Research On The Fractional Order PID Controller For The Crude Oil Stabilization Heating Furnace

In order to meet the safety requirements of crude oil during storage and transportation,crude oil needs to be stabilized.To make preparations for the following processes,the heating furnace raises the temperature of the crude oil.The heating furnace is the core equipment of the whole equipment.The temperature control of ending part in the heating furnace directly affects yield and quality of product.However,due to its characteristics such as large time delay,high inertia and time-varying characteristics,the control in the process of production is extremely complicated.All of these make great difficulties in achieving the desired effects with guidance of the conventional control strategies.The fractional calculus theory can establish a better connection between the model and time;hence,it can be used to describe the physical phenomena of the real world comprehensively and exactly.In recent years,many researchers have designed the fractional order PID controller,which has been widely used in engineering.To solve the existing problems of stabilization of crude oil,this paper employs Smith predictor control theory,fuzzy control theory,neural network control theory and soft variable structure control theory to improve the performances of the fractional order PID controller.Then,the one-dimensional and three-dimensional crude oil stabilization heating furnace system with time delay can be well controlled.The main contents of this dissertation are as follows:1.Considering the limitations of time-delay and slow response,a Smith fractional order PID controller is designed to solve the problem of that in the heating furnace of crude oil.First,through discussing the theoretical basis of fractional calculus,the stability of fractional order PID controller in heating furnace is analysed.Then,the Smith predictor controller is applied to the stability control of fractional order heating furnace,by which the slow response in the heating furnace system with time-delay can be solved.Finally,based on static accuracy analyses,the appropriate Smith fractional order PID controller parameters are selected,and the effects of the order on the control time are discussed.Applying the designed controller in the fractional order heating furnace system,simulation results and engineering experiments verify the effectiveness of the controller.2.Regarding the problem that the controller parameters of heating furnace system of crude oil are hard to determine,a fuzzy fractional order PID controller that meets the requirements of control adaptability is designed.On the basis of Smith fractional order PID control,the fuzzy control method,with the guidance of expert experience and the stabilization of crude oil heating furnace characteristics,is introduced.18 fuzzy rules of that are designed.Based on the error and error rate of change,the optimum parameters of the controller are searched in the data base of fuzzy rule,and then,the heating furnace without time-delay,and heating furnace with time delay can be well controlled.The controller achieve stability control in heating furnace without time-delay,and heating furnace with time delay.The simulation demonstrates that the fuzzy method can effectively adjust fractional order PID control parameters and improve the performance of the control system.3.To solve the problem of time denaturation in the heating furnace system,a neural network-based PID controller is designed.Based on the Smith fractional order PID controller,we introduce the neurons,the three forms of error,error integral and error change rate to estimate the optimal parameters of the controller.Then,the heating furnace without time-delay and the heating furnace with time-delay can be well controlled.The simulation and data verify the effectiveness of the proposed method.Because the controller parameters can be adjusted automatically,the influence of the slow and small changes of the structural parameters of the heating furnace are overcome,and the system stabilization is faster and the system error overshoot is smaller.4.To solve the problems of control constraint and stabilization in limited time in the heating furnace,the fractional order PID controller with soft variable structure is designed.Based on the basic concept of finite time theory and soft variable structural control,a finite-time soft variable structure PID controller is designed to achieve the finite time stability control and constraint control for the heating furnace.The Lyapunov method is applied to derive the stability control of fractional order furnace in the limited time.The relationship between the controller parameters and the synchronization time is given.The simulation and data verify that the time of stabilization in the heating furnace are shortened through adjusting the parameters of the fractional order PID.