Automatic control of an orthogonal-type robot with a force sensor and a small force input device

In this paper, an automatic control system with a force sensor and a small force input device is presented for an orthogonal-type robot. The automatic control system is composed of a force feedback loop, a position feedback loop and a position feedforward loop. The force feedback loop controls the resultant force consisting of tool contact force and kinetic friction forces. The stability criterion of the force control system is briefly discussed. In addition, the position feedback loop controls the position in only pick feed direction. The position feedforward loop guides the tool tip along a desired trajectory called cutter location data (CL data), in which the feed rate is suitably generated by a fuzzy reasoning according to each model's curvature. Furthermore, a fine stick-slip motion control strategy is added to improve the lapping efficiency. The fine stick-slip motion is orthogonally generated to the direction of tool movement. Finally, a force input device is designed to enable an operator to manually regulate the desired feed rate or the desired polishing force. The force input device allows the robot to realize cooperative motion between the automatic control and the manual control reflecting operator's skill. The effectiveness of robot's performance is examined through experiments.