256 research outputs found
A Kalman Filter-based disturbance observer for state-of-charge estimation in EV batteries
No full textA method for estimating the state-of-charge in batteries of electric vehicles is developed using a Kalman Filter-based disturbance observer. Estimation of the state-of-charge is important for the safe functioning of electric vehicles and for minimizing their charging time. The computation of the state-of-charge of the battery at each time instant becomes a non-trivial problem because one can measure only an output voltage. In the present article the equations of Kirchhoff's voltage and current laws are used first to obtain the electric dynamics of the battery and to formulate the associated state-space model. Next, the Kalman Filter is redesigned as a disturbance observer, so as to estimate the state-of-charge despite the effects of model uncertainty terms, The proposed method allows for computing not only the battery's state-of-charge but also for identifying perturbations and model uncertainty about the charging process
Chaos-based communication scheme using proportional and proportional-integral observers
No full textIn this paper, we propose a new chaos-based communication scheme using the observers. The novelty lies in the masking procedure that is employed to hide the confidential information using the chaotic oscillator. We use a combination of the addition and inclusion methods to mask the information. The performance of two observers, the proportional observer (P-observer) and the proportional integral observer (PI-observer) is compared that are employed as receivers for the proposed communication scheme. We show that the P-observer is not suitable scheme since it imposes unpractical constraints on the messages to be transmitted. On the other hand, we show that the PI-observer is the better solution because it allows greater flexibility in choosing the gains of the observer and does not impose any unpractical restrictions on the message
Standalone DC microgrids as complementarity dynamical systems: Modeling and applications
No full textIt is well known that, due to bimodal operation as well as existent discontinuous differential states of batteries, standalone microgrids belong to the class of hybrid dynamical systems of non-Filippov type. In this work, however, standalone microgrids are presented as complementarity systems (CSs) of the Filippov type which is then used to develop a multivariable nonlinear model predictive control (NMPC)-based load tracking strategy as well as Modelica models for long-term simulation purposes. The developed load tracker strategy is a multi-source maximum power point tracker (MPPT) that also regulates the DC bus voltage at its nominal value with the maximum of ±2.0% error despite substantial demand and supply variations
Nonlinear optimal control for ship propulsion with the use of an induction motor and a drivetrain
No full textA nonlinear optimal (H-infinity) control method is proposed for an electric ship's propulsion system that consists of an induction motor, a drivetrain and a propeller. The control method relies on approximate linearization of the propulsion system's dynamic model using Taylor-series expansion and on the computation of the state-space description's Jacobian matrices. The linearization takes place around a temporary equilibrium which is recomputed at each time-step of the control method. For the approximately linearized model of the ship's propulsion system, an H-infinity (optimal) feedback controller is developed. For the computation of the controller's gains an algebraic Riccati equation is solved at each iteration of the control algorithm.The stability properties of the control method are proven through Lyapunov analysis
Condition monitoring for the quadruple water tank system using H-infinity Kalman Filtering
No full textThe problem of statistical fault diagnosis for the quadruple watertanks system is examined. The solution of the fault diagnosis problem for the dynamic model of the four-water tanks system is a non-trivial case, due to nonlinearities and the system's multivariable structure. In the article's approach, the system's dynamic model undergoes first approximate linearization around a temporary operating point which is recomputed at each sampling period. The linearization procedure relies on Taylor series expansion and on the computation of the Jacobian matrices of the state-space description of the system. The H-infinity Kalman Filter is used as a robust state estimator for the approximately linearized model of the quadruple water tanks system. By comparing the outputs of the H-infinity Kalman Filter against the outputs measured from the real water tanks system the residuals sequence is generated. It is concluded that the sum of the squares of the residuals' vectors, being weighted by the inverse of the associated covariance matrix, stands for a stochastic variable that follows the χ2 distribution. As a consequence, a statistical method for condition monitoring of the quadruple water tanks system is drawn, by using the properties of the χ2 distribution and the related confidence intervals. Actually, normal functioning can be ensured as long as the value of the aforementioned stochastic variable stays within the previously noted confidence intervals. On the other side, one can infer the malfunctioning of the quadruple water tanks system with a high level of certainty (e.g. of the order of 96% to 98%), when these confidence intervals are exceeded. The article's method allows also for fault isolation, that is for identifying the specific component of the quadruple water tanks system that has been subject to fault or cyber-attack
Fundamental issues in antenna design for microwave medical imaging applications
No full textThis paper surveys the development of microwave medical imaging and the fundamental challenges associated with microwave antennas design for medical imaging applications. Different microwave antennas used in medical imaging applications such as monopoles, bow-tie, vivaldi and pyramidal horn antennas are discussed. The challenges faced when the latter used in medical imaging environment are detailed. The paper provides the possible solutions for the challenges at hand and also provides insight into the modelling work which will help the microwave engineering community to understand the behaviour of the microwave antennas in coupling media
Observer-based secure communication using indirect coupled synchronization
No full textIn this paper, an observer-based secure communication system composed of four chaotic oscillators is proposed. Observer based synchronization is achieved between two of these oscillators and employed as a transmitter and a receiver. The other two oscillators are indirectly coupled and are employed as keystream generators. The novelty lies in the generation of the same chaotic keystream both in the transmitter and receiver side for encryption and decryption purposes. We show, in particular, that it is possible to synchronize the two keystream generators even though they are not directly coupled. So doing, an estimation of the keystream is obtained allowing decrypting the message. The performance of the proposed communication scheme is shown via simulation using the Chua and Lorenz oscillators
Nonlinear Optimal Control for Gas-Turbine Power Generation Units
No full textA nonlinear optimal (H-infinity) control approach is proposed for an electric power unit that comprises a gas-turbine and a synchronous-generator. The control method aims at synchronizing the generator with the grid's frequency while also optimizing the fuel's consumption by the gas-turbine. At a first stage the state-space model of the the power unit is linearized at a temporary operating point which is updated at each iteration of the control method. The linearization procedure relies on Taylor series expansion and on the computation of the system's Jacobian matrices. At a second stage, an H-infinity feedback controller is designed for the approximately linearized model of the power unit. This allows to solve the optimal control problem of the power generation unit, despite the effects of model inaccuracy and exogenous disturbances. The feedback gain of the H-infinity controller, is obtained after solving an algebraic Riccati equation at each time-step of the control method. Finally, Lyapunov analysis is used to prove the global asymptotic stability properties of the control scheme
Flatness-based control and Kalman filtering for a continuous-time macroeconomic model
No full textThe article proposes flatness-based control for a nonlinear macro-economic model of the UK economy. The differential flatness properties of the model are proven. This enables to introduce a transformation (diffeomorphism) of the system's state variables and to express the state-space description of the model in the linear canonical (Brunowsky) form in which both the feedback control and the state estimation problem can be solved. For the linearized equivalent model of the macroeconomic system, stabilizing feedback control can be achieved using pole placement methods. Moreover, to implement stabilizing feedback control of the system by measuring only a subset of its state vector elements the Derivative-free nonlinear Kalman Filter is used. This consists of the Kalman Filter recursion applied on the linearized equivalent model of the financial system and of an inverse transformation that is based again on differential flatness theory. The asymptotic stability properties of the control scheme are confirmed
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