by and for Young Researchers
Kyoto University
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Asian Advanced Vibration and Control Forum by and for Young Researchers |
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| October 22 - 24, 2007 | ||
| Room 211, Faculty of Engineering Department of Physics Building, Kyoto University |
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| Time | Schedule | Remarks | |
|---|---|---|---|
| 09:00〜12:00 | Special seminar | Free-for-all | |
| 12:00〜13:00 | Lunch | ||
| 13:00〜18:00 | Discussion | Free-for-all | |
| 18:00〜20:00 | Dinner | ||
Chong-Won Lee (Professor, NOVIC, Department of Mechanical Engineering, KAIST, Daejeon, Korea)
In this work, we introduce two new biologically inspired mechanisms from flying insect flapping and fish locomotion, which utilize resonant vibration.
The flapping motion of flying insect is modeled as the second mode vibration of a ring with a pair of wings attached to the vicinity of two neighboring nodal points, so that the angular motion of the wings can be maximized. When the vibrating flapping mechanism, with its wing span angle of slightly less than 90 degrees, is subject to rotation, the torque produced due to the difference in flapping angles of two wings caused by the moving effect of nodal points of rotating ring acts in the opposite direction of rotation, so that this mechanism has the capability of self-attitude control. When the wing span angle is larger than 90 degrees, the flapping mechanism gets unstable, generating a torque acted in the same direction of rotation and thus resulting in a rotating motion.
Inspired by the observation that the highly efficient, smooth, steady-state fish locomotion may result from the harmonic motion excited at one of its natural frequencies, we attempt to understand the mechanism of fish locomotion through the resonant vibration analysis of a continuous free-free beam with varying cross-sectional area, which is submerged in water. A linear finite element model of whiting (codfish) is constructed and its steady-state harmonic response is calculated, considering the nonlinear dynamic hydraulic resistance. It is found, from extensive numerical analysis with the fish model, that the wavy paddling motion, and thus the fish forward motion, can be effectively generated by the resonant vibration at its second natural frequency, when the neighboring modes also significantly contribute to the steady-state harmonic motion. The positive net thrust, which is mainly due to the interaction between the paddling motion and the resulting hydraulic resistance, monotonically increases, as the amplitude of fish motion increases.
Hiroaki Nakanishi (Lecturer, Department of Mechanical Engineering and Science, Kyoto University, Kyoto, Japan)
Various kinds of Unmanned Aerial Vehicles (UAVs) are developed and used for many purposes. Japan is on the top in production of unmanned helicopters, a type of UAV, for non-military uses, and more than 2,000 unmanned helicopters are used for agricultural purposes, especially for aerial chemical spraying at rice paddy fields. But an operator must control the unmanned helicopter manually, and the helicopter can not fly out of the operator’s sight. Therefore, the usage of the unmanned helicopter is limited.
To reduce the loss of a disaster, the information about the disaster area is needed. Therefore it is necessary to develop methods for gathering information about disaster area. Aerial rescue robot is effective for the disaster response because it can easily approach to the disaster area and gather bird's-eye information. Especially, Aerial rescue robot can be used at dangerous area, such as erupting volcano, without putting pilots and observers at risk. To apply an unmanned helicopter for this purpose, autonomous flight control system must be developed. In the presentation, our studies on an autonomous helicopter for disaster prevention and disaster response, especially, prime research results of DDT Project (Special Project for Earthquake Disaster Mitigation in Urban Areas/III-4 Development of Advanced Robots and Information Systems for Disaster Response are reported.
Youngjin Park (Professor, NOVIC, Department of Mechanical Engineering, KAIST, Daejeon, Korea)
We introduce the preview control to vehicle systems which include high speed tracked and wheeled vehicles, the stabilization control to a satellite antenna and a pointing apparatus mounted on the unmanned ground vehicle and the iterative feed-forward control to a 6-dof shaking table.
Military vehicles such as a tank have an important role in the battle on the ground, so that study on performance enhancement has been progressed widely in the world. In close future, average traveling speed of military vehicles will be increased up to 60km/h. Because it mainly drives open field with irregular road surface, such a high speed traveling can result in severe vibration of chassis. Such a vibration can deteriorate ride comfort of drivers. In order to reduce the vibration efficiently, preview control based on an active suspension unit is applied. Preview control uses the front road information acquired from preview sensors in designing controller and result in performance improvement of ride comfort.
The research results for improving the tracking performance of a servo-hydraulic shaking table are presented. A servo-hydraulic shaking table is not only highly nonlinear but has a lot of time delay. In addition, the shaking table, which consists of multi axial hydraulic actuators, is a MIMO system coupled by kinematics and dynamics of each other’s actuators. It is necessary for the shaking table to track arbitrary trajectories up to high frequency even at the extreme situations such as substantial external loads and large disturbances. For this purpose, an iterative feed-forward control based on the inverse of a measured frequency response function is used for the shaking table control. To solve the dynamic coupling, a pressure feedback control is introduced. It is shown through numerical simulations and experiments that the tracking performance of shaking table can be improved up to 100Hz.
Kwang-joon Kim (Professor, NOVIC, Department of Mechanical Engineering, KAIST, Daejeon, Korea)
and Jeung-hoon Lee (Research Associate, NOVIC, Department of Mechanical Engineering, KAIST, Daejeon, Korea)
Pneumatic vibration isolation tables with resonance frequencies at a few Hertz have been popular for precision measurement and process equipments whose resonance or excitation frequencies are higher than tens to hundreds of Hertz. Recent advances in high precision equipments, e.g., those with internal active stabilization system, require better vibration isolation in very low frequencies. The purpose of this study is to set up a simple but practical technique in transmissibility design for double chamber pneumatic vibration isolation table.
From experimental observations on complex stiffness of double chamber pneumatic springs and subsequent dynamic modeling, it was found that stiffness of diaphragm used for air sealing, size of two chambers, and shape of capillary tube between the two chambers are key parameters in design. Since the rubber diaphragm, which can be characterized by amplitude and frequency dependent complex stiffness, is rather independent of the other design parameters, main focus here is put into design optimization of the two chambers and the capillary tube. As an important result, a fundamental design principle, called optimum damping tuning in the study, is proposed. That is to locate the frequency of the maximum loss factor of the dual-chamber pneumatic spring at the system natural frequency.
Trade-off to be considered inherently in practical selection of the chamber volume ratios is also discussed. Actual transmissibility measurements on several different designs are illustrated to show the optimality of the new design concept.
Hideo UTSUNO (Associate Professor, Department of Mechanical Engineering and Science, Kyoto University, Kyoto, Japan)
In this seminar, flexural wave propagation along the long cable, sound propagation at the perforated panel, and pulse wave propagation in the blood vessel are discussed. The governing equation of these phenomena is one dimensional wave equation which is taught in the second year of a university or the third year. However, they are quite useful to solve the real problems of vibration and sound propagation. Soliton of flexural wave occurs when the long cable collides to each other. After propagation of long distance, it becomes continuous sinusoidal wave which changes from high frequency to low frequency. Sound energy dissipation is caused by the viscosity at normal sound pressure level. On the other hand, energy dissipation proportional to the velocity squared pressure loss can occur at high sound pressure condition. The perforated panel was designed as a sound absorbing material using this phenomenon at the holes, and it was utilized in a silencer of the compressor. Arteriosclerotic is one of the serious mortality causes of human. If the blood vessel becomes stiff, it means the velocity of propagation of the pulse quickens. A new method to identify the pulse propagation speed in blood vessel is described.
Mai Bando (Ph. D. Student, Department of Aeronautics and Astronautics, Kyoto University, Kyoto, Japan)
and Akira Ichikawa (Professor, Department of Aeronautics and Astronautics, Kyoto University, Kyoto, Japan)
Modeling and control of complex nonlinear dynamical systems is a difficult task, and a natural approach is to use multiple local models and controllers, which are simpler. It is referred to as a multiple model approach, and is used in many areas. If local models are linear and underlying systems are described by their convex combination, they form an important subclass which contains Takagi-Sugeno fuzzy systems. This subclass has theoretical and computational advantages that ample design methods of controllers from linear systems theory can be used and many efficient algorithms are already developed. In this paper adaptive output regulation for nonlinear systems described by multiple linear models with unknown parameters is considered. Based on the Lyapunov stability theory, locally stabilizing adaptive controllers are designed, and local adaptive output regulation is established using a state dependent regulator equation. Simulation results are given to illustrate the theory.
Sang-Hyun Park (Ph. D. Student, NOVIC, Department of Mechanical Engineering,
KAIST, Daejeon, Korea)
and Chong-Won Lee (Professor, NOVIC, Department of Mechanical Engineering, KAIST, Daejeon, Korea)
In this work, we introduce two new biologically inspired mechanisms from flying insect flapping and fish locomotion, which utilize resonant vibration.
The flapping motion of flying insect is modeled as the second mode vibration of a ring with a pair of wings attached to the vicinity of two neighboring nodal points, so that the angular motion of the wings can be maximized. When the vibrating flapping mechanism, with its wing span angle of slightly less than 90 degrees, is subject to rotation, the torque produced due to the difference in flapping angles of two wings caused by the moving effect of nodal points of rotating ring acts in the opposite direction of rotation, so that this mechanism has the capability of self-attitude control. When the wing span angle is larger than 90 degrees, the flapping mechanism gets unstable, generating a torque acted in the same direction of rotation and thus resulting in a rotating motion.
Inspired by the observation that the highly efficient, smooth, steady-state fish locomotion may result from the harmonic motion excited at one of its natural frequencies, we attempt to understand the mechanism of fish locomotion through the resonant vibration analysis of a continuous free-free beam with varying cross-sectional area, which is submerged in water. A linear finite element model of whiting (codfish) is constructed and its steady-state harmonic response is calculated, considering the nonlinear dynamic hydraulic resistance. It is found, from extensive numerical analysis with the fish model, that the wavy paddling motion, and thus the fish forward motion, can be effectively generated by the resonant vibration at its second natural frequency, when the neighboring modes also significantly contribute to the steady-state harmonic motion. The positive net thrust, which is mainly due to the interaction between the paddling motion and the resulting hydraulic resistance, monotonically increases, as the amplitude of fish motion increases.
Sayaka KANATA (Ph. D. Student, Department of Mechanical Engineering and Science, Kyoto University, Kyoto, Japan),
Hiroaki NAKANISHI, Tetsuo SAWARAGI (Department of Mechanical Engineering and Science, Kyoto University, Kyoto, Japan),
Tetsuo YOSHIMITSU and Ichiro NAKATANI (Institute of Space and Astronautical Science (ISAS/JAXA), Japan)
We propose a reasonable localization method of a rover on small planetary body. Conventional localization methods are not adequate on sub-hundred-meter-sized bodies because of the planet’s irregular shape and small mass. One of the conventional methods, localization by camera images obtained on the rover needs a map made by a mother spacecraft. The resolution of the map is not enough for the rover’s local view. Localization by observing the movements of stars and the sun has little accuracy, because it needs gravity direction for a reference direction. The direction of gravitational force measured on the surface of the small planetary bodies does not always pass through the center of the mass. The direction error causes crucial effect to the localization accuracy. Our method measures two way range between a rover and a mother spacecraft. It realizes real-time localization by using Kalman Filter processing. The localization accuracy is meter order, assuming ITOKAWA-size planet whose maximum diameter is 600[m]. As HAYABUSA mission has shown in 2005, the surface of the asteroid ITOKAWA is full of geographical features. One of the future missions on a small planetary bodies is the surface exploration by a rover. Our proposal would provide effective navigation for these rovers.
Min-Geun Song (Master D. Student, NOVIC, Department of Mechanical Engineering,
KAIST, Daejeon, Korea)
and Youngjin Park (Professor, NOVIC, KAIST, Daejeon, Korea)
Tilt sensor is necessarily required when a biped robot walks on an uneven terrain against the external disturbance. Gyro sensor widely used for tilt estimate. These sensors can be sampled at high rates so gyro sensor is suitable for sensing the rapid motions that create high frequency pose variations. But gyro sensor only measure motion rates. its signal must be integrated to produce position or orientation. Noise and bias in the sensor signal integration produces a drift in the attitude computation that accumulates with elapsed time. To correct the accumulated drift, it is necessary to periodically reset the integrator output with measurements from other sensors that provide correct reference information.
To overcome this problem, we can use the vision sensor for low frequency stability and attitude computation. However vision sensor suffers from a lack of robustness system delay and high computational expense.
In this study, we propose a flexible framework with a two-channel motion-filter structure using Extended Kalman Filter (EKF). The two processing channels, one for the low rate vision measure and another for the high-rate inertial gyro, are complementary in that each compensates for the weakness in the other. The two channels process data independently, allowing for different sample rates of the sensor systems and reducing the end-to-end system delay.
Daisuke KONO (Ph. D. Student, Department of Micro Engineering, Kyoto University, Kyoto, Japan),
Atsushi MATSUBARA, Iwao YAMAJI, and Tomoya FUJITA (Department of Micro Engineering, Kyoto University, Kyoto, Japan)
This study describes a compensation method of the motion errors of machine tools to achieve sub-micron-order machining accuracy. The final goals are to measure, model, and compensate the motion errors and to achieve 0.5 μm geometric accuracy in free surface machining. For the first step of the research, we tried to achieve 0.5 μm flatness. An artifact (optical flat) and a displacement sensor were used for measuring motion errors in Z direction on XY plane on a machine tool with ball screw feed drive systems. The repeatable error components were selectively modeled by using Fourier series. Z-axis was commanded to cancel the estimated motion errors. The compensation motion was provided by a piezo electric actuator that changed the preload of the support bearing of the ball screw. As the result, the variation of the relative position of the tool to the table was reduced from 1.3 μmP-V to 0.5 μmP-V. The compensation method was applied to a machining process using a single crystal diamond bite and the straightness of the profile curve was reduced from 1.0 μm to 0.4 μm.
Fumi TAKEOKA (Ph. D. Student, Department of Mechanical Engineering and Science, Kyoto University, Kyoto, Japan),
Masaharu KOMORI, Masaki TAKAHASHI, Aizoh KUBO (Department of Mechanical Engineering and Science,
Kyoto University, Kyoto, Japan),
Toshiyuki TAKATSUJI, Sonko OSAWA and Osamu SATO (National Metrology Institute of Japan, AIST, Ibaraki, Japan)
Vibration and noise is one of the serious problems for involute spur and helical gears used for drivetrain of vehicles. Gear tooth flank form of micrometer order markedly affects gear vibration and noise; therefore, the strict quality control of the tooth flank form must be performed to realize an excellent gear performance. However, since gear checker is structurally-complex, it is difficult to analyze how error factors of gear checkers influence the measurement result and the inspection and calibration method of gear checker has not been established yet. In this research, Virtual Gear Checker (VGC) is proposed, which is a simulation program of gear measurement considering the mechanisms and motions of gear checkers and possible error factors. The influence of the error factors on the measurement result can be clarified by VGC. VGC is also able to calculate the theoretical measurement result of non-involute helicoid artifact. It is easy for VGC to measure tooth flank form repeatedly in virtual space and therefore it can assess the uncertainty of measurement with gear checker. The uncertainty of gear measurement is calculated as an example.
Ki-Sun Kim (Ph. D Student, NOVIC, Department of Mechanical Engineering, KAIST, Daejeon, Korea),
Jong-oh Sun (Ph. D Student, NOVIC, Department of Mechanical Engineering, KAIST, Daejeon, Korea)
and Kwang-joon Kim (Professor, NOVIC, Department of Mechanical Engineering, KAIST, Daejeon, Korea)
Dynamic models for vibration isolation elements which show nonlinear characteristics in amplitude and frequency are sometimes required for more accurate response analysis of dynamic systems with such elements. Pneumatic springs in precision vibration isolation tables and hydraulic rubber mounts in automotive power train systems could be examples.q
Regarding experimental identification of nonlinearities, there exists no single generally accepted approach yet. In this study, a technique is proposed, which is based on measurements of both dynamic stiffness with amplitude as a parameter and frequency-modulation characteristics at a reference amplitude. The proposed dynamic modeling is shooting for quasi-linear response analysis in frequency domain and nonlinear transient response analysis in time domain.
The technique consists of basically two steps. The first step is to process complex dynamic stiffness measured as function of frequency at different displacement amplitudes to obtain quasi-linear dynamic model in the fractional form of frequency polynomials as the non-dimensional amplitude as a parameter. At this step, frequency shift characteristics of the dynamic stiffness depending on the vibration amplitude can be reflected as well. The second step is to process frequency modulation characteristics of the dynamic stiffness at a given displacement amplitude to obtain nonlinear terms in the time domain model.
Keisuke YAMADA (Assistant Professor, Department of Mechanical Engineering and Science, Kyoto University, Kyoto, Japan),
Hiroshi MATSUHISA, Hideo UTSUNO (Department of Mechanical Engineering and Science, Kyoto University, Kyoto, Japan)
and Jeong Gyu PARK (LG Electronics Inc., Korea)
This study describes the equivalent mechanical and electrical models for active and passive vibration control systems in flexible structures using piezoelectric elements. There are two main methods to suppress vibration in flexible structures using piezoelectric elements. One is active vibration control and the other is passive vibration suppression. Because they include both mechanical and electrical systems, the mechanism of the vibration suppression is complicated and can not be understood easily. To make matters worse, the knowledge of the mechanical vibration suppression devices like a dynamic vibration absorber and electrical circuits are not utilized in vibration control systems using piezoelectric elements. Hence, this study describes the way to derive the equivalent mechanical and electrical models for the original systems. Using those equivalent models, the mechanism of the vibration suppression can easily be comprehended and the knowledge of mechanical and electrical devices can be applied effectively. Occasionally several groups of piezoelectric elements are used in these vibration suppression devices to suppress multiple vibration modes or to obtain robustness of the devices. Therefore this study describes the way to derive the equivalent mechanical and electrical models for active and passive vibration control systems using several groups of piezoelectric elements.