Causes of vibration of electric actuators

by:Lianke Valve     2022-06-21
At the production site, after the control system is put into operation, various oscillation phenomena of the electric actuator are often encountered. Electric actuators and regulating valves operate in an oscillating state, which will affect their service life. Therefore, the oscillation phenomenon should be eliminated in the control system. There are many reasons for the vibration of electric actuators. Today, the 'Huquan' brand electric actuators are specialized in Ru0026D, design, production and sales. The Sino-foreign joint venture high-tech joint-stock enterprise---Shanghai Huquan Valve Co., Ltd. will provide details for our customers. Analyze some causes and elimination methods of electric actuator oscillation. 1. Oscillation is caused by the fluctuation of the transmitter output due to the fluctuation of the measured parameter. The measured parameter itself is a pulsating signal, such as the water level of the boiler drum, the outlet pressure of the reciprocating compressor, etc., which is easy to cause oscillation. This pulsating fluctuation will cause the transmitter output to change continuously, which will cause the entire control system to oscillate without a stable state during the transition process. At this time, it can be considered to install buffer components in the pressure guiding pipe for mechanical filtering, or install electrical dampers, adjust and increase the filter constant of the transmitter and receiving instrument, or close the root valve to eliminate vibration. 2. Improper tuning of the PID parameters of the regulator caused by improper tuning of the PID parameters of the oscillating control system will also cause the control system to oscillate to varying degrees. For example, the proportional gain of the single-loop PID regulator is too large, the integral time is too short, and the differential time and differential gain are too large, which may cause the system to oscillate and cause the actuator to oscillate. For the multi-loop control system, in addition to the above reasons, there is also a problem of mutual influence between the loops, and the resonance problem caused by inappropriate parameter setting. According to the existing problems, the PID parameters can be re-adjusted, so that the control loop has a certain stability margin without affecting the production and meeting the requirements of process control. 3. The system oscillation caused by the flow characteristics of the regulating valve cannot ignore the flow characteristics of the regulating valve. The flow characteristics of the regulating valve are too steep. As long as there is a small deviation in the adjusted quantity, the adjusted medium will change greatly. Even if the controller has a small output, the flow of the medium will vary greatly due to the valve, which will cause overshoot and cause the entire system to oscillate with equal amplitude. For the above cases, if the characteristics of the valve cannot be modified, the proportional gain of the controller can be reduced to improve the control quality. 4. Oscillation caused by the mechanical assembly of the electric actuator and the regulating valve The poor mechanical connection between the electric actuator and the regulating valve, such as excessive mechanical clearance, will also cause the actuator to oscillate. Therefore, it is necessary to purchase high-quality products. The actuator and regulating valve are best supplied by the manufacturer, and the installation quality must be guaranteed. 5. The oscillation caused by the external disturbance of the control system The oscillation caused by the external disturbance of the control system is often irregular oscillation, and may be occasional, which is different from the oscillation of the control system and itself, or is easier to judge , but it is more difficult to eliminate. The measures that can be taken are: connect the ground wire, take shielding measures for the signal wire, and the shielding layer can only be grounded at one point. 6. The failure of the electric actuator causes the braking mechanism of the oscillating electric actuator to fail, which will cause the electric actuator to fall off and cause oscillation. After the braking mechanism of the electric actuator fails, the brake is not properly closed, which makes the motor idle too long. Even if the deviation of the servo amplifier is zero, the deviation of the servo amplifier cannot be zero due to the over-adjustment of the valve position. Causes the motor to spin back and forth and oscillate.
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