The Application Of Model-Free Adaptive Control On Large Time-Delay System

In industrial processes, since the large time-delay, it is difficult to obtain well performance with the traditional PID controllers. However, ordinary model-based control algorithms also cannot work well because of the difficulty of building accurate mathematical model for the large time-delay system.The large time delay control method of the object is described in this paper, and presents a main line of the Smith predictor control, combing the research achievements of the traditional control methods, and intelligent control methods in the large time-delay plants.This paper uses the advantage of the model-free adaptive control does not need to rely on a mathematical model of the controlled system, only the controlled system I/O data, without the need for any other system model information. According to the characteristics of the controlled system with large time-delay, an improved algorithm based the basic model-free adaptive control is deduced, constraint entry of the rate of change of the input with large time-delay is introduced in the input criterion function, and constraint entry of the change of the input with large time-delay is introduced in the pseudo-partial-derivative estimate criterion function, so as to achieve the purpose of constraint large time-delay.In this paper, the first, second and third order objects with large time-delay are selected and constructed, and nonlinear discrete-time systems with large time-delay is constructed, and the corresponding simulation blocks is developed, which are applied in the temperature control process simulation experiment. Contrasting analysis of the improved model-free adaptive control algorithms, basic model-free adaptive control algorithms and PID control algorithms for the above-mentioned systems by simulation experiment, the factors which affect the control performance were analyzed also.The simulation results show that the improved algorithm significantly improves the control performance, and has strong robustness, and the anti-interference ability for large time-delay, its control performance for the large time-delay system is better than the basic model-free adaptive control algorithm and PID control method.