Robust Control of Collaborative Dual-User Haptic Training System: An Autonomous Variable Impedance Scheme

Lack of adequate skills are the most prominent contributor to the persistent problem of surgical errors throughout the early phases of a novice surgeon's training. Therefore, it is essential to thoughtfully and methodically consider the development of an effective strategy for transferring the trainers' expertise to novice surgeons, while simultaneously increasing the trainers' involvement in the training process. This article proposes a collaborative dual-user haptic-enabled surgical training system that utilizes a responsive variable impedance control structure. In this training system, a novice (trainee) and an expert (trainer) collaboratively conduct a particular task through their respective haptic devices. The desired parameters of the impedance model for the trainer's haptic device remain constant throughout the operation, while those of the trainee's haptic device are time-varying depending on his/her relative task performance level. The main purpose of this performance-based variable impedance control structure is to imitate or enhance the hands-on training experience. High-gain observers with unknown input are considered to estimate the interaction forces. The small-gain theorem and the input-to-state stability method are utilized to examine the overall nonlinear closed-loop system stability. Experiments are conducted to demonstrate the effectiveness of the proposed training system.