API review

Proposer: Sachin

Present at review:

• Eric
• Matei
• Kaijen
• Gil
• Tully

Question / concerns / comments

Sachin

• Please review the messages in the API specification. The documentation is within the messages themselves. There are still questions regarding supporting multi-dof joints within this api.
• The specification of orientation constraints will also be significantly simplified by taking out the constraint_region_pose specification and leaving in only the constraint_region_shape specification which will serve as a tolerance/constraint region centered at the goal orientation specified in the message.

• The service GetDynamicMotionPlan will be removed

• Two additional messages that have not been auto-updated yet are also up for review: [motion_planning_msgs/CollisionOperation]

string COLLISION_SET_ALL="all"
uint8 DISABLE=0
uint8 ENABLE=1
string object1
string object2
uint8 operation

and [motion_planning_msgs/OrderedCollisionOperations]

motion_planning_msgs/CollisionOperation[] collision_operations

• Also review GetIKWithCollision and IKRequest (contains robot_state)

• All uint8 that should be bools will be converted to bools.

• New proposal for SplineTraj and SplineTrajSegment

  • Rename to SplineTrajectory and SplineTrajectorySegment

  •   SplineTrajectory:
       Header header
       SplineTrajectorySegment[] segments
       string[] joint_names
      SplineTrajectorySegment:
       Spline[] splines
       Duration duration
      Spline:
        float64[] coefficients

Matei

• JointPath

  • very similar to trajectory_msgs/JointTrajectory (which also contains velocities and accelerations)
  • what is the header used for?

• JointState

  • it seems that by convention all messages here refer strictly to joint positions
    • is this OK? Is it possible that a motion planner might want to deal with velocities / accelerations as well?

    • if they remain like this, rename so that it is clear that they only refer to positions. The fact that they reside in motion_planning_msgs (as opposed to kinematic_msgs for example) obscures that. E.g. JointState -> JointPositionState

• RobotState

  • just listing here the much-discussed problem of the default value for the robot state.
  • how does one specify "use the current state of the robot"?

• JointConstraint

  • worried about the weight, which I think defaults to 0. If all weights are 0 is this handled graciously, or must the caller always set some reasonable weights?

  • should there be a JointConstraint with no weights, and then a WeightedJointConstraint message?

• PositionConstraint

  • change field comment inside message file: "# The desired pose of the robot link" -> "The desired position of the robot link"

  • how do we specify "I want the link above this plane" (e.g. the table)?

• OrientationConstraint

  • the "shape" of a constraint in {yaw, pitch, roll} space is a difficult concept, but we've discussed this before at length and might not have a better alternative

• SimplePoseConstraint

  • what makes it "simple"?

  • why is it not a combination of a PositionConstraint and an OrientationConstraint?

  • what does tolerance specified as x,y,z mean for an orientation specified as a quaternion?

• CollisionOperation

  • specifying "ALL" as a particular string inside of "objectx" is not ideal (even if the string is defined inside the message). Alternative would be adding two boolean flags, object1_all and object2_all

• AcceptableContact

  • is this superseded to some degree by the new mechanism for enabling / disabling collisions?

• FilterTrajectoryService

  • not documented

Meeting agenda

To be filled out by proposer based on comments gathered during API review period

• Review in the following order

  • JointPath, JointPathPoint are derivatives of JointTrajectory

  • JointLimits

  • JointTrajectoryWithLimits

  • JointState, PoseState, RobotState

  • IKService -> should this have RobotState

  • JointConstraint, PositionConstraint, OrientationConstraint, SimplePoseConstraint

  • Constraints

  • CollisionOperation, OrderedCollisionOperation

  • IKWithCollisionService

  • SplineTraj, SplineTrajSegment

  • DisplayPath

  • WorkspaceParameters

  • AcceptableContact

  • ConstraintErrors

  • ConvertToJointConstraint

  • FilterTrajectory

  • GetMotionPlan

• Ideas for robot state

  • JointState

  • PoseState

    • frame_id:
    • child_frame_id:
    • x: bool
    • y: bool
    • z: bool
    • rotx: bool
    • roty: bool
    • rotz: bool

  • RobotTrajectory

    • JointTrajectoryPoint[] points

    • PoseTrajectory[] poses

Conclusion

Package status change mark change manifest)

• Action items that need to be taken.

• Major issues that need to be resolved

• Remove JointPath and instead use JointTrajectory everywhere.

• Get rid of wraparound field in JointLimits, JointTrajectoryWithLimits is fine.

• Use sensor_msgs/JointState, ask for field accelerations in there.

• Add MultiDOFJointStates

  • :string frame_id :string child_frame_id :string joint_name - use groups to resolve this to "base_x_joint", etc. :Pose

• Take out header from joint state message

• Robot state should contain arrays of joint states and pose states

• IK Request should contain robot state + ik link names

• Joint constraints - take out header

• Position constraints - take out position, add offset from link

• Orientation constraints - 3 special cases, (a) fixed, (b) 1-dof around a world fixed axis (b) 1 dof around a gripper fixed axis, tolerances, quaternion, type, axis.

• IKService - add robot state, IKWithCollisionService is ok

• Acceptable contacts - specify as region names and then specify ordered collision operations on them

• Take out pose state

• Try not to use uint8 anywhere

• GetMotionPlan service

  • Add ordered collision operations to it
  • Change acceptable contacts to be just named regions

  • Must return RobotTrajectory and RobotState

  • Return enum error code
  • remove errors
  • Add penetration depth information to ordered collisions

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