Concerning first-order unstable processes with time delays that are typical in chemical processes, a modified 2-degree-of-freedom proportional–integral–derivative control method is put forward. The system presents a two-loop structure: inner loop and outer loop. The inner loop is in a classical feedback control structure with a proportional controller intended for implementing stable control of the unstable process; the outer loop is in a 2-degree-of-freedom structure with feedforward control of set points, where the system’s tracking response of set points is separated from its disturbance response. To be specific, the system has a feedforward controller that is designed based on the controlled object models and mainly used for regulating the system’s set point tracking characteristics; besides, it has a feedback controller that is designed on the ground of direct synthesis of disturbance suppression characteristics to improve the system’s disturbance rejection. To verify the effectiveness, the system is put into a theoretical analysis and simulated comparison with other methods. Simulation results show that the system has good set point tracking characteristics and disturbance suppression characteristics.

中文翻译：

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不稳定过程的修正2自由度比例-积分-微分控制器设计

针对化学过程中典型的具有时滞的一阶不稳定过程，提出了一种改进的2自由度比例-积分-微分控制方法。系统呈现两回路结构：内回路和外回路。内环采用经典的反馈控制结构，带有比例控制器，用于对不稳定过程进行稳定控制；外环采用 2 自由度结构，具有设定点的前馈控制，其中系统对设定点的跟踪响应与其扰动响应分离。具体来说，该系统具有前馈控制器，该控制器是基于受控对象模型设计的，主要用于调节系统的设定点跟踪特性；除了，它有一个反馈控制器，它是在直接综合干扰抑制特性的基础上设计的，以提高系统的抗干扰能力。为了验证其有效性，对该系统进行了理论分析，并与其他方法进行了仿真比较。仿真结果表明，该系统具有良好的设定点跟踪特性和扰动抑制特性。