Research On Friction Modeling Analysis And Compensation Of Two-Axis Differential Micro-Feed Servo System

One of the key technology bottlenecks of ultra precision machining is how to make the tool or workpiece accurate,stable and reliable micro displacement in the process of machining,that is,the precision drive feed technology.Precision drive feed system plays an important role in precision operation such as precision measurement and precision machining.The conventional drive feed system based on the servo motor and the rolling contact component is difficult to achieve precise and uniform motion of the displacement feed because of its low speed and nonlinear crawling problem,which can not meet the urgent needs of ultra precision machining.In order to meet the urgent needs of high precision machining technology,macro and micro drive technology is an effective strategy to realize large stroke and high precision motion control at present.It has high positioning precision and dynamic response speed.However,the hysteresis nonlinearity inherent in the actuation of micro actuation intelligent material not only increases the difficulty of system control,but also makes the system more difficult to control.Its positioning accuracy is discounted.Therefore,based on the principle of nut driven ball screw and differential synthesis,the author proposed a "dual axis differential speed servo system".In order to improve the control precision of the dual axis differential feed servo system,this paper focuses on the dynamic characteristics,nonlinear friction,thermal deformation and other factors,focusing on the modeling,identification and analysis of friction,and puts forward a more perfect system modeling and error compensation method.The main contents are as follows:(1)The finite element model of the feed system is built on the basis of the theory of the joint part.Theoretical and experimental modal analysis of the feed system is carried out.Based on the finite element model of the feed system,the influence of the quality and position of the table,the stiffness of the ball screw pair,the stiffness of the rolling guide pair and the stiffness of the bearing on the dynamic characteristics of the feed system are studied by theoretical calculation.(2)The friction of the contact parts of the rolling contact components of the feed system are analyzed.Because the structure and driving mode of the dual axis differential system can not be identified by the conventional friction parameter identification method,a method for the identification of the full component friction parameters is proposed.The friction parameters of the two drive shaft and the table are identified respectively by this method,and the accurate full component friction model of the feed system is established.The accuracy of the whole component friction model and the conventional friction model is compared with the friction effect observation experiment.(3)Establish a Matlab/Simulink simulation platform including the system precise dynamic model and the full component friction model.Based on the whole component friction model,a low speed feed characteristic analysis method considering the driving shaft and the critical speed of the worktable is proposed.The method is used to study the dual axis differential system and the single drive system under different working conditions.The critical crawling speed of the two systems and the speed range suitable for the differential drive mode and the conventional driving mode are obtained through the analysis of the speed response of the two systems,and the performance of low speed trace feed performance and the speed tracking performance of the commutation zone are verified by experimental comparison.(4)The friction compensation control method for biaxial differential systems is studied.A feedforward friction compensation control algorithm based on proportional differential control is designed to compare the effect of feedforward friction compensation control based on the conventional friction model and the full component friction model,and the effectiveness of the full component identification method is verified.Considering the uncovered part of the system modeling and the uncertain part of the model parameters,a wavelet fuzzy neural network observer is designed for the uncertainty of the observation system,and an intelligent two order sliding mode friction compensation control strategy is proposed to improve the position tracking of the dual axis differential micro feed servo system with the two order sliding mode variable structure control.It is possible to verify the feasibility and effectiveness of the composite control strategy through simulation and experiments.(5)The mechanical structure and driving mode of the Two axis differential micro feed servo system are different from the conventional feed servo mechanism.The temperature distribution of the system is also different from that of the conventional feed mechanism.By solving the heat generation,heat conduction and heat balance equations of the system,the distribution of the temperature field of the dual axis differential system is analyzed.The parameters of Elman network are optimized by differential evolution algorithm.The axial thermal error prediction model of dual axis differential system based on BP,Elman and DE-Elman neural network is constructed,and the validity and robustness of the modeling method are verified by experiments.