Teleoperation is the extension of a person's sensing and manipulation capability to a remote location. A teleoperator can be generally modeled as a linear transfer function inherently including modeling uncertainties. Modeling uncertainties can make the system unstable and its performance poor. Unstructured modeling uncertainties arise from the following sources : linearization of robot dynamics, different operating condition (depending on the configuration of robots), neglected actuator dynamics, and nonlinear characteristics of environment impedance, and so on. In Chapter 2, we design robust bilateral controllers using μ-synthesis framework that achieve stability and performance in the presence of unstructured modeling uncertainties.
Many teleoperator systems have considerable time delays between the master robot and remote robot. It is well known that the systems can be unstable even when a small time delay exists in the communication channel. In Chapter 3, we present a new design procedure of a teleoperator controller for time-delayed telemanipulation using the internal model control structure. This approach allows a convenient means to achieve stability in the presence of time delay and modeling uncertainties as well as to optimize performance specification.
The parameters of the environment dynamics should be assumed to be unknown and to change significantly according to the task. And the stiffness parameter of a master robot changes significantly depending on whether an operator holds the master robot with a firm or loose grasp. These parameter changes can be regarded as parametric modeling uncertainties. In Chapter 4, considering parametric modeling uncertainties, we design robust bilateral controllers via μ-synthesis. Furthermore we address a case that the uncertain parameters vary over wide ranges about nominal values, which leads to very conservative controllers in the robust control framework. A scheme based on an adaptive control and the position-force architecture is proposed. Without any knowledge about the parameters of the slave robot and environment dynamics, the scheme can guar-antee robustness to the parameter uncertainties of the master robot as well as the stability of the whole teleoperation system. In Chapter 5, simulations and an experiment for 1 DOF gripper-type robot are performed to confirm the validity of the methods proposed in Chapter 4.