高频二维脉宽调制转阀流体控制特性研究

传统的阀控液压系统是利用液压阀节流孔来控制流量，存在很大的节流损失。基于数字液压的思想及受高速开关阀全开和全关状态理论上无节流损失的启发，本文提出二维脉宽调制转阀构型，将液压系统流量以流体脉宽调制的方式进行控制及分配，降低节流损失，同时通过主动溢流方式极大地消除溢流损失。在高压(负载)支路和低压(油箱)支路之间通过阀芯旋转快速高频切换输出离散流量；通过阀芯轴向位移控制占空比(恒定转速下，负载支路连通时间与回油支路总连通时间的比)以实现输出平均流量的控制。通过数学模型、仿真以及实验验证了高频二维脉宽调制转阀可将流体连续性流动转变为离散、可控的流动，从流体系统工作介质离散化的角度实现了一种新的流量控制方式。

Fluid Control Characteristics of High Frequency Two-dimensional Pulse Width Modulation Rotary Valve

The orifice of the hydraulic valve was used to control the flow in the traditional valve controlled hydraulic system, which inevitably led to very large throttling loss. Based on the idea of the digital hydraulic and inspired by the theory that there was no throttling loss in the fully open and fully closed state of the high-speed on-off valve, an innovative configuration of the two-dimensional pulse width modulation rotary valve was proposed to control and distribute the flow of hydraulic system in the way of fluid pulse width modulation, in order to reduce the throttling loss and greatly eliminate the overflow loss through the active overflow. With the rotation of the valve core, the oil could be quickly switched between the high-pressure (the load) branch and the low-pressure (the oil tank) branch, so as to output the discrete flow. And the duty cycle (the ratio of the communication time of the load branch to the total communication time of the oil return branch at a constant speed) was controlled by the axial displacement of the valve core to realize the control of the output average flow. Through the establishment of the mathematical model, the simulation and the experimental research, it was verified that the high frequency two-dimensional pulse width modulation rotary valve can transform the continuous flow of the fluid into discrete and controllable flow. When the output flow of the quantitative pump was 30L/min, the output frequency of the two-dimensional pulse width modulation rotary valve was 200Hz and the control pressure was 13MPa, the output pressure of the two-dimensional rotary valve could be maintained at 21MPa. Taking the duty cycle of 50% as an example, the load flow was about 12.3L/min. This was a flow control method from the perspective of the discretization of the working medium in the fluid system.