A model-based robust control approach for bilateral teleoperation systems

In this project we aim to design controllers that provide high fidelity force feedback for bilateral teleoperation systems in order to provide a feeling of tele-presence. New methodologies based on switching and robust control are proposed to tackle the performance-stability trade-off.

PhD Candidate: César A. López Martínez
Supervisor: René van de Molengraft
Promoter: Maarten Steinbuch
Project Financing: PITON project
Project Period: September 2010 - September 2014

Bilateral teleoperation systems allow an operator to manipulate a remote environment by means of a master and a slave device while using force feedback to obtain a feeling of tele-presence. There is an inherent trade-off between stability and performance, and it is a challenging problem to design controllers that meet an appropriate balance.

This thesis adopts a model-based robust control design approach.  We propose and validate different controller designs. First, we synthesize a single controller for a bounded range of stiffness variation. Next, to improve performance we propose a multi-controller structure, in which we design multiple robust controllers for different regions of environment stiffness, which controllers are scheduled on the basis of an estimate of the environment stiffness. 

We design three variations of such structure, in the first one, all the controllers are designed to share a common lyapunov function to guarantee smooth switching between them. In the second we use dwell time conditions during the controller synthesis . In the third one, we synthesize multiple performance-optimized controllers independently and switching between them is based on an adapted version of the bumpless transfer technique. The last multi-controller structure is implemented on a real-life surgical robot named Sofie.