Improvement of Force Transmission Performance Considering Nonlinear Friction in Bilateral Control Systems

Abstract

This paper presents the results of an experimental evaluation of four-channel bilateral control systems. These systems are based on robust acceleration control, and take nonlinear friction compensation into consideration. Although force estimation by a reaction force observer is one of the key technologies used to achieve precise bilateral control without force sensors, extracting accurate force data using this method proves difficult owing to the requirement of removing disturbances such as friction, gravity, interference force, etc. It is well known that nonlinear friction exhibits a complicated behavior at the micro-displacement region and/or the reversal point of velocity direction. In particular, this characteristic is most obvious in the operability in macro/micro bilateral control with scale conversion between master and slave. This paper presents an improvement to the quality of force estimation by using nonlinear friction modeling and model-based friction compensation in the reaction force observer. The accuracy of force control performance in the four-channel bilateral control system with a reaction force observer is experimentally evaluated by using linear actuator systems with different friction dynamics.