Bilateral control with compliant force lock for safety enhancement

This paper proposes a force feedback compliance force lock for biltateral control based on sensor-less sensor Reaction Force Observer (RFOB). The force limit is defined by the operator in advance based on the experience. The force lock protects the object which is in contact with the slave actuator from excessive force imposed by the master operator in bilateral control. A small vibration has been introduced to notify the attainment of the force limit to the master operator. Furthermore, if master operator wishes to increase his applied force, he will experience spring effect. The equilibrium point of virtual spring controller which is continuously copied from the slave force locked position aligns master and slave positions at force lock mode. The loss of reaction force occurs at the transition from bilateral control to force lock and vice versa has been removed to regain system stability and to facilitate comfortable operation for the operator. Releasing logic of force lock can be determined by the operator. The proposed system is validated with experiments and results prove the concept of RFOB based force feedback compliance force lock for bilateral control.