基于电弧特性的焊割电源控制优化研究

发布时间：2018-03-30 17:07

本文选题：弧焊与切割一体机　切入点：变参数切换　出处：《华中科技大学》2014年硕士论文

【摘要】：等离子弧焊与切割是工业制造中重要的加工方式，其电源控制特性直接影响焊接与切割质量，设计合理的电源控制器十分重要。常规设计近似认为等离子弧电压大小与其电流无关，但实测结果表明，等离子弧电压随电流变化会发生较大变化，从而降低了控制性能，针对上述问题，本文从等离子弧特性出发，采用变参数切换控制以及滑模控制的方法，提高了焊接与切割电源性能。对于等离子切割控制，本文结合等离子弧变化特性，提出了根据引弧电流大小动态改变切换参数的双环并联控制方法，从而提高小电流下引弧成功率。对于弧焊控制，为保证系统稳定，常规PI控制选择负载电阻最小时进行参数设计，当电弧负载阻值波动很大时，控制器的动态性能变差，导致焊接质量下降。针对此问题，结合滑模控制恒动态的特性，本文提出采用滑模控制器对弧焊电源进行控制的方法。在滑模控制器设计中，首先建立弧焊电源的等效状态空间模型，，采用输出电流误差及其积分和微分变量作为滑模被控参数，基于PWM定频控制策略产生开关管调制信号，从而解决常规滑模控制中存在的开关频率不固定的问题。为了解决焊割过程中负载变化对控制性能的影响，本文将电阻参数等效为负载电压与电流之比。同时为了减小间接控制对输出电流稳态误差的影响，在原有滑模被控参数的基础上增加了电流误差的二重积分量。最后对所述改进型滑模控制策略进行了实验对比，在电阻负载突变下，滑模控制器的超调量比PI控制器减小33.3%，调节时间缩短31%，在电弧负载下，滑模控制器的电流波动比PI控制器更加缓和，焊接的质量也相应提高。
[Abstract]:Plasma arc welding and cutting is an important machining method in industrial manufacturing. The quality of welding and cutting is directly affected by the power control characteristics of plasma arc welding and cutting. It is very important to design a reasonable power controller.The conventional design approximates that the voltage of plasma arc is independent of its current, but the measured results show that the voltage of plasma arc changes greatly with the change of current, which reduces the control performance.Based on the characteristics of plasma arc, variable parameter switching control and sliding mode control are used to improve the performance of welding and cutting power supply.For plasma cutting control, this paper presents a dual-loop parallel control method which can dynamically change the switching parameters according to the magnitude of the arc starting current, so as to improve the success rate of arc starting under small current.For arc welding control, in order to ensure the stability of the system, the conventional Pi control selects the parameter design when the load resistance is minimum. When the arc load resistance fluctuates greatly, the dynamic performance of the controller becomes worse, which leads to the deterioration of welding quality.In view of this problem and combined with the constant dynamic characteristics of sliding mode control, this paper puts forward a method to control arc welding power source by sliding mode controller.In the design of sliding mode controller, the equivalent state space model of arc welding power source is first established. The output current error and its integral and differential variables are used as sliding mode controlled parameters, and the switching tube modulation signal is generated based on PWM constant frequency control strategy.In order to solve the problem that the switching frequency is not fixed in the conventional sliding mode control.In order to solve the influence of load variation on control performance during welding, the resistance parameters are equivalent to the ratio of load voltage to current.In order to reduce the influence of indirect control on the output current steady-state error, the double integral of current error is increased on the basis of the original sliding mode controlled parameters.The current fluctuation of the sliding mode controller is more moderate than that of the Pi controller, and the welding quality is improved accordingly.
【学位授予单位】：华中科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN86;TG48

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