Normal force and rolling moment acting on a delta wing in forced sinusoidal rolling oscillation are measured in low speed wind tunnels. Flow visualization revieled details of the separated vortices. With increasing the rolling frequency, the normal force and the rolling moment show, within a cycle of motion, large hysteresises which due to time lag in leading edge separated vortices to follow the moving wing surface. The amplitude of hysteresis increases with angle of attack, up to the angle at which the vortex breakdown reaches the trailing edge of the wing. Beyond this angle nonlinearities are introduced by the vortex breakdown. The effect of breakdown is studied using a mathematical model. The result shows that the time lag in vortex movement ends in positive energy supply from free streams and the one in asymmetric vortex breakdown suppresses this.
This paper presents a higher order theory for bending of homogeneous orthotropic elastic plates. The inplane stresses are expanded into series of the Legendre polynomials in the thickness coordinate. The thicknesswise stresses are given as a result of integration of the equilibrium equations of three-dimensional elasticity. The series are truncated so as to contain terms up to the third order. The plate variables are defined and the governing equations as well as the boundary conditions are formulated by means of weighted integral and the principle of complementary energy. The theory consists of 16 governing equations for 16 dependent variables and 6 boundary conditions. If the third order terms are neglected, it reduces to the Reissner type theory. If the Poisson-Kirchhoff hypothesis is introduced, it further reduces to the classical theory.
This paper presents a new digital adaptive control design for the CCV that has unstable zeros. In recent years, designs for digital control systems have been developed that showed good responses for the Japanese T2-CCV. However, the deflection of the actuators resulted in severe vibration, because the zeros of the CCV impulse transfer function were quite close to the unit circle boundary in the Z plane. Most of the proposed scheme for non-minimum phase systems have been adaptive pole-placement methods. In this paper, we schemed a design for the model reference adaptive flight control system using a placement method for zeros of the CCV. The method adds the vertical acceleration to the vertical speed signal, and pitch rate and pitch acceleration to the attitude signal from the CCV so as to move the zeros to a more stable region. Computer simulations were performed on the T2-CCV and showed remarkable adaptability and resulted in satisfactory CCV modes without any unstable vibration of the flaperon or the elevator.
Application of periodic optimization to minimum fuel aircraft trajectories is discussed. The most part of a long range trajectory is a cruise segment, which is assumed to be a steady flight in many papers. The steady condition is one of the constraints which lower optimality. In this paper, the optimum cruise segment is considered as an unsteady flight. The cruise segment is devided to subarcs in which same control sequences are used. The solution of minimum fuel problem for the subarc optimizes a total trajectory. The periodic optimization has some advantages in an operation. Zero-order approximate solution is presented as a maximum thrust ascent and a minimum thrust descent. This solution indicates the limitation of the exact one when the final range is specified infinite. Numerical results show the periodic cruise can save fuel 3-4% decrease.