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Cartesian Twist Controller

Overview

The Cartesian Twist Controller commands a desired twist to a chain of joints. The chain of joints is a set of joints that spans from some link (the "root" link) to another link (the "tip" link). The twists are applied at the origin of the tip link in the frame of the root link, and are controlled by PID controllers. Translational and rotational gains are set separately.

ROS API

Subscribed Topics

command (geometry_msgs/Twist)

• The twist to command

Parameters

root_name (string, default: Required)

• The root link of the chain of joints

tip_name (string, default: Required)

• The tip link of the chain of joints

fb_trans/p (double, default: Required)

• Translational gain, relating force to velocity error

fb_trans/d (double, default: 0.0)

• Translational derivative gain

fb_trans/i (double, default: 0.0)

• Translational integral gain

fb_trans/i_clamp (double, default: 0.0)

• Bounds enforced on the translational integral windup

fb_rot/p (double, default: Required)

• Rotational gain, relating end-effector torques to angular velocity error

fb_rot/d (double, default: 0.0)

• Rotational derivative gain

fb_rot/i (double, default: 0.0)

• Rotational integral gain

fb_rot/i_clamp (double, default: 0.0)

• Bounds enforced on the rotational integral windup

Example configuration

r_arm_cartesian_twist_controller:
  type: CartesianTwistController
  root_name: torso_lift_link
  tip_name: r_wrist_roll_link
  fb_trans:
    p: 20.0
    i: 0.5
    d: 0.0
    i_clamp: 1.0
  fb_rot:
    p: 0.5
    i: 0.1
    d: 0.0
    i_clamp: 0.2