Showing papers on "Smith predictor published in 2009"
TL;DR: In this paper, a unified approach for the design of dead-time compensators is presented based on a modified structure of the Smith predictor that allows to decouple the disturbance and set-point responses in order to tune the controller for a compromise between performance and robustness and is able to cope with unstable processes.
227 citations
TL;DR: Two different methods for the control over a network, adaptive Smith predictor approach and robust control based approach, which are imposed by the accessible information about the network are proposed.
104 citations
TL;DR: In this article, the authors proposed a new methodology to design fractional integral controllers combined with Smith predictors, which are robust to high frequency model changes, in particular, special attention is paid to time delay changes.
89 citations
TL;DR: In this article, the authors proposed a new strategy for the control of water distribution in an irrigation main canal pool characterized by large time-varying time delays using fractional order PI controllers combined with Smith predictors that yield control systems which are robust to changes in the process time delay.
65 citations
TL;DR: In this article, an analytical PID design method is presented based on a general controller evaluation method, taking both performance and robustness in different frequency regions into account, and the proposed method, called robust IMC, gives the user the important freedom to control both mid and high-frequency robustness.
Abstract: Based on a general controller evaluation method, taking both performance and robustness in different frequency regions into account, an analytical PID design method is presented. It is related to the well known and often used lambda tuning approach, which is based on internal model control (IMC) for a specific second-order non-minimum phase plant model. The analytical method introduced in this paper includes two tuning parameters, one that guarantees a specified stability margin for the given model, and one that is also able to adjust the control activity to a desired level. The suggested method, called robust IMC, gives the user the important freedom to control both mid- and high-frequency robustness. An extended evaluation procedure also illustrates how efficiently PI and PID controllers including a Smith predictor (SP) can control time delayed plants. More specifically, it is shown to be more profitable to provide a PI controller with derivative action than with a SP for plants with long time delays.
60 citations
TL;DR: In this article, a feedback linearization strategy for a solar collector field, which is a constrained nonlinear processes, is proposed to take advantage of linear control without losing the intrinsic nonlinearities typical of thermal power plants.
57 citations
TL;DR: In this paper, the analysis of the Smith predictor structure for multiple input multiple output (MIMO) systems with uncertain multiple delays is presented, where the uncertainty structure can also accommodate the dynamic uncertainty of the rational part as well.
46 citations
TL;DR: The scattering transformation is applied to NCS, for the first time, in order to guarantee stability in the presence of unknown constant time delay, and it is shown that no knowledge of the time delay value is necessary for the analysis and design of the closed-loop system.
Abstract: In a networked control system (NCS), the plant and the controller are spatially separated and the control loop is closed through a communication network. Communication time delay in an NCS degrades the performance and may lead to instability. In this paper, the scattering transformation is applied to NCS, for the first time, in order to guarantee stability in the presence of unknown constant time delay. The scattering transformation approach in its original version relies on the assumption that all subsystems are passive. This paper extends the approach to nonpassive, static-output-feedback-stabilizable plants. We consider linear time-invariant (LTI) systems here. It is furthermore shown that no knowledge of the time delay value is necessary for the analysis and design of the closed-loop system. Lastly, experimental validation shows that the proposed approach is superior to a delay-dependent controller and the Smith predictor, as far as stability, performance, and sensitivity to time delay are concerned.
44 citations
TL;DR: The control methods proposed here are based in the use of proportional integral controllers with dead-time compensation to avoid undesirable oscillations in the BIS signal during the process.
Abstract: This paper presents an efficient computer control technique for regulation of anesthesia in humans. The anesthetic used is propofol and the objective is to control the degree of hypnosis of the patient. The paper describes the basic hardware/software setup of the system and the closed-loop methodologies. The bispectral index (BIS) is considered as the feedback signal. The control methods proposed here are based in the use of proportional integral controllers with dead-time compensation to avoid undesirable oscillations in the BIS signal during the process. The compensation is based on the Smith predictor. To guarantee the applicability of the method to different patients, an adaptive module to tune the compensator is developed. Some real and simulated results are presented in this work to attest the efficiency of the methods used.
37 citations
TL;DR: A delay compensator has been incorporated in the primary loop of the parallel cascade control system, which provides robust control performances and significant improvement in the closed loop performances are obtained with the Delay compensator.
Abstract: Parallel cascade controllers are used in chemical processing industries to improve the dynamic performance of a control system in the presence of disturbances In the present work, a delay compensator has been incorporated in the primary loop of the parallel cascade control system The secondary controller is designed using the internal model control (IMC) method The primary controller is designed based on a direct synthesis method for the delay-free system Design of controllers for slow (when the secondary loop dynamics is slow ie process contains poles sufficiently slower than the desired closed loop response) as well as fast dynamics (when the inner loop dynamics is fast ie process contains poles sufficiently faster than the desired closed loop response) of the secondary process is considered The method provides robust control performances Significant improvement in the closed loop performances are obtained with the delay compensator over that of a conventional parallel cascade control system Several case studies are considered to show the advantage of the proposed method when compared to other recently reported methods
35 citations
TL;DR: In this article, an interactive tool for dead-time compensator design is presented, which is based on an unified Smith predictor and considers models commonly used in industrial process control, including integrating and unstable systems.
TL;DR: This paper presents a simple cascade controller in the enhanced modified Smith predictor structure for control of open loop unstable cascade processes with/without zero that gives significant disturbance rejection both in the inner and outer loops.
Abstract: This paper presents a simple cascade controller in the enhanced modified Smith predictor structure for control of open loop unstable cascade processes with/without zero. The proposed structure cons...
TL;DR: A fully linearizable single-input-single-output relative-degree n system with an output time delay is considered and good output tracking results are obtained.
Abstract: A fully linearizable single-input-single-output relative-degree n system with an output time delay is considered in this paper. Using the approach of Pade approximation, system center approach, and second-order sliding-mode (SM) control, we have obtained good output tracking results. The Smith predictor is used to compensate the difference between the actual delayed output and its approximation. A second-order supertwisting SM observer observes the disturbance in the plant. A nonlinear example is studied to show the effect of this methodology.
TL;DR: The proposed strategy that uses the Smith predictor principle and delay information not only achieves synchronization but also preserves the natural local dynamics of each subsystem without being affected by the feedback nature of control.
Abstract: This paper addresses a new control strategy for synchronizing two or more distributed and interconnected dynamic systems having communication time delays. The proposed strategy that uses the Smith predictor principle and delay information not only achieves synchronization but also preserves the natural local dynamics of each subsystem without being affected by the feedback nature of control. The proposed synchronization scheme is generalized to cases that deal with an arbitrary number of heterogeneous interconnected systems through dynamic scaling of input under a ring-type network configuration. In addition, possibility of applying the proposed scheme to nonlinear systems is discussed. Simulation and experimental tests are conducted to validate theoretical results.
Journal Article•
Patent•
11 Feb 2009
TL;DR: In this article, a hydraulic AGC system of a rolling mill is described, and the system is connected to be formed in a manner of double closed loop of an inner-outer loop that is combined by an outer closed loop and an inner single closed loop.
Abstract: The invention discloses a hydraulic AGC system of a rolling mill, and a control method thereof, and the system is connected to be formed in a manner of double closed loop of an inner-outer loop that is combined by an outer closed loop and an inner single closed loop. A thickness measuring device is taken as a feedback element, a deviation signal of the feedback value of the thickness measuring device and a given thickness value is firstly input into a PID controller which is based on Smith predictor function and then is input into the PID controller in the inner single closed loop, the deviation signals of a position sensor, a pressure sensor, a tension sensor and the feedback value of an speed measuring device are input into the PID controller; the PID controller processes the signals by a control module, and a touch screen HMI device is used for setting and displaying the parameters of the system and operating and monitoring all the steps. As the strategy of the PID controller based on Smith predictor function is introduced in the invention, the feedback and response speed is fast, thus improving the control precision and stability of the system obviously. The system and the method have the advantages of simple installation and debugging, convenient operation and reliable running.
Journal Article•
TL;DR: The paper shows that the predictors designed to produce optimal open-loop predictions are not optimal when operating in closed loop and a new concept "Prediccion para Control" is introduced where predictors should be designed as an integral part of the controller in order to produce better closed-loop response.
Abstract: This paper presents an analysis of dead-time compensating controllers for processes exhibiting a dead time. The robustness and performance of several dead-time compensating control structures are analysed and the effect of the predictor on the closed-loop is studied. A unified approach is used considering ideas from “Model Pedictive Control” (MPC) and “Dead-time Compensators” (DTC). The main papers in the area are revised and the relationships between MPC and DTC are shown. The paper shows that the predictors designed to produce optimal open-loop predictions are not optimal when operating in closed loop. Furthermore, structures based on the Smith predictor offer more robust controllers and similar nominal performance even when the process exactly matches the situation required by optimal controllers. A new concept "Prediccion para Control" is introduced where predictors should be designed as an integral part of the controller in order to produce better closed-loop response.
TL;DR: This paper considers the identification and fuzzy controller design for nonlinear uncertain systems in presence of unknown input time- delay, and proposes a time-delay Takagi-Sugeno-Kang type fuzzy neural system and the Smith predictor compensation and dominate pole assignment technique for the fuzzy PID controller.
Abstract: This paper considers the identification and fuzzy controller design for nonlinear uncertain systems in presence of unknown input time-delay. Firstly, a time-delay Takagi-Sugeno-Kang (TSK) type fuzzy neural system (TDFN) is proposed to identify a class of nonlinear input time-delay systems. The input- output signals of nonlinear systems are used to identify the system dynamics and unknown time-delay, and then construct the system in the form TSK-fuzzy time-delay model. Each fuzzy rule has a corresponding linear system with an input time-delay as the consequent part. Based on parallel distribution compensation (PDC) approach, the Smith predictor compensation and dominate pole assignment technique are then adopted to design the fuzzy PID controller. Several simulations are shown to demonstrate the effectiveness and control performance of the proposed approach.
TL;DR: In this paper, a modification of the Exponentially Weighted Moving Average (EWMA) controller, called the Smith-EWMA run-to-run controller, is proposed, and a performance comparison with the recursive-least-square controllers under disturbance conditions based on simulation is conducted.
Abstract: The Exponentially Weighted Moving Average (EWMA) controller is a popular run-to-run controller in the semiconductor manufacturing industry. The controller adjusts input based on measurement information from previous runs. EWMA controllers can guarantee satisfactory results in many cases; however, when there is a measurement delay in the process, the stability properties and performance of the EWMA controller cannot be guaranteed. In order to maintain the satisfactory outcomes of EWMA controllers, a Smith predictor control scheme is introduced, created particularly for time delay systems in control theory, into EWMA controllers. A modification of the EWMA controller, called the Smith–EWMA run-to-run controller, is proposed. Comparisons between the stability properties of Smith–EWMA and EWMA run-to-run controllers are studied. Moreover, a performance comparison with the EWMA and recursive-least-square controllers under disturbance conditions based on simulation is conducted. The results show that when there...
TL;DR: This article presents a methodology for compensating for the time-delay effects in tele-operated control systems by replacing the linear estimator with a neural network whose structure is based on the radial basis function (RBF).
Abstract: This article presents a methodology for compensating for the time-delay effects in tele-operated control systems. Compensation can be carried out by a neural network. A tele-operated system consists of a master robot to give commands, and a slave robot to work with the environment. The positional command by the master robot is transferred to the slave robot, and the contact force from the environment is transferred back to the master robot. The structure of the Smith predictor is modified by replacing the linear estimator with a neural network whose structure is based on the radial basis function (RBF). The RBF network identifies the slave model to deal with the nonlinearities in the system. Simulation studies have been conducted, and experimental studies of one-directional force control were performed to confirm the simulation results.
TL;DR: A new Smith predictor based on single neural network PID (SNN-PID) is proposed, which can effectively compensate the delay effects and achieve better control performance than the conventional PID controller.
Abstract: Flatness is one of the most important criterion factors to evaluate the quality of the steel strip. To improve the strip’s flatness quality, the most frequently used methodology is to employ the closed-loop automatic shape control system. However, in the shape control system, the shape-meter is always installed at the down way of the exit of the cold rolling mill and can not sense the changes of the strip flatness in the rolling gap directly. This kind of installation results in the delay of the feedback in the control system. Therefore, the stability and response performance of the system are strongly affected by the delay. At present, there is still no mature way to design controllers for systems with time delay. Although the conventional PID controller used in most practical applications has the capability to compensate the delay, the effect of the compensation is limited, especially for the systems with long time delay. Smith predictor, as a compensator for solving this problem, is now widely used in industry systems. However, the request of highly precise model of the system and the poor adaptive performance to the changes of related parameters limit the application of the Smith predictor in practice. In order to overcome the drawbacks of the Smith predictor, a new Smith predictor based on single neural network PID (SNN-PID) is proposed. Because the single neural network is employed into the Smith predictor to improve the controller’s self-adaptability, the adaptive capability to the varying parameters of the system is improved. Meanwhile, for the purpose of solving the problems such as time-consuming and complicated calculation of the neural networks in real time, the learning coefficient of neural network is divided into several stages as usually done in expert control system. Therefore, the control system can obtain fast response due to the improved calculation speed of the neural networks. In order to validate the performance of the proposed controller, the experiment is conducted on the shape control system in a 300 mm four-high reversing cold rolling mill. The experimental results show that the SNN-PID with Smith predictor controller can effectively compensate the delay effects and achieve better control performance than the conventional PID controller.
TL;DR: In this paper, an intelligent frame to reduce the dasiaa priori' knowledge of the plant delays required in the design of SP controllers for multivariable systems is proposed and improved.
Abstract: One of the drawbacks of the Smith Predictor (SP) to control systems with external point delays is that its performance is strongly influenced by the knowledge of the time delay of the plant. Hence, as the mismatch between the actual delay of the plant and the nominal one used in the control structure increases, the closed-loop performance degrades accordingly, even potentially causing instability. This effect is particularly important when dealing with multivariable systems, where there is a coupling between input and output variables. In this paper, an intelligent frame to reduce the dasiaa priori' knowledge of the plant delays required in the design of SP controllers for multivariable systems is proposed. The intelligent frame is composed of a set of different plant delay models running in parallel along with a high level supervision algorithm which selects the one that best describes the actual delay of the plant at each time interval to be used for control purposes. In this way, the designer can design the control of the system based on its delay-free part while the appropriate tuning of the delay of the Smith Predictor is performed by the intelligent supervisor. As a consequence, like simulation examples show, the closed-loop performance of the system is improved without the dasiaa priori' requirement of an accurate knowledge of the value for the time delay.
18 Jul 2009
TL;DR: The results of simulation show validity of the control scheme that new Smith predictor combined with fuzzy adaptive controller for the NCS does not include network delay.
Abstract: In order to effectively restrain the impact of network delay, aiming to time-variant, random and uncertain network delays, a new approach is proposed that new Smith predictor combined with fuzzy adaptive controller for the NCS. Because new Smith predictor does not include network delay, therefore, the network delays no need to be measured or identified on line. Based on CSMA/AMP (CAN Bus), the results of simulation show validity of the control scheme.
TL;DR: In this article, the authors proposed a control strategy for a Diesel Oxidation Catalyst (DOC) which is grounded on a one-dimensional distributed parameter model, which accounts for spatially distributed heat generation due to oxidation of reductants.
TL;DR: This paper proposes a new method for automatic tuning of the Smith predictor controller based on a Repetitive Control (RC) approach which requires the input of a periodic reference signal which can be derived from a relay feedback experiment.
Abstract: This paper proposes a new method for automatic tuning of the Smith predictor controller based on a Repetitive Control (RC) approach. The method requires the input of a periodic reference signal which can be derived from a relay feedback experiment. A modified repetitive control scheme repetitively changes the control signal to achieve tracking error convergence. Once a satisfactory performance is achieved through the learning control, the parameters of the Smith predictor controller can be computed from the signals using a nonlinear least squares algorithm. The same relay feedback experiment can provide an initial parameter vector for an efficient implementation of the parameter estimation. Simulations and experimental results will be furnished to illustrate the effectiveness of the proposed tuning method.
13 Nov 2009
TL;DR: An output feedback controller that compensates the performance degradation owing to time-delay and input disturbance is presented and simulation results show the performance improvement by the proposed controller for reducing the both effects of time- delay andinput disturbance.
Abstract: Time-delay and input disturbance frequently occur in control systems, which decrease the pre-defined performance of the closed-loop system. This paper presents an output feedback controller that compensates the performance degradation owing to time-delay and input disturbance. Simple adaptive control (SAC) and a new disturbance observer (DOB) approaches have been combined to achieve the control purpose. It is shown that the closed-loop system can be made robust against uncertain time-delay by using the SAC algorithm. For disturbance attenuation a new DOB structure has been used for the non-minimum phase system caused by to the Pade approximation of time-delay. Simulation results show the performance improvement by the proposed controller for reducing the both effects of time-delay and input disturbance.
01 Jan 2009
TL;DR: In this article, the authors considered the study of a heat diffusion system based on the application of the fractional calculus concepts and investigated several control methodologies, namely, fractional PID and Smith predictor, and extensive simulations are presented assessing the performance of the proposed fractional-order algorithms.
Abstract: The differentiation of non-integer order has its origin in the seventeenth century, but only in the last two decades appeared the first applications in the area of control theory. In this paper we consider the study of a heat diffusion system based on the application of the fractional calculus concepts. In this perspective, several control methodologies are investigated namely the fractional PID and the Smith predictor. Extensive simulations are presented assessing the performance of the proposed fractional-order algorithms.
01 Mar 2009
TL;DR: In order to effectively restrain the impact of network delay for the networked control systems (NCS), a novel approach is proposed that new Smith predictor combined with non linear PID control for the NCS can adaptively tune parameters of the nonlinear PID controller.
Abstract: order to effectively restrain the impact of network delay for the networked control systems (NCS), a novel approach is proposed that new Smith predictor combined with nonlinear PID control for the NCS. This approach can adaptively tune parameters of the nonlinear PID controller. Because new Smith predictor hides predictor model of the network delay into real network data transmission process, further the network delay no longer need to be measured, identified or estimated on-line. Simultaneously this new Smith predictor doesn ' t include the prediction model of the controlled plant, thus it doesn't need to know the exact mathematical model of the controlled plant beforehand. It is applicable to some occasions that network delay is random, time-variant or uncertain, larger than one, even tens of sampling periods, and there are some data dropouts in closed loop. Based on CSMA/AMP (CAN bus), the results of the simulation show the validity of the control scheme.
08 Jul 2009
TL;DR: The Smith Predictor is a well-known method for designing controllers for plants with I/O delays, where the time delay known compensates the delay within the loop making it possible to design the controller just considering the (rational) delay-free part of the plant.
Abstract: The Smith Predictor is a well-known method for designing controllers for plants with I/O delays. Assuming the time delay known, this control configuration compensates the delay within the loop making it possible to design the controller just considering the (rational) delay-free part of the plant.