ADAPTIVE-CONTROL OF FORCE IN END MILLING OPERATIONS - AN EVALUATION OF AVAILABLE ALGORITHMS

Automatic adjustment of feed rate in end milling operations to maintain a desired force level improves overall productivity in manufacturing operations where machining time constitutes a significant fraction of part production time. Controllers with fixed gains function satisfactorily if variations in the machining process geometry are small. In the presence of large variations, the performance of fixed-gain controllers degrades, and adaptive controllers perform better. Since adaptive control systems are in general nonlinear and time-varying, they are not very amenable to comprehensive investigation of their performance. Instead, simulation and experiments are used to evaluate the characteristics of proposed adaptive control schemes for the operating conditions of interest. The current work presents a comparison of a fixed-gain controller and three available adaptive control schemes for force control in end milling. A validated model of the end milling process is used to evaluate the controllers through simulation. Control schemes are evaluated for change in the axial depth of cut for slot cuts, change in the radial depth of cut, and entry into the side of a workpiece by a rapidly moving cutter. We present the results of the simulation study and indicate significant differences in the performance of the investigated controllers.