基于感应电压负反馈的数字化送丝系统

Digital wire-feeding system with armature induced voltage feedback

分析了受限单极式可逆PWM调速系统中电枢感应电压和旋转频率的关系,设计了基于DSP的数字化控制PWM调速送丝系统,通过采样电流断续时的电枢感应电压,采用数字PI方法调节PWM占空比,维持电枢感应电压恒定,实现送丝电机旋转频率恒定.该方法消除了负载电流对送丝速度的影响,具有和旋转频率负反馈相同的效果,但其结构和控制方法简单、成本较低.结果表明,电网电压波动以及送丝软管从平直状态到软管中部弯绕400mm一圈情况下,送丝速度变化率均小于±3%,满足标准规定的要求.

The relationship between armature induced voltage and wire-feeding motor speed in the limited unipolar mode of reversible pulse-width modulation (PWM) speed-control system is analyzed, and a reversible PWM speed-control system based on the digital control of a digital signal processor (DSP) is designed. The control method can eliminate the effect of load current on the speed of the wire-feeding motor by using synchronous sampling of armature voltage at the moment of zero current. The digital PI regulation method is used for adjusting the PWM duty-cycle to keep the armature induced voltage constant and improve the stability of wire-feeding. The test results show that the rate varieties of wire-feeding under the conditions of variable power network voltage and change of wire-feeding tube from straight state to a cycle of  400 mm at the middle all meet the standard requirements.