Research On Decoupling Control Method Of Multivariate Molecular Distillation Evaporation Process

Molecular distillation is a new kind of physical separation of non-equilibrium distillation technologies, this technology possess the Characteristics of multivariable, strong coupling and large time delay. The automatic control circuits of the molecular distillation process of the evaporation work at the same time and have strong coupling among all loops. This coupling will directly affect the control performance and stability of molecular distillation evaporation process. In this paper, a method of establishing mathematical model of the controlled object and the decoupling design of the control system is put forward to reduce the mutual influence among the control loops and improve the control performance and stability of molecular distillation evaporation process.A new identification method for multivariable plus time delay mode is proposed to effectively analyze the evaporation loop in molecular distillation system. An idea of transforming MIMO identification into SISO identification is used to simplify the identification, and the basis of the idea is proved. A equation set constructed by the response date of the process with step input, and the unknown coefficient of the equation set is obtained by using the Simpson numerical integration formula, the transfer function matrix is obtained by solving equation set mentioned above. The feasibility and estimate precision of the proposed algorithm has been demonstrated through a number of simulation examples and experiments.This paper uses the method of diagonal matrix decoupling to decouple the two input and two output of molecular distillation process and obtain the the transfer function matrix of molecular distillation and evaporation process of the decoupling compensator. This matrix will make the molecular distillation evaporation process of the transfer function matrix into a diagonal matrix. Due to removing of the coupling between the two control loop,it will achieve complete decoupling on the molecular distillation evaporation process.According to the equivalent process of decoupling,the internal model controller will be designed. By approximate process for the time delay in the decoupling controller and then using Maclaurin expansion formula, it can obtain the three parameters of PID controller and form a complete set of the multi variable system of the decoupling control scheme. Using this method in the decoupled molecular distillation system which is described in third chapter of this paper, the result proved that the controller using this method designing has good anti-interference performance and robustness. In this paper, the step of controller design is very simple and and convenient the engineering application and software realization.Using C++ language to write the decoupling control software based on ADS 1.2 which can run In the PC operation of X86 framework based on CPU.This software has realized the automatic calculation function for Internal model PID controller parameters and two input and two output’s decoupling process.