Membrane structures are made of thin materials which have tension given by other structures. Their features include flexibility and lightness. However, when vibration is caused on membrane structures, it is hard to attenuate it. The purpose of this study is the vibration suppression of membrane structures by active control method with Dielectric Elastomer Actuator (DEA). In addition, we apply multiple DEAs to attenuate vibration effectively in a wide frequency band. DEA is also flexible and light, so it is suitable for membrane structures as actuator for active vibration control. To design the controller, the state space model is obtained by system identification based on experimental modal analysis approach. The controller is obtained by H_∞ control theory. The effectiveness of proposed active vibration control using multiple DEAs is validated by experiment.

To assess the quality of fruits and vegetables, firmness is often used as quality-related index. Firmness is represented by firmness index that is defined by combining resonant vibration frequency with mass of fruits or vegetables. This paper shows the non-destructive measuring technique of frequency responses for apples via a vibration excitation by dielectric elastomer actuator (DEA). An advantage of DEA is its flexibility, so it is able to adhere directly to spherical objects like apples. Then, DEA’s excitation force is well transferred to the target. Vibration experiment was carried out, and we obtained the frequency response and firmness index of the apples to evaluate the quality of apples.

This paper discusses a dielectric elastomer actuator (DEA) speaker with a concave shaped vibrating surface to control a sound radiation pattern without multiple speakers. DEAs have a sandwich structure that is a dielectric elastomer layer is wedged between flexible electrodes. Since flexibility DEAs can deform a desired shape easily, the authors developed the DEA speaker with a hemispherical shell or a spherical shell, yielding an omnidirectional radiation pattern. In our experiment, we formed the concave shaped DEA speaker using a vacuum chamber to create a directional sound source. We used a microphone array to visualize the generated sound radiation pattern.

The use of off-the-shelf materials is a promising approach to build soft robots and stretchable devices. Those premade materials are expected to enable rapid fabrication as they remove the need of some processes such as material preparation and thermal curing. In this contribution, we characterize soft actuators and sensors based on off-the-shelf dielectric and conductive acrylic elastomers to investigate the applicability of the materials for soft and stretchable devices. We observe areal strain of 8% at 5 kV in the actuators and a high-linearity (R² = 0.995) up to 50% of uniaxial strain in the sensors. These results illustrate that the materials used in this study is compatible to compliant devices and that the strategy to use off-the-shelf materials can be an effective method to rapidly fabricate soft robotic elements.

Belousov–Zhabotinsky (BZ) reaction is a chemical reaction which realizes oscillation of chemicals. BZ gel, that is a polymer gel in which BZ reaction occurs, shows oscillation of the volume in association with the reaction and it is expected to be utilized as a new soft actuator. Despite the large attention for the application of the gel, understanding of the dynamics seems to be insufficient. Under some assumptions which seem to be valid experimentally, here we propose a simple model for the dynamics of BZ gel. Analyzing the model mathematically, we obtain condition of parameters for realizing oscillation of the gel and discuss parameter dependence of period and amplitude of the oscillation. These results will be tested by experiment and utilized as a guide for proper design of BZ gels.

The small fan motor is used now to cool off with the IT apparatuses including the personal computer. An examiner evaluates a sound and vibration by the quality check of the small fan motor, an examiner changes the posture of the small fan motor dynamically. As for this method , an effect is recognized from experience in inspecting quality, but because the effect is not clear theoretically, an elucidation is necessary. Therefore I clarify a principle of rocking it using an experimental device and multibody to change the posture of the body of rotation consecutively in this study.

In this research so far, we have proposed an Inverse analysis method that models acoustic phenomena in the vocal tract, which is the space from the vocal cords to the lips, with a concentrated mass model to estimate the vocal cord source wave. In addition, the validity of the Inverse analysis has been confirmed by experiments using a shaker and by a valve that self-oscillates due to the air flow. However, the valve used in the previous study was significantly different from the actual human vocal cord in shape and physical properties, and it was difficult to examine the physical mechanism of vocal cord self-excited vibration. In this paper, we created an artificial vocal cords that has the same shape and physical properties as human vocal cords, and made it possible to reproduce vocal cord vibration that is close to the actual phenomenon. In addition, we propose a vocal cord vibration analysis model that can be calculated with high accuracy and speed by performing modal analysis on the artificial vocal cords. Furthermore, dysphonia is reproduced by adding a pseudo lesion to the analysis model, and the result is compared with the result of the Inverse analysis of the actual voice of the patient.

This research concerns sound transmission characteristic analysis for human middle ear lesions using finite element method. A large number of patients are suffering from the middle ear lesions, such as the tympanic membrane perforation, the arthrosclerosis, and the tympanosclerosis. These lesions can change the dynamic properties of middle ear, cause various kinds of hearing problems, as well as the decline of the quality of life. For an early detection of illness and the improvement of the cure, it is important to clarify the influence on hearing ability at the time of lesion of the middle ear. However, it is difficult to grasp the dynamic properties of the auditory organ of a human body by an experiment. In this paper, the dynamic analysis of the middle ear at the time of lesions using the finite element method was conducted. Firstly, a finite element model of a healthy middle ear was built up, and used to verify the validity of the model. The analysis results showed good correspondence to the experiment results of other study. Secondly, the influences of tympanic membrane perforations with different size and position are investigated. The analysis results showed that the decrease of hearing ability is proportional to the size of the tympanic membrane perforation. Especially, the perforation at lower part showed an obvious decrease of hearing ability. Thirdly, the influences of arthrosclerosis and tympanosclerosist occurring at different positions are investigated. The results showed that the arthrosclerosis of incudostapedial joint and the tympanosclerosist at upper part of the TM can obviously decrease the hearing ability.

Tympanoplasty is a surgical operation performed for diseases that make air-bone gap larger. Ossicular reconstruction for recovery of hearing is a part of this surgery. But there are some cases in which postoperative hearing depends on each patient’s base symptom, so this surgery has not been expected yet as a versatile way for recovery for hearing. There are some studies on the mechanism of sound conduction via the human intact middle ear, however we have not yet obtained enough information related to the mechanism of sound conduction of reconstructive models of auditory ossicles. In this study, we adopted threedimensional Finite Element Method (FEM) models of a human intact middle ear and reconstructed middle ear, and examined the mechanism of sound conduction of reconstructive models of auditory ossicles using vibroacoustic numerical analysis. As a result of the analysis, the validity of this study was confirmed by comparing them with the previous studies.

Events such as cognition and judgement for sensory stimulus have attracted attention in the fields of psychology, medicine, and engineering to investigate the process of information processing in brain. Questionnaire is often used as a method to evaluate the process of information processing in brain. In order to deal with human state which changes from time to time, method for evaluating events using biosignal is required. We used Auditory Event Related Potentials (ERPs) to evaluate events. ERPs contains P300 which appears by cognition and judgement for sensory stimulus. In this paper, we propose evaluation method for cognition and judgement using ERPs with P300. We used modified Duffing oscillator to investigate whether the parameters of mathematical model could be used in analysis. It was applied to EEG data which is obtained by ERPs measurement experiment. Interval estimation was used for parameters analysis. As a result, parameter A decreased and parameter B increased when ERPs appeared, and parameter C decreased after ERPs appeared. It is suggested that interval estimation can be a method which can evaluate events appearing in ERPs because it can investigate the change of model parameters due to cognition and judgement.

In this study, we develop 2-D in vitro transplantation system for human neurons. Dynamic stimulation was added for the purpose of promoting the connection between neural networks and their effects were evaluated. First, differentiation of human iPS cells was induced into motor neural progenitor cells. After 35 days, the neural progenitor cells are adhered, and are differentiated into neurons colony. Then 24 hours after adhesion, new neural progenitor cells colony are seeded near by as transplanted donor cells. Thus, transplantation was simulated by shifting the timing to start the adhesion culture. After transplantation and confirmation of cells adhesion, dynamic stimulation was applied. In this study, we established a living fluorescent staining method using NeuroFluor NeuO. Using this method and conventional method, staining was performed on day 1, 3, 5 and 7 after transplantation, and evaluation was performed. As a result, it was confirmed that the application of the dynamic stimulation promoted the differentiation growth rate over entire period, and also the networking between the transplanted neuronal donor cells colonies and the recipient ones was promoted by the dynamic stimulation.

In this study, we cultured two neighbor mouse neurons colonies in the 3-D gel embedded culture in differentiation process from iPS cells to neurons, and applied dynamic stimulation. We examined the effects of dynamic stimulation informing neuronal network between that colonies. To apply dynamic stimulation, we used a small piezoelectric vibration stage. Vibration conditions are set as the frequency:5Hz (12 hours stimulation-12 hours static and 14 hours stimulation- 10 hours static), the amplitude:60μm, and the culture period:7days, in horizontal direction. New evaluation methods were invented for connected neurites between two neurons colonies in the 3-D gel embedded culture. The result can be summarized as follows. Firstly, in vitro experiment system using two neurons colonies cultured by 3-D gel embedded culture was developed. Secondly, applying dynamic stimulation to two neurons colonies cultured in 3-D gel embedded culture, the effects of promoting differentiation and growth of whole neurons were observed. In particular, statistical significance was confirmed between the 14 hours stimulation-10 hours static and the static case. Thirdly, two new evaluation methods were invented. One method is focused on differentiation and growth about neurites, and the other is focused on neurites connection between two neuron colonies. Finally, possibility of increasing connected neurites network by applying dynamic stimulation was suggested with 12 hours of stimulation-12hours of static, and also 14 hours of stimulation-10 hours of static.

Neural cells, which are generally said to be hard to recover from physcical damage, are equipped with function of a sensor that senses stimuli and extends axons has been elucidated. In this study, we investigated the effect of the dynamic stimulation on damaged mouse neuron colonies in neuronal network reconstruction. The neural cells differentiated from iPS cells are cultured for 5 days, and after the cells have sufficiently grown, the neuronal cells colony is damaged. Next, dynamic stimulation is applied for 6 days after the damage applied. To apply dynamic stimulation, we use a small piezo electric vibration stage. The vibration condition is set as the amplitude of 60 µm, the frequency of 5 Hz, and the interval stimulation with every 12hours in the direction perpendicular to the damaged surface. As a result, it was confirmed that the neurites are reconstructed from the damage by the applied dynamic stimulation.

Applying mechanical vibration to cultured cells gives cellular biochemical responses activated so that it can be applied to medical fields such as regenerative medicine. However, the cellular mechanisms of sensing mechanical vibration and transducing into the biochemical responses have not been clarified. One of the previous studies culturing osteoblastic cells under mechanical vibration reported that gene expression levels related to bone formation reached maximum dependent of frequencies like a resonance curve from a mechanical engineering point of view. Considering the analogies between mechanical and biochemical responses of a cell, modes of vibration of a cell can be related to the cellular mechanisms of mechanosensing. In this paper, we experimentally measured displacement of a fluorescently labeled nucleus of living cell under horizontal mechanical vibration of 25-100 Hz, 0.5-2.0 G by using an experimental system consisting of an electromagnetic exciter, a fluorescent microscope, and a high-sensitivity and high-speed camera. To measure the displacement from the images captured under static state and dynamic state where the velocity of vibration was 0, fluorescent microspheres were adhered on the bottom of a cell culture dish as the reference positions. As a result, the displacements of the nucleus were measured but frequency dependencies were not observed in those conditions. This present paper will contribute to elucidating upstream of the mechanisms of mechanosensing from mechanical engineering point of view.

In this study, we report a novel cell suspension culture method. When culturing large quantities of cells, suspension culture is generally used. We performed suspension culture using agitation by acoustic streaming. First, we manufactured the suspension culture devise that can generate acoustic streaming and agitate medium in a cell culture flask. Next, we performed cell culture experiments using the devise. As a result, the cell proliferation rate in the case of irradiating ultrasound was higher than that in the case of not irradiating ultrasound. Therefore, cell suspension culture can be more efficient using agitation by ultrasound irradiation.

Cell adhesion is closely related to various cellular properties. However, there is no effective method to measure cell adhesion. Meanwhile, we have developed an enzyme-free detachment method, which can detach cells by irradiating ultrasonic. Hence, we set out to develop a method for measuring the adhesive force of cells by irradiating ultrasonic from the bottom of the dish. As a preliminary experiment for this purpose, we fabricated a cell detachment microfluidic device for irradiation of ultrasonic on a cell in order to focus on observation of one cell. The microchannel was made of a cover glass and PDMS, and the ultrasonic vibrator was fabricated by using a transducer with a glass plate and a piezoelectric ceramic plate. By using this device, the mesenchymal stem cells were cultured in the microchannel, and ultrasonic irradiated to a single cell cultured in the microchannel. By increasing the output voltage of the transducer, cells detached by the ultrasonic were observed.

In recent years, studies have been conducted to extract three-dimensional images of blood vessels and analyze the blood flow using CFD (Computational Fluid Dynamics) to support the diagnosis and treatment of cardiovascular diseases. However, this method has a problem that the calculation time is long and the stress in the blood vessel wall cannot be calculated because the blood vessel wall is regarded as a rigid body, and the pulse wave analysis cannot be performed accurately. The purpose of this study is to develop an analytical model that can calculate stress in blood vessel wall in a short time. In this paper, the vibration of the blood vessel wall was modeled by the finite element method, and the blood flow analysis was modeled by the one-dimensional difference method, and a coupled model of the blood vessel wall and the blood flow was developed.-

SMID-MCDG are children with severe motor and intellectual disabilities medical care dependent group. Most of them have difficulty expressing themselves using their voice and face. Therefore, those who take care of them pay attention to their motion and physiological signals to understand their emotion. However, it cost much time to become to be able to understand their emotion because their motion signals are unclear and physiological signals change for various reasons. To solve this problem, I tried to develop emotion recognition system for SMID-MCDG using motion and physiological signals measured by wearable sensor. This system cannot speak for them but might be clues for communication. As a first step, I considered the methods of emotion recognition based on the data collected by simulation experiment. The simulation experiment were conducted in supine posture to simulate that SMID-MCDG is bedridden. In the experiment, pleasant, unpleasant or neutral were evaluated per minute. In the emotion recognition, the number of motions for one minute and heart rate variability are chosen as features and decision tree is used as classification method. As the result, proposed method showed about 64.5% of accuracy rate for the data of simulation experiment.

The number of home water server users is increasing by year. Installing a water container on a water server is one of the important factors affecting usability. In this paper, a subject experiment was carried out in which a water container was mounted using five types of commercially available water servers. The physical load and operating time of the subjects was quantitatively and statistically evaluated from the information obtained from the electromyography, motion capture, and acceleration sensor and the results of an interview questionnaire.

We propose a method to detect human rhythm movement in real-time using jerk. In recent years, education and cultural activities such as music and dance have attracted attention as a place for people with disabilities to participate in society. In order to promote participation of persons with disabilities, it is necessary to provide support for those with disabilities. Therefore, we are conducting study on a system that detects rhythm movements in real-time by the movements of a music conductor or dance instructor and transmits them to a performer using a haptic interface device. A three-axis acceleration sensor is used for motion detection to measure a mixed acceleration. Next, the jerk is obtained by differentiating the acceleration with respect to time. The jerk has a remarkable peak at the timing of the beat of the rhythm movement. In this paper, it was clarified by experiments that real-time detection can be performed by a microcomputer by simplifying this numerical analysis part.

The manuscript describes the characterization of the dialysis needle puncture in terms of hand manipulation dynamics. The present study aimed to present gripping force features denoting expert or novice operation trends. Our method uniquely utilized tri-axis force sensors mounted on the body of the dialysis needle, which measures Three-dimensional force vectors of thumb side and index finger during the punctuation to the skin vessel model. Novice student volunteers and Clinical engineers who expertize dialysis treatment participated in our experiment. The results revealed that the skilled penetration concentrated vertical gripping forces, and smoothly connected to sheering force for the needle insertion. The proposed quantification expects to contribute to skill enhancement.

In the endoscopic surgery, the forceps attached many kinds of gripping clip have been used, but it has been pointed out that there is a difference in the operability of the endoscopic forceps in the actual operation. In this study, to consider the performance of Endoscopic forceps for sensing the property of flexible materials using sensory characteristics, a sensory test was carried out by Scheffé’s methods of paired comparison and Thurstone’s methods which are used for the sensory test. The specimens were used a silicon rubber with different hardness as a substitute for material as an object of the sensory test. From the experimental results of the sensory test and an analysis of variance with the score as a sensory property, the effect of the main factor, which was explained as the difference of the specimen hardness was significant at 99% confidence level in all cases. The combined effect was not significant with the forceps, which means that the ability of forceps was limited to detect the discrimination of the magnification relations of hardness. As a result, it was made clear that the discrimination accuracy of hardness for specimen using the forceps was low compared than direct gripping for discrimination part.

This study verified the rehabilitation effect of the power assist leg that was developed as an ankle joint rehabilitation device. The experiment imposes a standing posture for 60 minutes after rest in order to reduce the function of the lower leg. After that, the power assist leg was attached to one leg to rehabilitate. The rehabilitation frequency was 50 times, 100 times, 150 times, and 200 times. In order to evaluate the effect, the range of motion of the ankle joint, the flexion force of the toes and the muscle hardness of the lower leg muscles were measured. The rehabilitation effect of wearing the power assist leg was remarkable in the range of motion of the ankle joint and the muscle hardness of the lower leg muscles. The most effective frequency of rehabilitation was 150 or 200, depending on the measurement items. Considering time issues, rehabilitation using the power assist leg was effective when performed 150 times (60 minutes).

This paper discussed the rehabilitation system using the power assist hand. The power assist hand is the rehabilitation equipment for hemiplegic disabilities using bellows actuators. We developed the self rehabilitation system which is composed of a power assist hand and a hand motion capture device. The hand motion capture device used here is a leap motion sensor. This sensor is very useful device for getting the positions of finger joints. The system recognizes the flexion or extension motion of healthy fingers using the leap motion sensor, the power assist hand moves according to the motion of healthy hand. The effectiveness of our system is demonstrated by several experiments.

Recently, needs of robot technology specialized for locomotive rehabilitation and gait assistance are expected increasingly. In gait and locomotive assistance, appropriate recognition of walking patterns and navigation are required; however, most of supporting devices are directly intervening in movements of lower limbs and therefore they let walking patterns be unnatural. In order to solve this problem, we propose a method to estimate walking patterns from movement of lower limb movements and force/contact interaction with upper libs. Step length and velocity can be measured from the movement of lower limbs by a laser-based sensor, and the dependency on the assistance can be measured from the upper limb by a force and tactile sensors, aiming in the optimal control of intervention in walking support for gait navigation. In this paper, we focus on a detection algorithm of walking patterns from the lower limbs.

Head injuries are one of the most frequent outcomes of paediatric accidents. Severe head injuries such as cranial fractures and intracranial bleedings are difficult to diagnose by external appearances. Of those critical head trauma, acute subdural haematoma (ASDH) causes high death rate and serious sequela. Some former studies stated ASDH as a representative case for shaken baby syndrome (SBS), claiming that ASDH is a sequel of strong shaking events inflicted to a child head. On the other hand, some researches found peaks of global head accelerations and velocities under shaking events were very low compared to impact situations. Since past studies mainly focused on the head acceleration for the investigation of head traumas, cause of ASDH was always a controversial topic. However, a recent study suggested that relative motions between skull and intracranial subjects could be the cause of ASDH. The study used a finite element (FE) model to investigate the intracranial behavior. Findings over the relative motion between skull and brain using the FE model enlightened new perspectives of ASDH researches. Due to paucity of infant PMHS data, there are very few paediatric FE models ever built. Hence, the current study newly developed a 6mo head FE model, and its biofidelity was validated against quantitative experimental data. The validated model was then used for simulations, and conditions susceptible to ASDH were investigated. As a result, no general correlation was to be found between head acceleration peaks and a relative motion regarding brain and skull. An importance to distinguish the head impact location was indicated as well, since occipital impacts showed a significant risk of sustaining ASDH, regardless of the drop height.

Perinatal well-being and support for childbirth are important issues as measures against the declining birthrate and women's social advancement in Japan. Meanwhile, although the death of mothers and infants during delivery has decreased due to advances in medical technology, troubles in delivery has still been reported. If delivery progress is delayed, there is a risk of serious problems and could affects the prognosis of the mother and fetus. During delivery, it has been clarified that the fetus progresses to the uterine ostium with rotating his own body. It is considered that the maternal muscle activity around the uterus also plays an auxiliary role in childbirth, though the detailed mechanism has not been revealed. Although various methods are used to measure muscle activity, it is necessary to select a non-invasive method considering the effects on the mother and fetus because the main purpose of this study is assessment of muscle activation for pregnant women. The surface electromyography (EMG) is a method for measuring muscle activity that can be used for pregnant women. Thus, the muscle activity around trunk during bear down was measured for four women in this study for the future study in the process of giving birth for pregnant women. At first, EMG electrodes were placed on the right and left upper rectus abdominis, lower rectus abdominis, oblique abdominal muscle and adductor muscle. Next, the participants did the act of bearing down on a bed. As the results, some trend of the muscle activity during the act of bearing down motion was observed.

Falls in people with walking disabilities lead to being bedridden and an increase in long term care. The prevention of these incidents is thus a key factor in maintaining activity level and maximizing their Quality of Life (QOL). The sagittal plane motion has been widely studied, but there are few studies about frontal plane motion such as falls to the side. In this study, we focus on frontal plane motion and consider fall prevention by plantar height. Because falls may occur when the center of gravity, which is followed by the ground reaction force, is shifted from the base of support, giving plantar height can be applied to fall prevention. The purpose of this paper is to assess the effect of plantar height on fall prevention. We used two types of theoretical models, an inverted pendulum model and a self-righting doll model. First, the motion in the frontal plane of a developed leg foot model was observed. Then, its motion was compared with the simulation results. As a result, the simulation of the self-righting doll was close to the experimental model. Second, the relation between plantar height and radius of the foot was considered. As a result, the radius of the foot would be estimated at 0.77 m and 0.13 m under “without height conditions” and “with height conditions”, respectively. From the viewpoint of the equation of motion of the self-righting doll, restoring torque resisting fall increased with decreasing the radius of the foot. From the above, this paper indicates that the self-righting doll model is valid as the leg foot model, and the plantar height affects fall prevention.

In the sport of golf, the use of an appropriate club is of paramount importance. Hence, we developed a method to determine the optimal weight of a suitable club for an individual golfer. The ultimate goal of this method is to estimate changes in the swing when the club characteristics are changed and to fit the club to the golfer’s needs. To this end, it is first necessary to study the swing behavior of clubs of different types, based on standard club parameters. This report focuses on the measurement and estimation of the swing behavior of clubs of different weights. The first step of this study was to measure the swing of clubs of different weights and calculate the torque exerted during the swing. Then, power spectral density (PSD) values were obtained by performing fast Fourier transformations (FFT) on the obtained torque data. The PSD values for the different club weights were compared, and based on this comparison, the PSD values were corrected by applying an amplification function. The inverse Fourier transformation was then applied to the corrected PSD values to obtain estimated torque data. Finally, using the estimated torque data and performing forward dynamics calculations, the change in swing behavior was analyzed.

This study attempted to propose a methodology which can quantify the influence of cushioning properties of the shoe sole on the propulusion mechanism of support leg joints in running. The cushioning properties were quantified as stiffness and viscosity of spring and dashpot set between foot segment and the ground. The foot segment was modelled as a 2-D rigid segment connected to the articulated shank and thigh segments moving in the sagittal plane during support phase in order to reduce the influence of the disturabance due to fluctuation of the position vector pointing from cg of the segment to the center of pressure(COP) of the segment when quantifying the dynamics contributions of the support leg joints’ torques. In order to calcualate the dynamic contribution of support leg joints’ torques to the generation of the state values of the foot segment including linear and angular displacements of the segment, a recurrence formula was derived from the combination of the discretized equation of the support leg motion and a difference formular regarding the genreralized acceleration vector of the expanded system. With use of this recurrence formula it becomes possible to quantify the dynamic contributions of joint torques of the support leg joints to the generation of acting force vectors at fore-foot and rear-foot parts.

In gymnastics, the skeleton of the athletes can be estimated from many points having three-dimensional coordinate data by measurement control using LiDAR (Light Detection and Ranging), and the motion can be known. However, the system cannot know what kind of load is being put on the athletes' bodies. Also, it is not possible to know in detail how top-level athletes handle apparatus. It is considered that if we can measure apparatus' motion and grasp the athlete's motion using the data, it will be possible to evaluate the load by the exercise and the accurate use of the apparatus. Therefore, it is important to understand the dynamic response of the apparatus to the athlete’s motion. However, it is not desirable to directly attach a sensor to the bar because it interferes with the competition. For example, if it is possible to grasp the deformation and stress of the apparatus by attaching sensors to the post end, the measurement can be carried out without affecting the competition. In this study, we measured the displacement of both ends of the bar with an accelerometer that can sense how the bar is deformed by applying a static load to the bar. It was shown that the deformation identification of the bar was possible by substituting these measurement results to both ends of the bar of the model using the finite element method as displacement quantity.

In recent years, with the serious aging society, research on assist suits is being conducted. In order to setting the optimum assist timing for each user, we proposed a method to determine the assist timing for wire type assist suit. In this method, since the assist timing is determined based on the hip joint angular acceleration by the IMU sensor. Specifically, the assist range is defined by the standard deviation of the point which the positive/negative value of thigh acceleration is reversed to the point that the positive/negative value of acceleration is reversed again, and the two timings when the sign of the differential value of the angular acceleration is inverted is defined as the maximum tension timing. As a result of the experiment using the assist timing created by this method, the effectiveness of the created assist timing was shown from the results of the hip joint angle and the hip joint torque.

Assessment and improvement of balance ability is an important issue in the medical field. The balance ability should be divided into static balance ability and dynamic balance ability, and it is necessary to notice the dynamic balance ability from the viewpoint of fall prevention. This paper focuses on the cyclic sway test of a support surface in standing at a single frequency. Although it is known that the balance strategy varies with the frequency in this test, there is no rational explanation based a mechanical model. The purpose of this study is to investigate rational balance strategies from the sway test at 0.3 Hz and 0.8 Hz. We defined a double inverted pendulum model as a mechanical model and two dynamical modes describing the ankle joint strategy and the hip joint strategy. From the superposition of these modes, the head displacement which is one of the control target was obtained. As a characteristics of the balance strategy, we found that only the ankle strategy mode was used at 0.3 Hz. To investigate the control strategy at the frequency, the ankle joint moments were significantly smaller than theoretical values for suppressing the head oscillation. We concluded that the difference is due to the constraint of the base of support, and as a result, the head was oscillated at 0.3 Hz.

This study aims to error reduction in estimation of joint torque using wearable sensor system. The wearable sensor system consists of wearable motion sensor installing the inertial and magnetic field sensors and wearable force plate installing several compact force sensors and inertial and magnetic field sensors. The wearable motion sensor outputs the angular velocity, the acceleration, and magnetic field, and the wearable force plate outputs the 6-axis force components and the motion sensor output. We conducted the measurement experiment of gait analysis using the wearable sensor system and the optimal motion capture system. We established the compensation method of error reduction in the effect by attaching on skin and clothes. This method was assumed the effect of error elements by using the spring and damping elements. We compared the posture information of knee joint in the results of without compensation and with compensation. The analytical results of the Roll angle indicated the effectiveness of this method.

This paper presents localization of contact-type failure based on frequency down-conversion of elastic vibration by measurement of structural intensity. It is required to detect contact-type failure such as fatigue cracks and peeling in a structure. When two ultrasonic vibrations with different frequencies are input to the test object with contact-type failure, the contact condition of the failure interface fluctuates by ultrasonic vibrations. In this situation, a difference frequency component is generated in the test object. This phenomenon is called frequency down-conversion. In this paper, since difference frequency component is caused by local non-linearity, we consider that contact-type failure can be regarded as the excitation point of the difference frequency component. Using measurement of structural intensity as a method to estimate the excitation point, we propose a localization method of contact-type failure. By measuring structural intensity, the excitation point can be estimated as a source of vibration power flow. As a basic study, we performed localization of contact-type failure in a uniform beam structure. Furthermore, we clarified the relationship between the vibration mode of the difference frequency component and the detection accuracy of the failure location.

There are many contact interfaces in machines. Some contact interfaces including lubricants exist in engines and gear boxes, and they often are sliding interfaces. Contact pressure on the interfaces strongly affects machine performance. This study proposes a novel evaluation method for the contact pressure by using ultrasonic pulses. Interferences of the ultrasonic pulses which are multiply reflected on the contact interfaces are affected by thickness of gap of the contact interface, which is a thin lubricant layer in this case. The proposed method can inform us that there is spatial unevenness of their thickness on the contact area because observed interference of the pulses is sensitive to the thickness and the contact pressure. We demonstrated this method to evaluate an axial contact pressure of a roller bearing. Comparing experimental results and simulation results at 4 sampling points, it was estimated that the thickness of the lubricant layers and the contact pressure are uneven on the roller bearing. The range between the thickest lubricant layer and the thinnest lubricant layer was about 3 μm.

This paper concerns detection of contact-type failure based on nonlinear wave modulation using local standing wave generated between excitation points. The contact failure detection method based on nonlinear wave modulation improves the detection accuracy by using ultrasonic vibration of natural vibration. However, the ultrasonic vibration of natural vibration cannot be excited in a large structure. Therefore, we focused on the fact that a local standing wave is formed between the excitation points. In this paper, we perform a basic study on contact failure detection based on nonlinear wave modulation using locally standing waves. A local standing wave is formed by exciting a beam structure in which ultrasonic vibration of natural vibration is difficult to excite at two points. We indicate that it is possible to detect contact failure based on nonlinear wave modulation by using the formed local standing wave.

The piezoelectric impedance method is a structural health monitoring method that utilizes a single piezoelectric element bonded on the surface of a target structure to detect damages by interrogating the electromechanical admittance (or impedance) of the piezoelectric element. In this paper, an idea of deploying multiple piezoelectric elements that are electrically connected in parallel is investigated for the rough localization of the damage by confining the sensing region. Qualitative modeling studies based on both modal expansion and wave propagation analysis are presented, and a possibility of using two or three piezoelectric elements connected in parallel is suggested to grant the piezoelectric impedance method an ability of spatial segmentation.

A “smart gear sensor system” consisting of an antenna connected to a network analyzer and another antenna having the same shape connected to a crack detection sensor was proposed in our previous paper. The results of this previous paper have shown that the return losses of the monitoring antenna changed depending on the sensor conditions, healthy or unhealthy. However, no parameters of the smart sensor on the gear side have been identified yet even though the use of this identification for the gear failure process wirelessly is inevitable. Hence, in this study, a method for wirelessly identifying the quality (Q) factor by executing a frequency analysis using the return loss of the observation antenna is proposed. In the first place, a model denoted the magnetic coupling phenomenon between the two antennas is introduced. Next, the derivation for the expression of the return loss of the observation antenna was conducted. Since the appearance of the unknown Q parameter in this expression is realized, necessary transforms have been executed to establish a simultaneous equation of Q factor. Then, by solving this equation, solutions of Q values are obtained. Furthermore, gradient descent method has been applied to optimize the identification process of Q value. This value of Q parameter later is validated by simulation and the consequences have demonstrated that this method could efficiently identify the Q parameter of the antenna on the gear side.

The damage detection of the wire ropes is using magnetic sensors and search coils based on magnetic flux leakage testing method. In recent years, a method of detecting damage in the circumferential direction of a wire rope using installing multiple magnetic sensors in the wire rope's circumferential direction has been implemented. However, it is difficult to evaluate the damage of multiple sensor data based on their correlation. Even if a damage in front of the sensor is the same as a damage between the sensors, it cannot be correctly evaluated as the same damage. Therefore, in this study, in order to focus on correlation of sensor data obtained from a magnetic sensor array system containing multiple magnetic sensors, the continuous wavelet transform (CWT) and principal component analysis (PCA) from the detected values at the wire rope flaw detector according to experiments using a multi sensor the feature amount extracted, by performing classification by kernel support vector machine (Kernel-SVM), and consider the possibility of this method as a damage identification method for wire ropes.

Inspection of wire ropes are done mainly by visual observation. However, since the wire rope has grease or rust, it is difficult to be detected damage. Therefore, magnetic flux leakage testing has been utilized as a method to compensate for the visual inspection. Wire ropes are a complex shape. So, the leakage magnetic flux is also generated in addition to the damaged portion. This magnetic flux leakage prevents the detection of minor damage. Until now, treatment of noise was performed by using the signal processing. However, since the detection of damage buried in noise, difficult in very small damage. In this study, for the purpose of clarifying the flow of the magnetic flux of the wire rope, performs static magnetic field analysis by the finite element method. Using the results from numerical analysis, we study the angle of the magnetic sensor capable of noise reduction. Further, by performing the damage detection experiments with different angles of the magnetic sensor, performs consider whether it is possible noise reduction by changing the sensor angle. It indicated to be useful in damage detection experiment of the wire rope in the magnetic flux leakage testing.

There are a lot of street lights in Japan. Some of these street light are damaged or corroded by water or condensation in the winter. In the worst case, a street light falls down to injure person or damage a car and so on. To prevent these accidents, periodical inspection is required. Most common inspection methods are visual inspection or thickness inspection by ultrasonic sensor. Visual inspection has following problems, i.e., (1)quality of inspection depends on a inspector, (2)it takes a lot of cost and time to inspect a street light. The thickness inspection by ultrasonic sensor has problems of poor contact of sensor to a street light especially at uneven surface caused by corrosion. In this paper, we excited a street light to measure its vibration and then estimated reduction of thickness of pole for several street lights in Osaka prefecture and checked its performance. Finally, good ability of damage detection was confirmed.

Condition-based maintenance (CBM) is a maintenance program that recommends maintenance decisions based on maintenance information by condition monitoring. To apply CBM to industrial systems, it is important to diagnose condition of equipment appropriately based on the knowledge of abnormal condition of the equipment. In a nuclear power plant, however, it is quite difficult to obtain the knowledge of abnormal condition. For this reason, simulation is expected to be an effective approach to estimate conditions of equipment instead of data acquisition. In this study, we focused on and built models for a motor operated valve and a centrifugal pump, since the inspection cost is generally expensive due to the number of them in a nuclear power plant. We considered a pump-loop system and analyzed the measurement values in normal and abnormal conditions. Our analytical result reproduces the behavior of the measurement values and shows the characteristic deviation from normal condition in abnormal conditions.

Old pipes can be damaged by potential problems such as cracks. In the past, the Mihama Power Station Unit 3 accident caused deaths. As can be seen from such accidents, pipes with potential problems are extremely dangerous, and robots capable of exploring the inside of pipes are necessary and developed to prevent accidents due to pipe rupture and to find damaged parts. There is Currently, there are various types of in-pipe exploration robots, including prototypes. However, there are many things that cannot advance if there are obstacles in the tube or they are not circular. In addition, there are many individuals with external power sources, and their free behavior within the jurisdiction is limited, and many have narrowed their range of action. Therefore, we thought that it is necessary to have a mechanism that can accommodate changes in the shape of the pipe and that can move without being supplied with power or resources from the outside, or a mechanism that can afford a battery. Based on these, we have developed a moving mechanism in a pipe by combining a valve and a telescopic mechanism. And we made a prototype using a 3D printer. Then, the operation in the pipe was confirmed.

In recent years, there is concern the increase of the deteriorated public infrastructures and plants constructed during the high economic growth period in Japan. The utilization of the robot technology will be expected for inspection of infrastructure/plant. In order to promote the development and spread of such infrastructure/plant inspection robots, the standard test methods that can objectively evaluate each performance are required by subdividing the robot performance. The purpose of this paper is to develop a standard test method to evaluate the visual inspection performance for the diagnosis and evaluation of deteriorations on the surface of structure such as rust and crack by the inspection robot. This paper proposed the basic design of the visual inspection test method for the tank and bridge based on the concept of the standard test method proposed NIST/ASTM. The design concept of the test piece board (200 mm square) that can reproduce various deteriorations and an example of a test field assuming a tank wall surface inspection were shown. The test piece board can be removed. The method of reproducing rust/crack and the concept of test field for visual inspection performance evaluation were described.

The development of micro power supply technologies for mobile phones and portable electronics has increased in recent years. Methods of self power generation using the vibration loads of structures have attracted attention as the power supply technologies. The purpose of the study is to develop a high- efficiency PZT generator element that utilizes the vibration loads in the support members of a structure. However, piezoelectric elements only generate power in the order of several microwatts, so improving their power generation capacity is of the utmost importance. The purpose of this research is to develop a power generation element with higher power generation characteristics and to develop an autonomous state monitoring system using this element as a power source. In this paper, we report the results of a verification test of an autonomous condition monitoring system that employs a general-purpose small air compressor as a vibration source and drives an acceleration sensor by vibration power generation using a La-doped stacked PZT element.

In the practical application of IoT in recent years, systems for detecting abnormalities of machine are attracting attention. However, these systems often use vibration sensor for monitoring machine vibration and batteries for power supply. We investigate battery free self-sensing wireless system using magnetostrictive vibration power generator. This system uses the generator not only for power supply but also for vibration sensor. By achieving this system, we can monitor vibration intensity of machine without maintenance in a low-cost way because the system doesn’t need to prepare the battery and vibration sensor separately. In this study, we measured characteristics of the generator as a vibration sensor. We confirmed the system can monitor variation of vibration intensity in a few % error under sinusoidal vibration of about 0.02-0.3 G and 60-120 Hz by experiment. Then we combined the generator with self-sensing wireless system and evaluated accuracy of the system under sinusoidal vibration. As a result, when a sine wave was excited at a certain speed and resonance frequency, the speed was calculated with an error of about 15% from the transmitted value, so it was possible to detect the change in speed. Furthermore, it was found that the speed can be calculated with an error of about 1% when converted from the transmitted waveform. As future prospects, we would like to reduce errors and improve system power.

This study aimed to develop a structurally embedded piezoelectric ultrasonic active sensor that intermittently induces ultrasonic bursts at one of the natural frequencies of the host structure, by using electric energy harvested by itself from the operational vibration of the host structure. To this end, this paper mainly focuses on how oscillation circuits to induce the ultrasonic burst coupled with the high-frequency dynamics of the host structure can be designed. A negative impedance converter (NIC)-based design of the oscillation circuit is presented, and its limit-cycle analysis is conducted by applying the describing function method to comprehend the oscillation behavior of the proposed circuit as well as its stability condition.

We propose a method to determine nonlinear parameters of small-sized practical piezoelectric energy harvester based on harmonic balance method, considering nonlinear piezoelectricity. The previous studies discussed a cantilever beam in which the piezoelectric material covers over entire structure, no mass attached on the tip of the beam, and it is connected to a single resistive load. However, such a condition was not practical. We used a cantilever beam with piezoelectric elements attached near the fixed end only and the mass was attached on the beam's tip. Firstly, we derived the governing equation of motion for the harvester based on the third-order nonlinear piezoelectric equation proposed previously. Secondly, we will determine nonlinear parameters of governing equation by using the harmonic balance method (HBM). The equation we derived replicates two phenomena observed in real device: (1) lower shift of the resonance frequency, (2) increase in the effective electromechanical coupling coefficient depending on the excitation force. We expect that our model can reproduce the actual electromechanical characteristics by using the two way coupled analysis with the non-linear circuit, which is proposed by us.

We designed a nonlinear circuit suited to the miniature autoparametric excitation harvester. The miniature autoparametric excitation harvester consists of the piezoelectric cantilever and the micro-patterned doubly-clamped beam formed by the photolithography followed by the wet-etching. The nonlinear circuit can decrease the acceleration threshold needed in the autoparametric excitation and the increased piezoelectric coupling force, combining the self-powered SECE (Synchronous Electric Charge Extraction) technique and the full wave voltage doubler rectifying circuit. Furthermore, compared with the parallel or series SSHI (Synchronized Switch Harvesting on Inductor) nonlinear circuit, the nonlinear circuit in this study showed less dependency on the resistive load, because of the SECE technique. The acceleration threshold is as low as 0.02 G, and we achieved the maximum output power of 1.2 mW at 0.3 G from the D cell size and 2 Hz frequency bandwidth.