Robustness and sensitivity of Smith predictor controllers for time-delay systems

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University, Dept. of Control Engineering , Sheffield
Statementby D. H. Owens, H. M. Wang and A.Chotai.
SeriesResearch report / University of Sheffield. Department of Control Engineering -- no. 238, Research report (Universityof Sheffield. Department of Control Engineering) -- no.238.
ContributionsWang, H. M., Chotai, A.
ID Numbers
Open LibraryOL13955020M

Of time delay sys tems The well known Smi th extensions are often used in this case. Re cent subject of the control predictor and its work pays particular attention to the robustness of the Smith predictor scheme to copy with the plant/model mismatch and to retain stability in the presence of the changes in plant dynamics.

Abstract. A new method for robust fixed-order controller design for uncertain time-delay systems is presented. It is shown that the robust performance condition can be represented by a set of convex constraints with respect to the parameters of a linearly parameterized primary controller in the Smith predictor by: 3.

The proposed approached allows one to design PI/PID as well as higher order primary controllers in the Smith Predictor structure which provide robust H performance for systems with uncertain deadtime and multiplicative or multimodel uncertainty in the dead-time free model of the by: 7. Robust Smith Predictor Design for Time-Delay Systems with H primary controller in the Smith predictor structure.

Systems with uncertain dead-time and Section IV the results are extended to unstable time-delay systems. Gain-scheduled SP is designed for ytheconcludingremarks. mance superior to the Smith predictor. When the process time-delay varies, even Smith predictor controllers with modest MS values tend to destabilise.

Description Robustness and sensitivity of Smith predictor controllers for time-delay systems EPUB

No reason are found for utilising a Smith predictor PI or PID controller over a Pareto optimal PI or PID controller. One will have to tune the Smith predic. Robust design of Smith predictor for a delay margin based on maximum sensitivity Ogunnaike, B.A.

and Ray, W.H. () Process Dynamics Modeling and Control, Oxford University Press, New York. Recently, there have been significant developments in robust control of time-delay systems.

This volume presents a systematic treatment of robust control for such systems in the frequency domain. The emphasis is on systems with a single input or output delay, although the delay-free part of the Unified Smith Predictor. Pages : Springer-Verlag London. Robust Control of Time-delay Systems is self-contained and will interest control theorists, researchers and mathematicians working with time-delay systems and engineers looking to design commercial controllers or to use them in plants, biosystems or communication systems with time delays.

Its methodical approach will also be of value to graduates. lay free system and a pure time-delay. There have been several partially successful attempts to generalize the Smith predictor for the control of MIMO systems, all using the structure in Figure 1.

In [3,4], it was assumed that all delays in each input-output channel were equal. In [5] a delay is associated with each sensor, i.e. closed-loop time constant (τc), a guideline is provided over a broad range of time-delay/time-constant ratios on the basis of the peak.

of maximum sensitivity (Ms). An analysis has been performed for the uncertainty margin with the different process parameters for the.

robust controller design. If a time delay is introduced into a well. tuned system, the gain must be reduced to. maintain stability [l]. The Smith predictor control scheme can help overcome this limitation and allow larger gains [2], but it is critical that the model parameters ex- actly match the plant parameters [ The objective is fast and tight control of processes with dead times.

A dead time can be recognized by the observation that after a step excitation of the manipulated variable there is no reaction of the controlled variable at all for a certain time (the dead time).File Size: KB.

There is now an extensive literature on the subject of the control of time-delay systems (1).

Details Robustness and sensitivity of Smith predictor controllers for time-delay systems PDF

The well known Smith predictor (2) and its extensions are often used in this case. Recent work pays particular attention to the robustness of the Smith predictor scheme (3) to copy with plant/model mismatch and to retain stability in the presence of Author: D.H.

Owens, H.M. Wang and A. Chotai. A method is outlined for designing Smith predictor controllers that provide robust performance despite real parameter uncertainties in the process model. Insight into the design process is gained by viewing the Smith predictor from the Cited by: The original proposals to deal with time-delay systems suffer from robustness problems and implementation issues (a good survey can be found in [9]).

In [10] a discrete predictor for continuous-time plants with time delay is proposed, and the closed-loop stability is proved. Fig. 1: Smith predictor control loop. literature for removing the destabilizing effects of time-delay in control loops [1]. In this method the attempt is to remove the time-delay parameter effect from the open loop transfer function or from the input signal to the controller.

Keywords: Time-delay systems, robust stability, congestion control, Smith predictor 1. Introduction Time delays are often present in feedback control systems due to reasons such as the transport of material or information.

From the control theoretic point of view, it is well-accepted that, quite often, an increase of the time delay may lead to. It is well known that classical analog Smith Predictor is not suitable for control of unstable and integrating time-delay processes. The designed digital LQ Smith Predictor eliminates this drawback.

The paper is organized in the following way.

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The general problem of a control of the time-delay systems is described in Section Size: KB. controllers are usually not effective for this kind of real systems []. The standard Smith predictor (SP), and its many extensions, can be considered as the first control method for the long time delay system.

The main advantage of the SP is that the time delay is eliminated from the characteristic equation of the closed loop Size: KB. It then compares this prediction yp with the desired setpoint ysp to decide what adjustments are needed (control u). To prevent drifting and reject external disturbances, the Smith predictor also compares the actual process output with a prediction y1 that takes the dead time into account.

v ABSTRACT The internal model control (IMC) philosophy relies on the internal model principle, which states that control can be achieved only if the control system encapsulates, either.

The authors present solutions of the (robust) stability analysis and stabilization problem of linear time-delay systems, which are the result of this cross-fertilization of control theory, numerical linear algebra, numerical bifurcation analysis, and optimization.

Smith predictor is an effective method to control the process, because the time delay is fixed. Nevertheless, the Smith predictor has the inherent drawback that its performance is sensitive to the process model uncertainty, especially to the time delay.

If a process model deviates from the process dynamics the system performance deteriorates. The Smith predictor (invented by O. Smith in ) is a type of predictive controller designed to control systems with a significant feedback time delay.

The idea can be illustrated as follows. Suppose the plant consists of followed by a pure time delay. refers to the Z-transform of. 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 Cited by: 5. Astrom et al. have proposed a new Smith predictor to control the process with an integrator and a long time delay. Though the method provides significant performance improvement, it fails to give effective tuning rules even when the integral constant is equal to 1.

In this paper the method is extended to the general integrator/time delay by:   In this paper, we examine a design method for modified Smith predictors for non-minimum-phase time-delay plants with multiple feedback-connected time-delays.

The Smith predictor is proposed by Smith to overcome time-delay and known as an effective time-delay compensator for a plant with large time-delay.

The Smith predictor by Smith cannot be used Cited by: 1. control delay systems ’ ISBN mathematicians who work in the area of control and time-delay systems. The book is divided into two parts:ControllerDesign (Chapters 2–10)and incorporating a modified Smith predictor (MSP). A practical issue, a numerical problem with the MSP, is discussed in.

Robust Control in Power Systems deals with the applications of new techniques in linear system theory to control low frequency oscillations in power systems.

The book specifically focuses on the analysis and damping of inter-area oscillations in the systems which are in the range of Hz. The. An improved cascade control structure with a modified Smith predictor is proposed for controlling open-loop unstable time delay processes. The proposed structure has three controllers of which one is meant for servo response and.

within the context of non-minimum state space (NMSS) control system design methodology is directly equivalent, under certain non-restrictive pole assignment conditions, to the equivalent digital Smith predictor (SP) control system for time delay systems.

This allows SP controllers to be considered within the context of NMSS state variable File Size: KB.A two-degree-of-freedom control structure is proposed for a class of unstable processes with time delay based on modi ed Smith predictor control; the superior performance of disturbance rejection and good robust stability are gained for the system.

e set.In this revised edition, the authors make the leap from stabilization to the design of robust and optimal controllers and from retarded-type to neutral-type delay systems, thus enlarging the scope of the book within control; include new, state-of-the-art material on numerical methods and algorithms to broaden the book s focus and to reach Cited by: