| A method has been presented in this paper that the Linear Direct-current Motor (LDM) is used to drive the electrode of the EDM (Electrical Discharge Machining) tool directly. This method can meet the requirement of high precision positioning and rapid reverse response in the process of EDM which the servo system should have, and can implement rapid feeding, exact positioning, automatic cutter back-off and rapid back when it is short circuit.The structure and operating principle of the LDM are introduced in this paper, and a mathematics model is established for dynamic characteristic analyzing.According to the characters of LDM, a scheme of LDM control system based on TMS320LF2407 is designed, which includes current inner loop, velocity middle loop and position outer loop. According to digital PID algorithm, DSP outputs the PWM wave with certain duty.ln response to the discharge gap states, the servo control system decides the priority of position control or speed control. The scheme is adopted that digital PI algorithm in velocity loop and current loop, as well as online autoregulative PID algorithm in position loop, to do online adjustment of the three parameters K_p, K_I, and K_D of the PID controller, by which problems of nonlinearity, parameter time-variation and model uncertainty of LDM are solved. The design process of fuzzy PID control is analyzed especially, and the results of simulation indicate that the fuzzy PID control system has done a better performance o n rapid r esponse speed a nd p owerful a djustment a bility t han t he traditional one. The fuzzy control regulation of simulation can help to realize the fuzzy PID control of LDM in practice.In the end, the hardware circuit and software architecture of LDM controller based on TMS320LF2407 DSP are specified according as the control scheme above. It is programmed by C and assemble language, and preliminary debugging has been done. |
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