Comparison of upwind and downwind rotor operations of the DOE/NASA 100-kW Mod-O wind turbine

Three aspects of the test results are compared: rotor blade bending loads, rotor teeter response, and nacelle yaw moments. As a result of the tests, it is shown that while mean flatwise bending moments were unaffected by the placement of the rotor, cyclic flatwise bending tended to increase with wind speed for the downwind rotor while remaining somewhat uniform with wind speed for the upwind rotor, reflecting the effects of increased flow disturbance for a downwind rotor. Rotor teeter response was not significantly affected by the rotor location relative to the tower, but appears to reflect reduced teeter stability near rated wind speed for both configurations. Teeter stability appears to return above wind speed, however. Nacelle yaw moments are higher for the upwind rotor but do not indicate significant design problems for either configuration

Engine Yaw Augmentation for Hybrid-Wing-Body Aircraft via Optimal Control Allocation Techniques

Asymmetric engine thrust was implemented in a hybrid-wing-body non-linear simulation to reduce the amount of aerodynamic surface deflection required for yaw stability and control. Hybrid-wing-body aircraft are especially susceptible to yaw surface deflection due to their decreased bare airframe yaw stability resulting from the lack of a large vertical tail aft of the center of gravity. Reduced surface deflection, especially for trim during cruise flight, could reduce the fuel consumption of future aircraft. Designed as an add-on, optimal control allocation techniques were used to create a control law that tracks total thrust and yaw moment commands with an emphasis on not degrading the baseline system. Implementation of engine yaw augmentation is shown and feasibility is demonstrated in simulation with a potential drag reduction of 2 to 4 percent. Future flight tests are planned to demonstrate feasibility in a flight environment

Lateral ride quality of the B-1 aircraft subjected to a reduction of lateral static stability

A method to evaluate the lateral ride quality of a B-1 aircraft subjected to a reduction in lateral static stability is developed. Ride quality is then found for three different relaxed static stability configurations which are augmented by yaw rate feedback to restore specified handling qualities. These cases are compared to the ride quality of the unrelaxed aircraft with the same handling qualities

Pemodelan Simulasi Berbasis Fuzzy Controller Terhadap Perilaku Yaw Rate Dengan Pengendalian Sudut Steer Roda Belakang (4WS)

Four Wheels Steering System drives (4ws) are increase ones quality of chassis system as propose improve the handling quality and increase the safety, comfortable, and stability control at the highest of vehicle speed. At the time of vehicle move yaw-rate will arise out because caused by tire characteristic and it is give effect to loss of handling quality and stability of vehicle. As control the effort of vehicle performance cause by yaw-rate effect on chassis system that it is use turn the rear wheel of vehicle, which capable to make an opposite direction or same direction with front wheel steering. The controlling of rear wheel turn on 4WS system is used side-slip control method and DC motor of position angle actuator so real yaw-rate will always neutral position of yaw. In this research is applicative the simulation modeling that conducted by utilize the fuzzy controller from Mat-Lab 6.5. As the result of the modeling simulation turn direction rear wheel give a most advance and effect to vehicle in handling the stability and yaw rate effort, so vehicle always stable when turn effort

MOD-0 wind turbine dynamics test correlations

The behavior of the teetered, downwind, free yaw, MOD-0 wind turbine, as represented by NASA dynamic test data, was used to support confidence in the Hamilton Standard computer code simulations. Trim position, performance at trim, and teeter response as predicted by the computer codes were compared to test results. Using the computer codes, other possible configurations for MOD-0 were investigated. Several new test configurations are recommended for exploring free yaw behavior. It is shown that eliminating rotor tilt and optimizing cooling and blade twist can contribute to good free yaw behavior and stability. The effects of rotor teeter, teeter gravity balance, inflow and other physical and operating parameters were also investigated

Transonic aerodynamic damping and oscillatory stability in yaw and pitch for a model of a variable-sweep supersonic transport airplane

Transonic aerodynamic stability and damping in yaw and pitch for variable sweep supersonic transport mode

Simulator study of the effectiveness of an automatic control system designed to improve the high-angle-of-attack characteristics of a fighter airplane

A piloted, fixed-base simulation was conducted to study the effectiveness of some automatic control system features designed to improve the stability and control characteristics of fighter airplanes at high angles of attack. These features include an angle-of-attack limiter, a normal-acceleration limiter, an aileron-rudder interconnect, and a stability-axis yaw damper. The study was based on a current lightweight fighter prototype. The aerodynamic data used in the simulation were measured on a 0.15-scale model at low Reynolds number and low subsonic Mach number. The simulation was conducted on the Langley differential maneuvering simulator, and the evaluation involved representative combat maneuvering. Results of the investigation show the fully augmented airplane to be quite stable and maneuverable throughout the operational angle-of-attack range. The angle-of-attack/normal-acceleration limiting feature of the pitch control system is found to be a necessity to avoid angle-of-attack excursions at high angles of attack. The aileron-rudder interconnect system is shown to be very effective in making the airplane departure resistant while the stability-axis yaw damper provided improved high-angle-of-attack roll performance with a minimum of sideslip excursions

Stability of Monomer-Dimer Piles

We measure how strong, localized contact adhesion between grains affects the maximum static critical angle, theta_c, of a dry sand pile. By mixing dimer grains, each consisting of two spheres that have been rigidly bonded together, with simple spherical monomer grains, we create sandpiles that contain strong localized adhesion between a given particle and at most one of its neighbors. We find that tan(theta_c) increases from 0.45 to 1.1 and the grain packing fraction, Phi, decreases from 0.58 to 0.52 as we increase the relative number fraction of dimer particles in the pile, nu_d, from 0 to 1. We attribute the increase in tan(theta_c(nu_d)) to the enhanced stability of dimers on the surface, which reduces the density of monomers that need to be accomodated in the most stable surface traps. A full characterization and geometrical stability analysis of surface traps provides a good quantitative agreement between experiment and theory over a wide range of nu_d, without any fitting parameters.Comment: 11 pages, 12 figures consisting of 21 eps files, submitted to PR