Scientific Articles, Reports & Theses
List of Publications
Select tag “Algoryx” for publications affiliated with Algoryx, or “External” for external publications that use or cite Algoryx software.
2021 |
|
 | Aoshima, Koji; Servin, Martin; Wadbro, Eddie: Simulation-Based Optimization of High-Performance Wheel Loading. arXiv:2107.14615 , 2021. (Type: Miscellaneous | Abstract | Links | BibTeX | Tags: Algoryx, External) @misc{Aoshima2021, title = {Simulation-Based Optimization of High-Performance Wheel Loading}, author = {Koji Aoshima and Martin Servin and Eddie Wadbro}, url = {https://arxiv.org/abs/2107.14615 http://umit.cs.umu.se/hp_loading/}, year = {2021}, date = {2021-08-02}, organization = {Umeå University}, abstract = {Having smart and autonomous earthmoving in mind, we explore high-performance wheel loading in a simulated environment. This paper introduces a wheel loader simulator that combines contacting 3D multibody dynamics with a hybrid continuum-particle terrain model, supporting realistic digging forces and soil displacements at real-time performance. A total of 270,000 simulations are run with different loading actions, pile slopes, and soil to analyze how they affect the loading performance. The results suggest that the preferred digging actions should preserve and exploit a steep pile slope. High digging speed favors high productivity, while energy-efficient loading requires a lower dig speed.}, howpublished = {arXiv:2107.14615 }, keywords = {Algoryx, External}, pubstate = {published}, tppubtype = {misc} } Having smart and autonomous earthmoving in mind, we explore high-performance wheel loading in a simulated environment. This paper introduces a wheel loader simulator that combines contacting 3D multibody dynamics with a hybrid continuum-particle terrain model, supporting realistic digging forces and soil displacements at real-time performance. A total of 270,000 simulations are run with different loading actions, pile slopes, and soil to analyze how they affect the loading performance. The results suggest that the preferred digging actions should preserve and exploit a steep pile slope. High digging speed favors high productivity, while energy-efficient loading requires a lower dig speed. |
 | Shima, Daichi; Furukawa, Tomoyuki; Aoba, Ryuma; Ohashi, Ayato; Tsuruno, Kota; Naruse, Keitaro: Team Activity of Robot Competition of Simulated Robot in World Robot Summit 2020. SHS Web of Conferences, pp. 04016, EDP Sciences 2021, ISSN: 2261-2424. (Type: Inproceedings | Abstract | Links | BibTeX | Tags: External) @inproceedings{shima2021team, title = {Team Activity of Robot Competition of Simulated Robot in World Robot Summit 2020}, author = {Daichi Shima and Tomoyuki Furukawa and Ryuma Aoba and Ayato Ohashi and Kota Tsuruno and Keitaro Naruse}, url = {https://www.shs-conferences.org/articles/shsconf/abs/2021/13/shsconf_etltc2021_04016/shsconf_etltc2021_04016.html https://www.shs-conferences.org/articles/shsconf/pdf/2021/13/shsconf_etltc2021_04016.pdf }, issn = {2261-2424}, year = {2021}, date = {2021-05-08}, booktitle = {SHS Web of Conferences}, volume = {102}, pages = {04016}, organization = {EDP Sciences}, abstract = {World Robot Summit (WRS) has several robot competitions, and we will participate it in the infrastructure and disaster response category. Participating teams develop their robot system by teleoperation and/or autonomous operation and run it in a set of courses modelling and simplifying disaster responding situations. The authors will attend the challenge of the tunnel disaster response and recovery, in which we are requested to achieve an investigation and rescue scenario of a tunnel fire with simulated robots. As preparation, we develop simulated robot models and corresponding software as a team. In this article, we report out activity to the robot competition and student’s project-based learning by joining it.}, keywords = {External}, pubstate = {published}, tppubtype = {inproceedings} } World Robot Summit (WRS) has several robot competitions, and we will participate it in the infrastructure and disaster response category. Participating teams develop their robot system by teleoperation and/or autonomous operation and run it in a set of courses modelling and simplifying disaster responding situations. The authors will attend the challenge of the tunnel disaster response and recovery, in which we are requested to achieve an investigation and rescue scenario of a tunnel fire with simulated robots. As preparation, we develop simulated robot models and corresponding software as a team. In this article, we report out activity to the robot competition and student’s project-based learning by joining it. |
 | Selby, Nicholas S; Asada, Harry H: Learning of Causal Observable Functions for Koopman-DFL Lifting Linearization of Nonlinear Controlled Systems and Its Application to Excavation Automation. arXiv preprint arXiv:2104.02004, 2021. (Type: Journal Article | Abstract | Links | BibTeX | Tags: External) @article{selby2021learning, title = {Learning of Causal Observable Functions for Koopman-DFL Lifting Linearization of Nonlinear Controlled Systems and Its Application to Excavation Automation}, author = {Nicholas S Selby and Harry H Asada}, url = {https://arxiv.org/abs/2104.02004 https://arxiv.org/pdf/2104.02004 }, year = {2021}, date = {2021-01-01}, journal = {arXiv preprint arXiv:2104.02004}, abstract = {Effective and causal observable functions for low-order lifting linearization of nonlinear controlled systems are learned from data by using neural networks. While Koopman operator theory allows us to represent a nonlinear system as a linear system in an infinite-dimensional space of observables, exact linearization is guaranteed only for autonomous systems with no input, and finding effective observable functions for approximation with a low-order linear system remains an open question. Dual Faceted Linearization uses a set of effective observables for low-order lifting linearization, but the method requires knowledge of the physical structure of the nonlinear system. Here, a data-driven method is presented for generating a set of nonlinear observable functions that can accurately approximate a nonlinear control system to a low-order linear control system. A caveat in using data of measured variables as observables is that the measured variables may contain input to the system, which incurs a causality contradiction when lifting the system, i.e. taking derivatives of the observables. The current work presents a method for eliminating such anti-causal components of the observables and lifting the system using only causal observables. The method is applied to excavation automation, a complex nonlinear dynamical system, to obtain a low-order lifted linear model for control design.}, keywords = {External}, pubstate = {published}, tppubtype = {article} } Effective and causal observable functions for low-order lifting linearization of nonlinear controlled systems are learned from data by using neural networks. While Koopman operator theory allows us to represent a nonlinear system as a linear system in an infinite-dimensional space of observables, exact linearization is guaranteed only for autonomous systems with no input, and finding effective observable functions for approximation with a low-order linear system remains an open question. Dual Faceted Linearization uses a set of effective observables for low-order lifting linearization, but the method requires knowledge of the physical structure of the nonlinear system. Here, a data-driven method is presented for generating a set of nonlinear observable functions that can accurately approximate a nonlinear control system to a low-order linear control system. A caveat in using data of measured variables as observables is that the measured variables may contain input to the system, which incurs a causality contradiction when lifting the system, i.e. taking derivatives of the observables. The current work presents a method for eliminating such anti-causal components of the observables and lifting the system using only causal observables. The method is applied to excavation automation, a complex nonlinear dynamical system, to obtain a low-order lifted linear model for control design. |
 | Styrud, Jonathan; Iovino, Matteo; Norrlöf, Mikael; Björkman, Mårten; Smith, Christian: Combining Planning and Learning of Behavior Trees for Robotic Assembly. arXiv preprint arXiv:2103.09036, 2021. (Type: Journal Article | Abstract | Links | BibTeX | Tags: External) @article{styrud2021combining, title = {Combining Planning and Learning of Behavior Trees for Robotic Assembly}, author = {Jonathan Styrud and Matteo Iovino and Mikael Norrlöf and Mårten Björkman and Christian Smith}, url = {https://arxiv.org/abs/2103.09036 https://arxiv.org/pdf/2103.09036 https://github.com/jstyrud/planning-and-learning }, year = {2021}, date = {2021-01-01}, journal = {arXiv preprint arXiv:2103.09036}, abstract = {Industrial robots can solve very complex tasks in controlled environments, but modern applications require robots able to operate in unpredictable surroundings as well. An increasingly popular reactive policy architecture in robotics is Behavior Trees but as with other architectures, programming time still drives cost and limits flexibility. There are two main branches of algorithms to generate policies automatically, automated planning and machine learning, both with their own drawbacks. We propose a method for generating Behavior Trees using a Genetic Programming algorithm and combining the two branches by taking the result of an automated planner and inserting it into the population. Experimental results confirm that the proposed method of combining planning and learning performs well on a variety of robotic assembly problems and outperforms both of the base methods used separately. We also show that this type of high level learning of Behavior Trees can be transferred to a real system without further training.}, keywords = {External}, pubstate = {published}, tppubtype = {article} } Industrial robots can solve very complex tasks in controlled environments, but modern applications require robots able to operate in unpredictable surroundings as well. An increasingly popular reactive policy architecture in robotics is Behavior Trees but as with other architectures, programming time still drives cost and limits flexibility. There are two main branches of algorithms to generate policies automatically, automated planning and machine learning, both with their own drawbacks. We propose a method for generating Behavior Trees using a Genetic Programming algorithm and combining the two branches by taking the result of an automated planner and inserting it into the population. Experimental results confirm that the proposed method of combining planning and learning performs well on a variety of robotic assembly problems and outperforms both of the base methods used separately. We also show that this type of high level learning of Behavior Trees can be transferred to a real system without further training. |
 | Gieselmann, Robert; Pokorny, Florian T: Planning-Augmented Hierarchical Reinforcement Learning. IEEE Robotics and Automation Letters, 6 (3), pp. 5097-5104, 2021. (Type: Journal Article | Abstract | Links | BibTeX | Tags: External) @article{Gieselmann2021, title = {Planning-Augmented Hierarchical Reinforcement Learning}, author = {Robert Gieselmann and Florian T Pokorny}, doi = {10.1109/LRA.2021.3071062}, year = {2021}, date = {2021-01-01}, journal = {IEEE Robotics and Automation Letters}, volume = {6}, number = {3}, pages = {5097-5104}, abstract = {Abstract—Planning algorithms are powerful at solving longhorizon decision-making problems but require that environment dynamics are known. Model-free reinforcement learning has recently been merged with graph-based planning to increase the robustness of trained policies in state-space navigation problems. Recent ideas suggest to use planning in order to provide intermediate waypoints guiding the policy in long-horizon tasks. Yet, it is not always practical to describe a problem in the setting of state-to-state navigation. Often, the goal is defined by one or multiple disjoint sets of valid states or implicitly using an abstract task description. Building upon previous efforts, we introduce a novel algorithm called Planning-Augmented Hierarchical Reinforcement Learning (PAHRL) which translates the concept of hybrid planning/RL to such problems with implicitly defined goal. Using a hierarchical framework, we divide the original task, formulated as a Markov Decision Process (MDP), into a hierarchy of shorter horizon MDPs. Actor-critic agents are trained in parallel for each level of the hierarchy. During testing, a planner then determines useful subgoals on a state graph constructed at the bottom level of the hierarchy. The effectiveness of our approach is demonstrated for a set of continuous control problems in simulation including robot arm reaching tasks and the manipulation of a deformable object.}, keywords = {External}, pubstate = {published}, tppubtype = {article} } Abstract—Planning algorithms are powerful at solving longhorizon decision-making problems but require that environment dynamics are known. Model-free reinforcement learning has recently been merged with graph-based planning to increase the robustness of trained policies in state-space navigation problems. Recent ideas suggest to use planning in order to provide intermediate waypoints guiding the policy in long-horizon tasks. Yet, it is not always practical to describe a problem in the setting of state-to-state navigation. Often, the goal is defined by one or multiple disjoint sets of valid states or implicitly using an abstract task description. Building upon previous efforts, we introduce a novel algorithm called Planning-Augmented Hierarchical Reinforcement Learning (PAHRL) which translates the concept of hybrid planning/RL to such problems with implicitly defined goal. Using a hierarchical framework, we divide the original task, formulated as a Markov Decision Process (MDP), into a hierarchy of shorter horizon MDPs. Actor-critic agents are trained in parallel for each level of the hierarchy. During testing, a planner then determines useful subgoals on a state graph constructed at the bottom level of the hierarchy. The effectiveness of our approach is demonstrated for a set of continuous control problems in simulation including robot arm reaching tasks and the manipulation of a deformable object. |
2020 |
|
| Li, Guoyuan; Waldum, Håkon Bjerkgaard; Grindvik, Marcus Olai; Jørundl, Ruben Svedal; Zhang, Houxiang: Development of a vision-based target exploration system for snake-like robots in structured environments. International Journal of Advanced Robotic Systems, pp. 1-11, 2020. (Type: Journal Article | Abstract | Links | BibTeX | Tags: External) @article{Li2020, title = {Development of a vision-based target exploration system for snake-like robots in structured environments}, author = {Guoyuan Li and Håkon Bjerkgaard Waldum and Marcus Olai Grindvik and Ruben Svedal Jørundl and Houxiang Zhang}, url = {https://journals.sagepub.com/doi/full/10.1177/1729881420936141 https://www.researchgate.net/publication/342710008_Development_of_a_vision-based_target_exploration_system_for_snake-like_robots_in_structured_environments}, doi = {10.1177/1729881420936141}, year = {2020}, date = {2020-07-06}, journal = {International Journal of Advanced Robotic Systems}, pages = {1-11}, abstract = {Applying snake-like robots to environmental exploration has been a hot topic for years. How to achieve free navigation for target search in a complex environment in a safe and efficient manner is one of the main tasks that researchers in the field of robotics currently face. This article presents a target exploration system that takes advantages of visual sensing to navigate the snake-like robot in structured environments. Two cameras are utilized in the system. The first one is mounted on the head of the snake-like robot for target recognition and the other is an overhead camera which is responsible for locating the robot and identifying surrounding obstacles. All dead ends in the environment can thus be recognized using a template-based method. A search strategy for traversal of the dead ends is employed for generating exploration paths. Several gaits are developed for the snake-like robot. By switching between these gaits, the snake-like robot is able to follow the paths to search for the target. Two experiments are conducted in a maze environment. The experimental results validate the effectiveness of the proposed system for snake-like robots exploring in structured environments.}, keywords = {External}, pubstate = {published}, tppubtype = {article} } Applying snake-like robots to environmental exploration has been a hot topic for years. How to achieve free navigation for target search in a complex environment in a safe and efficient manner is one of the main tasks that researchers in the field of robotics currently face. This article presents a target exploration system that takes advantages of visual sensing to navigate the snake-like robot in structured environments. Two cameras are utilized in the system. The first one is mounted on the head of the snake-like robot for target recognition and the other is an overhead camera which is responsible for locating the robot and identifying surrounding obstacles. All dead ends in the environment can thus be recognized using a template-based method. A search strategy for traversal of the dead ends is employed for generating exploration paths. Several gaits are developed for the snake-like robot. By switching between these gaits, the snake-like robot is able to follow the paths to search for the target. Two experiments are conducted in a maze environment. The experimental results validate the effectiveness of the proposed system for snake-like robots exploring in structured environments. | |
 | Major, Pierre; Zhang, Houxiang; Hildre, Hans Petter; Edet, Mathieu: Virtual prototyping of offshore operations: a review. Ship Technology Research, pp. 1–18, 2020. (Type: Journal Article | Abstract | Links | BibTeX | Tags: External) @article{major2020virtual, title = {Virtual prototyping of offshore operations: a review}, author = {Pierre Major and Houxiang Zhang and Hans Petter Hildre and Mathieu Edet}, doi = {10.1080/09377255.2020.1831840}, year = {2020}, date = {2020-01-01}, journal = {Ship Technology Research}, pages = {1--18}, publisher = {Taylor & Francis}, abstract = {Virtual prototyping of offshore operations (VPOO) is performed to plan and validate planning of infrequent or demanding operations characterized by high risk and low margins of error in hostile and remote environments distant from emergency response bases that require expensive equipment. Key elements of VPOO is the rapidity of virtual prototyping and the human-centric approach necessitating high quality visuals and real-time time-domain simulation. This survey reviews publications, commercial software and simulators, and regulations on offshore operations. Findings indicate that the VPOO is not common in the industry, offshore operation regulations lag behind the state of the art in industry in terms of mission planning, and this field has been subject to scarce commercial and scientific scrutiny so far. A discussion of future developments and trends concludes the paper.}, keywords = {External}, pubstate = {published}, tppubtype = {article} } Virtual prototyping of offshore operations (VPOO) is performed to plan and validate planning of infrequent or demanding operations characterized by high risk and low margins of error in hostile and remote environments distant from emergency response bases that require expensive equipment. Key elements of VPOO is the rapidity of virtual prototyping and the human-centric approach necessitating high quality visuals and real-time time-domain simulation. This survey reviews publications, commercial software and simulators, and regulations on offshore operations. Findings indicate that the VPOO is not common in the industry, offshore operation regulations lag behind the state of the art in industry in terms of mission planning, and this field has been subject to scarce commercial and scientific scrutiny so far. A discussion of future developments and trends concludes the paper. |
 | Yang, Yajue; Pan, Jia; Long, Pinxin; Song, Xibin; Zhang, Liangjun: Time Variable Minimum Torque Trajectory Optimization for Autonomous Excavator. arXiv preprint arXiv:2006.00811, 2020. (Type: Journal Article | Abstract | Links | BibTeX | Tags: External) @article{yang2020time, title = {Time Variable Minimum Torque Trajectory Optimization for Autonomous Excavator}, author = {Yajue Yang and Jia Pan and Pinxin Long and Xibin Song and Liangjun Zhang}, url = {https://arxiv.org/abs/2006.00811 https://arxiv.org/pdf/2006.00811}, year = {2020}, date = {2020-01-01}, journal = {arXiv preprint arXiv:2006.00811}, abstract = {In this paper, we present a minimal torque and time variable trajectory optimization method for autonomous excavator considering the soil-tool interaction. The method formulates the excavation motion generation as a trajectory optimization problem and takes into account geometric, kinematic and dynamics constraints. To generate time-efficient trajectory and improve the overall optimization efficiency, we propose a time variable trajectory optimization mechanism so that the time intervals between the keypoints along the trajectory subject to the optimization. As a result, the method uses few keypoints and reduces the total number of optimization variables. We further introduce a soil-tool interaction force model, which considers the geometric shape of the bucket and the physical properties of the soil. The experimental result on a high fidelity dynamic simulator shows our method can generate feasible trajectories, which satisfy excavation task constraints and are adaptive to different soil conditions.}, keywords = {External}, pubstate = {published}, tppubtype = {article} } In this paper, we present a minimal torque and time variable trajectory optimization method for autonomous excavator considering the soil-tool interaction. The method formulates the excavation motion generation as a trajectory optimization problem and takes into account geometric, kinematic and dynamics constraints. To generate time-efficient trajectory and improve the overall optimization efficiency, we propose a time variable trajectory optimization mechanism so that the time intervals between the keypoints along the trajectory subject to the optimization. As a result, the method uses few keypoints and reduces the total number of optimization variables. We further introduce a soil-tool interaction force model, which considers the geometric shape of the bucket and the physical properties of the soil. The experimental result on a high fidelity dynamic simulator shows our method can generate feasible trajectories, which satisfy excavation task constraints and are adaptive to different soil conditions. |
 | Maruyama, T; Ogawa, S; Noda, K; Edaya, M; Jaklin, N; Tolsma, S; Takeda, N: Structural displacement compensation of a gigantic manipulator via deep learning. 2020 IEEE/SICE International Symposium on System Integration (SII), pp. 219–224, IEEE 2020. (Type: Inproceedings | Abstract | Links | BibTeX | Tags: External) @inproceedings{maruyama2020structural, title = {Structural displacement compensation of a gigantic manipulator via deep learning}, author = {T Maruyama and S Ogawa and K Noda and M Edaya and N Jaklin and S Tolsma and N Takeda}, doi = {10.1109/SII46433.2020.9026263}, year = {2020}, date = {2020-01-01}, booktitle = {2020 IEEE/SICE International Symposium on System Integration (SII)}, pages = {219--224}, organization = {IEEE}, abstract = {Structures of robotic systems that handle extremely heavy loads undergo static displacement. The ITER blanket remote handling system, which handles 4-ton objects, has displacements of up to 100 mm at the end effector. We propose a novel method that combines deep learning with a physics-based virtual reality system to compensate for displacement. Our deep learning model was trained by using data obtained from both the virtual reality system and physical measurement data of end effector positions. By using a prototype of the ITER blanket remote handling system, we experimentally show that our method successfully reduces the displacement at the end effector to a maximum error of 5.7 mm and a median error of 1.2 mm. We conclude that our approach provides an effective contribution to ensuring the feasibility and safety of the remote maintenance procedures that are to be performed within the ITER project.}, keywords = {External}, pubstate = {published}, tppubtype = {inproceedings} } Structures of robotic systems that handle extremely heavy loads undergo static displacement. The ITER blanket remote handling system, which handles 4-ton objects, has displacements of up to 100 mm at the end effector. We propose a novel method that combines deep learning with a physics-based virtual reality system to compensate for displacement. Our deep learning model was trained by using data obtained from both the virtual reality system and physical measurement data of end effector positions. By using a prototype of the ITER blanket remote handling system, we experimentally show that our method successfully reduces the displacement at the end effector to a maximum error of 5.7 mm and a median error of 1.2 mm. We conclude that our approach provides an effective contribution to ensuring the feasibility and safety of the remote maintenance procedures that are to be performed within the ITER project. |
 | Yuan, Shuai; Major, Pierre; Zhang, Houxiang: Flexible riser replacement operation based on advanced virtual prototyping. Ocean Engineering, 210 , pp. 107502, 2020. (Type: Journal Article | Abstract | Links | BibTeX | Tags: External) @article{yuan2020flexible, title = {Flexible riser replacement operation based on advanced virtual prototyping}, author = {Shuai Yuan and Pierre Major and Houxiang Zhang}, doi = {10.1016/j.oceaneng.2020.107502}, year = {2020}, date = {2020-01-01}, journal = {Ocean Engineering}, volume = {210}, pages = {107502}, publisher = {Elsevier}, abstract = {As a critical campaign in the offshore oil and gas engineering, flexible riser replacements involve complex operations that need to be optimized and detailed to factor in trends in the industry. Since it allows engineers to interact with simulation tools in real time during the operation design phase, virtual prototyping (VP) is an efficient method to obtain an optimal solution and improve operational procedures in terms of safety and effectiveness for risk-based integrity management of flexible risers. In this study, a real-time VP model is adopted to simulate the process of a water injection flexible riser pulled in from an installation vessel to a jacket platform, which is one of the riser replacements tasks. The results are validated against results based on a finite element analysis. Attention is paid to the configuration, tension, and maximum bending curvature along the flexible riser during the operation. The innovative approach presented in this paper can provide guidance with respect to the operation limitations of a flexible pipe in practical engineering.}, keywords = {External}, pubstate = {published}, tppubtype = {article} } As a critical campaign in the offshore oil and gas engineering, flexible riser replacements involve complex operations that need to be optimized and detailed to factor in trends in the industry. Since it allows engineers to interact with simulation tools in real time during the operation design phase, virtual prototyping (VP) is an efficient method to obtain an optimal solution and improve operational procedures in terms of safety and effectiveness for risk-based integrity management of flexible risers. In this study, a real-time VP model is adopted to simulate the process of a water injection flexible riser pulled in from an installation vessel to a jacket platform, which is one of the riser replacements tasks. The results are validated against results based on a finite element analysis. Attention is paid to the configuration, tension, and maximum bending curvature along the flexible riser during the operation. The innovative approach presented in this paper can provide guidance with respect to the operation limitations of a flexible pipe in practical engineering. |
 | Suzuki, Kenta; Kawabata, Kuniaki: Development of a simulator for underwater reconnaissance tasks by utilizing remotely operated robots. 2020 IEEE/SICE International Symposium on System Integration (SII), pp. 1100–1106, IEEE 2020. (Type: Inproceedings | Abstract | Links | BibTeX | Tags: External) @inproceedings{suzuki2020development, title = {Development of a simulator for underwater reconnaissance tasks by utilizing remotely operated robots}, author = {Kenta Suzuki and Kuniaki Kawabata}, doi = {10.1109/SII46433.2020.9026281}, year = {2020}, date = {2020-01-01}, booktitle = {2020 IEEE/SICE International Symposium on System Integration (SII)}, pages = {1100--1106}, organization = {IEEE}, abstract = {This paper describes the development of a simulator for underwater reconnaissance tasks by utilizing remotely operated robots. The developed simulator replicates physical effect such as fluid dynamics, buoyancy and fluid resistance in the area assumed to be filled with water. The simulated thrusters generate propulsion force and torque. The simulator also provides camera view disturbance models for a blur, distortion and noise. In this paper, we discussed the requirements to realistically simulate underwater remote reconnaissance tasks and explain the implementation methodologies. By using the developed simulator, we also demonstrate a simulation of a remotely operated vehicle (ROV) that was utilized in Fukushima Daiichi Nuclear Power Station (FDNPS).}, keywords = {External}, pubstate = {published}, tppubtype = {inproceedings} } This paper describes the development of a simulator for underwater reconnaissance tasks by utilizing remotely operated robots. The developed simulator replicates physical effect such as fluid dynamics, buoyancy and fluid resistance in the area assumed to be filled with water. The simulated thrusters generate propulsion force and torque. The simulator also provides camera view disturbance models for a blur, distortion and noise. In this paper, we discussed the requirements to realistically simulate underwater remote reconnaissance tasks and explain the implementation methodologies. By using the developed simulator, we also demonstrate a simulation of a remotely operated vehicle (ROV) that was utilized in Fukushima Daiichi Nuclear Power Station (FDNPS). |
 | Borgström, Johan: Methodology for Real Time Simulations of Autonomous Utility Vehicles. 2020. (Type: Miscellaneous | Abstract | Links | BibTeX | Tags: External) @misc{borgstrom2020methodology, title = {Methodology for Real Time Simulations of Autonomous Utility Vehicles}, author = {Johan Borgström}, url = {http://ltu.diva-portal.org/smash/record.jsf?pid=diva2%3A1437952&dswid=-7032 http://ltu.diva-portal.org/smash/get/diva2:1437952/FULLTEXT02.pdf}, year = {2020}, date = {2020-01-01}, abstract = {This master thesis is a part of a research project where Luleå University of Technology (LTU) collaborates with University of Oulu, SINTEF Narvik and Oulu University of Applied Sciences. The goal with the research project is to develop a Nordic platform for development of autonomous, environmental friendly and energy efficient heavy vehicles in the forest, harbor and mining industry. The purpose with the master thesis is to assist LTU in their role in the research project. The Nordic platform was positioned in the product development process, with the result that it could be useful in the fourth phase ”Detail design” and in the fifth phase ”Testing and refinement” in the Ulrich and Eppinger product development process. A methodology has been developed, covering all necessary steps going from an assembly of a vehicle in an arbitrary CAD program to perform real time simulations (including HiL simulations) of the vehicle in Simulink. The off-road research platform for forest- and agriculture applications developed by LTU was used as a case study in the master thesis. Applying the methodology on this platform showed that choosing correct simulation frequency is important and that graphics enabled in real time simulations requires large computational power.}, keywords = {External}, pubstate = {published}, tppubtype = {misc} } This master thesis is a part of a research project where Luleå University of Technology (LTU) collaborates with University of Oulu, SINTEF Narvik and Oulu University of Applied Sciences. The goal with the research project is to develop a Nordic platform for development of autonomous, environmental friendly and energy efficient heavy vehicles in the forest, harbor and mining industry. The purpose with the master thesis is to assist LTU in their role in the research project. The Nordic platform was positioned in the product development process, with the result that it could be useful in the fourth phase ”Detail design” and in the fifth phase ”Testing and refinement” in the Ulrich and Eppinger product development process. A methodology has been developed, covering all necessary steps going from an assembly of a vehicle in an arbitrary CAD program to perform real time simulations (including HiL simulations) of the vehicle in Simulink. The off-road research platform for forest- and agriculture applications developed by LTU was used as a case study in the master thesis. Applying the methodology on this platform showed that choosing correct simulation frequency is important and that graphics enabled in real time simulations requires large computational power. |
 | Pereira, JG; Ellman, A: From CAD to Physics-Based Digital Twin: Framework for Real-Time Simulation of Virtual prototypes. Proceedings of the Design Society: DESIGN Conference, pp. 335–344, Cambridge University Press 2020. (Type: Inproceedings | Abstract | Links | BibTeX | Tags: External) @inproceedings{pereira2020cad, title = {From CAD to Physics-Based Digital Twin: Framework for Real-Time Simulation of Virtual prototypes}, author = {JG Pereira and A Ellman}, url = {https://www.cambridge.org/core/services/aop-cambridge-core/content/view/479604733E3644CA38B927FFCC09B519/S2633776220000473a.pdf/from-cad-to-physics-based-digital-twin-framework-for-real-time-simulation-of-virtual-prototypes.pdf}, doi = {doi:10.1017/dsd.2020.47}, year = {2020}, date = {2020-01-01}, booktitle = {Proceedings of the Design Society: DESIGN Conference}, volume = {1}, pages = {335--344}, organization = {Cambridge University Press}, abstract = {Engineering work is mostly done in 3D CAD software throughout the engineering process from conceptual design and layout of products. Physics-Based Virtual Prototypes are very valuable addition on Computer Aided Engineering enabling product development simulators, training simulators and digital twin concept in product lift-cycle process. In this work, we present a framework, how such virtual prototypes can be developed from 3D CAD models with meaningful effort.}, keywords = {External}, pubstate = {published}, tppubtype = {inproceedings} } Engineering work is mostly done in 3D CAD software throughout the engineering process from conceptual design and layout of products. Physics-Based Virtual Prototypes are very valuable addition on Computer Aided Engineering enabling product development simulators, training simulators and digital twin concept in product lift-cycle process. In this work, we present a framework, how such virtual prototypes can be developed from 3D CAD models with meaningful effort. |
 | Laezza, Rita; Karayiannidis, Yiannis: Shape Control of Elastoplastic Deformable Linear Objects through Reinforcement Learning. IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS)
Las Vegas (Virtual), USA, 2020-10-25 - 2020-10-29, 2020. (Type: Conference | Abstract | Links | BibTeX | Tags: External) @conference{laezzashape2020, title = {Shape Control of Elastoplastic Deformable Linear Objects through Reinforcement Learning}, author = {Rita Laezza and Yiannis Karayiannidis}, url = {https://ras.papercept.net/proceedings/IROS20/3496.pdf}, year = {2020}, date = {2020-01-01}, booktitle = {IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS) Las Vegas (Virtual), USA, 2020-10-25 - 2020-10-29}, abstract = {Deformable object manipulation tasks have longbeen regarded as challenging robotic problems. However, untilrecently, very little work had been done on the subject, withmost robotic manipulation methods being developed for rigidobjects. As machine learning methods are becoming morepowerful, there are new model-free strategies to explore forthese objects, which are notoriously hard to model. This paperfocuses on shape control problems for Deformable Linear Objects (DLOs). Despite being one of the most researched classesof DLOs in terms of geometry, no other paper has focusedon materials with elastoplastic properties. Therefore, a novelshape control task, requiring permanent plastic deformationis implemented in a simulation environment. ReinforcementLearning methods are used to learn a continuous controlpolicy. To that end, a discrete curvature measure is usedas a low-dimensional state representation and as part of anintuitive reward function. Finally, three state-of-the-art actor-critic algorithms are compared on the proposed environmentand successfully achieve the goal shape.}, keywords = {External}, pubstate = {published}, tppubtype = {conference} } Deformable object manipulation tasks have longbeen regarded as challenging robotic problems. However, untilrecently, very little work had been done on the subject, withmost robotic manipulation methods being developed for rigidobjects. As machine learning methods are becoming morepowerful, there are new model-free strategies to explore forthese objects, which are notoriously hard to model. This paperfocuses on shape control problems for Deformable Linear Objects (DLOs). Despite being one of the most researched classesof DLOs in terms of geometry, no other paper has focusedon materials with elastoplastic properties. Therefore, a novelshape control task, requiring permanent plastic deformationis implemented in a simulation environment. ReinforcementLearning methods are used to learn a continuous controlpolicy. To that end, a discrete curvature measure is usedas a low-dimensional state representation and as part of anintuitive reward function. Finally, three state-of-the-art actor-critic algorithms are compared on the proposed environmentand successfully achieve the goal shape. |
2019 |
|
 | Major, Pierre; Skulstad, Robert; Li, Guoyuan; Zhang, Houxiang: Virtual prototyping: a case study of positioning systems for drilling operations in the Barents Sea. Ships and Offshore Structures, 14 (sup1), pp. 364–373, 2019. (Type: Journal Article | Abstract | Links | BibTeX | Tags: External) @article{major2019virtual, title = {Virtual prototyping: a case study of positioning systems for drilling operations in the Barents Sea}, author = {Pierre Major and Robert Skulstad and Guoyuan Li and Houxiang Zhang}, doi = {10.1080/17445302.2019.1601322}, year = {2019}, date = {2019-01-01}, journal = {Ships and Offshore Structures}, volume = {14}, number = {sup1}, pages = {364--373}, publisher = {Taylor & Francis}, abstract = {This study proposes a framework for comparative study on three different positioning solutions for mobile offshore drilling units (MODUs) using high modulus polyethylene (HMPE) ropes, including active mooring with an HMPE rope, conventional dynamic positioning (DP) and active hybrid position-keeping (AHP-K). The goal of the positioning systems is to keep the MODU above the wellhead with acceptable riser-angle loading, minimal energy consumption, reduced underwater noise generation, and harmful emissions. This is the first time a holistic study has been performed on positioning that factors in the financial and environmental costs. The time domain simulation, which includes sea-state, wind, and current profiles, is performed with a well-developed software architecture and control algorithms for MODU position-keeping. The case study addresses a MODU drilling in the Barents Sea. Simulation results show that AHP-K is more efficient compared to the other two positioning solutions for drilling operations in the studied environment.}, keywords = {External}, pubstate = {published}, tppubtype = {article} } This study proposes a framework for comparative study on three different positioning solutions for mobile offshore drilling units (MODUs) using high modulus polyethylene (HMPE) ropes, including active mooring with an HMPE rope, conventional dynamic positioning (DP) and active hybrid position-keeping (AHP-K). The goal of the positioning systems is to keep the MODU above the wellhead with acceptable riser-angle loading, minimal energy consumption, reduced underwater noise generation, and harmful emissions. This is the first time a holistic study has been performed on positioning that factors in the financial and environmental costs. The time domain simulation, which includes sea-state, wind, and current profiles, is performed with a well-developed software architecture and control algorithms for MODU position-keeping. The case study addresses a MODU drilling in the Barents Sea. Simulation results show that AHP-K is more efficient compared to the other two positioning solutions for drilling operations in the studied environment. |
 | Suzuki, Kenta; Kawabata, Kuniaki: Development of a multi-copter simulator and a projection system for virtual operation experience. 2019 IEEE/SICE International Symposium on System Integration (SII), pp. 1–6, IEEE 2019. (Type: Inproceedings | Abstract | Links | BibTeX | Tags: External) @inproceedings{suzuki2019development, title = {Development of a multi-copter simulator and a projection system for virtual operation experience}, author = {Kenta Suzuki and Kuniaki Kawabata}, doi = {10.1109/SII.2019.8700412}, year = {2019}, date = {2019-01-01}, booktitle = {2019 IEEE/SICE International Symposium on System Integration (SII)}, pages = {1--6}, organization = {IEEE}, abstract = {Our motivation is to utilize simulation technology to accelerate the decommissioning of Fukushima Daiichi Nuclear Power Station (FDNPS) by remote operated robots. We already developed several simulation functions in our previous work. Recently multi-copter was utilized for reconnaissance tasks at FDNPS. This paper described to design a simulation function for multi-copter operation training. Fluid dynamics affected to flying body are simulated by implemented function. We also attempt the demonstration of immersive operation environment based on a 3D projection system that provides virtual operation experience.}, keywords = {External}, pubstate = {published}, tppubtype = {inproceedings} } Our motivation is to utilize simulation technology to accelerate the decommissioning of Fukushima Daiichi Nuclear Power Station (FDNPS) by remote operated robots. We already developed several simulation functions in our previous work. Recently multi-copter was utilized for reconnaissance tasks at FDNPS. This paper described to design a simulation function for multi-copter operation training. Fluid dynamics affected to flying body are simulated by implemented function. We also attempt the demonstration of immersive operation environment based on a 3D projection system that provides virtual operation experience. |
 | Wang, Lin; Kim, Hyuncheol; Kim, Imgyu; Han, Soonhung: A visual simulation of ocean floating wind power system. Computer Animation and Virtual Worlds, 30 (2), pp. e1859, 2019. (Type: Journal Article | Abstract | Links | BibTeX | Tags: External) @article{wang2019visual, title = {A visual simulation of ocean floating wind power system}, author = {Lin Wang and Hyuncheol Kim and Imgyu Kim and Soonhung Han}, doi = {10.1002/cav.1859}, year = {2019}, date = {2019-01-01}, journal = {Computer Animation and Virtual Worlds}, volume = {30}, number = {2}, pages = {e1859}, publisher = {Wiley Online Library}, abstract = {The development of ocean floating wind power has been burgeoning in recent years because of its low cost and high efficiency. To facilitate effectiveness, 3D visualization using virtual reality and augmented reality technologies has been applied to many operating systems. However, most of the existing 3D motion visualizations are “pseudo” visualization, and there are a few realistic visualization systems that base the motion of ocean floating wind power on simulation and experiment results. Therefore, in this paper, we conducted research related to the design for a realistic motion visualization system based on numerical simulation data using a commercial game engine (Unity 3D). In our system, the six‐degree‐of‐freedom motion (Surge, Sway, Heave, Roll, Pitch, and Yaw) is simulated and visualized based on numerical analysis results of two hydrodynamics simulation softwares, which can illuminate the nuance between simulation results and experiment results and give us a “real‐time” visual experience about motion in each direction. Meanwhile, comprehensive sea environment conditions, such as wind, rain, water, sound, and cloudiness, are also visualized in Unity 3D.}, keywords = {External}, pubstate = {published}, tppubtype = {article} } The development of ocean floating wind power has been burgeoning in recent years because of its low cost and high efficiency. To facilitate effectiveness, 3D visualization using virtual reality and augmented reality technologies has been applied to many operating systems. However, most of the existing 3D motion visualizations are “pseudo” visualization, and there are a few realistic visualization systems that base the motion of ocean floating wind power on simulation and experiment results. Therefore, in this paper, we conducted research related to the design for a realistic motion visualization system based on numerical simulation data using a commercial game engine (Unity 3D). In our system, the six‐degree‐of‐freedom motion (Surge, Sway, Heave, Roll, Pitch, and Yaw) is simulated and visualized based on numerical analysis results of two hydrodynamics simulation softwares, which can illuminate the nuance between simulation results and experiment results and give us a “real‐time” visual experience about motion in each direction. Meanwhile, comprehensive sea environment conditions, such as wind, rain, water, sound, and cloudiness, are also visualized in Unity 3D. |
 | Kanehiro, Fumio; Nakaoka, Shin’ichiro; Sugihara, Tomomichi; Wakisaka, Naoki; Ishigami, Genya; Ozaki, Shingo; Tadokoro, Satoshi: Simulator for disaster response robotics. S., Tadokoro (Ed.): Disaster Robotics, 128 , pp. 453–477, Springer, 2019. (Type: Incollection | Abstract | Links | BibTeX | Tags: External) @incollection{kanehiro2019simulator, title = {Simulator for disaster response robotics}, author = {Fumio Kanehiro and Shin’ichiro Nakaoka and Tomomichi Sugihara and Naoki Wakisaka and Genya Ishigami and Shingo Ozaki and Satoshi Tadokoro}, editor = {Tadokoro S. }, doi = {10.1007/978-3-030-05321-5_9}, year = {2019}, date = {2019-01-01}, booktitle = {Disaster Robotics}, volume = {128}, pages = {453--477}, publisher = {Springer}, series = {Springer Tracts in Advanced Robotics}, abstract = {This chapter presents a simulator for disaster response robots based on the Choreonoid framework. Two physics engines and a graphics engine were developed and integrated into the framework. One physics engine enables robust contact-force computation among rigid bodies based on volumetric intersection and a relaxed constraint, whereas the other enables accurate and computationally efficient computation of machine–terrain interaction mechanics based on macro and microscopic approaches. The graphics engine allows simulating natural phenomena, such as rain, fire, and smoke, based on a particle system to resemble tough scenarios at disaster sites. In addition, wide-angle vision sensors, such as omnidirectional cameras and LIDAR sensors, can be simulated using multiple rendering screens. Overall, the simulator provides a tool for the efficient and safe development of disaster response robots.}, keywords = {External}, pubstate = {published}, tppubtype = {incollection} } This chapter presents a simulator for disaster response robots based on the Choreonoid framework. Two physics engines and a graphics engine were developed and integrated into the framework. One physics engine enables robust contact-force computation among rigid bodies based on volumetric intersection and a relaxed constraint, whereas the other enables accurate and computationally efficient computation of machine–terrain interaction mechanics based on macro and microscopic approaches. The graphics engine allows simulating natural phenomena, such as rain, fire, and smoke, based on a particle system to resemble tough scenarios at disaster sites. In addition, wide-angle vision sensors, such as omnidirectional cameras and LIDAR sensors, can be simulated using multiple rendering screens. Overall, the simulator provides a tool for the efficient and safe development of disaster response robots. |
 | João, Pereira Jr: Development of a Harvester Machine Simulator in Virtual Reality. Faculty of Engineering and Natural Sciences, Tampere University, 2019. (Type: Masters Thesis | Abstract | Links | BibTeX | Tags: External) @mastersthesis{pereira2019development, title = {Development of a Harvester Machine Simulator in Virtual Reality}, author = {Pereira Jr João}, url = {https://trepo.tuni.fi/bitstream/handle/10024/115646/Pereira.pdf?sequence=2}, year = {2019}, date = {2019-01-01}, school = {Faculty of Engineering and Natural Sciences, Tampere University}, abstract = {Computer-aided design (CAD) software is used in the product design and development to design complex and detailed prototypes. It provides good assistance and solid data generation to designers and engineers. In order to remain competitive, industry is always seeking for higher process efficiency and product quality enhancement in the shortest period of time. Continuous research keeps going to make it possible. Virtual reality has been one of the research focus in the recent years. It is studied and applied to be used as an assistant tool in the product lifecyle management, particularly in facilitating the development phase. However, the implementation process from CAD to virtual reality remains a challenge due to time consumption and technology complexibility. In this work a real-time virtual reality harvester simulator was developed. The start point was a 3D harvester CAD model. It was used the CAD simulator AGX Momentum, a game engine Unity and the physics engine AGX Dynamics to create dynamics simulation, to design a virtual forest environment and to enable physical controllers interact with the model. With the capabilities of AGX Momentum, it was added dynamics motion directly in the CAD software, creating fast CAD simulations. A virtual scene was designed with Unity to simulate an environment and the immersion of the user on it with Oculus Rift device. The harvester model was imported to the Unity scene with AGX Dynamics. In the end it was obtained a real size virtual prototype, with the possibility of interacting and control it using physical controllers. The user can visualise the scene in real-time through a head mounted display, providing him the experience of a real machine operator. Driving the harvester in a simulated forest, allowed to test the model in a hypothetical real scenario. The process of implementing the CAD model in virtual reality used in this work, revealed to be efficient and intuitive. However, because it is a complex and large model, it was necessary to remove certain bodies (without dynamics effect) and reduce the number of contact points between components in order to balance the speed and performance of the simulator. Following the same method used in this work, Other CAD models can be imported to virtual reality and be dynamically simulated.}, keywords = {External}, pubstate = {published}, tppubtype = {mastersthesis} } Computer-aided design (CAD) software is used in the product design and development to design complex and detailed prototypes. It provides good assistance and solid data generation to designers and engineers. In order to remain competitive, industry is always seeking for higher process efficiency and product quality enhancement in the shortest period of time. Continuous research keeps going to make it possible. Virtual reality has been one of the research focus in the recent years. It is studied and applied to be used as an assistant tool in the product lifecyle management, particularly in facilitating the development phase. However, the implementation process from CAD to virtual reality remains a challenge due to time consumption and technology complexibility. In this work a real-time virtual reality harvester simulator was developed. The start point was a 3D harvester CAD model. It was used the CAD simulator AGX Momentum, a game engine Unity and the physics engine AGX Dynamics to create dynamics simulation, to design a virtual forest environment and to enable physical controllers interact with the model. With the capabilities of AGX Momentum, it was added dynamics motion directly in the CAD software, creating fast CAD simulations. A virtual scene was designed with Unity to simulate an environment and the immersion of the user on it with Oculus Rift device. The harvester model was imported to the Unity scene with AGX Dynamics. In the end it was obtained a real size virtual prototype, with the possibility of interacting and control it using physical controllers. The user can visualise the scene in real-time through a head mounted display, providing him the experience of a real machine operator. Driving the harvester in a simulated forest, allowed to test the model in a hypothetical real scenario. The process of implementing the CAD model in virtual reality used in this work, revealed to be efficient and intuitive. However, because it is a complex and large model, it was necessary to remove certain bodies (without dynamics effect) and reduce the number of contact points between components in order to balance the speed and performance of the simulator. Following the same method used in this work, Other CAD models can be imported to virtual reality and be dynamically simulated. |
2018 |
|
 | Lenerand, Torstein Sundnes: Component-Based Simulator for Modelling the Design and Dynamics of Modular Robots. 2018. (Type: Masters Thesis | Abstract | Links | BibTeX | Tags: External) @mastersthesis{lenerand2018component, title = {Component-Based Simulator for Modelling the Design and Dynamics of Modular Robots}, author = {Torstein Sundnes Lenerand}, url = {http://hdl.handle.net/11250/2581432 https://ntnuopen.ntnu.no/ntnu-xmlui/bitstream/handle/11250/2581432/Lenerand%2c%20Torstein%20S.%202018.pdf?sequence=1&isAllowed=y}, year = {2018}, date = {2018-01-01}, abstract = {This project presents the design of a component-based simulator used for modelling the design and movement of chain-based modular robots. This work is in collaboration with NTNU Ålesund and implemented in the Unity® game engine with Algoryx® Dynamics for physics calculations. The focus is on Modular robots, along with techniques for simulator creation and software development such as Component-Based Software Engineering and Design. The Unified Process is used for prototyping and research, while the finished design is verified using tests, reviews, and use-case studies. This thesis discusses the impact of using Component-Based Design in a relatively small project, and the advantages/disadvantages of this decision. The goal is to provide the optimum tool for students to learn about, and researchers to develop, customized modular robots.}, keywords = {External}, pubstate = {published}, tppubtype = {mastersthesis} } This project presents the design of a component-based simulator used for modelling the design and movement of chain-based modular robots. This work is in collaboration with NTNU Ålesund and implemented in the Unity® game engine with Algoryx® Dynamics for physics calculations. The focus is on Modular robots, along with techniques for simulator creation and software development such as Component-Based Software Engineering and Design. The Unified Process is used for prototyping and research, while the finished design is verified using tests, reviews, and use-case studies. This thesis discusses the impact of using Component-Based Design in a relatively small project, and the advantages/disadvantages of this decision. The goal is to provide the optimum tool for students to learn about, and researchers to develop, customized modular robots. |
2017 |
|
 | Nakaoka, Shiníchiro; Cisneros, Rafael; Morisawa, Mitsuharu; Sakaguchi, Takeshi; Kaneko, Kenji; Kajita, Shuuji; Kanehiro, Fumio: Developing semi-autonomous humanoid robots that perform various composite tasks via a task sequencer and dynamics simulator. 2017 IEEE Workshop on Advanced Robotics and its Social Impacts (ARSO), pp. 1–8, IEEE 2017. (Type: Inproceedings | Abstract | Links | BibTeX | Tags: External) @inproceedings{nakaoka2017developing, title = {Developing semi-autonomous humanoid robots that perform various composite tasks via a task sequencer and dynamics simulator}, author = {Shiníchiro Nakaoka and Rafael Cisneros and Mitsuharu Morisawa and Takeshi Sakaguchi and Kenji Kaneko and Shuuji Kajita and Fumio Kanehiro}, doi = {10.1109/ARSO.2017.8025188}, year = {2017}, date = {2017-01-01}, booktitle = {2017 IEEE Workshop on Advanced Robotics and its Social Impacts (ARSO)}, pages = {1--8}, organization = {IEEE}, abstract = {This paper proposes a system to enable a humanoid robot to perform various tasks semi-autonomously according to higher-layer procedures called task sequences. A task sequence is a sequentially structured procedure that describes how to perform a particular task based on sensing data, motion planners, and a robot controller. These task sequences are processed by the task sequencer to move the robot. The goal of our system is to support comprehensive tasks, such as disaster response, with a number of task sequences defined for various subtasks. To efficiently develop required task sequences, the task sequencer is designed such that task sequences can be executed interactively; further, the task sequencer is integrated with a dynamics simulator that can be used to test the sequences without actually moving the robot. We verified our system by using it to make our HRP-2Kai robot perform the tasks defined in the DARPA Robotics Challenge, a competition involving disaster response robots.}, keywords = {External}, pubstate = {published}, tppubtype = {inproceedings} } This paper proposes a system to enable a humanoid robot to perform various tasks semi-autonomously according to higher-layer procedures called task sequences. A task sequence is a sequentially structured procedure that describes how to perform a particular task based on sensing data, motion planners, and a robot controller. These task sequences are processed by the task sequencer to move the robot. The goal of our system is to support comprehensive tasks, such as disaster response, with a number of task sequences defined for various subtasks. To efficiently develop required task sequences, the task sequencer is designed such that task sequences can be executed interactively; further, the task sequencer is integrated with a dynamics simulator that can be used to test the sequences without actually moving the robot. We verified our system by using it to make our HRP-2Kai robot perform the tasks defined in the DARPA Robotics Challenge, a competition involving disaster response robots. |
 | Hatledal, Lars Ivar; Zhang, Houxiang; Halse, Karl Henning; Hildre, Hans Petter: Numerical study for a catamaran gripper-monopile mechanism of a novel offshore wind turbine assembly installation procedure. ASME 2017 36th International Conference on Ocean, Offshore and Arctic Engineering, American Society of Mechanical Engineers Digital Collection 2017. (Type: Inproceedings | Abstract | Links | BibTeX | Tags: External) @inproceedings{hatledal2017numerical, title = {Numerical study for a catamaran gripper-monopile mechanism of a novel offshore wind turbine assembly installation procedure}, author = {Lars Ivar Hatledal and Houxiang Zhang and Karl Henning Halse and Hans Petter Hildre}, url = {https://www.semanticscholar.org/paper/Numerical-Study-for-a-Catamaran-Gripper-Monopile-of-Hatledal-Zhang/cc2cd384a1d1b1a36cab675be59b6aecc7e6432c?p2df}, doi = {10.1115/OMAE2017-62342}, year = {2017}, date = {2017-01-01}, booktitle = {ASME 2017 36th International Conference on Ocean, Offshore and Arctic Engineering}, organization = {American Society of Mechanical Engineers Digital Collection}, abstract = {Current methods for installation of offshore wind turbines are all sensitive to the weather conditions and the present cost level of offshore wind power is more than twice the cost of land-based units, increasing with water depth. This paper presents numerical simulations of a novel experimental gripper design to reduce the environmental effects applied to a catamaran type of vessel during wind turbine installation. In SFI MOVE project in NTNU Aalesund, our team proposed a novel wind turbine installation process. A new catamaran vessel will carry pre-assembled wind turbines to the installation location. Two new designed grippers on the deck will make a lifting operation to install the wind turbine onto the turbine foundation. Three prismatic grippers with several rolling contact points at the end are attached in an arc at the catamaran’s aft, designed to grasp the turbine foundation in order to make a connection between the two in the horizontal plane. This paper will only emphasize the contact responses between the turbine foundation and the three grippers during the wind turbine installation process. Numerical simulations are carried out using the virtual prototyping framework Vicosim which is developed by NTNU Aalesund. The simulation results show validation of a key part of the proposed new wind turbine installation idea.}, keywords = {External}, pubstate = {published}, tppubtype = {inproceedings} } Current methods for installation of offshore wind turbines are all sensitive to the weather conditions and the present cost level of offshore wind power is more than twice the cost of land-based units, increasing with water depth. This paper presents numerical simulations of a novel experimental gripper design to reduce the environmental effects applied to a catamaran type of vessel during wind turbine installation. In SFI MOVE project in NTNU Aalesund, our team proposed a novel wind turbine installation process. A new catamaran vessel will carry pre-assembled wind turbines to the installation location. Two new designed grippers on the deck will make a lifting operation to install the wind turbine onto the turbine foundation. Three prismatic grippers with several rolling contact points at the end are attached in an arc at the catamaran’s aft, designed to grasp the turbine foundation in order to make a connection between the two in the horizontal plane. This paper will only emphasize the contact responses between the turbine foundation and the three grippers during the wind turbine installation process. Numerical simulations are carried out using the virtual prototyping framework Vicosim which is developed by NTNU Aalesund. The simulation results show validation of a key part of the proposed new wind turbine installation idea. |
 | Li, Guoyuan; Urbina, Rodrigo; Zhang, Houxiang; Gomez, Juan G: Concept design and simulation of a water proofing modular robot for amphibious locomotion. 2017 International Conference on Advanced Mechatronic Systems (ICAMechS), pp. 145–150, IEEE 2017. (Type: Inproceedings | Abstract | Links | BibTeX | Tags: External) @inproceedings{li2017concept, title = {Concept design and simulation of a water proofing modular robot for amphibious locomotion}, author = {Guoyuan Li and Rodrigo Urbina and Houxiang Zhang and Juan G Gomez}, doi = {10.1109/ICAMechS.2017.8316566}, year = {2017}, date = {2017-01-01}, booktitle = {2017 International Conference on Advanced Mechatronic Systems (ICAMechS)}, pages = {145--150}, organization = {IEEE}, abstract = {This paper will introduce a novel adaptive modular robot for amphibious locomotion research. First, an overview of modular robotic research is given systematically. In this project, we concentrate on designing a new kind of modular robot with a central part and adaptable covers, so to build different configurations. The assemble prototypes could be used for bio-inspired locomotion research not only on ground, but also in water. The modular design, interfaces, and different configurations will be presented throughout. After that, related simulations including locomotion and swimming are shown to confirm the concept and principle. In the end, a conclusion is given and future work is outlined.}, keywords = {External}, pubstate = {published}, tppubtype = {inproceedings} } This paper will introduce a novel adaptive modular robot for amphibious locomotion research. First, an overview of modular robotic research is given systematically. In this project, we concentrate on designing a new kind of modular robot with a central part and adaptable covers, so to build different configurations. The assemble prototypes could be used for bio-inspired locomotion research not only on ground, but also in water. The modular design, interfaces, and different configurations will be presented throughout. After that, related simulations including locomotion and swimming are shown to confirm the concept and principle. In the end, a conclusion is given and future work is outlined. |
2016 |
|
 | He, Dahai: Virtual Winch Prototyping-Design, Modeling, Simulation and Testing of A Marine Hydraulic Winch System with Active Heave Compensation.. 2016. (Type: Masters Thesis | Abstract | Links | BibTeX | Tags: External) @mastersthesis{he2016virtual, title = {Virtual Winch Prototyping-Design, Modeling, Simulation and Testing of A Marine Hydraulic Winch System with Active Heave Compensation.}, author = {Dahai He}, url = {https://ntnuopen.ntnu.no/ntnu-xmlui/bitstream/handle/11250/2417673/He%2c%20D.%202016.pdf?sequence=1&isAllowed=y https://ntnuopen.ntnu.no/ntnu-xmlui/handle/11250/2417673 http://hdl.handle.net/11250/2417673}, year = {2016}, date = {2016-01-01}, abstract = {This thesis is to develop a standard virtual prototyping system for hydraulic winch system including developing a library of standard sub-models of hydraulic system, mechanical system and control system (AHC), and visualizing the simulation and operation of the virtual winch prototyping system. To be more specific: Chapter 1. Motivation and background of winch prototyping is introduced so as to break down the problems and formulate the objectives of this projects. Chapter 2. Theoretical background is shown in this part. It contains the briefly descriptions of the important theory applied in virtual prototyping winch system. Chapter 3. Methodology is shown in this part. It contains the detailed theory basis applied in the modelling of hydraulic and mechanical sub-systems of winch system. Chapter 4. This chapter describes the implementation of mechanical sub-system. 3D modelling, parameterization and visualization are implemented by using WebGL technology with three.js library. The outcome of the mechanical part can be easily integrated into the virtual prototyping framework. Chapter 5. This chapter elaborates the method and the process of hydraulic and control (AHC) sub-model modelling. Bond graph theory is applied during the modelling process. Different alternatives of hydraulic system structure are analysed and compared to finalize a better solution of hydraulic system structure. Chapter 6: This chapter explains the integration method of virtual prototyping winch system framework. Chapter 7: Results of mechanical modelling, hydraulic with control modelling and co-simulation of integrated virtual prototyping winch system are shown and discussed to evaluate the performance of virtual prototyping system. Chapter 8: This part makes conclusions, modelling alternatives and future work for the virtual prototyping winch system.}, keywords = {External}, pubstate = {published}, tppubtype = {mastersthesis} } This thesis is to develop a standard virtual prototyping system for hydraulic winch system including developing a library of standard sub-models of hydraulic system, mechanical system and control system (AHC), and visualizing the simulation and operation of the virtual winch prototyping system. To be more specific: Chapter 1. Motivation and background of winch prototyping is introduced so as to break down the problems and formulate the objectives of this projects. Chapter 2. Theoretical background is shown in this part. It contains the briefly descriptions of the important theory applied in virtual prototyping winch system. Chapter 3. Methodology is shown in this part. It contains the detailed theory basis applied in the modelling of hydraulic and mechanical sub-systems of winch system. Chapter 4. This chapter describes the implementation of mechanical sub-system. 3D modelling, parameterization and visualization are implemented by using WebGL technology with three.js library. The outcome of the mechanical part can be easily integrated into the virtual prototyping framework. Chapter 5. This chapter elaborates the method and the process of hydraulic and control (AHC) sub-model modelling. Bond graph theory is applied during the modelling process. Different alternatives of hydraulic system structure are analysed and compared to finalize a better solution of hydraulic system structure. Chapter 6: This chapter explains the integration method of virtual prototyping winch system framework. Chapter 7: Results of mechanical modelling, hydraulic with control modelling and co-simulation of integrated virtual prototyping winch system are shown and discussed to evaluate the performance of virtual prototyping system. Chapter 8: This part makes conclusions, modelling alternatives and future work for the virtual prototyping winch system. |
 | Li, Guoyuan; Skogeng, Pedersen Birger; Deng, Yuxiang; Hatledal, Lars Ivar; Zhang, Houxiang: Towards a virtual prototyping framework for ship maneuvering in offshore operations. OCEANS 2016-Shanghai, pp. 1–6, IEEE 2016. (Type: Inproceedings | Abstract | Links | BibTeX | Tags: External) @inproceedings{li2016towards, title = {Towards a virtual prototyping framework for ship maneuvering in offshore operations}, author = {Guoyuan Li and Pedersen Birger Skogeng and Yuxiang Deng and Lars Ivar Hatledal and Houxiang Zhang}, url = {https://folk.ntnu.no/gulj/myPaper/2016_li_towards.pdf}, year = {2016}, date = {2016-01-01}, booktitle = {OCEANS 2016-Shanghai}, pages = {1--6}, organization = {IEEE}, abstract = {This paper presents a virtual prototyping framework that can achieve modeling, simulation and control for ship maneuvering in offshore operations. To fast construct scenario for certain ship maneuvering tasks, a scenario editor is designed to model the ship, the environment disturbances and the scene, respectively. The corresponding scenario containing physical properties is built up in a physics simulation engine AgX. A graphical user interface responsible for visualizing the simulation and plotting data in a real-time manner is developed, in which dynamic interaction including manual control, failure/recover of thrusters and weather change is implemented. Taking advantages of a distributed communication architecture, the plug-in control mechanism is realized to increase the flexibility for evaluating ship maneuvering performance. Through a case study of trajectory tracking, the framework is verified efficient in constructing scenario and testing control model for ship maneuvering applications.}, keywords = {External}, pubstate = {published}, tppubtype = {inproceedings} } This paper presents a virtual prototyping framework that can achieve modeling, simulation and control for ship maneuvering in offshore operations. To fast construct scenario for certain ship maneuvering tasks, a scenario editor is designed to model the ship, the environment disturbances and the scene, respectively. The corresponding scenario containing physical properties is built up in a physics simulation engine AgX. A graphical user interface responsible for visualizing the simulation and plotting data in a real-time manner is developed, in which dynamic interaction including manual control, failure/recover of thrusters and weather change is implemented. Taking advantages of a distributed communication architecture, the plug-in control mechanism is realized to increase the flexibility for evaluating ship maneuvering performance. Through a case study of trajectory tracking, the framework is verified efficient in constructing scenario and testing control model for ship maneuvering applications. |
 | Park, Kwang-Phil; Ham, Seung-Ho; Lee, Chan-Young: Application and validation of production planning simulation in shipbuilding. Ocean Engineering, 114 , pp. 154–167, 2016. (Type: Journal Article | Abstract | Links | BibTeX | Tags: External) @article{park2016application, title = {Application and validation of production planning simulation in shipbuilding}, author = {Kwang-Phil Park and Seung-Ho Ham and Chan-Young Lee}, doi = {10.1016/j.oceaneng.2016.01.008}, year = {2016}, date = {2016-01-01}, journal = {Ocean Engineering}, volume = {114}, pages = {154--167}, publisher = {Elsevier}, abstract = {As the weight and size of assembly blocks are getting increased, new production procedures by using floating cranes have been proposed to enhance the efficiency in shipyards. In this situation, simulation technology is required to evaluate potential risks of the procedure in advance. By such a necessity, we have developed a simulation system, named SIMSON (SIMulation System Of New production planning). SIMSON calculates the motion of the lifted block and floating bodies such as vessels and floating cranes based on the multibody system dynamics with the hydrostatic and hydrodynamic forces. The calculated motion and wire rope tension are used for dynamic effect estimation. In this paper, we present the application cases of SIMSON to real production process. The simulation results are compared by observing the situation in the real operations. The observation illustrates the simulation results are in harmony with the real situation and the application of SIMSON to production planning simulation in shipyards is quite feasible.}, keywords = {External}, pubstate = {published}, tppubtype = {article} } As the weight and size of assembly blocks are getting increased, new production procedures by using floating cranes have been proposed to enhance the efficiency in shipyards. In this situation, simulation technology is required to evaluate potential risks of the procedure in advance. By such a necessity, we have developed a simulation system, named SIMSON (SIMulation System Of New production planning). SIMSON calculates the motion of the lifted block and floating bodies such as vessels and floating cranes based on the multibody system dynamics with the hydrostatic and hydrodynamic forces. The calculated motion and wire rope tension are used for dynamic effect estimation. In this paper, we present the application cases of SIMSON to real production process. The simulation results are compared by observing the situation in the real operations. The observation illustrates the simulation results are in harmony with the real situation and the application of SIMSON to production planning simulation in shipyards is quite feasible. |
2015 |
|
 | Hatledal, Lars Ivar; Schaathun, Hans Georg; Zhang, Houxiang: A software architecture for simulation and visualisation based on the functional mock-up interface and web technologies. Proceedings of The 57th Conference on Simulation and Modelling (SIMS 56): October, 7-9, 2015, Linköping University, Sweden, Linköping University Electronic Press, Linköpings universitet 2015. (Type: Inproceedings | Abstract | Links | BibTeX | Tags: External) @inproceedings{hatledal2015software, title = {A software architecture for simulation and visualisation based on the functional mock-up interface and web technologies}, author = {Lars Ivar Hatledal and Hans Georg Schaathun and Houxiang Zhang}, url = {https://www.researchgate.net/profile/Hans-Georg-Schaathun/publication/300217936_A_Software_Architecture_for_Simulation_and_Visualisation_based_on_the_Functional_Mock-up_Interface_and_Web_Technologies/links/575a9bc108aec91374a603fd/A-Software-Architecture-for-Simulation-and-Visualisation-based-on-the-Functional-Mock-up-Interface-and-Web-Technologies.pdf }, doi = {10.3384/ecp15119123}, year = {2015}, date = {2015-01-01}, booktitle = {Proceedings of The 57th Conference on Simulation and Modelling (SIMS 56): October, 7-9, 2015, Linköping University, Sweden}, organization = {Linköping University Electronic Press, Linköpings universitet}, abstract = {This paper presents a software architecture for a collabora-tive virtual environment (CVE) for simulation and visual-isation based on the Functional Mock-up Interface (FMI)for co-simulation and web technologies. FMI has beenchosen in order to have a standardised and independentinterface to models created in different modelling tools.The user interface has been implemented using webtechnologies, which enables a very high degree of flexi-bility. The Web Graphics Library (WebGL) is used for in-teractive 3D visualisations, enabling native cross-platformrendering directly in the browser without the need ofinstalling any additional plug-ins. Employing the bi-directional communication capabilities of the WebSocketprotocol, multiple users can interact with the same simu-lation models simultaneously.A software prototype has been developed in order todemonstrate the applicability of the proposed architecture.As a case study, we have considered virtual prototypingof marine cranes, to illustrate the use on real world prob-lems.}, keywords = {External}, pubstate = {published}, tppubtype = {inproceedings} } This paper presents a software architecture for a collabora-tive virtual environment (CVE) for simulation and visual-isation based on the Functional Mock-up Interface (FMI)for co-simulation and web technologies. FMI has beenchosen in order to have a standardised and independentinterface to models created in different modelling tools.The user interface has been implemented using webtechnologies, which enables a very high degree of flexi-bility. The Web Graphics Library (WebGL) is used for in-teractive 3D visualisations, enabling native cross-platformrendering directly in the browser without the need ofinstalling any additional plug-ins. Employing the bi-directional communication capabilities of the WebSocketprotocol, multiple users can interact with the same simu-lation models simultaneously.A software prototype has been developed in order todemonstrate the applicability of the proposed architecture.As a case study, we have considered virtual prototypingof marine cranes, to illustrate the use on real world prob-lems. |
2014 |
|
 | Metrikin, Ivan: A software framework for simulating stationkeeping of a vessel in discontinuous ice. Modeling, Identification and Control 2014, pp. 211–248, Norsk Forening for Automatisering, 2014. (Type: Inproceedings | Abstract | Links | BibTeX | Tags: External) @inproceedings{metrikin2014software, title = {A software framework for simulating stationkeeping of a vessel in discontinuous ice}, author = {Ivan Metrikin}, url = {https://ntnuopen.ntnu.no/ntnu-xmlui/bitstream/handle/11250/2392045/MIC-2014-4-2%2b-%2bMetrikin.pdf?sequence=3&isAllowed=y http://hdl.handle.net/11250/2392045}, doi = {10.4173/mic.2014.4.2}, year = {2014}, date = {2014-01-01}, booktitle = {Modeling, Identification and Control 2014}, volume = {35}, number = {4}, pages = {211--248}, publisher = {Norsk Forening for Automatisering}, abstract = {This paper describes a numerical package for simulating stationkeeping operations of an offshore vessel in floating sea ice. The software has found broad usage in both academic and industrial projects related to design and operations of floating structures in the Arctic. Interactions with both intact and broken ice conditions can be simulated by the numerical tool, but the main emphasis is placed on modelling managed ice environments relevant for prospective petroleum industry operations in the Arctic. The paper gives a thorough description of the numerical tool from both theoretical and software implementation perspectives. Structural meshing, ice field generation, multibody modelling and ice breaking aspects of the model are presented and discussed. Finally, the main assumptions and limitations of the computational techniques are elucidated and further work directions are suggested.}, keywords = {External}, pubstate = {published}, tppubtype = {inproceedings} } This paper describes a numerical package for simulating stationkeeping operations of an offshore vessel in floating sea ice. The software has found broad usage in both academic and industrial projects related to design and operations of floating structures in the Arctic. Interactions with both intact and broken ice conditions can be simulated by the numerical tool, but the main emphasis is placed on modelling managed ice environments relevant for prospective petroleum industry operations in the Arctic. The paper gives a thorough description of the numerical tool from both theoretical and software implementation perspectives. Structural meshing, ice field generation, multibody modelling and ice breaking aspects of the model are presented and discussed. Finally, the main assumptions and limitations of the computational techniques are elucidated and further work directions are suggested. |
2012 |
|
| Metrikin, Ivan; Lu, Wenjun; Lubbad, Raed; Løset, Sveinung; Kashafutdinov, Marat: Numerical Simulation of a Floater in a Broken-Ice Field: Part I—Model Description. International Conference on Offshore Mechanics and Arctic Engineering, pp. 579–588, American Society of Mechanical Engineers 2012. (Type: Inproceedings | Abstract | Links | BibTeX | Tags: External) @inproceedings{metrikin2012numerical, title = {Numerical Simulation of a Floater in a Broken-Ice Field: Part I—Model Description}, author = {Ivan Metrikin and Wenjun Lu and Raed Lubbad and Sveinung Løset and Marat Kashafutdinov}, doi = {10.1115/OMAE2012-83938}, year = {2012}, date = {2012-01-01}, booktitle = {International Conference on Offshore Mechanics and Arctic Engineering}, volume = {44939}, pages = {579--588}, organization = {American Society of Mechanical Engineers}, abstract = {This paper presents a novel concept for simulating the ice-floater interaction process. The concept is based on a mathematical model which emphasizes the station-keeping scenario, i.e. when the relative velocity between the floater and the ice is comparatively small. This means that the model is geared towards such applications as dynamic positioning in ice and ice management. The concept is based on coupling the rigid multibody simulations with the Finite Element Method (FEM) simulations. The rigid multibody simulation is implemented through a physics engine which is used to model the dynamic behaviour of rigid bodies which undergo large translational and rotational displacements (the floater and the ice floes). The FEM is used to simulate the material behaviour of the ice and the fluid, i.e. the ice breaking and the hydrodynamics of the ice floes. Within this framework, the physics engine is responsible for dynamically detecting the contacts between the objects in the calculation domain, and the FEM software is responsible for calculating the contact forces. The concept is applicable for simulations in a three-dimensional space (3D). The model described in this paper is divided into two main parts: the mathematical ice model and the mathematical floater model. The mathematical ice model allows modelling both intact level ice and discontinuous ice within a single framework. However, the primary focus of this paper is placed on modelling the broken ice conditions. A floater is modelled as a rigid body with 6 degrees of freedom, i.e. no deformations of the floater’s hull are allowed. Nevertheless, the hydrodynamics of the floater and the ice is considered within the outlined model. The presented approach allows implementing realistic, high fidelity 3D simulations of the ice-fluid-structure interaction process.}, keywords = {External}, pubstate = {published}, tppubtype = {inproceedings} } This paper presents a novel concept for simulating the ice-floater interaction process. The concept is based on a mathematical model which emphasizes the station-keeping scenario, i.e. when the relative velocity between the floater and the ice is comparatively small. This means that the model is geared towards such applications as dynamic positioning in ice and ice management. The concept is based on coupling the rigid multibody simulations with the Finite Element Method (FEM) simulations. The rigid multibody simulation is implemented through a physics engine which is used to model the dynamic behaviour of rigid bodies which undergo large translational and rotational displacements (the floater and the ice floes). The FEM is used to simulate the material behaviour of the ice and the fluid, i.e. the ice breaking and the hydrodynamics of the ice floes. Within this framework, the physics engine is responsible for dynamically detecting the contacts between the objects in the calculation domain, and the FEM software is responsible for calculating the contact forces. The concept is applicable for simulations in a three-dimensional space (3D). The model described in this paper is divided into two main parts: the mathematical ice model and the mathematical floater model. The mathematical ice model allows modelling both intact level ice and discontinuous ice within a single framework. However, the primary focus of this paper is placed on modelling the broken ice conditions. A floater is modelled as a rigid body with 6 degrees of freedom, i.e. no deformations of the floater’s hull are allowed. Nevertheless, the hydrodynamics of the floater and the ice is considered within the outlined model. The presented approach allows implementing realistic, high fidelity 3D simulations of the ice-fluid-structure interaction process. | |
| Metrikin, Ivan; Borzov, Andrey; Lubbad, Raed; Løset, Sveinung: Numerical simulation of a floater in a broken-ice field: Part II—Comparative study of physics engines. International Conference on Offshore Mechanics and Arctic Engineering, pp. 477–486, American Society of Mechanical Engineers 2012. (Type: Inproceedings | Abstract | Links | BibTeX | Tags: External) @inproceedings{metrikin2012numericalb, title = {Numerical simulation of a floater in a broken-ice field: Part II—Comparative study of physics engines}, author = {Ivan Metrikin and Andrey Borzov and Raed Lubbad and Sveinung Løset}, doi = {10.1115/OMAE2012-83430}, year = {2012}, date = {2012-01-01}, booktitle = {International Conference on Offshore Mechanics and Arctic Engineering}, volume = {44939}, pages = {477--486}, organization = {American Society of Mechanical Engineers}, abstract = {Numerical simulation of a floater in ice-infested waters can be performed using a physics engine. This software can dynamically detect contacts and calculate the contact forces in a three-dimensional space among various irregularly shaped bodies, e.g. the floater and the ice floes. Previously, various physics engines were successfully applied to simulate floaters in ice. However, limited attention was paid to the criteria for selecting a particular engine for the simulation of a floater in broken-ice conditions. In this paper, four publicly available physics engines (AgX Multiphysics, Open Dynamics Engine, PhysX and Vortex) are compared in terms of integration performance and contact detection accuracy. These two aspects are assumed to be the most important for simulating a floater in broken ice. Furthermore, the access to code, documentation quality and the level of technical support are evaluated and discussed. The main conclusion is that each physics engine has its own strength and weaknesses and none of the engines is perfect. These strength and weaknesses are revealed and discussed in the paper.}, keywords = {External}, pubstate = {published}, tppubtype = {inproceedings} } Numerical simulation of a floater in ice-infested waters can be performed using a physics engine. This software can dynamically detect contacts and calculate the contact forces in a three-dimensional space among various irregularly shaped bodies, e.g. the floater and the ice floes. Previously, various physics engines were successfully applied to simulate floaters in ice. However, limited attention was paid to the criteria for selecting a particular engine for the simulation of a floater in broken-ice conditions. In this paper, four publicly available physics engines (AgX Multiphysics, Open Dynamics Engine, PhysX and Vortex) are compared in terms of integration performance and contact detection accuracy. These two aspects are assumed to be the most important for simulating a floater in broken ice. Furthermore, the access to code, documentation quality and the level of technical support are evaluated and discussed. The main conclusion is that each physics engine has its own strength and weaknesses and none of the engines is perfect. These strength and weaknesses are revealed and discussed in the paper. | |
2011 |
|
 | Wan, Yijun: Discrete element method in granular material simulations. 2011. (Type: Masters Thesis | Abstract | Links | BibTeX | Tags: External) @mastersthesis{wan2011discrete, title = {Discrete element method in granular material simulations}, author = {Yijun Wan}, url = {https://pure.tue.nl/ws/portalfiles/portal/47015912/716753-1.pdf}, year = {2011}, date = {2011-01-01}, journal = {Institute of Fraunhofer ITWM Kaiserslautern/Technical University of Kaiserslautern}, abstract = {This thesis describes the theories and simulations of granular material using discrete element method. With wide applications in agriculture and mechanical engineering, granular material exhibits a number of unique physical properties. The understanding of such properties is important in order to evaluate the performance of existing methodologies and to trigger the development of new models for different functionalities in the future. As a microscopic approach, discrete element method has been proved to be adequate in most simulations of granular material. An elaborated description is provided to illustrate a three-phase scheme from the fundamental discrete element model, which includes contact detection, force interaction and time integration. Additional to the conventional scheme, we present a bonding model with a connecting rod between each pair of contacted particles. Two enhanced bonding models are discussed in detail, with special characteristics in accordance with brittle and crack propagation features, respectively. On the contrary, continuum mechanical models give a macroscopic view to investigate granular material behaviors. Difficulties arise from the solving of a complex system of partial differential equations and the connections between model parameters and phenomenological ones. Moreover, triaxial test, uniaxial compression test and blade test are chosen as three representative experiments in granular material study. Simulation results implementing discrete element method are analyzed and discussed regarding the role of different parameters. By carefully choosing models and adjusting parameters, simulation results can have a good quantitative agreement with laboratory measurements. One of our kernel concerns is the computational complexity. Therefore, we focus on exploring effective simplified models with fewer variables.}, keywords = {External}, pubstate = {published}, tppubtype = {mastersthesis} } This thesis describes the theories and simulations of granular material using discrete element method. With wide applications in agriculture and mechanical engineering, granular material exhibits a number of unique physical properties. The understanding of such properties is important in order to evaluate the performance of existing methodologies and to trigger the development of new models for different functionalities in the future. As a microscopic approach, discrete element method has been proved to be adequate in most simulations of granular material. An elaborated description is provided to illustrate a three-phase scheme from the fundamental discrete element model, which includes contact detection, force interaction and time integration. Additional to the conventional scheme, we present a bonding model with a connecting rod between each pair of contacted particles. Two enhanced bonding models are discussed in detail, with special characteristics in accordance with brittle and crack propagation features, respectively. On the contrary, continuum mechanical models give a macroscopic view to investigate granular material behaviors. Difficulties arise from the solving of a complex system of partial differential equations and the connections between model parameters and phenomenological ones. Moreover, triaxial test, uniaxial compression test and blade test are chosen as three representative experiments in granular material study. Simulation results implementing discrete element method are analyzed and discussed regarding the role of different parameters. By carefully choosing models and adjusting parameters, simulation results can have a good quantitative agreement with laboratory measurements. One of our kernel concerns is the computational complexity. Therefore, we focus on exploring effective simplified models with fewer variables. |