Robot falling within simulation

Omniverse Isaac Sim
1

Isaac Sim Version

4.5.0
4.2.0
4.1.0
4.0.0
4.5.0
2023.1.1
2023.1.0-hotfix.1
Other (please specify):

Operating System

Ubuntu 22.04
Ubuntu 20.04
Windows 11
Windows 10
Other (please specify):

GPU Information

  • Model: NVIDIA RTX 3500 Ada Generation
  • Driver Version: 570.124.06

Topic Description

Detailed Description

I imported my own robot in Isaac Sim using the urdf importer. However, when I sent the import_config.default_drive_type to UrdfJointTargetType.JOINT_DRIVE_POSITION, my robot moved on a short distance and fell. When I switch to UrdfJointTargetType.JOINT_DRIVE_VELOCITY, it doesn’t fall, but the robot joints do not move as I programmed them. For instance, the camera is supposed to move,g but it does not with UrdfJointTargetType.JOINT_DRIVE_VELOCITYthus. I had to use UrdfJointTargetType.JOINT_DRIVE_POSITION

I set the robot element masses following its urdf.

Base Components

  • Base Link: 2.4kg
  • Wheels (each): 0.01kg
  • Caster Wheels (each): 0.01kg
  • Plate Link: 0.571995kg
  • Battery Link: 1.194kg

Arm Components

  • Arm Base Link: 0.379673kg
  • Shoulder Link: 0.480879kg
  • Upper Arm Link: 0.430811kg
  • Upper Forearm Link: 0.234589kg
  • Lower Forearm Link: 0.220991kg
  • Wrist Link: 0.084957kg

Gripper Components

  • Gripper Link: 0.072885kg
  • Gripper Prop Link: 0.00434kg
  • Gripper Bar Link: 0.034199kg
  • Left Finger Link: 0.016246kg
  • Right Finger Link: 0.016246kg

Camera and Sensors

  • Camera Tower Link: 2.366224kg (significant weight!)
  • Pan Link: 0.098997kg
  • Tilt Link: 0.019845kg
  • Camera Link: 0.072kg
  • Lidar Tower Link: 0.155485kg
  • Laser Frame Link: 0.196kg

Screenshots or Videos

3

Hi there,

Thank you for your question. When you put all the joints in your robot into position control. it is likely that the torque output to the wheels can be large causing it to easily topple over. You want to use velocity control for the wheels and could keep position control for the camera. To change the control mode for specific joints use switch_control_mode

4

Dear Michalin,

Thank you! I’ve been looking for this for a while.