Vibration control of feed drive in NC machine tools by dual actuation (1st report) - Damping control of 2 mass system by relative velocity feedback

Abstract

High speed feed drives are being introduced to machining centers for aiming high speed and high productive machining. High lead ballscrew drives are generally used in practical applications, as they are cost-effective and robust to disturbances such as cutting forces. However, ballscrew drives suffer from vibration due to low damping of ball or roller guideways which are commonly used in high speed feed drives. This paper deals with a dual actuation drive, which has direct actuators in the drive table as well as conventional ballscrew drive mechanism. In this actuation system, relative velocity feedback (RVFB) controllers are investigated to give the adequate damping for servo system. By using modal analysis, RVFB gain can be interpreted as damping ratio of 2 mass vibration system. Three types of RVFB are analyzed and compared to direct velocity feedback (DVFB) theoretically. The damping control performance is examined by numerical simulations and experiments, which have good agreement with the theoretical analysis.