Computing Feature Mating Poses

computing-feature-mating-poses

This skill computes geometry only. When a relation has a free rotational degree of freedom, it selects the equivalent mate closest to the current TCP orientation to avoid arbitrary or unreachable reorientation. Its pre-contact standoff encloses the complete attached-object sphere projection along the fixture axis, preventing long held bodies from sweeping into the fixture.

When to use

• A held loop or ring must be placed over a shaft, peg, or hook.
• A held shaft or tip must enter an aperture.
• The mating pose has rotational symmetry that should be resolved from the current robot pose.

Use loop_over_shaft for a loop or ring placed over a peg or hook. Use shaft_into_aperture for a shaft entering an opening; tip_through_aperture and insert_through are accepted aliases. The skill checks that the relevant inner and outer dimensions have sufficient clearance: for loop_over_shaft the held radius_inner against the fixture radius_outer, for apertures the held radius_outer against the fixture radius_inner.

For loop_over_shaft, describe the fixture at its distal tip with an axis pointing outward from the mounting surface, radius_outer, and the observed usable_length from tip toward the mount. The skill uses these dimensions to center the shaft inside the loop during crossing, travel to a stable interior shaft position, and then seat the loop without requiring an object-specific target point. crossing_lift_m (default 0) raises the approach and engaged poses vertically by that amount after centering, so a long held body that settles in the hand between observation and crossing still clears the tip; the mate pose is unaffected. It applies when usable_length is declared.

For apertures, the fixture axis points into the opening. The approach is mirrored onto the free side of the mate, and insertion_depth (when the fixture declares it) moves the engaged and mate poses that far into the opening.

Outputs

• approach_pose is a collision-free standoff before fixture engagement.
• engaged_pose crosses the distal tip far enough for the loop to surround the shaft, or enters the aperture.
• mate_pose places the loop farther along the usable shaft and seats it, or seats the shaft at the requested depth.
• seating_distance and minimum_clearance describe the computed mate.

Boundaries

• This skill computes poses but does not plan or execute robot motion.
• Inputs describe functional geometry and a typed relation, not object names. Object-specific corrections (a settling offset measured for one tool) enter through crossing_lift_m, supplied by the graph.
• Execute the result with planning-held-object-motion and the corresponding motion-execution skills.