Nano-satellites are suitable for formation flight missions because of a lower cost and in a shorter development period than conventional-sized satellites. However, it is difficult for nano-satellites to use long-duration propulsion systems due to their strict constraints in terms of mass, volume, and power consumption. This research proposes a new method for formation keeping using differential plasma force. This plasma force is generated by the interaction between space plasma in the Earth's ionosphere and a magnetic field induced by a magnetic torquer for an attitude control system. Therefore, no additional components are needed for the relative orbit control. Plasma force is modeled on the basis of the results of Particle-In-Cell simulations in order to design a model-based controller and to compare with external perturbations including aerodynamic drag effect. A numerical simulation is performed to demonstrate the effectiveness of the proposed formation keeping for nano-satellite.
Aiming to the Mars exploration by flight vehicle, we have developed a new concept of parafoil type flight vehicle which has a high aerodynamic performance and a structural robustness, that is partial close type parafoil. However, the stability of this parafoil becomes worse than conventional ram-air type parafoil. Especially, severe lateral instability was observed in the drop test. To understand the stability characteristics, the analytical study focusing on the lateral stability was carried out based on the motion dynamic equation in a steady glide. The results indicate that increasing mean line length and high anhedral angle enhances its stability for spiral divergence. Moreover, in this study, this trend suggested by analysis is confirmed by the drop tests.
This paper considers controller design of large antenna servo systems, which is given by a new integral-type servo controller with gain-scheduled control for linear parameter-varying systems, while expanding to type-2 control with velocity tracking. An example of application is provided to demonstrate the effectiveness of the proposed method.
A dynamic bubble burst control plate with plate-height adjustment mechanism is aimed to suppress the stall by enhancing the vortex structure inside the laminar separation bubble formed on the airfoil. This dynamic bubble burst control plate is a dynamically oscillating rectangular cross section plate which is attached near the leading edge of the airfoil and the plate height can be altered. To improve the performance of stall suppression, a feedback control system of the plate oscillation was considered and machine learning control was applied to this system. In this paper, fundamental characteristic measurements of a NACA0012 airfoil with dynamic bubble burst control plate with a plate-height adjustment mechanism was conducted at a chord length Reynolds number of 1.3 × 105. Based on the results, the control system of this control plate was designed using genetic programming, which is a kind of machine learning. Further stall suppression effect by the gradual lift force decrease in the higher plate height was observed. The results of surface pressure measurement showed that this is due to the intermittent suction pressure recovery near the leading-edge. The control law designed by use of machine learning control enabled to suppress stall by attaining the gradual lift decrease with reduced plate oscillation.
Evaluation of electric propulsion propellant flow within ground test facilities (vacuum chambers) is necessary for research and development. In this study, a miniature rarefied dynamic pressure device was re-designed and developed. Through the evaluation and three-dimensional measurement within a vacuum chamber, it was confirmed that the device can detect the rarefied dynamic pressure with high resolution regardless the mounting attitude, the chamber wall reflection flow affects the propellant flow in the whole region of the chamber, the vacuum pump evacuation influences the propellant flow in the downstream region, and both the position and the attitude of the thruster was important for the thruster performance evaluation.