Two main methods:
- Tilt insertion
- Given a hole pose, the part is held vertically above the hole by a preset distance
- the gripper is then tilted about its local y-axis
- this offset places the lowest part of the bottom edge of the part directly above the estimated center of the hole.
- Translate downwards in the global frame until the part makes contact with the hole, reconfiguring as you go
- Spiral insertion
- Given a shaft end pose, the grasped part is held vertically above the shaft by a preset distance
- the hand then moves down along the axis of insertion until a reaction force threshold is reached
- the robot then preforms a spiraling motion defined in polar coordinates with its origin at the point of contact; it continues until either
- the gripper pose exceeds a threshold below which the intended hole pose cannot lie
- lateral torques at the wrist exceed a threshold indicating the gear has slid onto the shaft and cannot translate laterally
- Once the threshold is met, the hands push down until the z-component of the hands final pose is near the expected value, and the assembly is considered a success