Unable to move custom vehicle in the simulation environment

[Carl_0127]

Isaac Sim Version

[✔] 5.0.0

Operating System

[✔] Ubuntu 24.04

GPU Information

• Model: RTX-A4000
• Driver Version: 575.64.03

Topic Description

Unable to move custom vehicle in the simulation environment.

Detailed Description

I customized a single-steering-wheel vehicle in URDF format and converted it into USD format through Isaac Sim. Using a Python script, I assigned a velocity to the steering wheel, but I found that when the wheel touches the ground, it doesn’t rotate and the vehicle cannot move. Only when I increase the vehicle’s z-coordinate to lift it off the ground does the wheel start rotating. Other joint like fork can be controlled.

Steps to Reproduce

ware_house = stage_utils.add_reference_to_stage("warehouse.usd", "/World/warehouse")
robot_prim = stage_utils.add_reference_to_stage("Robot.usd", "/World/Robot")
simulation_context = SimulationContext()
simulation_context.initialize_physics()
robot = Articulation(prim_paths_expr="/World/Robot", name="Robot")
robot.initialize()
robot.set_gains(kps=[0], kds=[50], indices=[0], joint_indices=[self.steer_weel_id]) #suggestion from gpt
robot.set_max_efforts(values=[1000], joint_indices=[self.steer_wheel_id])
robot.set_joint_velocity_targets(velocities=[50], joint_indices=[self.steer_wheel_id])

[Carl_0127]

I tried to use vehicle from isaacsim assets. It can be moved with the same code. And I found some difference between the robot from isaacsim assets and my custom robot. The icon of customized robot has a blue arrow, but the official robot has a orange arrow. What dose the diffrence mean? And when lift the official robot off the ground, it can fall back to the ground automatically. But customized robot can not, it just frozen in the air.

[Simplychenable]

@Carl_0127 the color of the arrow corresponds to the composition arc and how it’s being brought into your USD stage/scene. blue indicates payload while orange is reference composition arc. you can switch between them if you were to right click on the selective composition arc in the stage list.

you can read more about the composition arcs here as it’s a core concept with OpenUSD - Glossary — Isaac Sim Documentation

that said, i suspect it’s not the root cause of the simulation but worth a try first.