This report presents a time-dependent mathematical model and numerical analysis of a hybrid (hydrostatic/hydrodynamic) thrust pad bearing as an over-clamped slipper with a restrictor of the low fluid film stiffness used in swash-plate type axial piston pumps and motors. The bearing's motion is simulated three-dimensionally, including roughness interaction, asperity contact and the time-lag between the changes in supply pressures and loads. Solutions are obtained regarding the friction, flow rate and contact pressure under mixed and fluid film lubrication conditions. Calculations indicate that the over-clamped slipper runs in fluid film lubrication in the low pressure period, but in mixed lubrication in the high pressure period. The time-lag affects markedly the motion and tribological characteristics of the slipper especially at the transition of the high and low pressure periods.

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The air spring for railway vehicle is usually passively controlled using a leveling (height control) valve with a sub tank to suppress the vibration of vertical direction. There are demands to reduce the space and to improve the controllability of the air spring for rail trains. In this research, the vibration of an air spring for railway vehicle is actively controlled by a pneumatic servo system. We proposed an active control method using an acceleration sensor, a relative displacement sensor, a laminar type flow sensor having high dynamic characteristics and a spool type servo valve. The flow sensor was used for linearization of the spool type servo valve. We applied the proposed method to a real air spring for railway vehicle having a mass of 800[kg]. The experiments were carried out for several frequencies especially at near the resonance frequencies and for several amplitudes of sinusoidal vibration given by a hydraulic driven vibration exciter. The results were compared with that of the passive control. The effectiveness of the proposed method was confirmed experimentally.

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Recently, the use of robots has been increasing into various fields, and is not only for industrial use. The expectations of using robots for support operations in disaster areas are increasing, to avoid the danger of secondary disasters that might occur. We are developing a hydraulically actuated hexapod robot COMET-IV, which aims to support a variety of activities in dangerous environments where humans caimot go. Currently, it is very difficult to implement fully autonomous robots in stricken areas. For this reason, teleoperational control of robots is an indispensable technology to be introduced. We believe that the performance of the teleoperation could be improved if it were possible for the operator to observe the robot conditions and surroundings in real time on a computer screen. We have proposed a teleoperation system that applies an omni-directional vision sensor and real time 3D animation of robots. Obstacle avoidance walking experiments conducted in an outdoor environment have indicated the effectiveness of the proposed system.

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Pneumatic isolation tables are widely used in high-precision processes and measurements to attenuate the vibration transmitted from the floor to the table, but also the vibration generated by the movement of the precision machine. In this paper, a new method for suppressing the second kind of vibration is proposed though feedback control of the differentiated pressure. The purpose of the feedback is to decrease the pressure time constant. Since the pressure change in the air-spring is very small, it is difficult to obtain the differentiated pressure by discrete simultaneous differentiation of pressure. Instead, this value is obtained through direct measurements by a pressure differentiator. Finally, the effectiveness of the proposed method is demonstrated experimentally.

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This paper presents an integral sliding mode controller with the describing function method for active suspension systems. The proposed controller can occur a desirable limit cycle in the vicinity of switching surface, since the controller despairs perfect sliding modes. As a result, deterioration of the control effect due to the chattering in the high frequency range, such as increase in acceleration of the sprung mass related to the ride comfort, can be suppressed. The nonlinear switching control input in the proposed controller is based on the twisting algorithm. A necessity condition and a setting procedure for the parameters of the controller are presented. A consideration of the robustness for the proposed method is demonstrated. Finally, simulation results show the effectiveness of the proposed controller.

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This report deals with a vibration control method of rotary cranes with rotating and boom-hoisting. In the control of the rotary crane, it is important to consider the trade-off between the settle time and the vibration of the load. In this report, we discuss the design problem of 2 degree of freedom control system which is robust for the change of the rope length. Although dynamics of the rotary crane are described by a double-input quadruple-output nonlinear system, the derived linear dynamics are two single-input double-output systems. And we find out the effectiveness of the proposal method by the experiment.

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This study aims at achieving a three axis stabilization attitude control of a satellite using two control moment gyros (CMGs). If this can be achieved, it leads to realization of attitude control system (ACS) with fault tolerance because the loss of the function of ACS is not fatal even if some CMGs mounted on the satellite are broken. In this paper, an underactuated satellite with two CMGs is a controlled system, and both conservation law of angular momentum of satellite and satellite attitude dynamics were formulated. Using the Rodriguez parameter as an attitude representation, satellite attitude kinematics was formulated. In this study, a sliding mode controller using the Rodriguez parameter was designed. To verify the control performance of the designed controller, some numerical simulations were carried out. From some results, we confirmed the effectiveness of the designed controller for controlling the satellite with two CMGs.

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In this paper, a new saturation control technique using fractional calculus in the framework of anti-windup compensation is developed for linear time-invariant systems subject to input nonlinearities. The difficulties of most anti-windup control methods are caused by constracting a local feedback loop which connects the anti-windup compensator to an unconstrained controller. Instead, it is considered that a fractional order controller is simply put in front of the unconstrained controller. The effectiveness of the proposed method is examined in a numerical example.

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In this paper, we consider the nonlinear control of four wheel steering/driving vehicle with nonlinear dynamics, and proposed integrated control of steering and breaking/driving force by state-dependent riccati equation (SDRE) method. In this control method, the saturation property of longitudinal and lateral force which generated from front and rea tire is considered. The effectiveness of proposed control method is verified by numerical simulations.

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Precise motion control of underwater vehicles without mechanical noises is a technical issue on underwater observation. As a solution for the problem, we pay attentions to bio-mechanisms of underwater creatures, especially ribbon-like fins being used for attitude control. Bio-mechanisms of creatures are adapted to environment as a result of evolution. If the motor control mechanisms of the creatures can be introduced into underwater robots, there is a possibility that a high performance actuator will be realized. In this research, we have been trying to develop a biomimetic underwater actuator instead of screw propellers. As the material of a developing actuator, electroconductive polymer is used as an artificial muscle. We introduce the developing biomimetic actuator and the performance evaluation test of motion control experiments is discussed.

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Abstract: An ocean-going underwater glider with independently controllable main wings is under development for applications in oceanographic surveying, monitoring of the marine environment, and ocean exploration. Power-driven propulsive machinery is unnecessary for this underwater glider so that it is applicable to long-term and wide-range operations. And this silent and safe underwater vehicle can be maintained with relative ease and does not cause any harm to the ocean environment and underwater marine life. The purpose of this research is to establish a method to control an experimental vehicle named 'ALEX' as a test-bed for an underwater glider with independently controllable main wings. ALEX was designed to realise high performance manoeuvrability. The six servomotors for the right and left main wings, upper rudder, elevator, movable balance weight and combination valve can be controlled by the on-board microcomputer system MAVC2 (Micro Aerial Vehicle Controller 2^<nd> model) through a servomotor controller. Three axes acceleration, three axes angular velocity, depth and direction by magnetic compass during a cruise can be measured in 10 samples per second and stored in the EEPROM (Electrically Erasable Programmable ROM) as the flight recorder for a maximum of 20 minutes. The ALEX glider is navigated by dead reckoning under water but accurate positioning can be obtained by GPS when it is at the surface. These sensor data are transmitted to a PC station by a wireless modem system when positioned at the surface. Various kinds of experiments and motion observation have illustrated that an underwater glider with independently controllable main wings exhibits a high performance of motion and has remarkable capabilities for diving / surfacing with a much smaller gliding angle as compared with a conventional fixed-wing underwater glider.

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In the previous report, the concentrated mass model was proposed to analyze a nonlinear pressure wave phenomenon in a cylindrical straight tube. In this paper, we apply the model to an enlargement and contraction element. To confirm the validity of the proposed model, we perform experiments on a sound tube with a muffler, compare the experimental results with the numerical results. The numerical computational results agree very well with the experimental results. Therefore, it is concluded that the proposed model is valid for the numerical analysis of nonlinear pressure wave problem in a tube with enlargement and contraction.

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The averaging method of elliptic type is proposed in order to obtain accurate periodic solutions for a nonlinear oscillator with multi-degree-of-freedom with harmonic excitation and damping. Sum of Elliptic Jacobian cosine and sine function is incorporated as the generating solution of averaging method. The stability analysis for the approximate solution obtained by the present method is also discussed. The numerical results for typical nonlinear oscillators with two and three -degree-of freedom systems are shown. The efficiency of the proposed method is illustrated by comparing its computational results with those obtained by the shooting method. It is confirmed that the present method is effective to analyze nonlinear oscillator with Multi-degree-of Freedom System

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Squeal and chatter phenomena were generated in bicycle disc brake. In this report, the authors deal analytically with a simple coupled in-plane and out-of-plane vibration system with three degree of freedom subject to the friction in order to make clear the essence of such phenomena generated in bicycle disc brake system. In this model, two kinds of squeal were generated in the nonlinear analysis, the squeal generated in the linear analysis and the internal resonance phenomena were also generated in the nonlinear analysis. The squeal was in-plane unstable vibration in the disc surface direction, caused by the dry friction with negative slope with respect to the relative velocity. The internal resonance phenomena, that is, the chatter was the other frictional nonlinear vibration in which the squeal and the out-of-plane unstable vibration due to Coulomb friction were combine together through the internal resonance relationship between out-of-plane and in-plane vibrations caused by increasing of moment spring constant.

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Estimation of time-varying vibration parameters, that is, instantaneous damping and frequencies by the wavelet transform is based on the ridge identification and the phase extraction in the time-frequency map. However, the process of the ridge identification is rather complicated, and the most suitable mother wavelet to yield a time-frequency map for an efficient identification can not be determinately chosen. In this paper, the time-varying parameters pertaining to nonlinearities are successfully estimated by a segmental use of the harmonic wavelet. In addition, it is possible to identify nonlinear vibration parameters qualitatively and quantitatively by the time-varying parameters, using method of averaging which is a type of approximate method for the weakly nonlinear system.

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This paper deals with the problem of vibration quenching of the system with a limited power supply using a Hula-Hoop. Following was made clear from the results of numerical analysis and experiment: (1) It is confirmed that the self-excited vibration such as the one observed in automatic balancer is not capable of generating. (2) This device is very effective in the region exceeding the resonant point of the system. (3) Both vibration quenching and energy saving are able to be established by using the bearing with small rotating resistance for Hula-Hoop. (4) The experimental and the analytical results were in good qualitative agreement with each other.

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Friction-induced vibration in a mechanical system sometimes generates a bouncing motion of an object. When a plate-like object is rubbed by rubber, such a self-excited vibration is generated. This vibration often results in noise since plate vibration oscillates the air. For reducing the vibration, we perform numerical simulations assuming that the rubber does not slip and bounces on a plate, and examine the effect of the mass and the damping of a dynamic absorber mounted on a plate. The calculated results are compared with the experimental ones. The results demonstrate that the damping of a dynamic absorber is effective for reducing the vibration.

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The self-synchronized phenomena generated in a coupled self-excited oscillators acting on Coulomb's friction are analytically investigated. This system consists of two nonlinear self-excited oscillators coupled in series. In this system, the stick-slip vibration often occurs resulting from the friction. The shooting method is improved in order to analyze the discontinuous systems. As results, there are unstable regions based on saddle-node or period-doubling bifurcation alternately exist on the branch of Model, which the blocks vibrate nearly in-phase. In this relation, we analytically show that such unstable regions are caused by internal resonance by dealing with variational equation of the model which the same oscillators are coupled.

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Generally, we have a problem that the control inputs to stabilize pendulums and to swing up a pendulum interfere, when we swing up pendulums one by one in a multiple inverted pendulum system. To solve this problem, we proposed the subspace control for stabilizing the system and the method to swing up a pendulum by nonlinear resonance based on Jacobian elliptic function. In this report, we apply these methods to a parallel triple inverted pendulum system and verify the effectiveness of the methods by numerical simulation and experiments.

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This paper considers a spatially periodic structure consisting of identical rigid members which are connected to adjoining ones under the action of nonlinear restoring moments. The members extend straight in equilibrium and the displacements are restricted in a plane. The numerical solutions to the governing equations with free boundary conditions at both ends and the appropriate initial conditions show that movable intrinsic localized modes (ILMs) can be excited and that they exhibit a variety of interesting interactions between them.

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