Control System Design for Networked Telerobotic Systems

Abstract

Telerobotic systems are designed to extend the manipulation capability of users at different scales to remote and dangerous environments. In the past decade, the availability of higher computational power, larger variety of commercial haptic devices and faster means of communication at lower costs have facilitated the rapid development of haptic technology and new applications that would require an interconnection of more than one master and slave. Examples of such applications are telementoring of surgical residents and dual-arm tele-manipulation of objects. These networked systems are dynamically involved and are often represented by multi-port networks; as such, the coupled stability analysis and the design of multilateral controllers for these systems pose a great challenge. This thesis proposes new stability analysis tools and control architectures for networked telerobotic systems, modelled by lumped multi-port networks, distributed multi-port networks, and a cascade of two-port networks.

The first methodology deals with extending the Zeheb-Walach absolute stability theorem, originally developed for microwave systems, to robotic systems represented by a lumped network. The extended Zeheb-Walach theorem allows for studying a larger class of networks with marginal stability, such as robotic systems with position feedback. In the second methodology, a distributed framework for the development of a stability-guaranteed telerobotic system with any number of masters and slaves is proposed. The proposed architecture allows for any number of master or slave networks, all connected to a simple sharing protocol that governs the dynamic interaction among them. Modular stability analysis of each master or slave network, regardless of the underlying sharing paradigm, is conducted using the notion of absolute k-stability. In the third approach, Mobius transformation is used to develop a chain-wise stability analysis methodology to verify the coupled stability of a cascade of networks. The proposed methodology tracks the transmitted passivity unit disk of the load through the cascade to the user network and allows for networks in the cascade that are not passive nor absolutely stable. Due to the modularity of this methodology, it is more suitable for dynamic distributed systems in which a network block in the cascade is modified, added or taken out.