Friction compensation controller for load varying machine tool feed drive

• Friction compensation controller considering feed drive load change is proposed.
• Feed drive testbed of that the applied load can be easily adjusted is built.
• Effects of the applied load on feed drive friction characteristics are discussed.
• Position accuracy improvement using the proposed method is demonstrated.

The load applied to a machine tool feed drive changes during the machining process as material is removed. This load change alters the Coulomb friction of the feed drive. Because Coulomb friction accounts for a large part of the total friction the friction compensation control accuracy of the feed drives is limited if this nonlinear change in the applied load is not considered. This paper presents a new friction compensation method that estimates the machine tool load in real time and considers its effect on friction characteristics. A friction observer based on a Kalman filter with load estimation is proposed for friction compensation control considering the applied load change. A specially designed feed drive testbed that enables the applied load to be modified easily was constructed for experimental verification. Control performance and friction estimation accuracy are demonstrated experimentally using the testbed.