Inferential networked control with variable accessibility constraints (original) (raw)
Related papers
2014
The predictor and controller design for an inferential control scheme over a network is addressed. A linear plant with disturbances and measurement noise is assumed to be controlled by a controller that communicates with the sensors and the actuators through a constrained network. An algorithm is proposed such that the scarce available outputs are used to make a prediction of the system evolution with an observer that takes into account the amount of lost data between successful measurements transmissions. The state prediction is then used to calculate the control actions sent to the actuator. The possibility of control action drop due to network constraints is taken into account. This networked control scheme is analysed and both the predictor and controller designs are addressed taking into account the disturbances, the measurement noise, the scarce availability of output samples and the scarce capability of control actions update. The time-varying sampling periods that result for the process inputs and outputs due to network constraints have been determined as a function of the probability of successful transmission on a specified time with a Bernoulli distribution. For both designs performance has been established and linear matrix inequality (LMI) design techniques have been used to achieve a numerical solution.
A non-uniform predictor-observer for a networked control system
2011
This paper presents a Non-Uniform Predictor-Observer (NUPO) based control approach in order to deal with two of the main problems related to Networked Control Systems (NCS) or Sensor Networks (SN): time-varying delays and packet loss. In addition, if these delays are longer than the sampling period, the packet disordering phenomenon can appear. Due to these issues, a (scarce) non-uniform, * Corresponding author 1 delayed measurement signal could be received by the controller. But including the NUPO proposal in the control system, the delay will be compensated by the prediction stage, and the non-available data will be reconstructed by the observer stage.
State and output feedback control in model-based networked control systems
2002
In this paper the control of a continuous linear plant where the sensor is connected to a linear controller/actuator via a network is addressed. Both state and output feedback are considered. The work focuses on reducing the network usage using knowledge of the plant dynamics. Necessary and sufficient conditions for stability are derived in terms of the update time h, the network delay, and the parameters of the plant and of its model. The deterioration of behavior when either h, the delay τ, or the modeling error increase is explicitly shown and examples are used to illustrate the results. 0-7803-7516-5/02/$17.00 ©2002 IEEE
Design of Networked Control Systems With Explicit Compensation for Time-Delay Variations
IEEE Transactions on Systems, Man, and Cybernetics, Part C (Applications and Reviews), 2010
In this paper, the effects of network delay among interconnecting elements of a distributed computer network control system are analyzed. Experimental tests have been accomplished to show the influence of the combined effects of the network delay (between sensor/controller and controller/actuator) on the overall performance of a feedback control system. For this purpose, a proportional-plus-integral (PI) controller has been used. This controller has been designed, using the well-known direct synthesis method and implemented in a didactic networked control system platform. Corresponding (z-transform) difference equations have been used, assuming time-triggered (regular) samplings. The augmented PI controller (with compensation of the control signal and estimation of missing measurements) is developed. Stability analysis is performed to verify the validity of this scheme. The results presented in the paper show that the dynamic behavior of the closed-loop system can be improved using the proposed technique. Index Terms-Digital controllers, effects of time delay, networked control systems (NCSs), time-delay compensation. I. INTRODUCTION W HILE conventional control systems make use of analog or digital technology to send control signals over the loop, in modern computer control systems, the control loop is almost entirely closed over a communication network. In this networked system, the sensor, the actuator, and the controller are elements that share information by exchanging messages over the network. The great availability and ever-decreasing costs of the networked digital technology have been responsible for the replacement of the traditional point-to-point link for broadcast transmission. This change represents an important breakthrough toward effective control decentralization, resulting in significant cost reduction with wiring and maintenance [1], [2]. Such a control architecture is now been denominated networked control systems (NCSs) [3], [4]. NCSs present better characteristics in terms of modularity and scalability, offering more design options. Nevertheless, the presence of a network in the control loop has the drawback of introducing time delays in the communications among field
New Trends in Networked Control of Complex Dynamic Systems: Theories and Applications
Mathematical Problems in Engineering, 2014
In recent years, networked control systems (NCSs) have been extensively studied in both academy and industry and used in many fields, such as telerobotics, smart grids, intelligent transportation systems, and even in medical, military, and aerospace applications. NCSs offer great advantages, such as low cost, high reliability, simple installation and maintenance, and reduced weight and power requirements. In the meantime, the common shortcomings of the communication networks, such as transmission delays, packets drops and disorder, and data quantization, also appeared in the loops of the networked systems. During past decade, plenty of studies have been carried out in the literature to address the networkinduced problems for given dynamic systems that are relatively simple. However, more challenging mathematical problems such as network-based control of more complex dynamics, including time delay, parameter variations, uncertainties, and nonlinearities, are still largely open and necessitate further investigations to enable wider and more successful applications. This special issue aims to provide a timely discussion on the trends and challenges of networked control of complex dynamics systems. Both theoretical and application-oriented papers are sought for, addressing the issues and mathematical techniques of network-based control, sensing, multiagent control of complex dynamic systems, and so forth.
The International Conference on Information Networking 2013 (ICOIN), 2013
This paper investigates the problem of stabilization processes of networked control systems (NCSs) with delayed-transmission time. The investigation deals with control problem of linear time invariant (LTI) of NCSs when the plant and the controller belong to the same network. Long time delays due to the transmission element may degrade and destroy the stability of a networked control system. To overcome this problem a new exact and novel approach is analytically obtained and the delay elements in system variables have been augmented and moved to the systems parameters. An output control feedback is introduced for designing a controller based on using the same conventional control technique in the literature. A design procedure for stabilizing the linearized model of NCSs involving a time delay based on the alternative generalized model is introduced. As a result, the effect of the delay factor is completely eliminated from the system's variables and moved to the systems parameters. The design procedure of the controller that moves the finite eigenvalues of the system to arbitrary locations simultaneously is carried out in a manner similar to those obtained for non-delayed conventional state space systems. The coefficients of the feedback control law can be easily evaluated which makes it possible to update the controller's parameters on-line with the change of the operating point. It is shown that the non-delayed ordinary state space systems appear as special cases of the present work when the delay elements vanish. To support and illustrate the effectiveness and usefulness of the work presented for the proposed technique an example based on the transformed model derived in this work is introduced.
Networked Control Systems: A Model-Based Approach
Handbook of Networked and Embedded Control Systems, 2005
In this article a class of networked control systems called Model-Based Networked Control Systems (MB-NCS) is considered. This control architecture uses an explicit model of the plant in order to reduce the network traffic while attempting to prevent excessive performance degradation. MB-NCS can successfully address several important control issues in an intuitive and transparent way. In this article the main results of this MB approach are described with examples. Specifically, conditions for the stability of state and output feedback continuous and discrete systems are derived under different scenarios that include delay compensation, constant and time varying update times, non-linear plants and quantization of the feedback signals. In addition, a performance measure for MB-NCS with noise inputs is introduced.
Fundamental Issues in Networked Control Systems
This paper provides a survey on modeling and theories of networked control systems (NCS). In the first part, modeling of the different types of imperfections that affect NCS is discussed. These imperfections are quantization errors, packet dropouts, variable sampling/transmission intervals, variable transmission delays, and communication constraints. Then follows in the second part a presentation of several theories that have been applied for controlling networked systems. These theories include: input delay system approach, Markovian system approach, switched system approach, stochastic system approach, impulsive system approach, and predictive control approach. In the last part, some advanced issues in NCS including decentralized and distributed NCS, cloud control system, and co-design of NCS are reviewed.
Stability analysis and controller design for networked control systems
This work is devoted to design the stabilizing controller and stability analysis in the case of networked real-time control systems (NCSs). By considering the relationship between the network-induced delay and its bound, an improved stability criterion for NCSs is proposed in the derivative of Lyapunov function. A stabilizing state feedback controller is applied to generate the next control information for each subsystem using delayed sensing data in a free-weighting LMI formulation. Moreover the system control design focuses on the network-induced delays which may deteriorate the closed-loop performances and even destabilize the closed-loop system in real-time control. Simulation examples show the interest of the proposed approach.
Analysis of networked control systems with drops and variable delays
Automatica, 2007
Motivated by the insertion of a communication network in the feedback control loop, this paper focuses on how network-induced data dropouts and variable delays affect the stability of a linear plant with state feedback control. Sufficient conditions for Lyapunov stability are derived in the case of uncertainty due to drops and delays. The verification problem of the sufficient conditions can be directly cast as an LMI feasibility problem. We illustrate the methodology by an example in the cases of drops, delays and drops with delays. ᭧