Implementation of power and force adaptive control of the end milling process.

Abstract

This thesis explores the application of adaptive control for power and force control in the end milling process. The spindle power and cutting force are maintained at desired levels despite the variations in the depth of cut and the workpiece properties. A first-order discrete model is used to represent the relationship between the process output (spindle power or cutting force) and the feedrate input. By open-loop experiments, the model is validated and the process parameters of the spindle power and cutting force systems are identified. The process is found to have pure time delay and can be a non-minimum phase system. A Deadbeat (DB) Model Reference Adaptive Control (MRAC) algorithm is compared with modified MRAC, a typical scheme in existing adaptive control systems for non-minimum phase end milling processes. The design of the two controllers is described and simulations are presented. It is shown that the DB MRAC has less design complexity and superior control performance in simulation studies than the modified MRAC. Actual cutting tests of spindle power and cutting force control in the end milling process using the DB MRAC algorithm are carried out for a variety of cutting conditions. The control systems are stable with good transient and steady-state performance. The successful experimental results demonstrate the effectiveness of the DB MRAC scheme for spindle power and cutting force control of the end milling process and the feasibility of spindle power control in adaptive control of end milling processes.