Effect of Scaling on the Performance and Stability of Teleoperation Systems Interacting with Soft Environments

There is generally a tradeoff between stability and performance in haptic control systems. Teleoperation systems with haptic feedback are no exception. Scaling in these systems used in applications such as telemicrosurgical systems has further effects on the stability and performance. This paper focuses on those applications interacting with soft tissues and analyzes the effects of the scaling in an effort to increase the performance of these systems while maintaining the stability. Position tracking and kinesthetic perception are especially important in the tele-surgical systems and, hence, are used as the performance criteria. Quantitatively defined stability robustness, which is based on Llewellyn's absolute stability criterion, is used as a metric for stability analysis. Various choices of scaling factors, and human and environment impedances are then investigated. The proposed kinesthetic perception concept is validated using psychophysical experiments. Widely used bilateral control architectures such as the two-channel position-position, two-channel force-position and four-channel controls are specifically analyzed and evaluated using simulations and experiments with phantom soft tissues. Results also show that the force-position control architecture shows the best position tracking performance irrespective of the scaling factors while the four-channel controller shows the best kinesthetic perception capability