Abstract
The control strategy research of the time-delay system is a focused issue in the control field. In order to furthermore improve the performance of the first-order time-delay inertial system, firstly, a new Smith predictor structure is proposed, which solves the constraint that the conventional Smith predictor needs to match the actual object model. Secondly, the performance and parameter function of the new Smith predictor are discussed in theory to provide the basis for parameter tuning. Finally, a new Smith predictor combined with linear active disturbance rejection control (LADRC) is proposed to solve the problem that the two input signals of the linear extended state observer (LESO) are not synchronized on the time scale, and the stability of the new Smith + LADRC time-delay control system is proved theoretically for known and unknown controlled complex objects. Simulation analysis is conducted to verify the robustness of the proposed strategy under the condition of the different parameters. The results indicate that the proposed strategy has better performance than the conventional method in response speed, overshoot, adjustment time, and stability.
Highlights
Time-delay system widely exists in the industrial production process, which is a difficult problem of process control [1]
Many intelligent controls and composite controls that are composed of several kinds of control appeared, such as adaptive control [3, 4], model-free control [5], neural networks control [6], predictive control [7], Smith + PID [8], PI + multimodel dynamic matrix control [9], and Fractional Order Proportional-Integral-Derivative [10]. ese algorithms are suitable for the case that the object has less time delay or variation of parameters
To estimate the states of the system effectively, two input signals of linear extended state observer (LESO) need to be processed synchronously. It can realize the synchronization of two input signals of LESO by introducing the Smith predictor, but the conventional Smith linear active disturbance rejection control (LADRC) will lead to the instability of the system when the parameter perturbation occurs to the object
Summary
Time-delay system widely exists in the industrial production process, which is a difficult problem of process control [1]. Since the extended state observer (ESO) and the error feedback control law of ADRC contain nonlinear functions, it is difficult to analyze the stability, and many parameters need to be tuned. Gao used linear functions to process the ESO and error feedback control law and proposed the linear ADRC (LADRC) method [15, 16], which makes the stability analysis and parameter tuning easier. In [20], the stability conditions and parameter perturbation of Smith + LADRC for the first-order large time-delay systems are analyzed. Based on the above investigations, a new Smith predictive LADRC method for the first-order time-delay system is proposed, and its prediction mechanism and stability are analyzed under the condition that the controlled object model is known and roughly known through simulations. When the linear function is used in SECL and ESO, the active disturbance rejection is called linear active disturbance rejection, which is beneficial to the theoretical and engineering design and parameter tuning and easy to use the frequency domain method to analyze the stability in engineering
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