Study On Bidirectional Asymmetric Pulse Micro-arc Oxidation Power Supply

With the development of the times,the demands for lightweight metal materials in the industrial area is increasing.However,lightweight metal material is easily worn and corroded,the scope of its application range is limited.As a kind of metal surface treatment technology,micro-arc oxidation technology which can effectively improve the quality of oxide coating and the performance of metal.Micro-arc oxidation power supply is the key equipment for micro-arc oxidation.Therefore,developing a novel micro-arc oxidation power supply has an extremely important academic and practical value for promoting the development of micro-arc oxidation technology.In this paper,firstly,the theory of micro-arc oxidation has been studied.With analyzing the relationship between the quality of the oxide coating and micro-zone thermal cycling,the adjustment ranges of the output electrical parameters of the pulse micro-arc oxidation power supply are determined.Based on the coating characteristics of the micro-arc oxidation,electrical models of the micro-arc oxidation load in different stages are established,from the simulation and analysis,the law between the power supply output mode and the trend of load voltage is obtained.Based on the above analyses,the design requirements of the micro-arc oxidation power supply are proposed.Secondly,based on the design requirements of the micro-arc oxidation power supply,this paper designs a novel bidirectional asymmetric pulse micro-arc oxidation power supply.The main circuit adopts the rectifier-chopper-invert three-stage topology to ensure that the power supply can output bidirectional asymmetric pulses.In order to reduce the volume of the micro-arc oxidation power supply,PIC18F4580 single-chip microcomputer has been selected as the control core of the power supply.In order to avoid large arc discharge in micro-arc oxidation process,this paper programs a double-closed-loop fuzzy PID control algorithm to improve the stability of output voltage and current.The human-machine interaction interface has been designed based on Weiluntong touch screen,the information of the power parameters and processing time can be displayed in real time,and the convenience of operation has been improved.Finally,a micro-arc oxidation power supply prototype has been fabricated according to the design scheme.The results of the prototype test show that the power supply can output bidirectional asymmetrical waveform,and can effectively avoid the occurrence of large arc discharge,the control process is steady and the human-machine interaction interface is concise.Using electron microscope to observe the morphology of the coatings,the results show that the coating generated by the fuzzy PID control algorithm is smooth,the membrane pore is uniform,the burning on the surface is not obvious and the coating quality is better.