Modified Smith Predictor Control Research Articles

Optimization of a Robust Modified Smith Predictor Control Strategy for Integrating Processes with Dead Time

The presence of an integrator and dead time in physical processes reduces stability and robustness. It limits the response time of a system. Integrating plus dead time (IPDT) processes provide oscillatory and slow response if the parameters of a system are not tuned properly despite dead time compensators (DTCs) being used. To overcome these shortcomings, the Smith predictor based sliding-mode control (SP-SMC) strategy using the Jaya optimization technique for IPDT processes is proposed in this study. For the selected populations, the cost function and best controller parameters are evaluated. The proposed strategy is compared with the typical Smith predictor-based proportional, integral and derivative (SP-PID), and conventional SP-SMC design methods. To evaluate the performance, integrating first-order with dead time (IFODT) process models with different controllability relationships (CR) is considered. Robustness analysis of the controller is carried out in this study for 30% parametric uncertainties and bounded disturbances. The simulation tests on a laboratory process (level) control system reveal the supremacy of the Jaya optimization algorithm over prevalent control strategies. Compared to SP-PID and SP-SMC, the proposed design method shows an improvement of 33.07% and 12.58% in settling time and an improvement of 19.73% and 22.93% in rise time with 0% overshoot, respectively. The applied setup elicits better multi-level set point tracking and disturbance rejection capabilities with the step input. Besides, the proposed algorithm shows better closed-loop performance for numerical simulations of Models 1 and 2.

Modified Smith Predictor Based on H 2 and Predictive PI Control Strategy

In this paper, a new type of modified Smith predictor based on the H 2 and predictive PI control strategy is proposed. The modified Smith predictor not only has H 2 robust performance but also has a similar predictive PI control structure. By introducing a time delay term, the modified Smith predictor controller overcomes the shortcoming that the conventional control algorithm can only use the low-order approximation of time delay term to design the control algorithm. The modified Smith predictor controller’s output is related to the current system error and related to the output in a period before the controller. Simultaneously, the modified Smith predictor controller is applied to conventional process systems based on dynamic optimization estimation in the case study to show absolute superiority over the nonpredictive control method (such as the classical PID control method).

An Improved Lag-Time Compensation Technique in Distributed Networked Control System based on Smith Predictor

The geographically distributed feedback control loops connected via communication network elucidate the core of networked control system (NCS), wherein different users spread all over the world can regulate, direct and command the components of control system located at distant location. The proficiency of NCS provides sceptre to its user and multifaceted assignments are successfully endowed through it. The ascendancy of NCS is lowered through inconspicuous delays which destabilize the system. The induction of delays in the network lead to the proscription of packet delivery, bandwidth utilization and stable system response. In this manuscript Smith predictor is modified using Markov approach and Kalman estimation algorithm. The scheme has been implemented by using Matlab/ Simulink software for delay compensation. Performance analysis shows the robustness of modified Smith-Predictor controller in comparison to classical Smith predictor controller and proportional-integral-derivative based controllers.

Set Point Weighted Modified Smith Predictor for Higher Order Integrating Processes with Time Delay

This Paper Presents About The Synthesis Of Two-Degree-Of-Freedom Control Structure Based On Modified Smith Predictor Control For Higher Order Integrating Processes With Time Delay. This Control Synthesis Is Done Based On Chengqiang Yin Method. It Has Two Pid Controllers- One Is Set Point Tracking Controller Based On Direct Synthesis Method And The Other Is Disturbance Rejection Controller Based On Imc Principle. In This Work, A Set Point Weight Is Added With Pid Controller To Reduce Peak Overshoots And Settling Time In The Modified Smith Predictor. Two Simulation Examples Are Given To Demonstrate The Validity Of This Method.

Improved Cascade Control System for a Class of Unstable Processes with Time Delay

An improved cascade control scheme is proposed based on modified Smith predictor for controlling a class of unstable processes with time delay. The proposed control structure consist three controllers of which the secondary loop has one controller and the primary loop has two controllers. The secondary loop controller is designed according to Internal Model Control (IMC) principles. The primary loop set point tracking controller and disturbance rejection controller are designed using the same procedure based on modified Smith predictor control structure. An analytical method on the basis of the Internal Model Control design principle is adopted for the two controllers which reduces complexity in design. The two controllers in primary loop are designed as proportional, integral and derivative (PID) controller cascaded with a lead-lag filter. Moreover, suitable values are recommended for the three controllers based on extensive simulations. Simulations studies are carried out to demonstrate the effectiveness of the proposed method.

Optical Parametric Oscillator Longitudinal Modes Suppression Based on Smith Predictor Control Scheme

Fiber optical parametric oscillators (FOPOs) contain multiple longitudinal modes arising from the hundreds of meters to a kilometer scale length of their cavity. To obtain better understanding of the longitudinal modes and to find out how to suppress them, a model for the operation of FOPOs is introduced. This model utilizes the sinusoidal-input describing function (SIDF) as a quasi-linear approximation of the nonlinear dynamics of parametric amplification. Applying this model, the SIDF of the FOPO is derived, which predicts that the origin of the longitudinal modes is the presence of the cavity round-trip delay term in the characteristic equation (the denominator) of the transfer function. To eliminate the effect of the delay term, a modified Smith predictor control scheme has been applied to the FOPO cavity, and a control algorithm is developed. This algorithm has been numerically analyzed and experimentally implemented, where the results indicate drastic suppression of the longitudinal modes.

An automatic tuning methodology for a unified dead-time compensator

In this paper, an automatic tuning methodology for a modified Smith predictor control scheme is proposed. The main feature of the procedure is that it is applied in closed-loop (by either evaluating a set-point or a load disturbance step response) and it is suitable for self-regulating, integral and unstable processes. Further, the process parameter estimation technique is based on the evaluation of the integral of signals, thus making it inherently robust to measurement noise. Simulation and experimental results demonstrate the effectiveness of the methodology.

Enhanced PID Controllers Design Based on Modified Smith Predictor Control for Unstable Process with Time Delay

A two-degree-of-freedom control structure is proposed for a class of unstable processes with time delay based on modified Smith predictor control; the superior performance of disturbance rejection and good robust stability are gained for the system. The set-point tracking controller is designed using the direct synthesis method; the IMC-PID controller for disturbance rejection is designed based on the internal mode control design principle. The controller for set-point response and the controller for disturbance rejection can be adjusted and optimized independently. Meanwhile, the two controllers are designed in the form of PID, which is convenient for engineering application. Finally, simulation examples demonstrate the validity of the proposed control scheme.

Modified Smith predictor design for unstable processes with step and periodic disturbances

In this article, a modified Smith predictor control scheme is proposed for step and periodic disturbance rejection for unstable processes with time delay. The scheme consists of three controllers: first one for set-point tracking, second one for nonperiodic disturbance rejection, and the third one for rejecting the periodic disturbances and improving the robustness. The set-point tracking controller is designed using the classical direct synthesis method based on the process model without considering the time delay. The nonperiodic disturbance rejection controller is also designed using the direct synthesis method. For further improved disturbance attenuation, a periodic disturbance rejection controller is designed. An analysis for the selection of the closed-loop tuning parameters of the controllers is carried out with the peak value of sensitivity function ( MS) as a robustness measure. The present method gives improved nominal and robust performances for step and periodic disturbances and also improved closed-loop performances when compared to recently reported methods.

Modified Smith predictor and controller for time delay processes

A modified Smith predictor control scheme is proposed for controlling stable, integrating and unstable processes with time delay. The two-degrees-of-freedom control structure along with simple tuning rules result in improved servo and regulatory performances by independently tuning a single control parameter. A convenient property of the proposed control scheme is that it decouples the setpoint response from the load response. The H 2 optimal control method is used to design the setpoint tracking controller and an optimal IMC filter is proposed to design a PID controller that produces good disturbance rejection performances. Simulation results show the simplicity and superiority of the proposed method compared with some reported methods.

Modified Smith predictor design for periodic disturbance rejection

In this paper, a modified Smith predictor control scheme is proposed for periodic disturbance rejection in both stable and unstable processes with time delay. Without affecting the superior setpoint response of Smith predictor control, the regulation performance under periodic disturbance can be enhanced significantly by the proposed design. Meanwhile, the asymptotical rejection for non-periodic disturbance will also be improved. Internal stability is investigated for a closed-loop control system. The effectiveness of the proposed scheme will be demonstrated by simulations as well as a test on an experimental thermal system.

A double two-degree-of-freedom control scheme for improved control of unstable delay processes

A double two-degree-of-freedom control scheme is proposed for enhanced control of unstable delay processes. The scheme is motivated by the modified Smith predictor control in [IEE Proc. Control Theory Appl. 16(5) (1999) 359] and devised to improve in the following ways: (i) one more freedom of control is introduced in our scheme to enable manipulation of disturbance transient response, and is tuned based on minimization of the integral squared error criterion; (ii) four controllers in the scheme are well placed to separately tune the denominators and numerators of closed-loop transfer functions from the set-point and disturbance. This allows easy design of each controller and good control performance for both set-point and disturbance responses. Especially, improvement of disturbance response is extremely great, compared with [IEE Proc. Control Theory Appl. 16(5) (1999) 359; Automatica 36 (2000) 1651]. Internal stability of the proposed structure is analyzed, which has not been reported in the literature on modified Smith predictor control before. Examples are provided for illustration.

Simple control method for integrating processes with long deadtime

Abstract Control of integrating processes with long deadtime is a challenging problem. Using original Smith predictor control structure will result in an offset problem during load disturbance. Using the internal model control (IMC) principle to design the control structure will result in large overshoot during servo response. In this work, a simple modified Smith predictor controller design is proposed for this important type of system. The overall control structure has only two physically meaningful tuning parameters. One is used to set the speed of the closed-loop servo response and the other tuning parameter is used to set the speed of the closed-loop load response. Two examples are used to demonstrate the improved closed-loop performance of the proposed controller design.

New Smith predictor control for the time delay systems

In the present paper, we examine a design method of Smith predictor control system with time delay. Almost past proposed Smith predictor control design methods cannot apply for the system having open right half plane poles, but those by De Paor et al. and by Kwak et al. can. Since the control structure of the modified Smith predictor control systems proposed by De Paor et al. and by Kwak et al. are limited, nothing has been reported whether or not, the modified Smith predictor control system can represents all of stabilizing controllers for the plant with time delay. If the modified Smith predictor control system can represent all of stabilizing controllers for the plant, the modified Smith predictor control system is effective. The purpose of the present paper is to give a new control structure of the modified Smith predictor control system for unstable minimum phase systems with time delay. Proposed structure can represent all of controllers for the unstable minimum phase systems with time delay.

Inverse-based Design for a Modified PID Controller

A modified PID (m-PID) controller design using low order dynamic models is presented. In contrast to the one of Haggland and Astrom (1985), the controller uses model-based parameters. Synthesis of such a controller is by way of an inverse-based approach. By this approach, a pure lead is introduced into a l=p to make the system equivalent to a modified Smith predictor (MSP) control system. Tuning rules for this m-PID controller are then derived from this equivalent system. For robustness, gain and phase margins are analyzed. It is found that this proposed m-PID control system has good responses to both set-point and load changes. Tuning rules derived from reduction of this m-PID controller for conventional PID control have also been presented.

Modified Smith predictor control for multivariable systems with delays and unmeasurable step disturbances

The paper presents a new disturbance rejection version of the Smith predictor control system (Smith 1959) and of the multivariable one (Donoghue 1977). The method uses a dynamical compensator and can decay the output error to disturbances as fast as desired without any change of the input-output transfer characteristics of the Smith predictor control system. The design procedure of the compensator and the mechanism of the disturbance rejection are discussed. Numerical examples are given to demonstrate the availability of the method.

Modified Smith Predictor Control for Multivariable Systems with Multiple Delays Subject to Unmeasurable Disturbances

This paper is concerned with disturbance rejection of multivariable Smith predictor control for multiple-delay systems. The Smith predictor control method can convert the delay control problem to the delay-free one, and yield desired responses to the reference inputs. However, if the process is subject to unmeasurable disturbances, the error decay can not be made as fast as desired. Particularly, if the process has poles near the origin in the complex plane, the output responses may be sluggish enough to be unacceptable. A new method which can yield zero steady state error and desired transient responses to the disturbances is proposed.