Robust Smith Predictor Research Articles

A modified Smith predictor based – Sliding mode control approach for integrating processes with dead time

This paper proposes a modified hybrid robust Smith predictor controller design for integrating processes with long dead time. The proposal results in a dynamic sliding mode controller for integrating systems on blending sliding mode control and Smith Predictor modification concepts. The design part of the controller corresponding to the sliding mode arises from an approximate model of the high-order nonlinear integrating process to characterize the non-self-regulating processes. The approximation to a First Order Integrating System Plus Dead Time is obtained from an experimental method that adopts identification procedures and avoids complex analytical resources. The model contributes to designing the dynamic sliding mode controller and tuning parameters. The resulting controller is a hybrid scheme that combines the sliding mode methodology, a smith predictor structure, and a PD compensator. The hybrid control topology is used for the first time for integrating systems with dead time. The proposed approach is applied to a high order linear integrating system with long-dead time and a coupled tanks system using hardware in the loop (HIL) simulation. The hybrid control topology provides enhanced controller performance, guarantees proven robustness to parameter modeling uncertainties, and attenuates high-frequency oscillations, counteracting the adverse effects of chattering. Integral of Squared Error (ISE), Total Variation of control effort (TVu), Maximum overshoot, and Settling Time are used for quantitative comparative performance analysis.

Improved Smith predictor control for fast steering mirror system

In this paper, a novel Smith predictor control strategy improved by a high bandwidth inner loop for fast steering mirror (FSM) tracking control system based on a charge-coupled device (CCD) and rate sensor is proposed. A high bandwidth velocity closed-loop constructed by a fiber-optic gyroscope is utilized to provide a robust controlled plant for the Smith predictor controller. Usually, due to the mechanical resonances and time delay induced by a low CCD sampling rate, the tracking performance of FSM system is insufficient when suffering uncertain input command. Therefore, the Smith predictor control, which is famous for its delay-free characteristic and suitable for regulating systems with an excessively long time delay, is recommended to compensate for the CCD time delay. However, the classical Smith predictor is sensitive to plant parameter variations, which could deteriorate the stability of the control system. Thus, in order to make a robust Smith predictor, a cascaded dual closed-loop including a high bandwidth velocity inner loop is introduced to reduce the influence of plant parameter variations. The low sensitivity to parameter variation of this method shows the significant improvement of the conventional Smith predictor control. Simultaneously, the analysis of tracking accuracy and the bandwidth of the FSM system is also presented. A series of comparative experimental results demonstrate that the tracking performance of the FSM control system can be effectively improved by the proposed approach.

Performance Study of Distributed Power Control Algorithms Under Time-Delays and Measurement Uncertainty

This paper is aimed to evaluate different distributed power control algorithms for code division multiple access (CDMA) systems. The evaluation scenarios consider three practical aspects: i) time-varying channels, ii) feedback time-delays, and iii) uncertainty in the measurement of the signal to interference-noise ratio (SINR). First, dynamic power control is formulated in its general form as a tracking problem for an objective SINR and by assuming a feedback structure. Next, seven distributed power control algorithms are described: fixed step, Foschini-Miljanic, proportional-integral-derivative (PID) control, robust control H_infinity, robust Smith predictor, variable structure control and linear quadratic Gaussian (LQG) control. The analysis and implementations were performed in simulation by using MATLAB. In our evaluation, the LQG control outperformed other strategies in terms of SINR tracking precision, robustness and complexity.

Stability of Networked Control Systems with Time-Varying Delays

A robust Smith predictor is proposed to compensate for the round trip delay of networked control systems (NCSs); An analytical TCP model is adopted. We show that stability of the closed-loop system is guaranteed up to some maximum upper bound of the round trip delay

Design of a vehicle steering assist controller using driver model uncertainty

Single vehicle road departure (SVRD) accidents lead to over 1/3 of highway fatalities in the United States. A steering assist controller to reduce SVRD accidents is proposed. Previous studies using driving simulator data illustrate that the parametric uncertainty can represent the change in driver steering behaviour during long driving task. The uncertainty results show that occasionally the driver can perform very poorly. A serial steering control approach is investigated. The controller is used to attempt robust performance under the influence of driver uncertainty. A robust Smith predictor controller is employed to handle the delay in the driver model. The results indicate that the poor stability situations are successfully avoided and robust stability is achieved. However, due to large variations in driver behaviour, robust performance is not achieved. An adaptive version of the robust Smith predictor controller is shown to reduce the uncertainty in the driver model. The designed controllers are evaluated using frequency domain analyses and computer simulations.

A robust Smith predictor modified by internal models for integrating process with dead time

The internal model principle and control together (IMPACT) structure of the Smith predictor is proposed. The structure constructively achieves both the robust stability and absorption of external disturbances. In the structure design, the absorption principle is applied to enable the rejection of arbitrary class of deterministic disturbances and/or to suppress the effects of low frequency stochastic external signals on the system output. It is shown that the tuning of IMPACT structure is extremely simple due to relatively small number of tuning parameters all having clear physical meanings. The presented results of the simulation runs demonstrate the design procedure and illustrate the efficiency of the structure in disturbance absorption.

Robust Smith Predictor Design via Uncertainty Quantification: Application to a Reclaimer

The Smith predictor is a type of compensator that eliminates a time-delay occurred in industrial processes. Recently, the robustness in of the Smith predictor has been great issue. In this paper, a robust Smith predictor design is investigated. In this paper, the system identification method is used to find out a nominal model and its uncertainty bound of the nominal model is quantified in the frequency domain through the uncertainty quantification method. In addition, a robust criterion for the Smith predictor is also derived. With the obtained nominal model, uncertainty bound and the robust criterion derived, a robust Smith predictor is designed. This designed robust Smith predictor is applied to a reclaimer, which has a large output time-delay and is used in the raw yard of a steel plant. The performance of the designed robust Smith predictor is verified through the experiments and the simulations.

Traditional and Robust Predictor-Based Control for Mixing Systems in Cement Plants

This paper presents a rational matrix represented model of homogenizing processes and their disturbances in a cement plant and also general features as a multivariable stochastic system. A control method and actually applied results are presented, which is composed of PI-controllers with Smith predictors with an optimum mixing calculation. From robustness performances necessary for the process, this paper also reports performance comparison results by simulation experiments when applying a robust Smith predictor based two-degree of freedom controller with the traditional control and also with the extended horizon adaptive control.

Robust time-delay control of a reclaimer

In this paper, a robust time delay control for a reclaimer is investigated. Supplying the same amount of raw material throughout the reclaimation process, from the raw yard to a sinter plant, is important to keep the quality of the molten steel uniform. As the parameter values of the reclaimer are not available, the boom rotational dynamics. is modeled as a second order differential equation with unknown coefficients. The unknown parameters in the nominal model are estimated using recursive estimation method. Another important factor in the control problem of a reclaimer is the large time delay in output measurement. Assuming a multiplicative uncertainty, that accounts for both the unstructured uncertainty neglected in the modeling and the structured uncertainty in the parameter estimation, a robust Smith predictor is designed. A robust stability criterion for the multiplicative uncertainty is derived. Following the work of Goodwinet al. (1992), a quantifying procedure of the multiplicative uncertainty bound, through experiments, is described. Experimental and simulation results are provided.

Reclaimer Control: Kinematic Analysis, Modeling, Identification, and a Robust Smith Predictor

The reclaimer is a type of industrial equipment that excavates and transports the raw materials like coal and iron ore in the raw yard of a steel company. In this paper, as a part of reclaimer automation, an inverse kinematics problem and a robust time delay control are investigated. Analyzing a job task in the field, a closed-form solution of the inverse kinematics problem is provided. A nominal plant model, for the purpose of control system design, with unknown parameters is introduced. The unknown parameters in the nominal model are estimated with a recursive least squares estimation method. One obstacle in obtaining a good control performance is a large output delay due to the non-collocation of an actuator and a sensor. In this paper, in the presence of both structured and unstructured uncertainties in the nominal model and with large time delay, a robust Smith predictor is designed. A robust stability criterion with an uncertainty is derived, and a procedure of quantifying the uncertainty bound that is allowed in the nominal model of the reclaimer is described. Experimental and simulation results are provided.