An Observer-Based Responsive Variable Impedance Control For Dual-User Haptic Training System

This paper proposes a variable impedance control architecture to facilitate eye surgery training in a dual-user haptic system. In this system, an expert surgeon (the trainer) and a novice surgeon (the trainee) collaboratively conduct a surgical task through their own haptic devices, while the trainee’s haptic device is connected directly to the real or virtual environment. The haptic interaction between the two surgeons is established through the haptic system. The mechanical impedance parameters of the trainer’s haptic device remain constant during the operation, while those of the trainee’s haptic device is set to be time-varying depending on his/her relative proficiency level. The trainee’s relative proficiency could be objectively quantified in real-time using the position error between the trainer and the trainee as captured by their haptic devices. The proposed controller enables the trainer to intervene in the training process as needed to ensure the trainee is following the right course of action and to reduce the trainee’s authority level to avoid potential tissue injuries. The stability of the overall nonlinear closed-loop system has been investigated using the input-to-state stability (ISS) criterion. High-gain observers with unknown inputs are considered in this work to estimate the interaction forces. Simulation and experimental results under different scenarios confirm the improvement provided by the proposed controller over traditional methods.