变PWM占空比的压电式阀门定位器控制方法

Control method of piezoelectric valve positioner with variable PWM duty cycle

压电式阀门定位器因其具有高可靠性、低功耗和低耗气量等特点,逐渐成为智能阀门定位器的主流。带反向PWM的五步开关法应用于小范围阶跃控制时,存在阀位启动慢、正向PWM脉冲个数多、调节时间长的缺点。在带反向PWM的五步开关法基础上,提出了线性化方法和分段PI方法变正向PWM占空比,小范围阶跃控制时,能够获得较大占空比的正向PWM脉冲,加速阀位启动过程,减少正向PWM脉冲个数,减小调节时间。在PI控制区(线性区)和死区之间设置了安全区,安全区内正向PWM占空比为最佳正向PWM占空比,保证了阀位能够很快的到达目标位置且不产生超调。在基于MSP430F5418超低功耗单片机的硬件系统上实时实现了该控制方法,取得较好的实验效果。

Piezoelectric valve positioner has gradually become the main stream of intelligent valve positioner,due to its high reliability,low power consumption and low air consumption.When a five-step switching method with backward PWM is applied to small-scale step control,there are disadvantages in slow start of valve,too much number of forward PWM pulses and long adjusting time.Based on the five-step switching method with backward PWM,the linearization method and segmented PI method are proposed to change forward PWM duty cycle.When this method is used in small-scale step control,it will gain forward PWM pulses with relative large duty cycle to accelerate the start of valve,reduce the number of forward PWM pulses,and reduce the adjustment time.The safe area is set between the PI control area(linear area) and the dead area,where forward PWM duty cycle is optimal PWM duty to ensure that the valve position can quickly reach the target position without overshoot.This control method is realized in real time based on the hardware with the ultra-low power MCU MSP430F5418 chip and good control results are obtained.