【作者】 徐卫；

【导师】 孙同景；

【作者基本信息】 山东大学 ， 控制理论与控制工程， 2008， 硕士

【摘要】 随着工业自动化程度和焊接工艺要求的提高,弧焊电源的数字化控制已成为焊接领域的发展方向。脉冲MIG焊以其轴向性好、飞溅小、焊缝成形美观等特有的优点在焊接领域得到了广泛的应用。全数字化控制的弧焊电源具有灵活性好、控制精度高和响应速度快等特点,能极大提高脉冲MIG焊的控制水平。本文首先对脉冲MIG焊的熔滴过渡行为进行了研究,分析了脉冲电流各参数的作用,并提出了对焊接电流和电压的双闭环控制方案。其中电流环采用变参数的数字PI控制,使得电流快速跟随给定;电压环采用平均电压闭环控制,实现电弧的稳定调节。本文结合当前嵌入式技术和EDA技术发展的最新成果,选用ColdFireV2核微控制器MCF5213CAF80和FPGA EP1C6T144C8设计了脉冲MIG逆变电源的全数字化控制系统,搭建了该系统的硬件平台。其中MCF5213CAF80作为主控制器,负责电压环控制和焊接事务管理;FPGA作为协处理器,负责电流环的控制以及数字PWM模块的设计。两者通过在FPGA内部实现的并行总线接口进行数据的交换。在研究脉宽调制工作机理的基础上,本文采用高速计数器法,利用VHDL语言在FPGA内部实现了数字PWM模块。较之采用专用PWM芯片设计的模拟PWM控制方式,数字PWM简化了控制系统与功率变换电路的接口,提高了系统的响应速度和稳定性。另外,本文将实时嵌入式操作系统μC/OS-Ⅱ移植到MCF5213CAF80中,各个任务可以进行独立设计,使得焊机的事务管理更加方便。本文最后对所设计的全数字控制系统进行了测试,包括A/D转换精度测试、保护电路测试、PWM输出波形测试以及焊接过程波形控制效果测试。实验表明,该系统能够实现精确的电流波形控制和弧压闭环控制,为后续复杂的工艺研究和专家库的建立打下了坚实的基础。更多还原

【Abstract】 With the development of industrial automation and welding process requirements, the digital control arc welding inverter power source has become the trend in welding field. Pulsed MIG welding is widely used for its characteristics of good direction transition, less material splash and nice welding appearance. Full-digital control arc welding inverter power source can greatly enhance the level of pulsed MIG welding for good flexibility, high control accuracy and quick system response.At first, this paper studies the types of droplet transition in pulsed MIG welding, then analyzes the functions of the pulsed current parameters, finally proposes a dual-loop control method for welding current and welding voltage. Parameter-varying PI algorithm is applied to the current loop to adjust the welding current. The system uses the average welding voltage to keep the arc stable.This paper has designed full-digital control system for pulsed MIG welding inverter power source by establishing hardware platform using ColdFire V2 core microcontroller MCF5213CAF80 and EP1C6T144C8. The main controller, MCF5213CAF80, is responsible for voltage-loop control and welding affairs management; and EP1C6T144C8, the coprocessor, realizes the current-loop control and digital PWM module. These two controllers communicate with each other through the parallel bus interface built in FPGA.Based on the digital PWM mechanism, this paper introduces a High-Speed Counter Method to design the digital PWM module in FPGA implemented by VHDL. Compared with analog PWM mode using dedicated PWM chips, this method simplifies the interface between control circuits and power conversion circuits, as well as enhancing the system’s security and stability. Furthermore, the portability of real-time embedded operating systemμC/OS-Ⅱon MCF5213CAF80 makes it possible to design tasks independently and more convenient to manage welding affairs. Finally, this paper does some tests for the control system, including A/D conversion accuracy test, PWM output waveform test and control results test of welding process. Experiments prove that the system can control the current waveforms and average arc voltage precisely. The study helps to establish a solid foundation for subsequent complex research and expert system.更多还原