Workspace Force/Acceleration Disturbance Observer for Precise and Safe Motion Control

The use of impedance control has become widespread in applications requiring simultaneous position tracking and compliance in contact. However, disturbances such as friction and model uncertainties can adversely affect the performance of impedance-based motion control. The disturbance observer (DOB) has been proposed to address this issue, which is a widely-utilized robust controller that eliminates observed disturbances with the nominal model. However, current DOB applications fail to consider the aspect of interactive force control properly. This study proposes a novel Workspace Force/Acceleration Disturbance Observer (WFADOB) controller, which utilizes both interaction force and acceleration to design a disturbance observer loop, enabling precise motion tracking even with low-impedance gain settings. Additionally, the proposed controller offers fine impedance rendering performance, offering safe contact while maintaining low impedance. This paper discusses the problem of motion tracking performance due to friction and the interaction force that arises during contact. The proposed controller is theoretically analyzed and experimentally verified, demonstrating its performance compared to conventional methods.