JT Cartesian Controller


The JT Cartesian Controller controls the pose of the end effector using a Jacobian-transpose based controller, with redundancy control.

It's loosely based off the acceleration control scheme in Nakanishi, Comparative Experiements on Task Space Control, with a diagonal approximation of the mass matrix, and the Jacobian derivatives set to zero. These simplifications have worked well in practice when controlling the PR2.



root_name (string, default: Required)
  • The root link of the chain to control.
tip_name (string, default: Required)
  • The tip link (end effector) of the chain to control.
cart_gain/trans/p (double, default: Required)
  • Proportional gain for translation of the end effector.
cart_gains/trans/d (double, default: Required)
  • Derivative gain for translation of the end effector
cart_gains/rot/p (double, default: Required)
  • Proportional gain for rotation of the end effector
cart_gains/rot/d (double, default: Required)
  • Derivative gain for rotation of the end effector
vel_saturation_trans (double, default: 0.0)
  • Velocity limit for translation (m/s). Zero means not limited.
vel_saturation_rot (double, default: 0.0)
  • Velocity limit for rotation (rad/s). Zero means not limited.
jacobian_inverse_damping (double, default: 0.0)
  • Damping term for taking the inverse of the Jacobian.
joint_feedforward/<joint> (double, default: 0.0)
  • Feedforward term for the posture controller.
saturation/<joint> (double, default: 0.0)
  • Maximum torque for the joint.
k_posture (double, default: 1.0)
  • Gain on the posture control.

Example configuration (from pr2_controller_configuration/pr2_jt_controllers.yaml):

  type: robot_mechanism_controllers/JTCartesianController
  root_name: torso_lift_link
  tip_name: r_gripper_tool_frame
  k_posture: 25.0
  jacobian_inverse_damping: 0.01
  pose_command_filter: 0.01
      p: 800.0
      d: 15.0
      p: 80.0
      d: 1.2
    r_shoulder_pan_joint: 3.33
    r_shoulder_lift_joint: 1.16
    r_upper_arm_roll_joint: 0.1
    r_elbow_flex_joint: 0.25
    r_forearm_roll_joint: 0.133
    r_wrist_flex_joint: 0.0727
    r_wrist_roll_joint: 0.0727
    r_shoulder_pan_joint: 11.88
    r_shoulder_lift_joint: 11.64
    r_upper_arm_roll_joint: 6.143
    r_elbow_flex_joint: 6.804
    r_forearm_roll_joint: 8.376
    r_wrist_flex_joint: 5.568
    r_wrist_roll_joint: 5.568

  vel_saturation_trans: 2.0
  vel_saturation_rot: 4.0

Published Topics

state (robot_mechanism_controllers/JTCartesianControllerState)
  • Current state of the controller
state/x_desi (geometry_msgs/PoseStamped)
  • Current setpoint of the controller

Subscribed Topics

command_pose (geometry_msgs/PoseStamped)
  • Tells the controller where to go.
gains (std_msgs/Float64MultiArray)
  • New gains. 6 values replaces all the Kp terms (trans, trans, trans, rot, rot, rot). 12 Replaces the Kp and Kd terms.
command_posture (std_msgs/Float64MultiArray)
  • New desired joint posture. Should have the same size as the number of joints being controlled.

Wiki: robot_mechanism_controllers/JTCartesian Controller (last edited 2013-02-17 13:21:06 by Boris)