Controlled pin insertion using airflow sensing and active feedback

Abstract

An automatic assembly apparatus or robot holds a pin in an instrumented gripper, moves open loop to the 'detection region' in which airflow forces, primarily lateral forces, in the vicinity of the hole may be dependably sensed. Relatively large lateral airflow forces in the detection region are sensed and the pin is moved toward the hole. The airflow forces exhibit an abrupt force change as the pin reaches the insertion point within the 'capture region' of the hole defined by the mechanical chamfer or significantly extended as a result of the virtual chamfer of airflow through the hole. The insertion point is the point where lateral X,Y force vectors balance to a null, where Z force readings change from complex X,Y,Z force vectors to simple Z force vectors. The controller commands an open loop move to place the pin within the detection region; then commands a closed loop move, using a skirt around the pin or the pin itself as a probe, and sampling the force vectors until the insertion point is detected; then commands a move in the Z direction to put the pin into the hole. Insertion success or failure is detected by sampling the Z force vectors for blockage by the plate, or by sampling pressure as the pin plugs the hole. Retry routines follow detection of any insertion failure.