等编码数字流量控制单元编码变换与控制方法

Configuration Transformation and Flow Control of Equal-coded Digital Flow Control Unit

基于并联数字阀的数字流量控制单元(Digital flow control unit,DFCU)是数字液压系统的核心控制部件,在编码开关控制下DFCU开关组合数量随编码位数呈指数增加,面临控制计算量大、流量分辨率受限的问题。因此,提出等编码DFCU编码变换方法,通过减少编码位数缩小最佳开关组合搜索空间,减少控制计算量,并设计基于代价函数的编码开关控制、脉冲宽度调制(Pulsewidthmodulation,PWM)及其组合的多种控制器,提高流量分辨率保证控制精度。基于高速开关阀静态特性测试,拟合得到其流量-占空比-压力三者之间数学模型。以7-bit高速开关阀组成的等编码DFCU作为研究对象,利用不同高速开关阀数量的组合控制,变换为4-bit裴波那契编码和3-bit二进制编码,并分析编码变换前后的脉冲数调制(Pulsenumber modulation,PNM)、脉码调制(Pulsecodemodulation,PCM)、PWM及复合控制器的流量输出特性。试验结果从控制精度、计算量、切换次数的对比表明,DFCU在编码开关控制方式下以较少的启闭次数可实现离散流量有级输出,编码构型变换后可有效减少计算量,切换次数与冲击略有增多;PWM控制可实现近似连续的流量输出,但压力脉动和切换次数远高于编码开关控制;变换后的编码开关与PWM复合控制不仅提高了流量控制精度,可以实现与PWM控制精度基本一致的流量输出,且切换次数远小于PWM控制方式并可以减少控制周期内的计算量。

The digital flow control unit(DFCU)based on parallel on/off valves is the core component of digital hydraulics.The on/off combinations of DFCU increase exponentially with the coded bits under the coding-based on/off control,which faces the problems of large control calculations and limited flow resolution.Therefore,the coding transformation method of equal-coded DFCU is proposed by reducing the number of coded bits to narrow the search space for the best on/off combination and decrease the control calculation,The coding-based on/off control based on the cost function,pulse width modulation(PWM)control,and their compound controllers are designed to improve the flow resolution and ensure control accuracy.The mathematical model of flow-duty-pressure of the high-speed on-off valve is established by tests and fitting.The 7-bit equal-coded DFCU composed of high speed on/off valves is the research objective,which is converted to 4-bit Fibonacci-coded and 3-bit Binary-coded DFCU utilizing the combined control for different numbers of on/off valves and analyze the flow control characteristics under the designed pulse number modulation(PNM),pulse code modulation(PCM),PWM and compound controllers.The comparison results from control accuracy,calculation and switching numbers show that the DFCU can achieve the discrete flow output with less switching number under the coding-based on/off control,and the calculation can be effectively reduced after the coded configuration transformation,while the switching number and pressure shock are slightly increased;the PWM control can achieve the nearly continuous flow output,but the pressure pulsation and switching number are much higher than the coding on/off control;the transformed coding-based on/off control with PWM compound control not only improves the flow control accuracy similar to flow output of PWM control,and the switching number is much smaller than the PWM control and reduce the amount of computation in the control duty.