Compensation of backlash for geared drive systems and thrust wires used in teleoperation

This paper presents a unique method to cancel the backlash present in geared drive systems and thrust-wire systems. Large-sized robots need larger actuators with a high inertia to obtain the desired amount of torque. However, the use of large actuators will increase the effect of gravity. To compensate for the gravitational effect, motors with a high torque are again necessary. Therefore, geared drive systems are used to obtain higher torques and decrease the actuator size. However, adding gears will create a backlash problem. Moreover, when it is necessary to make lighter robots, thrust wires can be used to transmit the motion from the motor to the end effector while keeping them separated. However, the mechanical backlash inside the thrust wire is again a matter of concern. If geared systems and thrust-wire systems are used for the transmission of haptic information in bilaterally controlled systems, the backlash will greatly deteriorate the performance of the system and necessitate compensation. Therefore, a novel method is proposed to uniquely cancel the backlash in the gears and thrust wires used in bilateral teleoperation with twist control. This method uses two identical counter-operating drives per joint to compensate for the backlash effect with a unique control structure that can be used in both geared systems and thrust-wire systems. Experiments have been carried out for the proposed method to validate its accuracy.