Bilateral Control - Operational enhancements

Official URL: http://risc01.sabanciuniv.edu/record=b1160385 (Table of Contents)

A succinct definition of the word bilateral is having two sides [1]. In robotics the term bilateral control is used to define the specific interaction of two systems by means of position and/or force. Bilateral systems are composed of two sides named master and slave side. The aim of such an arrangement is such that position command dictated by master side is followed by a slave side, and at the same time the force sensation of the remote environment experienced by slave is transferred to the mater - human operator. This way bilateral system may be perceived as an “impendanceless” extension of the human operator providing the touch information of the remote (or inaccessible) environment. In a sense bilateral systems are a mechatronics extension of the teleoperated systems. There are many applications of this structure which requires critical manipulations like nuclear material handling, robotic surgery, and micro material handling and assembly. In all these applications a human operator is required to have as close to real as possible contact with object that should be manipulated or in other word the telepresence of the operator is required. In this thesis work various important aspects of bilateral control systems are discussed. These aspects include problems of (i) acquisition of information on master and slave side, (ii) analysis and selection of the proper structure of the control systems to ensure fidelity of the system behavior. The work has been done to enhance the performance of the bilateral control system by: (i) Enhancing position and velocity measurements obtained from incremental encoder having limited number of pulses per revolution. A few algorithms are investigated and their improvements are proposed; (ii) Increasing system robustness by using acceleration controller based on disturbance observer. The robust system design based on disturbance observer is known but its application requires very fast sampling and high bandwidth of the observer. In this work the discrete time realization of the observer is presented in details and selection of the necessary filters and the sampling so to achieve a good trade-off for observer realization is discussed and experimentally confirmed; (iii) Increasing the bandwidth of force sensation by using reaction force observer. For transparent operation of a bilateral system the bandwidth of force sensation is of the major interest. All force sensors do have relatively slow dynamics and observer based structures seems providing better behavior of the overall system. In this work the observer of the interaction force is examined and design procedure is established. In order to verify all of the proposed ideas a versatile bilateral system is designed and built and experimental verification is carried out on this system.