Compensation of backlash for improving the efficiency of flexible actuator in bilateral teleoperation system

Teleoperation systems provide human with the ability to interact unknown environment from a remote side which may be dangerous, hazardous, or difficult to access. This paper addresses the development of a bilateral controller for improving the efficiency of a flexible actuator. Based on various identification results from the different bending angles of thrust wire, the system model for a flexible actuator is established and formulated as a one-mass system with variable backlash and friction. When the thrust wire bends in the different angles, the dead-zone backlash characteristics are varied due to the contact surface between the inner wire and outer tube. Therefore it is not quite possible to compensate this non-linearity effects in a real-time. To overcome the inherent problem of backlash and vibration in the thrust wire, the load-side encoder is mounted to measure the end-effector movement. The information transformation technique called, a modal space design is proposed to achieve the targets of bilateral control and suppress this non-linearity effect of backlash. By using the proposed method, it is not necessary to estimate backlash parameters. This algorithm is verified through the identification and experimental results of master and slave robots with thrust wire.