A Study on Design of Process Control System in the Presence of Load Change

本研究的目的是开发一种在大负荷变化情况下的化工厂数字跟踪控制系统的设计方法。我们特别注意的事实是，感兴趣的化学过程是受时滞，非线性，以及控制输入和输出之间的直接联系。以下是本研究的发现1。基于LQI技术，我们得到了具有积分、状态反馈和预览作用的最优数字控制器。对于时延为单边的特殊情况，提出了一种计算反馈增益的算法，计算量较小。将上述控制算法应用于中试热力发电装置的控制，其目的是独立调节出水温度和流量，以跟踪给定的参考数据，且无稳态误差。提出了一种将精确输入输出线性化技术与上述跟踪控制算法相结合的非线性控制系统的设计方法。将上述方法应用于具有大负荷变化且具有时滞的非线性连续搅拌釜式反应器的跟踪控制。仿真研究表明了该算法的有效性。通过对标称参数正负20%的摄动，通过仿真验证了所得控制系统的鲁棒性。在这项研究中，我们理解了开发一种技术来检验所产生的非线性控制系统的鲁棒性的重要性，因为目前还没有一种方法来评估非线性跟踪控制系统的鲁棒稳定性。

The aim of this research is to develop a design method of digital tracldng control system for chemical plants in the presence of large load changes. We direct much attention to the fact that the chemical processes of interest are subject to time-delays, nonlinearities, and direct link between the control input and output. The following are the findings of the present research.1. Based on the LQI technique, we derive an optimal digital controller having integral, state feedback plus preview action.2. For a special case of importance where the time-delay is unilateral, we develop an algorithm to compute feedback gain with less computational effort.3. We apply the above control algorithm to a control of a pilot heat exclianger plant, where the purpose is to regulate the water outlet temperature and flow rate independently to follow the given references without steady state errors.4. We present a design method of a nonlinear control system combining an exact input-output linearization technique and the tracking control algorithm of developed above.5. We apply tlie above technique to a tracking control of a nonlinear continuous stirred tank reactor(CSTR)with a time-delay and in tlie presence of large load changes. Simulation studies show the effectiveness of the present algorithm. Tlie robustness of tlie resulting control system is checked by simulations by giving perturbations of <plus-minus>20% to nominal paraineter6. During this research, we understand the importance of developing a technique for checking a robustness of a resulting nonlinear control system, since at present there exists no methodology to evaluate the robust stability of a nonlinear tracking control system.