Yasuhiro Ohyama

Tokyo University of Technology, Edo, Tōkyō, Japan

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Publications (93)23.92 Total impact

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    ABSTRACT: It is an urgent need to find an objective way to estimate the degree of fatigue of employees. In this study, we designed a monitoring and estimation system for the degree of fatigue. This paper explains a long-term pedaling experiment that we use it to explore the possibility to use only the time sequence data of head movement during pealing to estimate the fatigue. While we show the possibility for this through experimental data, it is clear that we need to collect more data to establish an estimation method.
    No preview · Conference Paper · Jul 2014
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    ABSTRACT: This research presents a precision computation approach that improves product machining accuracy of existing six-axis parallel link mechanism in product modeling and product testing, as a part of main research project on build-to-order manufacturing of wearable metal muscle supporters for human legs and arms. As the actual design object is in the shape of semi-elliptical helix, we approximate this design with a sum of arcs from different elliptical helixes that connected into give the desired build-to-order shape. The proposed computation methods are applied in product modeling phase and product testing phase. In modeling phase, parameter calculation of proper surface direction is addressed to avoid unwanted surface shape deformations like excessive twisting than that of the object center. In testing phase, elliptical fitting problem for noisy and possible incomplete data is addressed as an optimization approach. Comparisons of linear and nonlinear fitting criteria are performed for shape direction detection.
    No preview · Conference Paper · Apr 2014
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    ABSTRACT: This paper describes a structure and soft finger model of digital hand for real-time dexterous manipulation. From investigations of human dexterous manipulation by using high speed camera, the structure and skin conditions of digital hand are defined. To evaluate our model, bar spinning as dexterous manipulation is adopted. Comparing manipulations with human hand and digital hand, we discuss its effectiveness and problems of our model.
    No preview · Article · Mar 2014
  • Q. Shi · L. Ouyang · J. She · L. Xu · J. Imani · Y. Ohyama
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    ABSTRACT: A method of compensating for Stribeck-type nonlinear friction torque for a two-mass mechatronic system has been devised based on the equivalent- inputdisturbance (EID) approach. The nonlinearity in the system is treated as an input-dependent disturbance, and an EID estimator is designed that estimates it. The incorporation of the estimate into the control input compensates for the nonlinearity. Simulation results demonstrate the validity of the method and show that the compensation accuracy is closely related to the time constant of the low-pass filter.
    No preview · Article · Mar 2014 · Journal of Advanced Computational Intelligence and Intelligent Informatics
  • T. Ishikawa · K. Makino · J. Imani · Y. Ohyama
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    ABSTRACT: This research addresses a gait motion planning problem for a six-legged robot walking on an irregular field. In this proposal, we used a simplified neural network model called an Associatron that recalls total motion patterns sequentially frompartial information. The Associatron is used here because it is more effective and adaptable than conventional methods. Using the proposed method, the robot is expected to walk in unknown fields. After verifying planning using an Open Dynamics Engine (ODE) by using simulations, we found that memorized patterns are recalled from developed patterns. We then conducted experiments using a real developed robot. Experiment results show that, when using the proposed planning method, the robot selects suitable gait motion patterns in the presence of an obstacle.
    No preview · Article · Mar 2014
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    ABSTRACT: This research proposes an effective vertical clustering strategy of 3D data in an elliptical helical shape based on 2D geometry. The clustering object is an elliptical cross-sectioned metal pipe which is been bended in to an elliptical helical shape which is used in wearable muscle support designing for welfare industry. The aim of this proposed method is to maximize the vertical clustering (vertical partitioning) ability of surface data in order to run the product evaluation process addressed in research [2]. The experiment results prove that the proposed method outperforms the existing threshold no of clusters that preserves the vertical shape than applying the conventional 3D data. This research also proposes a new product testing strategy that provides the flexibility in computer aided testing by not restricting the sequence depending measurements which apply weight on measuring process. The clustering algorithms used for the experiments in this research are self-organizing map (SOM) and K-medoids.
    Preview · Article · Feb 2014
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    ABSTRACT: This research proposes a computation approach to address the evaluation of end product machining accuracy in elliptical surfaced helical pipe bending using 6dof parallel manipulator as a pipe bender. The target end product is wearable metal muscle supporters used in build-to-order welfare product manufacturing. This paper proposes a product testing model that mainly corrects the surface direction estimation errors of existing least squares ellipse fittings, followed by arc length and central angle evaluations. This post-machining modelling requires combination of reverse rotations and translations to a specific location before accuracy evaluation takes place, i.e. the reverse comparing to pre-machining product modelling. This specific location not only allows us to compute surface direction but also the amount of excessive surface twisting as a rotation angle about a specified axis, i.e. quantification of surface torsion. At first we experimented three ellipse fitting methods such as, two least-squares fitting methods with Bookstein constraint and Trace constraint, and one non- linear least squares method using Gauss-Newton algorithm. From fitting results, we found that using Trace constraint is more reliable and designed a correction filter for surface torsion observation. Finally we apply 2D total least squares line fitting method with a rectification filter for surface direction detection.
    Preview · Article · Feb 2014
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    ABSTRACT: The Karvonen formula, which is widely used to estimate exercise intensity, contains maximum heart rate, HR max, as a variable. This study employed pedaling experiments to assess which of the proposed formulas for calculating HR max was the most suitable for use with the Karvonen formula. First, two kinds of experiments involving an ergometer were performed: an all-in-one-day experiment that tested eight pedaling loads in one day, and a one-load-per-day experiment that tested one load per day for eight days. A comparison of the data on 7 subjects showed that the all-in-one-day type of experiment was better for assessing HR max formulas, at least for the load levels tested in our experiments. A statistical analysis of the experimental data on 47 subjects showed two of the HR max formulas to be suitable for use in the Karvonen formula to estimate exercise intensity for males in their 20 s. In addition, the physical characteristics of a person having the greatest impact on exercise intensity were determined.
    Full-text · Article · Feb 2014 · International Journal of Automation and Computing
  • J. She · H. Nakamura · J. Imani · Y. Ohyama
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    ABSTRACT: In this study, we developed a new system for measuring and monitoring the degree of an employee's fatigue. The system is comprised of an ergometer, a pulsometer, a Kinect sensor, and a computer. It records the heart rate and the 3D motion of a subject during a pedaling exercise. This system is simple, inexpensive, and easy to use. This paper explains the construction of the system, and reports the results of verification experiments with a special focus on the use of the Kinect sensor. The results show that the Kinect sensor is a useful tool for recording body movement and that the system may be used to measure and monitor the degree of fatigue.
    No preview · Article · Jan 2014 · Journal of Advanced Computational Intelligence and Intelligent Informatics
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    ABSTRACT: We propose affective image classification on dimensional affective groups against conventional discrete affective groups which does not cover all three emotional vectors. This approach serves as affective group identification phase of a full emotion estimation model from affective pictures. The known emotional vector values Valence, Arousal and Dominance of IAPS photo set for all subjects are categorized into nine affective groups using few well known clustering algorithms and the clusters are evaluated by using photo description. The texture and histogram based graphical features of photographs without borders within the SOM based affective groups are evaluated by using the pattern recognition tools of neural network to identify the affective groups where the inputs originated. The test results proved that the gray scale is suitable for high valence or high arousal groups, edges and corners are suitable for high valence groups and blue histogram is useful in high arousal groups. Single or logical combination of these trained networks can be used for affective group recognition in high arousal or valence group. High dominance groups are under development.
    No preview · Article · Mar 2013
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    ABSTRACT: In this research, a classification method for human touching behaviors to haptic therapy robot is proposed. It is difficult to apply explicit discrete representation for human touch behaviors such as “slap”, “pat” due to the existence of intermediate touch behavioral patterns. Therefore a new classification approach for human touch behaviors using Self Organizing Map (SOM) is proposed, using its ability to classify the nearby data in to a group. Further in this research the axis of out put maps are defined to be meaningful by specifying the initial placement of the input data during the training process.
    No preview · Conference Paper · Jan 2013
  • J. She · H. Nakamura · K. Makino · Y. Ohyama · H. Hashimoto · M. Wu
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    ABSTRACT: Maximum heart rate (MHR) is commonly used to estimate exercise intensity with the Karvonen formula, and there are several methods of calculating it. In this study, we used pedaling experiments on a cycle ergometer to evaluate methods of determining MHR in order to select the ones most suitable for the Karvonen formula. In the experiments, 43 subjects rode an aerobike. The results show that, for people in their 20s, two methods are suitable for estimating exercise intensity with the Karvonen formula. The main physical parameters affecting exercise intensity were also extracted, based on the experimental results.
    No preview · Article · Jan 2013
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    ABSTRACT: This paper describes dexterous manipulation of the digital hand we have developed, whose structure is based on human hand. The purpose of the development is to investigate good shape design for anyone to make use of it easily, the technology transfer in man hand and the novel operation of robot hand. To do this, it is necessary to examine the force distribution generating on a contact point between hand and object. We have developed the estimation systems; one is the dynamics simulation space that has the collision calculation function. The other is the shape inspection of hand with a high-speed camera which is able to record the dexterous hand motion. As a dexterous manipulation, bar spinnings by the digital hand are examined.
    No preview · Article · Aug 2012
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    Preview · Article · Jul 2012
  • K. Makino · J.-H. She · Y. Ohyama
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    ABSTRACT: It has been proposed a method that the all autonomous mobile robots share a common coordinate system without the communication among them and without recognition of the landmarks or maps. However, the effectiveness of the only directional method is confirmed by analysis and simulations. This paper describes the positional modification method, newly. The effectiveness of is confirmed by the simulations. As a result, it is found out that the method has optimal values.
    No preview · Article · Jan 2012
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    Jinhua She · Xin Xin · Yasuhiro Ohyama
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    ABSTRACT: This paper explains how to use an arm robot experiment system to teach sampled-data H∞ control theory. A design procedure is presented for a digital tracking control system for a continuous plant with structured uncertainties; the target is the positioning control of an arm robot. To guarantee the robust stability of the closed-loop system and provide the desired closed-loop performance, the design problem is first formulated as a sampled-data H∞ control problem, and is then transformed into an equivalent discrete-time H∞ control problem. Finally, linear matrix inequalities are used to obtain a reduced-order output-feedback controller and a static state-feedback controller. In a course, the design procedure is explained and practice is provided through simulations and experiments. © 2011 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.
    Preview · Article · Nov 2011 · IEEJ Transactions on Electrical and Electronic Engineering
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    ABSTRACT: This paper describes an approach to estimate human hand posture using 3-dimensional range data. The approach employs an approximation of the human hand with a plane in the 3-dimensional space. While this approximation is not so precise for detail reconstruction of the hand shape, it is intended for tracking of the human hand in applications such as virtual reality applications, in which relatively low precision is acceptable.
    No preview · Article · Nov 2011
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    ABSTRACT: This paper presents development of an evaluation system for easiness of manipulation of product shapes to design better product shapes. In developing the evaluation system, we concentrate mainly on manipulation which involves handling state such that even when the product is rotating it remains near the hand. The evaluation system consists of a glove type hand posture measuring instrument and physics simulation software environment in which a hand model moves in accordance with the pose of the hand wearing the glove. Observation of hand manipulation is also performed with a high-speed camera to analyze the motion and improve the evaluation system.
    No preview · Article · Jun 2011
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    ABSTRACT: This research focuses on the electric wheelchair controlled by Human Body Motion Interface (HBMI). HBMI uses the body motion which is caused by the voluntary motion. From our previous research, it has been confirmed that HBMI, which uses the center of weight on the pressure sensor attached on the backrest, has the ability of an interface. However the problem has also remained. The velocities of each wheel have determined based on the error between initial and current position of center of weight. When user tries to stop the wheelchair, user has to rigorously return the center of weight to the initial position. Therefore, if a slight error remains on the center of weight, the wheelchair is not able to stop exactly. This paper absorbs ambiguous human motion, and proposes the control scheme to prevent miss operation of wheelchair caused by slight variation of the center of weight.
    No preview · Article · Jun 2011
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    ABSTRACT: This research focuses on the electric wheelchair controlled by Human Body Motion Interface (HBMI). HBMI uses the body motion which is caused by the voluntary motion. From our previous research, it has been confirmed that HBMI, which uses the center of weight on the pressure sensor attached on the backrest has the ability of an interface. However the problem has also remained. The velocities of each wheel have determined based on the error between initial and current position of center of weight. The error increases in the proportion to the inclination of the body. In some cases, the error doesn't increase due to the contact condition between body and backrest, even if the user leans own body. In this case, therefore, the user cannot control the wheelchair arbitrarily in spite of leaning his/her body. This paper shows the improvement to control wheelchair regardless of the amplitude of the error. I. INTRODUCTION
    No preview · Article · May 2011