Control of cutting torque in the drilling process using disturbance observer

In the drilling processes of machine tools an increase of the drilling speed is usually required, but it often leads to breakage of the drill due to the excessive torque. Thus it is necessary to measure and control cutting torque in real time. In this study a new sensorless control system is developed of cutting torque irrespective of drill wear and the material of target work-pieces. The authors (1994) proposed an estimation method for the cutting torque using a disturbance observer. This paper is concerned with a sensorless PID torque control system for the drilling process based on the estimated torque information. Experimental results demonstrate the effectiveness of the proposed method.