In recent years, the aerodynamic analysis using computational fluid dynamics (CFD) has been widely used in the actual aircraft design. Especially, unstructured mesh method is widely used now, because it can treat complex objects. However, there are several difficulties in the current CFD, for example difficulty in the large scale parallel computation, in the mesh generation applying to the much complex objects, in the deformation of the volume mesh, and so on. To overcome these issues, the Building-Cube Method (BCM) based on the equi-spaced Cartesian mesh has been proposed. As is widely recognized, the biggest issue to use Cartesian mesh approach is the treatment of wall boundaries. In this study, Immersed Boundary Method (IBM) with ghost cell/image point approach is implemented. Virtual flux concept is also implemented to compute thin components like trailing edge of a wing. The Cartesian mesh solver has advantages in treating the moving boundary problems, because of the easy mesh generations. Therefore, the nonlinear flutter simulations are also carried out by direct coupling of the compressible Building-Cube Method and the structural equations.
Proper Orthogonal Decomposition (POD) or Dynamic Mode Decomposition (DMD) is a useful analysis method to extract principal components from complex flow and to understand the flow field. In POD, it is possible to extract the components of the flow which occupy a lot of energies. In DMD, it is possible to take in dynamic information by dealing with sequence of the given time series data and to observe the component of the flow which has specific frequency. In this study, flow around circular cylinders arranged independently, in series or in parallel is measured by time resolved PIV, and POD or DMD is applied to the data. In any case of model arrangement, it is confirmed that vortex shedding is expressed by pair of POD modes or DMD modes which have vortex shedding frequency or its harmonics.
Gain-scheduled steering control for the adaptive skew pyramid-type control moment gyros (ASCMGs) is proposed. Contrary to past studies that treated the fixed skew angle for pyramid type CMG systems, in the adaptive skew pyramid type CMG system (ASCMGs), the skew angle is treated as a variable to obtain larger torques, compared to the traditional fixed skew angle CMGs. The steering control law proposed for the ASCMGs handles not only gimbal angles but also the skew angle, and consists of off-diagonal singularity robust inverse term and null motion term. The numerical results show that the skew angle has a tendency to change towards the ordinary skew angle in order to maintain the singularity free space as large as possible at the end of maneuver, settling time of the maneuver was shortened, compared to the case of the fixed-skew angle SGCMGs, and that by introducing a weighting function to the element associated with the skew angle in the off-diagonal matrix, the skew angle rate is smoothly controlled to avoid chattering-like motion near singularities and at the end of or after maneuver.
New type of strain sensor using a CMOS inverter oscillator circuit has been developed. The sensor could omit an amplifier because a counting device measures frequency changes of circuit voltage output caused by resistance changes of a strain gauge. Characteristics and measurement accuracy of the sensor that consists of an oscillator circuit and a strain gauge were confirmed by static tensile tests of specimens. The test results showed that the same level of accuracy as conventional sensor has been achieved by using simple compensation factor assuming of existence of internal resistance on circuit.
In a heater control system including a number of elements, the power consumption may exceed the capacity of the power supply when a lot of elements require the power source simultaneously. In such case, the system has some risk of power shortages, while the time-averaged power consumption is enough low for the power supply. If an equipment gathers the information about the temperature of each elements and controls each switches not to turned on simultaneously, the over consumption would be prevented. However, this system needs many cables between center equipment and each elements, and becomes complex and lacks versatility. To solve these problems, authors has proposed a novel multi-agent heater controller that maintains the temperature at each element, while the whole power consumed is kept constant, without any specific server in the system. In this paper, a new developed multi-agent heater controller for spacecraft is introduced and results of experiments to verify the control system are shown. The results are compared with the results of simulations.