PR2 Arm Control

Low-level Controllers

Controller	Joint Spline Trajectory Controller	JTranspose Controller	JTranspose Task Controller	JInverse Controller	End Effector Cartesian Impedance Control
Designer	Stuart Glaser	Stuart Glaser	Adam Leeper	Stuart Glaser	MIT
Control Space	Joint space	Cartesian Space	Cartesian Space	Cartesian Space	Cartesian Space
Control Type	Joint position, velocity, acceleration control with PID	Controls force at the end effector with PD on the Cartesian error	Same as JTranspose, shaped stiffness matrix in end effector's frame	Position or Velocity Cartesian control with PD control on joint velocities	Force-stiffness hybrid control, JTranspose on some DOF, force control on others
Relevant Equations	T = PID(spline(t, trajectory) - q_cur)	T = J^T * PD(x_err) + Kff * J_null * (q_posture - q)	Same but: PD(x_err) = R * Kp * R^T * x_err + R * Kd * R^T * x_dot	T = Kp * (q_proxy - q) + Kd * (q_dot_des - q_dot) q_dot_des = J_pinv * x_dot + J_null * (q_posture - q)	T = J^T * F F = PD(x_err) or F_des
Control Location	Joints	User specified Cartesian pose	User specified Cartesian pose	User specified Cartesian pose	Wrist Cartesian pose
Interfaces	Actionlib Command topic	Command topic	Command topic	Command topic	Actionlib Command topic
Demonstrated Tasks	Planning and manipulation stack Scratch approach ver. 1 Trajectory playback Overhead grasping	Lightswitch Interactive grasping THEP remote control Door opening	Invisible surface		Sweeping with broom Brushing on table Writing with pencil Flipping pages in a book Cutting a cake Door opening (not smoothly)
Specify Trajectory	Yes	No	No	No	Yes
Change Gains on the Fly	No	Yes	Yes	No	Yes, if using impedance control
Integral Control	Yes	No	No	No	No
Cartesian Velocity Saturation	No	Yes	Yes	No, not implemented yet	No
Torque Saturation	No	Yes	Yes	No	No
Notes	Waypoints are smoothly interpolated between using splines. Commands can be sent to the controller to be executed in the future.				Each point in the trajectory is alternatively an impedance vector or a force. The derivative term is not implemented.