The microcontact printing (µ CP) is a well-established method to pattern a material of interest using an elastomeric stamp. We have developed two techniques which assist the µ CP-based cell-patterning for the controlled growth guidance of cultured neuronal cells on substrates. (i) Contact-transfer of extracellular matrix (ECM) protein on a microelectrode array substrate was achieved by spatially designing the microstamp to allow printing proteins even on the surface having uneven structures, and the differentiated PC12cells showed selective adhesion and growth in the pre-determined locations on the electrode array. (ii) Cell alignment onto the pre-patterned ECM protein was also succeeded by using the microstructured silicon wafer having a band array of microholes, and the placed PC12cells extended their axons along the protein pattern. These researches were carried out with the objective to developing a cell-based device based on a cellular network.

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Stress fiber is a bundle of actin filaments, which also contains myosin and cross-linking proteins. It remains unclear how stress fibers are formed from their main components, actin and myosin. To address this question we examined the process of formation of stress fibers in a model system, a semi-intact cell. Fibroblasts were treated with a Rho kinase inhibitor to disorganize stress fibers. These cells were permeabilized and used as semi-intact cells in this study. When these cells were treated with ATP and Ca²⁺, stress fibers were restored within 15min. Motion analysis of actin filaments labeled with quantum dots during formation of stress fibers revealed actin filaments were gradually assembled while they were moving toward the center of the cell. This suggests that ATP-driven tension influences the stress fiber formation. The ATP-driven tension was mimicked in this study by artificial centripetal traction force, which was carried out by dragging the micropipette attached on the cell surface. Stress fibers were formed by the traction force application. These results suggest that tension in actomyosin meshwork is an important element in stress fiber formation.

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Outer hair cells (OHCs) in mammals can elongate and contract at frequencies up to 100kHz in response to changes in their membrane potential. The origin of this unique motility is the motor protein prestin, which is densely packed in the lateral membrane of the OHCs. In a previous work, we constructed a prestin-expressing cell line using Chinese hamster ovary (CHO) cells to obtain a stable supply of prestin. When we research prestin using constructed cells, it is necessary to estimate the expression level of prestin in the cells easily and non-invasively. As the prestin gene and a green fluorescent protein (GFP) gene were introduced into constructed cells using the same vector, the expression level of prestin and fluorescence intensity of GFP are possibly correlated. Since this correlation is not clear, however, in this study, we therefore investigated whether the expression level of prestin evaluated by patch-clamp recording and the fluorescence intensity of GFP obtained from fluorescence images are correlated or not. As a result, it was demonstrated that they were correlated. The expression level of prestin can therefore be evaluated by measuring the fluorescence intensity of GFP.

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Endothelial cells (ECs) that line the inner surface of blood vessels are barriers to the transport of various substances into or from vessel walls, and are continuously exposed to shear stress induced by blood flow in vivo. Shear stress affects the cytoskeleton (e.g., microtubules, microfilaments, intermediate filaments), and affects the transport of macromolecules. Here, the relationship between the microtubule network structure and this transport process for albumin uptake within cultured aortic endothelial cells affected by shear stress was studied. Based on fluorescent images of albumin uptake obtained by using confocal laser scanning microscopy (CLSM), both the microtubule network and albumin uptake in ECs were disrupted by colchicine and were affected by shear stress loading.

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Tensile properties of smooth muscle cells freshly isolated from rat thoracic aortas (FSMCs) in their major and minor axes were measured using a laboratory-made micro tensile tester. The relationship between the tension applied to a cell and its elongation was obtained in untreated cells and those treated with 10^-5M serotonin to induce contraction. An initial stiffness of untreated FSMCs, normalized by their initial cross-sectional area perpendicular to the stretch direction, was significantly higher in the major axis (14.8±4.3kPa, mean±SEM, n=5) than the minor axis (2.8±1.0kPa, n=5). The stiffness increased significantly in response to the contraction, but the increase was much higher in the minor axis (59.0±9.4kPa, n=4) than in the major (88.1±13.3kPa, n=4). The difference between the two directions was insignificant in the contracted state. Observations of the morphology of actin filaments with a confocal laser scanning microscope in untreated FSMCs revealed that they were long fibers running almost parallel to the major axis, while those in contracted cells showed an aggregated structure without a preferential direction. These results may indicate that anisotropy in untreated FSMCs is caused by the anisotropic alignment of their actin filaments, and that such anisotropy disappears in response to actin filament reorganization caused by the contraction.

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Effect of fluid shear stress on permeability of endothelial monolayer was investigated using an endothelial cell (EC)-smooth muscle cell (SMC) cocultured model (CM). Permeability of ECs to bovine serum albumin was measured after exposure to shear stress of 1.5Pa for 48 hours. Morphology and VE-cadherin expression of ECs in CM was almost same as of ECs cultured alone (monocultured model, MM). Under static condition, EC permeability was 5.1±3.0 × 10^-6cm/sec (mean±SD) in MM and 6.5±3.4 × 10^-6cm/sec in CM. After exposure to shear stress, EC permeability in CM (2.2±1.9 × 10^-6cm/sec, p < 0.05) significantly decreased compared with the static model. However, EC permeability in MM (3.9±3.2 × 10^-6cm/sec) did not significantly change compared with static cultured condition. These results suggested that cellular interactions between ECs and SMCs have important influences on EC permeability.

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Hemodynamic factors are suspected to be involved in the localized pathogenesis and development of atherosclerotic lesions in the human thoracico-abdominal aorta. Hence, we studied the detailed flow patterns and the distributions of fluid velocity and wall shear stress there under the condition of a steady flow using five transparent aortic trees prepared from dogs as models of the human descending aorta and by means of flow visualization and high-speed cinemicrographic techniques. It was found that in all the cases the flow in the descending aorta was not fully developed to the extent to provide a parabolic velocity profile. Flow was disturbed at each junction, and most complex secondary and adverse flows formed at the branching site of the left renal artery adjacent to the lateral and posterior walls of the descending aorta. Furthermore, there was considerable interaction between the secondary and adverse flows formed at the branching sites of the four major arteries that stemmed off the descending aorta.

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It has been hypothesized that blood flow through high grade stenotic arteries may produce conditions in which elastic flow choking may occur. The development of atherosclerotic plaque fracture may be exacerbated by the compressive stresses during collapse. This study explored the effects of pulsatile flow on stenotic flow collapse. Pulsatile flow was produced using a gear pump controlled by a digitized physiologic waveform. Upstream and downstream mean pressures and pulsatile flow rates were measured and digitized. An improved model of arterial stenosis was created using an elastomer with an incremental modulus of elasticity matched to a bovine carotid artery in the relevant range of collapse. Additionally, the model retained a very thick wall in the stenotic region similar to arterial disease. Flow choking was observed for pulsatile pressure drops close to those previously reported for steady flow. The phase difference between flow rate and pressure between upstream and downstream of the stenosis occurred by the compliance of tube and stenosis resistance. For 80% nominal stenosis by diameter and 100+/-30mmHg upstream pressure, collapse occurred for average pulsatile pressure drops of 93mmHg. Pulsatile flow experiments in this model revealed the range of conditions for the flow choking and the paradoxical collapse of the stenosis during systole with expansion during diastole. The stenosis severity was dynamic through the pulse cycle and was significantly greater under flow than the nominal severity. The results indicate that flow choking and stenotic compression may be significant in thick-walled arterial stenoses subjected to pulsatile flow.

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To study the wall motion abnormality and characteristic flow distribution observed in the heart with myocardial infarction, we modified our finite element model of left ventricle and performed simulations at two different phases after the onset of the disease by applying characteristic material property to the infarcted region. The model could not only reproduce the hemodynamic change in myocardial infarction but also give mechanistic insight into the following complicating problems. 1) Stagnation of blood as the cause of clot formation 2) Extra energy wasted for the stretch of infarcted tissue. The effect of compensatory enhancement of the force generation in normal myocardial tissue is also discussed.

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This paper describes the prediction of index of thrombus formation in shear blood flow by computational fluid dynamics (CFD) with Lattice Boltzmann Method (LBM), applying to orifice-pipe blood flow and flow around a cylinder, which is simple model of turbulent shear stress in the high speed rotary blood pumps and complicated geometry of medical fluid machines. The results of the flow field in the orifice-pipe flow using LBM are compared with experimental data and those using finite difference method, and it is found that the reattachment length of the backward facing step flow is predicted as precise as that the experiment and the finite difference method. As for thrombus formation, from the computational data of flow around the cylinder in the channel, the thrombus formation (thickness) is estimated using (1) shear rate and adhesion force (effective distance) to the wall independently, and (2) shear rate function with adhesion force (effective distance), and it is found that the prediction method using shear rate function with adhesion force is more accurate than the method using the former one.

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Recent studies have suggested that long standing elevated wall shear stress might degenerate the arterial wall and be involved in the pathogenesis of intracranial aneurysm formation and development. The present study focuses on the interplay between the hemodynamic stresses, arterial wall degeneration and deformation. By constructing a computational model and examining the hypotheses that govern the rules to grow an intracranial aneurysm, we simulate the formation and development of intracranial aneurysms. The high wall shear stress is found to propagate towards the proximal and distal end of the formed aneurysm, which becomes the key factor for the expansion of wall degeneration and aneurysm progression. The development of aneurysm is influenced by the wall shear stress threshold, the Reynolds number and the rate of wall degeneration. Our preliminary results indicate that computer simulation can be used in the study of aneurysm mechanics and yields new insight into the mechanism of aneurysm pathophysiology.

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It has been conceived that the mechanical heart valves mounted in an artificial heart close much faster than in vivo use, resulting in cavitation bubbles formation. In this study, the mechanisms for cavitation in mechanical heart valves (MHVs) is investigated with monoleaflet and bileaflet valves in the mitral position with an electrohydraulic total artificial heart (EHTAH). The valve-closing velocity and pressure-drop through the valve were done, and a high-speed video camera was employed to investigate the mechanism for MHVs cavitation. The valve-closing velocity and pressure-drop of the bileaflet valves were less than that of the monoleaflet valves. Most of the cavitation bubbles in the monoleaflet valves were observed next to the edge of the valve stop and the inner side of the leaflet. With the bileaflet valves, cavitation bubbles were concentrated along the leaflet tip. Also, the number density of cavitation bubbles in the bileaflet valves was less than that of the monoleaflet valves. The number density of cavitation bubbles increased with an increase in the valve-closing velocity and the valve stop area. It is established that squeeze flow holds the key to cavitation in the mechanical heart valve. In a viewpoint of squeeze flow, the bileaflet valve with slow valve-closing velocity and small valve stop area, is safer to prevent of blood cell damage than the monoleaflet valves.

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Articular cartilage has biphasic property based on high water content. It is generally believed that the proteoglycan supports the compressive load, but the detailed loading mechanism has not yet been clarified. In this study, first we observed the changes in compressive stress and strain of articular cartilage under constant total compressive deflection. We evaluated the changes in modulus of elasticity, which was estimated from the stress-strain relation in equilibrium state. To examine the role of proteoglycan in compressed articular cartilage, we compared the time-dependent viscoelastic behaviors in both the intact cartilage and the cartilage treated with chondoroitinase ABC under constant total compressive deformation. We could confirm that the peak stress after compression and the modulus of elasticity at equilibrium were reduced after the digestion of proteoglycan. Next, we observed the changes in local strain in both articular cartilage specimens with and without chondroitinase treatment by monitoring the position of stained chondrocyte in the confocal laser scanning microscope. These visualized images indicated that the local strain changed time-dependently and depth-dependently. The digested cartilage showed the quicker change in movement and larger thinning in surface layer than the intact cartilage. These results indicate that the proteoglycan contributes to the compressive load-carrying capacity and controls the permeability.

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Adaptive remodeling of soft fibrous tissues under cyclic tensile forces was investigated. Patellar tendons of rat’s knee were harvested and mounted on apparatuses for mechanical stimuli. They were transplanted into the subcutaneous tissues and experienced mechanical stimuli of cyclic tensile forces (1N, 1Hz). Then the tendons were retrieved and their mechanical properties were evaluated with a tensile tester. Four experimental groups were examined in which loading conditions were (1) three times a day (2700 cycles a day) throughout 4 weeks, (2) twice a week (1800 cycles a week) throughout 4 weeks, (3) load-free throughout 4 weeks, or (4) control. Comparing to control group, the tendons in load-free conditions were very weak and shown statistically significant decrease in maximum load, strength and tangent modulus. Contrarily, the tendons in frequent loadings (three times a day) nearly maintained their mechanical properties. Thus the present study clearly elucidated the fact that cyclic tensile forces have significant effects on the mechanical properties of transplanted fibrous tissues.

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The human lumbar spine can support much larger compressive loads if it is applied along a follower load path that approximates the tangent to the curve of the lumbar spine compared with the vertical load path. In this study, a musculoskeletal finite element model of the simplified lumbar spine including idealized psoas major muscles in the frontal plane was developed and the quantitative role of psoas major muscles was investigated to generate the follower load by using stiffness methods when vertical loads are given. The muscle force distributions were analyzed under various loading cases and follower load constraints. The validity of the developed model was assessed through comparison with previous modeling and experimental studies.

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The purpose of this study was to investigate the influence of lateral muscle loading on the stress/strain distributions of the trochanteric Gamma nail (TGN) fixation within the healed, trochanteric and subtrochanteric femoral fractures by means of a finite element method. The effect of three muscle groups, the abductors (ABD), the vastus lateralis (VL) and the iliotibial band (ITB), were investigated. The analytical results showed that addition of lateral muscle forces, iliotibial band and vastus lateralis, produced compensation of forces and reduction of bending moments in the bone and in the trochanteric Gamma nail especially in the lateral aspect. The iliotibial band produced a higher impact as compared to the vastus lateralis. Therefore in the finite element analysis of the proximal femur with the trochanteric Gamma nail fracture fixation should include the lateral muscle forces to simulate load condition with maximal physiological relevance to the closed nailing technique.

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Macroscopic bone properties depend on the microscale structural organization and the properties of microstructural elements. In the case of cancellous bone, the network structure of trabeculae, i.e., bar/plate bone elements of submillimeter diameter/thickness, results in the anisotropic properties as a porous media, and it is important to investigate the mechanical properties of cancellous bone with relation to the microstructural and micromechanical properties of trabeculae. Efforts have been devoted for the mechanical test of single trabecula in this context. In this article, the mechanical property of single trabecula was examined by means of Vickers hardness test, and the content of hydroxyapatite crystals was evaluated by X-ray diffraction analysis. The results were discussed relating to the macroscopic mechanical and structural properties of cancellous bone.

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The purpose of this study is to predict with the use of FEA, the differing predisposition to cortical bone resorption and subsequent distal migration of an un-cemented femoral hip replacement stem subjected to long term biomechanical high compressive stresses, while varying the load angles, the material properties of the stem, and the stem length. A two-dimensional hip model was constructed to estimate the minimum principle stresses (P₃) and migration magnitudes. Bone remodeling at the interface between the bone and the prosthesis was performed by comparison of the local compressive stress to physiological stress values governing bone resorption. With respect to load angles, migrations of the hip prosthesis did not occur with load angles between 63° and 74° load angle in relation to the longitudinal axis of the bony femur, as the compressive stress generated on the cortical bone was under the criteria threshold for bone resorption (-50MPa). In addition, the magnitude of migration (17%decrease) was relatively more sensitive to changes in stem length than those (92%decrease) of changes of material properties. In conclusion, using an FEA model for bone remodeling, based on the high compressive stresses exerted on distal cortical bone, it is possible to estimate migration magnitudes of cementless hip prostheses in the long term. The load angles have been shown to be an important parameter affecting the migration magnitudes and furthermore, it can be demonstrated that the stiffer materials and reduction of stem length can decrease the migration of cementless hip prosthesis in the long term.

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The objective of treating the fractured bone is to achieve painless functioning of the bone and undisturbed healing at the fracture. Internal fixation by stiff bone-plate is one of the standard methods to achieve these objectives. Recently, there is considerable interest in the usage of compliant plates to enhance bone healing with reduced stress shielding. Herein, first an analytical solution is developed to determine screw forces in the bone-plate assembly that conforms the plate and the bone under bending load. Based on the analytical calculations, an optimal fixator plate selection criterion for necessary and sufficient stress shielding is proposed. Second, effectiveness of employing a non-homogeneous stiffness graded (SG) plate rather than a homogeneous stainless steel (SS) plate for stress shielding is investigated using a finite element method. It is found that stress shielding on bone by SG plate is less compared to SS plate.

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Now, it is possible to discuss qualitatively the effects of skis, skier’s ski control and slope on a ski turn by simulation. The reliability of a simulation depends on the accuracy of the models used in the simulation. In the present study, we attempt to develop a new ski control model for a “parallel turn” using a computer graphics technique. The “ski control” necessary for the simulation is the relative motion of the skier’s center of gravity to the ski and the force acting on the ski from the skier. The developed procedure is as follows. First, the skier is modeled using a multibody system consisting of body parts. Second, various postures of the skier during the “parallel turn” are drawn using a 3D-CAD (three dimensional computer aided design) system referring to the pictures videotaped on a slope. The position of the skier’s center of gravity is estimated from the produced posture. Third, the skier’s ski control is obtained by arranging these postures in a time schedule. One can watch the ski control on a TV. Last, the three types of forces acting on the ski from the skier are estimated from the gravity force and the three relative types of inertia forces acting on the skier. Consequently, one can obtain accurate ski control for the simulation of the “parallel turn”, that is, the relative motion of the skier’s center of gravity to the ski and the force acting on the ski from the skier. Furthermore, it follows that one can numerically estimate the edging angle from the ski control model.

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This paper aims at realization of the walk of a spider as an organism, and intends to construct a robot that can walk with its 8 legs in cooperation with each other by adapting itself to various types of environmental information. A spider as an organism can walk on a variety of places by corresponding to a variety of environment. With the aid of neural networks and fuzzy control, decision-making or realization of the environment-adaptive walk is done. Utilizing the distance to the destination or fear information as surrounding environmental information, a report is hereby released with respect to the computer simulation and experimental result of walks ambiguously expressed in such a manner as “gradually accelerate speed" or “walk so as not to be tired."

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A monopivot magnetic suspension blood pump has been developed in our laboratory. The flow patterns within the pump should be carefully examined in order to prevent thrombogenesis, especially around the pivot bearing. Therefore, the effects of the pump geometry on the local flow were analyzed using computational fluid dynamics together with the experimental flow visualization. The engineering goal was to reduce the area of stagnation around the pivot in order to prevent thrombus formation. As a result, the stagnation area and the flow rate through the washout holes were found to be highly affected by the size and geometry of the washout holes. Secondary flow was revealed to form a jet-like wash against the pivot, thus preventing thrombus formation. The flow rate through the washout holes was estimated to be up to one fifth of the pump flow rate, depending on the cross-sectional areas of the washout holes. Furthermore, an anti-thrombogenic effect was attained by removing a small gap between the male and female pivots.

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Digital Image-based Elasto-Tomography (DIET) is a novel method of determining the distribution of elastic properties within the breast. Using an array of calibrated digital cameras and an inverse reconstruction algorithm, DIET allows reconstruction of the internal elastic stiffness distribution of the breast using only motions at the breast surface. This reconstructed stiffness should clearly show carcinoma based on their high elastic property contrast with healthy tissue. Proof of concept studies are presented for both the calibration of the digital imaging system and the inverse reconstruction algorithm. The reconstruction algorithm identified high stiffness tumors in the majority of test cases, even with the addition of random noise based on expected calibration accuracy.

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A new method using ultrasound sensors to detect the diaphragm position of a ventricular assist device (VAD) was proposed. Two small ultrasound sensors of 2.4mm diameter were attached to the outside surface of blood chamber of a pneumatic VAD. The receiving crystal received the ultrasound from the transmitting crystal reflected by the diaphragm. The diaphragm position was calculated by using geometric relation among two sensors and ultrasound propagation time. Validity of this method was evaluated in a mock circulation test under various driving conditions of VAD by comparing the ultrasound signals with driving pressure waveforms. The ultrasound signals could detect full-fill (FF) and full-eject (FE) status shortly before the spikes appeared on pressure waves, which are currently available to detect FE and FF but accompanies excessive extension of the diaphragm. This method would be helpful to avoid overloading of diaphragm. Linear correlation was observed between the output from VAD and blood volume calculated from the change of diaphragm position multiplied by the heart rate. This monitoring method of diaphragm of a VAD was proven to have advantages over the current method toward better control of a pneumatic VAD.

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Insect cuticle possesses excellent mechanical properties, such as strength, stiffness, fracture toughness, which are closely related to its elaborate microstructures optimized through millions of years’ evolution. SEM observation to the insect cuticle shows a particular distribution of fibers surrounding a hole in the insect cuticle, which is quite different from that in conventional man-made composites. In this paper the mechanism of such microstructure is analyzed. Making use of such microstructure, fiber-reinforcing laminate specimens containing preformed holes are designed and fabricated, the ultimate strength of which is investigated experimentally. For comparison, the ultimate strength of the fiber-reinforcing laminate specimens containing drilled holes is also tested. It shows that the ultimate strength of the laminates with preformed holes is distinctly higher than that with drilled-holes, and the difference increases as the hole diameter increases.

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This paper concerns the minimization of acoustic potential energy in an enclosure by both active noise control (ANC) and active vibration control (AVC). First, the optimal feedforward control law for minimizing the acoustic potential energy in a cavity walled by flexible structures is derived. Secondly, it is found that the control acoustic power radiated from each acoustic secondary source used for ANC and control vibration power infused by each control actuator for AVC become zero under the optimal control condition. It is also found that the zero control power phenomena are the necessary conditions for the optimality. Finally, the control effects for minimizing the potential energy using ANC and AVC are demonstrated from a viewpoint of numerical analysis.

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Dry hobbing has great advantages such as its environmental friendliness and its ability to reduce manufacturing cost. Dry hobbing, however, often causes failures of the cutting edge of a hob or problems on the surface quality of the tooth flank of a manufactured gear. The pinching and crushing of generated chips between the cutting edge of a hob and the tooth flank of a work gear is considered to be a major cause of such problems. A simulation method of cutting using a hob was reported. In this report, the simulation is applied to solving the industrial problems of dry hobbing. The simulation clarifies the mechanism of cutting edge failures. The “distance of single-edge cutting” of a hob tooth is proposed to be an index of pinching and crushing of chips. Factors influencing this index are investigated and fundamental countermeasures against pinching and crushing are shown. This method has been applied to solving problems in the mass production of automotive gears, and good results were obtained.

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In this study, a novel hydraulic brake system is proposed in order to increase the reliability of railway brake systems. The reason hydraulic brake systems have not been taken up as a practical railway brake system until now is that the brake pressure control valve inherently has internal leakage and this causes insufficient fail-safe function. Accordingly, We focus on the development of a hydraulic brake pressure control valve (BPC valve) in this study. By virtue of adopting poppet elements in the valve, the braking force is maintained without internal leakage even when the electric power supply fails. The developed BPC valve includes a built-in pressure feedback mechanism and it enables the pressure control function to be maintained when the pressure transducer is broken. The operating principle and wear compensation methods for poppet elements are also examined in this study. The experimental results verify the linearity of static behavior, the stability, and the performance of the valve in maintaining output pressure.

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A spring-lumped mass dynamic absorber system with internal vibration disturbance sources is constructed for active vibration control. The self-organizing fuzzy controller is employed to control the vibration amplitude of the main mass. This approach has learning ability for responding to the time-varying characteristic of the disturbance inducing vibration. Its control rule bank can be established and modified continuously by on-line learning. The experimental results show that this intelligent controller effectively suppresses the vibration amplitude of the body with respect to the external disturbance.

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When real robot manipulators are mathematically modeled, uncertainties are not avoidable. The uncertainties are often nonlinear and time varying. The uncertain factors come from imperfect knowledge of system parameters, payload change, friction, external disturbance and etc. We proposed a class of robust hybrid position/force control of manipulators and provided the stability analysis in the previous work. In the work, we propose a class of adaptive robust hybrid position/force control of manipulators with bound estimation and the stability based on Lyapunov function is presented. Especially, this controller does not need the information of uncertainty bound. The simulation results are provided to show the effectiveness of the algorithm.

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A novel hydraulic brake pressure control (BPC) valve for the railway rolling stock was proposed in the part I of this study. As a second report, this paper is concerned with the dynamic analysis and the performance evaluation of the hydraulic brake system using the BPC valve. In order to analyze the behavior of the BPC valve, a simplified transfer function and a nonlinear model of the valve are derived respectively. By use of simple linear model, it is achieved to determine the initial values of essential parameter simply. In addition, it is also achieved to investigate overall dynamic performance of brake system and to evaluate the effect of design parameters through the numerical analysis using detailed nonlinear model. The validity of mathematical models is confirmed by experiments. Finally, the performance of the hydraulic brake system using newly manufactured BPC valve is confirmed with an actual braking device of the E2 series Shinkansen railway.

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The optical telemeter system has been developed, which converts the temperature of rotating spindle to the digital data and carries the digital data from LED on the rotating side toward PD on the stationary side by the optical data transmission. Based upon the temperature distribution of hollow ball-screw obtained by the telemeter system, the thermal elongation of the ball-screw is estimated as the one-dimensional thermal elongation. Estimation accuracy, which is the difference between the estimated thermal elongation and the measured thermal elongation, is -3.1∼+3.2µ m for the thermal elongation of 50-60µ m over the length of 935.5mm of the ball-screw.

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