7. Dimensions and units

Below is a table showing the dimensions and its associated units in AGX Dynamics. Where possible, SI units are being used. Many of the units are derived from the gravitational acceleration \(g\). It has a default value in AGX Dynamics of 9.80665 m/s² and can be found in agx/Math.h.

Table 7.1 Dimensions and units used in AGX Dynamics.

Dimension	Unit
Acceleration	m/s2
Angle	rad
Angular velocity	rad/s
Angular acceleration	rad/s2
Cohesion	Pa
Compliance (rotational)	rad/Nm
Compliance (translational)	m/N
Damping [*]	s
Damping (rotational)	Nms/rad
Damping (translational)	Ns/m
Surface viscosity [†]	m/s/N or s/kg
Density	kg/m3
Electric potential	V
Electric resistance	Ohm
Force	N
Length	m
Mass	kg
Moment of inertia	kg m2
Pressure	Pa
Speed	m/s
Stiffness (rotational)	Nm/rad
Stiffness (translational)	N/m
Torque	Nm
Young’s Modulus	Pa

[*]

Damping in AGX Dynamics refers to the damping time constant. It is a holonomic constraint-stabilization parameter for the time integration, expressed in seconds. It indicates roughly how quickly a holonomic constraint takes to dissipate energy and get back to the rest state; the damping effect usually scales with the simulation time step \(\Delta t\).

[†]

Surface viscosity is a regulerization parameter for nonholonomic constraint that quantifies how easily a force generates velocity; the unit \(m/s/N\) = \(s/kg\) denotes velocity per unit force (mechanical mobility).