This paper considers a model-following controller with optimal disturbance attenuation. The controller design process follows a similar approach to the MDM/MDP (Multiple Delay Models/Multiple Design Points) design method, in which the controller performance is evaluated only at selected design points and optimization is performed numerically. Unlike the MDM/MDP method, however, performance is evaluated over the whole range of uncertainties, and is optimized with a method which has a convergence property. In this design process, the performance of the disturbance attenuation is defined as a quadratic cost function and the design problem is formulated with one convex and one non-convex condition, but this is not easily solvable. A design procedure that uses an iterative algorithm, which is easily solvable and has the convergence property, is presented to render the problem tractable. Next, model-following controllers for the lateral/directional motions of MuPAL-α, one of the National Aerospace Laboratory’s flight experiment aircraft are designed with the proposed method, and the results of flight experiments to verify their performances are presented.
A torsional-type thrust stand has been designed in order to measure precisely the impulse bits produced by low-power pulsed plasma thrusters. The stand is capable of measuring impulse bits ranging from 10 to 1,000 μNs in vacuum conditions. Investigations concerning extremely low impulse measurement have encountered difficulties in the past due to undesired vibrations of the measuring facility. The relation between the background noise and the excited vibrations to the thrust stand is considered and it is shown that an optimum damping ratio exists which provides a maximum SN (signal-to-noise) ratio.
This paper considers application of the right inverse system in the design of model-matching controllers. In practice, it is impossible to apply the ideal right inverse system to a strictly proper system, such as linearized airplane motions, because differentiators are required. However, considering that there is no need for the right inverse property to hold over all frequency ranges, a filtered right inverse system that has the right inverse property only in the low frequency range is adopted. To investigate their practical application, several filtered right inverse systems were designed as model-matching controllers for the lateral/directional motions of NAL’s MuPAL-α flight research aircraft, and their model-matching performances were examined by simulations. These examinations confirmed that when a higher fidelity system model is used to design the controller, the controller exhibits better performance but noise may be amplified by the inverse system, limiting its ultimate usefulness. There is therefore a trade-off between performance and practicality in designing controllers using the right inverse system. Subsequent flight experiments verified that suitably designed model-matching controllers for the longitudinal and lateral/directional motions of MuPAL-α gave good performance.
The observing method that uses ENA (Energetic Neutral Atom), produced by Charge Exchange Collision, is studied and researched by ISAS in order to estimate the density of neutral particles in the upper atmosphere. Its method is called ENA observation. At present, the ENA observation is done by Charge Exchange Collision between neutrals in the upper atmosphere and the ions in the magnetospheric ring current field that is activated by solar wind. But in this method, it is difficult to separate the informations between neutrals and ions from ENA data because the ions in the magnetospheric ring current field are the natural origin and their energies are not constant. In this study, we propose the new method of ENA observation that uses ions exhausted from ion thruster. Ions from ion thruster are the artificial ones and are more suitable for ENA observation because their energies and densities can be controlled. We evaluate the possibility of application of ion thruster’s exhausted ions to ENA observation. Analytical results show the range of altitude and the operating conditions of ion thruster that this method effectively can apply.
A new flying quality criterion and a quadratic performance index with time weighting matrix are introduced. The H∞ controller design satisfies these requirements is shown. This design method contains several parameters with which many features of time responses can be adjusted easily. Finally the proposed method is applied to MuPAL-α.
The unsteady flow oscillation caused by the wake vortices generated from a number of objects is a meaningful theme for the fluid dynamics and aeroacoustics. The discrete vortex method has been used for a variety of incompressible high Reynolds number flows as a simple numerical simulation method, and this method has a merit in a point of easy treating for wake vortices. So discrete vortex method is often used for cascades flow, but it has a difficulty in directly applying for stator-rotor interaction because it could cause a locally unnatural flow by the interaction between wake vortices and bounded vortices expressing surfaces of objects. In this paper a suitable method using a sub-element method is applied not to spoil the basic algorithm and essential merit of the discrete vortex method and an investigation the basic mechanism of the interaction between stator and rotor is performed.
Quasi-zenith satellite system attracts the attention recently, at least one satellite of which is in high elevation angle. Large capacity communication system and GPS augmentation system using quasi-zenith satellite system are proposed. GPS augmentation satellites in high elevation can improve integrity capability and navigation accuracy of GPS. In the first half of paper, I show the constellation design of quasi-zenith satellite system to optimize for Japan. In the last half, I show the GPS augmentation effect by designed quasi-zenith satellite system.
The propulsive characteristics of water rockets are analyzed theoretically and experimentally. The unsteady thrust force acting on a PET bottle and the air pressure inside the bottle are measured simultaneously by the thrust test stand we have developed. The semi-empirical thrust history is obtained utilizing the air pressure history and it is compared with the measured thrust history. The results show qualitative agreement. The observation of the flow inside bottle by a high-speed video camera shows that the air precedes water when it is about to be discharged entirely. We have developed a flow regulator attached to the nozzle cap to reduce the precursor air discharge that is considered as a result of the swirling flow inside the bottle. The experimental results show that the air discharge and the body vibration are suppressed effectively.
Manual tracking experiments were carried out. The pilots tried to track the random reference input and commented the workload of control. Pilot models were identified and the philosophy of pilot control was derived. Using the philosophy, controller design method with standard pilot model, which improves the workload, is proposed. Standard pilot model can be given arbitrarily and controller is designed so that standard pilot model can control the plant easily. Design method was applied to the plant, which is difficult to be controlled by pilot, the decrease of workload was confirmed.
Improvements of the take-off and climb performance of the next generation supersonic transport (SST) are one of the key features for the SST development. Take-off and climb performances have been estimated for the cranked-arrow-wing SST configuration when the leading-edge vortex flaps and the trailing-edge flaps are deflected. Results show that the take-off distance and the balanced field length are reduced when the trailing-edge flaps are deflected, as expected. The thrust required for the constant climb gradient can be reduced when the leading-edge vortex flaps and the trailing-edge flaps are deflected at the same time.