The purpose of this research is to develop a high-performance face gear set for aircraft. The geometrical design method of the face gear has already been proposed, and how to decide an effective engagement area under the design parameter has been clarified. A numerical example is presented based on the proposed method. The designed modified-tooth was processed by the Multi-Tasking machine. Finally, running test was performed at a pinion rotating speed of 970 rpm. The face gear set can be operated continuously at an maximum load torque 1390 N•m, without any trouble. The transmission efficiency reached 98.9% under maximum load torque.

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The involute-cycloid composite tooth profile gear developed by the authors has some advantages against typical involute gear in tooth bending strength, surface durability, and power transmission efficiency. However, it is expected that the involute-cycloid composite tooth profile gear is sensitive to center distance error since this tooth profile includes cycloid part. In this study, we calculated the tooth root stress and tooth contact stress of involute-cycloid composite tooth profile spur gears with changing center distance and some design parameters which define the tooth profile. Then we have searched design parameters which reduce the influence of center distance error.

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This paper describes a study on the load bearing capacity of high density sintered metal gears with surface-densification. High density sintered metal gears were hobbed, and then surface-rolled. These gears were case-carburized after surface-rolling. The effect of surface-rolling on the surface property was examined by measuring porosities and hardness near surfaces of rolled gears. Running tests for these gears were performed, for the cases when these gears were used as a driver or follower. A failure mode and load bearing capacity of high density sintered metal gears and the effects of surface-rolling on the load bearing capacity of sintered metal gears were determined, and the results were compared with those of carburized wrought steel gears. The experimental results show that the load bearing capacity of high density sintered metal gear with surface-densification is comparable to that of a carburized wrought steel gear.

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This paper presents a study on effects of rim and web thicknesses on root stresses of thin-rimmed helical gears. Root stresses of thin-rimmed helical gears with symmetric web arrangement of various rim and web thicknesses, which were meshed with the solid helical gear, were measured from the beginning of engagement to the end of the engagement by the strain gauge method. The changes of the root stress from the beginning of engagement to the end of engagement were examined for the thin-rimmed helical gear with symmetric web arrangement. The meshing position (worst loading position), where the maximum root stress occurred, was determined for the thin-rimmed helical gear with symmetric web arrangement. The effects of rim and web thicknesses on the root stress, the maximum root stress and the position of the maximum root stress were clarified.

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In order to permit gear units to have higher performance; e.g., higher efficiency and lower driving noise level, an appropriate tooth contact pattern is required. The tooth contact pattern is affected by the stiffness of bearings, shafts and a gear case. Therefore, it is important in design process of gear units to evaluate the stiffness of these elements precisely. Stiffness of bearings is generally calculated using the method proposed by Harris. However, the stiffness of a tapered roller bearing subject to axial and radial load calculated by the method is different from the our measured one. Thus, the stiffness of tapered roller bearings under axial and radial load was analyzed and evaluated by using Tooth Flank Film Elements (TFFEs) for the contact problem. As a result, the change in calculated stiffness by TFFEs coincided with measured one especially in large displacement area. Furthermore, the appropriate bearing stiffness was obtained in consideration of the clearance between the inner and outer raceway and the deviation in the diameter of each tapered roller.

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Sidebands of mesh harmonic frequencies are considerable components in gear vibration spectrum. In this study, generation mechanism and characteristics of sidebands are investigated based on a single-degree-of-freedom vibration model of a cylindrical gear pair. Time-varying mesh stiffness and contribution of tooth surface form are formulated in the model. In addition to mesh harmonic components, the first order component of gear rotation is incorporated into each of the time-varying mesh stiffness and the tooth surface form as the effect of gear eccentricity. This model presents that the product of mesh harmonics and low order component of gear rotation frequency produces sidebands on either side of the mesh frequency. Asymmetrical property of sideband amplitudes about mesh frequency is dependent on frequency response function of gear vibration system. Vibration response curves of the sidebands have pseudo resonance peak. These sideband characteristics are verified by comparing simulation result of the gear model with experiment using a single-stage helical gearing.

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The carbon nitride (CNx) coating is one of the promising materials such as high wear proof, and superlow friction. It was reported that CNx coating showed superlow friction when it slid against a Si₃N₄ ball in N₂ environment. From the view point of industrial field, 1.0 μm thickness and 20 GPa hardness is necessary to CNx coating. We investigated the effect of substrate temperature, nitrogen ion beam acceleration voltage, deposition rate, and the thickness on its hardness. The CNx coating was synthesized on Si(100) substrate with 5 min of nitrogen ion beam sputtering before synthesis. The coating paramaters were -20, -5, and 15 °C of substrate cooling and without cooling, 0, 0.3, 0.5 and 1.0 kV of nitrogen ion beam acceralation voltage, 0.7 to 2.1 nm/s of deposition rate, and 500 and 1000 nm of thickness. After the synthesis, the coatings were analized by Auger Electron Spectroscopy (AES), Raman, and indentation hardness. As a result, N ion beam accelerate voltage, deposition rate, and thickness was not effective to the hardness of CNx coating. On the other hand, it was clear that the CNx coating hardness increased from 10 to 20 GPa with decreasing of substrate temperature. From the Raman analysis, I_D/I_G ratio and G peak position decreased with decreasing substrate temperature. These results indicated that sp³ structure which included in CNx coating increased, and then the hardness of itself increased.

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In tribology, a contact condition between mating surfaces is very important to reduce friction and raise their lifetime. Direct observation of apparent contact area is necessary for a better understanding of the contact condition. However, it takes a lot of measurement time to observe the whole apparent contact area with the existing contact microscope. Thus, another technique is required for a faster method to observe the real contact area. So, the laser microscope with a wide field of view we developed has been used to observe the whole apparent contact area for a very short time. A rubber disk specimen of a diameter of 5mm was pressed on a glass plate at several different loads and their contact areas were observed through the glass plate. The same contact areas were observed with the contact microscope. Both the measured results by two different methods were compared with each other. It was found that they were similar with each other. Considerably wide apparent contact area between a platen rubber roller and the glass plate was observed with the laser microscope with a wide field of view. The distribution of real contact ratios and micro-slips on the contact area were obtained. A Relationship between the real contact ratios and the micro-slips on the contact area was discussed.

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A porous vacuum chuck has an advantage that the flatness of an object held by this kind of chuck is superior to that by other types of vacuum chucks with vacuum holes or circumferential vacuum grooves. This is because porous material has through holes with micron-meter order diameter over a chuck surface. In addition, it is reported that a surface-restricted layer which has lower permeability than the bulk of the porous material can improve the holding characteristics, especially in the case of holding an object with smaller diameter than a porous chuck diameter. However, forming the surface-restricted layer is somewhat troublesome work. In addition, when a porous chuck is applied to machine tools, cutting fluid infiltrates a porous chuck and a holding force is decreased. Moreover, in cutting materials, a cutter also cuts the chuck surface and, accordingly, an air permeable sheet is usually inserted between an object and a chuck surfaces. Therefore, this paper proposes to use a water-impermeable porous film with 0.3 μm diameter holes as the surface restricted layer and the permeable sheet to overcome the above problems. The vertical and lateral holding forces are clarified numerically and experimentally. It was found that a water-impermeable porous film can easily form the surface-restricted layer for vacuum chucks and make it possible for vacuum chucks to apply to machine tools using cutting water.

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A spherical stepping motor based on a truncated octahedron and a regular dodecahedron is proposed. At first, the advantages of general spherical motor are presented. Next, a principle of a conventional stepping motor is expanded to the three dimensional space and a principle of a spherical stepping motor based on a truncated octahedron and a regular dodecahedron is proposed. Then, the proposed spherical stepping motor is designed. The rotor diameter, total mass of the permanent magnets, and the total ampere-turns of the motor are designed to be the same as the developed spherical motor based on a hexahedron and an octahedron. Static torque and the no-load movement of the designed motor are simulated. From the simulation results, the static torque of the motor will be the same as that of the developed spherical motor based on a hexahedron and an octahedron. The no-load torque fluctuations are less than that of the developed spherical motor. The proposed motor will be a high-torque, high-performance spherical motor.

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Research and development of micro-fluidic systems, such as μ-TAS (Micro-Total Analysis Systems) and micro reactor system, has recently become active in the fields of chemical engineering and biotechnology. Micro pumps are an essential element in the realizing of micro-fluidic systems. Therefore, in this research, a micro linear pump has been developed as a micro pump incorporated into micro-fluidic systems. The full length and diameter of the micro linear pump are 32.5 mm and 6 mm, respectively. The performances of micro pump depend largely on micro check valve. In this report, then, micro check valves having steric microstructure were developed through micro rubber fabrication for improving the micro linear pump. The micro rubber fabrication is a process integrated the finite element method (FEM) analysis, the precise die using a fine NC milling machine, the silicone rubber molding and the excimer laser junction. Thus far, most kind of micro check valves have planar structure. Having steric microstructure, however, the developed micro check valves have higher performances than conventional flat type micro check valves and work as check valve without the structure in the surrounding. This paper details the structure and performances of the developed micro check valves, as well as application test to the micro linear pump.

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For the purpose of reduction of the electric power consumption during expansion of a giant magnetostrictive actuator (GMA), the authors developed the power-saving drive GMA, and showed its good power-saving performance. However, due to its drive principle, the developed GMA has a problem that instantaneous excessive expansion appears at the beginning and end of the GMA expanding. For the reduction of the excessive expansion, this paper clarifies the cause of the excessive expansion and presents the modified actuator construction. In order to prevent the giant magnetostrictive material (GMM) from being magnetized by the external magnetic field generated by the coil, the coil in the GMA is divided into two coils, and each coil is placed inside and outside of the permanent magnet. With the two coils, this paper presents two types of improved power-saving drive method. One is to counterbalance the magnetic field in the GMM actively by the magnetic fields of the coils which counter each other. The other is to actively prevent the instantaneously changing magnetic field from penetrating the GMM by the inductance of the short-circuited coil. The evaluation of performance of those methods has been carried out. It has been confirmed that both the methods are effective to reduce the instantaneous excessive expansion.

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In the fundamental configuration of a giant-magnetostrictive actuator (GMA), a giant-magnetostrictive material (GMM) rod is energized by a coil surrounding it. Continuous electric power supply to the coil is necessary to maintain the expansion of the GMA. However, the electric energy consumption is in proportion to the activation interval of the GMA and becomes larger especially for applications to maintain their expansion in long interval. In order to reduce the electric power consumption during the GMA expanding, this paper presents a new drive method of the GMA which can waste no electric power during GMA expanding. This proposed method utilizes the magnetization/demagnetization characteristics of interior permanent magnets of the GMA to magnetize the GMM during its expansion. But the motion control of developed GMA was restricted only in the 2-position control. Furthermore, this paper also presents the modified power-saving drive method which can give the function of continuously positioning between the 2 positions to the GMA.

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UV lithography has been used in most case of microstructure patterning. However, it is difficult to form a fine rectangular microstructure in the thin film at a small width. On the other hand, silicon dry etching technology makes it possible to fabricate rectangular structures by repeating two steps of etching process and protection process. Then, we introduce the ability of Si dry etching technology in order fabricate un-tapered, high precision Au microstructures containing rectangular patterns in order to fabricate Au microstructures. Au electroforming was realized from the bottom of the Si microstructure groove. We succeeded in forming about 4 μm thick, void-free Au film in a space as narrow as 2.6 μm in large effective area of 60 mm squares on 4 inch Si wafer. Therefore, it is expected to be used in the production of a wide variety of devices that have not yer been put into practice.

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A walking assistance device using a flexible shaft was developed. A combination of the flexible shaft with a worm gear was successfully adopted on this device to modify its appearance simple and its size compact. This device is controlled with a hybrid-control system both torque and angle at ankle and knee joints. In this system, the torsional spring constant of the flexible shaft is taken into account to the control power and the rotating angle of the motor. To expand the area of where an equipped parson can walk with the device, a self-contained system that controlled with SH-4 microcomputer and actuators, which consisted of motors and gears, were put in the small backpack, and Lithium-ion battery was utilized. Therefore, the equipped parson and patient can freely walk both in and out of doors environment.

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An apparatus to assist elderly patients to stand up, as well as leaning forward the upper body, has been developed. The mechanism of the apparatus enables to shift the person's center of gravity along an adequate trajectory during the standing up process, so as not to cause strain on the joints of the user's leg. The apparatus also assists a person to alter from standing or sitting posture to lying posture. Although the mechanism has multiple links and joints, only one actuator is required to transform the apparatus between aforementioned three postures. The length of each link of the mechanism has been determined from their effect on the backrest angle when each link in the mechanism length is changed. The torque of the hip and knee joints while using the apparatus can be calculated and compared with the data of a user not using the apparatus. We hypothesize that the output torque of the user while standing is decreased by using the apparatus.

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Large-sized spiral bevel gears in a Klingelnberg cyclo-palloid system are manufactured using multi-tasking machine tool with five axis control. This manufacturing method has some advantages that realize arbitrarily modification of tooth surface and machining of the part except tooth surface. The pitch circular diameter of the gear treated in this study is more than 1,000 mm. For this study, first the numerical coordinates on the tooth surfaces of the spiral bevel gears are calculated and the tooth profiles are modeled using a 3D-CAD system. Afterwards, the large-sized spiral bevel gears were manufactured based on a CAM process using multi-axis control and multi-tasking machine tool. After rough cutting, the workpiece was heat-treated and it was finished by a swarf cutting using a radius end mill. The real tooth surfaces were measured using a coordinate measuring machine and the tooth flank form errors were detected using the measured coordinates. Moreover, the gears were meshed each other and the tooth contact patterns were investigated. As a result, the validity of this manufacturing method was confirmed.

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This study has proposed a method of frictional reduction and lubricity improvement for meshed gears, which is based on ultrasonic oscillation. This report describes gear and shaft design using the finite element analysis (FEA), and results of experiments using an ultrasonic actuator. First, the FEA calculated axial and radial amplitude of vibration on the shaft and gear surfaces. A modified gear profile improved the axial amplitude by 50 % as keeping the radial amplitude low. Next, a manufactured gear thermally-inserted to a shaft was oscillated by an ultrasonic transducer excited by two types of driving amplifiers. Measurement with laser Doppler vibrometer demonstrated that the axial and radial amplitudes of vibration were 1.3 μm(p-p) and 0.49 μm(p-p), respectively.

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In a traditional turbine-generator set, rotor shaft designers and blade designers have their own models and design process which neglects the coupled effect. Since longer blade systems have recently been employed for advanced turbine sets to get higher output and efficiency, additional consideration is required concerning rotor bending vibrations coupled with a one-nodal (k=1) blade system. Rotor-blade coupled bending conditions generally include two types so that the parallel and tilting modes of the shaft vibrations are respectively coupled with in-plane and out-of-plane modes of blade vibrations with a one-nodal diameter (k=1). In this paper, we propose a method to calculate the natural frequency of a shaft blade coupled system. According to our modeling technique, a certain blade mode is reduced to a single mass system, which is connected to the displacement and angle motions of the shaft. The former motion is modeled by the m-k system to be equivalent to the blade on the rotating coordinate. The latter motion is commonly modeled in discrete form using the beam FEM on an inertia coordinate. Eigenvalues of the hybrid system covering both coordinates provide the natural frequency of the coupled system. In order to solve the eigenfrequencies of the coupled system, we use a tracking solver based on sliding mode control. An eight-blade system attached to a cantilever bar is used for an example to calculate a coupled vibration with a one-nodal diameter between the blade and shaft.

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In this paper we revisit the PID control design in terms of descriptor expression. Based on the descriptor expression of the derivative action in the PID controller, we consider PID control design utilizing standard nonlinear optimal control problem. Therefore, although the resultant control problem includes mixed constraint conditions with states and inputs, the real time optimization tool (MPC, for instance) can be applicable as one of the most powerful methods for tuning of PID parameters. Finally, some simulations are given to illustrate the effectiveness of the proposed approach.

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This paper deals with active noise control (ANC) using an acoustic wave reflection of a parametric array loudspeaker (PAL). Making use of the strong directivity of a sound radiation a PAL has, it is possible to avoid spillover phenomenon leading to the augmentation of sound pressure in other region of the targeted control point. The strong directivity, however, may be double-edged for ANC. If an obstacle exists between a PAL and a target control point, it may no longer achieve ANC as a sound diffraction cannot be expected. To overcome this problem, this paper presents a control strategy based upon the use of a sound reflection, and hence the sound beam of a PAL may detour the obstacle, arriving at the control point. First, fundamental properties of a sound beam reflection are investigated, thereby assuring the possibility of a sound reflection for ANC. Furthermore, mathematical description of a sound beam is performed using a mirror image method, control effect of ANC being clarified. Finally, an experiment is conducted, demonstrating the validity of the proposed method.

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An automatically performing bell system, which informed the specified time with music, has many types of bell configuration and arrangement. The first requirement for the bell system is to tune the fundamental resonance frequencies of each bell to an equal temperament of scale. Finite Element Method (FEM) was used to determine the natural frequency of the bell and the effect of bell profile such as thickness and diameter on the natural frequencies was analyzed. Experimental evaluation was also carried out to examine the natural frequencies and mode shapes of the similar profile bell series and constant thickness bell series. The tuning algorithm of the fundamental and higher mode frequencies by changing the inner profile of the bell to improve the sound quality was developed using FEM successive calculation and its availability was discussed. Moreover, the acoustic radiation properties of the vibrating bell were examined by use of the Boundary Element Method.

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A new torque cancelling system that stabilizes mechanical sway against quick, rotational motion is discussed in this paper. The torque cancelling system (TCS) cancels the reaction moment generated by the rotational motion of an object by considering the precise dynamics of the object and the body of the robot itself. The reaction moment can be obtained accurately using the parallel solution scheme of inverse dynamics that handles the dynamics of complex robotic architectures by modeling them with finite elements. Once the reaction moment is known, it can be cancelled by applying an anti-torque to a torque-generating device. In this paper, an outline of the parallel solution scheme is first described. Then, some examples of torque cancelling resulting from accurate calculations of dynamics are demonstrated by showing the experimental results carried out on simple systems. The systems used in the experiments include rigid and flexible outboard and inboard objects, where difficult assumptions are normally required to consider the dynamics accurately. A numerical example of a complex robotic architecture is also presented to verify the use of the system.

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A general-purpose solution scheme of inverse dynamics for link systems called the parallel solution scheme, was developed on the basis of a finite element approach. It can be applied to dynamics compensation of different types of configurations such as open-loop, closed-loop, or multibranch link systems, and can also deal with elastic deformations of constituted links without the need to revise any part of the scheme. The main objective of this study is to extend the use of the scheme to dynamics compensation of underactuated link systems, and to obtain highly stable feedforward control of those systems by feeding the calculated torque. A solution scheme of kinematics with updated transformation algorithm is also developed on the basis of the finite element approach, in order to calculate target motions of the systems including passive joints and flexible links. The feedforward control experiments of several underactuated link systems are carried out, and the validity of the dynamics compensation is confirmed.

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This paper proposes design procedures for output synchronization problems where each plant is subject to control magnitude constraints. To motivate the present control design problem, we first show that an existing output synchronization control law, which modifies primal reference inputs to obtain better output synchronizations, provides adequate synchronization performance, however, it tends to be high gain controls and becomes difficult for practical implementations due to well known input saturation phenomena and resulting serious performance deterioration. To overcome the problem, we propose output synchronization and Reference Governor combined control systems design procedures. Effectiveness of the proposed methods is validated through experimental evaluations.

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This paper describes a front-steering assist control system design for a motorcycle taking into account of nonlinearity of tire cornering forces. Utilizing hyperbolic tangent functions to approximate Magic Formula tire forces, the rider-motorcycle system model can be linearized around an equilibrium point of steady-state circular turning. From the view points of eigenvalues and frequency responses, the linearized model is analyzed and a reduced-order model is obtained to design the control system by using H_∞ control theory. By carrying out the steady-state circular turning simulation in the low road friction condition, it is demonstrated that the control system can stabilize a motorcycle when receiving a sudden disturbance from the front wheel.

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The topology optimization method is the most flexible optimization method that allows both shape and topological changes during the optimization process. However, due to its high flexibility, the utility of topology optimization results is often spoiled by a preponderance of impractical designs that are difficult or impossible to manufacture, such as structures with numerous extremely thin members and tiny holes. This paper proposes a new structural optimization methodology that reduces the number of design variables in a multiple phase projection method, which advantageously reduces computational time and benefits manufacturability. The multiple phase projection method is a geometrical contraint method that imposes a minimum length scale on both solid and void phases. Normally, two design variables are associated with each of these phases at each node in the finite element analysis, resulting in an undesirable increase in the number of design variables. To mitigate this problem, we develop a new methodology that requires only one design variable at each node. An optimum design example for a minimum compliance problem is provided to confirm that the new methodology provides reasonable solutions that achieve the given minimum length scale using a reduced number of design variables.

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The head positioning accuracy of the hard disk drive should be improved to meet today's increasing performance demands. Vibration suppression of the arm in the hard disk drive is very useful to enhance the servo bandwidth of the head positioning system. In this study, the smart structure is introduced into the hard disk drive to suppress the vibration. First, the proof-mass actuator and the tabular PZT actuator are designed, and then the experimental set-up of the smart head actuator is developed by installing the actuators for vibration control on the objective head actuator. Second, the state-space modeling of the system is conducted by system identification approach in the experimental modal analysis for control system design. Next, the vibration controller is obtained by conducting the H_∞ control problem. Finally, the closed-loop performance is evaluated by simulation and experiment.

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This paper describes a method of estimating the amount of swelling in rollers under working conditions, such as high load pressures, high rotation speeds, high temperatures, and slippage occurring between paired rollers. Three kinds of swelling test system were considered. “Rotation tests” refer to swelling tests inside the actual environment of the machine. A pair of rollers rotates under conditions of load pressure, high temperature and slippage (difference in rotation speed). “Static tests” are similar to the traditional swelling test where the roller is free from speed, slip and load. “Quasi-static tests” is similar to Static tests but load pressure can be applied. The Experiments were efficiently conducted with these three systems by using DOE (design of experiments). As a result, rotation speed, slippage and load pressure (within the usual range in ATM) had small effects, whereas, environmental temperature, total contact time, application quantity and application frequency had large effects on roller radius. Accelerated test method was examined and finally, the maximum amount of swelling in the roller under the actual conditions inside the machines can be predicted using the regression curve analyzed from 3 experimental points by the “static test”, and the method provides a swelling test that is completed within one day.

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A new hybrid type magnetic bearings using flux concentrated permanent magnet arrangement is proposed in this paper. Also a new axial bearing rotor disc is proposed which has similar diameter with the other rotor parts for easy manufacturing and maintenance. This flux concentrated bias PMs are designed using ferrite PMs which are low cost and unlimited resources. Structure and operating principle of the proposed magnetic bearings are introduced. Then they are designed using FEM analysis. The experimental setup is fabricated and tested. The static tests showed relatively strong attractive force with low cost PMs. The levitation and rotating tests were stable with good characteristics.

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This paper shows the effect of angular spring and angular damping coefficients of oil film on the stability characteristics of an elastic rotor supported in circular journal bearings. A theoretical Jeffcott rotor model considering the angular spring and angular damping coefficients are constructed, and stability threshold speeds and stability margin were calculated under wide operating conditions. Comparing to the model neglecting the angular spring and angular damping coefficients, the angular spring and angular damping coefficients do not affect on the stability of the rotor-bearing system when the stiffness of the rotating shaft is high. On the other hand, when the shaft is very flexible, Sommerfeld number at the stability threshold speed increases, indicating the angular spring and angular damping coefficients improve the stability of the rotor-bearing system.

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This paper shows the stability characteristics of a flexible rotor supported in three types of multi-lobe bearings, i.e. 2-lobe bearings, 3-lobe bearings and 4-lobe bearings, and tilting pad journal bearings theoretically. Angular spring and angular damping coefficients of oil film of the bearings are calculated and the effects of the preload factor on the coefficients are discussed. With a Jeffcott rotor model considering the angular spring and angular damping coefficients, stability charts are made under the wide range of operating conditions, and show that 2-lobe bearings with a high preload factor cover much larger stable region in the stability charts than the other bearings, and 3-lobe bearings, 4-lobe bearings and tilting pad journal bearings with line contact pivots do not have special advantages in comparison with 2-lobe bearings. From the results, it is concluded that 2-lobe bearings with a high preload factor are most suitable for supporting the flexible rotor.

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The perception models which explain perceived lengths of objects by static holding have two assumptions. One is strict rest of objects and the other is small fluctuation of them. In this paper, we measured the fluctuation of objects by using a 6 DOF (degrees of freedom) tracking system. It made clear firstly that the objects were certainly fluctuating. Secondly, the fluctuation was divided into the initial part just after the start of holding and the steady part after that. Thirdly, the fluctuation of the initial part was bigger than that of the steady part, but much smaller than that of wielded objects. We considered a muscle torque model, MTM, which consisted of a static moment and an inertia moment. The relation between angular acceleration and the coefficients of the MTM showed that subjects perceived lengths depending on dynamic characteristics of objects so much as angular acceleration increased.

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This paper describes a basic research on the method for presenting haptic texture sensation in a three dimensional space. A vibratory pin-array display for tactile stimulation was attached to the Phantom force display to provide surface information of an object in addition to its shape to the user. The haptic presentation of textures on the surface of an icosahedron was evaluated by three-stage discrimination experiments. A basic discrimination of difference between visual and haptic renderings was almost perfectly answered while more intricate textures lowered the correct answer ratio to around seventy percent. The discrimination of stripe, mesh and melon-rind textures was not very easy even with a visual guidance since in part strictly accurate motion of a finger to pick up the salient feature of the textures was not possible. Without visual guidance the haptic exploration produced over fifty percent correct answer to textures with very similar features, while the chance rate was twenty-five percent. These results, although limited, demonstrated that the very small difference in texture features was properly presented to the users. The authors consider that tactile presentation of textures increased the sensation of reality greatly as compared to the force sensation via the stylus of a force display conventionally used in the field.

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Braille is one of the few writing systems that use tactile perception. The system is widely used by the blind to read and write. However, Braille is difficult to learn for persons with acquired blindness, especially for the elderly. Therefore, the aim of the present study was to design a tactile Japanese Katakana presentation device for the investigation of characteristics of tactile Katakana recognition. The device consists of a disk for tactile Katakana patterns, a force sensor unit for force measurement when subjects' fingers touch the tactile patterns, and an ultrasonic motor for tactile patterns presentation. Using the ultrasonic motor, the device presents characters to subjects quickly and automatically. Furthermore, the device has a big advantage that subjects are only required to move their fingers up and down, without any big submovements. An experiment was conducted using the device to test tactile recognition of 46 Katakana characters in native Japanese speakers with normal vision. Ten healthy right-handed male volunteers consented to participate in this experiment. Successful tactile Katakana recognition was higher than 78% (±14.4%) for these young subjects.

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This study describes the use of a novel orthosis in individuals with restricted upper limb movement owing to decreased muscular strength. In such individuals, it would be effective to neutralize the influence of gravity so that they can freely move and hold their arms. Hence, we developed a novel orthosis that compensates for each joint moment. An auxiliary method of the orthosis involves weight compensation mechanisms that constitute only a spring, wire, and pulley, because assisting methods that involve electricity are disliked by users. Our novel orthosis has two advantages compared with the conventional orthoses: (1) it allows the use of the subject's arms in a wide range of motion and (2) external forces do not hinder upper limb motion because the auxiliary function make the upper limbs feel lighter. Therefore, there is negligible discomfort and skin irritation with the long-term use of this orthosis. We evaluated the effect of assisting muscular strength by applying our orthosis in healthy male subjects. Surface electromyogram measurements in the deltoid and trapezius muscles revealed remarkable reduction of muscular activity, which is necessary for improvement in upper limb motion. In conclusion, the novel orthosis enabled stress-free upper limb motion by means of a weight compensation mechanism.

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As a model for putting a shot, we employ a release model with three degrees of freedom which model includes three parameters: a shot putting speed, a release angle and a horizontal speed of the shot putter's body. The three DOF model provides the explicit solution of the optimum release angle with the model parameters, and the solution is used for estimating the value of the model parameters from measured data. Under the assumption that shot putters release a shot at their optimum angles, the speeds of putting a shot and the body are estimated. The result shows the distinct negative correlation between these speeds. Also, we attempt to clarify the difference between the glide and rotational techniques which are popular throwing techniques in shot put. It is found that the distribution of the body speed and the optimum putting angle depend on the throwing techniques, and this result suggests that the three DOF release model explains the difference between the throwing techniques from the standpoint in mechanics.

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Non-invasive measurement of the arterial pulse wave can be carried out by means of an optical sensor placed at the center of the artery. In our previous study, we suggested an artery searching method on the basis of this inversion phenomenon that a dicrotic wave and a percussion wave of reflection photoplethysmography (PPG) with wavelength 530 nm and 810 nm were turned over at moving the reflection-type optical sensors on the inner side of the wrist. However, the contact state of optical sensors at the detection of arteries and accuracy validation of an artery searching method are not clarified. The purpose of the present study is to investigate the suitable measurement conditions of optical sensors for an artery searching method and to elucidate on the accuracy of this method. In this study, we investigate the suitable measurement conditions of optical sensors by measuring the pulse wave by using the reflection-type optical sensor and by numerical analysis of light propagation and examined an artery searching method by the measurement in the wrists of 5 subjects. Our results indicate that a no pressure should be exerted at a wavelength of 530 nm. On the contrary, pressure should be exerted at a wavelength of 810 nm in order to obtain more accurate the detection of arteries. From the measurement of 5 subjects, the accuracy of our proposed method is 0.78 mm at these measurement condition. In conclusion, we propose that reflection PPG at wavelengths 530 nm and 810 nm can be performed for an artery searching method.

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Swarm robotics is the research field of multi-robot systems which consist of many homogeneous autonomous robots without any type of global controllers. Generally, since a task given to this system can not be achieved by a single autonomous robot, emergent cooperative behavior is expected in a robot swarm by a certain mechanism through the interactions among the robots or with an environment. In this paper, an evolutionary robotics approach, i.e., the method that the robot controllers are designed by evolutionary algorithms with artificial neural networks, is applied. Among many approaches to evolving artificial neural networks, two approaches, NEAT and MBEANN, are adopted for computer simulations. Although a conventional neural network evolves only synaptic weights with the condition of a fixed topology, NEAT and MBEANN evolve not only their synaptic weights but also their topologies. As a benchmark of swarm robotics, cooperative package pushing problems by ten autonomous robots are conducted to examine their performance. The emerged behavioral characteristics are discussed.

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To compare the sitting balance capabilities of healthy young women with those of women with idiopathic scoliosis, we performed experiments using a system for evaluating dynamic sitting balance. The system comprised a three-dimensional position and orientation sensor for measuring the upper body joint angle, a stabilometer for measuring the center of pressure (COP) trajectory and seat reaction force, and a six-degree-of-freedom platform for producing seat perturbation. The seat reaction force and joint angle of the upper body were used to calculate the joint torque of the 5th lumbar and 12th thoracic vertebra. During the experiments, 13 control subjects and 21 women with idiopathic scoliosis tried to maintain a sitting posture relative to the seat perturbation (0.25 Hz and 0.5 Hz, 5 deg amplitude). For seat perturbation of 0.5 Hz, the root mean square, mean velocity along the trajectory, and excursion area (COP parameters), and the joint torque of the 12th thoracic vertebra in women with idiopathic scoliosis were significantly higher than those in the control subjects. Results suggest that the dynamic sitting balance ability of women with idiopathic scoliosis is inferior and that a large physical load is necessary for them to maintain a sitting posture.

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Life style related diseases such as hypertension and diabetes promote arteriosclerosis which causes circulatory diseases. It is important to evaluate arterial condition for prevention of circulatory diseases. The pulse wave velocity method has become familiar as a vascular test because it is easy and non-invasively. However, the accuracy of the method seems not to be high because it just compares two points ignoring the frequency dependence and reflection waves from peripheral vessels. In this study theory of pulse wave propagation considering such effects was formulated. A new method to identify the reflection ratio from peripheral vessels and pulse wave velocity was proposed. This method was verified by experiment using a silicon tube and applied to measure the pulse wave propagation of human arm as a case study. The results showed that this method has possibility to apply to measure the pulse wave propagation of human pulse wave.

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A surveillance system is required to gather the suffering information in the stricken area safely after large-scale disasters. An autonomous blimp is the best option for this purpose. This paper proposes a control design method for automatic takeoff and landing of outdoor blimp robots. The control method consists of stabilizing control in horizontal plane and longitudinal control for altitude and pitching motion of the blimp. The states of the kinematic model which is used to design a time-varying stabilizing controller in horizontal plane are transformed considering blimp motion property. Some simulations and experiments are performed to confirm the usefulness of the proposed method by using an outdoor blimp whose length is 12m.

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This paper considers control design problems that can reduce a throughput time of total task of a robotic manipulator which is used in handling silicon semiconductor wafers. We propose an algorithm for discontinuous switchings between translatory and rotational motions. We derive the motion switching algorithm by utilizing an invariant set of the rotational dynamics. The effectiveness of the proposed algorithm is evaluated though experimental studies.

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This paper discusses the development of the interpretation system for the mobile robot manipulation which maps linguistic command with vague expression issued by a human operator to an appropriate quantity. The system allows the operator to use only few kinds of vague expressions, as can be seen in the case when a human instructs some other person orally. The problem here is to find an appropriate quantity for each operator because the quantity corresponding to the vague word which is implied by the operator differs when operator changes. To cope with the difficulty, this paper proposes the distance type fuzzy reasoning algorithm with iterative learning scheme that can accommodate individual difference on how to quantify the vague expression. The experiment has been carried out to examine the change in the number of instructions required to guide the mobile robot to destination. The result of the experiment shows that the number of instructions necessary for achieving the guidance task decreases in almost all cases, which implies the validity of the proposed system.

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The present paper proposes a novel grasp configuration planning for a robotic hand to achieve a specified task with high manipulation accuracy against unknown disturbances. In precision tasks such as a peg-in-hole insertion or a manipulation with a tool, manipulation accuracy of the task coordinate on the grasped target is important. We verify that the effects of unknown disturbances on manipulation task accuracy depend upon the singular vectors and condition number of the manipulation system. It is shown that the manipulation task accuracy can be controlled by changing the grasp configuration appropriately. Then a grasp configuration planning method for precise grasp is proposed by using the above-mentioned measures. The usefulness of the proposed method is shown by simulations concerning a peg-in-hole insertion task.

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A real-time collision-avoidance algorithm for human-symbiotic robot that is required to avoid multiple pedestrians was developed. An algorithm to predict the likelihood of a collision with obstacles was based on the relative velocities between a moving robot and multiple obstacles. An algorithm that can generate the optimum path sequence to a goal in real time was also developed. The collision-avoidance path is generated by repeating an operation to select two tangent paths that connect a via-point on a path to a collision circle of each obstacle that exists in the relative space. A robot—called “EMIEW”—using these algorithms with a system for avoiding collisions with many obstacles moves at a speed of 0.8 m/s in a cluster of five people walking at 1.2 m/s - speed. The repeat period for generating a new avoidance path is 0.5s, and the processing time for the developed algorithm in the each period is less than 4 ms.

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This paper presents the method of autonomous voice acquisition for a talking robot by applying a dual-SOM. We have so far developed the talking robot, which has mechanical organs as a human. By applying an auditory feedback control, the robot autonomously learns the vocalization skill. For the autonomous learning method, a Self Organizing Neural Network (SONN) by combining a Self-Organizing Map (SOM) with a Neural Network (NN) was employed. The SONN had 2-dimensional mapping space, which was used to locate phonetic features of voices generated by the robot. By choosing cells on the map, voice articulations were autonomously recreated. However, due to the spatial restriction of the map, the voice transition from one vocal sound to another was not always recreated properly. To solve the problems, a dual-SOM, the combination of a phonetic-SOM and a motor-SOM, both of which have 3 dimensional mapping spaces, is introduced. The structure of the dual-SOM is firstly described, and then acquired vocal sounds are evaluated, together with the analysis of the behavior of the SOM.

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The aim of this study was to examine impacts of cell phone conversation and operation on the driving performance. Ten male students participated in following two experiments: one is to examine the effect of cell phone conversation on driving performance, and the other is to examine the effect of cell phone operation while driving. In the former experiment, the subjects performed No-task and conversation (cognitive tasks) with hands-free (HF) and hand-held (HH) cell phone while driving in city traffic in which the maximum speed limit is 40 km/h. In the latter experiment, they were instructed to operate (dialing or talking) HH and HF such as touch screen, earphone, and voice recognition while driving. We measured driving performance, heart rate, eye tracking, and NASA-TLX. The results were as follows: (1) Regardless of phone type, cell phone conversation while driving increased the drivers' psychophysiological stress and also had negative impacts on the driving performance. (2) Break reaction time in response to pop-up event was significantly slower in operation of both HH and all hands-free kits than in No-task. The results suggest that using all hands-free cell phone while driving is not safer than hand-held cell phone or driving without a cell phone; inattentional blindness itself may be a risk factor for traffic accidents.

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