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ros-controls / gazebo_ros2_control

Wrappers, tools and additional API's for using ros2_control with Gazebo Classic
Apache License 2.0
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Position_controller not working properly as wheel controller of mobile robot #342

Closed HPCLOL closed 3 months ago

HPCLOL commented 3 months ago

I am trying to use ROS2 to make a mobile robot move in Gazebo, and the mobile robot just looks like a vehicle with four wheels. For some reason, I use the position_controller to control each wheel. When I post a series of trajectory points to the position controller, the wheels rotated but the robot did not move, as if it is slipping. When I replace the controller with the velocity_controller or effort_controller , the wheels can drive the robot to move normally. I have checked the URDF file and there are no issues with the contact and friction between the wheels and the ground.

I want to know why this happens and want to control the wheels through the position_controller to make the robot move.

My ros2 version is iron, and I use gazebo classic.

Thank you so much!

christophfroehlich commented 3 months ago

I guess this is the same result as described here https://github.com/ros-controls/gazebo_ros2_control/issues/240. You could use https://control.ros.org/rolling/doc/gazebo_ros2_control/doc/index.html#using-pid-control-joints to overcome this issue.

HPCLOL commented 3 months ago

I guess this is the same result as described here #240. You could use https://control.ros.org/rolling/doc/gazebo_ros2_control/doc/index.html#using-pid-control-joints to overcome this issue.

Thank you so much, it works when I replace the command interface of original joints with pid-control-joints!

But I have a suggestion, the command_interface name for pid-control-joints should be "position_pid" but "position_PID" in https://control.ros.org/rolling/doc/gazebo_ros2_control/doc/index.html#using-pid-control-joints.

Actually, I noticed this webpage earlier and tried to use the pid-control-joints, but the controller did not activate successfully because the command interface name was incorrect. I didn't pay attention to this at the time and gave up trying to use it.

Thank you again！

christophfroehlich commented 3 months ago

But I have a suggestion, the command_interface name for pid-control-joints should be "position_pid" but "position_PID" in https://control.ros.org/rolling/doc/gazebo_ros2_control/doc/index.html#using-pid-control-joints.

I see, thanks for reporting. Do you mind submitting a PR to fix the docs?

HPCLOL commented 3 months ago

Do you mind submitting a PR to fix the docs?

Ok, I will submit a PR later.