| 1. |
Kazuya Yokota, Satoshi Ishikawa, Yosuke Koba, Shinya Kijimoto, Inverse analysis of vocal sound source by acoustic analysis of the vocal tract, 26th International Congress on Sound and Vibration, ICSV 2019, 2019.01, Diseases occurring near the vocal cords, such as laryngeal cancer, often cause voice disturbance as an initial symptom. As an acoustic diagnostic method for such diseases, the GRBAS (grade, roughness, breathiness, asthenia, strain) scale is widely used, but its objectivity is not well established. Instead, more accurate diagnosis may be possible by capturing the waveform of the volume velocity at the vocal cords (the vocal sound-source waveform). The aim of this study is to enable diagnosis of diseases near the vocal cords by identifying the sound-source waveform from voice measurements. In the proposed method, an analytical model of the vocal tract is used to identify the sound source. The air inside the vocal tract is modeled as concentrated masses connected by linear springs and dampers. The vocal tract shape is identified by making the natural frequencies of the analytical model correspond to the measured formant frequencies. The sound-source waveform is calculated from the analytical model by applying the measured voice (sound pressure) to the lip position of the identified vocal tract. To assess the validity of the proposed method, an experimental device was made to simulate the human voice mechanism. The device is equipped with artificial vocal cords made of a urethane elastomer that are self-excited by air flow. The sound pressure equivalent to the voice was measured using a microphone set at the lip position of the experimental device, and the flow velocity at the artificial vocal cords was measured using a laser Doppler velocimeter (LDV). To assess the model's validity, the sound-source waveform identified from the measured sound pressure was compared with the waveform measured using the LDV. |
| 2. |
Kazuya Yokota, Satoshi Ishikawa, Shinya Kijimoto, Yosuke Koba, Shohei Sugiki, Acoustic diagnosis of voice disturbance using an analytical model of the vocal tract, 25th International Congress on Sound and Vibration 2018: Hiroshima Calling, ICSV 2018, 2018.01, Laryngeal cancer and voice disturbance share the initial symptom of hoarseness of voice. By analyzing changes in the voice, these diseases might be diagnosed. Because it is important to detect these diseases as early as possible, there is demand for a simple and highly accurate diagnostic method. The GRBAS (grade, roughness, breathiness, asthenia, strain) scale is used as an acoustic diagnosis method for these disorders but its objectivity is not well established. Instead, more accurate diagnosis is possible by capturing the waveform of the flow velocity at the vocal cords. The aim of this study was to enable diagnosis of laryngeal cancer and voice disturbance by identifying the sound-source waveform from voice measurements. For acoustic analysis of the vocal tract, we modeled the air in the vocal tract as concentrated masses connected by linear springs and dampers. The vocal tract shape was identified by making the natural frequencies of the analytical model correspond to the measured formant frequencies. The sound-source waveform was calculated from the measured voice waveform. To assess the validity of the model, we measured actual voices and used the model to identify the vocal tract shapes and corresponding sound-source waveforms. The identified waveforms were similar to the Rosenberg wave, which is an approximation of the actual vocal sound-source waveform. Because of the influence of local solutions, multiple vocal tract shapes could be identified from a single sample. However, mathematical analysis showed that these differed in amplitude of sound-source waveform only, which does not affect the shape of the waveform. From this, we conclude that our proposed methods are valid.. |
| 3. |
Shotaro Hisano, Satoshi Ishikawa, Shinya Kijimoto, Yosuke Koba, Model-based active noise control for two-dimensional closed space by concentrated mass model, 46th International Congress and Exposition on Noise Control Engineering: Taming Noise and Moving Quiet, INTER-NOISE 2017, 2017.01, Several adaptive feedforward control methods have been proposed in previous research on active noise control. In those methods, noise control is achieved by adding in a reverse-phase control sound of the same amplitude to noise near an error microphone. Because this method is aimed at controlling only noise near the error microphone, the control area is inherently narrow. Here, we propose an alternative method of noise control for an entire closed space. The proposed method is based on state feedback control and modeling of the acoustic space by the concentrated-mass model. The acoustic space is modeled as masses, connecting springs, connecting dampers, and base support dampers. Further, a loudspeaker as control source is also modeled as a mass-spring-damper system. We previously reported a method for simple one-dimensional acoustic space control. In this paper, we show the design of a control system for two-dimensional acoustic spaces. The acoustic space and loudspeakers are modeled in a concentrated-mass model, and the state feedback control system is realized as a Kalman filter with pole placement. The number of degrees of freedom is reduced by using modal analysis, which reduces the computation time of the controller. Experiments and numerical simulation of the coupled system were conducted to confirm the validity of the analysis model. Noise in the acoustic space was experimentally controlled, with the finding that noise in the entire acoustic space was reduced around the resonance frequencies. Furthermore, the theoretically the limit of the control effect are considered within the proposed system.. |
| 4. |
WANG Xun, SATAKE Takayuki, KOBA Yosuke, Satoshi ISHIKAWA, KIJIMOTO Shinya, Active reduction of the two-way diffraction from a noise barrier by using feedforward control, Inter-Noise 2016, 2016.08.  |
| 5. |
Satoshi Ishikawa, Shinya Kijimoto, Matsuo Ataru, Akayama Yuta, Coupled analysis of two-dimensional acoustic and membrane vibration by concentrated mass model, 23rd International Congress on Sound and Vibration, ICSV 2016, 2016.01, When using the finite element method (FEM) for a structural-acoustic coupled analysis, the mass and stiffness matrices are not symmetric because the acoustic space is described by sound pressure and the structure is described by displacement. Therefore, eigenvalue analysis takes a long time. In our previous studies, we have proposed a concentrated mass model for in performing structural-acoustic coupled analysis. The advantage of this model is that the mass and stiffness matrices become symmetric because both the acoustic space and the membrane are described by the displacement of the mass points. However, some physically meaningless modes, such as spurious modes and zero eigenvalues, arise with this model. In this paper, we propose a new concentrated mass model that does not generate the spurious modes and zero eigenvalues. This model can be used to analyze a coupled system of a two-dimensional acoustic space and a membrane. The mass points of the new model are placed at the sides of elements rather than at nodal points. To confirm the validity of the proposed model, the natural frequency obtained by using the concentrated mass model is compared with the natural frequency found by using FEM. These results are in good agreement, and spurious modes and zero eigenvalues are not generated in the proposed model. Furthermore, we compared the proposed model with FEM in terms of the time required for the eigenvalue analysis. Because the mass and stiffness matrices of the proposed model are symmetric, its eigenvalue analysis is faster than that of FEM, whose matrices are asymmetric. Therefore, we conclude that the proposed model is valid for coupled analysis of a two-dimensional acoustic space and membrane vibration, and that it is superior to FEM in terms of calculation time.. |
| 6. |
Xun Wang, Yosuke Koba, Satoshi Ishikawa, Shinya Kijimoto, Locally global active noise control based on wavefront synthesis, 23rd International Congress on Sound and Vibration, ICSV 2016, 2016.07, This paper presents an active noise control (ANC) approach to reducing noise in a certain area by controlling the sound pressure at a local point based on the concept of wavefront synthesis. Multi-input and multi-output (MIMO) ANC systems can achieve the global control of noise. However, the computational complexity of the control algorithm and the complicated hardware configuration limit the use of MIMO systems. In order to simplify the system structure, a concept of dividing a global ANC system into sub-systems according to the control objectives is considered in this paper. One sub-system is to reproduce the wavefront of the incident noise into the target area, and the other one is to tune the amplitude and phase of the reproduced control sound wavefront. The first system objective can be realized by a sound field reproduction method, and the latter one can be implemented by a single-input and single-output (SISO) ANC system. Based on this concept, a locally global ANC system using a loudspeaker array that reproduces planar waves according to the incident angle of the noise is proposed. Numerical simulations are conducted to verify the effectiveness of the system. The results show that the proposed system can effectively reduce the noise in the target area regardless of the incident angle of the noise.. |
| 7. |
Xun Wang, Yosuke Koba, Satoshi Ishikawa, Shinya Kijimoto, Development of indoor hybrid active noise barrier, 22nd International Congress on Sound and Vibration, ICSV 2015, 2015.07, This paper develops an indoor active noise barrier (ANB) by using a hybrid active noise control (HB-ANC) system. The HB-ANC system reduces the noise diffracted from the top of the ANB and the noise propagated to the head position of the target person behind the ANB simultaneously to achieve higher noise attenuation. However, the waterbed effect of the feedback control part of the HB-ANC system will cause noise enhancement at some frequencies in the control area. In the paper, in order to solve this problem, a filter able to cancel the noise enhancement is integrated into the HB-ANC system. Then, the noise attenuation performance of the ANB under four sound field configurations is verified by simulations. The sound field configurations are set up to investigate how the diffraction from side of the ANB and the reflection influence the performance of the ANB. An experiment in the anechoic chamber is also conducted. The simulation and experiment results indicate that the low frequency noise can be reduced in a wide area behind the ANB, and at the head position of the person, the noise attenuation can be obtained within a wider frequency range, even for the sound fields where the diffraction from side and the reflection exist.. |
| 8. |
Xun Wang, Yosuke Koba, Satoshi Ishikawa, Shinya Kijimoto, Hybrid active noise barrier with sound masking (Experiment for verifying the noise attenuation performance in an office room and evaluation of maskers by listening experiments), 44th International Congress and Exposition on Noise Control Engineering, INTER-NOISE 2015, 2015.08, A hybrid active noise barrier (ANB) integrating sound masking techniques, which aims to abate the noise problem and improve the speech privacy in open plan offices, has been proposed in the previous work. This ANB exploits a hybrid active noise control (ANC) system with sound masking techniques to reduce and mask the target sound simultaneously, so less masker power is needed to achieve the same masking performance with the conventional sound masking techniques. In the previous work, the effectiveness of the ANB has been verified by computer simulations and by experiments in an anechoic chamber. In this paper, an experiment is conducted to verify the noise attenuation performance of the ANB in the sound field of a real office room. The influence of background noise on the noise attenuation performance of the ANB is also investigated in the experiment. Moreover, in order to select an appropriate masker for the sound masking part of the control system, several types of maskers are compared and investigated by listening experiments in this paper.. |
| 9. |
WANG Xun, KOBA Yosuke, ISHIKAWA Satoshi, KIJIMOTO Shinya, Hybrid active noise barrier with sound masking, Inter Noise 2014, 2014.11. |
| 10. |
ISHIKAWA Satoshi, KIJIMOTO Shinya, OWAKI Ryoma, MATSUO Ataru, Coupled analysis of two-dimensional acoustic and membrane vibration by concentrated mass model, Inter Noise 2014, 2014.11. |
| 11. |
HISANO Shotaro, ISHIKAWA Satoshi, KIJIMOTO Shinya, KOBA Yosuke, Active noise control based on state feedback by a concentrated mass model, Inter Noise 2014, 2014.11. |
| 12. |
Shotaro Hisano, Satoshi Ishikawa, Shinya Kijimoto, Yosuke Koba, Active noise control based on state feedback by a concentrated mass model, 43rd International Congress on Noise Control Engineering: Improving the World Through Noise Control, INTERNOISE 2014, We herein propose a new model-based control method, in place of traditional adaptive control, for a low-frequency noise problem in a closed space. The proposed control method is based on state feedback control and a model of the acoustic space obtained by the concentrated mass model. Thus, we can control noise in the entire space. According to the concentrated mass model, the acoustic space is modeled as masses, connecting linear springs, connecting dampers, and base support dampers. Furthermore, a loudspeaker, as a control source, is also modeled by a mass, a spring, and a damper. In the present paper, as a first step, we constructed a coupled analysis model of a one-dimensional sound field and the loudspeaker. We designed the model-based system for the standing sound wave in the low-frequency band. Specifically, we realized a state feedback control system based on a Kalman filter and pole placement. Modal reduction using modal analysis is conducted to reduce the computation time of the controller. Then, we conducted experiments and a numerical simulation of the one-dimensional sound tube to confirm the validity of the analysis model. Moreover, we perform an experiment to control the noise in the sound tube. The noise is reduced around the resonance frequency in the entire space. Therefore, the proposed method is valid for noise control in a closed space.. |
| 13. |
Satoshi Ishikawa, Shinya Kijimoto, Ryoma Owaki, Ataru Matsuo, Coupled analysis of two-dimensional acoustic and membrane vibration by concentrated mass model, 43rd International Congress on Noise Control Engineering: Improving the World Through Noise Control, INTERNOISE 2014, In the finite element method of a structural-acoustic coupled analysis, the mass matrix and the stiffness matrix are not symmetrical. Therefore, the modal analysis cannot be applied directly to the coupled problem. In our previous study, a concentrated mass model was proposed to analyze a two-dimensional acoustic analysis. The model consists of the masses, the connecting springs. It is very easy to couple the structure and acoustic field by the concentrate mass model. Furthermore, the mass matrix and the stiffness matrix are symmetrical. In this paper, we propose a concentrated mass model to perform a coupled analysis of a two-dimensional acoustic and a membrane vibration. And we propose a coupling method to arrange of the masses of the air near the membrane. To confirm the validity of the proposed model, the natural frequency obtained by the concentrated mass model is compared with the natural frequency by the modal coupling method. These results are in good agreement. Therefore, it is concluded that the proposed model is valid for the coupled analysis of an acoustic and a vibration analysis.. |
| 14. |
Xun Wang, Yosuke Koba, Satoshi Ishikawa, Shinya Kijimoto, Hybrid active noise barrier with sound masking, 43rd International Congress on Noise Control Engineering: Improving the World Through Noise Control, INTERNOISE 2014, In this paper, a hybrid active noise barrier (ANB) with sound masking capability is considered. To protect the speech privacy, several sound masking techniques have been developed. However, these sound masking techniques based on the superposition of the masker and original sound will lead to increase in the loudness of the sound after masking. Against this problem, this paper proposes a soundproof system which combines an ANB with a sound masking system. The ANB applies a new type of hybrid active noise control (ANC) system, which can reduce the noise diffraction and the noise propagated to the ear positions of the people behind the ANB simultaneously, to attenuate the conversation sound. Consequently, the required volume of the masker sound will decrease because of the smaller loudness of the original conversation sound in the control area. The sound masking system applies a method which can generate masker based on the frequency properties of the original sound. Several simulations are carried out to investigate the sound attenuation and sound masking performance of this system, and the results show that comparing with the traditional sound masking system, the proposed system needs smaller masker sound to achieve the sound masking effect.. |
| 15. |
ISHIKAWA Satoshi, KIJIMOTO Shinya, KOBA Yosuke, OWAKI Ryoma, MORI Yuki, Two-dimensional Acoustic Analysis by Concentrated Mass Model, Inter Noise 2013, 2013.09. |
| 16. |
SUGIKI Shohei, ISHIKAWA Satoshi, KIJIMOTO Shinya, KOBA Yosuke, Simulation of Speech Production by Concentrated Mass Model, Inter Noise 2013, 2013.09. |
| 17. |
TANIGUCHI Tishiro, KOBA Yosuke, ISHIKAWA Satoshi, KIJIMOTO Shinya, Active Noise Control Considering Moving Evaluation Point in Actual Sound Field, The 3rd Japan-Korea Joint Symposium on Dynamics and Control, 2013.08. |
| 18. |
TAKAHASHI Akihiro, KIJIMOTO SHINYA, ISHIKAWA Satoshi, KOBA Yosuke, Sound Masking Using Active Noise Control, The 3rd Japan-Korea Joint Symposium on Dynamics and Control, 2013.08. |
| 19. |
Kazuya YOKOTA, Shinya Kijimoto, ISHIKAWA Satoshi, Yosuke KOBA, Active Noise Control with Changing Adaptive Behavior Algorithm, The 3rd Japan-Korea Joint Symposium on Dynamics and Control, 2013.08. |
| 20. |
Shohei Sugiki, Satoshi Ishikawa, Shinya Kijimoto, Yosuke Koba, Simulation of speech production by concentrated mass model, 42nd International Congress and Exposition on Noise Control Engineering 2013: Noise Control for Quality of Life, INTER-NOISE 2013, Larynx cancer or pulmonary problems cause the initial symptoms such as hoarse voice. There is a possibility of diagnoses of the affected area by analyzing these changes of voice. In this study, our purpose is to enable diagnoses of larynx cancer or pulmonary problems by an acoustic analysis model inside of the vocal tract. As a first step, we aimed to establish an acoustic analysis method in the vocal tract, and identification method of vocal tract shapes and vocal sound source waveforms. In this paper, we modeled the air in the vocal tract as a concentrated mass model that consists of masses, connecting linear springs, connecting dampers, and base support dampers. And we make an acoustic analysis model in the vocal tract. Then we identified the vocal tract shapes by using the Levenberg-Marquardt method, and analyzed vocal sound source waveforms by using the transfer matrix method from the measured voice wave. And we simulated a speech production by the analyzed sound source. The identified vocal tract shapes are valid and the analyzed vocal sound source waveforms are similar to the Rosenberg wave. The speech production results are clear voices. Then, we conclude our proposed methods are valid.. |
| 21. |
Satoshi Ishikawa, Shinya Kijimoto, Yosuke Koba, Ryoma Owaki, Yuuki Mori, Two-dimensional acoustic analysis by concentrated mass model, 42nd International Congress and Exposition on Noise Control Engineering 2013: Noise Control for Quality of Life, INTER-NOISE 2013, FDTD method and CIP method are used for an acoustic analysis in time domain. However, these methods do not take into account a sound attenuation from viscosity. In our study, we propose a concentrated mass model which consists of spring-mass-damper system to perform a two-dimensional acoustic analysis. The dampers of this model consider viscosity of air. In this paper, we derive mass, connecting springs, connecting dampers, and base support dampers. The characteristic of the connecting spring is derived from the condition of adiabatic change of air, and the connecting damper is derived from the normal stress. To confirm the validity of the proposed model, the numerical results obtained by the concentrated mass model are compared with the theoretical value of the traveling wave, and with the theoretical value of the natural frequency. All numerical computational results agree very well with the theoretical values. Therefore, it is concluded that the proposed model is valid for the two-dimensional acoustic analysis.. |
| 22. |
Yoshiko Ohno, KOBA Yosuke, ISHIKAWA Satoshi, Shinya Kijimoto, Active Noise Control for a Moving Evaluation Point Using Stepsize Vector and Secondary Path Interpolation, Mjiit-Juc Joint Symposium, 2012.11. |
| 23. |
Yasuhiro Shimada, ISHIKAWA Satoshi, Shinya Kijimoto, DEVELOPMENT IN MEASUREMENT METHOD AND ANALYSIS MODEL OF LIVING BODY, Mjiit-Juc Joint Symposium, 2012.11. |
| 24. |
Xun Wang, Shinya Kijimoto, Yosuke Koba, Koichi Matsuda, Noise barrier using feedback active noise control, 40th International Congress and Exposition on Noise Control Engineering 2011, INTER-NOISE 2011, In this paper, a kind of active noise barrier (ANB) using active noise control (ANC) technique to improve noise attenuation in low frequencies is proposed. The ANB consists of an ordinary noise barrier, three active noise control units (ANCU) and a DSP (TMS 320C6713 DSK). Feedback ANC system is used in the ANCUs. In order to achieve higher noise attenuation, fast transversal filter adaptive algorithm is introduced into the feedback ANC system. An investigation into the acoustic boundary generated by an ANCU is conducted. It is shown that the acoustic power flow around the surface of an ANCU reduced when control is turned on. Also, numerical and experimental study on an active noise barrier is conducted. As a result, the active noise barrier shows better noise attenuation performance in low frequencies.. |
| 25. |
Koichi Matsuda, Shinya Kijimoto, Reaction disturbance cancellation for a magnetically levitated ladder arm of clean-room robot, 36th Annual Conference of the IEEE Industrial Electronics Society, IECON 2010, 2010.12, This paper treats a disturbance cancellation problem for minimizing the effects of reaction forces on position accuracy of a clean-room robot applied with magnetic bearings. The robot is composed of a main body and a ladder arm, and moves without friction at joints owing to magnetic support. The support stiffness is, however, weaker than the conventional bearings, and the ladder arm moves in reaction to rotary motion of the main body. A feedforward controller is designed to compensate the effects of the reaction forces, and implemented successfully to reduce the transverse displacements of the ladder arm when the main body rotates.. |
| 26. |
Ikuma Ikeda, Yosuke Koba, Shinya Kijimoto, Koichi Matsuda, Active noise control using filter map in 3-dimensional acoustic field, 38th International Congress and Exposition on Noise Control Engineering 2009, INTER-NOISE 2009, On active noise control in 3-dimensional acoustic field, a control effect reduces when an evaluation point moves. Against this problem, we proposed control with filter map. In this algorithm, a control area is divided into small grids. Adaptive filters are accumulated and corresponding to the node. The controller is updated from the accumulation. Effectiveness of this algorithm was shown in simulations. In this paper, the validity of this algorithm is shown in several simulations and experiments in an anechoic chamber. The evaluation point moves 0.4m at the speed of 0.45m/s in experiment. A CCD camera detects a position of the point. From the experimental results, it is shown that the effectiveness of the proposed algorithm is 10dB more than the that of the direct adaptive algorithm.. |
| 27. |
Koichi Matsuda, Shinya Kijimoto, An approach to designing a magnetic-bearing system for smaller rotating machines, 2008 IEEE International Symposium on Industrial Electronics, ISIE 2008, 2008.12, This paper presents a design of a magnetic-bearing system well suited for a smaller rotating machine. The system contains two 3-pole active radial bearings and an optimal passive axial bearing. The effects of number of stator poles are investigated on the rotor outside diameter for an outer-rotor type of radial bearing, and the investigation reveals that 3-pole bearings yield the smallest rotor outside diameter for a stator-eore diameter less than 50 mm. The structural configuration of the axial bearing is also optimized to have the largest support stiffness. Those radial and axial bearings are integrated in a homopolar configuration to yield a smaller magnetic-bearing system.. |
| 28. |
Young Chul Park, Yoichi Kanemitsu, Shinya Kijimoto, Koichi Matsuda, Yosuke Koba, Structural - Acoustic coupled analysis in consideration of sound absorption characteristics of materials, 35th International Congress and Exposition on Noise Control Engineering, INTER-NOISE 2006, 2006.12, In order to perform acoustic analysis with sufficient accuracy, the method of treating sound absorption characteristics is important. Modeling theories using flow resistance or complex density / complex sound velocity are generally used in the modeling methods of porous materials. However, since it is difficult to find out necessary material characteristic for prediction of the sound absorption characteristic, acoustic characteristics of sound absorption material may be unable to be predicted. In this research, an easy modeling method of sound absorption material will be proposed for analyzing the 3-dimensional acoustic field that has a sound absorption material. Therefore, an experiment was conducted on the sound tube that has a sound absorption material. The validity of a simple modeling method of sound absorption material is verified by comparison of the experimental result and the calculated result. And the simple modeling method will be applied to automatic water supply equipment. An optimal arrangement of the sound insulation / absorption material was calculated by the numerical analysis. Consequently, the noise could be reduced by 4dB(A). In addition, structural acoustic coupled analysis is due to be performed to the noise reduction in consideration of the sound absorption characteristic of material of automatic water supply equipment.. |
| 29. |
Shinya Kijimoto, Yasumasa Imamura, Yoichi Kanemitsu, Koichi Matsuda, Yosuke Koba, Active noise control using online secondary path identification algorithm, 35th International Congress and Exposition on Noise Control Engineering, INTER-NOISE 2006, Considering about practical use of active noise control in 3dimensional sound field, it is difficult to obtain characteristic of a secondary path (acoustic path from the secondary source to the error microphone) beforehand. In this paper, a FTF algorithm that has fast converging property is newly introduced to a direct adaptive algorithm which does not need the secondary path characteristic beforehand. A numerical simulation is carried out with a sound field that the error path changes during control. Experiments are also carried out. The effectiveness of the proposed algorithm is shown through both the simulations and the experiments.. |
| 30. |
Koichi Matsuda, Shinya Kijimoto, Yoichi Kanemitsu, Self-sensing three-pole magnetic bearing using a Kalman filter, 2006 SICE-ICASE International Joint Conference, Self-sensing active magnetic bearing is designed by a new approach. The approach aims to solve the observer bias problem by introducing a Kalman filter. In order to verify the validity of the approach, a Kalman filter is designed for a three-pole homopolar magnetic bearing and used to estimate the radial displacement and velocity of the rotor. The electric current is driven by a linear power-amplifier circuit to flow through the coils, and the coil terminal voltage is passed through an analog first-order low-pass filter with a cut-off frequency of 100 Hz. The designed Kalman filter uses the filtered coil-voltage and the controller inputs as an input for calculating the estimate. The unobservable bias is estimated as an unknown state, and the Kalman-filter estimates are numerically simulated by the measured input/output data. The results show that the bias is successfully estimated to overlap the estimated displacement to its measurement.. |
| 31. |
Koichi Matsuda, Yoichi Kanemitsu, Shinya Kijimoto, Stability-optimized clearance configuration of fluid-film journal bearings, DETC2005: ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, A clearance configuration of fluid-film journal bearings is optimized in a sense of enhancing the stability of a full circular bearing at high rotational speeds. A performance index is chosen as the sum of the squared whirl-frequency ratios over a wide range of eccentricity ratios, and a Fourier series is used to represent an arbitrary configuration of fluid-film bearings. An optimization problem is then formulated to find the Fourier coefficients to minimize the index. The whirl-frequency ratio is inversely proportional to the stability threshold speeds of a Jeffcott rotor. The short bearing approximation is used to simplify a mathematical model that describes a pressure distribution developed in a fluid-film bearing. The designed bearing cannot destabilize the Jeffcott rotor at any high rotating speed subject to the short-bearing assumption and significantly reduces the size of the unstable region for a finite-length bearing with a small length-to-diameter ratio.. |
| 32. |
Koichi Matsuda, Natsuki Kawamura, Yoichi Kanemitsu, Shinya Kijimoto, Katsuhide Watanabe, Eiichi Izumi, Active vibration suppression on an image of a scanning electron microscope, Metrology, Inspection, and Process Control for Microlithography XIV, 2000.01, This paper proposes a new approach to reducing an effect of floor vibration on an image of a scanning electron microscope. An image-shifting coil is used to move the electron probe in order to cancel undesirable motion of a specimen due to the floor vibration. The floor vibration is structurally transmitted through the microscope and detected by two acceleration sensors at the root of the specimen chamber of the microscope. The outputs of the acceleration sensors are fed forward into a controller to move the electron probe by the image-shifting coil. The feed-forward controllers are designed in two ways. The first one is based on a transfer function from the sensor outputs to the relative displacement of a specimen to the electron probe being at rest. The microscope is put on a table attached to a shaker. Sinusoidal excitation tests are done many times to estimate the transfer functions from vibrating images of a micro scale. Moreover, the second controller is designed by manually amplifying and delaying the sensor outputs so as to minimize amplitude of the vibrating images on a CRT. Those two controllers are implemented as a digital filter running on a digital signal processor.. |
| 33. |
Koichi Matsuda, Yoichi Kanemitsu, Shinya Kijimoto, Attitude control of a space robot using the nonholonomic structure, Guidance, Navigation, and Control Conference and Exhibit, 1998, 1998.01, This paper treats the attitude control of a space robot using the fact that a free-flying space robot can reorient its attitude only by moving the manipulators. We solve an optimal control problem formulated in a more general way than those of the problems to have been solved so far. That is, our approach can afford to solve the case where the initial and final postures of the manipulators are different and where the solution could not be a smooth and continuous function of time. The optimal control problem is discretized by the rectangular rule into a mathematical programming problem to be solved by the periodically preconditioned conjugate gradient-restoration algorithm. A space-robot model with a multi-link manipulator is used to exemplify the present approach.. |
| 34. |
Koichi Matsuda, Yoichi Kanemitsu, Shinya Kijimoto, Regulator/Kalman filter design for realizing wave-based controllers, Guidance, Navigation, and Control Conference and Exhibit, 1996, 1996.01, In this paper, we put forth the idea that a wave—based controller can be realized by using a noisy modal model. This idea is based on the fact that a wave-based input—output relation may be interpreted as that of a usual modal model contaminated with colored measurement noise. Specifically, an identical controller can be derived from models based on either a traveling wave or standing one on a flexible structure. In general, we can design a controller in terms of a regulator and a Kalman filter in a linear stochastic system. Since the Kalman filter contains unknown dynamics of the colored noise in the present system, this dynamics can be selected to realize the wave-based controllers. Furthermore, we design a controller for vibration suppression of a flexible beam to investigate the validity of this idea numerically. The results show that a modal compensator agrees with the wave-based one well, and yields a new interpretation of a wave-based controller.. |
| 35. |
Shinya Kijimoto, Akio Nagamatsu, Kazuto Seto, Youichi Kanemitsu, Vibration control of the structure with an active mechanical component, 1989 ASME Pressure Vessels and Piping Conference, 1990.09, In order to control vibration, many mechanical structures have recently begun using active elements. Up to now, in cases of designing such structures, structural analysis and design of the controller were carried out separately, and a controller was apt to become too complex. This paper investigates a design method that can use both vibration analysis and the controller design. This method is to design a controller by using both the transfer functions of the controller and whole structure.. |
| 36. |
Shinya Kijimoto, A. Nagamatsu, K. Seto, Y. Kanemitsu, Vibration control of the structure with an active mechanical component, Seismic Engineering - 1989: Design, Analysis, Testing, and Qualification Methods, 1989.12, In order to control vibration, many mechanical structures have recently began using active elements. Up to now, in cases of designing such structures, structural analysis and design of the controller were carried out separately, and a controller is apt to become too complex. This paper investigates a design method that can use both vibration analysis and the controller design. This method is to design a controller by using both the transfer functions of the controller and whole structure.. |
