This paper deals with the motion analysis of snowboard turns using the measurement information of gliding on the actual snow field. The motion measurement systems that measure 3-axis angular velocity, 3-axis acceleration and 3-axis magnetic field are attached to the body segments of snowboarder and the bindings. The 3D posture is estimated by applying the sensor fusion using Extended Kalman filter. The joint torque of snowboarder is estimated by applying the measurement information of the systems to the closed-loop inverse dynamics. We conducted the measurement experiment by the snowboarder gliding on the actual snow field. The results represented the optimal joint torque of snowboarder in the snowboard turns. Furthermore, the analysis was conducted using the joint torque estimated by the proposed and previous methods. The results indicated the major and additional joint torque. Therefore, the analysis method can be used to the clarification of turn mechanism and the skill rating.
A fiber optic strain and vibration sensors (FOSVS) has been newly developed for application to health monitoring of structures. FOSVS is a fiber optic gap sensor and composed of two multimode cantilever and reflector fibers, a broad-band light, two photo detectors and a FBG filter. Reflected interference signal from the sensor was used for measuring axial displacement of the cantilever fiber, which is converted to strain. On the other hand, transmitted light power through the reflector fiber, which is converted deflection of the cantilever fiber, was used to measure transverse acceleration applied to the sensor. From the experimental and theoretical results, it appeared that the sensor could measure the axial strain and the transverse acceleration correctly. Furthermore it has been proven that the sensor characteristic is predictable by simple elastic beam theory. From the present results, it can be concluded that the FOSVS sensor has practical capability of simultaneous measurement of strain and vibration
By adding impulse excitation and energy dispersion operations, we obtain steady states of three-body vibro-impact system with two small oscillators coupled to one large oscillator under wave algorithm. From the steady collision conditions of the three-body system, we deduce a trajectory and a function of external force or enforced displacement for steady collision conditions of two kinds of two-body or single-body vibro-impact oscillator. By using either function, mass of the vibro-impact oscillator steadily collies with arbitrary impact positions and velocities. Compared with these functions, steady collisions were not achieved with harmonic external forces or enforced displacements. These functions could be favorable for steady impact process.
By adding impulse excitation and energy dispersion operations to time evolution of Patel's vibro-impact system, we can obtain steady states of three-body vibro-impact system with two small oscillators coupled to one large oscillator under wave algorithm. In this study, we proved that the steady states are stable limit-cycles by using state transition matrix. When small deviations of parameters exist, we observed the convergence of state vectors under the various conditions of the system in state transition diagram. Because this cycle is stable, we can control a collision velocity arbitrarily by changing the amount of excitation. In case the collision position shifts to the direction of the balance point, convergence time is shortened by increasing the amount of excitation. We obtained the optimal division number of excitation from the approximated state transition matrix and numerical calculations. Because the convergence time is minimized in the optimal division number of excitation, we can smoothly control the steady vibro-impact oscillation of tapping mode AFM and can smoothly operate the manipulator in space.
In this study, to separate contributions of vehicle interior noise using only response point signals, we tried to apply independent component analysis (ICA). To verify and consider applicability of ICA in contribution separation, we used engine and wind noises and mixed them in three conditions (synchrony / asynchrony / asynchrony with frequency characteristic), and carried out contribution separation using ICA to these mixed response signals. As results, the contribution was calculated accurately using time domain ICA in case the source signals were mixed synchrony, but the accuracy of this method became low when the signals were mixed asynchrony. However, frequency domain ICA could separate the contributions correctly. In case of the source signals were mixed asynchrony with frequency characteristic, permutation problem, in which the calculated contribution signal does not have the continuity among frequency, occurred. Then, we considered a permutation solution method using non-Gaussian characteristic of each calculated contributions. By applying the method, the contribution could be calculated accurately. Consequently, the proposed method using frequency domain ICA with the permutation solution was clarified to have an ability which separates contributions of vehicle interior noise using only response point signals.
In this paper, we describe a design and input voltage waveforms for a 3-DOF precise inchworm mechanism with 6 contact points. In those ten years, we have developed an omnidirectional and holonomic inchworm mechanism to provide a flexible, compact, and precise microscopic processing. In previous mechanism, a pair of U-shaped electromagnets arranged to cross each other are connected by four piezoelectric actuators so that the mechanism can move in any direction. However, microscopic operations are still difficult because of vibrations caused by inclination of the U-shape electromagnets. In this paper, we have proposed newly developed mechanism composed of a pair of Y-shaped electromagnets and six piezoelectric actuators to prevent the inclination of the electromagnets. We have analyzed a 3-DOF simple vibration model to get the dynamical response of the mechanism. We have also solved quasi-constant conditions of internal forces between a pair of the Y-shaped-electromagnets. Finally, we develop the expression for input voltage waveforms which represents holonomic and omnidirectional motion. We have checked the validity of the theoretical input voltages by orthogonal and rotational experimental results.
One of the problems in ceramic grinding is damage to tool after a long time operation. It gives a crucial damage to work piece so that the grinding tool has to be replaced by new tool before the crucial damage. Acoustic emission is often used in the monitoring. It gives satisfactory results in certain case, while some results are ineffective because the acoustic emission is sensitive to noise. In the present study, we use the vibration acceleration of the ceramic work piece during the grinding process. The acceleration can be easily acquired and show stable characteristics irrespective of measurement location. We investigate a feasibility of damage monitoring of ceramic grinding tool using the vibration acceleration, and focus on the amplitude modulation of the obtained acceleration. A direct frequency analysis to the obtained acceleration is ineffective for the monitoring because it only shows broadband random frequency components. On one hand, the frequency analysis of the amplitude modulation shows significant results. The rotational frequency of the tool and its multiples are clearly observed in the frequency components of the amplitude modulation, and the tool condition can be monitored by tracking the transition of the rotational and its multiples frequency components.
Numerical analysis technique for three dimensional sound fields including perforated plates vibrated by sound pressure and mechanical force is proposed. The technique is an acoust - structural coupled analysis technique which is based on boundary element method for sound fields and finite element method for perforated plates. To verify validity of the numerical analysis method, the sound field in the acoustic tube with thin aluminum perforated plate was analyzed by the method, and the computed result was compared with experimental result. The sound absorption coefficient of the perforated plate computed by the present method proved to be good agreement with experimental results. We found that the accuracy of the proposed method is enough and the method is useful for designing sound absorption structure using perforated plates.
Lightening each part is needed as one method to improve the Fuel Economy of the car. On the other hand, a certain amount of mass is required for the brake rotor as thermal capacity because the main role of the brake is to convert the kinematic energy of the vehicle into the frictional thermal energy for decelerating the vehicle. Therefore, the appropriate heat design becomes important aiming at lightening brake parts. Many thermal analyses to design the strength and the cooling performance concerning the brake rotor are done. However, there are a few papers that treat the relation between the thermal analysis and the brake friction force. Authors have been developed the simple calculation method of the temperature on the friction surface where the pad and rotor come in contact. Then, it is found that contact form is one of factors in fluctuating brake friction force from the bench test data and the calculated friction surface temperature. In this paper, the calculation method of two dimensional temperature distribution of the rotor is proposed. The calculated results are effective to confirm the detail of radial temperature distribution of the rotor as a short time under braking. The tested pads and rotors were analyzed by EPMA on the friction surface. These results show that a detectable amount of tin is difference. It is found that the fluctuating brake friction force has affected by the relationship between the friction surface temperature and the melting point of tin.
We are developing a simulation program called ASSESS (A Survey Simulator to Evaluate Safety Systems) which is intended to evaluate the effects of automotive prevention safety assistance systems. A simulated driver in the ASSESS drives a vehicle to avoid collisions with other vehicles. For the driver to drive safely, we need to determine the braking operation algorithm. The two decisive factors of braking operations here are the braking timing and the brake pedal force. In this paper, the former is discussed. After analyzing the previous experiment results about human cognitive judgments, we revealed that the timing of cognitive judgments is decided by the inverse of Time To Collision (iTTC), the inverse of distance, and the constant term. Based on this fact, we derived a formula to determine the driver's braking timing in the ASSESS. We also examined its validity by comparing the calculated braking operation time with the actual braking reaction time in the experiment. As a result, a simple formula that we proposed can replicate the start timing of the driver's braking operation.
This paper describes a structural optimization method for subsystems which realizes the desired value of coupling loss factors (CLFs) in statistical energy analysis (SEA). We have developed the structural design process on the basis of experimental SEA for the purpose of reducing structure-borne sound in real-world machinery. The process identifies the CLFs which should be changed in order to reduce the noise radiated from the machinery. The optimization method is implemented using the finite element method and optimization algorithms. The finite element model represents a part of a whole system which includes a junction together with their neighboring SEA subsystems, associated with the CLFs which need to be changed. In this paper, the proposed method for the structural optimization is demonstrated. Consequently, taking one CLF as the objective function, an optimization of the thickness of the shell elements is performed showing the efficiency of the structural optimization method.
This paper presents a sensor system to predict behavior patterns that occur when patients leave their beds. We originally developed plate-shaped sensors using piezoelectric elements. Existing sensors such as clip sensors and mat sensors require restraint of patients. Moreover, these sensors present privacy problems. The features of our sensors are that they require no power supply or patient restraint. We evaluated our system using a basic experiment to predict seven behavior patterns with machine-learning algorithms without setting thresholds. We obtained a result of predicted behavior patterns related to bed-leaving using only six sensors installed under a bed. Especially, our system can correctly detect behavior patterns of lateral sitting, which is a position that occurs when a patient tries to leave from the bed, and terminal sitting, which is the position immediately before bed-leaving. They were discerned from other behavior patterns.
In this paper, we report the results of experimental evaluation for methods of pedestrian traffic measurement at the festival held in Tatebayashi, Gunma prefecture. To measure pedestrian traffics, which include the direction and the number of pedestrian, we have already proposed two types of measuring methods based on subtraction stereo. One is the tracking method using Kalman filter, which is used in uncrowded scenes. The other is the method using KLT and Voronoi diagram, used in highly dense scenes. Finally, we show the accuracy of the proposed methods used in city environments.
In this paper, we discuss some phenomena of object clustering by distributed autonomous robots. This work was motivated by Swiss Robots, which collect scattered objects into some clusters without any global information nor intelligent concentrated controller. The clustering mechanism will be generated from the interaction among the mechanical system (i.e. body), the control law (i.e. brain), and the environment (i.e. real world). In order to understand the clustering mechanism, we utilize a “Implicit Control Theory”. This theory proposes not only “Explicit Control Law”, which corresponds to general control law, but also “Implicit Control Law”, which reflects the interaction among the body, the brain, and the environment. Based on the “Implicit Control Theory”, the object clustering by Swiss Robot is investigated. Moreover, this paper investigates not only the Swiss Robot's object clsutering, but also object clsuterings by another simple robots (Coronoc Robot, and Aggregator Robot). Though the Explicit Control Law and mechanical structures of each robot are exactly different, we can see common parts (principles) of Implicit Control Law. Furthermore, we demonstrate the correspondance between the Explicit Control Law and its clustering ability of each robot (e.g. number of clusters, clustering position).
Extra low-power suspension in the gravitational field of ground is achieved by a magnetic suspension system whose power source is solely a solar generator. Presently, solar cells become more efficient and cost-saving year by year. In this study, photovoltaic power generation technique is combined with the zero-power magnetic suspension. The zero-power control achieves the steady state in which the attractive force produced by a permanent magnets balances the weight of the floator and the control current converges to zero. Therefore, the power consumed for suspension is very small. However, the peripheral devices including sensors and a controller need power for their operations. The consumption power in the peripheral devices becomes dominant in the total power in the steady state. In this work, dedicated power-saving peripheral devices are newly fabricated. The average consumption power in the electromagnet is 20mW to suspend a 90-gram mass, while the consumption power in the peripheral devices is 13mW. The photovoltaic cells used in the apparatus has a maximum power capacity of almost 2W in the summer sunlight of 120klx. The system achieves stable suspension even under the illuminance of a fluorescent lamp of 5klx in the standalone.
In this study, we developed a robotic heartbeat simulator which is able to simulate a heartbeat for quantitative evaluation of availability and safety of the master-slave surgical robot system with heartbeat synchronization mechanism. We got a design specification of the robotic heartbeat simulator from in vivo measurement by using an experimental animal (pig). Based on the specification, we fixed a parallel mechanism link parameter of the robotic heartbeat simulator by genetic algorithm (GA). We measured the working space of the robotic heartbeat simulator and we confirmed that the robotic heartbeat simulator has the desired operating range. Furthermore, we conducted heartbeat simulation experiment by the developed robot. The results showed that a maximum value of cross-correlation function between desired trajectory and measured trajectory was 0.98-0.99 in x, y, z, roll and yaw axis, 0.89 in pitch axis. By this result, we revealed that the robotic heartbeat simulator has a high performance to simulate a heartbeat.
In the present paper, a rotational speed estimation method of a baseball is considered. In general, the gyro sensor is used for measurement of rotational speed. However, the gyro sensor in present condition can not measure for highspeed rotation. So, the signal processing procedure such as FFT or CWT (continuous-time wavelet transform) based on accelerometer signals are adopted instead of the gyro sensor measurement. First, the estimation procedure based on the three-axis accelerometer is described. Next, the estimation performances are verified in comparison with the estimation signals and measured signals by the gyro sensor by using accelerometer/gyro sensors which are built in a softball. By the result, it is verified that the estimated rotational speed by using CWT provides excellent performances in comparison with FFT and it is shown that it is able to simulate time variation of the rotational speed. Further, some estimation results for straight and curved ball by throwing experimental results by using the accelerometer built in a baseball are shown.
The chest compressions is one of the most important actions for the first aid cardio-pulmonary resuscitation (CPR). Because many people will be survived by CPR in the early-stage of cardio-respiratory arrest, it is expected the chest compressions becomes widely known to the public through trainings. The chest compressions is accompanied with an internal force and it is difficult for trainees to understand the amount of the required force only from demonstrations. In this paper, we develop an enhanced motion that enables the trainees to generate the required force for the chest compressions from dynamical point of view. A skilled motion is captured and modeled by an autonomous control system containing information of human motion. Based on decomposition of the controller, “Pseudo-reference” is introduced. Through the trainings with/without Pseudo-reference, the effectiveness of the enhanced motion is evaluated based on the output force and its weaknesses are declared which will be complemented by a trainer.
In this paper, the cutting mechanism and the cutting performance of a ball end mill for an inclined surface with spindle inclination by a contour path method are evaluated. In addition, a highly efficient and highly accurate cutting method is proposed. Ball end mills are used to produce many items, including molds and dies. However, the cutting process of ball end mills is very complex, so the highly efficient and highly accurate cutting method is not clear. Therefore, in this study, at first the modeling of a ball end mill and a workpiece with an inclined surface are carried out using 3D-CAD. Secondly, the cutting cross-sectional area is calculated by the interference of the rake surface and the uncut chip volume which will be removed by one cutting operation. And also, the evaluation value Ed corresponding to the cutting torque is defined and calculated. Then the influence of the cutting method and the workpiece and the spindle inclination angles on the maximum cutting cross-sectional area and the maximum evaluation value are shown. Thirdly, the conditions which expect good cutting performance with small evaluation values and including the cutting with the bottom edge of a ball end mill are picked out, and experiments are carried out under these conditions. Finally, cutting conditions which yield the good cutting performance are shown using the analytical and experimental results.
A sophisticated formulation for re-entrant flow-shop scheduling problem is discussed in order to plan an optimum production schedule by mathematical programming. In the formulation, repeated operations by the same production resource are taken into account in the cyclic manufacturing process for mono-product. The general constraints of the problem are represented in linear equations composed by decision variables including both absolute starting times and relative starting times of the operations. The absolute starting times provide the sequence of the processing order in the manufacturing activity, while the relative starting times assure the appropriate handling in cyclic operation for each production resource. Since the complexity of the constraints affects the optimization, redundant decision variables have to be eliminated from the constraints. In this paper, we derive a new formulation in which the absolute starting times variables are represented implicitly by the relative starting time variables. The new formulation guides stepwise optimization approach, that is, the total number of cyclic terms is minimized before the search for the shortest complete time of the product, or the flow time. The result of the pre-optimization contributes enlargement of the problem size in optimization. The number of the total processes of the products is evaluated to verify the feasibility of the formulation and the optimization procedures by computational examinations.
In the present paper, we describe the measurement of brain activation response during rotating a handle of a lathe and the measurement of brain activation response during lathe operation in a VR lathe environment and an actual lathe environment by near-infrared spectroscopy (NIRS). In the handle rotating experiment, we did instruction trial and non-instructed trial. In case of the instruction trial, subjects rotated the handle according to our instruction. On the other hand, subjects rotated the handle without thinking in the non-instructed trial. In the case of the frontal lobes, the oxyHb did not change in the non-instruction trial. Meanwhile, in case of instruction trial, the oxyHb increase in the frontal lobes. The results mean that the frontal lobes were activated by the instruction. In the lathe operation experiment, the results show that the brain activation response in the VR lathe environment was very similar to that which occurs during lathe operation in the actual lathe environment.
The Polishing process is used as finishing process of many products with smooth surface. This process is generally conducted by skillful worker as manual process and the productivity is low and difficult to control. An automatic polishing system which consists of inexpensive tool and general purpose machine tool are developed. However, system operator has to have know-how and experience of the polishing process to decide the machining conditions. In this study, optimization algorithm for machining time and improvement of the surface roughness were established. Software for optimizing machining conditions of the system was developed and evaluated the robustness of calculated conditions by Taguchi method. Total machining time with calculated and optimized conditions could be shortened by 12% than conventional time in plane polishing. It is concluded from result that: (1) Developed software using the proposed algorithm of automatic polishing is effective to decide machining conditions without know-how and experience of the polishing process. (2) Full automatic polishing become possible by using the combination of developed system and the software.
This study proposes the combinations of some hydrodynamic shapes formed on the end or the annular surface of oil impregnated sintered porous bearing as a DC spindle motor's bearing system. Hydro Wave Bearing or Pump In as a thrust hydrodynamic shape, and Herring Bone (Ⅰ&Ⅱ), Three Lobed Type or Sleeve as a radial hydrodynamic shape were proposed, and the total of eight kinds of combinations were produced as thrust-radial coupled bearing. It examines to optimize the hydrodynamic shape combination experimentally as thrust-radial coupled bearing by measuring the lubrication characteristics. This research report is especially referred to the experimental examination for Settling Time, Lissajous Curve diagram or Shaft Whirling by measuring the Time History Waveform of shaft such as the lubrication characteristics under unsteady shaft starting condition. Furthermore this report examines the influence of diametral clearance change to the lubrication characteristics such as above mentioned by measuring the Time History Waveform of shaft under shaft starting condition.
We prepared 10 types of expanded beads and 12 types of expanded bead cushions in order to estimate tactile impression using sensory evaluation on an SD scale. In this paper, we focused on the properties of expanded beads. Of the various types of multiple classification analyses, multi-regression analysis and quantification theory I were applied to the results of the sensory evaluation. Prediction formulae were made and it was found that the bead diameter was important for all sensory words in this research. The expanded beads with a diameter less than 1.5 mm were related closely to tactile impression. It was found that the diameter of 1.0-1.5 mm was a threshold value of the tactile impression. The sensory evaluation results for each sensory word were explained by the score of the item/category. The diameter and evenness of the expanded beads were important bead properties. The relationship between the sensory evaluation results and the mechanical properties of the expanded beads was examined.
The tensile strength of the solid structure fabricated by a direct metal lamination under various lamination conditions is examined. The direct metal lamination is a kind of the additive manufacturing process using the arc welding technology; where the molten metal made by the arc discharge is accumulated successively in this process. Combinations of lamination conditions such as welding current, torch feed speed and the cross feed of the torch are explored and the suitable conditions to realize a solid structure without weld defects are clarified. Then it is shown that the laminated modeling object has enough tensile strength compared with the same bulk material. In addition, the welding torch moving direction doesn't affect the strength of the object because the accumulated overlapping beads melt into each other under the suitable condition.
The purpose of this research work is to fabricate small pipes consisting of boron carbide. The characteristics of boron carbide are hard and anti-corrosion. However, it is difficult to sinter the material and to obtain small pipes. Therefore, a new method is developed to fabricate pipes of boron carbide in this paper. At first, graphite powder is mixed with boron powder. And the surface of mixed powder is irradiated by a laser beam. And then, the powder is evaporated at the central portion of the laser beam. Boron carbide is produced around the central portion by the chemical reaction between the graphite powder and boron powder. Then, a small pipe consisting of boron carbide is obtained. The outer, inner diameter and length of the pipes are measured for different irradiating conditions of laser beam. The boron carbide is detected by XRD in the pipes. It is deduced that the concentration of boron carbide at the inner surface of the pipes is more than that at the other portions. Connected two or three pipes are fabricated by this method.
Bolt/double nuts assemblies are used for preventing the self loosening when the clamp force is relatively low. In general, the fatigue load acting on the bolt increases in the bolted joint with low clamp force due to the separation at the contact plane. However, the effect of the locking force on the fatigue strength of the bolt has not yet been clarified. This study aims to evaluate the fatigue strength of a bolt in bolt/double nuts assemblies quantitatively. Fatigue tests were performed for bolt/double nuts assemblies by taking the locking force and the nut height as parameters. FE stress analysis was also performed to predict the fatigue strength using Ishibashi's and Yoshimoto's hypotheses concerning the relationship between the local stress and the fatigue strength of the material. The results show that the locking force has the effect to decrease the local mean stress of the fatigue loading on the first thread root of the bolt mating with the lower nut, and it leads to the increase of the fatigue strength of the bolt expressed by the nominal stress.
Development of a method or a system to support design of vision-friendly products for elderly persons is desired because it is difficult for young designers to understand elderly person's difficulty of vision. For the requirement, a method to simulate elderly person's vision using computer graphics and image processing is proposed and a basic system based on the proposed method is constructed. The system has the models of accommodation ability characteristics, optical characteristics of the crystal lens of human eyes, spatial frequency characteristics, and focusing velocity characteristics which are the characteristics on aging-related changes of the human eye. The system can then simulate a blurred vision occurred by deficient accommodation power, optical absorption change, aging nerve change, and focusing time change. Sign marks, Landolt rings and antenna marks were shown elderly persons as experimental samples, and the answers for visibility of these samples were obtained. The answer of elderly persons and simulation results were compared. As the result, the usefulness of the system was confirmed.
Recently, in the most of small and medium-sized industries in Japan, they are facing with the problems that occur from small amounts of orders with too much variety. In Maruzen Industry, about 70% of products are orders that have never been produced. Therefore, it is very difficult to estimate required production time. These miss estimation lead to overtime working, deadline breaking and so on. So it is very important to estimate it as accurate as possible. We have proposed prediction of production preparation time for each set-up for each machine by using Data Envelopment Analysis (DEA). Once we grasp production preparation time, we can grasp daily production ability for each machine. Moreover, once we grasp product abilities of machines in the factory, we can estimate total amount of products, and we can improve the scheduling that we do not need to overtime work and/or dead line break. In the previous study, some data did not match with the preparation time that part managers have had. In this study, we are going to propose reasonable preprocess method to derive accurate production preparation time.
In recent years, the demand for power generation capacity has increased considerably due to the electric drive of air conditioners and so on in the engines of civil aircraft. Therefore, it is estimated that power losses may increase in the accessory gearbox because of generators and pumps that in turn augment fuel consumption. To reduce these losses, Computational Fluid Dynamics (CFD) simulation that analyzes oil churning and windage losses was developed and improvements were made to the shrouds of bevel gears which have large losses in the gearbox. It was revealed that the loss was reduced up to 36% compared with unshrouded gears, by shrouding in the experiments. On the other hand, to assure the functional reliability of the gearbox, it is necessary to design spur gear trains of the gearbox in a manner that prevents the stagnation of oil inside the gearbox that occurs when the aircraft changes attitude. We performed CFD simulations and experiments to survey the application of flow guides to the spur gear trains. Experimental results showed that there was little oil stagnation within the improved gearbox.