The Development Of A PID-type Fuzzy Algorithm Based On SIEMENS S7-300 PLC

A complex, nonlinear and large time delay control system often exists in industrial process systems, and its precise modeling is difficult to build so that traditional control algorithms cannot meet its requriment very well. However, fuzzy logic control algorithm(FLC) as one of the advanced control algorithms can solve the above problems very well.Meanwhile, programmable logic controller(PLC) is weidely used in all walks of life and provides an effiective means for the realization of a complicated control algorithm. This system aims at applying FLC in S7-300 PLC, and then FLC as a function is sealed up in a library in STEP7 software so that the technical development personnel can easily call the algorithm, which means that can reduce the workload and the complexity of programming. With the help of dSPACE real-time simulation and MATLAB build an easy call and debugging system platform to verity the algorithm and make the validation of the algorithm more realistic so that it can be better used in actrual production.First of all, this paper describes an analytical-structure and PID-type fuzzy control algorithm which adopts two different methods, namely the incremental algorithm and the position algorithm. The incremental algorithm can realize undisturbed switching from automatic model to manual model(A/M). The tuning process of the 4 parameters of the controller is given by combining the gain margin and the phase margin. And according to the system comprehensive performance evaluation index, self optimizing tuning method of the parameters is given. The 4 parameters' influence on the performance of the system is summarized.Secondly, the realization of the PID-type fuzzy control algorithm in PLC, whitch adopts the structured control language(S7-SCL), is detailly introduced. Assistant functions are A/M, output speed limit and dead zone limit. And then, the main funtion,the initialization subfunction and interrupt subfunction call the corresponding fuction by using LAD and STL. Download all the funtions to PLC. The overall closed loop control system is assembled by PLC, dSPACE and WinCC. And the feasibility of the fuzzy control algorithm is validated.Finally, 3 PID-type and adaptive fuzzy control algorithms are introduced and a function tuner and slope-change method(FTM-SCM) is proposed by combining with the above adaptive algorithms and according to the 4 parameters' influence on the performance of the system, and simulation experiments verify its availability.