As the core component of electro-hydraulic servo control system, the performance of servo valve directly affects the control accuracy and stability of the system. However, in the actual application process, due to the change of working environment temperature, the thermal expansion of servo valve internal materials, the temperature sensitivity of magnetic materials and the parameter drift of electronic components, the output characteristics of servo valve will shift, which is called “temperature drift”. The existence of temperature drift will seriously affect the accuracy and reliability of the control system, so how to effectively compensate the temperature drift of the servo valve is an important topic in engineering practice.
1. Cause Analysis of Temperature Drift of Servo Valve
Servo valve temperature drift mainly comes from the following aspects:
1. Mechanical deformation caused by thermal expansion of materials: The precise mechanical parts inside the servo valve (such as valve core and valve sleeve) will expand or contract when the temperature changes, which will lead to the change of mating clearance, and then affect the flow and pressure control characteristics.
2. Temperature drift of electromagnetic components: When the temperature rises, the resistance of electromagnetic coil increases, which leads to the decrease of driving current, which in turn affects the output torque of torque motor and causes the displacement deviation of valve core.
3. Nonlinear response of sensors and electronic components: feedback sensors (such as LVDT) and their amplification circuits will also have measurement errors at different temperatures, which will affect the accuracy of closed-loop control.
The superposition of these factors makes it difficult for the servo valve to maintain constant static and dynamic performance in high and low temperature environment.
Second, the compensation method of servo valve temperature drift
In order to overcome the adverse effects caused by temperature drift, there are mainly the following compensation methods:
# 1. Hardware compensation method
-thermistor compensation: install a thermistor near the electromagnetic coil, adjust the driving current by detecting the temperature change, and offset the influence of the coil resistance with the temperature change.
-Mechanical structure optimization: using materials with similar thermal expansion coefficient to manufacture the valve core and valve sleeve, so as to reduce mechanical deformation caused by temperature difference; Or design a mechanical structure with temperature compensation function.
# 2. Software compensation method
-Digital temperature compensation algorithm: By embedding a temperature sensor in the controller, the mathematical model between temperature and output error is established, and the control parameters are adjusted in real time to realize closed-loop temperature drift compensation.
-Neural network and adaptive control technology: the intelligent control algorithm is used to learn and correct the temperature drift online to improve the real-time and accuracy of compensation.
# 3. Comprehensive compensation strategy
Combining hardware and software means, a multi-sensor fusion temperature drift compensation system is constructed. For example, a closed-loop temperature control system is formed by arranging multiple temperature sensors at key positions of the servo valve and cooperating with digital compensation algorithm, so as to realize more efficient and accurate temperature drift suppression.
Third, the conclusion
With the continuous improvement of the precision requirement of servo system in modern industry, the problem of temperature drift of servo valve has been paid more and more attention. Through reasonable material selection, structural design, intelligent algorithm application and compensation strategy combining software and hardware, the influence of temperature drift on servo valve performance can be effectively reduced. In the future, with the development of intelligent sensing and artificial intelligence technology, the temperature drift compensation of servo valve will develop in the direction of higher precision and stronger adaptability, which will provide a strong guarantee for the stable operation of high-precision electro-hydraulic servo system.