脉宽调制中的颤振算法

Dither Algorithm in Pulse Width Modulation

脉宽调制以其高效、灵活、抗干扰等优势,成为电液比例阀的标准驱动方式。同时,通过给比例电磁铁施加颤振信号可改善阀心的动态性能。针对脉宽调制驱动中的频率和占空比两个控制参数,导出了低频时的寄生颤振计算式,结果表明其振幅和频率不能独立调节。高频时,通过改变占空比的方式可实现幅度和频率均可调的独立颤振。根据感性负载的电流特性,分别导出正弦波和三角波包络线的独立颤振计算式,数值仿真与试验结果相吻合。该算法特别适合于数字信号处理与控制系统。

Pulse width modulation （PWM） has become the standard for electro-hydraulic proportion valve amplifiers for it is efficient, flexible and anti-interference. Meanwhile, the dynamic characteristics of a proportional valve can be improved by superimposing dithers to the valve coil. Aiming at the two control parameters, the frequency and the duty ratio of the PWM, the algorithm of the parasitic dither in low frequency PWM is deduced. The result shows that the amplitude and frequency of the dither cannot be set independently. In a high frequency PWM, dither with independent frequency and amplitude can be generated separately by changing the duty ratio of the pulses. According to the current in inductive loads, the algorithms for two types of dither, one in sine wave envelop and another in triangle wave envelap, are deduced respectively. Numeric emulation agrees with the experiment result. The algorithm particularly suits for digital signal processing and control system.