The Stiffness Analysis Of Direct Drive NC Machine Tool Rotary Table Servo System

In order to meet requirements of the high speed cutting and high precise cutting technology, a new "zero-transmission" direct drive rotary table feed system driven by PMSM had been developed. Compared with conventional worm gear rotary table system, the direct drive PMSM rotary system has outstanding characteristics, such as the simple structure ,high acceleration, and high position accuracy. This new rotary table feed system is being used by more and more engineers who develop the new NC machine tools.In order to maintain the processing quality when they suffers disturbs from cutting force and make the machine tools have enough processing precision, exploit the high response characteristics of direct drive PMSM servo system in machining process, the servo control system must achieve tracking performance as high as possible a well as good dynamic servo stiffness.The dissertation mainly discusses the servo stiffness of direct drive NC rotary table servo system. Firstly, the merit and the shortcoming of the direct drive and the indirect drive are compared and evaluation method is brought foreword since the servo stiffness of the direct drive servo system take on new features. Secondly, the models of this control system and servo stiffness are given. A simulation is performed using software MATLAB to evaluate the influence of control structure , control parameters and mechanical characteristics on the dynamic stiffness direct drive servo system. In the fourth chapter, we infer an adaptive H_∞ controller and make simulations for this control system.