Test method for dynamic performance of proportional directional valve
Test method for dynamic performance of proportional directional valve
1. Hydraulic test circuit for dynamic characteristics of four-way proportional directional valve
The dynamic performance test circuit is shown in Figure 15. When designing the system, the pipelines from oil ports a and B to the dynamic metering cylinder should be as short as possible, and the accumulator should be as close to the P port of the valve as possible.
The output signal of the valve can be measured by one of the following methods.
(1) The dynamic metering cylinder with low friction (pressure drop not exceeding 0.3MPa) and low inertia (the bandwidth is at least 3 times of the maximum test frequency including the trapped oil volume effect) is used to drive the speed sensor. When this method cannot be realized, method (2) or method (3) can be selected.
(2) In the valve with built-in valve center position sensor but not with built-in pressure compensation flow controller, the valve center position signal is used as the output signal.
(3)如果阀不带内置的阀心位置传感器，也没有内置式压力补偿的流量控制器，则有必要安装外置式阀心位置传感器，以及合适的测量放大器。只要附加传感器不会影响阀的频率响应，则可用此信号作为阀的输出信号。
如果采用动态计量缸测量阀的输出流量，可增加低增益位置反馈回路来纠正计量缸的漂移，以避免测试过程中产生撞缸现象。
方法(1)、(2)、(3)会得出不同的结果，因此，试验报告数据应注明所使用的试验方法。
2．频率响应试验
输入起始频率为0.2Hz或相位滞后90°时对应频率5%的输入信号（两者取小值），然后在衰减到15dB以上的频宽范围内绘制出幅值比和相位滞后曲线，如图25所示。
Input the test valve with the following sinusoidal signals, and keep the amplitude of the sinusoidal input signal unchanged during the test cycle:
(1) Input a symmetrical input signal so that the output flow through ports a and B alternates near zero, and its amplitude is sufficient to form a peak output flow of approximately ± 5% of the maximum steady-state output flow. For positive cover valves, this test is carried out using an active dead zone eliminator.
(2) For the positive cover valve without dead zone eliminator, input the offset input signal, and adjust the DC offset signal and input signal to make the output flow always in one direction. In this way, the whole cycle of the valve core is always carried out on the middle side, and a flow sensor meeting the bandwidth is needed to replace the metering cylinder.
3. Step response test
(1) Response characteristics of input signal step. Trigger the step function generator, generate step input signal, act on the test system, and record the relationship curve between input and output, as shown in Figure 26. The amplitude of step input signal can be set as 5%, 10%, 25%, 50% and 75% of the rated input signal as required.
(2) Response to load step change. This test item is applicable to the valve with load pressure compensator. When the step pressure signal amplitude is 50% of the rated pressure (if necessary, under the condition of other step pressure signal amplitude), record the response of the maximum load pressure from zero to 50% and the step change of the maximum load pressure from 50% to 100%, as shown in Figure 27.
The circuit shown in Figure 15 is only applicable to the test of dynamic characteristics of proportional directional valve with symmetrical valve port. When the median function of the proportional direction valve is not O-shaped, or the valve port has an asymmetric structure, or the area ratio of the two valve ports is different, the dynamic characteristic test circuit shown in Figure 15 cannot be used. At this time, the frequency characteristic of a single valve port should be tested, as shown in Figure 28. At this time, the flow measurement device cannot adopt the linear moving structure, but should be rotary or orifice plate, otherwise there will be cylinder collision.
When the proportional amplifier inputs a positive signal, if the proportional electromagnet A is powered on, the stop valves 2 and 3 should be opened. The input sinusoidal signal is a sinusoidal signal superimposed on a constant positive amplitude signal, as shown in Figure 29.
When the proportional amplifier inputs a negative signal, if the proportional electromagnet B is powered on, the stop valves 1 and 4 should be opened. The input sinusoidal signal is a sinusoidal signal superimposed on a constant negative amplitude signal, as shown in Figure 29.
The flow signal obtained by the above method is not symmetrical about zero flow, as shown in Figure 30.
Through signal analysis, the frequency characteristics of the proportional directional valve with asymmetric valve port can be analyzed. This method is also applicable to the frequency characteristic analysis of proportional pressure valve (0 ~ 10V) and proportional flow valve (0 ~ 10V) with one-way signal.
