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IIT Jodhpur

This paper proposes to design a robust controller for a class of nonlinear networked control systems using aperiodic feedback information. The parameter variation and system nonlinearity are considered as sources of uncertainty. To tackle uncertainty in system dynamics, a linear robust control law is derived using optimal control theory. Two different architectures of closed-loop systems are considered. In the first one, system and controller are not collocated; instead they are interconnected by means of a shared communication network. In the second architecture, however, sensors and controller are connected through a shared communication channel. In both architectures, the feedback loop is closed through the network. To save network bandwidth, the state and input information are transmitted aperiodically through the feedback loop. To this aim, the paper adopts an event-triggered control approach to reduce the transmission overhead. We show that the designed event-triggered controller achieves a trade-off between control performance and saving network bandwidth in the presence of uncertainty. The developed control algorithm is implemented and validated numerically on a classical nonlinear system. © 2020 IEEE.

Department of Electrical Engineering

World University root node

IECON Proceedings (Industrial Electronics Conference)

Robust Stabilization of a Class of Networked Nonlinear Systems via Parsimonious Communication and Actuation

This article proposes a framework to design a robust controller for a class of nonlinear networked control systems using aperiodic feedback information. Here, the nonlinearity and parameter variations of system model are considered as sources of uncertainty. To tackle the uncertainty in system dynamics, a linear robust control law is derived by applying the optimal control theory. Two different architectures of closed-loop systems are considered. In the first one, system and controller are not collocated; instead they are interconnected by means of a shared communication network. In the second architecture, system, controller and actuator are all collocated with their respective outputs available at all time - instead, sensors and controller are connected through a shared communication channel. In both architectures, the feedback loop is closed through the network. Owing to its shared nature, the network may suffer from bandwidth limitations. To save the network bandwidth, state and input information are transmitted aperiodically within the feedback loop. With this aim, the paper adopts an event-triggered control technique so as to reduce the transmission overhead. Applying Input-to-State Stability theory, we derive two different event-triggered robust control laws that stabilize the uncertain nonlinear system. Finally, we show that the designed event-triggered controllers satisfy the trade-off between control performance and saving in network bandwidth in the presence of uncertainty. The developed control algorithm is implemented and validated through numerical simulations. © 2013 IEEE.

Fulltext

IEEE Access

Robust stabilization of a class of nonlinear systems via aperiodic sensing and actuation

In this paper, we consider a class of denial-of-service (DoS) attacks, which aims at overloading the communication channel. On top of the security issue, continuous or periodic transmission of information within feedback loop is necessary for the effective control and stabilization of the system. In addition, uncertainty - originating from variation of parameters or unmodeled system dynamics - plays a key role in the system's stability. To address these three critical factors, we solve the joint control and security problem for an uncertain discrete-time Networked Control System (NCS) subject to limited availability of the shared communication channel. An event-triggered-based control and communication strategy is adopted to reduce bandwidth consumption. To tackle the uncertainty in the system dynamics, a robust control law is derived using an optimal control approach based on a virtual nominal dynamics associated with a quadratic cost-functional. The conditions for closed-loop stability and aperiodic transmission rule of feedback information are derived using the discrete-time Input-to-State Stability theory. We show that the proposed control approach withstands a general class of DoS attacks, and the stability analysis rests upon the characteristics of the attack signal. The results are illustrated and validated numerically with a classical NCS batch reactor system. © 2019 IEEE.

Proceedings of the IEEE Conference on Decision and Control

Robust Stabilization of Resource Limited Networked Control Systems under Denial-of-Service Attack

This paper proposes a discrete-time robust control technique for an uncertain nonlinear system. The uncertainty mainly affects the system dynamics due to mismatched parameter variation which is bounded by a predefined known function. In order to compensate the effect of uncertainty, a robust control input is derived by formulating an equivalent optimal control problem for a virtual nominal system with a modified costfunctional. To derive the stabilizing control law for a mismatched system, this paper introduces another control input named as virtual input. This virtual input is not applied directly to stabilize the uncertain system, rather it is used to define a sufficient condition. To solve the nonlinear optimal control problem, a discretetime general Hamilton-Jacobi-Bellman (DT-GHJB) equation is considered and it is approximated numerically through a neural network (NN) implementation. The approximated solution of DTGHJB is used to compute the suboptimal control input for the virtual system. The suboptimal inputs for the virtual system ensure the asymptotic stability of the closed-loop uncertain system. A numerical example is illustrated with simulation results to prove the efficacy of the proposed control algorithm. © 2014 Chinese Association of Automation.

IEEE/CAA Journal of Automatica Sinica

Suboptimal robust stabilization of discrete-time mismatched nonlinear system

This technical note proposes a procedure to control an uncertain discrete-time networked system using an aperiodic stabilizing input information. The system is primarily affected by the time-varying, norm bounded, mismatched parametric uncertainty. Aperiodic exchange of information is done due to bandwidth constraint of the communication network. An event-triggered based robust control strategy is adopted to reduce the effects of system uncertainty in such bandwidth constrained networks. In event-triggered control, the control input is computed and actuated at the system end only when a pre-specified event condition is violated. The robust control input is derived to stabilize the uncertain system by solving an optimal control problem based on a virtual nominal dynamics and a modified cost-functional. It is shown that the robust control law with aperiodic information ensures input-to-state stability (ISS) of the original system in the presence of mismatched uncertainty. Deriving the event-triggering condition for a discrete-time uncertain system and ensuring the stability of such system analytically are the key contributions of this technical note. A numerical example is given to prove the efficacy of the proposed event-based control algorithm over the conventional periodic one. © 1963-2012 IEEE.

IEEE Transactions on Automatic Control

Stabilization of Uncertain Discrete-Time Linear System with Limited Communication

A conceptual design methodology is proposed for event-triggered based power system control. The event-triggering mechanism is adopted to reduce the communication burden between origin of the remote control signal and the controller location. The remote signal is transmitted to the controller location only when a pre-defined state dependent event-triggering condition, is satisfied. The triggering condition is derived from a stability criterion, and is monitored continuously by a separate event-monitoring unit located at the origin of the remote signal. The stability of the resulting closed loop system is guaranteed via the input-to-state stability (ISS) technique. The proposed event triggered mechanism is implemented on single machine infinite bus test power system. The validation of proposed mechanism is carried out through the simulation studies on MATLAB/Simulink platform. The numerical results show the efficacy of the controller in managing the communication channel usage without compromising the stated system stability objectives. © 2016 IEEE.

2016 IEEE 6th International Conference on Power Systems, ICPS 2016

Conceptual analysis and representation of event-triggering mechanism in power system

Event-triggered control has a greater significance in networked control system (NCS) as it minimizes communication cost. The present paper introduces a novel event-based robust control framework for linear uncertain system. The robust control law is designed by solving an optimal control problem and realized thorough a dynamic event-triggering mechanism to reduce the communication traffic. A dynamic variable is used to generate the event-triggering law using Input-to-State Stability (ISS) criteria. Proposed control strategies ensure stability in the presence of bounded system uncertainties. Derivation of dynamic event-triggering rule with a non-zero positive inter-event time and corresponding stability criteria for uncertain system are the key contributions of this paper. The validation of proposed algorithm is carried out through a numerical simulation. © 2016, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved.

IFAC-PapersOnLine

Robust dynamic event-triggered control for linear uncertain system

This paper proposes a framework to design an event-triggered based robust control law for linear uncertain system. The robust control law is realized through both static and dynamic event-triggering approach to reduce the computation and communication usages. Proposed control strategies ensure stability in the presence of bounded matched and mismatched system uncertainties. Derivation of event-triggering rule with a non-zero positive inter-event time and corresponding stability criteria for uncertain event-triggered system are the key contributions of this paper. The efficacy of proposed algorithm is carried out through a comparative study of simulation results. © 2015 Chinese Automatic Control Society and John Wiley & Sons Australia, Ltd

Asian Journal of Control

Model Based Robust Control Law for Linear Event-Triggered System

A conceptual design methodology is proposed for event-triggered based communication for wide-area damping controller in power systems. The event-triggering mechanism is adopted to reduce the communication burden between the origin of the remote signal and the wide-area damping controller (WADC) location. The remote signal is transmitted to the WADC only when an event-triggering condition based on a predefined system output, is satisfied. The triggering condition is derived from a stability criterion, and is monitored continuously by a separate event-monitoring unit located at the origin of the remote signal. The stability of the resulting closed-loop system is guaranteed via the input-to-state stability technique. The proposed event-triggered WADC is implemented on two typical test power systems - two area four machine and IEEE 39-bus 10-machine. The validation of proposed mechanism is carried out through non-linear simulation studies on MATLAB/Simulink platform. The numerical results show the efficacy of the controller in managing the communication channel usage without compromising the stated system stability objectives. © The Institution of Engineering and Technology 2016.

IET Generation, Transmission and Distribution

Event-triggered communication in wide-area damping control: A limited output feedbackbased approach

This paper proposes a finite-time robust control law for a nonlinear, uncertain robot manipulator. Load variations and unmodeled system dynamics of manipulator are the primary sources of uncertainties. The dynamics of the manipulator is modeled in State-Dependent Coefficient (SDC) form to consider all nonlinear term in system dynamics. To control such uncertain system a robust control law is essential. An optimal control approach is adopted to design the proposed robust control law. The control input is generated by solving a State-Dependent Differential Riccati Equation (SDDRE) in forward in time. Here the analytical solution of SDDRE is used to compute control law. The designed control law ensures the stability analytically and numerically in the presence of bounded uncertainty. © 2015 ACM.

ACM International Conference Proceeding Series

Finite-time robust control of robot manipulator: A SDDRE based approach

This paper proposes a framework to design an event-triggered based robust control law for nonlinear uncertain robot manipulator. Load variations and unmodeled system dynamics of manipulator are the primary sources of both system and input uncertainties. A static event-triggering rule is employed to realize the proposed robust control law. Derivation of static event-triggering rule with a positive inter-event time and corresponding stability criteria for uncertain manipulator dynamics are the key contribution of this paper. Validation of proposed control technique is carried out numerically on a two-link SCARA type robot manipulator. Simulation results show that measurement error norm is always bounded by the state dependent threshold and also ensures that asymptotic convergence of manipulator states in the presence of both system and input uncertainty. © 2014 IEEE.

2014 13th International Conference on Control Automation Robotics and Vision, ICARCV 2014

An event-triggered based robust control of robot manipulator

Different wireless application platforms are available for remote monitoring and control of systems. In the present paper a system has been described for online remote recording and monitoring of sensor data using DTMF (Dual Tone Multi Frequency) technology where acoustic communication has been implemented. One DTMF transceiver in the sensing system has been used to generate and decode the DTMF tone corresponding to the sensor output which in turn is received from the mobile phone in the user side. A separate DTMF decoder has been used in the user side to decode the received DTMF tone corresponding to the sensor output from the sensor side. Microcontroller has been used to store the decoded data from the sensor and to control the whole operation sequentially. Thus online remote recording and monitoring of the sensor data have been possible at any where in the coverage area of the mobile network. Experimental result shows good linearity between data output taken directly from the sensor side and that remotely from user side. © 2011 IFSA.