Force sensorless control of cutting resistance for NC machine tools by spindle motor control using variable pulse number T-method

This paper proposes a force sensorless control of cutting resistance for numerical control (NC) machine tools by spindle motor. In conventional NC machine tools, speed of spindle motor is set to a constant value during machining, and the spindle speed is determined according to operator´s experience. The proposed method estimates cutting resistance by disturbance observer, and the spindle speed is determined by controlling the cutting resistance to follow the reference value. In addition, a novel method for velocity calculation which is referred as variable pulse number T-method is proposed to reduce the velocity measurement noise and to improve the robustness of disturbance observer.