Excess Force Reduction in Bilateral Control for Precise and Safe Operation

This paper proposes a constrained bilateral control method to maintain a safe force limit in a remote environment in an event where the operator applies excessive force on the master system. The disturbance observer compensates system disturbances, and the reaction force observer (RFOB) estimates the external force exerted on individual. The paper introduces a force regulator called excess force reduced RFOB (EFR RFOB) to reduce the excessive force applied by the operator to the safe force limit. The amount of excess force is determined by adding the master-side RFOB output and the replica-side safe force limit. Acceleration-based bilateral control is implemented in a virtual space with a master virtual force input, virtual position response, and replica real force-position responses. It realizes transparency in the virtual space. This paper derives the relation between master-side real and virtual space variables to facilitate reproducibility between the master operator and replica environment. The restrained master force-position responses in the virtual space realize precise and safe force control on the replica-side in real space. The proposed method is verified using experiments.