I am using the physX Vehicle Wizard NoDrive model and I have the ability to apply Drive Torque to each wheel. I would like to know the formula to set the drive torque per each wheel so I can make sure the car has a constant velocity, as defined by me. In short, I want to be able to apply the torque knowing the car’s final speed when the torque is applied. Through my experiments, I realized there was a constant and linear relationship between the drive torque and the vehicle rigid body linear velocity, but that is not enough in my situation. Another question is, is there aerodynamic drag in the Isaac Sim? What causes the car to reach constant linear velocity when constant torque is applied, if there is no aerodynamic drag?
Referring purely to the PhysX/omni.physx side here (using omni.physx Vehicle Creation Wizard and then simulate without any potential IsaacSim logic on top):
- aerodynamic drag is not modeled. You have to compute and apply that force as user code
- about reaching a desired speed: there is no simple formula that would guarantee that a certain torque will result in the desired speed in all cases. Often you would build some PID type of controller to set the torque
- when directly applying torque on the wheels, it is up to you to define some sort of graph that couples, for example, linear speed to torque (to somewhat emulate the behavior of a motor). With a PID controller, you probably have to worry less about it (as long as the torque values stay within some reasonable range)
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