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Adaptive Control
Published in Alex Martynenko, Andreas Bück, Intelligent Control in Drying, 2018
The process dynamics are characterized by a significant time delay resulting from conveyor belt transport delay. In general, such processes are challenging for control design and standard PID approaches are hardly able to guarantee the demanded specifications. To account for the time delay, a so-called Smith predictor (Bahill, 1983) can be used along with a standard PID design to improve the controller’s performance. The classical Smith predictor structure as depicted in Figure 7.9 relies on a parallel model of the process which is divided into delay-free part and delay. Design of the PID controller (or any type of controller) is based on the delay-free part of the model. However, to guarantee the desired specifications, an accurate estimation of the time delay is required. This motivated the development of adaptive Smith predictors that can deal with uncertain and changing values of these.
Unified Smith Predictor for MIMO Systems with Multiple Time Delays
Published in Krishan Arora, Suman Lata Tripathi, Sanjeevikumar Padmanaban, Smart Electrical Grid System, 2023
Time delays appear in many physical systems, especially in those involving information transmissions. The most famous method to deal with such kind of systems is the Smith predictor (SP). The SP designs the controller in such a way that the closed-loop response of a delayed system is the same as the delayed response of a closed-loop delay-free system [1,2]. The SP is also applied to time-varying delay [3]. But, it can only be applied to stable systems in which delay is perfectly known. This is the limitation over SP as many delayed systems are unstable.
FUZZY CONTROL
Published in Kumar S. Ray, Soft Computing and Its Applications, Volume Two, 2014
For systems with large time delays, most design approaches use a prediction mechanism as part of the controller to simulate the process for given system parameters and time delay. In the well-known Smith predictor, the controlled output is fed through models of the process with delay, and the process without delay, respectively. The difference of the output signals is added to the actual plant output and then fedback to the controller, thus allowing the controller to act of the prediction of the plant output.
Design of PSO-tuned FOPI & Smith predictor controller for nonlinear polymer electrolyte membrane fuel cell
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2022
Swati Singh, Vijay Kumar Tayal, Hemender Pal Singh, Vinod Kumar Yadav
The Smith predictor is a design-based controller that works well for long-dead-time processes (GnanaMuruga and Senthilkumar 2014). It features an inner loop with a primary controller that can be constructed quickly and easily without requiring any dead time. The Smith predictor is used in the construction of a controller for a plant that has a time delay or a time delay approximation. It works with a closed-loop control system. The effects of load interruption and model inaccuracy are addressed by an outer loop. The Smith predictor can be utilized for processes with significant nonminimum phase dynamics and high-order systems with apparent dead time. In control systems, the Smith predictor is frequently used as delay compensation device. For both minor and significant delays, this strategy can be employed. In the Smith predictor, the delay component from system’s closed loop is to be removed (Mirzal 2017). It is done as the systems’ stability is hampered with the delay component. Thus, the stability is enhanced by removing delay from the closed loop. In general, the closed loop response with delay is presented in Figure 6.
Control of Main Steam Pressure in Coal-Fired Power Plant Boilers by Fractional-Order Controller with Smith Predictor Structure for Delay Compensation
Published in IETE Journal of Research, 2021
Mehdi Doostinia, Mohammad T. H. Beheshti, Masoud Babaei, Seyed Amir Alavi, Amin Ramezani
This research has comprehensively evaluated the performance of an optimal fractional-order PID controller with the Smith predictor strategy for the main steam pressure control in a Coal-fired power plant boiler. The objective of this proposed control strategy is to delay effect compensate for a desirable performance of the closed-loop system as well as reaching the favorable response specifications for example lower rise time, settling time, and overshoot. The simulation results and the comparison with the traditional PID controllers illustrate the superior performance of the suggested controller. The comparison table between the traditional controllers and the proposed one shows the very low rise and settling times along with low overshoot. The same result is achieved for the mean square error. Moreover, the closed-loop system stability in the Smith predictor with the OFOPID controller has been analyzed thoroughly along with showing the larger stability region of the proposed controller. The limitation of the Smith predictor is the mismatch between the process model and the process. For future work, we will use the Smith predictor structure with a robust FOPID controller to overcome the mismatch between the process and the process model.
Uncertainty analysis of transfer function of proton exchange membrane fuel cell and design of PI/PID controller for supply manifold pressure control
Published in Indian Chemical Engineer, 2019
Srinivasarao Divi, S. H. Sonawane, Shantanu Das
In order to handle the time lag effects of a process, the control system should stay before response taking action. The performance of the PID controller is strictly restricted by the long dead time. The Smith predictor is the well-known control scheme to treat with time delay systems. Smith predictor is also known as dead time compensator as it compensates the dead time effects. In 1957, O. J. Smith developed the Smith predictor structure to compensate systems with time delay, where it is too difficult to control processes with long time delay using PID algorithm [17,18]