目的 研究纸张定量控制回路中的大时滞控制策略，减小纸张定量偏差。方法 在传统Smith预估器的基础上，结合分数阶PID算法，设计由常规PID控制器和分数阶PID控制器组成的双自由度Smith预估控制系统，完成设定值跟踪和负载扰动的独立控制。设定值跟踪采用传统Smith预估控制器，负载扰动采用具有抗干扰和强鲁棒性的分数阶PID控制器。将控制算法应用到纸张定量中，并与传统控制算法相比较。结果 相对于传统Smith控制，基于分数阶PID的双自由度Smith预估控制的设定值跟踪及抗扰性能更优，在纸张定量控制过程中，将定量偏差减少到±1.6 g/m2。结论 基于分数阶PID的双自由度Smith预估器可有效控制时滞，模型失配时具有较好的鲁棒性，可有效提高定量回路的控制精度。

The work aims to reduce the paper basis weight deviation by studying the large time delay control strategy in the paper basis weight control loop. On the basis of traditional Smith predictor and combined with fractional order PID algorithm, a two-degree-of-freedom Smith predictor composed of traditional PID controller and fractional order PID controller was designed to independently control set value tracking and load disturbance. Set point tracking adopted traditional Smith predictor. Fractional order PID controller with strong anti-interference and robustness was served for load disturbance. The control algorithm was applied in the paper basis weight and compared with the traditional control algorithm. With respect to traditional Smith control, the set value tracking and anti-interference of two-degree-of-freedom Smith predictor based on fractional order PID were more excellent. In the process of paper basis weight control, the paper basis weight deviation was reduced to ±1.6 g/m2. The two-degree-of-freedom Smith predictor based on fractional order PID can effectively control time delay. With its good robustness when the model is mismatched, the control accuracy of paper basis weight control loop can be effectively improved.