Smith Predictor Control Research Articles

Stabilization Control of Electro-Optical Tracking System With Fiber-Optic Gyroscope Based on Modified Smith Predictor Control Scheme

The electro-optical tracking system with speedability and maneuverability based on stationary platform is confronted with some problems such as external physical disturbance and detector delay. To obtain better stability, which is the key to achieving high tracking precision, a modified Smith predictor method for inertia stabilization loop control is introduced. This method proposes the Smith predictor control scheme based to compensate delay time caused by the signal filtering of fiber gyroscope sensor in the velocity feedback control, and it utilizes disturbance feedforward control to improve the stability of stabilization platform simultaneously. The design of control structure and analysis of the theory are reported. The experiment results indicate convincingly that the proposed method can effectively improve the bandwidth of velocity closed-loop. Moreover, it can drastically enhance the disturbance suppression performance of tracking platform.

Model-free and time-constant prediction for closed-loop systems with time delay

This study presents a model-free method of signal prediction dedicated to closed-loop systems affected by time delay. The proposed prediction method leads to better prediction results than the Smith Predictor for relatively small delays. Moreover, the solution is dedicated to complex systems, which are susceptible to differences between the system and its model. The theoretical analysis, experiments, and comparisons performed in this study confirmed these features. This paper presents simplifications that were conducted to obtain the Prediction Block directly from the Smith Predictor control scheme. The Prediction Block, under specific conditions, allows for signal prediction with a constant time value. The Prediction Block was compared with an ideal anticipatory object. Furthermore, the Smith Predictor control scheme was compared with the proposed method. In this case, the transport-delay value in the closed-loop system is the only information required for proper prediction. An adapted Nyquist criterion that can prove the asymptotic stability of the control scheme was proposed. The theoretical part of the paper was supported by experiments performed on an experimental test stand with a hydraulic manipulator. In the experiments, the Prediction Block improved the position tracking of the system. The prediction control scheme has already demonstrated widespread potential for applications in multiple control approaches and experiments. The solution is dedicated to complex systems that are susceptible to differences between the system and its model.

New Smith predictive fuzzy immune PID control algorithm for MIMO networked control systems

Aiming at the problem of network-induced delays for multi-input multi-output networked control systems (MIMO NCS), a new Smith predictive fuzzy immune PID algorithm is introduced to effectively reduce the adverse effect of network-induced delays about stability in MIMO NCS, firstly, by using the v-norm type to decouple the coupling plant. Based on the generalized plant after decoupling, the new Smith predictor is designed. Then, an modified fuzzy immune feedback control algorithm is used to tune PID controller parameters online. When there is a model mismatch or parameter perturbation, the set-point tracking performance and robustness of output response can be significantly optimized. The proposed algorithm does not contain the network delay prediction model and does not need to measure, estimate, or identify the network delay. It can be used in MIMO NCS where the network bandwidth is constrained and the network-induced delays are large. Numerical examples with Ethernet protocol are built to illustrate the correctness and effectiveness of this new algorithm.

Adaptive Fuzzy Predictive Controller for a Class of Networked Nonlinear Systems With Time-Varying Delay

In this paper, an adaptive fuzzy predictive controller (AFPC) is designed and analyzed for a class of networked nonlinear systems with time-varying communication delay. The integration of the communication network in the control loops makes the nonlinear system has forward and feedback time-varying delays. The proposed controller compensates the network-induced delays in the forward and feedback channels. The structure of the AFPC consists of adaptive fuzzy logic control (AFLC) with state predictor located at the controlled plant and a remote adaptive smith predictive controller at the master node. The AFLC and the state predictor are utilized to identify the dynamic of the time-varying delay-free nonlinear plant in order to cancel the nonlinear term for the nonlinear control system in a canonical form. In the remote controller, adaptive smith predictor is employed to compensate the time-varying delay effect to achieve the desired tracking performance. Based on the Lyapunov theory, the stability of the closed-loop system is guaranteed in the presence of bounded external disturbance and time-varying delays. Simulated application of Van der Pol oscillator is provided to demonstrate the feasibility and effectiveness of the proposed scheme based on TrueTime toolbox.

Process identification of the SCR system of coal-fired power plant for de-NOx based on historical operation data

ABSTRACTThe selective catalytic reduction (SCR) system, as one principal flue gas treatment method employed for the NOx emission control of the coal-fired power plant, is nonlinear and time-varying with great inertia and large time delay. It is difficult for the present SCR control system to achieve satisfactory performance with the traditional feedback and feedforward control strategies. Although some improved control strategies, such as the Smith predictor control and the model predictive control, have been proposed for this issue, a well-matched identification model is essentially required to realize a superior control of the SCR system. Industrial field experiment is an alternative way to identify the SCR system model in the coal-fired power plant. But it undesirably disturbs the operation system and is costly in time and manpower. In this paper, a process identification model of the SCR system is proposed and developed by applying the asymptotic method to the sufficiently excited data, selected from the original historical operation database of a 350 MW coal-fired power plant according to the condition number of the Fisher information matrix. Numerical simulations are carried out based on the practical historical operation data to evaluate the performance of the proposed model. Results show that the proposed model can efficiently achieve the process identification of the SCR system.

Adaptive-Smith Predictor for Controlling an Automotive Electronic Throttle over Network

The paper presents a control strategy for an automotive electronic throttle, a device used to regulate the power produced by spark-ignition engines. Controlling the electronic throttle body is a difficult task because the throttle accounts strong nonlinearities. The difficulty increases when the control works through communication networks subject to random delay. In this paper, we revisit the Smith-predictor control, and show how to adapt it for controlling the electronic throttle body over a delay-driven network. Experiments were carried out in a laboratory, and the corresponding data indicate the benefits of our approach for applications.

A Multivariable Controller for the Start-up Procedure of a Solar Membrane Distillation Facility

This paper presents a multivariable TITO (two inputs two ouputs) controller aimed to improve the start-up procedure of a Solar Membrane Distillation (SMD) facility, located at Plataforma Solar de Almería (PSA). The control structure includes PID controllers and decouplers, as well as a reference governor based on a real time optimizer. The filtered Smith Predictor (SP) control structure has been used for controlling one of the output variables, whereas a cascade control scheme is employed to control the other one. The proposed approach has been tested in simulation on a nonlinear model of the SMD facility, showing promising results.

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.

Design of adaptive PID controllers based on adaptive Smith predictor for ultra-local model control

In this paper, an ultra-local model control approach based on adaptive Smith predictor is proposed. The design of adaptive PID controller takes into account the estimation of variable time delay which is compensated by the addition of an adaptive Smith predictor. The purpose of this paper is to solve the online estimation problem of time delay thanks to the proposed identification method of ultra-local model parameters. A performance comparison between the proposed control approach and the Smith predictor control with classical PID is carried out. The numerical simulation results of the thermal process study with severe constraints and operating conditions show the superiority of the adaptive PID controller. The robustness with respect to noises, disturbances and system parameter uncertainties of control approaches are highlighted.

New pressure control method of mixed gas in a combined cycle power plant of a steel mill

ABSTRACTThe enterprise production concept is changing with the development of society. A steel mill requires a combined-cycle power plant, which consists of both a gas turbine and steam turbine. It can recycle energy from the gases that are emitted from coke ovens and blast furnaces during steel production. This plant can decrease the overall energy consumption of the steel mill and reduce pollution to our living environment. To develop a combined-cycle power plant, the pressure in the mixed-gas transmission system must be controlled in the range of 2.30–2.40 MPa. The particularity of the combined-cycle power plant poses a challenge to conventional controllers. In this paper, a composite control method based on the Smith predictor and cascade control was proposed for the pressure control of the mixed gases. This method has a concise structure and can be easily implemented in actual industrial fields. The experiment has been conducted to validate the proposed control method. The experiment illustrates that the proposed method can suppress various disturbances in the gas transmission control system and sustain the pressure of the gas at the desired level, which helps to avoid abnormal shutdowns in the combined-cycle power plant.

Non-predictor control of a class of feedforward nonlinear systems with unknown time-varying delays

ABSTRACTThis paper generalises the several recent results on the control of feedforward time-delay nonlinear systems. First, in view of system formulation, there are unknown time-varying delays in both states and main control input. Also, the considered nonlinear system has extended feedforward nonlinearities. Second, in view of control solution, our proposed controller is a non-predictor feedback controller whereas smith-predictor type controllers are used in the several existing results. Moreover, our controller does not need any information on the unknown delays except their upper bounds. Thus, our result has certain merits in both system formulation and control solution perspective. The analysis and example are given for clear illustration.

Design of Neuro-Fuzzy Controller for Control of Water Distribution in an Irrigation Main Canal

This paper propose a neuro-fuzzy Smith predictor controller (NFSP) for effective control of water distribution in an irrigation main canal, which allows to improve the efficiency and to reduce the water losses. The dynamic model of this process is obtained from an identification procedure based in real-time data. A neuro-fuzzy controller combined with a Smith predictor is therefore designed which behaves robustly against the effect of external disturbance and plant dynamical parameters variations. Simulated results compare the performance of the proposed controller with a standard PI controller, also combined with a conventional Smith predictor for several operation conditions. These results show that the proposed controller outperforms the standard controller in terms of performance and robustness.

IMC based Smith Predictor Design with PI+CI Structure: Control of Delayed MIMO Systems

In this study a novel structure for time-delay MIMO systems controller design is introduced. In this method decoupled Smith predictor (SP) controller is designed using Internal Model Control structure (IMC). In order to approximate decoupled system, step response model approximation is employed and simulated on MIMO multiple time-delay system. Moreover, to improve system performance from overshoot and rise time perspective, Smith predictor controller is combined with PI+CI structure. Furthermore, to increase system robustness, a low pass filter is designed. Afterwards, the proposed structure is applied to the model of a time-delay MIMO distillation tower system and obtained results are compared to those of a PID controller. Finally, performance of different design methods is evaluated using Integral error criterion (Integral Square Error criterion).

Tuning and Control Strategies for a Debutanizer Column

Various conventional control strategies was performed using Proportional Integral Derivative (PID) controller which have been applied for control of a debutanizer column. Tuning of PID control strategies studied are using Smith Predictor control, Internal Mode control, Cascade control, Feedback control and Feedforward-feedback control. The comparisons were conducted using MATLAB Simulation in SIMULINK. The comparison for each control strategy performance was conducted in terms of response towards set point changes, and to evaluate the Process Variable (PV) and Manipulated Variable (MV). The success of control strategies are determined by the stability of the process model obtained from each control strategies by evaluating the IAE value.

Temperature measurement and control of bobbin tool friction stir welding

Bobbin tool friction stir welding (BTFSW) is a relatively new, solid-state welding technology, but its control is not the same as the conventional friction stir welding (FSW) due to the unique welding tool structure. In this paper, closed-loop control system was developed and the Smith predictive proportional-integral-derivative (PID) control method was presented to assist the welding system in producing an appropriate interface temperature response. As it is difficult to accurately detect the temperature in full range of the welding zone, the tool-workpiece interface temperature is detected by thermocouple and wireless transmission technology. Initial experiments were conducted to derive a qualitative understanding of bobbin tool friction stir welding processes. Ziegler-Nichols setting method was adopted to determine parameters of the PID controller. While examining the capabilities of Smith predictive PID control in BTFSW, this paper focuses on the control effect of hysteretic characteristics of welding temperature during butt welding. A compensation strategy was setting gaps along the welding path, and the gap could affect the distribution of temperature. Through our experiments, we demonstrate that temperature control strategy is feasible, and the tensile properties of the weld are uniform along the welding direction.

Stability analysis and fuzzy smith compensation control for semi-active suspension systems with time delay

This paper investigates the problem of stability analysis and fuzzy-smith compensation control for semi-active suspen- sion systems with time delay. The dynamic system of the suspension system with time delay is first formulated in terms of control objectives, such as ride comfort, road handling, and suspension deflection. By using the Lyapunov stability analysis, the neces- sary and sufficient condition of the critical time delay for the semi-active suspension is derived, and the numerical computation method of solving the asymptotic stability area for this suspension system is presented. Then, our work focuses on designing a Fuzzy-Smith predictive controller to satisfy suspension performance requirements. The control law adopted here is based on the smith predictive control principle, which ensures the control accuracy and stability of a time-delay suspension system. In order to overcome the challenging issues of the model uncertainties of input time delay, a Fuzzy-Smith predictive controller with time delay is established for the semi-active suspension. Furthermore, simulation and test results for the semi-active suspension are provided to demonstrate the effectiveness and feasibility of the proposed method.

Tuning algorithms for fractional order internal model controllers for time delay processes

ABSTRACTThis paper presents two tuning algorithms for fractional-order internal model control (IMC) controllers for time delay processes. The two tuning algorithms are based on two specific closed-loop control configurations: the IMC control structure and the Smith predictor structure. In the latter, the equivalency between IMC and Smith predictor control structures is used to tune a fractional-order IMC controller as the primary controller of the Smith predictor structure. Fractional-order IMC controllers are designed in both cases in order to enhance the closed-loop performance and robustness of classical integer order IMC controllers. The tuning procedures are exemplified for both single-input-single-output as well as multivariable processes, described by first-order and second-order transfer functions with time delays. Different numerical examples are provided, including a general multivariable time delay process. Integer order IMC controllers are designed in each case, as well as fractional-order IMC controllers. The simulation results show that the proposed fractional-order IMC controller ensures an increased robustness to modelling uncertainties. Experimental results are also provided, for the design of a multivariable fractional-order IMC controller in a Smith predictor structure for a quadruple-tank system.

Study on Control of First Order Plus Delay Using Smith Predictor

This paper presents the implementation of Smith predictor structure for the control of a first order plus delay time process. Water heater for vacuum distillation apparatus is studied, the open loop transfer function shows a first order plus delay time. The control system is analyzed using open loop Bode plot and root locus method through “sisotool” in MATLAB control tool box. The Smith predictor control design carried out using MATLAB (7.11.0) command windows. The controller gain is found to be 96.3 and the integral time 256.4

Algorithm and Implementation of Smith Predictive Control

With invariable time delay theoretically,Smith predictor is deeply studied,the fact that the Smith predictor depends on the math model of the system is found ,and so it is very difficult to control the time-varying delay system well. Therefore,it is necessary to take an effective method--using PID controller with the digital Smith predictor,and studying its control algorithm,and doing the simulation in the lab of micro-computer control. Simulation results have proved the efficiency of the algorithm and the validity.

The Design of Kiln Liquid Level Control System with Long Time-Delay

In the glass production industry, kiln glass liquid level control system is an important link. And the controlled object of liquid level control system often has the characteristics of nonlinear, time-varying and long time-delay. For this kind of complex control system, the parameters of the PID controller are difficult to be set and it is difficult to obtain the expected control effect. This paper puts forward combining fuzzy controller and Smith predictor, expounds the complementary action between Smith predictor controller and fuzzy controller. Finally according to the characteristics of the glass kiln liquid level fluctuation and the actual situation, the reasonable glass kiln liquid level automatic control scheme is designed. Using Simulink tool in MATLAB to do the simulation for the system and through the analysis of simulation results, this control system can achieve good control effect.