Test method for zero drift of electrohydraulic servo valve

Test method for zero drift of electrohydraulic servo valve

Two zero drift test methods are usually used: ① position closed-loop test method; ② Pressure closed-loop test method. The position closed-loop zero drift test diagram is shown in Figure 3. Close the switch s, and the current displayed by the ammeter is the zero bias value of the valve.

The pressure closed-loop zero drift test is shown in Figure 4. Close the switch s, and the current displayed by the ammeter is the zero bias value of the valve. It should be particularly pointed out that in order to ensure the test accuracy, the forward channel of the servo amplifier of the pressure closed-loop circuit should be designed with a PI type correction link, and the detection circuit should be changed into a type 1 constant value circuit. Compared with the position closed-loop zero drift test method, the pressure closed-loop zero drift test method has the following advantages:

(1) Friction and internal leakage inevitably exist in the hydraulic cylinder in the position closed loop, which will affect the test accuracy; The pressure closed-loop directly uses the differential pressure sensor to detect the pressure, which avoids the influence of external interference such as friction and internal leakage, and has high test accuracy.

(2) When doing acceleration, vibration, impact and other tests, it is often necessary to detect the zero drift of the valve online. For example, using the position closed-loop method will involve very troublesome problems such as hydraulic cylinder installation and pipeline connection; The pressure closed-loop test method is much more convenient than the former because it only needs to lead out the signal of the differential pressure sensor.