Bilateral Control Architectures for Telerobotics

This chapter introduces and surveys bilateral (master-slave) control methods and system architectures for telerobotics known in the literature. The discussion takes a focus most relevant to subsequent chapters, see [1–3] for complementary and more complete surveys. Firstly, an introductory example of a control-oriented block diagram formulation for a typical two-channel force-velocity architecture is presented, where the human system interface (master) is force controlled and the teleoperator (slave) is velocity controlled. Then a network theoretic view using n-ports is taken and the basic concept of passivity is explained meaning that an interconnection of passive subsystems results in an overall passive system. Transparency is defined, meaning that the human operator should ideally feel as if directly acting in the remote environment (is not able to feel the technical systems/communication network at all). The well known and for ideal transparency required four-channel architecture is presented. The important discussion of time delay in the communication network, which impairs or might threaten stability properties of the closed loop teleoperation system, is then discussed. The most successful approach using the scattering (wave variable) transformation approach is presented, which guarantees that the communication two-port is lossless (passive) for arbitrary constant time delay. Finally, we mention the key challenges in the design of bilateral teleoperation systems and give a short preview of the subsequent chapters addressing some of these challenges.