Research On Control Strategy Of Magnetic Levitation Linear Feed Unit

With the development of modern manufacturing industry,the machining precision and environment of numerical control machine tool have been put forward more and more stringent requirements.However,the feed unit is an important component of numerical control machine tools,and its performance directly affects the work efficiency of the machine tool.Then,there are many aspects of friction and wear in traditional feeding method which uses the rotary motor and ball screw,so the feed rate and accuracy are limited.In order to overcome the above shortcomings,the idea of magnetic levitation linear feeding came into being.Because of the static levitation above the linear guide rail and the indirect contraction with guide rail,the creeping phenomenon is completely eliminated.Thus,the precision and the service life will not reduce due to the wear and contact fatigue.So the high positioning accuracy can be achieved.However,it is necessary to control the magnetic levitation linear feed unit with nonlinear and open-loop instability.Therefore,the design of the control system is the core,which determine the double requirements directly of high speed and high accuracy of the magnetic levitation linear feed unit.As a research object,this paper focuses on thecontrol strategy of the magnetic levitation linear feed unit,and the purpose is to ensure that it can achieve efficient and reliable operation.First of all,this paper introduces the background of the subject and the significance of the research on the magnetic levitation control technology.On the basis of a large number of references,the present situation and development trend of magnetic levitation control technology in China and abroad are systematically summarized.Secondly,this paper introduces the basic structure and working principle of the magnetic levitation linear feed unit,and gives the mechanical and electrical model of the single degree of freedom of the magnetic suspension bearing system.In order to study the coupling characteristics of each degree of freedom,the Lagrange equation is used to model and decouple the five degree of freedom of the magnetic suspension support system.On this basis,the stability of the system is analyzed,and the control parameters are determined by the combination of theoretical calculation and experimental method.Then,based on the combination of fuzzy control,the adaptive principle and the traditional PID control,the adaptive fuzzy PID controller is designed to simulate the magnetic suspension support system.In order to reduce the external interference and its parameter change of the system,the adaptive discrete sliding mode control strategy is used.The simulation shows that the strategy can reduce the inherent chattering problem of sliding mode control effectively compared with the conventional sliding mode control.Finally,in order to verify the effectiveness of the control algorithm,a six degree of freedom magnetic levitation linear feed unit test platform is built.The overall structure of the control system is designed by using LPC2131 micro-controller,and the C language is used to program and debug in ADS1.2 ARM integrated development environment.Respectively,using adaptive fuzzy PID control and adaptive discrete sliding mode control to complete floating,stable suspension and anti-interference test of the magnetic suspension linear feed unit.Further,theexperimental results results are compared,and lay the foundation for the magnetic levitation control system for further research.