Recently, there appeared new materials with light and high strength characteristics. And some concepts of balloon or kite with flying ability of more than sixty thousands feets height have already been proposed by applying these new materials to the tethering cable. Some investigation of these high altitude tethering capability are made by finding a similarity rule for tether cable and by computer analysis in this paper. As a result, it is verified that a large scale kite with around 100m span may show those high performances.
Plasma diagnostic measurement and flowfield analysis in a quasi-steady coaxial magnetoplasmadynamic (MPD) channel realizing a one-dimensional flowfield were conducted for understanding blowing acceleration. Axial variations of current, electron temperature and electron number density in an MPD channel were measured, and these experimental results for Ar roughly agreed with analyzed ones. As a result, it was expected, from the axial profiles of Lorentz forces inferred from the measured current distributions and the calculated plasma velocities, that there existed two acceleration zones near the inlet and outlet at high magnetic Reynolds numbers. Furthermore, it was predicted from numerical analysis that nonequilibrium ionization process enhanced electromagnetic acceleration through the channel.
Feedback control tests were carried out to improve flame-holding performance in a fixed-geometry scramjet combustor. When the combustor geometry was fixed, pressure oscillation and/or blow-off occurred easily by small changes of the main airflow condition and the equivalence ratio. These phenomena could be improved by changing the combustor geometry according to the conditions. Hence, instead of mechanical transformation, four air injectors were installed on the combustor wall and the secondary air was injected into the boundary layer which developed on the combustor wall in order to control the effective cross sectional area of the combustor. Signals from pressure transducers on the combustor wall were used as feedback signals. The present control system worked effectively for improving pressure oscillation and/or blow-off and could respond for rapid change of the condition. It was also valid for improving self-ignition limit.
The movement of a satellite-mounted manipulator can disturb the attitude of the satellite, and the inertial parameters of the system change with the configuration of the manipulator. In the proposed control method, this disturbance is absorbed by using feedforward control based on estimation of the manipulator angular momentum, and further errors are removed by using feedback control with gains that change according to the inertial parameter variations of the system. Our algorithm greatly reduces the number of calculations due to the use of a simplified model derived from a better understanding of some particular properties of space robots. Stability of the proposed control system is guaranteed by constracting a Lyapunov function.
Two design considerations to the exact linearization method that yield a robust controller to parameter variations are proposed. The first one is that the feedback gains using exact linearization are determined to be equal to those of the linear approximated design. This means that the closed-loop system has no less robustness than the corresponding linear approximated design. Another design consideration is based on the idea that two vector fields before and after the nonlinear transformation are made to be equal each other near the design point. Thus, the transformed system retains the original stability characteristics. The first consideration is then used to design a nonlinear controller of an aircraft with a jump phenomena due to roll coupling. The equations of motion are examined from viewpoint of exact linearization, and the required ransformation is obtained analytically. The designed controller is examined for the control input magnitude and parameter variations, and the robustness is compared with a linear controller.