Development And Optimization Of Temperature Controller For Thermostat

The thermostat is used for heating reagents and preserving heat.One of its quality indicators is the dynamic characteristics of the temperature inside.Thermostats usually have characteristics such as lag,large inertia,time variation,nonlinearity and uncertainty.It is not easy to control such a complex object using conventional controllers,and it is difficult to ensure the good dynamic characteristics of the temperature in thermostats.In order to control the temperature better,to realize the precise control of its temperature and ensure the quality of the stored medicine reagents,it is necessary to develop and optimize the temperature controller.The development and optimization of temperature controller for the thermostat are mainly realized in three aspects:model identification,controller design and optimization of the parameter of controller.In terms of model identification,an improved biased relay feedback identification method is used to obtain the transfer function model of the thermostat.The advantages and disadvantages of traditional relay feedback identification method are discussed,and through the derivation and mechanism analysis,a new relay feedback identification method is derived.Experiments are carried out on the thermostat,proved that the method has the advantages of accurate and rapidity and easy to implement.In terms of controller design,aiming at different accuracy of the model,identification-free adaptive control and IMC-Dahlin control are.developed respectively.Identification-free adaptive control does not require accurate mathematical models of controlled objects,but it still guarantees a good performance for nonlinear objects,time-varying objects and objects without accurate models.The control performance of IMC-Dahlin control is slightly better than that of identification-free adaptive control,but the requirement of the accuracy of the model is a bit higher.It has a good control effect for objects which has more accurate model and less nonlinearity than the prior one.Selecting the appropriate controller according to the actual situations,the temperature of the thermostat can be controlled more effectively.In terms of optimization of controller parameters,the parameter tuning method of identification-free adaptive control and IMC-Dahlin control is studied in this thesis.According to the design of robust controller,the control laws of them are respectively analyzed and deduced.Finally,the optimization problem of controller parameters is transformed into several linear matrix inequalities(LMI),and by solving the LMI,the optimal parameters are obtained.In the thesis,a set of improved formulas of relay feedback identification is proposed.The feasibility and reliability of this identification method are proved by simulation and experimental results.On the basis of identifying the transfer function of the object,an identification-free adaptive controller and an IMC-Dahlin controller are respectively designed and are discussed in detail in terms of the principle and the implementation method.On the basis of the controller design,this paper separately deduced and presented the parameter tuning method of the above controller.Finally,the control program on the embedded system is realized.Experiments on the existing experimental equipment are carried out.From the simulation results,the feasibility and reliability of the model identification method,as well as the controller design method and the controller parameter tuning method are proved.Two kinds of embedded controllers that can automatically identify the model and control the objects well are realized in the end.Different controller can be chosen according to the actual situation,and effective control can be achieved in medical,industrial and other fields.