Gains Selection for a Variable Gain Adaptive Control System for Turning

Abstract

The adaptive control constraint system described is a nonlinear, sampled data system designed to regulate the cutting force during turning operations. The controller keeps the system stable under wide variations in process parameters, limits the force overshoot, and provides fast transient response. The stability region of the nonlinear system was determined in order to define the boundaries of the gain space within which the optimal gains that minimize the ISE index of performance were selected. As a result, a data base for optimal gains as functions of process parameters was generated. Since in most cases the depth-of-cut changes in an unknown manner, the use of this data base is limited. To overcome this problem, an on-line adaption scheme of the gains was designed to achieve optimal response without the need for depth-of-cut measurements. With this control scheme, a series of simulations were performed that demonstrate excellent response under wide variations of process parameters.