Enhancing free-space transparency with discrete energy-based compensation in physical human–robot interaction

In physical human–robot interaction (pHRi), free-space transparency reflects how accurately a robot interprets and follows human motion intentions. This paper presents a novel discrete energy-based compensator designed to enhance transparency by leveraging an admittance controller that requires real-time input compensation. Transparency, defined as the work performed by interaction forces per unit distance, is improved by analyzing human dynamics to minimize interaction forces linked to transparency. The proposed compensator incorporates time delay control to compute necessary real-time compensation based on interactions between human and robot dynamics represented by admittance parameters. The method was validated through simulations and experiments on a physical robot system, demonstrating its effectiveness in enhancing transparency while addressing practical limitations. This study emphasizes the importance of dynamic analysis in pHRi and proposes a cost-effective approach to compensate for both interaction and robot dynamics.