Research On The Precision Servo Feed System Based On Sliding Screw Drive

With the increasingly wide application of complex electromechanical equipment,the demand for complex functional surface is increasing in our country.Most of the surface accuracy requires the micro-nano scale,and the realization of it needs the servo feed system which can achieve micro-nano scale accurate displacement.Therefore,based on the sliding screw nut pair‘spiral transmission principle’ and’differential synthesis principle’,a new feed servo mechanism is proposed in this paper,which can achieve micro-nano scale high-precision motion control at a low cost.This paper takes a new servo feed system based on sliding screw drive as the research object.A series of research have been studied on dynamic characteristics,friction characteristics,creeping phenomenon and low speed feed characteristics.The main contents are as follows.(1)A new type of servo feed device based on sliding screw transmission is designed to meet the requirements of functional surface generation according to the research content of the subject.The system composition and hardware selection of the dual drive feed mechanism are introduced,and the control system of the feed test bench is built.(2)Based on the joint theory and using the finite element spring damping unit,a dynamic model of the total system is established.The first six natural frequencies and vibration modes of the system are obtained by modal analysis.The harmonic response of the dual drive feed system is analyzed to determine the vibration characteristics of the system in actual work.The research on dynamic characteristics of the feed system based on the joint modeling provides a reference for the improvement and optimization of the dual drive feed system and the design of the control system.(3)The friction model and dynamic model of the dual drive servo feed system are established.Firstly,the friction characteristics of the sliding joint surface of the sliding screw nut pair are analyzed.The mechanism of the creeping phenomenon of the servo feed system is analyzed from the micro point of view.The dynamic models of single screw drive,single nut drive and dual drive,which consider the nonlinear friction,are established by using the lumped parameter method.Finally,the dynamic model of AC servo motor based on PID three-loop control is established,which provide a foundation for the achievement of servo system full closed loop control and the design of friction compensation controller.(4)A full closed-loop Matlab/Simulink simulation platform of single sliding screw drive,conventional ball screw feed system and dual drive feed system of sliding screw considering friction is established.The platform verifies that the precision of dual-drive feed system based on sliding screw transmission is one order of magnitude higher than that of single drive sliding screw,and it can reach the precision of ball screw feed system most commonly used in CNC machine tools with a lower cost;Based on the feedforward control of velocity and acceleration,the feedforward friction compensation method based on LuGre friction model is adopted,and using simulation to verify the performance of the controller.