Planning Held Object Motion

planning-held-object-motion

Turn a feature mate into safe phases for a held object:

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lift away from support
  -> rotate minimally in clear space
  -> translate above the fixture with orientation fixed
  -> approach and engage linearly

The skill plans; it does not move the robot or release the object. Follow it with executing-held-object-motion to execute the carry plan and executing-feature-mating to execute the engagement plan.

Choosing the carry strategy

plan_clearance_motion takes strategy:

• "clearance_first" (default) derives a lift from the farthest attached sphere, selects the smallest reachable symmetry-equivalent rotation among eight roll candidates (each checked with motion.plan_joint), rotates while clear, and translates the aligned feature to a staging location on the free side of the fixture, approach_clearance_m along its axis. The staging location is derived from the fixture geometry and attached-object extent. stage_outward_m (default 0) shifts that location within the support plane away from the fixture toward the current hand — use it when a recessed opening is observed mostly at its far rim and the object should stage over the interior instead.
• "direct" escapes escape_m (default 6 cm) along the support normal as a contact_transition waypoint, then hands approach_pose to the executor as one planned_joint waypoint with allow_start_contact and three attempts. It calls no planner itself. Use it when the object is already clear of its support, the orientation change is small, and a single attached-object plan to the approach pose is appropriate; it requires approach_pose.

If uncertain, choose the clearance-first strategy for a large orientation change or a long held object. Do not add arbitrary midpoint waypoints and do not remove collision geometry to make direct planning succeed.

Engagement

plan_feature_engagement converts the typed relation and the approach, engaged, and mate poses into execution semantics. loop_over_shaft crosses the shaft tip with a tracked cartesian_cross leg — stopping on first contact can leave a loop balanced against the tip without enclosing the shaft — and then seats with the bounded contact_seat servo; feature_to_fixture uses the contact servo for both legs; aperture insertion uses planned_linear waypoints that allow goal contact. The task graph therefore does not decide ad hoc whether a contact servo is needed.

plan_linear_engagement plans a straight insertion from the fixture feature alone: a planned_joint pre-contact pose precontact_clearance_m before the opening and a planned_linear engaged pose engagement_depth_m past it, both holding the current orientation. Give it observation (the current Observation), object_description and direction_marker_description to re-observe the held tip from the wrist first: when both the object and its direction marker are visible, the endpoint of the object's principal axis toward the marker replaces the carried feature position.

Recommended skill sequence

1. Use registering-held-objects to obtain held_feature_in_tcp and attached_object.
2. Use computing-feature-mating-poses when explicit approach/engaged/mate poses are needed.
3. Select the carry strategy using the criteria above.
4. Execute the returned reorientation_plan with executing-held-object-motion.
5. Execute placement_plan with executing-feature-mating.

Waypoint modes are semantic: contact_transition leaves the initial support, planned_joint is collision-aware free-space motion, planned_linear locks orientation for a straight local leg, cartesian_cross is a tracked short crossing, and contact_seat is the final intentional-contact servo.

Boundaries

• Upstream perception supplies the held feature in TCP coordinates and the fixture pose/axis. Registration supplies attached-object collision geometry.
• Inputs describe functional geometry and a relation rather than an object class or task name; the graph chooses strategy, stage_outward_m and the re-observation descriptions.
• Free roll about the fixture axis is treated as symmetry. Candidates are checked for reachability and the smallest feasible TCP rotation is selected.
• support_normal may be supplied when the escape direction is known; it defaults to world up for a horizontal support surface.
• Relationship-specific clearances may be supplied by the graph when fixture depth is observable or specified. Conservative geometric defaults are used otherwise.
• The final crossing is linear and may allow goal contact. All earlier motion remains collision-aware free-space motion.