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Jin Young Choi - One of the best experts on this subject based on the ideXlab platform.

  • new parametric affine modeling and control for skid to turn missiles
    IEEE Transactions on Control Systems and Technology, 2001
    Co-Authors: Dongkyoung Chwa, Jin Young Choi
    Abstract:

    This paper presents a new practical autopilot design approach to acceleration control for tail-controlled skid-to-turn (STT) missiles. The approach is novel in that the proposed parametric affine missile model adopts acceleration as the controlled output and considers the couplings between the forces as well as the moments and control fin deflections. The Aerodynamic Coefficients in the proposed model are expressed in a closed form with parameters that can be fitted over the whole operating range. The parameters are fitted from Aerodynamic Coefficient lookup tables by the proposed function approximation technique, which is based on the combination of local parametric models through curve fitting using the corresponding influence functions. In addition, a feedback linearizing controller is designed by using the proposed parametric affine missile model. Stability analysis for the overall closed-loop system is provided, considering the uncertainties arising from approximation errors. The validity of the proposed modeling and control approach is demonstrated through simulations for an STT missile.

  • new parametric affine modeling and control for skid to turn missiles
    American Control Conference, 2000
    Co-Authors: Dongkyoung Chwa, Jin Young Choi
    Abstract:

    This paper presents a new practical autopilot design approach to acceleration control for tail-controlled STT (skid-to-turn) missiles. The approach is novel in that the proposed parametric affine missile model adopts acceleration as the controlled output and considers the couplings between the forces as well as the moments and control fin deflections. The Aerodynamic Coefficients in the proposed model are expressed in a closed form with fittable parameters over the whole operating range. The parameters are fitted from Aerodynamic Coefficient look-up tables by the function approximation technique, which is based on the combination of local parametric models through curve fitting using the corresponding influence functions. In this paper, in order to employ the results of parametric affine modeling in the autopilot controller design, we derived a parametric affine missile model and designed a feedback linearizing controller for the obtained model. Stability analysis for the overall closed loop system is provided, considering the uncertainties arising from approximation errors. The validity of the proposed modeling and control approach is demonstrated through simulations for an STT missile.

Tor Arne Johansen - One of the best experts on this subject based on the ideXlab platform.

  • Icing Detection for Small Fixed Wing UAVs using Inflight Aerodynamic Coefficient Estimation
    2019 IEEE Aerospace Conference, 2019
    Co-Authors: Andreas Wenz, Tor Arne Johansen
    Abstract:

    In cold and humid environments, airfoil icing is a major hindrance to UAV operations. Airfoil icing increases the Aerodynamic drag Coefficient, while reducing the maximum lift Coefficient and the stall angle. This results in degraded endurance and safety of an UAV. Recently de-icing solutions for fixed-wing UAVs have been developed. These solutions use resistive heating in order to melt the ice on the wings. However, since this requires a high amount of energy it is desirable to only heat the wings if significant icing occurs. In this paper, a method for automatic icing detection is presented. A moving horizon estimator (MHE) is used, which combines Aerodynamic, kinematic and stochastic wind models with data from a typical autopilot sensor suite to estimate angle of attack and lift Coefficients. The sensor suite consists of an inertial measurement unit (IMU), a global navigation satellite system (GNSS) receiver, a heading reference and a pitot-static tube. Within the MHE an Unscented Kalman Filter (UKF) is used for arrival cost approximation. FENSAP icing simulations show that in severe icing conditions, both the offset and the gradient of the lift Coefficient change. Based on these icing simulations an UAV flight simulator that can simulate icing has been used. Simulation results show that the MHE is capable of monitoring changes in offset and gradient of the lift Coefficient due to icing. A faster convergence to the estimated Coefficient values could be achieved when using an external trigger signal, i.e. from a temperature and humidity sensor, to reset the covariance matrix of the arrival cost. We also investigate the effect on convergence speed resulting from an altitude change giving additional excitation. The estimation results show angle of attack estimation errors below 1 degree. These estimates can be used to limit the angle of attack and adjust the commanded airspeed in the autopilot in order to avoid stall.

  • icing detection for small fixed wing uavs using inflight Aerodynamic Coefficient estimation
    International Conference on Control Applications, 2016
    Co-Authors: Andreas Wenz, Tor Arne Johansen
    Abstract:

    We propose a method to detect icing of the airfoil of a fixed-wing Unmanned Aerial Vehicle by using an Aerodynamic Coefficient estimator and ambient temperature and humidity sensors. The estimator uses the information provided by a standard autopilot sensor suite consisting of an IMU, GNSS and a pitot-static tube to estimate lift Coefficients as well as steady and turbulent wind velocities. These sensor inputs are fused within an Extended Kalman Filter using frequency separation and kinematic, Aerodynamic and wind models while avoiding the need for prior knowledge about the aircraft. Ambient temperature and humidity sensors are used to assess environmental conditions and if icing is suspected, a trigger signal to the estimator and the autopilot is generated. This signal is used to adjust the anticipated uncertainties of the estimated Coefficients and, if permitted by the flight control system, to initialize a small altitude change in order to excite the estimator. Simulation results show that this method is able to separate clearly between iced and non-iced cases and can be used to significantly enhance the detection performance compared to only using temperature and humidity based information.

Dongkyoung Chwa - One of the best experts on this subject based on the ideXlab platform.

  • new parametric affine modeling and control for skid to turn missiles
    IEEE Transactions on Control Systems and Technology, 2001
    Co-Authors: Dongkyoung Chwa, Jin Young Choi
    Abstract:

    This paper presents a new practical autopilot design approach to acceleration control for tail-controlled skid-to-turn (STT) missiles. The approach is novel in that the proposed parametric affine missile model adopts acceleration as the controlled output and considers the couplings between the forces as well as the moments and control fin deflections. The Aerodynamic Coefficients in the proposed model are expressed in a closed form with parameters that can be fitted over the whole operating range. The parameters are fitted from Aerodynamic Coefficient lookup tables by the proposed function approximation technique, which is based on the combination of local parametric models through curve fitting using the corresponding influence functions. In addition, a feedback linearizing controller is designed by using the proposed parametric affine missile model. Stability analysis for the overall closed-loop system is provided, considering the uncertainties arising from approximation errors. The validity of the proposed modeling and control approach is demonstrated through simulations for an STT missile.

  • new parametric affine modeling and control for skid to turn missiles
    American Control Conference, 2000
    Co-Authors: Dongkyoung Chwa, Jin Young Choi
    Abstract:

    This paper presents a new practical autopilot design approach to acceleration control for tail-controlled STT (skid-to-turn) missiles. The approach is novel in that the proposed parametric affine missile model adopts acceleration as the controlled output and considers the couplings between the forces as well as the moments and control fin deflections. The Aerodynamic Coefficients in the proposed model are expressed in a closed form with fittable parameters over the whole operating range. The parameters are fitted from Aerodynamic Coefficient look-up tables by the function approximation technique, which is based on the combination of local parametric models through curve fitting using the corresponding influence functions. In this paper, in order to employ the results of parametric affine modeling in the autopilot controller design, we derived a parametric affine missile model and designed a feedback linearizing controller for the obtained model. Stability analysis for the overall closed loop system is provided, considering the uncertainties arising from approximation errors. The validity of the proposed modeling and control approach is demonstrated through simulations for an STT missile.

Andreas Wenz - One of the best experts on this subject based on the ideXlab platform.

  • Icing Detection for Small Fixed Wing UAVs using Inflight Aerodynamic Coefficient Estimation
    2019 IEEE Aerospace Conference, 2019
    Co-Authors: Andreas Wenz, Tor Arne Johansen
    Abstract:

    In cold and humid environments, airfoil icing is a major hindrance to UAV operations. Airfoil icing increases the Aerodynamic drag Coefficient, while reducing the maximum lift Coefficient and the stall angle. This results in degraded endurance and safety of an UAV. Recently de-icing solutions for fixed-wing UAVs have been developed. These solutions use resistive heating in order to melt the ice on the wings. However, since this requires a high amount of energy it is desirable to only heat the wings if significant icing occurs. In this paper, a method for automatic icing detection is presented. A moving horizon estimator (MHE) is used, which combines Aerodynamic, kinematic and stochastic wind models with data from a typical autopilot sensor suite to estimate angle of attack and lift Coefficients. The sensor suite consists of an inertial measurement unit (IMU), a global navigation satellite system (GNSS) receiver, a heading reference and a pitot-static tube. Within the MHE an Unscented Kalman Filter (UKF) is used for arrival cost approximation. FENSAP icing simulations show that in severe icing conditions, both the offset and the gradient of the lift Coefficient change. Based on these icing simulations an UAV flight simulator that can simulate icing has been used. Simulation results show that the MHE is capable of monitoring changes in offset and gradient of the lift Coefficient due to icing. A faster convergence to the estimated Coefficient values could be achieved when using an external trigger signal, i.e. from a temperature and humidity sensor, to reset the covariance matrix of the arrival cost. We also investigate the effect on convergence speed resulting from an altitude change giving additional excitation. The estimation results show angle of attack estimation errors below 1 degree. These estimates can be used to limit the angle of attack and adjust the commanded airspeed in the autopilot in order to avoid stall.

  • icing detection for small fixed wing uavs using inflight Aerodynamic Coefficient estimation
    International Conference on Control Applications, 2016
    Co-Authors: Andreas Wenz, Tor Arne Johansen
    Abstract:

    We propose a method to detect icing of the airfoil of a fixed-wing Unmanned Aerial Vehicle by using an Aerodynamic Coefficient estimator and ambient temperature and humidity sensors. The estimator uses the information provided by a standard autopilot sensor suite consisting of an IMU, GNSS and a pitot-static tube to estimate lift Coefficients as well as steady and turbulent wind velocities. These sensor inputs are fused within an Extended Kalman Filter using frequency separation and kinematic, Aerodynamic and wind models while avoiding the need for prior knowledge about the aircraft. Ambient temperature and humidity sensors are used to assess environmental conditions and if icing is suspected, a trigger signal to the estimator and the autopilot is generated. This signal is used to adjust the anticipated uncertainties of the estimated Coefficients and, if permitted by the flight control system, to initialize a small altitude change in order to excite the estimator. Simulation results show that this method is able to separate clearly between iced and non-iced cases and can be used to significantly enhance the detection performance compared to only using temperature and humidity based information.

Abdessattar Abdelkefi - One of the best experts on this subject based on the ideXlab platform.

  • role of the galloping force and moment of inertia of inclined square cylinders on the performance of hybrid galloping energy harvesters
    Applied Energy, 2018
    Co-Authors: Umer Javed, Abdessattar Abdelkefi
    Abstract:

    Abstract Energy harvesting by a square cross-section cylinder, inclined at different angles from the incoming wind flow, prone to galloping oscillations is investigated. The cylinder is fixed at the tip of a cantilever beam at a definite angle, to which is attached a piezoelectric layer and a permanent magnet placed in the close vicinity of a coil. Existing Aerodynamic-Coefficient experimental values as a function of the incident angle of attack are utilized for determining the Aerodynamic force on each inclined cylinder. Seven-order polynomial is recognized to be a convenient choice for performing the analyses in this study. After establishing the galloping Aerodynamic force of each case, a reduced-order model is developed for the beam-cylinder energy harvester using Galerkin discretization. Moment of inertia of each case is calculated using transformation matrix and its impact on the natural frequency is determined. It is shown that the moment of inertia affects the linear characteristics of the galloping-based energy harvester when the inclination of the cylinder is changed. The nonlinear characteristics and performance of the energy harvester for various inclination angles are carried out. It is indicated that an upright zero inclined or a slight angle of cylinder till ten or fifteen degrees towards the wind flow is preferable for energy harvesting. Any forward inclination towards the wind flow greater than that or any backward angle of cylinder away from the wind flow are not suitable for attaining high levels of harvested power. This behavior actually opens the doors for using a movable cylinder at the tip of a beam with lock mechanism that can be tilted at a high forward or backward angle for extreme windy conditions to have reasonable practical power harvesting without damaging the harvester.