Enhanced time delayed linear bilateral teleoperation system by external force estimation

Abstract

One of the prevalent methods in linear bilateral teleoperation systems with communication channel time delays is using position and velocity signals in the control scheme. Utilization of force signals in such controllers improves the performance significantly and reduces the tracking error. Measuring force signals in such cases is one of the major problems. In this paper, a control scheme in the presence of human and environment force signals for the linear bilateral teleoperation is proposed. Due to elimination of measuring forces in the control scheme, a force estimation approach based on disturbance observers has been utilized. The proposed approach guarantees asymptotic estimation of constant forces. The estimation error would only be bounded for time varying external forces. To cope with the variation of the human and environment force, a sliding-mode-controller is used. The stability and transparency condition in the teleoperation system with the designed control scheme is derived from absolute stability concept. The designed control scheme guarantees the stability of the teleoperation system in the presence of time varying human and environment forces. Experimental results show that the proposed control scheme improves position tracking in the free motion and in contact with the environment. In addition, the force estimation approach appropriately estimates human and environment forces.