This paper deals with a control strategy to attenuate the rotational motion of a target satellite with a manipulator mounted on a free-flying space robot. First, we approximate an impact force and a friction force between the manipulator and the target satellite with smooth functions. Then, the motions of the space robot and the target satellite are given by equations of motion. Next, we design a feedback control law of joint torques with nonlinear model predictive control. We also propose a performance index for determining the pushing and pulling of the manipulator according to the angular velocity of the target satellite. Finally, numerical simulation shows the effectiveness of this control law.
Enhance of combustion efficiency of the hydroxyl ammonium nitrate (HAN)-based green monopropellant is an important topic for improving the capability of green propellant reaction control system (RCS) to achieve practical use. This paper conducts the atomization of HAN-based monopropellant SHP163 by the effect of flashing or flash atomization. Flashing is the atomization method using the pressure difference between the saturation pressure of a liquid and the ambient pressure. This paper reports the result of the injection test of SHP163 in different ambient pressures from atmospheric to near-vacuum and the catalytic thruster combustion test of SHP163 in two different pressures, atmospheric and near vacuum, and describes the effect of the flashing of green propellant for its catalytic combustion efficiency.
The reduction of N/rev vibration of rotorcraft can be accomplished using the CG offset. It is desirable if lateral CG offset is movable, and by considering the difficulties of moving CG laterally, the cant rightward of a main rotor shaft has been proposed in this paper. Moving the CG longitudinally is easier than doing so laterally, but it is still also preferred to have an alternative way. Here, the negative horizontal stabilator setting angle was introduced to have the effective moment on a main rotor hub. The vibratory forces and moments acting on the main rotor hub were obtained using CAMARD II, then the acceleration of pilot seat position was calculated. The results showed the cant of a main rotor shaft could be an alternative way to supply a shortage of the required lateral CG offset however, the negative horizontal stabilator produces a large negative lift that eliminates the increase of fuselage lift force, which results in the slight increase of the 4/rev Fz force.
Grid-induced flow separation which often happens to computational fluid dynamics (CFD) for aircraft high-lift configurations is one of the problems in aircraft aerodynamic design using CFD. This is because the larger uncertainty on the aerodynamic forces due to the grid-dependent results causes the larger design margins on the aerodynamic characteristics, which may cause decreases in the aircraft performance in the certification by analysis. In this paper, grid-induced flow separation on the outboard wing of the NASA high-lift common research model (CRM-HL) is investigated. Steady-state Reynolds averaged Navier-Stokes analysis is conducted on six types of grids at angles of attack 7.05 and 17.05 degrees. The results are analyzed using a grid resolution index which is introduced to evaluate the grid resolution quantitatively. As a result, it is clarified that the grid resolution to capture vortices generated by slat brackets has a relation to the outboard wing flow separation. The results also show that grid refinement using the proposed requirement for the grid resolution index can improve the grid-induced flow separation.
This paper proposes the evaluation methodology in early design phase for the feasibility of novel instrument layout to be applied for the next generation civil aircraft, based on the MIL-HDBK-46855A human engineering guideline that shows pilot evaluation and analysis method for military system. Airline pilots evaluation on mockup with this method facilitates to identify the critical design issue and its potential resolutions from visibility, its trajectory and crew coordination point of view and mitigate the risk for late finding of issue to avoid redesign in later design phase. The effectiveness of the evaluation method is potentially shown by the trial usage on the conventional instrument layout, and the achieved data can be used for a reference to compare it with the novel instrument layout design.