The present paper treats a technique of vibration measurement and control based on the optimal placement of sensors and actuators. In the second report of this paper, the experimental verification of vibration measurement and control for CFRP laminated plates is carried out using a modal sensor and a modal actuator. The modal sensor is constructed using accelerometers, based on the criterion of minimum observation spillover, while the modal actuator is constructed using PZT piezoelectric materials, based on the criterion of minimum control spillover. Some experimental results demonstrate that the optimal placement of sensors and actuators is very important to stabilize a control system for a limited number of sensors/actuators, and the vibration of laminated plates can be suppressed effectively by state feedback control for each mode using the modal sensor and actuator.
The experiment on aircraft spin phenomena was conducted at the low speed wind tunnel of Nagoya University with its exit test section inclined vertically. The model used in this experiment consists of three parts: a main wing, a fuselage, and a tail. Due to the stability effect of the tail, rotation of the model is decreased at low angles of attack, while it is increased at high angles of attack. As a result of pressure measurements, the horizontal tail wing was found to be the cause of this phenomenon. More specifically, a vortex is created from the leading edge of the windward horizontal tail wing, so that negative pressure regions appear on the windward horizontal wing and the vertical wing.
Two-dimensional large deflection of the initially deformed beam is theoretically and numerically analyzed. Effects of the geometrical non-linearity due to thickness and radius of the beam are considered on the derivation of the strain equation. The equilibrium equations are derived by applying non-extensional assumption at the neutral axis as used in the Elastica. The numerical examples are performed to investigate the effects of the ratio of thickness to radius on the total deformations and the ratio of non-dimensional maximum stress of proposed analysis to that of Elastica. The deformation of the beam calculated by the proposed analysis becomes smaller and non-dimensional stress ratio calculated by the proposed analysis becomes larger for larger ratio of thickness to radius.
Numerical analyses were performed to clarify the power conversion mechanisms in a 1kW class Continuous-Wave (CW) laser thruster. Laser plasma heating and radiation emission from the plasma, which dominate in the power conversion balance, were highlighted in the analyses. Calculation results showed that low laser power absorption and large radiation loss from the plasma cause low thruster performance. These results also showed that optimization of the nozzle shape and use of regenerative-cooling can substantially improve the thruster performance.
The Pitot probe with 5-hole pyramidal head originally developed by NAL was planed to be adopted in the early phase of the development of the High-Speed Flight Demonstration Phase II. But it was turned out that the probe could not achieve enough ability of Mach number measurement at high altitude condition. To improve the ability of the ADS, pressure holes were added on the aft surface of the probe. As the result, the error of Mach number measurement due to the errors of pressure sensors became 2.7% of an original error at best condition, and the new probe could achieve adequate accuracy of Mach number.
This paper presents a design method of reconfigurable flight control systems based on the coprime factorization method. The baseline robust control system is designed using the normalized coprime factorization method. The identification method employed is a closed-loop one, which is also based on coprime factorization; therefore, the method is suitable to the robust control system. The ν-gap metric is chosen as a criterion that indicates the effects of failures on stabilizability of the robust control system. The ν-gap metric can be computed using the identified parameters. To illustrate the effectiveness of the control and identification method, a design example and simulation results for the F-18 HARV are shown.
The authors have proposed an advanced fuel configuration to overcome the defect of conventional hybrid rockets, i.e., the low thrust level. The key feature of this new type of hybrid rocket, named Cascaded Multi-staged Impinging jet (CAMUI), is that the cylindrical fuel blocks with two ports parallel to the axis are arranged in a row in the combustion chamber. This fuel configuration allows mixing and combustion to occur in and around the impinging jet regions. In the present paper, a CFD simulation clarifies the fundamental features of the flow field and the heat transfer distributions in the CAMUI hybrid rocket grain. Following results are obtained: Higher heat transfer occurs near the edge of the impinging jet region. A fountain flow caused by the collision of the wall jets enhances the heat transfer on the backward end of the upstream fuel block. A semi-cylindrical swirling flow appearing near the inlet of the fuel port increases the convective heat transfer in this region.