Traditional PID controllers have problems of the inability to adjust online control parameters, poor control effects, etc. so this paper proposes an intelligent PID controller based on an improved fuzzy neural network. The controller not only combines the reasoning ability of fuzzy control and the learning ability of neural network, but also creatively parameterizes the fuzzy rules so that the fuzzy rules can also be adjusted online, thereby improving the accuracy of control. At the same time, by constructing a new type of activation function—IThLU function, it can effectively avoid the occurrence of gradient disappearance and gradient explosion, and improve the responsiveness of control. The final simulation experiment results show that the intelligent PID controller of improved fuzzy neural network can realize online real-time adjustment of control parameters, improve the responsiveness, stability and accuracy of the system, and is an effective improvement to the PID control algorithm.
表 1 评价指标Table 1 Evaluation index
图1 模糊神经网络结构图Fig.1 Structure of fuzzy neural network
图2 几个激活函数的比较Fig.2 Comparison of several activation functions
图3 IFNN-PID系统结构图Fig.3 Structure of IFNN-PID system
图4 阶跃响应Fig.4 Step response
图5 代价函数曲线Fig.5 Cost function curves
图6 IFNN-PID控制器的各参数在线调整曲线Fig.6 Several parameter online adjustment curve of IFNN-PID controller