An obstacle avoidance method using a virtual impedance wall is proposed for a multi-legged robot. The swing legs use compliance control to make soft contact and avoid colliding with objects, so that the robot maintains the moving direction as far as possible while the swing legs maintain a preferred operating region. The preferred operating region is surrounded with a virtual impedance wall. When the leg passes over the threshold of the preferred operating region, the moving direction is modified by the virtual repulsive force from the virtual impedance wall to avoid the workspace limitation. Moreover, the pattern recognition technique using the support vector machine is implemented for estimating the contact point between the object and the body by using the data set of the error of each leg. The virtual impedance field is set at the estimated contact position to direct the aspect of avoidance. The robot is pushed and rotated by the virtual repulsive force from the impedance field. These passive motions from the virtual impedance model can provide a good solution for object avoidance control. The feasibility of the proposed obstacle avoidance method is shown by experiments using actual robots.

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This paper addresses a simplification method of wave propagation modeling for discontinuous structures by using experimentally identified or numerically computed reflection and transmission coefficients. In order to simplify the modeling of a discontinuous region of a waveguide, a modified spectral element method, which includes reflection and transmission coefficients in the spectral elements, was derived. Spectral elements except for discontinuity region may be theoretically modeled by the elementary theory of a continuous system. Whereas, spectral elements for discontinuity region are calculated by the proposed method using experimentally identified or numerically computed reflection and transmission coefficients. Wave analysis by the modified spectral element method was performed to show the validity of the modeling. The behavior of resultant waves showed good agreement with the frequency characteristic of reflection and transmission coefficients.

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This paper presents a task instruction system for picking up an indicated object in a complex environment. The basic setup of the system consists of a manipulator, a stereo camera, and a monitor. The task instruction scheme comprises the following four main steps: 1) The user indicates the target object on the camera image by a mouse click, and selects the object category and grasping form from a pop-up list. In this way, the system obtains information about the 3D position coordinates of the clicked point on the target object, the primitive shape of the object, and the task model for object picking with the selected grasping form. 2) The system acquires the information about the target object and constructs an environment model around the target by stereo vision using the information obtained from the task instruction. 3) The system finds a grasp point based on a grasp evaluation using the acquired information. 4) The robot performs picking up the indicated object. The features of the scheme are that the user can easily instruct the robot how to perform the object picking task by simple clicking operation, and the robot can pick up the indicated object placed in a complex environment without any previous knowledge of the target object.

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Brain-computer interface (BCI) is used to controls machines and devices by extracting neural information from human brain activity. BCI is expected to medical care as a rehabilitation system. In an earlier study developed an NIRS-BCI rehabilitation system. But , this study's detection method of brain activity is simple threshold. For this reason, it is difficult obtain highly accurate control operations. This study proposes a new brain activity detection method that uses separability and perseptron to achieve highly accurate on/off operations for rehabilitation system. Brain activity during actual grasping tasks and imagined grasping tasks are measured to demonstrate the validity of the proposed method. As a result, the proposed method of correct could be confirmed to have improved detection precision. In grasping task, the average correct rate by the proposed method improved 18.6 point compared with the conventional method. In imagined grasping task, the average correct rate by the proposed method improved 10.5 point compared with the conventional method. These results indicate that our proposed method enabled more accurate detection than conventional method. Results show that the proposed method is effective for detecting brain activity level.

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Paper curl causes paper jam or print quality degradation in electrophotographic printers and copiers. It is useful to predict amount of the paper curl in electrophotographic process for the efficient products development. The fusing process which is a sub-process of electrophotography is one of the causes of the paper curl. But it had been unclear how the paper curl was generated in the fusing process. In a previous study, a paper curl mechanism based on temperature gradient in paper heating was revealed. The mechanism shows that a temperature gradient causes moisture transfer from the high-temperature side to the low-temperature side within paper and consequently the moisture content of the low-temperature side becomes higher than that of the high-temperature side. This causes a shrinkage difference between both sides of the paper and thus the paper curl is generated. In this report, a one dimensional numerical model to simulate moisture transfer within paper is proposed. In this model, paper is treated as a uniform porous material and the moisture diffusion and transfer are treated according to Darcy's law, as well as evaporation during heating. The computer simulations are carried out to determine the moisture distribution within the paper when the surfaces are heated at different temperatures. The results are finally verified by measuring electrical resistance of papers. They are found to be in good agreement.

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In the 21^st century, as it is important to produce products with care for protecting the earth, a producer must be careful to conserve energy, save resources and reduce waste which pollutes environment. On the other hand, in case of a machine tool, much lubricating oil was used for smooth drive, electrical energy of forced cooling was used for high accuracy, and much cutting oil was also used for lubrication and cooling. This is large problem for protecting the earth. Therefore the soaking machine tool in strong alkaline water were developed and evaluated. Several elements of a machine tool were firstly investigated for alkali-proof. Then the bench lathe was remodeled and soaked in the vessel with strong alkaline water (pH12.5), thermal deformation between the spindle and the tool post was measured for evaluation of accuracy. And turning using the bench lathe was performed for investigating the effect of water evaporation in the strong alkaline water. It is concluded from the results that; (1) Alkali-proof regarding several elements of a machine tool were cleared in the experiment, (2) Thermal deformation of the bench lathe for bathing was very small in spite of no-forced cooling, (3) Accuracy of the machne tool was very good and the tool life was very long in spite of no-cutting oil, (4) The soaking machine tool in strong alkaline water was economical and eco-friendly.

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Various types of clean energy vehicles (CEVs) have been developed to reduce CO2 emissions and move our economies away from petroleum in the transportation sector. To make an innovation of these technologies and introduce them into the market effectively, it is important to analyze an optimal portfolio of CEVs, CO2 reduction effects and total social cost in the future that can be used as a decision-making guideline for governments and companies. Meanwhile, CEVs contain some metals that have supply risks because of the reserves and political availability. However, previous researches have not taken the metal resource problems into account. In this paper, we develop the optimization model by linear programming for CEV portfolios by 6 regions of the world, considering metal resource usage of CEVs. As a case study, under the definition that the objectives are minimizing total social cost or copper resource usage, and the constraint is CO2 emission reduction target, we clarify an optimal CEV portfolio of the world. In case of minimizing total social cost, electric vehicle and plug-in hybrid electric vehicle were mainly selected. On the other hand, in case of minimizing copper usage, fuel cell vehicle and clean diesel vehicle are selected. The optimal portfolio is different for both cases. Moreover, the relationship between CO2 emission target and copper usage to achieve is clarified. Finally, we evaluate copper resource constrains. When achieving 15% reduction of CO2, about 1.7 million ton of copper (approximately equal to 33 million units of EV) might be in short supply.

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The design theory of the previously proposed contact head slider was extended by considering the intermolecular adhesion force and thermally protruding head slider. The microwaviness-excited vibration characteristics of the thermally protruding head slider were analyzed by using the JKR adhesive contact theory. An important fact revealed is that, owing to the adhesive force, the excited frequency of the contacting slider are changed from zero to a value higher than the original second mode resonance frequency with an increase in the head penetration depth. This results in the successive appearance of the first and second pitch mode resonances. Because the friction force varies at the same frequency as the slider normal vibration, low frequency vibrations of the slider-suspension system has to be excited in the off-track and down-track directions. It is speculated that the large vibration with the first mode frequency commonly observed at moderate penetration depth is caused by internal resonance when the the resonance frequency of contact slider passes through the first mode frequency. It is suggested that the region of the head penetration depth for perfect contact sliding can be widened by increasing the contact damping and decreasing the microwaviness.

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The pitting damages at the tooth face sometimes occur on the transfer gears for the auxiliaries of the diesel engine through a short operation time even if the load of these gears is tiny compared with the main load of the engine. This phenomenon occurs regardless of the engine power from a few decade kW to a few ten thousand kW. According to the general design thinking, if the load is tiny, the size can be small and the manufacturing cost also can be low. But the above phenomenon does not represent this thinking and represent the necessity of a particular design guide for the tiny load gears. We reproduced this phenomenon by the simulator and also drew the original formulas by which we can calculate the manufacturing cost of the gear regardless of that size. When we changed the parameters of the gears, we checked the phenomenon change and also calculated the manufacturing cost. Then we drew one original design guide for the tiny load gears considering cost.

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This paper deals with development of a titanium boride grinding wheel. At first, a desired shape is made of titanium. Next, boron powder is spread on a surface of the titanium. The surface is scanned by a laser beam, and then titanium boride is produced on the surface of the titanium by the chemical reaction between the boron powder and the titanium. The produced titanium boride is used as a grinding wheel. Titanium substrates of plate shape are used in this paper for the experiments of producing titanium boride. The surface layers of the substrates are examined by an X-ray diffraction and titanium boride is detected in the layers. The cross sections of the layers are examined by an EPMA and EDS. Titanium boride is produced at the bottom of the groove those are generated by the laser scanning. Grinding experiments are performed using these grinding wheels. The results show that the sintered layer can be used for grinding of hardened die steel. The grinding wheel with small scanning interval of a laser beam can remove work material better and has small wear.

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In the early stage of the development of mechatronic systems, designers define system architecture as a set of subsystems and their interfaces in collaboration with domain experts across engineering domains. System architecture is crucial for designers and domain experts to understand the function of each subsystem within the context of overall function and clarify the design objectives of each subsystem and its constraints in relation with neighboring subsystems. This paper proposes a method to compose the structural hierarchy of a system along with functional system decomposition using the knowledge about physical phenomena, which are defined in terms of parameter relations across engineering domains. The method has been implemented on a CAD system for system architecting and demonstrated with a system architecting case of an air conditioner. The method helps systematically generate possible structural hierarchies of a mechatronic system.

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Mahalanobis-Taguchi (MT) method was applied to determining the first arrival time of acoustic emission (AE) waves in order to conduct waveform analyses without the experiences of experts. The recorded waveform was divided into the segments and that the Mahalanobis distances from the reference space consisting the back-ground noises to each segment were evaluated for identification. The appearance of the meaningful signal for the analysis could be found by searching the segment which firstly loses the similarity to the reference space. It was demonstrated that MT method could easily determine the arrival time which is coincident with the time obtained by visual observation based on the experiment using the simulated AE waves. It was found that MT method is effective to determine the arrival time of AE waves with high accuracy and robust against for configuration of the parameter in comparison with the voltage threshold method which has been generally used.

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[in Japanese]

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