Showing papers on "Smith predictor published in 2004"

Wide-area measurement-based stabilizing control of power system considering signal transmission delay

Abstract: Recent technological advances in the area of wide-area measurement systems (WAMS) has enabled the use of a combination of measured signals from remote locations for centralized control purpose. The transmitted signals can be used for multiple swing mode damping using a single controller. However, there is an unavoidable delay involved before these signals are received at the controller site. To ensure satisfactory performance, this delay needs to be taken into account in the control design stage. This paper focuses on damping control design taking into account a delayed arrival of feedback signals. A predictor-based H/sub /spl infin// control design strategy is discussed for such time-delayed systems. The concept is utilized to design a WAMS-based damping controller for a prototype power system using a static var compensator. The controller performance is evaluated for a range of operating conditions.

Robust bilateral control with Internet communication

Abstract: Smith predictor is a well-known method for compensating time delay in control systems. Therefore, it has been applied to many systems with time delay so far. However, delay time should be estimated precisely in this method. So, if time delay is fluctuant and unpredictable, like the communication delay over the Internet, performance of Smith predictor deteriorates. This paper proposes "Communication Disturbance Observer". It regards the error caused by time delay as disturbance torque (or acceleration), then it can observe and compensate the error. Furthermore, it doesn't need to estimate the value of delay time; therefore it can be applied to control systems with fluctuant and unpredictable time delay. It can be said that control system with "Communication Disturbance Observer" is robust to time delay and fluctuation of that. Effectiveness and robustness of proposed method is shown by result of simulation and experiment. In experiment, master-slave manipulator was used over the Internet. We were able to get the sense of touch from the environment of remote site.

Optimal linear filtering over observations with multiple delays

Abstract: In this paper, the optimal filtering problem for a linear system over observations with multiple delays is treated proceeding from the general expression for the stochastic Ito differential of the optimal estimate and its variance. As a result, the optimal filtering equations similar to the traditional Kalman–Bucy ones are obtained in the form dual to the Smith predictor, commonly used for robust control design in time-delay systems. In the example, the obtained optimal filter over observations with multiple delays is verified for a sample system and compared with the best Kalman–Bucy filter available for delayed measurements. Copyright © 2004 John Wiley & Sons, Ltd.

Quantitative Performance Design of a Modified Smith Predictor for Unstable Processes with Time Delay

Abstract: The existence of both right-half-plane poles and time delay makes it difficult to obtain a higher control quality. Recently, a modified Smith predictor for unstable processes with time delay was presented and good performance was obtained. In this paper, the modified Smith predictor is discussed. A modified structure is presented. The new one not only is simple for analysis and design but also avoids the improper element. Instead of introduction of an inner loop, a direct design procedure is given and analytical formulas for the controllers are provided. The time domain performance for both trajectory and regulatory responses is obtained quantitatively. Sufficient and necessary conditions for robust stability are also given. The new structure and design method can also be used for the control of integrating processes with time delay and stable processes with time delay. Numerical examples are provided to illustrate the proposed method.

Power control of cellular radio systems via robust Smith prediction filter

Abstract: In this paper, a robust Smith prediction filter is proposed for power control design of direct-sequence code-division multiple-access cellular mobile radio systems. Due to the type-I (integrator) structure in the close loop, we first show that zero steady-state tracking error of the averaged received signal-to-noise plus interference ratio (SINR) with respect to a constant target SINR can be ensured. Next, with the Smith predictor to compensate round trip delay, a fixed-order robust H/sub /spl infin// loop filter is developed by using the genetic algorithm to minimize the worst-case variance of the received SINR from the minimax perspective. Using the proposed robust control approach, the statistics of the fading and interference are not needed in the design procedure. To confirm the performance of the proposed method, several simulation results are given in comparison with other methods.

A control theoretical approach to congestion control in packet networks

Abstract: In this paper, we introduce a control theoretical analysis of the closed-loop congestion control problem in packet networks. The control theoretical approach is used in a proportional rate controller, where packets are admitted into the network in accordance with network buffer occupancy. A Smith Predictor is used to deal with large propagation delays, common to high speed backbone networks. The analytical approach leads to accurate predictions regarding both transients as well as steady-state behavior of buffers and input rates. Moreover, it exposes tradeoffs regarding buffer dimensioning, packet loss, and throughput.

Exploring strategies for closed-loop cavity flow control

Abstract: One of the current three main thrust areas of the Collaborative Center of Control Science (CCCS) at The Ohio State University is feedback control of aerodynamic flows. Synergistic capabilities of the flow control team include all of the required multidisciplinary areas of flow simulations, low-dimensional and reduced-order modeling, controller design, and experimental integration and implementation of the components along with actuators and sensors. The initial application chosen for study is closed-loop control of shallow subsonic cavity flows. We have made significant progress in the development of various components necessary for reduced-order model based control strategy, which will be presented and discussed in this paper. Stochastic estimation was used to show that surface pressure measurements along with the reduced-order model based on flow-field variables can be used for closed-loop control. Linear controllers such as H ∞ , Smith predictor, and PID were implemented experimentally with various degrees of success. The results showed limitations of linear controllers for cavity flow with inherent nonlinear dynamics. Detailed experimental work further explored the physics and showed the highly non-linear nature of the cavity flow and the effects of forcing on the flow structure.

Smith predictor based-sliding mode controller for integrating processes with elevated deadtime.

Abstract: An approach to control integrating processes with elevated deadtime using a Smith predictor sliding mode controller is presented. A PID sliding surface and an integrating first-order plus deadtime model have been used to synthesize the controller. Since the performance of existing controllers with a Smith predictor decrease in the presence of modeling errors, this paper presents a simple approach to combining the Smith predictor with the sliding mode concept, which is a proven, simple, and robust procedure. The proposed scheme has a set of tuning equations as a function of the characteristic parameters of the model. For implementation of our proposed approach, computer based industrial controllers that execute PID algorithms can be used. The performance and robustness of the proposed controller are compared with the Matausek-Micic scheme for linear systems using simulations.

A unified Smith predictor based on the spectral decomposition of the plant

Abstract: We point out a numerical problem in the well-known modified Smith predictor and propose a unified Smith predictor (USP) which overcomes this problem. The proposed USP combines the classical Smith predictor with the modified one, after a spectral decomposition of the plant. We then derive an equivalent representation of the original delay system, together with the USP. Based on this representation, we give a controller parameterization and we solve the standard H 2 problem.

Advances in Communication Control Networks

Abstract: Stochastic Fluid Models For the On-line Control of Communication Networks.- Stability Analysis of Window Flow Control.- H-infinity and LMMSE Based Capacity Predictors for Flow.- Control in Communication Networks.- Models and Methods for Analyzing Congestion Control and Active Management Schemes.- Delay Effects on the Stability of Various Fluid Models Encountered in High-speed Networks.- Decentralized Track Engineering in the Internet: A Sliding Mode Approach.- Modeling the Internet Congestion Control Using the Smith Predictor and Input Shaping.- Saturated Controller Design of an ABR Explicit Rate Algorithm for ATM Switches.- State-space Models for Control and Identification.- Global Stability of Nonlinear Congestion Control with Time-Delay.- On the Optimization of Load Balancing in Distributed Networks in the Presence of Delay.- Bounds on Achievable Performance of Load Balancing Algorithms for Parallel Computations.- On Position Tracking in Bilateral Teleoperation.- Suboptimal Control Techniques for Hybrid Systems Operating via Networks.- Communication Requirements for Networked Control.- A New Approach to Fault Diagnosis, with an Application to Demodulation.

Varying time delay Smith predictor process controller.

Abstract: One of the perceived weaknesses of the classical Smith predictor is that the time delay is fixed. For systems with a varying time delay, underestimating or overestimating the time delay significantly degrades control quality. This paper presents theoretical and practical results of applying the Smith predictor with a varying time delay when the nature of the application allows the time delay to be practically computed in real time.

A control strategy for energy optimal operation of a direct district heating system

Abstract: A dynamic model of a direct district heating system (DDHS) is developed, and an energy optimal control strategy is designed. The DDHS is characterized as a system with long transport time delay. The use of a Smith predictor (SP) to deal with this type of time delay is explored. An SP is designed by using the reduced-order dynamic model and implemented on the full-order model. Also, optimal set point profiles of supply water temperature as a function of outdoor air temperature have been determined. The simulation results show that the SP works effectively in disturbance rejection compared with the nominal control design. The use of optimal set point control strategy resulted in energy savings of the order of 19–32% when the influence of internal load was considered. Copyright © 2004 John Wiley & Sons, Ltd.

GMV control of nonlinear multivariable systems

Abstract: A Generalized Minimum Variance control law is derived for the control of nonlinear, possibly time-varying multivariable systems. The solution for the control law is original and was obtained in the time-domain using a simple operator representation of the process. The quadratic cost index involves both error and control signal costing terms. The controller obtained is simple to implement and includes an internal model of the process. In one form might be considered a nonlinear version of the Smith Predictor. However, unlike the Smith Predictor a stabilizing control law can be obtained even for some open-loop unstable processes

Controller design for active closed-loop control of cavity flows

Abstract: In this paper we discuss feedback controller design issues for active control of shallow cavity flows. Linear controllers, such as H ∞ , PID, and Smith predictor based controllers are designed and tested experimentally. The ineffectiveness of using fixed linear models in the design of linear controllers for the cavity flows is demonstrated via experimental results. In order to better address this problem, we are in the process of developing a nonlinear model of the cavity flow dynamics using Proper Orthogonal Decomposition (POD). We briefly discuss control issues related to the class of feedback systems involving this type of nonlinear plants.

Loop Shaping for Transparency and Stability Robustness in Time-Delayed Bilateral Telemanipulation

Abstract: This paper presents a control methodology that provides transparency and stability robustness in bilateral telemanipulation systems that include a significant time delay in the communication channels. The method utilizes an adaptive Smith predictor to compensate for the time delay, and incorporates a previously published loop shaping approach to design a compensator for transparency and stability robustness of the loop. The method is experimentally demonstrated on a single degree-of-freedom telemanipulation system, and is shown to effectively provide stability and performance robustness.

Engine delay compensation

Abstract: An engine with inertial integration and delay is controlled through the use of a disturbance estimator. Control logic includes a feed-forward control path driving a control input with a control signal. The feed-forward control path is designed to provide closed-loop control of the controlled parameter without the presence of transport delay. The disturbance estimator generates an estimate of the engine disturbance. A Smith predictor generates a compensation signal for the feed-forward control path based on the control signal and the engine disturbance estimate.

Control of Systems with Input Delay—An Elementary Approach

Abstract: The stabilization by feedback control of systems with input delays may be considered in various frameworks; a very popular is the abstract one, based on the inclusion of such systems in the Pritchard-Salamon class. In this chapter we consider the elementary approach based on variants of the Smith predictor, make a system theoretic analysis of the compensator and suggest a computer control implementation. This implementation is based on piecewise constant control which associates a discrete-time finite dimensional control system; it is this system which is stabilized, thus avoiding unpleasant phenomena induced by the essential spectrum of other implementations

Fractional-order boundary control of fractional wave equation with delayed boundary measurement using Smith predictor

Abstract: In this paper, we consider boundary control of a fractional order wave equation. Both integer order and fractional order boundary control laws are investigated. When delayed boundary measurements are used for boundary control, the Smith predictor is applied. Through extensive hybrid symbolic and numerical simulation, combined with parameter optimization, for the first time, we confirmed that (1) small time delay in boundary control law can destabilize the controlled system; (2) the Smith predictor can compensate the delay effect; and (3) fractional order boundary control can outplay its integer counterpart in terms of transient performance.

Application of kalman filter algorithms in a gmc control strategy for fed-batch cultivation process

Abstract: This paper addresses the study of a Generic Model Control (GMC) approach for regulation of the specific growth rate of for fed-batch cultivation process. This approach requires all the process states to be available on line. Since direct measurement of these states is not possible, a state estimator must be implemented. In this work, the estimator is a Kalman filter that uses the oxygen uptake rate (OUR) of the microorganisms as the measurable process output. Another practical issue constitutes the time delay present in the OUR measurements, a Smith predictor compensation is proposed to overcome this problem. Several simulations were carried out to test this scheme using an experimentally identified process model.

Modified Smith predictor design for periodic disturbance rejection

Abstract: In this paper, a simple yet effective modified Smith predictor control scheme is proposed for periodic disturbance rejection. With sound set point response, the closed-loop regulation performance is enhanced significantly with respect to periodic disturbances, provided that the period of the disturbance and the system time delay can be detected. Internal stability is analyzed explicitly. The effectiveness is demonstrated by simulations.

Robust stability of approximate Smith predictor control systems

Abstract: This paper clarifies the mechanism of weakness of Smith predictor control about robust stability to the delay mismatch. The approximate Smith predictor is introduced to remove the cause. The sufficient condition for robust stability of the approximate Smith predictor control is proved. It is shown that the stability area becomes wider in comparison with the original Smith predictor.

Control for integrating processes based on new modified smith predictor

Abstract: This paper presents a new modified Smith Predictor called Cascade Smith Predictor (CSP) to control the integrating processes with long dead-time, CSP has two Smith Predictors. The inner predictor keeps the actual process stable and converts the integrating process into a stable one, while the outer smith predictor reject the load disturbance. Combined with a good tuning rule introduced in this paper, the CSP control structure only need to adjust one parameter to control the integrating processes with long dead-time, which make CSP show better performance than that of other Smith predictors.

Hot Strip Laminar Cooling Control Model

Abstract: The control model of laminar cooling system for hot strip, including air-cooling model, water-cooling model, temperature distribution model along thickness direction, feedforward control model, feedback control model and self-learning model, was introduced. PID arithmetic and Smith predictor controller were applied to feedback control. The sample of model parameter classification was given. The calculation process was shown by flow chart. The model has been proved to be simple, effective and of high precision.

Hot Strip Laminar Cooling Control Model

Abstract: The control model of laminar cooling system for hot strip, including air-cooling model, water-cooling model, temperature distribution model along thickness direction, feedforward control model, feedback control model and self-learning model, was introduced. PID arithmetic and Smith predictor controller were applied to feedback control. The sample of model parameter classification was given. The calculation process was shown by flow chart. The model has been proved to be simple, effective and of high precision.

Single-neuron PSD adaptive control based-on Smith predictor for the main steam temperature

Abstract: The main steam temperature process is regarded as a controllable process with large dead time and immeasurable disturbances. A new single-neuron PSD self-adaptive algorithm that based on Smith predictor was proposed, i.e., a compound controller was combined with Smith predictor and single-neuron PSD self-adaptive controller. Compared with conventional PID controller, the results of simulation show that the system has favorable dynamic properties and good adaptability. The variety of main steam temperature can be maintained in a very small range and it can manipulate variable changes smoothly under large-scale variety of load. Therefore, the scheme has promising application prospects.

Digital redesign of analog smith predictor for systems with input time delays.

Abstract: This paper presents a new methodology for digitally redesigning an existing analog Smith predictor control system, such that the cascaded analog controller with input delay can be implemented with a digital controller. A traditional analog Smith predictor system is reformulated into an augmented system, which is then digitally redesigned using the predicted intersampling states. The paper extends the prediction-based digital redesign method from a delay free feedback system to an input time-delay cascaded system. A tuning parameter v is optimally determined online such that in any sampling period, the output response error between the original analogously controlled time-delay system and the digitally controlled sampled-data time-delay system is significantly reduced. The proposed method gives very good performance in dealing with systems with delays in excess of several integer sampling periods and shows good robustness to sampling period selection.

Position Controller And Controlling Method for Time Delay Compensation of the Image Tracker in Electro-Optical Tracking System

Abstract: PURPOSE: A time delay compensating controller of an image tracker in an electro-optical tracking system(EOTS) and a control method thereof are provided to construct a smith predictor for operating independently relating to an input command and a disturbance input within a loop, thereby controlling effectively the input command follow-up and disturbance compensation function. CONSTITUTION: An image sensor unit(230) is comprised of a subtraction unit(211) for subtracting a chase output signal(y) from the input command. A quantizer(212) quantizes the output of the subtraction unit(211). An image processing unit(220) is comprised of an adder unit(221) for adding the output of the image sensor unit(210) to a quantization error signal(n), a sampling period unit(222) and a laplace converting unit(223) of an image process time delay. A control input(u) and a disturbance(d) of a position controller(240) are added in the adder unit(250) and inputted it to a chase loop. A stabilization drive unit(230) outputs an output signal(y) of a chaser.

Boundary Control of Wave Equations with Delayed Boundary Measurement

Abstract: The Smith predictor and its variant are applied to boundary control of a wave equation with delayed boundary measurement. The well-known instability problem due to a small time delay is solved for wave equations. Simulation results demonstrate the effectiveness of the proposed method. The effect of the time delay size and the boundary feedback gain has also been demonstrated