Research On The Prediction And Control Method Of Servo Motion In Micro-EDM

Micro precision machining technology becomes one of the most important production technologies in manufacturing industry field, and particularly with several advantages, such as no macro-forces in machining process and no excessive requirement for machining system etc., micro-EDM has been widely applied in micro-scale machining field, showing tremendous technology potential, and receives attention and concern from both industry and academia all over the world. However, due to the natural characteristics of micro-EDM, such as high pulse power supply frequency, extremely weak discharge energy, complex machining environment and unstable spark discharge states etc., the machining process tend to have lots of uncertainties and randomness. To ensure the stability and effectiveness of machining process control becomes the key to promote the performance of the machining system and the efficiency and precision of the machining process.At present, fuzzy logic theory has been widely adopted in the machining process control of micro-EDM, which achieves good results. In comparison with traditional fuzzy logic, type-2fuzzy logic has better capability of handling the uncertainties in the nonlinear time-varying systems. In order to further enhance the fuzzy controller’s capability of handling the uncertainties of the machining process and improve the performance of micro-EDM system, on the foundation of the type-1fuzzy controller, a two-stage servo motion controller is designed based on the interval type-2fuzzy logic theory which is introduced in this paper, which enhance the machining system’s capability of describing the uncertainties of each variable; meanwhile, through the analysis of the affect caused to the stability of the machining process by the lagging of the regular detection-based control, coupled with the interval type-2fuzzy control method, a servo motion predictive control method is presented, which is based on calamities grey prediction and takes the servo feed speed as the prediction object, aiming at overcoming the affect caused by the lagging of the regular detection-based control method and improving the stability of the machining process, so that better machining efficiency can be obtained.Relying on the independently developed micro-EDM machine tool and taking micro-holes as the machining targets, the experiment researches are carried out to verify the feasibility of the interval type-2fuzzy control method and the calamities grey prediction based predictive control method, which are introduced in this paper. The experiment results show that, interval type-2fuzzy logic can handle the uncertainties of the micro-EDM system, in comparison with the type-1fuzzy control method, interval type-2fuzzy control method can obviously promote the machining efficiency, which confirms that interval type-2fuzzy logic is applicable in the machining control of micro-EDM; comparing with the machining process relying on the regular detection-based control, the predictive control method introduced in this paper can promote the machining efficiency to some extent and effectively minimize the frequency of the servo rollback (tool lifting). So, the calamities grey prediction based servo motion predictive control method can effectively overcome the affect caused by the lagging of the regular detection-based control method, which results in the stable machining process.The research on the prediction and control method of servo motion of micro-EDM in this paper provides conducive reference to ensuring the stability of machining process and promoting machining efficiency as well as facilitating the development of micro-EDM control method.