Physical Human–Robot Interaction Based on Adaptive Impedance Control for Robotic-Assisted Total Hip Arthroplasty

The performance of human–robot interaction can be enhanced by imposing force constraints through virtual fixture (VF) algorithms. In this article, an adaptive impedance-based VF scheme is proposed, aiming to improve the accuracy of human–robot interaction in robot-assisted total hip arthroplasty (RA-THA). We developed a multimode impedance controller that realizes four distinct functional modes according to boundary divisions of the VF: free dragging, position constraints, restriction, and restoration of manipulability. A variable impedance control algorithm that adaptively adjusts the damping, stiffness, and force limitations is proposed to achieve precise stopping of the robot at the VF boundary. The stability of the closed-loop system is proved via Lyapunov theory. Experimental results demonstrate that the controller delivers precise, smooth, and stable VF constraints, even at varying velocities and in complex force interactions. The VF constraints are accurate within 1 mm, effectively improving the accuracy of human–robot interaction in RA-THA.