This paper presents an automatic flight-path control of aircraft. In the control, a desired flight trajectory is first determined as a sequence of straight lines, arcs and spirals in the three-dimensional space. Commands and command rates of heading and flight-path (climb) angles are then obtained from the desired trajectory. A required acceleration vector of the aircraft is calculated based on the command rates and angle deviations. Desired roll, pitch and yaw rates are then obtained by acceleration controller and are fed to attitude control. The feedback control of acceleration employs conventional PID control technology, without using inverse dynamics of the aircraft, and the attitude control can employ any existing control technologies suitable for the aircraft to be controlled. These make the proposed control relatively simple and easy to implement. Numerical simulations illustrate the effectiveness of the control.
In aerospace projects preflight evaluation is crucial for mission success, because flight testing in a real environment is often difficult or impossible. Monte Carlo simulation is a powerful tool for the preflight evaluation because a nonlinear system incorporating various uncertain parameters can be evaluated directly. Monte Carlo simulation has been used in various aerospace projects throughout the world as the computer power increases. After the system evaluation, it is important to detect influential uncertain parameters which cause significant performance degradation so that measures for the system improvement can be studied. However, detecting those parameters is often uneasy because various uncertain parameters are incorporated simultaneously and their magnitudes are randomly generated in Monte Carlo simulation. An interaction of more than two uncertain parameters might be affected. This paper presents a simple approach to detect influential uncertain parameters applying a statistical test to the Monte Carlo results.
Experimental and numerical studies of the interaction between combustion of a hydrogen jet and an incident shock wave were performed. In the case that an incident shock wave was introduced upstream of the injection slot, the boundary-layer separation region was extensively expanded. The penetration height of the Mach disk with an incident shock wave was less than that without an incident shock wave. Combustion was confirmed when the incident shock wave was introduced downstream of the fuel injection slot, while, with the incident shock wave upstream of fuel injection slot, combustion was not confirmed. The mechanism of these phenomena was discussed based on the results of numerical simulation in terms of the residence time in the separation region near the fuel injection slot.
A one-dimensional numerical simulation was conducted inside an anode layer type Hall thruster in order to clarify the nature of low frequency discharge oscillation in Hall thrusters. The model assumed quasi-neutrality, Maxwellian electron distribution, and classical and Bohm diffusions across magnetic field lines. Heavy species were simulated using Particle-in-Cell (PIC) method, and electrons were dealt as fluid continuum. Generalized Ohm’s law was used to determine the electric potential, and an electron energy equation was solved to determine the electron temperature. As a result, we obtained discharge oscillations which were caused by ionization instability. The calculated current, its oscillations, and the stable operation range agreed with measured ones. We also succeeded to simulate the transition from the classical diffusion mode to Bohm diffusion mode by the calculation. In the discussion, it is shown that the electron energy given by the electric field has the large effect on the current oscillation.
In this paper, we describe the surface error of pseudo-parabolic surface, to construct an inflatable parabolic reflector. The gore sheet is generated by cutting the three-dimensional parabolic surface. A scheme of generating the gore sheet is described, and the rms surface error between the parabolic surface and the three-dimensional shape composed of the gore sheets is proposed and formulated. The rms surface error between the parabolic surface and the shape produced by pressurizing the circular membrane is also formulated. Finally, the possibility that the parabolic reflector composed of the gore sheets has high surface accuracy is shown.
Experimental investigations have been made on the mode I interlaminar fracture toughness (GIC) of stitched CFRP (carbon fiber reinforced plastic) laminates. The GIC of stitched CFRP laminates fabricated by resin transfer molding (RTM) and stitching with five kinds of stitch thread thicknesses, 400d (denier), 600d, 800d, 1000d, and 1200d were experimentally obtained by double cantilever beam (DCB) tests. Interlaminar tension tests for stitched CFRP laminates for a specimen containing only one stitch thread were also carried out. The consumption energy of the single stitched CFRP laminates (Wt) and stitch threads broken modes were obtained by such interlaminar tension tests. DCB test results show that the GIC of stitched CFRP laminates of several stitch thread thicknesses are governed by stitch density (SD). It is found that the relationship between ΔGIC/ΔSD and Wt are linear function. In other words, the GIC of Kevlar® stitched CFRP laminates is not only governed by SD but also Wt obtained from the interlaminar tension tests. It is also suggested that the interlaminar tension test results exhibit the potential for GIC estimation on the Kevlar® stitched CFRP laminates instead of conducting the DCB tests.
A computational program using a CFD-CSD coupled method has been developed to study the problem of low supersonic curved panel flutter. So far the supersonic aerodynamic model has been commonly employed to compute flutter boundaries. However, the present CFD-CSD coupled method makes it possible to analyze flutter boundaries at all speeds including transonic speeds. The computed flutter dynamic pressure for M∞=3 agrees with others’ results. A curved panel flutter were analyzed at a low supersonic speed, M∞=1.2. The flutter for small curvature panels is first-mode flutter, which is similar to flat panel flutter, whereas it becomes higher-mode flutter for larger curvature plates. In this study, flutter boundaries for an access panel have also been simulated. Its critical dynamic pressure becomes significantly lower compared with the case of a panel with its all edges simply supported.
Torque acting on a blade of a coaxial helicopter was estimated by measuring a lead-lag angle of the blade. The estimated torque was compared with the one measured by referring the characteristics of the motor. The comparison shows that the former method has the same accuracy as the latter method.