电液比例阀PWM控制中的颤振信号分析

摘要

Plus With Modulation ( PWM) is widely used in proporational control systems for it is efficient ,flexible and anti-inter-ference.Due to the friction and hysteresis of electromagnet ,hysteresis exists when hydraulic valve in steady-state,and hysteresis influences the dynamic characteristics of the valve seriously ,the hysteresis can be improved by superimposing dithers with certain frequency and amplitude to the valve coil .Aiming at the character of anti-unloading power driver circuit ,analyzed the parasitic dither which exists in ±24 V PWM control ,besides ,the experiment shows that in a high frequency PWM ,dither with independent frequency and amplitude can be generated by changing the frequency of the PWM ,in this way,the average current of electromag-net and dither can be adjusted separately by changing duty ratio and frequency of PWM .%脉宽调制（ PWM）技术以其高效、灵活和抗干扰能力强的特点被广泛应用在电液比例控制系统中。由于磁铁材料的磁滞和运动产生的摩擦力导致电液比例阀稳态特性存在明显的滞环现象，严重影响了电液比例阀的动态响应性能，改善滞环比较有效的方法是在驱动信号中叠加一定频率和振幅的颤振信号。针对反接卸荷式驱动电路的特点，详细分析了±24 V脉宽调制信号在电液比例控制中存在的寄生颤振，另外，根据实验得出，在高频状态下通过改变PWM波的频率可以实现频率和幅度均独立可调的颤振信号，同时该颤振叠加方式使得电磁铁平均电流和颤振电流分别受PWM占空比和PWM频率独立调节。