Principles for design of position and force controllers for robot manipulators

The paper introduces fundamental principles for design of position and force (P/F) controllers. There are two principles guiding the design of a P/F controller: (i) the principle of invariancy; and (ii) the principle of consistency. The principle of invariancy serves as a guideline for the decomposition of the task space into force and position subspaces. The principle of consistency relates the free motion and constrained force to the characteristics of the environment. This principle guarantees the overall stability and the reduction of interactions between the position and force subcontrollers. Based on these two principles, a theoretical framework for design and analysis of P/F controllers is established, and a generic P/F controller is proposed. The proposed P/F controller and other generic P/F controllers are compared in terms of stability and interactions between the two subcontrollers.