Browsing by Subject "Flexible Vehicle Modeling"

Now showing 1 - 4 of 4
  • Thumbnail Image
    Item
    Flight-Dynamics, Flutter, and Active-Flutter-Suppression Analyses of a Flexible Flying-Wing Research Drone
    (As presented at the NASA Armstrong Flight Research Center Edwards AFB, CA, 2015-06-15) Schmidt, David
  • Thumbnail Image
    Item
    Flight-Dynamics, Flutter, and Active-Flutter-Suppression Analysis of a Flexible Flying-Wing Research Drone
    (Aerospace Flutter and Dynamics Council (AFDC) Meeting, Spring 2015, 2015-04-16) Schmidt, David
  • Thumbnail Image
    Item
    MATLAB-Based Flight-Dynamics and Flutter Modeling of a Flexible Flying-Wing Research Drone
    (2015-05-19) Schmidt, David
    A relatively low-order, linear dynamic model is developed for the longitudinal flight- dynamics analysis of a flexible, flying-wing research drone, and results are compared to previously published results. The model includes the dynamics of both the rigid-body and elastic degrees of freedom, and the subject vehicle is designed to flutter within its flight envelope. The vehicle of interest is a 12-pound unmanned, flying-wing aircraft with a wingspan of 10 ft. In the modeling, the rigid-body degrees of freedom (DOFs) are defined in terms of motion of a vehicle- fixed coordinate frame, as required for flight-dynamics analysis. As a result, the state variables corresponding to the rigid-body DOFs are identical to those used in modeling a rigid vehicle, and the additional states are associated with the elastic degrees of freedom. Both body-freedom and bending-torsion flutter conditions are indicated by the model, and it is shown that the flutter speeds, frequencies, and genesis modes suggested by this low-order model agree very well with the analytical predictions and flight-test results reported in the literature. The longitudinal dynamics of the vehicle are characterized by a slightly unstable Phugoid mode, a well-damped, pitch-dominated, elastic-short-period mode, and the stable or unstable aeroelastic modes. A classical, rigid-body, short-period mode does not exist.
  • Thumbnail Image
    Item
    Stability Augmentation and Active Flutter Suppression of a Flexible Flying-Wing Drone
    (2015-05-19) Schmidt, David
    Integrated control laws are developed for stability augmentation and active flutter suppression (AFS) of a flexible, flying-wing drone. The vehicle is a 12-pound unmanned, flying- wing research aircraft with a 10 ft wingspan. AFS is flight critical since the subject vehicle is designed to flutter within its flight envelope. The critical flutter condition involves aeroelastic interactions between the rigid-body and elastic degrees of freedom; hence the control laws must simultaneously address both rigid-body stability augmentation and flutter suppression. The control-synthesis approach is motivated by the concept of Identically Located Force and Acceleration (ILAF), successfully applied on some previous operational aircraft. Based on the flutter characteristics and on conventional stability-augmentation concepts, two simple loop closures are suggested. It is shown that this control architecture robustly stabilizes the body- freedom-flutter condition, increases the damping of the second aeroelastic mode (which becomes a second flutter mode at higher velocity), and provides reasonably conventional vehicle pitch- attitude response. The critical factors limiting the performance of the feedback system are identified to be the bandwidth of the surface actuators and the pitch effectiveness of the control surfaces.