Analysis of the Critical Stick-slip Velocity of CNC Machine Tool Combining Friction Parameters Identification and Kinetic Model

Abstract

Stick-slip is a negative phenomenon caused by friction in servo feed systems, which is particularly prominent in low-speed and heavy-load conditions. At present, most research on the critical Stick-slip velocity (CSSV) ignores higher-order terms of the equivalent damping ratio, the calculation accuracy is greatly reduced when the system has a large equivalent damping ratio. Firstly, an Improved Stribeck Model based on Least Squares Genetic algorithm (ISM-LSG) is proposed for friction identification, At the same time, the identification of shape parameters of the traditional Stribeck model is extended instead of empirical values. Then, an improved Critical Velocity solving method based on the kinetic model is constructed, and the influence of the higher-order term of the equivalent damping ratio on the critical velocity identification accuracy is analyzed. Finally, this method is verified by the CNC end-face cylindrical grinder with a hard guideway. The friction force identification error with ISM-LSG is reduced 10% compared with the traditional method, and the error of the critical Stick-slip velocity with retaining higher-order term (CSSV-RHT) is reduced 37% compared with the critical Stick-slip velocity by ignoring higher-order term (CSSV-iHT).