大流量液压系统的油温控制

针对某大型液压系统的油温恒定需求,分析系统发热的数学模型和油液温度变化的滞后特性,提出一套运用比例水阀连续调节板式换热器冷却水量的大型液压系统油温控制方法.在Matlab/Simulink仿真环境中,比较分析使用常规PID和参数自整定模糊PID算法的油温控制特性.仿真结果表明,模糊PID控制器具有不依赖系统模型、响应快、控制精度高的优点,且易于PLC实现.将模糊PID控制方案应用于实际系统中,实验结果表明,参数自整定模糊PID控制器能够克服油温的大时滞、非线性变化,使得油液温度有效控制在45±1 ℃；参数自整定模糊PID控制器的响应速度、控制精度均优于常规PID,适合应用于大流量液压系统的油温控制.

Oil temperature control of large hydraulic system

A temperature control system was proposed employing proportional valve to regulate cooling water flow through a plate heat exchanger in order to retain the constant oil temperature in a large hydraulic system. Characterizing large time delay, the mathematic model of temperature variation was conducted based on laws of thermodynamics. The conventional PID control algorithm was compared with the fuzzy PID by using Matlab/Simulink. Simulation results show that the fuzzy PID strategy is independent on system model, and can efficiently improve the performance, which is easily realized with PLC. Fuzzy PID strategy was employed in the real system. Results show that the fuzzy PID controller can reach control accuracy of 45±1 ℃ under variant working conditions, which is irrespective of time delay problem and parameter variations. Compared with conventional PID controller, the fuzzy PID controller can achieve higher control accuracy, faster response and stronger robustness in oil temperature control of large hydraulic system.