A novel control law based on the sliding-mode control is proposed for energy-recycling vibration suppression of a structure with piezoelectric transducers. The performance of vibration suppression with the proposed control law is investigated and compared with that of the previously proposed control law based on LQR control theory. Numerical simulations of vibration suppression with a 10-bay truss structure show that the proposed control law is effective in suppressing vibration. Through experiments of vibration suppression with a truss structure, the proposed control law is shown to suppress single-mode and multiple-mode vibrations of actual structure. Although the proposed control law is derived in a different way from the previous control law, the two methods are found to have similar coefficients of modal velocities in the control index.
Performance of the methane fueled rocket nozzles are numerically investigated using computational fluid dynamics approach. A simple set of chemical reactions and kinetics for methane/oxygen nozzle flow is proposed. The chamber pressure, mixture ratio and size of the nozzle are parametrically changed to study the influence of characteristic rocket engine design parameters on nozzle losses. The amount of dissociation is high when the chamber pressure is low and the kinetic loss becomes dominant compared to the other nozzle losses. The peak specific impulse is achieved at a higher mixture ratio region as the chamber pressure increases. The chemical non-equilibrium flow appears mainly at down stream region of the nozzle throat. The influence of the chemical non-equilibrium effect decreases as the chamber pressure increases. Supersonic chemically reactive gas stays longer in the nozzle as the size of the nozzle become larger and the amount of recombination increases which decreases the kinetic loss. When the chamber pressure is high, the kinetic loss becomes small and the effect of the size of nozzle also becomes small.
This paper presents a new guidance and control system for a re-entry vehicle. In the conventional drag acceleration control system employed for the present space shuttles, the velocity is an unobservable state variable and the associated pole tends to be unstable. Therefore, in this study, a condition which allows all the states to be observable is introduced using a state-space linearization method. It is also shown that energy and its rate are appropriate for the state variables. A guidance law is analytically derived on the basis of the obtained state equation with respect to the energy by solving a two-point boundary-value problem. Furthermore, a tracking control system is designed to make the position, velocity, and flight path angle of the vehicle track the reference states generated in the guidance system. Finally, numerical simulation is performed to verify the validity of the obtained plant expression, and the effectiveness of the proposed guidance and control system.
In this paper, the new equation for estimating the missile flight distance during boost phase is presented and applied to the guidance law for the missile. First, the equation is obtained assuming the zero-lift drag coefficient is constant. The simulation results show that the equation gives the far better estimation than the previous one. Second, applying the equation to computing the future intercept point with a target, we obtain the collision course. Then, the new guidance law that makes the missile fly on the course is developed. Finally, we performed some simulations and verified that the guidance law presented is easy to design and has good performance if the initial heading angle error is small.
During the 20th century, aircraft were only used for transportation. If aircraft can be made small and lightweight, however, they can become tools to assist in everyday life. We developed a small, lightweight co-axial helicopter with a rotor diameter of about 30cm. The mechanisms for varying cyclic pitch of the upper and lower rotors, which are used in the coaxial helicopter for entertainment, are adopted in our develop helicopter. Our developed helicopter is equipped with a flight control system for the attitude and position, which is composed of a micro computer and some sensors. And the helicopter can make autonomous hovering flight just measuring the height and the distances from the walls. The weight of the helicopter is no more than 200g and this helicopter is the lightest helicopter for an autonomous hovering flight among the helicopters where all control systems are onboard, as far as the authors know.
Laser absorption spectroscopy was applied to pure oxygen flows generated by an inductively heated plasma generator IPG3. Temporal variation of translational temperature was deduced from measured absorption line broadening of OI 777.19nm because the flow properties fluctuated at 300Hz in synchronization with the induction current. The specific total enthalpy and mole fraction of oxygen were estimated from the deduced temperature assuming thermo-chemical equilibrium. Consequently, the averaged degree of dissociation of oxygen is 92%. The specific total enthalpy on the centerline was estimated at 33.7±2.9MJ/kg; 43% of it was in the form of chemical potential. Results show good agreement with intrusive measurements.
Because a new function of rolling moment control was added to the JAXA 60cm MSBS, control capability of the 6 components of magnetic force was examined. Adding pair magnets on both ends of a main magnet in a 5 DOF control model provides the model with rolling moment, which can be controlled by changing 4 side coil currents adequately. The magnitude of the moment was evaluated well with a proposed analytical expression. The effect of roll angle on the magnetic force except the rolling moment was estimated less than 0.5%FS in the tested range. The effect of rolling moment control current on the force was not changed with the roll angle. The reference balance was recalibrated to meet the calibration range to that of 5-axis calibration test of the JAXA 60cm MSBS. New error evaluation of Fx,Fy, and Fz gives 1.2%FS, 0.8%FS, and 1.2%FS, respectively.