Adaptive Nonlinear Friction Compensation for Pneumatically Driven Follower in Force-Projecting Bilateral Control

Force-projecting bilateral control is an effective method for enhancing the positioning rigidity and stability of teleoperation systems equipped with compliant pneumatically driven followers. However, friction in the pneumatic actuation mechanism has caused a deterioration in force reproducibility between the leader and follower. To solve this problem, this study proposes a practical method of nonlinear friction compensation in force-projecting bilateral control to improve the force reproducibility. The proposed method generates two friction compensation forces: one based on the target admittance velocity from the leader and the other based on the actual velocity of the follower. These forces are seamlessly switched according to the dynamic state of the system to compensate for the follower’s driving force. This enables improved force reproducibility in any motion states of the system while maintaining the advantage of force-projecting bilateral control, which eliminates the need for external force measurement on the follower side. Experiments were conducted using a 1-DOF bilateral control device consisting of an electric linear motor and a pneumatic cylinder, including free motion and contact operations with two types of environments, demonstrating the effectiveness of the proposed method.