Design of controller switching strategy for reusable launch vehicle with elevon jamming failure

When a reusable launch vehicle (RLV) returns to earth, it flies just by gliding without thrust. In this phase, one of the most likely and important faults to occur in the airframe is a jamming of the elevon. To tolerate this failure, the flight control system must keep stability and performance during such a failure. One of the effective ways to overcome this problem is to switch the controllers based on the information of the detected failure in the plant. Generally speaking, the controller must have integrators so as to yield the zero steady‐state error for the controlled output even if there exist some perturbations in the plant dynamics. In this paper, the design of controller switching scenario is addressed especially focusing on the decision of the controller state at the instant of switching the controllers with integrator. Then, the proposed switching scenario is applied to the control of ALFLEX (Automatic Landing FLight EXperiment), which is the automatic landing experimental vehicle being developed for RLV, considering the occurrence of the jamming fault. Some simulations are shown to verify the usefulness of the proposed idea. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 164(2): 80–90, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20356     

An improved thermal response test for U-tube ground heat exchanger based on optical fiber thermometers

As part of a new thermal response test (TRT) and to determine ground thermal conductivities, vertical temperature profiles were obtained using retrievable optical fiber sensors inserted into the U-tubes of two ground heat exchangers (GHEs) installed at Maebaru City (Fukuoka, Kyushu) and Kushiro City (Hokkaido), Japan. Measured profiles and outlet temperatures from TRTs were history-matched with the cylindrical source function. Nonlinear regression was used to estimate the vertical distribution of ground thermal conductivities. The computed distribution is consistent with measured data indicating both the reliability of the optical fiber thermometer and TRT interpretation. It is expected that TRTs and optical fiber thermometers will prove to be increasingly useful for optimizing the depth of the GHEs installed in heterogeneous formations, and consequently will minimize installation costs of geothermal heat pump systems.     

Simple purification and selective enrichment of metallic SWCNTs produced using the arc-discharge method

Purified single-walled carbon nanotubes (SWCNTs) were produced using the arc-discharge method with a combination of air oxidation and dispersion–centrifugation processes in a tetrahydrofuran solution containing an amine as a dispersant. Subsequently, SWCNT samples were analyzed using thermo gravimetric analysis, vis-near infrared absorption spectroscopy, scanning electron microscopy, and Raman spectroscopy. Results revealed that metallic SWCNTs were enriched in a supernatant through the dispersion–centrifugation process.     

Application and monitoring of SF6 gas‐insulated NGR (neutral grounding resistor) using ceramic resistors

About 15 years have passed since ceramic‐resistor NGRs (Neutral Grounding Resistors) were developed as new materials for power equipment. This paper describes the cumulative numbers of applications of ceramic‐resistor‐type SF₆ gas‐insulated NGRs and the typical construction of the 22‐, 66‐, and 110‐kV NGRs, and also describes monitoring methods for measuring the residual leakage current of the 110‐kV NGR that depend on the neutral unbalance voltage of power transformers, and the use of thermal detection devices for the ceramic resistors of the 66‐kV NGRs. © 2001 Scripta Technica, Electr Eng Jpn, 137(4): 32–37, 2001     

Effect of gas composition on metal surface cleaning using atmospheric pressure microwave plasma

A microwave excited atmospheric pressure plasma source was manufactured and a cleaning experiment involving a stainless steel plate contaminated with organic oil was conducted, while considering the radical density in the Ar, Ar-O₂, and Ar-H₂O plasma. The most notable cleaning effect was confirmed when the plasma contained water molecules. While the existence of a unique spatial distribution of OH radical was demonstrated, the relevance of the cleaning effect and radical density was confirmed. The radical density distribution was examined by numerical computation using the experimentally obtained plasma parameter.     

Electric and microstructural characteristics of bulk ZnO fabricated by underwater shock compaction

An underwater shock compaction of pure zinc oxide (ZnO) powder has been performed. This technique uses an underwater shock wave generated by detonation of an explosive. Shock pressure used in this work was about 10 GPa. The morphology and structure of shock-consolidated ZnO was investigated by X-ray diffraction (XRD) method and scanning electron microscopy (SEM). The density and impedance characteristics of shock-consolidated ZnO were measured by Archimedes method and Nyquist plot method, respectively. The shock-consolidated ZnO without visible cracks was successfully obtained. It was confirmed that the shock-consolidated ZnO had 99% of theoretical density without grain growth and high grain boundary resistivity in comparison with the commercial sintered ZnO.