"""A four-wheel vehicle driving from deformable terrain onto a rigid platform. Each agxVehicle.Tire owns a GTire and a TerrainWheel. Configure both child models explicitly and give them separate materials: GTire handles rigid geometry while TerrainWheel handles deformable AGX Terrain. """ import math import agx import agxCollide import agxOSG import agxRender import agxSDK import agxTerrain import agxUtil import agxVehicle from agxPythonModules.utils.callbacks import StepEventCallback from agxPythonModules.utils.environment import init_app, root, simulation from agxPythonModules.utils.terrain import create_visual WHEEL_RADIUS = 0.5 WHEEL_WIDTH = 0.4 WHEEL_MASS = 10.0 CHASSIS_HALF_EXTENTS = agx.Vec3(1.2, 2.0, 0.5) CHASSIS_MASS = 1000.0 SUSPENSION_RANGE = 0.1 SUSPENSION_STIFFNESS = 1.0e6 SUSPENSION_DAMPING = 4.0e4 def create_g_tire_parameters(): """Return an explicit GTire parameter set for the rigid-platform contacts.""" parameters = agxVehicle.GTireParameters() parameters.nominalInflationPressure = 220000.0 parameters.inflationPressure = 220000.0 parameters.verticalStiffness = 209651.0 parameters.dKz_dP = 0.7098 parameters.verticalDamping = 150.0 parameters.longitudinalStiffness = 358066.0 parameters.dKx_dP_lin = 0.17504 parameters.dKx_dP_quad = 0.0 parameters.lateralStiffness = 358066.0 parameters.dKy_dP = 0.16365 parameters.yawStiffness = 6000.0 parameters.muStatic = 1.0 parameters.muDynamic = 1.0 parameters.rollingResistance = 0.00702 parameters.rollingResistance_v = 0.001515 parameters.rollingResistance_v4 = 8.514e-5 parameters.rollingResistance_Fz = 0.0 parameters.rollingResistance_P = 0.0 parameters.minReferenceSpeed = 0.1 return parameters def configure_terrain_wheel(terrain_wheel): """Set the TerrainWheel model parameters used for deformable-terrain contacts.""" settings = terrain_wheel.getTerrainWheelSettings() settings.setPressureSinkageModel( agxTerrain.TerrainWheelSettings.PressureSinkageModel_REECE) settings.setEnableComputeMaximumNormalStressAngleFromFrontAngle(True) settings.setEnableComputeRearAngleFromFrontAngle(False) class BoxCar(agxSDK.Assembly): """A simple box car with four tires using the unified tire class.""" def __init__(self): super().__init__() self.g_tire_material = agx.Material("unified_g_tire") self.terrain_wheel_material = agx.Material("unified_terrain_wheel") self.drive_motors = [] self.wheels = [] self.wheel_joints = [] self.chassis = agx.RigidBody("chassis") self.chassis.add(agxCollide.Geometry(agxCollide.Box(CHASSIS_HALF_EXTENTS))) self.chassis.getMassProperties().setMass(CHASSIS_MASS) self.add(self.chassis) chassis_visual = agxOSG.createVisual(self.chassis, root()) agxOSG.setDiffuseColor(chassis_visual, agxRender.Color.Blue()) agxOSG.setAlpha(chassis_visual, 0.3) wheel_axis = -agx.Vec3.X_AXIS() steering_axis = agx.Vec3.Z_AXIS() for index, local_position in enumerate(self.wheel_positions()): tire = self.create_tire() tire.setPosition(local_position) tire.setRotation(agx.Quat(agx.Vec3.Y_AXIS(), agx.Vec3.X_AXIS())) tire.getTireBody().getMassProperties().setMass(WHEEL_MASS) self.add(tire) self.wheels.append(tire) anchor = agx.Vec3( math.copysign(CHASSIS_HALF_EXTENTS.x(), local_position.x()), math.copysign(CHASSIS_HALF_EXTENTS.y(), local_position.y()), local_position.z(), ) joint = agxVehicle.WheelJoint( agxVehicle.WheelJointFrame(anchor, wheel_axis, steering_axis), tire.getGTire().getTireCarrier(), self.chassis) # The front wheels are steerable; the Ackermann constraint below # keeps their steering angles coupled. joint.getLock1D(agxVehicle.WheelJoint.STEERING).setEnable(index >= 2) joint.getMotor1D(agxVehicle.WheelJoint.STEERING).setEnable(False) joint.getLock1D(agxVehicle.WheelJoint.WHEEL).setEnable(True) joint.getRange1D(agxVehicle.WheelJoint.SUSPENSION).setEnable(True) joint.getRange1D(agxVehicle.WheelJoint.SUSPENSION).setRange( -SUSPENSION_RANGE, SUSPENSION_RANGE) suspension = joint.getLock1D(agxVehicle.WheelJoint.SUSPENSION) suspension.setEnable(True) suspension.setCompliance( agxUtil.convertSpringConstantToCompliance(SUSPENSION_STIFFNESS)) suspension.setAttenuation(agxUtil.convertDampingCoefficientToAttenuation( SUSPENSION_DAMPING, SUSPENSION_STIFFNESS, simulation().getTimeStep())) self.add(joint) self.wheel_joints.append(joint) agxUtil.setEnableCollisions(self.chassis, tire.getTireBody(), False) motor = tire.getGTire().getCarcassHinge().getMotor1D() motor.setSpeed(-2.0 / WHEEL_RADIUS) motor.setForceRange(agx.RangeReal(1.0e5)) motor.setEnable(False) self.drive_motors.append(motor) # The two tire geometries overlap, so render only the GTire geometry. for geometry in tire.getTireBody().getGeometries(): if geometry.getName() == "GTireGeometry": agxOSG.createVisual(geometry, root()) # The first two wheels are the front pair. Without this constraint, # their unlocked steering DOFs can rotate independently about Z. self.steering = agxVehicle.Ackermann( self.wheel_joints[1], self.wheel_joints[0]) self.add(self.steering) self.setPosition(-12.0, 0.0, 1.5) self.setRotation(agx.EulerAngles(0.0, 0.0, -0.5 * agx.PI)) @staticmethod def wheel_positions(): z = -CHASSIS_HALF_EXTENTS.z() - 0.6 + WHEEL_RADIUS x = CHASSIS_HALF_EXTENTS.x() + WHEEL_WIDTH y = CHASSIS_HALF_EXTENTS.y() return (agx.Vec3(+x, +y, z), agx.Vec3(-x, +y, z), agx.Vec3(+x, -y, z), agx.Vec3(-x, -y, z)) def create_tire(self): tire = agxVehicle.Tire(WHEEL_RADIUS, WHEEL_WIDTH) g_tire = tire.getGTire() terrain_wheel = tire.getTerrainWheel() # These materials must be different: the two models configure their # respective material pairs differently. g_tire.setMaterial(self.g_tire_material) terrain_wheel.setMaterial(self.terrain_wheel_material) # Configure each model independently. g_tire.setGTireParameters(create_g_tire_parameters()) configure_terrain_wheel(terrain_wheel) g_tire.getCarcassHinge().getLock1D().setEnable(False) return tire def configure_terrain_contacts(self, terrain): material_manager = simulation().getMaterialManager() for tire in self.wheels: contact_material = material_manager.getOrCreateContactMaterial( terrain.getMaterial(), tire.getTerrainWheel().getMaterial()) agxTerrain.TerrainWheel.configureContactMaterial(contact_material) contact_material.setRestitution(0.0) def enable_drive(self): for motor in self.drive_motors: motor.setEnable(True) def buildScene(): simulation().setTimeStep(1.0 / 120.0) simulation().setUniformGravity(agx.Vec3(0.0, 0.0, -9.81)) terrain = agxTerrain.Terrain(281, 281, 0.15, 2.0) terrain.setPosition(agx.Vec3(-1.0, 0.0, 0.0)) terrain.loadLibraryMaterial("terrain_wheel_sand_1") # TerrainWheel reads terramechanics parameters from the terrain material. # Change one parameter explicitly as an example: the Bekker frictional # modulus k_phi [N/m^(n+2)]. terrain.getTerrainMaterial().getTerramechanicsProperties().setFrictionalModulusBekker( 1.5e6) terrain.setMaterial(agx.Material("terrain")) simulation().add(terrain) create_visual(terrain, render_particles=True, render_height_field=True) platform = agx.RigidBody("rigid platform") platform.add(agxCollide.Geometry(agxCollide.Box(4.0, 4.0, 0.05))) platform.setPosition(0.0, 0.0, -0.025) platform.setMotionControl(agx.RigidBody.STATIC) simulation().add(platform) platform_visual = agxOSG.createVisual(platform, root()) agxOSG.setDiffuseColor(platform_visual, agxRender.Color.DimGray()) vehicle = BoxCar() simulation().add(vehicle) vehicle.configure_terrain_contacts(terrain) StepEventCallback.callAt(1.0, vehicle.enable_drive) def set_camera(app): app.setCameraHome(agx.Vec3(-12.0, -15.0, 8.0), agx.Vec3(0.0, 0.0, 0.5), agx.Vec3.Z_AXIS()) init = init_app(name=__name__, scenes=[(buildScene, "1")], autoStepping=True, onInitialized=set_camera)