Enhancement of sensor-less cutting force estimation by tuning of observer parameters from cutting test

The cutting force measurement is a basic technology for process monitoring and optimization. For practical operations, the sensorless techniques for cutting force estimation based on internal information on machine tools is more desirable. In this study, the load-side disturbance observer (LDOB) is introduced in full-closed controlled ball-screw-driven stage to estimate the cutting force with high accuracy. Since the LDOB is a model-based technique, appropriate model parameters such as stiffness and damping, which precisely represent the dynamic characteristics of the feed drive system, are necessary for accurate force estimation. Generally, the model parameters are identified by dynamic identification tests such as tap testing or motor sweep test. However, it has been known that the dynamic characteristics of ball-screw-driven-stage is changed, for instance, depending on stage position and amplitude of exciting force. Therefore, the model parameters should be determined under actual cutting state. In this paper, from the above viewpoints, the concept and methodology, that the machine tools determine the model parameters of the cutting force observer by themselves based on their own responses to cutting test, is also proposed.