Showing papers on "Smith predictor published in 2007"

Control of dead-time processes

Abstract: Dead-time Processes.- Identification of Dead-time Processes.- PID Control of Dead-time Processes.- The Smith Predictor.- Dead-time Compensators for Stable Plants.- Dead-time Compensators for Unstable Plants.- Discrete Dead-time Compensators.- Model Predictive Control of Dead-time Processes.- Robust Predictive Control of Dead-time Processes.- Multivariable Dead-time Compensation.- Robust MPC for MIMO Dead-time Processes.- Control of Nonlinear Dead-time Processes.- Prediction for Control.

Backstepping boundary control for first order hyperbolic PDEs and application to systems with actuator and sensor delays

Abstract: We consider a problem of boundary feedback stabilization of first order hyperbolic partial differential equations (PDEs). These equations serve as a model for such physical phenomena as traffic flows, chemical reactors, and heat exchangers. We design controllers using a backstepping method, which has been recently developed for parabolic PDEs. With the integral transformation and boundary feedback the unstable PDE is converted into a "delay line" system which converges to zero in finite time. We then apply this procedure to finite-dimensional systems with actuator and sensor delays to recover a well-known infinite-dimensional controller (analog of the Smith predictor for unstable plants). We also show that the proposed method can be used for boundary control of the a Korteweg-de Vries-like third order PDE. The designs are illustrated with simulations.

Simple Analytical Design of Modified Smith Predictor with Improved Performance for Unstable First-Order Plus Time Delay (FOPTD) Processes

Abstract: A simple method of designing the controllers for the modified Smith predictor scheme with improved closed-loop performances is proposed for open-loop unstable first-order plus time delay (FOPTD) processes. The proposed method consists of two controllers that are meant for different objectives, namely, the set-point tracking and simultaneous stabilization of the unstable process with time delay and the load disturbance rejection. The design steps of these two controllers are independent. The direct synthesis method is used to design the set-point tracking controller, and simple analytical tuning rules are provided for the load disturbance controller. Robustness studies on the stability and performance are provided, with respect to the uncertainties in the unstable process model parameters. The proposed scheme consists of only one tuning parameter. Good nominal and robust control performances are achieved with the proposed method. Significant improvement in the closed-loop performances are obtained, when co...

Stability of Networked Control Systems with Time-Varying Delays

Abstract: 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

Set point weighted modified Smith predictor for integrating and double integrating processes with time delay.

Abstract: A simple method of designing the controllers for a modified form of Smith predictor is proposed for integrating and double integrating processes with time delay. The modified Smith predictor has two controllers, namely, a set point tracking controller and a load disturbance rejection controller for obtaining good set point tracking and load disturbance rejection, respectively. The set point tracking controller is designed using the classical direct synthesis method based on the process model without considering the time delay. The disturbance rejection controller is considered as a proportional-derivative (PD) controller and is designed using optimal gain and phase margin approaches. Set point weighting is considered for reducing undesirable overshoots and settling times in the modified Smith predictor. Guidelines are provided for selection of the desired closed loop tuning parameter in the direct synthesis method and the set point weighting parameter. The method gives significant load disturbance rejection performances. Illustrative examples are considered to show the performances of the proposed method. A significant improvement in control performance is obtained when compared to recently reported methods.

Modified Smith predictor design for periodic disturbance rejection.

Abstract: 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.

Smith-predictor compensator for a delayed omnidirectional mobile robot

Abstract: This paper deals with the discrete time control of an omnidirectional mobile robot subject to transport delays. A discrete-time model of the vehicle is obtained by considering an exact discretization of the continuous time model of the robot where the time delay induced by a communication network is considered. The path-tracking problem is addressed by means of a prediction strategy based on the well known Smith predictor compensator. The nonlinear nature of the omnidirectional mobile robot induces an approximate estimate of the future values of the systems that are used together with a feedback linearization approach to solve the tracking problem.

Robust Time Delayed Control Systems with Communication Disturbance Observer

Abstract: A time delay compensation method based on the concept of network disturbance and communication disturbance observer has been proposed so far. The method has the same effectiveness as that of Smith predictor and the validity has been experimentally verified. Furthermore, the advantage of the method is that it works without delay time model. However, whereas the method has been practically applied in several situations, the robustness has never been studied so far. In this paper, we present robustness of the time delayed control systems with the time delay compensation method. Some problems caused by model uncertainty and constraint on cutoff frequency are firstly discussed. Then a time delayed control system with communication disturbance observer based on two- degree-of-freedom control structure is designed. The control system makes it possible to achieve zero steady-state error. Moreover, the transient response is designed easily by parameters of controllers. Here, the transient characteristic and the attenuation performance of model uncertainty can be designed separately. Simulation results verify the validity of the control system.

The time-delay effect of multiple-network systems in NCS

Abstract: Applications of the network control system (NCS) improve the efficiency, the flexibility, and the reliability of large-scale systems in modern industries. In the same time, applications of NCS for remote control and monitoring reduce the time and cost of installation, reconfiguration, and maintenance. This study integrates the Ethernet, the control area network (CAN) network, and the wireless 802.11b in the present NCS. The TCP/IP and the CAN protocols are adopted as the communication gateway in a remote control system for an AC 400 W servo motor. The time delay between the application layer of the client and the application layer of the remote control target has been measured and analyzed in this study. Experimental results indicate that different sampling rates and the environments will greatly affect the delayed time. Also, results indicate that the distance will not affect the delay time in wireless communication. However, as the sampling period reduces, the delay time of the network increases dramatically. In the wireless network, the delay time may change suddenly by the environment interferences. Finally, with a serious time delay, a Smith predictor has been successfully applied to control the servo motor from Kaohsiung which is in 300 km away to verify the feasibility of the proposed NCS.

Real-Time Mobile Robot Teleoperation over IP Networks Based on Predictive Control

Abstract: This paper presents a system that enables remote operator to control a mobile robot with real-time control style via Internet. To compensate network delay and cancel its impact on teleoperation system, we adopt predictive control scheme based on a modified Smith predictor that we proposed previously. To guarantee stability and transparency of system, a dynamic model manager is described from sensors information exchange between the master and slave side, where model and force feedback errors are regulated under a fuzzy controller. In addition to force feedback, virtual predictive display is introduced to enhance the real-time efficiency of teleoperation. To predict time delay precisely, a novel timer synchronization algorithm is proposed. To decrease delay jittering, data buffer scheme is achieved at both sides together with its two algorithms. The usefulness and effectiveness of the developed method and system have been validated by teleoperation experiments through Internet on long distance.

Smith predictor design by CDM for temperature control system

Abstract: Smith predictor control is theoretically a good solution to the problem of controlling the time delay systems. However, it seldom gets use because it is almost impossible to find out a precise mathematical model of the practical system and very sensitive to uncertain system with variable time-delay. In this paper is concerned with a design method of smith predictor for temperature control system by coefficient diagram method (CDM). The simulation results show that the control system with smith predictor design by CDM is stable and robust whilst giving the desired time domain system performance.

GMV control of non-linear continuous-time systems including common delays and state-space models

Abstract: A non-linear generalized minimum variance control law is proposed for the control of non-linear continuous-time multivariable systems with common delays on input and output channels. The quadratic cost index involves both error and control signal costing terms. The solution for the control law is obtained using a non-linear operator representation of the plant and a linear state-equation model for the disturbance and reference models. The reference and disturbance models are represented by linear subsystems. However, the plant model can be in a very general non-linear operator form, which could involve state-space, transfer operators or non-linear function look up tables. The structure of the system and criterion is chosen so that a simple controller structure and solution is obtained. The controller obtained is simple to implement, particularly in one form, which might be considered to be a state-space version of a non-linear Smith predictor. The results are related to those for discrete-time systems but...

Robust Closed-Loop Control of the Inspired Fraction of Oxygen for the Online Assessment of Recruitment Maneuvers

Abstract: Recruitment maneuvers are commonly used in patients suffering from acute respiratory failure A continuous measurement of PaO2 would help to assess the proper execution of such maneuvers Unfortunately, there are only static offline measurement devices available However, if the oxygen saturation would be held close to a fixed set-point of 90-92% by automatically adjusting the FIO2 parameter of the mechanical ventilator, the latter would be inversely related to PaO2 In this work, a new robust PID control system is presented, which accounts for model uncertainty in a modified Smith predictor approach The controller was tested using a computer model of respiratory failure The model parameters were identified in an animal experiment with pigs

NGMV control of state dependent multivariable systems

Abstract: A nonlinear generalized minimum variance control law is derived for the control of nonlinear multivariable systems. The solution for the control law is obtained using a model for the process that includes three different types of subsystem to provide a variety of means of modeling the system. These may not all be present. The first subsystem involves a nonlinear operator of very general form. The second is a state dependent, state equation model of the plant and finally a linear state-equation model represents the output subsystem, disturbance and reference models. The process is assumed to include common delays in input or output channels of magnitude k. The quadratic like cost index involves state, error and control signal costing terms. The controller obtained is simple to implement, particularly in one form, which might be considered a nonlinear state-dependent version of the Smith predictor.

Smith Predictors in Nonlinear Systems - Application to ISS-based Leader/follower Trailing Control

Abstract: As in any control system, the presence of small delays in the feedback channel may severely affect the performance of the closed-loop system, and prevent a the successful application of established nonlinear control methodologies. In order to make a control law robust with respect to small time delay, we first extend input-to-state stability (ISS) concepts to encompass the effect of bounded delays and restrictions on the input. Then, a method is proposed to integrate the presence of a Smith predictor in a backstepping design based on nonlinear small gain assignment, when small time delays is present in the feedback loop. The method is applied to a leader-follower trailing control problem. Simulation results confirm the validity of the control design and the robustness analysis.

GIMC Structure Considering Communication Delay and Its Application to Mechatronic System

Abstract: This paper deals with a new GIMC structure considering a communication delay by using the Smith Predictor and its application to a mechatronic system. First, we stabilize the unstable mechatronic system by a PD controller and define the stabilized system as a new augmented plant. We design the proposed GIMC structure using the Smith Predictor based on Hscrinfin controllers for the new stabilized augmented plant. Finally, the proposed structure is evaluated experimentally and the effectiveness of the proposed approach is proven. In addition, we apply the proposed structure to a virtual networked control mechatronic system.

Fuzzy immune self-regulating PID control for wireless networked control system

Abstract: In order to effectively restrain the impact of network delays for wireless networked control systems (WNCS), aiming to time-variant, random and uncertain network delays and controlled plant might be time-variant or nonlinear, as well as Smith predictor models might be imprecise, we propose a novel approach that modified Smith predictor combined with fuzzy immune self-regulating PID control for the WNCS. Because modified Smith predictor does not include network delay models, therefore, it is no need for measuring on line, identifying or estimating network delays, thus it is applicable to some occasions that network delays are larger than one, even tens of sampling periods. Based on IEEE 802.11 b/g (WLAN), the results of simulation experiment show validity of the control scheme and improvement in dynamic performance and robustness of the WNCS.

Active Queue Management Controller using Smith Predictor for Time Delay Networks

Abstract: This paper presents an investigation into a robust controller for active queue management (AQM) using Smith predictor (SP). A new SP random early detector (RED) controller is proposed and compared with traditional RED based controller. It is worth noting that the RED controller is augmented by a Smith predictor structure for plants with medium and high time delays. The proposed Smith predictor based controller is implemented, tested and validated. Finally, a comparative performance of the SP controller and RED controller is presented and discussed to demonstrate the merits of the controller through a set of experiments.

Model Based Tuning of Humidifying Processes with Transportation Lag

Abstract: A humidifying system with varying transportation lag was studied experimentally. Various models were tried and the system fitted a first order plus dead time model with an error of ±5%. The humidity was measured using an on‐line Yokogawa hygrometer. From the model parameters, various controllers, such as PI, Smith predictor, IMC, and IMC PID were analyzed using Matlab. The closed loop performance was studied for both regulator and servo problems. Based on rise time, settling time, and overshoot, the present study concludes that the IMC controller is best suited for this process.

Multiple-Delay Smith Predictor Based Control of LTI Systems with Bounded Uncertain Delay

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. In this paper, an intelligent frame to reduce the 'a priori' knowledge of the plant delay required in the design of SP controllers 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 'a priori' requirement of an accurate knowledge of the value for the time delav.

Absorption Principle in Process Control Applications

Abstract: The broad class of industrial processes has similar dynamical behavior that may be described by simple mathematical models with the dead time. The most popular, a very effective and usual structure with a long dead time compensator in use today, is the Smith predictor. However, during the last 20 years, three principal problems of the Smith predictor controlling structures have been analyzed by many authors: (1) the robustness, (2) the disturbance rejection possibilities, and (3) the extension of the idea of the Smith predictor to the case of integrative plants. Furthermore, in order to effectively use control in industrial applications, simple tuning procedures must be developed. The mentioned problems may be solved more successfully than before by use of internal model principle and control together (IMPACT) structure. In this paper, the previous modification of the Smith predictor based on the IMPACT structure is improved and generalized for process control applications with the long dead time. The crucial part of the structure synthesis is implementation of the absorption principle that is derived and implemented in the general case of the continuous SISO systems with the dead time. The structure enables the extraction of the known class immeasurable disturbances and easy setting of controller parameters in order to achieve robust stability and performance. Both analytical analysis and simulation results show that tuning of the proposed structures is extremely simple due to relatively small number of tuning parameters, all having clear physical meanings.

Design and Simulation of Fuzzy Smith Intelligent Temperature Controller

Abstract: Based on the advantages of fuzzy PID control and fuzzy adaptive Smith predictor control,a Fuzzy Smith intelligent method is proposed.The filter time constant of improved-type Smith predictor is designed by fuzzy control method.The self-tuning rules and parameter fuzzy adjust organization are established.Simulation research shows that Smith intelligent control can improve the control performance of the pure hysteresis system,and the robustness and adaptability are improved.

High performance hydraulic pump system using switched reluctance drive

Abstract: High performance hydraulic pump system using SR drive is presented in this paper. A hydraulic pump system has an inherent defect that its dynamic behavior causes by interaction between the sensor and hydraulic load. It will make sometimes the whole system become oscillatory and unstable. Proposed system integrates direct instantaneous torque control (DITC) and Smith predictor to improve dynamic performance and stabilization. At last the proposed hydraulic oil pump system is verified by computer simulation and experimental results.

Robust auto tune smith predictor controller design for plant with large delay

Abstract: A robust Smith controller for plant with large delay is proposed A nonlinear PD controller is design to auto tune on-line the parameters of robust controller such that the closed system is of robust stability as well as good dynamic performance The simulation results show that the method can control the plant with large time-variable delay properly