Practical Reset Logarithmic Sliding Mode Control for Physical Human–Robot Interaction With Sensorless Behavior Estimation

This article considers the implementation of an observer-based logarithmic control scheme for physical human-robot interaction, which is a typical Lagrangian system. The novelty lies in using a switching term in the logarithmic sliding mode observer to describe the operator's behavior without any sensors, and applying adaptive parameters in the logarithmic sliding mode controller (SMC) to practically stabilize reaching the sliding surface using chattering-free nonsingular reaching law in finite time. A reset mechanism is synthesized into the control system to enhance the transient response. The motion on the sliding surface is analyzed from the perspective of practical finite-time stability, from which both the convergence regions of the tracking and estimate errors can be determined. The numerical and experimental results verify the effectiveness and advantage of the proposed reset logarithmic SMC and observer for human-robot interaction compared to the existing linear SMC and terminal SMC. With regards to settling time and rising time, the superiority of transient performance in experimental results is coincident with the stability analysis.