Robust and Transparent Multi-Degree-of-Freedom Bilateral Teleoperation with Time-Delay

Abstract

Robots are particularly well suited for executing tasks that take place in locations which are too dangerous or inaccessible to human operators. For robot manipulators to execute complex activities in unknown, unstructured environments, despite the recent increases in computation power, human input is still required for task planning and execution. Most of the existing bilateral teleoperation systems, which make use of commercially available master devices to control industrial slave manipulators, show three main limitations: instability on contact with stiff environments, reduced force-feedback performance to the operator and limited master workspaces. It is the main goal of the research presented in this thesis to achieve high transparency and time-delay robustness in bilateral teleoperation using dissimilar multi-dof master-slave devices, in particular making use of impedance-type masters to command impedance-controlled slave manipulators. This research focuses on tasks which a human operator could manually execute if physically present in the remote environment. This implies that there should be no force scaling and the motion remains within the limits of the human operator arm. It is also assumed that a high level of transparency should be provided to the operator to enable the execution of the required tasks in teleoperation. Currently, modern communication devices and the Internet allow connections throughout the world with round-trip communication delays in the range of hundreds of milliseconds. Throughout this work, communication delay values smaller or equal to 250 ms, for which direct bilateral teleoperation is the most usable, are considered. Under these premises, the research approach followed on this thesis is divided in three main parts. These parts are: (1) Effect of different parameters on system stability and performance for a system with impedance-type master commanding an impedance-controlled slave (2) Robust stability methods for 4-channel architecture under time-delay (3) Propose hardware/software architectures for multi-dof teleoperation