Difference between effort_controllers/JointVelocityController and velocity_controllers/JointVelocityController?

asked 2022-04-24 06:31:55 -0500

kevin.kuei.0321@gmail.com
159 ●14 ●18 ●26

updated 2022-04-24 06:33:08 -0500

Hi,

I wonder to know the difference between effort_controllers/JointVelocityController and velocity_controllers/JointVelocityController.

It looks like most examples of wheeled robot are using effort_controllers/JointVelocityController, though.

answered 2022-04-24 08:36:14 -0500

Mike Scheutzow
4918 ●2 ●430 ●45

The type of command you send to a Motor Controller differs between models. Some are designed to take a target position, others a target velocity, and still others a target torque (i.e. "effort").

So the difference between the effort_controllers and velocity_controllers is the type of command that the ros_control stack sends down to the hardware_interface::RobotHW layer. Typically the value is then passed directly to the motor controller, so the cmd type must match what the motor controller is expecting.

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Thanks for the reply. But, both the two controllers take target velocity. What is the difference? In Effort_controller/JointVelocityComtroller, I can imagine that it takes velocity as input, compare the velocity error, and generate proper effort to make the velocity error minimize. But what about the Velocity_controller/JointVelocityController? Is it really possible to control velocity by velocity itself in physics?

kevin.kuei.0321@gmail.com ( 2022-04-24 19:32:53 -0500 )edit

The Effort_controller/JointVelocityComtroller outputs effort (torque) commands to the hardware interface. the Velocity_controller/JointVelocityController outputs velocity commands to the hardware interface. Both controllers take jointVelocity as input.