基于均匀切换的并联数字阀控系统位置控制策略

针对并联数字阀控系统在脉数调制（PNM）控制下易出现低速定位精度低的问题，提出一种复合控制策略，即低速工况采用差动脉宽调制（PWM）控制策略，其余工况采用基于模型的PNM控制策略。各开关阀切换次数的差异程度在PNM控制下较大，且差异程度被差动PWM控制进一步放大，因此，为减小各开关阀切换次数的差异程度，基于循环滑动方法分别对PNM和PWM信号进行切换优化。实验结果表明，液压缸的平均定位误差从0.528 mm减小至0.032 mm，最小定位误差从0.221 mm减小至0.003 mm，开关阀切换次数的分布均匀性得到了显著提高。

Position Control Strategy of Parallel Digital Valve-Controlled Systems Based on Uniform Switching Method

Aiming at the problems of large positioning errors of a parallel digital valve-controlled system at low speed conditions under PNM control, a compound control strategy was proposed, where a differential PWM controller was adopted at low speed and a model-based PNM controller was adopted in other conditions.The differences among numbers of on/off valves’ switchings in digital flow control unit were big under PNM control and were further amplified by differential PWM control.Therefore, based on circular sliding method a uniform switching optimization was proposed to reduce the differences among numbers of on/off valves’ switchings.Experimental results demonstrate that the average errors of the hydraulic cylinder are reduced from 0.528 mm to 0.032 mm, and the minimum positioning errors of the hydraulic cylinder are reduced from 0.221 mm to 0.003 mm, the distribution uniformity of switchings among the valves is significantly improved.