Working principle of electro-hydraulic actuator Yonglong focuses on pneumatic/electric actuator
Time: 12:30:59, August 6, 2018 Source: Yonglong Valve Reading: zero second
Working principle of electro-hydraulic actuator - Yonglong has focused on pneumatic/electric actuator for 20 years
The input signal of the electro-hydraulic actuator is an electrical signal, and the power source of the output actuator is hydraulic oil. Therefore, it is especially suitable for applications with large thrust, large stroke and high-precision control. Compared with pneumatic actuators and electric actuators, electro-hydraulic actuators have larger thrust or thrust torque, faster response speed and accurate stroke positioning due to the use of hydraulic actuators. However, the hydraulic system requires more complex control of oil pressure pipeline and oil circuit system, such as the control of hydraulic oil temperature and pressure, as well as additional oil and oil circulation.
The electro-hydraulic actuator inputs the standard current signal, takes hydraulic oil as the working medium, converts the mechanical energy of the motor into the pressure energy of the hydraulic oil through the power components (such as hydraulic pump), and converts the hydraulic energy into mechanical energy through the pipeline and control components, and drives the valve rod to complete the movement of straight line or rotation angle with the help of the actuator.
Composition of electro-hydraulic actuator:
The electro-hydraulic actuator consists of two main parts, namely the actuator (cylinder and electro-hydraulic power assembly) and the control box. The actuator is installed on the driving device, and the control box is installed remotely. They are connected by module cable and feedback cable. The control box includes position control processor, power supply, motor driver, fuse and power filter, and terminal blocks.
There are three operation modes in the operating device of the position control processor: automatic, setting and local. When the actuator is in the automatic mode, it will reach the target position through automatic adjustment according to the control signal. When the actuator is in local mode, the actuator position can be adjusted manually. When the actuator is in the setting mode, the actuator can be calibrated and its operating parameters can be set, which control the dynamic characteristics of the actuator.
The position control processor (PCP) can enter the "setting" mode through a simple operation. Here, speed, travel, dead zone and control signals can be set through the three key area and display. Programming parameters can be obtained from permanent memory. PCP can diagnose various faults of actuator. The error code is represented by two letters on the five digit display screen, and the word "E -" is displayed in front of the error code.
The core of actuator is electro-hydraulic power module, including motor, gear pump, flow matching valve, oil storage tank, heater, bypass solenoid valve (unique to spring failure unit), etc.
The flow matching system allows the power module to be positioned incrementally. The motor and pump only act when the actuator needs to act. When not moving, the lock is in the original position. The system is fully capable of regulating tasks, and is not limited by starting, stopping or reversing.
Operating principle of electro-hydraulic actuator:
Depending on the preset parameters such as travel and signal range, PCP converts the external control signal into the target position, and the current position is determined by the feedback component installed on the actuator. The difference between the target and the current position is the error. If the error exceeds the dead zone (set by the user), PCP will recalibrate by starting the motor.
There is a reversible hydraulic pump driven by a motor inside the power module, which can be pressurized by one of the two flow matching valves (FMV-1 and FMV-2). Each FMV consists of an open valve core with an integrated check valve for guiding. The port sizes of the two FMVs are strictly consistent.
In order to move the piston to the left, the pump changes the rotation direction and pressurizes FMV-2 through port A. The valve core of FMV-2 loses its balance under the effect of pressure difference and moves to the left, holds its check valve, opens port D to port B, and port A to port E. High pressure flow flows from port E to the right chamber of the cylinder. Since the hydraulic circuit is closed, the same amount of oil flowing into the right side of the piston must flow out from the left side. This oil flow enters the pump suction through the check valve opened by FMV-2. By changing the rotation direction of the pump, the FMV operates in reverse to move the piston rod to the right.
When the pump stops. Both switching valves are closed. The hydraulic oil remains in the cylinder. The motor does not need to be operated to maintain the position.
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