The Experts below are selected from a list of 2652 Experts worldwide ranked by ideXlab platform

Zhou Jingyang - One of the best experts on this subject based on the ideXlab platform.

  • Perturbed Trajectory prediction based on pmu measurement in power plants
    2007
    Co-Authors: Zhou Jingyang
    Abstract:

    A method to predict the Perturbed trajectories of multi-machine power system based on measurement results of PMU (phasor measurement unit) equipped at generator terminals is proposed. Combined with state estimation or power flow data, the power system is order-reduced and simplified to such a system consisting of the generator nodes equipped with PMU; after the power system is Perturbed, utilizing the measured data of PMU the relations between voltages and currents of the order-reduced nodes is modified and substituted into corresponding generator models to realize the Perturbed Trajectory prediction of the power system. In the proposed method the data from state estimation or power flows during larger time interval is used to calculate nodal voltages and the initial value of current transitive-relationship matrix; the variation of diagonal elements of this matrix reflects the variations of the detailed models of system components, network topology and parameters after the perturbation, then by use of the PMU measured data in millisecond level the primary diagonal element can be modified. Finally, the simulation of a 6-machine 25-bus power system validates the effectiveness of the proposed method.

Pontani Mauro - One of the best experts on this subject based on the ideXlab platform.

  • Neighboring optimal guidance and proportional-derivative attitude control applied to low-thrust orbit transfers
    2019
    Co-Authors: Pontani Mauro, Celani Fabio
    Abstract:

    This work presents a unified guidance and control architecture, termed VTD-NOG & PD-RM, and describes its application to low-thrust orbit transfer from a low Earth orbit to a geostationary orbit. The variable time-domain neighboring optimal guidance (VTD-NOG) is a feedback guidance technique based upon minimizing the second differential of the objective function along the Perturbed Trajectory, and was proven to avoid the numerical difficulties encountered with alternative neighboring optimal algorithms. VTD-NOG identifies the Trajectory corrections assuming the thrust direction as the control input. A proportional-derivative attitude control based on rotation matrices (PD-RM) is used to drive the actual thrust direction toward the desired one, determined by VTD-NOG. Reaction wheels are employed to perform the attitude control action. In the dynamical simulations, thrust oscillations, errors on the initial conditions, and gravitational perturbations are considered. Extensive Monte Carlo simulations point out that orbit injection occurs with very satisfactory accuracy, even in the presence of nonnominal flight conditions

  • Variable-time-domain neighboring optimal guidance and attitude control for low-thrust orbit transfers
    2018
    Co-Authors: Pontani Mauro, Celani Fabio
    Abstract:

    In the last decades, low-thrust propulsion has gained an increasing interest by the scientific community, and has been already employed in some mission scenarios. This work proposes a unified guidance and control architecture, termed VTD-NOG & PD-RM, and describes its application to low-thrust orbit transfer from LEO to GEO. The variable timedomain neighboring optimal guidance (VTD-NOG) is a feedback guidance technique based upon minimizing the second differential of the objective function along the Perturbed Trajectory. This minimization principle leads to deriving all the corrective maneuvers, while avoiding possible singularities that often arise in alternative neighboring optimal guidance schemes. VTD-NOG identifies the Trajectory corrections by assuming a thrust direction always aligned with the longitudinal axis, thus generating a discontinuous commanded attitude. A proportional-derivative approach based on rotation matrices (PD-RM) is employed in order to drive the actual spacecraft orientation toward the desired one. Reaction wheels are employed to perform the attitude control action. In the dynamical simulations, oscillating perturbations of the propulsive thrust, errors on the initial conditions, and gravitational perturbations are considered. Extensive Monte Carlo campaigns point out that orbit injection at GEO occurs with very satisfactory accuracy, thus demonstrating that VTD-NOG & PD-RM indeed represents an effective methodology for the application at hand

  • Variable-time-domain neighboring optimal guidance, part 1: Algorithm structure
    2015
    Co-Authors: Pontani Mauro, Cecchetti Giampaolo, Teofilatto Paolo
    Abstract:

    This paper presents a general purpose neighboring optimal guidance algorithm that is capable of driving a dynamical system along a specified nominal, optimal path. This goal is achieved by minimizing the second differential of the objective function along the Perturbed Trajectory. This minimization principle leads to deriving all the corrective maneuvers, in the context of a closed-loop guidance scheme. Several time-varying gain matrices, referring to the nominal Trajectory, are defined, computed offline, and stored in the onboard computer. Original analytical developments, based on optimal control theory, in conjunction with the use of a normalized time scale, constitute the theoretical foundation for three relevant features: (i) a new, efficient law for the real-time update of the time of flight (the so called time-to-go), (ii) a new termination criterion, and (iii) a new analytical formulation of the sweep method. This new guidance, termed variable–time–domain neighboring optimal guidance, is rather general, avoids the usual numerical difficulties related to the occurrence of singularities for the gain matrices, and is exempt from the main disadvantages of similar algorithms proposed in the past. For these reasons, the variable–time–domain neighboring optimal guidance has all the ingredients for being successfully applied to problems of practical interest

Celani Fabio - One of the best experts on this subject based on the ideXlab platform.

  • Neighboring optimal guidance and proportional-derivative attitude control applied to low-thrust orbit transfers
    2019
    Co-Authors: Pontani Mauro, Celani Fabio
    Abstract:

    This work presents a unified guidance and control architecture, termed VTD-NOG & PD-RM, and describes its application to low-thrust orbit transfer from a low Earth orbit to a geostationary orbit. The variable time-domain neighboring optimal guidance (VTD-NOG) is a feedback guidance technique based upon minimizing the second differential of the objective function along the Perturbed Trajectory, and was proven to avoid the numerical difficulties encountered with alternative neighboring optimal algorithms. VTD-NOG identifies the Trajectory corrections assuming the thrust direction as the control input. A proportional-derivative attitude control based on rotation matrices (PD-RM) is used to drive the actual thrust direction toward the desired one, determined by VTD-NOG. Reaction wheels are employed to perform the attitude control action. In the dynamical simulations, thrust oscillations, errors on the initial conditions, and gravitational perturbations are considered. Extensive Monte Carlo simulations point out that orbit injection occurs with very satisfactory accuracy, even in the presence of nonnominal flight conditions

  • Variable-time-domain neighboring optimal guidance and attitude control for low-thrust orbit transfers
    2018
    Co-Authors: Pontani Mauro, Celani Fabio
    Abstract:

    In the last decades, low-thrust propulsion has gained an increasing interest by the scientific community, and has been already employed in some mission scenarios. This work proposes a unified guidance and control architecture, termed VTD-NOG & PD-RM, and describes its application to low-thrust orbit transfer from LEO to GEO. The variable timedomain neighboring optimal guidance (VTD-NOG) is a feedback guidance technique based upon minimizing the second differential of the objective function along the Perturbed Trajectory. This minimization principle leads to deriving all the corrective maneuvers, while avoiding possible singularities that often arise in alternative neighboring optimal guidance schemes. VTD-NOG identifies the Trajectory corrections by assuming a thrust direction always aligned with the longitudinal axis, thus generating a discontinuous commanded attitude. A proportional-derivative approach based on rotation matrices (PD-RM) is employed in order to drive the actual spacecraft orientation toward the desired one. Reaction wheels are employed to perform the attitude control action. In the dynamical simulations, oscillating perturbations of the propulsive thrust, errors on the initial conditions, and gravitational perturbations are considered. Extensive Monte Carlo campaigns point out that orbit injection at GEO occurs with very satisfactory accuracy, thus demonstrating that VTD-NOG & PD-RM indeed represents an effective methodology for the application at hand

Henk H Nijmeijer - One of the best experts on this subject based on the ideXlab platform.

  • sensitivity analysis of hybrid systems with state jumps with application to Trajectory tracking
    2014
    Co-Authors: Alessandro Saccon, Nathan Van De Wouw, Henk H Nijmeijer
    Abstract:

    This paper addresses the sensitivity analysis for hybrid systems with discontinuous (jumping) state trajectories. We consider state-triggered discontinuities in the state evolution, potentially accompanied by mode switching in the control vector field. For a given Trajectory with state jumps, we show how to construct an approximation of the nearby Perturbed Trajectory corresponding to a given variation of the initial condition and input signal. A major complication in the construction of such an approximation is that, in general, the jump times corresponding to a nearby Perturbed Trajectory are not equal to those of the nominal one. The main contribution of this work is the development of a notion of error to clarify in which sense the approximate Trajectory is, at each instant of time, a first-order approximation of the Perturbed Trajectory. This notion of error naturally finds application in the (local) tracking problem of a time-varying reference Trajectory of a hybrid system. To illustrate the possible use of this new error definition in the context of Trajectory tracking, we outline how the standard linear Trajectory tracking control for nonlinear systems could be generalized for hybrid systems.

  • sensitivity analysis of hybrid systems with state jumps with application to Trajectory tracking
    2014
    Co-Authors: Alessandro Saccon, Nathan Van De Wouw, Henk H Nijmeijer
    Abstract:

    This paper addresses the sensitivity analysis for hybrid systems with discontinuous (jumping) state trajectories. We consider state-triggered jumps in the state evolution, potentially accompanied by mode switching in the control vector field as well. For a given Trajectory with state jumps, we show how to construct an approximation of a nearby Perturbed Trajectory corresponding to a small variation of the initial condition and input. A major complication in the construction of such an approximation is that, in general, the jump times corresponding to a nearby Perturbed Trajectory are not equal to those of the nominal one. The main contribution of this work is the development of a notion of error to clarify in which sense the approximate Trajectory is, at each instant of time, a firstorder approximation of the Perturbed Trajectory. This notion of error naturally finds application in the (local) tracking problem of a time-varying reference Trajectory of a hybrid system. To illustrate the possible use of this new error definition in the context of Trajectory tracking, we outline how the standard linear Trajectory tracking control for nonlinear systems -based on linear quadratic regulator (LQR) theory to compute the optimal feedback gain- could be generalized for hybrid systems.

Teofilatto Paolo - One of the best experts on this subject based on the ideXlab platform.

  • Variable-time-domain neighboring optimal guidance, part 1: Algorithm structure
    2015
    Co-Authors: Pontani Mauro, Cecchetti Giampaolo, Teofilatto Paolo
    Abstract:

    This paper presents a general purpose neighboring optimal guidance algorithm that is capable of driving a dynamical system along a specified nominal, optimal path. This goal is achieved by minimizing the second differential of the objective function along the Perturbed Trajectory. This minimization principle leads to deriving all the corrective maneuvers, in the context of a closed-loop guidance scheme. Several time-varying gain matrices, referring to the nominal Trajectory, are defined, computed offline, and stored in the onboard computer. Original analytical developments, based on optimal control theory, in conjunction with the use of a normalized time scale, constitute the theoretical foundation for three relevant features: (i) a new, efficient law for the real-time update of the time of flight (the so called time-to-go), (ii) a new termination criterion, and (iii) a new analytical formulation of the sweep method. This new guidance, termed variable–time–domain neighboring optimal guidance, is rather general, avoids the usual numerical difficulties related to the occurrence of singularities for the gain matrices, and is exempt from the main disadvantages of similar algorithms proposed in the past. For these reasons, the variable–time–domain neighboring optimal guidance has all the ingredients for being successfully applied to problems of practical interest