Synchronous Control of 2-D.O.F Master-Slave Manipulators Using Actuators With Asymmetric Nonlinear Dead-Zone Characteristics

Although the various synchronous control techniques of a master-slave manipulator have been explored and developed over the decades, the investigations of the synchronous control for those systems with strong asymmetric dead-zone characteristics have been limited and not been fully considered. Hence, we proposed the robust and easy-to-implement estimation and control strategy to compensate for the actuator’s dead-zone effect and to guarantee synchronous performance. Specifically, we set up a two-step process called prior-estimation control to avoid the performance degradation due to the frequent failures of the desired estimation in a standard adaptive control. The first step is to adaptively estimate the asymmetric nonlinear dead-zone parameters via the Recursive Least Square (RLS) method. At the second stage, those estimated parameters via RLS are delivered to the main synchronous control system designed by a passivity-based sliding mode control technique along with inverse dead-zone control, and then the control is executed whenever a human operator interacts with the system. Finally, the effectiveness of the proposed approach has been validated by the actual 2-D.O.F master-slave manipulators equipped with cost-effective actuators with an inevitable asymmetric dead-zone. This work will be especially a valuable asset for those who wish to accurately control the master-slave systems with dead-zone characteristics such as the industrial construction multiple joints based fork cranes or lifts.