Low-Speed Characteristics Of Macro-Macro Dual-Drive Differential Sevrvo System

Ultra-precision and nano-processing technology are at the forefront of current manufacturing technology,but in order to achieve substantive breakthroughs in its technology,the core bottleneck is to improve the motion and dynamic accuracy of the processing mother machine.Servo system is the core component of the machine tool.There are friction effects among the mechanical components during its movement.The traditional "servo motor + ball screw" transmission mode is greatly affected by the low-speed non-linear creeping phenomenon.It is difficult to achieve uniform,micro-displacement,and continuous feed.At present,macro-macro dual-drive,hydrostatic technology and linear motor are commonly used to obtain large-stroke micro-feed.Its control algorithm is complex,and the cost of manufacture and maintenance are expensive.Based on the principle of velocity synthesis,a new micro-feed mode,macro-macro dual-drive differential servo system,was proposed by the author's tutor.In this paper,the macro-macro dual-drive differential servo system was taken as the research object.Its stiffness analysis,dynamic characteristics and low-speed motion characteristics is studied.The main contents include:A hybrid dynamic model of macro-macro dual-drive was established.Systematic analysis of the connection methods of various components in the system,taking into account the elastic deformation of the ball screw,in order to make the calculation more accurate,the ball screw is equivalent to Timoshenko beam.The contact stiffness of bearing,screw nut pair and guide rail pair was calculated by Hertz contact theory.Servo motors,the coupling and other parts were replaced by concentrated mass or equivalent spring.This system is a combination of "servo motor drive nut" and "servo motor drive screw".Because of its complex structure,if the vibration frequency of the system is close to the natural frequency of the system in the process of feed motion,the resonance phenomenon will appear,which will lead to the reduction of its motion accuracy and positioning accuracy.According to the dynamic theory,the energy equation of the dual drive system was established.By using Ritz series expansion method,the ball screw part is expanded,and the stiffness and mass matrix of the system are obtained.The dynamic simulation of the system was carried out by using MATLAB based on the state space method.The resonant frequency of the system was obtained.The resonant frequency was calculated by changing the parameters of some core components,and obtained the trend graph of the resonant frequency of the test bench.The system's elasticity,damping and nonlinear friction can cause the system to crawl,in order to analyze the speed characteristics of the macro-macro double-drive differential servo system.According to the principle of multi-body dynamics,in order to make the calculation result closer to the true value,the lead screw is treated as a flexible body,and the rigid-flexible coupling characteristics of the system were analyzed by ADAMS.The low-speed motion characteristics of macro-macro dual-drive differential servo system were analyzed.The displacement and velocity fluctuation of the table under quasi-static,uniform motion and sinusoidal motion were analyzed by simulation.It is concluded that the fluctuation of output speed is more obvious than that of uniform speed at variable speed.Finally,through the experimental verification,the trend of simulation analysis is consistent with the trend of experimental data,which proves the correctness of virtual prototyping,and the simulation analysis has a certain reference.