【作者】 蒋毅；

【导师】 赵万生； 顾琳；

【作者基本信息】 上海交通大学 ， 机械制造及其自动化， 2011， 博士

【摘要】 微小孔结构在汽车工业、航空航天工业、医疗设备、微电子器件等领域有着广泛的应用。电火花加工技术因其加工过程无宏观切削力、可加工所有导电材料、加工能力与材料的强度和硬度无关等特点,在微小孔加工中有着独特的优势。有效的电火花加工过程控制是电火花加工得以平稳高效进行的基础,包括了伺服控制、脉冲控制、以及所有对电火花加工过程产生影响的因素的控制。对电火花加工过程进行控制的依据是对加工状态的实时检测。本文首先分析了微小孔电火花加工的一些机理性问题,给出了微小孔电火花加工脉冲电源的设计目标,并在此基础上改进了主放电回路,实现了电容充放电过程的分离。针对微小孔电火花加工中排屑困难的问题,提出了采用窄脉宽大能量放电的清扫脉冲技术,设计了清扫脉冲回路,有效提高了微小孔电火花加工的效率。通过对脉冲控制技术的研究,完成了能够切断有害脉冲和施放清扫脉冲的微小孔加工脉冲电源开发,实现了对放电脉冲的精确控制。为了实现对放电状态的精确检测,分析了将小波变换应用于电火花放电状态检测的可行性,提出了基于小波变换的电火花放电状态检测方法及其实现途径,实现了数字信号处理技术与电火花放电状态检测技术的结合。实验结果显示,基于小波变换的电火花放电状态检测法能够较精确地获得单个脉冲的放电状态,与相应的控制技术结合后,能够有效应用于微小孔电火花加工的过程控制。为了实现在线实时的基于小波变换的放电状态检测,完成了采用数字信号处理器的电火花放电状态检测系统开发,该系统具有良好的实时性。针对微小孔电火花加工过程的时变性和非线性特点,设计了通过自校正调节器调节伺服参考电压,并通过模糊神经网络实现伺服参考电压跟随的微小孔电火花加工过程伺服控制系统。实验结果显示,采用这一伺服控制系统后,能够有效降低微小孔电火花加工过程中的有害脉冲比例,提高加工效率。对模糊神经网络控制系统的稳定性进行了研究,证明了所设计的模糊神经网络控制器的稳定性。为了研究本文开发的微小孔电火花加工过程控制系统的性能,进行了一系列深微小孔加工实验,获取了大量微小孔加工工艺数据。为进一步提高微小孔电火花加工的效率,对振动辅助微小孔电火花加工技术进行了研究,完成了基于音圈电机的微小孔电火花加工用振动平台的开发。实验表明,利用该平台施加合适的频率与振幅的辅助振动后,能够大幅提高微小孔电火花加工的效率。更多还原

【Abstract】 The structures of small-holes are widely used in auto industry, aerospace, medical science and micro electronics. Electrical Discharge Machining (EDM) is capable of machining all conductive materials with neglectable forces and irrespective to the material hardness and strength. These characteristics of EDM establish its predominant situation in the fields of small-hole machining. A stable and high efficiency EDM process depends on a robust process control system, including the servo control, the pulse control and other control units for the EDM processes. The fundmental part of the process control of EDM is the on-line gap status detecting.The design target of the pulse generator is determined based on the analysis of the mechanism of small-hole EDM. The main discharge circuit is improved by separating the charge and discharge processes of the capacity. In order to address the difficulty of debris evacuation, the sweep pulse, which has a short pulse duration and a high discharge energy, are applied to improve the machining efficiency remarkbly. A pulse generator is developed based on the pulse control technology. To shut off harmful pulses and apply sweep pulses, the control for pulses is achieved.In order to detecte the gap status accurately, the approach of the wavelet transform EDM discharge status detecting method is introduced by combining with digital signal processing technology. The experimental results show that the pulses can be distinguished and identified well by using the wavelet transform detecting method. This approach is capable of being applied in small-hole EDM process control together with a proper control strategy. In order to realize the on-line gap status detecting with wavelet transform method, a real-time signal acquisition and processing system is developed. A small-hole EDM servo control system is designed to adapt the time-varying and non-linear characteristics of small-hole EDM process. A self-tuning regulator is used to adjust the reference voltage, and a fuzzy neural network is used to realize the reference voltage following. The experimental results show that the percentage of the harmful pulses in small-hole EDM process is reduced and the machining efficiency is improved. The stability of the fuzzy neural network is also studied and validated by the experimental results.A series of experiments for deep small-hole drilling have been carried out and the effectivness of the process control system developed in this paper is verified. In order to make further efforts on machining efficiency improving, a voice coil actuator vibration platform is developed. The experimental results show that the machining efficiency of vibration assisted small-hole EDM is improved significantly with proper driving frequency and amplitudes.更多还原