Fuzzy adaptive force control of industrial robot manipulators with position servos

Abstract

A fuzzy adaptive force control algorithm is suggested for commercialized industrial robots equipped with position servo drives in cascade with a software filter for the control of acceleration/deceleration profile to avoid vibrational shocks due to a sudden start or stop, where the control algorithm is composed of a Fuzzy Interpolation Logic Controller (FILC) and a Fuzzy Adaptive Stiffness Estimator (EASE). FILC determines a control action according to the magnitude of an environmental stiffness in such a way that good force response is maintained regardless of changes of environmental stiffness. Specifically, some fuzzy controllers are designed for several representative environmental stiffness values, and then a control action for an estimated environmental stiffness value which is not the same as any representative stiffness values is decided by fuzzily aggregating different control actions of those fuzzy controllers. Here, FASE plays the role of estimating an environmental stiffness value and transfers the estimated stiffness value to FILC. To show the validity of the proposed adaptive fuzzy force controller, several numerical examples and some experimental results are illustrated, where soft, medium and hard environments are considered.