Robust Overwhelming Control and Impedance Control

Abstract

Robust manipulator end effector trajectory control in presence of modelling uncertainties and unknown external disturbances is discussed in this chapter. The concept of overwhelming control is discussed first and it is shown how robust trajectory control is possible in unstructured and uncertain environment. The control laws are developed in the physical domain and then they are transferred to the numerical domain for computerized control. When the interaction force has to be controlled at the robot and environment interface, e.g. during a surgery, one needs a hybrid position/force control system. This chapter introduces the concept of virtual foundation which compensates the reference trajectory command in order to restrict interaction forces within the specified limits. The adjective virtual indicates that the foundation dynamics is implemented in numerical domain after it has been properly designed in the physical domain through bond graphs. Here, the idea of first conceiving a physical paradigm and then realizing it in the controller domain is utilized. The utility of physical model based control is highlighted. The recovery from amnesia or the positional error accumulated during force control is discussed in the next chapter dealing with a space robot application.