Multirate Control Systems Research Articles

Stabilizability and Detectability of Multi-Rate Networked Control Systems with Short Time Delay

Stabilizability and Detectability of Multi-Rate Networked Control Systems with Short Time Delay

Analysis and Modeling of Multi-Rate Networked Control Systems with Short Time Delay

Analysis and Modeling of Multi-Rate Networked Control Systems with Short Time Delay

Predictor-corrector type multi-rate sample hold for continuous estimated outputs

A novel predictor-corrector hold (PCH) that yields continuous estimates for all instances is proposed for multi-rate control systems. The principle, characteristic, and performance of the PCH are analyzed. Through a comparison with other conventional holds, the efficacy of the proposed PCH is validated.

LQG Output Feedback Control of Multi-Rate Networked Control Systems

Networked control systems with single-rate mode means the sampling periods of sensor, controller and actuator are the same. Networked control systems with multi-rate mode means the sampling periods of sensor, controller and actuator are not the same. Networked control systems with single-rate mode are called single-rate networked control systems; networked control systems with multi-rate mode are called multi-rate networked control systems. The optimal estimator and LQG output feedback controller of multi-rate linear networked control systems are presented when the system has partial state information. The LQG output feedback controllers are proved to render corresponding closed-loop networked control systems exponentially mean square stable on some wild conditions. The separation theorem is proved to still hold in such multi-rate networked control systems.

Multi-rate Control System for Improvement in Intersample Response Based on State-space Representation

Multi-rate Control System for Improvement in Intersample Response Based on State-space Representation

Individual Cylinder Air–Fuel Ratio Control Using Fourier Analysis

Based on Fourier analysis, a general concept for the cylinder imbalance control problem with a single air-fuel ratio (A/F) sensor is presented. First, a control-oriented engine model is developed that is applicable for arbitrary engine types. With the model, a controller is designed, and the corresponding multirate control system is investigated in terms of stability using eigenvalue analysis. Moreover, a robustness analysis with respect to parametric uncertainties in the phase information is conducted using Monte Carlo simulations. It turns out that a good match of the model at steady state is more important than a sophisticated controller design. The domain of stable operation is identified. A five-cylinder test-bench engine is used to validate the model, to investigate the controller performance during a driving cycle, and to validate the results from the robustness analysis.

Controllability of Multi-Rate Networked Control Systems with Short Time Delay

Feedback control systems wherein the control loops are closed through a real-time network are called networked control systems. Multi-rate networked control systems mean the sampling rates of notes in networked control systems are not the same. The controllability of multi-rate networked control systems are investigated in this paper for the first time. Based on the mathematic model of multi-rate networked control systems with short time delay, some sufficient or necessary conditions for controllability of multi-rate networked control systems are got using stochastic systems approach.

Primary Research on Multirate Nature of Mechatronic System

Mechatronics system is widely used in computer numerical control, robots, medical equipment, and automatic production etc. Whereas the frequency responses of sensors and actuators in mechatronics system vary greatly, and then sampling time is also different among some links of mechatronics systems. This paper presents the multirate nature of mechatronics systems based on the characteristic of sensors and actuators. Then mechatronics system is described as a multirate discrete control system. Mathematical model of the system is established using lifting technique. Finally, a kind of motion control system that includes multirate controller is analysed and simulated with the different three sampling rates separately. The results show that the presented multirate discrete control system really exists in mechatronics system, and the performance is also influenced in a certain extent under traditional control method.

Construction and renovation of the independent component analysis model in dual rate system

Independent component analysis (ICA) is a simple, powerful tool for analysing multi-variant data to find abnormal on process monitoring. Traditional ICA algorithm is implemented on the consumption of unique sampling rate in the control system. However, there are a few multi rate control systems that could not apply the primitive ICA algorithm to the surveillance of industrial process. Several approaches of multivariate statistical modelling ICA are presented on dual rate system whose variables are correlated to each other in this paper. Furthermore, a strategy of renovation of ICA model on the dual rate system is also suggested with restricted number of new samples to replace the equally number of earliest one. The simulation results verify the capability of the modelling and updating ICA on dual rate system with their calculated statistics.

Design of multi-rate remote control systems with online estimation of the delay time

This paper integrates the IEEE 802.11g ad-hoc wireless network and the Control Area Network (CAN) as the Hybrid Networked Control System (HNCS) by implementing a communication gateway. An online delay estimation algorithm with a short-window median filter is adopted for the adaptive Smith predictor in the HNCS design. Moreover, the sampling rate is automatically switched according to the estimated delay time as network congestion occurs to render the reliable control performance of HNCS. Analytical and experimental results have proven the feasibility of the present HNCS design to achieve a satisfactory remote control system under environments with serious time delay.

Improvement in Intersample Response of HDD Head

AbstractThis paper proposes a new design method for controlling a head in a hard disk drive (HDD) system. In the HDD control system, the sampling interval of the head position is restricted, but the hold interval of the control input can be arbitrarily set. Hence, this study discusses a design method for a multi-rate control system, where the sampling and the hold intervxc als are not equal. In this study, a pole-assignment multi-rate control law is extended using newly introduced parameters such that the sample response of the plant output is maintained. Furthermore, intersample ripples in the steady state are eliminated using the new design parameters because those can be selected independently of the sample response. As a result, the intersample response can be improved independently of the sample response. The proposed method is applied to a benchmark problem of a HDD system, and its effectiveness is demonstrated.

Modeling and Stability Analysis of Multi-Rate Networked Control Systems with Multiple Control Loops

A kind of multi-input and multi-output network control system with multiple independent control loops is examined in this paper. The controller of each control loop is connected with the sensor and actuator by a network and each control loop has a different sampling period. The whole mathematical model of this kind of networked control system is set up when the maximum network-induced delay is smaller than one sampling period. And the sufficient condition subject to the asymptotic stability of this kind of networked control system is derived based on the theorem for estimation of feature value deduced from perturbation theory. The research results of this paper have significance in the analysis and design of this kind of networked control system or a similar networked control system.

Network-based predictive control of multirate systems

This study investigates the problem of model predictive control (MPC) for networked multirate control systems (NMCSs) with the output sampling period several times larger than the input updating period. Both sensor-to-controller and controller-to-actuator network-induced delays are considered and are assumed to be upperbounded by one output sampling period. Firstly, using a modified multirate MPC scheme, where the future control sequence is used to compensate for the network-induced time delays, the closed-loop NMCSs are described as switched systems. Sufficient stability conditions are established via a switched Lyapunov function approach. Then, a controller design method for stabilising NMCSs is proposed based on a finite input and state horizon cost with a finite terminal weighting matrix. The feedback gain matrix dependent of every sampling output can be obtained by solving linear matrix inequalities (LMIs). Finally, examples are provided to show the effectiveness of the proposed method.

IEEE 1451.0 standard based smart readout for multi-rate control of system

This paper presents a novel architecture for multi-rate control system with disturbance estimation and rejection using FPGA connected with sensors and actuators through IEEE 1451 standard. A signum function is used for estimation error correction. Estimated states are used to provide the control input at a rate higher or lower than the sample rate thus providing multi-rate control. An architecture is proposed to implement the proposed multi-rate controller in FPGA platform through IEEE 1451.0-2007 standard. The control scheme requires minimum analog hardware, namely comparator and digital to analog convertor and provides multi-bit resolution with multi-rate processing.

Receding horizon estimation to networked control systems with multirate scheme

This paper investigates the problem of receding horizon state estimation for networked control systems (NCSs) with random network-induced delays less than one sample period, which are formulated as multirate control systems. Based on a batch of recent past slow rate measurements in a finite horizon window, the initial state estimation in this window is solved by minimizing a receding-horizon objective function, and then the fast rate state estimations are calculated by the prediction of dynamic equation to compensate for the network-induced time delays. Furthermore, convergence results and unbiasedness properties are analyzed. An upper bound of estimation error is presented under the assumption of bounded disturbances acting on the system and measurement equations. A simulation example shows the effectiveness of the proposed method.

サンプル値位置決め制御系における外乱抑圧特性

A control system design method for disturbance suppression in a sampled-data positioning system was studied. To avoid complicated calculations involving matrices, this method uses frequency responses of a controlled object and a digital controller for calculating the gain of the sensitivity function in a sampled-data positioning control system. The method can handle inter-sampling vibrations and the characteristics of disturbance suppression beyond the Nyquist frequency in a sampled-data positioning system. As a result, this study indicates limiting conditions for disturbance suppression in the sampled-data positioning control system. This study also indicates the merits of using a multi-rate control system that includes an interpolator, a multi-rate filter, and a multi-rate hold. In order to verify the validity of the proposed method, simulations and experiments for disturbance suppression in the sampled-data positioning control system were conducted on a head-positioning control system in a hard disk drive.

A new method of multirate state feedback control with application to an HDD servo system

This paper discusses the redesign method for state feedback multirate control with current estimator. A computationally effective multirate digital control scheme, in which the control outputs are calculated based only on the state estimates at sampling instants, is presented. It is shown that the states of the redesigned state feedback multirate control system match the states of conventional state feedback multirate control system at every sampling instant. This conclusion is further supported by the analysis in frequency domain. The redesigned method is applied to a HDD servo control systems. The experimental results show that the performance of the redesigned multirate system is similar to that of the conventional multirate design in terms of open loop bandwidth, stability margins and tracking performance.

Multirate Constrained Predictive Control: Algorithm and Experimental Results

Control of multirate systems is a challenging problem due to several reasons such as increased complexity in the design with tighter performance specifications. In this work, an algorithm for multirate constrained predictive control (MCPC) is presented. The multirate predictive control system includes a multirate state estimator, which provides inter-sample estimates of state variables of the process from infrequent and slow measurements. Constraints are addressed rigorously in this framework. The proposed design method is verified via simulation as well as experimentation. The results of the multirate predictive control for temperature control of a stirred tank system are shown and compared with those of a proportional integral (PI) control system.

Disturbance rejection in hard disk drives with multi-rate estimated state feedback

Multi-rate control has been proposed as a solution to improve the performance of Hard Disk Drives (HDDs) head servo positioning. Some authors report unexpected decrease in performance when using this approach. This paper presents an analytical method to obtain the closed-loop sensitivity function of a multi-rate control system, with estimated state feedback. By using this tool, it is shown why disturbance rejection in multi-rate control may be worse than in single-rate. The paper reports both simulation and experimental results, confirming the possible decrease in performance, when using a standard design for the multi-rate control, even when a first-order hold is used. The paper also presents a novel design procedure for the multi-rate estimator, which takes into account the spectral distribution of disturbances and yields to a better performance, compared to both single-rate and standard multi-rate control.

A Design Method of Perfect Tracking Control for Discrete-Time Systems Using Multi-Rate Control

This paper presents a design method of perfect tracking control, for discrete-time systems based on multi-rate control. Generally, perfect tracking control schemes cannot be applied to nonminimum phase plants because of unstable pole-zero cancellations. Some methods that are applicable to nonminimum phase plants have been proposed, however, the following problems are left unsolved : limitations to plants and unclearness of design freedoms. We propose to use multi-rate control systems and state feedback schemes for perfect tracking. Since the method has been stated in 2-degree of freedom control techniques in this paper, it is clear how the design freedoms will be reserved after the design of tracking control. Basic techniques of this scheme have been presented, however, they cannot be applied to nonminimum phase discrete-time systems. We propose techniques that are applicable to nonminimum phase discrete-time systems. Finally, computer simulation results are presented.