Relative impedance-based internal force control for bimanual robot teleoperation with varying time delay

For a bimanual robot teleoperation system, the internal forces affecting the common deformable manipulation object are determined by both robot arms' actions. F/T sensorless, uncertain dynamics, and varying time delays increase dramatically the control difficulty for system stability and transparency. To address these problems, an internal force control method based on relative impedance is proposed in this paper. First, we deduce the desired positions to decrease internal force tracking errors and abstract the internal force from the product of the relative distance and impedance. Second, two strategies are adopted for reducing internal force tracking errors and motion synchronization. One is designing an adaptive factor to switch authorities for position control and internal force control. The other is proposing a force estimating method to the coupled item of uncertain dynamics, disturbance, and internal forces. Different parts of the coupled item are divided and solved separately by nonlinear characters. An integral sliding surface based on the relative impedance item is designed to minimize the force tracking errors. Finally, the effectiveness of the method is verified by linear matrix inequalities based on Lyapunov-Krasovskii functional synthesis, and an experiment based on a physical robot system is implemented to validate the proposed method.