Pneumatic vibration isolation tables are used in the field of semiconductor manufacturing and precision measurement. The flow disturbance to the isolation table causes the fluctuation of the table. In order to control the flow disturbance, multi-connection air regulators are often used. However, the multi-connection air regulators lead to a pressure loss of the compressed air. Previously, we used two feedforward control methods which utilized a pressure sensor to measure the supplied air pressure and provide feedforward controlled signals to the actuators. One method used an air spring and the other used a voice coil motor (VCM) as the actuators. The current study proposes flow meter instead of pressure sensor for the feedforward control of the flow disturbance. Until now, a flow meter has been used for monitoring the supplied air flow to the pneumatic isolation table. The objective of this study is to utilize a flow meter in practical control of the flow disturbance. In addition to the control of flow disturbance, the proposed method is also used to control the disturbances caused by the reduced supplied flow and air flow drops.

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In this paper, nonlinear and bilinear dynamic models are derived that include the dominant dynamics of the air pressure and flow in a fuel cell system. A two-degree-of-freedom sliding mode control system is also designed using a linear time-invariant state-space model derived from the nonlinear model. A precompensator is also designed that takes into account exhaust gas flow passing through the throttle valve. The precompensator shapes the pressure and flow references and makes the exhaust gas flow passing through the throttle during transient response approximate the desired flow. The precompensator also makes the references approximate static references for appropriately operating the fuel cell system in a static state. This paper presents the architecture of the precompensator, which takes into account the tracking performance for the static references and flow passing through the throttle in a transient state. Numerical calculations and experimental results are presented to verify that the nonlinear model accurately simulates the transient responses of the actual system and that the proposed techniques improve the transient pressure and flow responses in the fuel cell system.

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Interconnection and damping assignment passivity-based control (IDA-PBC) is a nonlinear control method which stabilize a system shaping its total energy and utilizing passivity. In previous studies, IDA-PBC is shown to be a powerful method to stabilize underactuated mechanical systems. However, the transient performances tend to be slow. In this study, to improve the slow responses and realize fast transient ones, the IDA-PBC is applied for a cart-inverted pendulum and free parameters in a closed-loop inertia matrix which have not been used in the previous studies are utilized. This means modifying the kinetic energy more actively. On the other hand, the additional use of the free parameters makes the selection of them more complicated because several assumptions must be satisfied to derive an IDA-PBC controller. To deal with this problem, we also propose a systematic method to select them graphically from a simple two dimensional region. Finally, we show that the transient performances of the IDA-PBC can be as fast as the LQR with the active modification of the kinetic energy. The IDA-PBC with suitable parameters also theoretically estimates as large domain of attraction as the upper half plane preserving the fast transient performances.

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This study aimed at simultaneously achieving realization of ride comfort and steering stability through controller design for semi-active suspension taking into consideration the most sensitive frequency range of the human body and vehicle behavior when steering. A method that can improve both ride comfort and vehicle stability is proposed by separating the control range in terms of the frequency domain, where the frequency weighting in controlled variables is used. Furthermore, the controller is scheduled in the time domain to attain a positive pitch angle during slaloms. The dynamics of road disturbance is assumed and is accommodated into the controller to make control more effective. Computer simulations were carried out to investigate the effectiveness of the proposed control system by using a full-vehicle model that had a variable stiffness and damping semi-active suspension system. As a result, it was demonstrated that the proposed method can improve ride comfort, reduce vehicle motion, and synchronize the roll and pitch motions caused by steering.

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Reducing the weight of industrial rotational machinery equipped with Active Magnetic Bearings (AMBs) has been shown to achieve efficient hydraulic performance at high speed rotation. It also improves space efficiency and gives cost reductions. One of our solutions for increasing rotational speed is to experimentally demonstrate the passing of the 3rd bending critical speed. In this paper, a flexible rotor supported by AMBs is introduced. The controller design for mode separation control is studied and the stability margin is evaluated according to ISO 14839-3. After checking the stability, we successfully perform the rotation test to pass a total of 5 critical speeds, i.e., 2 rigid modes and 3 bending modes, by using a modal balancing technique. This paper proves that stability and balancing are key technologies for achieving high-speed rotation.

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The development of magnetic suspension (MS) technology has been widely applied in high-tech industry. MS actuator has features of contact-free, friction-free, low contamination and low noise. This paper describes the design and examination of the hybrid MS actuator referring to our previous works with different analysis aspect to improve the overall performance of actuator and system. The re-designed MS actuator is analyzed and controlled by deriving its magnetic force and system state equations. This paper uses commercial products for design process and simulations about the stability and robustness of system. After deriving the dynamic equation of ball and beam system, the sliding mode control (SMC) is applied in the balance and stabilize the ball and beam system. The drive circuit and MS actuators are controlled by the microcontroller in ball and beam system. The combined SMC and Fuzzy Logic Control (FLC) are also introduced to control the adjustable stable position. Different situations are tested separately with conformed results to desired responses. Finally, comparison and analyses of the results in laboratory have presented good improvements on the proposed system.

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By using the feedback linearization, we studied the generating mechanism of intermittency. The well-known Lorenz model, Rössler model and BZ reaction model were selected as the subject of the present study. At first, we studied the basic properties of these models and it was found that the feedback linearization can apply to the analysis of these models. Subsequently, these models were modified into the linear equations with nonlinear inputs by the feedback linearization and we considered the generating mechanism of intermittency. The consideration results showed that the detailed information of the boundary has an important meaning to study the generating mechanism of intermittency. Moreover, it was shown that the generating mechanism of intermittency can be explained intuitively by the collision with the boundary.

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The resonant frequency of flexural vibration for an atomic force microscope (AFM) cantilever has been investigated using the Timoshenko beam theory. In this paper the dynamic behavior of vibrational modes based on Timoshenko beam theory by consideration the effects of contact position, the height of the tip, thickness of the beam, and the angle between the cantilever and the sample surface on the non-dimensional resonant frequency have been investigated for the rectangular AFM cantilevers. The results show that the frequency is sensitive to the contact position and also decreases by increasing Timoshenko beam parameter or cantilever thickness, the first frequency is sensitive only to the lower normal contact stiffness, but high order modes are sensitive in a larger range of normal contact stiffness. By increasing the height H, for a limited range of normal contact stiffness the sensitivity to the normal contact stiffness increases. Increasing the lateral contact stiffness increases the sensitivity to the normal contact stiffness after critical normal contact stiffness, but when the normal contact stiffness is lower than critical normal contact stiffness, the situation is reversed. Furthermore, by increasing the angle between the cantilever and sample surface, the frequency decreases.

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Automatic inference of depth/distance information is a primary goal of computer vision systems. Although the stereovision method is often used for computer vision, finding matching pairs between frames can often be problematic, particularly when there are several possible matching points. In order to cope with these problems, we have developed a depth measurement system that uses a single CCD camera. By placing the optical device in front of the camera lens, the image of a target recorded on the image plane is displaced by an amount related to the distance between the camera and the target. When the optical device is rotated physically at high speed during the exposure of the camera, the image of a moving target traces a spiral streak. Since the size of the streak is inversely proportional to the depth, and since the pitch and the variation in the size of the spiral is related to the velocity of the moving target, the 3-D information of the target can be obtained by analyzing the streak. In order to make image processing easier, the spiral streaks and their corresponding centerline are recorded on the same image. The centerline is used in computer processing to analyze the streaks. The developed method has been applied to the measurement of moving tracer particles in a flow, and satisfactory results were obtained.

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Wave motion of a liquid in a rotating, axially symmetric container undergoing a whirl motion is investigated. In the analysis of the present study, gravity is considered to be negligible and the liquid motion is taken as being axially uniform. Assuming that the liquid layer is thin, based on the shallow-water theory, the equations of motion are simplified to a one-dimensional problem along the circumference of the container. The modal coupling equations that include the nonlinear effects of the wave motion are obtained by applying Galerkin's method. Periodical solutions under harmonic whirl motion, which give resonance curves, are determined by applying the harmonic balance method to the modal coupling equations. The wave height and the fluid force acting on the container obtained from the analysis are compared with experimental results reported in previous studies. Good agreement is observed between the results of the present analysis and the experimental results with respect to the wave height profile and the magnitude of the fluid force by which the asynchronous whirl motion of the container is excited.

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