Research Of Time Delay Systems Based On Smith Predictor

Smith predictor is used to solve the problem of the systems with time-delay, it plays an important role in the modern industrial manufacture. This article mainly aims at solving the problems of the system steady-state error, parameters uncertainty and the model mismatch. Taking the stability and the adjust time into consideration, different control schemes are adopted to advise the system.The main contributions of this thesis are listed as follows:1. Traditional Smith-Predictor fails to provide a null steady-state error in the presence of a constant load disturbance if the process exhibits an integral dynamics(IPDT).Different methods are used to design the controller in order to eliminate the impact of errors on the system.2.Adaptive control for Smith predictor with uncertain parameters are discussed. Since model mismatch caused by uncertain parameters, the plant can no longer track the original reference model. Traditional Smith predictor combining with the algorithm of model reference adaptive control(MRAC) is adopted to regulate the plant. Then, the uncertainty of gain and time constant are adjusted by the control algorithm, the uncertain structural perturbations are regulated through choosing better adaptive law. Finally, the adaptive law is obtained by Lyapunov function. The stability of the system is improved.3. Based on the fuzzy algorithm, the mismatch problems of Smith predictor is developed, involves the gain mismatch, time constant mismatch, time mismatch. According to different mismatch factors, different mechanism is used to eliminate the mismatch error.At the same time, the IMC is adopted to design the forward controller. Concerning the variables of the parameters, fuzzy algorithm is used to change the parameters. Through comparing with the exist system, the speed of the system’s convergence is fast.