Controlling of a space robot without actuators on the main body is an underactuated control problem. As stabilization methods, time-varying feedback controllers, discontinuous feedback controllers, center manifold based methods, zero-dynamics methods, and sliding mode controllers have been proposed. However, these methods sometime suffer from slow rate of convergence. In addition, modeling errors and delay time have not been sufficiently considered in the past studies. In order to obtain faster convergence time and compensate modeling errors and delay time, the adaptive invariant manifold based switching control method is proposed. Firstly the link angles are controlled to reach the invariant manifold by constant periodic motion and the modeling error is estimated by a discrete adaptive method. In the first stage, the delay time is also detected by measuring the difference between the predicted response and the actual one. Secondly the angular velocity rate of the two links is controlled to constant so that the state slides on the invariant manifold and reaches the goal state. In order to evaluate performance of the proposed control method, numerical simulations are conducted for not only the case with modeling error, but also with delay time.
We have been developing a catalytic recombination model of oxygen and nitrogen atoms on a silica surface based on the multiscale analysis from the ab initio calculation. In this paper, we focus on desorption and surface migration of oxygen atoms on the α-quartz (0001) reconstructed surface as the first stage of the multiscale analysis. Our calculation by the density functional theory shows the adsorption energy is 2.19eV and the energy barrier of surface migration of an adsorbed atom is 1.46eV. Transition rates of desorption and surface migration were calculated by the transition state theory and compared with literatures.
Measurements of velocity distributions immediately behind the trailing edge of NACA0012 airfoil at low Reynolds numbers were carried out to disclose the relation between the aerodynamic characteristics described in the previous report and the flow fields around the airfoil. A dead-air region due to laminar separation, which spoils the linear growth of lift, is created near the trailing edge of the airfoil at low angles of attack. A laminar separation bubble is observed in the boundary layer on the upper surface at intermediate angles of attack and the existence of the bubble might be responsible for the constant slope of the lift curve. Blunt decrease in lift peculiar to the stall of airfoils at low Reynolds numbers is characterized by the gradual expansion of turbulent separated region.
The coupled rotation-vibration-dissociation analysis of carbon monoxide is conducted by the state-resolved direct simulation Monte-Carlo (DSMC) model incorporated with a quasi-classical trajectory (QCT) model for computation of inter-molecular collision dynamics. The potential energy surface for the triatomic system is described by the London-Eyring-Polanyi-Sato (LEPS) potential, which is determined from the spectroscopic constants of diatomic molecules and the results of ab initio electronic structure calculations. A comparison is made between the numerical results and the experimental data in terms of the macroscopic relaxation parameters and the dissociation rate coefficients at moderate temperatures. Finally, the relaxation parameters and the dissociation rate coefficients at extremely high temperatures where the experimental data are unavailable have been estimated by the DSMC-QCT calculations.
The paper reports the vibration characteristics assessment of grid panels which were furnished in the main structure of 50kg-class micro-satellite ``SOHLA-1''. Three different types of grid panels with dimensions of 141.1 × 423.0 × 10.0mm, triangle-grid-type panel, rectangle-grid-type panel and frame-type panel, were investigated to find their dynamics through impulse test. Vibration characteristics were also simulated by a FEM computer soft NASTRAN. Application of flame-retardant type magnesium alloy to the panel was made to confirm the structural effectiveness of magnesium alloy panel.