Robust control of teleoperation systems interacting with viscoelastic soft tissues

Abstract

This dissertation presents a control scheme for the optimization of robust tracking performance and transparency, while guaranteeing robust stability of teleoperation systems interacting with viscoelastic soft tissues. Surgical teleoperation systems have many advantages and the demand is continually increasing. However, there are problems such as nonlinear characteristics of the interaction between the slave robot and the soft tissues, and difficulty in deploying force sensors at the surgical end-effector. This makes it difficult to have a comprehensive and systematic approach to design of the bilateral control of the surgical teleoperation. The main objective of the developed control scheme is to maximize tracking performance and transparency in teleoperation system interacting with soft tissue such as telesurgical system. The environment, i.e., viscoelastic soft tissues, is characterized with the nonlinear Hunt-Crossley model. Because the soft tissue behaves differently from hard objects in constrained motions, previous research on control of teleoperation systems focused on position tracking in the free motion, and force tracking in the constrained motion does not hold. To propose robust control approach in telesurgical systems, the teleoperation system is modeled as a quasi-linear parameter varying (QLPV) system. For time delay in communication channel is also modeled linear parameter varying way using Pade approximations. To optimize the robust performance while guaranteeing robust stability, a gain-scheduling control scheme is adapted to develop a performance-optimized control of the QLPV system. The performance indices are rigorously analyzed. The optimized control design is provided to the operator with an easy selection of performance indices and frequency dependent filters. To avoid time delay approximation model, gain-scheduling control for delayed system is investigated. For a linear parameter varying system which has a delayed measurement, th...