针对变转速直升机摩擦离合传动对高可靠电液压力伺服控制技术的需求,基于A型半桥液阻回路和并联数字液压技术提出一种阵列数字阀控电液压力伺服结构.在深入分析系统工作原理基础上,建立其数学模型,揭示等值编码型阵列数字阀输出流量特性.为进一步提高数字阀压力控制精度和使用寿命,提出一种融合非线性脉冲数量调制(Pulse number modulation,PNM)编码、非对称差动脉冲宽度调制(Pulse width modulation,PWM)、信号缓冲分配以及信号循环分配技术的混合编码控制策略.试验结果表明,当采用混合编码控制策略后,在跟踪恒定压力时的最大和平均误差相较于PNM编码控制器分别减少47.6％和87.9％,并且切换次数标准差相较于差动PWM控制器从31.6降至为2.5.因此所提出的混合编码控制策略可有效兼顾压力控制的高精度,以及阵列数字阀切换次数分布均匀性.
Hybrid Coding Control of Electro-hydraulic Pressure Servo System Using Array Digital Valves
Aiming at the technical requirements for highly reliable electro-hydraulic pressure servo control of variable-speed helicopter friction clutch transmission system,an array digital valves-controlled electro-hydraulic pressure servo structure is proposed based on A-type half-bridge hydraulic resistance and parallel digital hydraulic technology.Firstly,based on an in-depth analysis of the working principle of the system,its mathematical model is established,and the output flow characteristics of the equal coded array digital valves are revealed.Then,to improve the pressure control accuracy and the service life of the digital valves,a hybrid coding control strategy that integrates nonlinear PNM(pulse number modulation)coding,asymmetric differential PWM(pulse width modulation),signal buffer allocation,and signal cyclic allocation technology is proposed.Experimental results show that when the hybrid coding control strategy is adopted,the maximum and average errors are reduced by 47.6％and 87.9％respectively compared to the PNM coding controller,and the standard deviation of switching times is reduced from 31.6 to 2.5 compared to the differential PWM controller.Therefore,the proposed hybrid coding control strategy can obtain a better balance between the pressure control accuracy and the uniformity of the switching times among the digital valves.
array digital valvespressure servo controlPNM codingdifferential PWMhybrid coding control
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