Recently, the Plant Input Mapping (PIM) method was proposed as a digital-redesign (or an emulation) approach in digital control system design. This method guarantees stability of a redesigned digital control system for a wide range of sampling periods. In this paper the PIM method is applied to the design of a digital model-matching flight control system. In the model-matching control system design a plant must have no unstable zeros. However, unstable zeros appear for small sampling periods in a step invariance model of a continuous-time (CT) plant with the relative degree greater than two, even if the CT plant has no unstable zeros. Hence, in such a case, the direct-digital approach cannot be applied to the design of a digital model-matching control system. By contrast, the digital-redesign approach such as the Tustin's method or the PIM method is free from the problem. Simulation results for an unstable VTOL aircraft show that the proposed method gives better performance than the conventional design methods.
A systematic computation scheme is presented for PAR-WIG cruising performance, on a FORTRAN program. It is suitable to be executed on personal computers. Effect of many parameters on the transportation efficiency is explored. Two concepts are presented as three views and artist impressions. One is a smallest single-crewman vehicle for experiment, sports or pleasure. The other is a large vehicle for civil transportation. The both have twin hulls, which is quite suitable to equip “Small-Tail-WIG” or “WIG-let” to establish longitudinal attitude stability.
A three-dimensional calculation incorporated with the Baldwin-Lomax turbulent model was conducted to investigate internal flows in scramjet nozzles and the interference with external flows. The numerical results were compared with experimental results on the pressure, heat flux distributions and the friction loss. The numerical and experimental results revealed complex variations of nozzle performance by the crossing shock-waves and the secondary flow caused by the external flows. The calculations predicted the internal and the external loss within a discrepancy from the experimental results by about 4%.
A new low vibration rotor blade design methodology using modal based structural optimization is proposed. The blade is substituted for a cantilevered rotating plane tapered beam subjected to sinusoidally varying distributed loads. Structural optimization problems to minimize dynamic loads and moments at the blade root are formulated as non-linear optimal control problems in continuous system and their optimum cross sectional area distributions are determined numerically by SCGRA. The features of this procedure are (1) in favor of modal approach, the low vibration blade design problems can be practicable by treating each blade mode separately, (2) utilizing the modal equation as one of equality constraints imposed on the problem, there is no necessity to specify the natural frequency ranges in advance and feasible natural frequency ranges are determined automatically during numerical processes. Numerical studies are conducted for five different kind of combinations of objective functions, constraints for minimum cross sectional area and exciting frequencies of external loads. To clarify the effects of structural optimization to vibration reduction, optimum solutions are compared with numerical results for a uniform blade. It is revealed that little difference can be recognized between the optimum solutions to minimize vertical shear force and those for out of plane moment. However, for optimum area distributions, large difference can be found depending on dominant vibration modes which are related to the exciting frequencies of external loads.
The LE-7 engine, the first stage main engine for the H-II rocket, has been developed in Japan. During the development, there were some troubles in the various welded joints. In the previous report, the tensile properties of the Inconel-718 welded joints, solution treated at 1228K, were reported. In this report, the micro-structures, the hardnesses and the tensile properties of the Inconel-718 welded joints with various solution treatment conditions were investigated and compared with the previous results. It was observed that the dissolution of Ni3Nb phases in the welded metal, which reduced the ductility, and the grain growth in the parent metal occurred simultaneously, and that the break point in the specimen shifted from the welded metal to the parent metal as the solution treatment temperature increased from 1228K to 1338K.