Abstract: It has been widely accepted that applying the traditional control method is difficult to achieve precise temperature control of the evaporator because the evaporator temperature has nonlinear, time-varying characteristics with a significant lag. Based on the evaporator production process analysis, an evaporator temperature control method based on the cascade fuzzy adaptive proportional-integral-differential (PID) is proposed here, which combines the fuzzy control theory with the cascade PID control theory to set up a Continuous Function Charts (CFC) configuration of fuzzy adaptive PID control for the main loop and the secondary loop. A real-time self-adapting amendment of PID parameters in the main loop and the secondary loop during the evaporator temperature control can be realized using this control strategy. The experimental results with the SMPT-1000 simulation equipment and Siemens PCS7 process control system show that after the real-time self-adapting amendment of PID parameters, the computed new proportional parameter can successfully accelerate the response speed of the system, the calculated new integral parameter can efficiently reduce the deviation of the system, and the deduced new differential parameter can wisely play an essential role in the anticipatory control. The corresponding experimental results demonstrated that the adjustment time of temperature response could be shortened by one-half, and the maximum deviation could be reduced by more than four-fifths. Additionally, the adjustment time of the temperature rise load could be shrunk by more than three-fifths, and the maximum deviation could be decreased by more than four-fifths. Moreover, the recovery time for the superheated steam perturbation could be narrowed by more than one-half, and the deviation of minimum and maximum temperature could be condensed by more than one-tenth. It is noteworthy that compared with the traditional cascade PID control method, the cascade fuzzy self-adaptive PID control strategy proposed here has the notable advantages of short regulation time, slight overshoot, and good robustness, which can overcome the shortcomings of the traditional cascade PID control method and provide an effective way and mathematical models to solve the problem of accurate temperature control in the evaporator. Therefore, the control strategy developed here has a particular significance in ensuring the smooth operation of the evaporator.

Key words: evaporator, temperature control, cascade fuzzy self-adaptive PID, PCS7, SMPT1000

摘要： 蒸发器温度控制存在时变性、非线性和滞后时间长等特性，传统控制方法难以实现温度的精确控制。通过对蒸发器的生产过程进行分析，提出了一种基于串级模糊自适应比例-积分-微分(PID)的蒸发器温度控制方法，将模糊控制理论和串级PID控制理论相结合，建立了主回路和副回路的模糊自适应PID控制连续功能图(CFC)，实现了对蒸发器温度控制的主回路和副回路PID参数的实时修正。采用SMPT-1000仿真设备和西门子PCS7过程控制系统的研究结果表明：PID参数实时修正后，比例参数加快了系统响应速度，积分参数减小了系统的偏差，微分参数起到了超前控制作用；温度响应的调节时间缩短二分之一，最大偏差降低幅度超过五分之四；温度提升负荷的调节时间缩短幅度超过五分之三，最大偏差降低幅度超过五分之四；过热蒸汽干扰的恢复时间缩短幅度超过二分之一，最低和最高温度偏差降低幅度超过十分之一。与传统串级PID控制方法相比，串级模糊自适应PID控制具有调节时间短、超调量小、鲁棒性好等优势，克服了传统串级PID的不足，为解决蒸发器温度精确控制提供了一种有效途径和方法。

关键词: 蒸发器, 温度控制, 串级模糊自适应PID, PCS7, SMPT1000