Task Specification and Closed Loop Control of Manipulators in the Presence of External Sensors

Abstract

Manipulators in an incompletely described environment require the feedback of the interaction between robot and object world by external sensors. A formal representation of a sensor guided robot action is characterized by two subtasks. The motion task describes the planned spatial trajectory, and the reaction task represents the interaction between robot effector and object. The control method presented relates to the base equation of manipulation which includes the two subtasks. The closed loop control in spatial coordinates requires an appropriate description of the dynamic behavior of the end effector. Coming from the servocontrolled arm it can be shown that the transient period of each Cartesian coordinate is similar to that one of each manipulator joint. A simple approach leads to an external closed loop control where the robot is modelled as a dead time alement in addition to a delay element. To achieve - flexible programming we propose a configurator for modules from which a variety of special sensory algorithms (skills) can be constructed. These modules are subdivided into a range of basic and complex functions. An experiment deals with a contouring method by the help of a force sensor. This has already been applied to the process of cleaning of castings.