Chatter vibration must be avoided to ensure the cutting accuracy in milling. Several studies have proposed analytical prediction methods for chatter stability based on a frequency-domain milling model and a modal analysis. However, the prediction accuracy is difficult to enhance because the modal parameters vary according to the spindle rotation and heat generation. In addition, necessity of special measurement devices for the modal analysis leads to high cost and complicated operations overwhelming the operator. In this paper, we propose a novel analytical method for identifying stable spindle rotations against chatter vibration in milling, which only requires once milling test without any measurement devices. Chatter frequency gradually gets larger with higher spindle rotation and drastically shifts at the stable spindle rotation, at which the locally largest depth of cut can be applied. Based on this characteristic of chatter frequency, the stable spindle rotations can be captured only from the servo information by decreasing spindle rotation continuously and observing frequency shifts with disturbance observer in the spindle control system. The disturbance observer is a technique to estimate the load torque only from the servo information, which is utilizable to monitor a fluctuation in cutting torque due to chatter. By applying time-frequency analysis to the estimated cutting torque, the drastic shift of chatter frequency can be captured. The experimental results show that the chatter frequency shift can be clearly captured at stable spindle rotations by applying a time-frequency domain analysis on the estimated disturbance torque.

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For additional functionality of artificial knee joint, the kinematics of knee has been evaluated using 2D/3D image registration technique after total knee arthroplasty. To evaluate the knee kinematics of implant, it is important how to adjust the ligament balancing around knee joint during surgery. In the kinematics evaluation of image matching, it is difficult to feed back the ligament balancing of knee because the information from image matching will be available after surgery only. Therefore, we developed a CT-based navigation system with the function of measurement of knee motion during surgery, which has been normally applied to enhance the accuracy of implant setting for target bone. The kinematics of knee has been evaluated with position of implant setting and ligament balancing which were obtained by this system during surgical operation. As a result, (1) The knee kinematics showed different trends between bone and implant based coordinate system, (2) Increasing 2mm thickness of insert between femoral and tibia component of artificial knee joint, the anterior-posterior shift of implant with knee flexion was decreased by changing the ligament tension around knee joint. In conclusion, it is possible to measure the knee kinematics with consideration of ligament balancing using the developed navigation system during surgery.

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The present paper describes the numerical results by the finite-element method of unstable phenomena of the spine induced by the growth of vertebral bodies in order to investigate the cause of the idiopathic scoliosis. In the previous study, through the linear buckling analysis using simple plate models, we confirmed the existence of the buckling phenomena, and made clear the region of geometrical parameters in which the buckling phenomena occur. These results support the buckling hypothesis as a cause of initiation of the idiopathic scoliosis. However, this theory is valid for infinitesimal deformation and is not applicable to estimate the stability for post-buckling behavior. In this study, we conduct post-buckling simulations caused by the growth of vertebral bodies considering the geometrical nonlinearity using the simple plate model and spine models with full width and half width. From the results, the existence of the non-linear buckling phenomena are confirmed in the simple plate model and the spine model with half width. Moreover, after the non-linear buckling phenomena, stable deformations are obtained excepting each one case in the simple plate model and the spine model with half width. However, the magnitudes of the post-buckling deformations are too small to explain the pathogenesis of the severe deformity observed in patients of idiopathic scoliosis.

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The research discussed in this paper proposed a control method that imparts equivalent friction to electronic power steering (EPS) systems in order to improve the steering feel. In order to impart friction stably, the proposed method uses motor torque rather than mechanical elements to impart friction. First, the effect of friction on the steering system was considered theoretically using simple harmonic motion models, and it was demonstrated theoretically that steering responsiveness could be increased by imparting appropriate friction force to the steering system. Based on the results of this analysis, a target value for equivalent friction force to be imparted by means of EPS control system was formulated. A method of linear approximation of the friction force necessary to realize equivalent friction force based on this target value was proposed. The method was applied in an actual vehicle, and the EPS system configuration necessary for the desired effect to be obtained was examined. It was considered that a system configuration incorporating a steering torque sensor with high torsional rigidity would be necessary, and a control method for imparting equivalent friction force was proposed. Finally, the effectiveness of the proposed method was verified in simulations using a vehicle model and in tests involving an actual vehicle. The vehicle model simulations demonstrated that the application of the proposed method increased steering responsiveness. The vehicle tests verified that the proposed method made it possible to obtain a stable steering feel, and was also effective in improving steering feel.

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Major sound sources remaining for Shinkansen, after the development and use of various noise reduction techniques, are the pantographs and bogies. Although aerodynamic sound generated from the bogies is highly influenced by air flow under the vehicle, velocity profiles under the vehicle on slab track have not been obtained since they are difficult to measure in field tests. In this study, we installed 8 simplified hot-wire anemometers on a slab track along the sleeper direction (at right angles to the direction of the rails) to measure time histories of velocity under vehicles. The ensemble averaged velocity for each type of rolling stock with different operation speeds clarified the characteristics of under-floor flow. The results and discussion are summarized as follows: (1) for series E5, the velocity at the track center, when non-dimensionalized with the train operational speed, is about 0.3 to 0.4, (2) for series E2, the velocity at the track center is about 0.4 to 0.5, which is 0.1 higher than that of series E5, (3) after increasing at the forward bogie section, the flow velocity decreases toward the rear section, again being driven up at the rear bogie section. This successive process, in which about a 0.1 increase is observed for series E2 and E5, is repeated with constant amplitude. This is probably because the channel of the flow under the vehicle, as it passes into the bogie section, immediately was enlarged which resulted in the decrease of velocity. These valuable results would be helpful not only for the aerodynamic sound evaluation but also for the validation of numerical simulations.

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Space structures encounter various severe environments in space. One of these environments is severe thermal condition where the difference of temperature during day-time and night-time is about 200 degrees Celsius. A signal level of radio wave from the Large Deployable Reflector (LDR) mounted on the Engineering Test Satellite-VIII (ETS-VIII) was observed to change during the Earth eclipse. This phenomenon was assumed to be caused by thermal deformation of the LDR. It was not a critical issue for the ETS-VIII because the communication beam from the LDR tended to spread in the wide range. However, highly accurate pinpoint communication beams are expected to be required in the future, and this transition of the beams may affect the performance of such satellites. Therefore, we tried to seek out the means to suppress the thermal deformation mechanically by focusing into the internal force generated at springs used to deploy the antenna. Furthermore, we simulated the thermal deformation behaviour in the original model of the antenna. According to the analyses in the single module model, the deformation at central side of upper radial member is almost suppressed by controlling the spring force if constraint conditions are pin and pin-roller constraint at center axis member. On the other hand, if the constraint condition is perfect constraint at longitudinal member, this means has no effect in suppression of the deformation at peripheral side of upper radial member, although the deformation at central side of it is almost suppressed. According to the thermal deformation analysis of the original model, deformation occurred towards normal direction of the reflector surface during thermal transition. Moreover, the midpoint of the LDR was confirmed to deform for about 5[mm] which explained the phenomena actually observed on the ETS-VIII.

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