NOTE: This is a preliminary brainstorming review conducted online
Proposer: Jonathan Bohren
Present at review:
- Jonathan Bohren
Question / concerns / comments
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Determine scope for a message type to capture the semantics of cartesian trajectories and streaming cartesian control in teleoperation.
Potential features include (in no particular order):
- Multiple end-effectors
- Variable impedance (stiffness/damping)
- Path tolerances
- Combinations of joint-space and cartesian-space movements
- Nullspace posture
- Nullspace impedance
The previous formal review notes are here: robot_mechanism_controllers/Reviews/Cartesian Trajectory Proposal API Review
The initial thread on ros-users is here: http://lists.ros.org/lurker/thread/20130605.124118.361c6da3.en.html
Willow Garage (2010)
[CartesianTrajectoryGoal] CartesianTrajectory trajectory Header header # A stamp of 0 means "execute now" PoseStamped tool # The frame which is being controlled string posture_joint_names CartesianTrajectoryPoint points duration time_from_start Pose pose Twist twist float64 posture JointTrajectory posture # For determining the redundancy CartesianTolerance path_tolerance # Tolerance for aborting the path float64 position float64 orientation # Permitted angular error float64 velocity float64 angular_velocity CartesianTolerance goal_tolerance # Tolerance for when reaching the goal is considered successful bool queue
[CartesianTrajectoryResult] int32 error_code # 0 if successful CartesianTrajectoryPoint cartesian_state JointTrajectoryPoint joint_state Twist pose_error Twist twist_error CartesianTolerance path_tolerance # Current tolerance used for the path
[CartesianTrajectoryError] int32 SUCCESSFUL = 0 int32 ROOT_TRANSFORM_FAILED int32 TOOL_TRANSFORM_FAILED int32 PATH_TOLERANCE_VIOLATED int32 INVALID_POSTURE
[CartesianTrajectoryGoal] Header header # A stamp of 0 means "execute now" string effector_names CartesianTrajectory trajectory Pose tool # The frame (offset ?) which is being controlled or it can be treated as separate effector ? CartesianTrajectoryPoint points duration time_from_start Pose pose Twist twist CartesianImpedance impedance Pose center_of_compliance # or it can be treated as separate effector ? TBD stiffness % cartesian stiffness TBD damping % damping ratio CartesianTolerance path_tolerance # Tolerance for aborting the path float64 position float64 orientation # Permitted angular error float64 velocity float64 angular_velocity CartesianTolerance goal_tolerance # Tolerance for when reaching the goal is considered successful string joint_names JointTrajectoryPoint posture # For determining the redundancy JointImpedance nullspace_impedance float64 stiffness float64 damping
Konrad Banachowicz 2
Express trajectory of frame target_frame_id in relation to frame header.frame_id .
Header header # stamp - trajectory start time, frame_id - trajectory reference frame string target_frame_id # target controlled frame CartesianTrajectoryPoint points duration time_from_start Pose pose Twist twist
Parameters of spring-damper located between frame header.frame_id and frame target_frame_id.
Header header # stamp - trajectory start time, frame_id - spring-damper base frame string target_frame_id # spring-damper end frame CartesianImpedancePoint points duration time_from_start CartesianStiffness stiffness Vector3 translational Vector3 rotational CartesianDamping damping Vector3 translational Vector3 rotational
Constraint the relation between header.frame_id and target_frame_id.
Header header # stamp - time of constraint activation string target_frame_id duration time_from_start # duration of constraint activation TranslationConstraint translation OrientationConstraint orientation Twist twist Wrench wrench
[CartesianTrajectoryGoal] CartesianTrajectory trajectory CartesianImpedance impedance CartesianConstraints path_constraints # Tolerance for aborting the path JointTrajectory posture # For determining the redundancy JointImpedance nullspace_impedance
Adolfo Rodriguez Tsouroukdissian
+1 for adding Cartesian accelerations to the CartesianTrajectoryPoint message.
The list of potential features mentions "Multiple end-effectors". I'd like to see how this looks like. We also need to decide where to draw the line, because when controlling multiple end-effectors, you're more likely to also want partial constraint specifications (< 6dof of a frame, like following orientation only), which seems out of the scope of the current proposal.
The concept of multiple end-effectors is included in ActionGoal. We have multiple trajectories (CartesianTrajectory trajectory). It can express trajectories in general, it could be "end-effectors", "tool transforms", "center of complayance", "look at" frame for head ...
In my use-case the constraints are encoded in spatial springs between frames. I don't control position of the end-effector directly but by spatial springs between end-effector and an other frames.
Package status change mark change manifest)
Action items that need to be taken.
Major issues that need to be resolved