Panel vibrations that cause acoustic radiation often have high modal density. Therefore, vibration reduction design is required. For practical vibration analysis, FEA (Finite Element Analysis) is used for modal analysis. Then the designer has to control the eigenmode which needs measures, but often depends on experience and it is desirable to have a structural design method to control the mode. Therefore, this paper proposes a method of controlling eigenmodes as one of the method. The method is combining the concept of modal analysis and wave number vector. Firstly, it is shown that the vibration modes of thin plates have specific angles of wave number vectors. Secondly, phase closure principle is applied to the waves of specific angles to reduce vibration of thin plates. Finally, this research proposes a method to devise structural modification for vibration reduction using phase closure principle. In order to confirm the validity of the proposed method, it is shown by FEM of the simple supported rectangular. The result showed that the vibration of mode group of the aim is reducing.

In the design of mechanical structure, improvement of characteristics of the transient response as well as the steady state response is important. For example, improvement of dynamic behavior of vehicle when running over a small obstacle is often investigated for ride comfort. Not only magnitude of the maximum amplitude of time history response but also the timing of occurrence may cause discomfort. In this paper, we try to control the peak timing arbitrarily, and to change the transient response by applying the sensitivity analysis by mass addition to a simple structure. As a result, it is found that it is possible to shift the occurrence time of the maximum peak based on the sensitivity analysis.

In order to investigate the vibration characteristics of the railway vehicle carbodies, some sorts of analytical models, such as a simple beam, a box-type and a finite element models, have been proposed. These models are constructed based on the equations of motions for some assumed or approximated structures. In this study, another modeling technique, without such assumption or approximation is applied. The modal characteristics of the tested carbody are estimated with use of the frequency response functions (FRF) obtained in the stationary excitation tests, and then the mass, damping, and stiffness matrices (characteristic matrices) of the carbody are identified. It is confirmed that the identified characteristic matrices properly represent the relation between the excitation force and response vibration. And also, the authors try to utilize the characteristic matrices in order to estimate the effects of certain vibration reduction devices such as dynamic vibration absorbers appended on the carbody.

Experimental modal analysis is one of the key technologies in structural dynamics analysis. When the resonance frequency is not close to the measured frequencies, it is difficult to identify low damping characteristics due to lack of FRF data around resonance frequency. Thus, the linear fit method which is applicable to systems with very low damping characteristics is proposed in our previous study. In the proposed method, a set of linear functions with respect to the real and imaginary parts of original Frequency Response Function (FRF) is derived by canceling the residue of FRF. This paper focuses on a single-input-multi-output (SIMO) and presents a method of improving the identification accuracy by utilizing the fact that data of the same frequency can be averaged regardless of reference points by erasing the residue terms. First, the theory of identification is explained using the linear fit method and through the application of the SIMO method. Next, a simple simulation is used to validate the method. we conclude that the estimation accuracy of the overall modal parameters can be improved by the proposal method.

In this paper, applicability of Dynamic Mode Decomposition (DMD) to the extraction of modal properties of linear mechanical systems from their time-domain dynamic responses, i.e., experimental modal analysis is discussed. Of particular interest is its capability to extract modal parameters, i.e., natural frequencies, damping ratios and mode shapes, from measured time histories of displacement of discrete and distributed mechanical systems. First, theoretical background of DMD is briefly reviewed from the viewpoint of structural dynamics. It is shown that the modal parameters can be extracted from the DMD eigenvalues and the associated eigenvectors. The DMD is then applied to analytical solutions of transient response of discrete mass-spring-damper mechanical systems to discuss the applicability of the DMD to extract the modal parameters from the transient response. Furthermore, the effects of measurement errors on the identified modal parameters are discussed. With relatively large measurement errors, it is shown that DMD produces erroneous results especially for the damping ratios. Finally, DMD is applied to experimentally-obtained impulse response of displacement field of a cantilevered beam with many measurement points, and its modal parameters are extracted. It is shown that the modal parameters extracted by DMD are as accurate as the ones obtained by the existing modal parameter extraction method.

Mechanical meta-materials are the materials or structures which do not exist in nature but are artificially created to generate novel mechanical properties, such as negative Poisson’s ratio, large specific strength, negative elastic modulus, etc. On the other hand, the normal mode analysis is the method to identify the vibration modes and to understand the dynamical properties of materials. In this study, we applied the normal mode analysis to mechanical metamaterials exhibiting negative or positive Poisson’s ratio by using numerical diagonalization. As a result, we found that there exists one floppy (zero frequency) mode as well as conventional acoustic modes at smaller frequencies and optical modes at large frequencies. We also found that self-collapse behavior occurs when the uni-axial stretching is applied onto the material.

It usually takes a lot of time to evaluate fatigue characteristics of welded steel pipes by fatigue testing machine commonly used. The purpose of this study is to obtain them in a short time by using a vibration testing machine. Steel pipe specimens with a joint welded by Fiber laser or TIG welding were prepared. They were fixed on a vibration testing machine in cantilever form. The force applied to a specimen by vibration testing machine is inertial force produced by specimen vibration, and then the problem is to extend the force up to testing force which is available for fatigue. To resolve it, an additional mass was attached at the tip of the specimen, and the excitation frequency was chosen at a value around the primary bending mode using the resonance curve. The vibration tests were conducted, and the relationships between acceleration amplitudes of excitation and numbers of cycles to failure were investigated. The relationships were converted into S-N curves by using relations between acceleration amplitudes and stress amplitudes. The S-N curves had a good correlation with the test results got by a regular fatigue testing machine. It was concluded that differences in fatigue characteristics of welding methods used in pipes could be evaluated in a short time.

A fishing-line artificial muscle, which is made from a polymer fiber, contracts by heating under load weight. The amount of contraction depends on the size of the load weight. In this paper, we investigate the optimum load weight by which the largest contraction of a fishing-line artificial muscle exhibits. In the experiment, self-coiled type and mandrel type artificial muscles are tested. Different results depending on the types of actuators and on evaluation criteria are observed.

This paper discusses the relationship between the characteristics of a flexible electrode and a stress distribution. We used the high-speed polarization camera to visualize a generated stress distribution of a dielectric elastomer actuator during an actuation. Carbon nanotube and acrylic rubber were used to make a flexible electrode and an elastomer film, respectively. In this experiment, by comparing a stress distribution due to the electrode orientation, it was investigated how electrode orientation affect a stress distribution.

Nylon fiber actuators, that can be manufactured by twisting nylon fibers and annealing them, has been researched. Meanwhile, since the manufacturing process is manual, the performance of the actuator varies. To reduce the variation in the performance of the actuators, we have developed a twisting machine that simplifies the manufacturing process of the actuators. The twisting machine has three motors, and by controlling these motors, nylon fibers are twisted while being kept constant tension, and wound on a bobbin. In this paper, we report that a large actuator can be manufactured with the twisting machine. In addition, we investigated how much the difference in displacement or force occurs during driving between a part of the manufactured large actuator and an actuator manufactured by the existing established method. From the results of these experiment, it was suggested that fabrication with the twisting machine could improve the positioning accuracy of the actuator.

This paper presents a robot hand using shape memory gel (SMG) and wire-driven mechanism. The characteristic of SMG depends on its temperature. The hot SMG is soft and cold SMG is rigid. The SMG links of the robot hand become soft and rigid depending on their temperature. The hand is designed so that 32 2-DOF joints of the hand can be bent by 16 motors. The wire winding mechanism is downsized so that the robot hand can be attached with the robot arm. The experiment using the robot hand attached with the robot arm is performed to show the effectiveness of the robot hand.

Compact and lightweight actuators have attracted attention for the human-machine coexistence society. However, these actuators based on conventional mechatronics mechanical elements such as motor make mechanical noise.. In this work, we propose an actuator driven by ElectroHydroDynamics(EHD). EHD is a fluidic phenomenon coupled with electrochemical reaction that can induce pressure through the application of a high-intensity electric field. The pump driven by EHD doesn’t make mechanical noise because of it doesn’t have drive part. Various EHD pumps have been developed in previous research, but all of them were not able to used any devices because of output pressure was not high. We succeeded in developing a pump driven by EHD increasing pressure by changing the electrode structure, fabricated by using a 3D printer and a cutting plotter. We obtained the pressure of 3458 Pa of EHD pump applying 8kV. EHD pump which we made was able to make approximately 9 times the output pressure campared to conventional.

In order to realize a vibration suppression of flexible structures like a membrane, we focus on introducing a smart structures technology to the membrane structure. In this study, a vibration control system using a DEA as an actuator for the membrane structure is proposed. A non-contact vibration test system using a high power Nd: YAG pulse laser for producing an ideal impulse excitation and laser Doppler vibrometers for measuring the response on the membrane is used for evaluating the vibration characteristics of the smart membrane structure. DEA is flexible, light and stretchable, and so it is suitable to be installed on the membrane structures as an actuator. Considering applications of DEA as space structures, a vacuum chamber is used in the control experiments. To confirm the effectiveness of the proposed method, the control experiments with H_∞ control for reducing multiple modes vibration are conducted in the vacuum chamber. It is verified by this study that the present active control method combined with the passive control mechanism due to DEA’s damping effectively suppresses the vibration responses of the membrane structure in wide frequency range.

We performed firmness assessment of pawpaw fruit by a non-contact and non-destructive vibration test. A laser-induced plasma shock wave generated with a high-output Nd: YAG pulsed laser is applied to pawpaws as a non-contact and non-destructive impulse excitation force. Vibration responses of pawpaws were measured using a laser Doppler vibrometer during the laser excitation. We succeeded to obtain natural frequencies and their mode shapes (₀S₂ mode) of pawpaws by experimental modal analysis. Relationship between natural frequencies (₀S₂ mode) and storage time has been revealed.

Machines made of compliant materials, such as soft robots and wearable devices often require to detect large strains for estimating and controlling their states and deformations. Highly stretchable strain sensors, especially those rely on reading the capacitive change as a function of strain, are a promising solution for the sensing of soft machines. In this contribution, a method to increase the sensitivity of capacitive strain sensors is described, which is to use auxetic structures. Sensor prototypes made of elastomeric materials are fabricated and tested. The result shows that the sensitivity can be improved by our method.

More attention has been paid to wave energy as a renewable energy source and its possibility has been studied for decades. To increase the power generation performance of a point absorber wave energy converter (WEC), the WEC with a tuned inertial mass (TIM) mechanism has been proposed and its effectiveness has been shown by the authors. The TIM mechanism was originally developed as a passive vibration control device for building structures subjected to earthquake loadings. The TIM is composed of a tuning spring, a rotational inertial mass, and a damping element such as a motor. This mechanism can increase the displacement of the damping part by taking advantage of the resonance effect of the tuning spring and the inertial mass, which results in a significant increase in power generation. To achieve further improvement, in this paper, static admittance (SA) and performance-guaranteed (PG) controllers proposed in the literature are applied to control the current into the motor for the WEC with the TIM. Numerical simulation studies under random sea waves characterized by JONSWAP spectrum are carried out to verify the advantages of a point absorber with the TIM over the conventional point absorber. Then, it is verified that the PG controlled WEC with the TIM shows even better power generation than the other approaches.

We experimentally validate the properties of piezoelectric energy harvester connecting to SSHI nonlinear circuit and derive an equation of motion for the practical piezoelectric energy harvester, considering nonlinear stress. The previous study did not discuss how the nonlinear stress affects the electromechanical properties for the harvester connecting to the SSHI circuit, while the SSHI circuit is likely to increase piezoelectric damping force. This study uses cantilever beam harvesting device, and parallel bimorph piezoelectric elements. Firstly, we obtained the equation of motion for the harvester based on the nonlinear piezoelectric equation proposed previously. Secondly, we investigated the impedance matching and frequency response experimentally. In the impedance matching, the rate of increase in the output power for SSHI circuit, compared to the standard circuit, decreased as the acceleration level increases, and the peak of the output power shifted to low electrical resistance. In the frequency response, the experimental result showed that the resonance frequency decreased as the acceleration increased. The derived nonlinear equation predicted these phenomena, therefore these results are most likely due to the effects of nonlinear stress.

One of the most significant issues for resonance-type vibration energy harvesters is their narrow operation bandwidth. In order to provide them an ability to tune themselves to the frequency variation, a variable stiffness cantilever oscillator that uses an electro permanent magnet (EPM) to change its effective length is proposed in this study. , The EPM, which consists of two different kinds of permanent magnets with different levels of coercivity, connected by iron yokes, and a magnetization coil, can turn its holding force on and off by reversing the magnetization of the magnet by activating the magnetization coil with a current pulse. Thus, by placing the EPM in the middle of a cantilever, a tunable oscillator can be realized which can change its natural frequency low to high. It is also described that there are two statuses of the activated EPM, i.e., fully activated (FA) and partially activated (PA), and the holding force of the latter can be much weaker than that of the former. Frequency sweep excitation tests are conducted to show that the oscillator shifts its resonance peak to the higher frequency when the EPM is fully activated, but does not exhibit any distinct resonance when the EPM is partially activated.

In this paper, an analysis of an energy harvesting device which converts a translational relative motion to an oscillatory motion via stick-slip motion is presented. The device consists of an L-shaped oscillator which is rubbed by a linearly moving frictional surface contacting at the tip. Preliminary studies showed that the oscillator showed variety of dynamical responses when rubbed by the surface. In this study, modeling of the oscillator as a 2-DOF system is carried out, and the equation of motion is derived via Lagrange equation. Four motion modes are defined in terms of the behavior of the tip motion, and the mode transition conditions are derived. A numerical simulation with a slow rubbing velocity and small attack angle is conducted, and calculation results exhibiting stick-slip motions similar to the experimental results are obtained.

Piezoelectric shunt damping is a technique for vibration suppression by connecting an external circuit called the shunt circuit to a piezoelectric element attached to a mechanical structure. Many previous studies consider only a single mode for designing shunt circuits. However, the vibration structures typically include multiple vibration modes. This paper inspects the gap between the design for the single mode system and implementation for the multimode systems. The Negative Capacitor (NC)-circuit, which consists of a negative capacitor and a resistor is tested. Then, we have found that the spillover phenomenon occurs on the lower frequency side in the multimode piezoelectric NC-shunt damping in the previous research. In this paper, we have analyzed the lower frequency side spillover phenomenon．

This paper presents a concise and straightforward model predictive controller for semi-active vibration control systems using piezoelectric actuators with switched inductance shunts in order to finally reduce the computational loads of the controller. Conventional studies of model predictive controllers for the semi-active vibration control systems used a general framework for designing model predictive controllers for hybrid systems and this approach leads heavy computational loads and difficulty of real time implementation. Instead of using the general framework, we focused on the characteristics of the semi-active vibration control systems and designed the concise and straightforward controller specially for the semi-active vibration control systems. The important characteristics of the semi-active vibration control systems are nonexistence of continuous input and meaningful constraint conditions and they convert the control problem into a simple combinatorial optimization problem. In the simple combinatorial optimization problem, the value of the objective function for each combination of the input can be obtained as a simple quadratic form of the current state vector and this nature helps to reduce the computational loads. Numerical simulations and experiments of semi-active vibration control of a cantilever beam using this controller are conducted and the results showed that the controller is effective especially for multi-mode excitation conditions and implementable with moderate horizon length.

This paper presents the application possibility of ionic polymer actuators to vibration control systems. Recently, polymer materials have gotten considerable attention due to their compactness and flexibility as soft actuators. They are also known as artificial muscle and they attract the communities of medicine as well as robotics because soft actuators can behave naturally like human beings. Especially, soft actuators have potential of taking over existing actuators in regard to flexibility, high power density, and compact energy source. Among various types of soft actuators, ionic polymer metal composite (IPMC), which can be activated under the low voltage condition, is used in this study. The feature of IPMC is that it bends when voltage is applied, while it can generate voltage when it is bended by an external force. The objective of this study is to explore the potential of the IPMC as a smart vibration control device. In this study, we assume relatively small structures such as precision instruments or cultural assets as target objects whose response vibration should be controlled. A characteristic test for the specimen of the IPMC is conducted and the transfer function of the IPMC is developed. A vibration control system for a single-degree-of-freedom (SDOF) model subject to seismic loadings using the IPMC controlled by the LQG (Linear-quadratic-Gaussian) controller is designed. Through numerical simulation studies, the possibility of the IPMC in the vibration control field is shown.

This paper is concerned with active vibration control aiming at the minimization of vibrational energy of a flexible beam. The purpose of the paper is to present the methodology of designing the smart sensor in which the reduction of its output results in the minimization of the vibration energy. Firstly, this paper begins with the derivation of an ideal feedforward control law for minimizing the vibration energy. This is followed by the derivation of the control law for minimizing the smart sensor output. Next, shaping function of smart sensor such that the control law for minimizing the kinetic energy is coincident with that for minimizing the smart sensor output is numerically designed. Numerical simulation on adaptive feedforward control in conjunction with the desined smart sensor is finally conducted. It is found that if the disturbance is pure tone, the kinetic energy is minimized by the proposed method. On the other hand, if the disturbance is a white noise, the control effect deteriorates compared to the case of the sinusoidal disturbance. This is caused by instability of the ideal control law for minimizing the kinetic energy.

This study experimentally investigates the electromechanical properties of self-powered synchronized switch damping on inductor (SP-SSDI) technique, varying the applied acceleration level. As the acceleration level increases, the resonance frequencies of the open-circuited piezoelectric plate shifted to lower frequency and the distribution of the frequency response started to show asymmetry. For the SP-SSDI, as the acceleration level increases, the damping performance enhances. The reduced equation of motion of the piezoelectric plate, which is established based on the linear piezoelectric constitutive equation and is widely accepted, cannot predict these phenomena. We introduced equation of motion from the nonlinear piezoelectric constitutive equation, including the nonlinear stress and the product term of the electric field and the stress. Qualitatively, the resonance frequency shift, the asymmetric distribution, and the enhancement of the damping performance can be explained by using the equation of motion. We assume that the nonlinear stress and the product term of the electric field and the stress in the nonlinear piezoelectric constitutive equation is more likely to trigger these phenomena.

This paper presents the new detection method of contact-type failure based on nonlinear wave modulation utilizing ultrasonic vibration driven by self-excitation. It is difficult to detect contact-type failure such as fatigue cracks and peeling in the structure. The constructional element of infrastructure is excited by environmental disturbance or forced excitation. In this situation, the contact condition of the failure fluctuates in synchronization with vibration. Amplitude and phase of ultrasonic fluctuate in the vicinity of contact-type failure. This phenomenon is called non-linear wave modulation. Detection method of contact-type failure based on nonlinear wave modulation was proposed. In this paper, the new detection method utilizing ultrasonic vibration driven by self-excitation. Firstly, nonlinear wave modulation can be expressed by linear time-varying system caused by fluctuation of natural frequency. We have developed a self-excitation method that oscillates at the natural frequency and changes the excitation frequency following the natural frequency fluctuation. Frequency modulation occurs in nonlinear wave modulation using self-excited ultrasonic vibration. This frequency modulation is considered to be an evaluation index of the level of failure. The detection experiment of contact type failure using a beam structure was performed. It oscillated at the natural frequency, and it was confirmed that the frequency modulation occurred according to the natural frequency fluctuation by the nonlinear wave modulation. Furthermore, the influence that the amplitude of the subsonic vibration gave to a frequency change and confirmed that it became the damage index is investigated.

In this paper, we propose a new system identification method of space structures. Considering operations of space structures, excitation force is usually unmeasurable and unknown. Instead of measuring excitation force, voltage of a piezoelectric transducer that is installed to the space structure is measured. The piezoelectric voltage can be used as an input signal to the structure because it is proportional to the force generated by the piezoelectric transducer. We consider that the excitation force can be represented as unknown periodic functions that are handled as an internal state of the system. Then, system identification is enforceable without measuring the excitation force. Also, two improvements are achieved in general system identification theory in this paper. First, we consider about uncontrollability of the system. The system that deals with the excitation force as internal state has some uncontrollable parts. Second, we introduce a forgetting factor to the sequential system identification theory, which is effective when characteristics of the space structure can be changed. We present performances of the proposed method in the numerical simulation. The simulation result shows that system identification can be implemented measuring the piezoelectric voltage without measuring the excitation force. In addition, it is showed that the proposed method adapts quickly to the change in structural condition.

Taguchi Method (Mahalanobis-Taguchi system) is widely used for fault detection of complex systems and industrial products including applications in Space Engineering. In this research, we focus on the Mahalanobis Taguchi (MT) system, and apply it to the fault diagnosis of adaptive space structures with advanced functions such as high precision shape control and vibration control. In this paper, we apply the Taguchi Method to the self-diagnosis problem that detects the failure in the smart structure using the random vibration response data, and verify its usefulness experimentally.

This research aims to construct a dynamic model of rolling resistance for wheelchair tires. The tire was modeled as an elastic body. It is considered that no slip originally occurs between the tire and the road surface. The relative displacement caused by the speed difference is thought to cause slippage. However, we thought that the circumferential spring of the tire worked so as not to cause slippage by shear deformation. I think that shear deformation occurs as rolling of the tire. Simulation of the rolling resistance force showed that the tendency to the vertical displacement of the tire was consistent. However, the calculated value of the rolling resistance force was 10 times larger than the measured value.

This paper describes measurement and evaluation of transferring movement in order to develop a simple assist tool for caregiver. The assist tool is a transferring board installed at the bed side and supported the transferring movement by slipping on the board. A motion capture apparatus, an electromyography device and a pressure-sensitive contact film were used to measure dynamic characteristics of human body balance for the transferring movement. It was experimentally evaluated by the comparison between the normal and the assist tool board for transferring movement. As a result, the assist tool board improved the dynamic balance of the caregiver during transferring movement and reduced the physical load on the caregiver.

In general, above knee prosthesis cannot generate extension torque at knee joint. It is difficult for wearer of above knee prosthesis to walk upstairs, in addition the burden on the other leg and waist is increased. On the other hand, above knee prosthesis that able to extend knee joint is expensive and heavy and need battery charge. We developed an inexpensive above knee prosthesis, which can prevent knee buckling during the stance phase and assist stairs climbing. It is named above knee prosthesis with a fix/extension mechanism. This study evaluates braking force for several small-scale brake, including disc-brake, band-brake and dram-brake, which is necessary to prevent buckling. This experiment show that dram-brake can generate larger braking force and is more suitable for knee joint brake than disc-brake because of self-servo effect of the structure of the dram-brake. Therefore, our current above knee prosthesis with a fix/extension mechanism is improved by using dram-brake. The current above knee prosthesis and the previous version are examined experimentally. The fixing motion of the previous knee joint brake needs larger ground reaction force, which delay the timing of knee joint fixing and cause unstable gaits. The current knee joint brake can work quickly, which can improve gait stabilization.

This paper presents new vibration control system considering psychological state of drivers. Low-speed vehicles such as ultra-compact vehicle have problems of ride comfort. In order to improve the ride comfort of ultra-compact mobility, we had proposed active seat suspension to control a vibration of seat section. In addition, it is possible that the vibration is controlled considering psychological state by the active seat suspension. It is necessary to improve the ride comfort by controlling the vibration in consideration of the psychological characteristics of the occupant against the vibration. Therefore, vibration control system using bioinstrumentation was experimentally investigated effects to ride comfort. This system switch ride comfort using psychological state analyzed in constant interval. The electrocardiogram was used to analysis for ride comfort and fed back to control system in this paper. Psychological state of driver was improved by switching ride comfort considering electrocardiogram.

Falling is a common problem in the growing elderly population and fall-risk assessment systems are needed for community-based fall prevention programs. In particular, the timed up and go test (TUG) is the clinical test most often used to evaluate elderly individual functional mobility in many clinical institutions or local communities. To evaluate the functional mobility during the TUG, some walking parameters such as stride length, step length and step width have to be measured. This paper presents a gait measurement system using a laser range sensor (LRS) (Laser-TUG system) for evaluating functional mobility in the TUG. The system tracks both legs and measures the foot contact positions to obtain walking parameters. However, both legs might be close to each other and one leg might be hidden from the sensor. This is especially the case during the turning motion in the TUG, where the time that a leg is hidden from the LRS is longer than that during straight walking and the moving direction rapidly changes. These situations are likely to lead to false tracking and deteriorate the measurement accuracy of the leg positions. To solve these problems, a novel data association method considering state transition of gait phase and leg observation from an LRS is proposed. In addition, to keep multiple hypotheses over multiple time steps, the proposed data association is applied to Rao-Blackwellized particle filter. We verify the proposed method for TUG tests with elderly people.

Low back pain of workers is increased in workplaces that involve hard work. It is caused by excessive loading of the waist joint and muscle fatigue. Therefore, power-assist suits have been developed to decrease the load on the waist joint. However, previous power-assist suits have had problems such as low output or heaviness. Thus, we have developed an assist suit that is lightweight and exerts a large force. Artificial muscles are attached to assist suit as the actuators. The assist suit has various desirable features: lightweight, flexibility, and high output. The assist suit is developed to reduces lumbar load in lifting. The assist suit prevent low back pain by limiting assistance actions in the unreasonable posture that is the cause of low back pain. Finally, the assist suit is evaluated by measuring the surface electromyography (EMG). The EMG of the wearer is compared with that without the suit. The effectiveness of the assist suit is confirmed by a decrease in EMG.

For preventing movement disorder the rehabilitation equipment was developed utilizing bellows actuators. The equipment for foot was produced and tested. The equipment was able to assist the motion of the ankle joint and toe joint. The developed power assist foot uses a resin bellows as an actuator, and by contracting and extending this bellows pneumatically, it assists the joint motion of the toe and ankle, i.e., dorsiflexion and plantarflexion. It also assists in inversion and eversion. It was shown that the developed power assist foot had an effect of improving blood flow, because the effects of the muscles becoming soft and eliminating swelling were remarkable.

The objective of this study is to develop a wheelchair which can be used a toilet independently. It is evaluated the estimated possibility that this wheelchair is used in daily life for people with physical disability and elderly people. The feature of this wheelchair is that the seat surface has a hole of the same size as the toilet seat. Accordingly, it supports for a person to excrete by the sitting down state on a wheelchair.

The evaluation of possibility for using for a long time is used 7 stages of rating scale method by subjects’ introspection, then, the usability of this wheelchair is inspected. The subjects of evaluation of seating comfort are 25 healthy male students. The subjects for measurement of sitting pressure during 30 minutes, are 2 healthy male students. The evaluation result of seating comfort indicated high score about the posture maintenance. On the other hand, the result of the hardness of the seat surface indicated the lowest score. The each score of the easiness of sitting down, the long sitting time and the pain was moderate. 2 subjects had unwell feeling about their body and felt a pain on their buttocks during the 30 minutes’ sitting. The sitting pressure during the time process indicated the tendency which rises pressure on a hip joint.

As a result, the developed wheelchair is found out difficulties to use in a daily life for a long time. However, it's possible to use it temporarily for assistance at hospitals and social service facilities. In conclusion, it revealed that this wheelchair can be reduced assistant persons’ hard task to help at the scene of toileting activities.-

Mechanical stimulation is known to increase bone mass and density through the cells’ biochemical response. It was reported that proliferation and differentiation of cultured osteoblasts were promoted by mechanical vibration and the effects were depended on the frequency. However, the relationship between this result and the influence of sloshing of culture medium was not fully investigated. In this study, frequency-depended effect of the mechanical vibration was investigated under the condition where the sloshing is small enough by using a small diameter culture plate. Osteoblast-like cells were culture for non-vibration groups, 12.5 Hz, 0.5 G groups and 50 Hz, 0.5 G groups. The vibration groups were cultured under the vertical vibration for 24h/day. To observe the effect of proliferation, the number of cells was obtained. To observe the effect of differentiation, the area of mineralization was observed by alizarin red staining. As a result, the mechanical vibration of 12.5 Hz and 50 Hz both caused an increase in saturated cell density and a decrease in the time required for mineralization but there is no dtaistical difference between the effect of 12.5 Hz and 50 Hz. Comparison with previous studies, there is a possibility that frequency dependent effects of proliferation and differentiation may be attributed to sloshing.

The brain is exposed to light, magnetic field, chemical stimulation, and mechanical stimulation. These stimulations affect neurons constituting the brain. Neurons are known as their stretching axons and the information transmission in the brain is conducted by them. Action potentials generated by the information transmission are measured as brain waves and are used to study brain activity. They are classified according to their frequency range and the frequency range from 26 to 80 Hz is called the gamma wave region. The gamma wave region are regarded as coordinating the activity between the nerves. Recently, it had been reported that the visual stimulation of light (60W, 40 Hz) excites the gamma wave region in the brain and that mechanical vibration promotes the proliferation and the differentiation of neural stem cells. We thought there are relationship between mechanical vibration and neurite outgrowth. Our goal is to verify the effect of mechanical vibration on neurite outgrowth. In this study, we used PC-12 which are also used to study signal transduction, differentiation, survival and proliferation mechanisms as they respond to many growth factors. We gave vertical sinusoidal considering medium sloshing to PC-12 and obtained that mechanical vibrations at 25 Hz (gamma wave region boundary) and 40, 50 Hz (gamma wave region) significantly suppressed neurite outgrowth compared to the non-vibration group. Compared with the previous report, it was concluded that shear stress resulting from sloshing promotes neurites and mechanical vibration may suppress neurite outgrowth.

The formation of a force field in the living body can be useful for medical treatments. For example, when we apply mechanical stimuli to cultured osteoblasts at a low frequency such as 12.5 Hz, the cell proliferation becomes promoted. On the basis of the evidence, mechanical stimuli are expected to promote the healing of fracture. There is acoustic holography as a means of forming a force field noninvasively in the living body. Acoustic holography is a technique of forming an arbitrary-shaped force field in a space by the phase control of waves from each ultrasound transducer. In this study, we simulated sound pressure distribution when we used the device which uses acoustic holography and then checked intensity and size of stimuli. As a result, we confirmed the device can give so large stimuli that affect the living body. Furthermore, we confirmed spatial resolution of the device is smaller than ones of existing devices.

Nowadays, innovative therapies for tissue engineering and regenerative medicine have been created and a large number of cells with high viability are cultured for these therapies. In the cell detachment method with common protein-degrading enzymes, the cell membranes are damaged at the detachment. On the other hand, the cell detachment method with ultrasonic vibration can detach without damage of cell membranes. For instance, the adherent cells on the culture dish are detached from the bottom of the dish by using sweep vibration without enzymes. The deformation of the culture dish, the acoustic streaming-driven shear flow, the acoustic pressure on a boundary of different materials having different acoustic impedance, and the sloshing of the liquid are candidates for detachment factor. However, details of the dominant conditions for cell detachment are not obvious. Therefore, in this study, we evaluated the effects of each factor on cell detachment from experiments and theory. As results, the deformation of the culture dish or the acoustic streaming-driven shear flow does not have sufficient force to detach the cells, while the pressure between the different acoustic impedance and the sloshing of the liquid are sufficient to detach the cells from reference. That is, these results indicate that the different acoustic impedance and the sloshing of the liquid are dominant factors for cell detachment with ultrasonic vibration.

This study covers pulmonary hypertension known as refractory disease. At present, blood flow velocity and blood pressure are measured using an invasive catheter, and pulmonary artery occlusion degree is calculated by measuring the phase difference between them. However, in recent years, noninvasive diagnosis is considered desirable. Therefore, in this research, we propose a noninvasive diagnostic method to measure the blood vessel outer diameter instead of blood pressure using ultrasonic diagnostic equipment. In the experiment using silicone tube, we confirmed that there is a reasonable difference of the phase angles between the blood vessel outer diameter value and the blood flow velocity. However, in the case of clinical data, there are some unacceptable phase angle, so far. Reproducibility is high for blood flow velocity measurement, on the other hand low for blood vessel diameter. Since the pulmonary artery is in the vicinity of the heart, the center position of the blood vessel changes due to the pulsation. So, it might be needed to eliminate the change of position of blood vessel by using other measured data in order to accomplish our noninvasive method.

The living body have abilities to adapt to surrounding mechanical situation of itself. This is because the individual cells sense the mechanical signals through the sensor called “mechanosensor” and transduce them into changes in intracellular chemistry. Although little is known about the mechanisms, “deformation” caused by static stimulation is related to the mechanisms. It was reported that gene expression of osteoblasts is promoted or suppressed by mechanical vibration as dynamical stimuli. Especially in the certain frequency, the chemical response has maximum value so that this phenomenon is the same reaction as resonance in the vibration engineering field. Now, it is considered that cells have vibration system because of density distribution of intracellular matrix and elasticity of cytoskeletal filaments. Therefore, there is a possibility that cells have natural frequencies and vibration modes. In the case of the mechanosensing to dynamical stimulation, in the same way that deformation caused static stimulation related to the mechanism, vibration modes may have also relations to the mechanism of mechanosensor. In previous study, the experimental system that could observe living cells under vibration was built and cultured cells, called MC3T3-E1, were excited and captured fluorescent images of its nucleus. However, vibration modes were not observed. Then, I changed the cultured cell from MC3T3-E1 to HeLa, derived from human cervical cancer. First, we observed HeLa has high cell heights compared with MC3T3-E1 by captured 3D images of them from confocal laser microscopy. Second, we improved the experimental system and measured vibration modes of HeLa nucleus under the frequencies of 25-250 Hz. As a result, there were no significant mechanical response.

This study shows the contribution of F-actin to sensing the mechanical vibration in mouse fibroblastoid cells experimentally. As living body adapts to mechanical stimuli from outside, cells consisting the body themselves are also found to react to them. Several experiments have shown that cells cultured under some mechanical vibration increase more than 20-30% in cell number compared with those under no vibration. After this findings, several studies have focused on the linker of Nucleus and cytoskeleton called LINC complexes and the linker of cell and extracellular matrix, namely, cell-matrix adhesion by Integrin α5β1 and Fibronectin. They show that these structures are essential factors of sensing vibration. Then, we hypothesize that cells sense mechanical vibration through Nucleus, F-actin, Integrin, and Nucleus connectivity. We especially focus on the F-actin between LINC complexes and cell-matrix adhesion during application of vibration. To assess the contribution of F-actin to sensing vibration, one of the actin polymerization inhibitors - Cytochalasin D (CD) was included in the medium of cells. Four groups, that is, with CD under static or vibration and without CD under static or vibration, were prepared. Comparing the cell number between these groups after confluent concentration state, the increase of cell number by vibration were only observed without CD. This result indicated that the organized F-actin was an essential factor of sensing vibration.

Diseases occurring near the vocal cords, such as laryngeal cancer, often cause voice disturbance as an initial symptom. As an acoustic diagnostic method for such diseases, the GRBAS (grade, roughness, breathiness, asthenia, strain) scale is widely used, but its objectivity is not well established. Instead, more accurate diagnosis may be possible by capturing the waveform of the volume velocity at the vocal cords (the vocal sound-source waveform). The aim of this study is to enable diagnosis of diseases near the vocal cords by identifying the sound-source waveform from voice measurements. In the proposed method, an analytical model of the vocal tract is used to identify the sound source. The air inside the vocal tract is modeled as concentrated masses connected by linear springs and dampers. The vocal tract shape is identified by making the natural frequencies of the analytical model correspond to the measured formant frequencies. The sound-source waveform is calculated from the analytical model by applying the measured voice (sound pressure) to the lip position of the identified vocal tract. To assess the validity of the proposed method, an experimental device was made to simulate the human voice mechanism. The device is equipped with artificial vocal cords made of a urethane elastomer that are self-excited by air flow. The sound pressure equivalent to the voice was measured using a microphone set at the lip position of the experimental device, and the flow velocity at the artificial vocal cords was measured using a laser Doppler velocimeter (LDV). To assess the model’s validity, the sound-source waveform identified from the measured sound pressure was compared with the waveform measured using the LDV.

In oral surgery using a rotary cutting tool, it is necessary to remove the hard layer on the surface of the bone and to finish the cutting before reaching the soft layer containing blood vessels and nerves inside. Currently, oral surgeons judge the end of cutting by sensing a subtle feel change of their hands when a cutting bur passes from the hard layer to the soft layer. However, it requires a lot of experience and skill. In this study, we aimed to establish a quantitative evaluation method of the change of sense felt by the surgeon before and after reaching the soft layer. First, using an accelerometer attached to the handpiece and a dynamometer attached to the jig holding a bone test piece, we constructed the experimental device to measure the vibration and cutting force of the handpiece. Next, the changes in the amplitude and frequency of vibration and cutting force were investigated when the cutting bur reaches the soft layer. As a result of bone cutting test by the oral surgeon using animal bones, it was confirmed that the vibration amplitude of the handpiece increased when the cutting bur passes from the hard layer to the soft layer.

We designed and developed a real simulator that can analyze the dynamic behavior of the machine operator-working machine-rough terrain system for a crawler crane, which is a typical crawler type working machine used on rough terrain. Using the simulator, we conducted an experimental analysis in which beginner level operators carried out load lifting, jib luffing and turning works while avoiding obstacles. Electroencephalograms, masseter voltage and line of eye sight were measured as the operator's biological characteristics. From the basic analysis of the measurement results, we examined the system that monitors the tipping safety condition of the machine during load handling work and transmits it to the operator through a visual and auditory system. Effects of the transmission pattern of the tipping safety condition to be monitored on the characteristics of the operation and related gaze (watching place and time) and also machine dynamic behavior were investigated. It was shown that transmitting the condition through the visual system when necessary and also adding transmission through the auditory system may contribute to ensuring tipping safety.

The percentage of old bridges over 50 years after construction has increased, and measures for aging bridges, such as early detection of damaged parts, have become urgent issues. Therefore, the authors have developed mobile robots BIREM that can run in steel three-dimensional complex environment. This robot has excellent running performance in the transition between two wall surfaces such as floor to wall and wall to ceiling, but its manual operation is difficult. Therefore, in this study, it is aimed that construction of a state feedback control system to realize the automatic travel on the transition between two wall surfaces by using a newly developed robot BIREM-IV. The authors have constructed the non-linear dynamic model that can reproduce the traveling behavior of BIREM-IV and make it possible to simulate the robot's traveling. Furthermore, the linearized approximate model has been created based on the non-linear model, as a result, a state feedback control system can be constructed based on the approximate linear model. By mounting the constructed control system on BIREM-IV, the authors confirmed that BIREM-IV can automatically pass successfully between two wall surfaces where the horizontal and vertical planes cross.

The non-destructive inspection of the wire ropes, soundness evaluation is using magnetic sensors based on magnetic flux leakage testing method. Breakage as the main damage factor of the wire rope. The breakage there is the external breakage in wire rope surface and the internal breakage in core side. However, it is difficult to determine the difference between internal and external breakage in the current test method to be performed only by the magnetic sensor. Therefore, discovering regularities from a single species of time-series data used in the abnormality detection technique, it is difficult to perform the identification of discrimination and deterioration degree of the damage factor of the wire rope is a technique for performing fault detection and prediction. In this study focused on correlation of time series data obtained from the plurality of kinds of 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 (K-SVM), and consider the possibility of an abnormally detection technology and soundness evaluation method of the wire rope. It was also prepared two types of internal breakage and external breakage as damage factor of the wire rope in the experiment. To perform the discrimination of these lesions factors were manufactured damage detection system using the multi sensor. This is a sensor array system using magnetic sensors and optical sensors. From these, as a feature amount to be used for classification by K-SVM, by comparing features derived by CWT, PCA and feature quantity derived by cross-correlation function, it shows the effectiveness of the identification of discrimination and deterioration degree of the damage factors. Also, using the derived feature quantity, performing damage evaluation of the wire rope by damage detection system using magnetic sensor and using multi sensor. It indicates that identification method used in this research and damage detection system using multi sensor are useful for soundness evaluation of the wire rope

Recently, IoT and Industry 4.0 were very hot topics, especially in diagnosis and maintenance area. Because an advanced computer simulation technique could be utilized using a standard computer, many engineer paid attention to an computer simulation based diagnosis technique, i.e., a digital twin. In this paper, a physical computer model of a magnetic brake was build by modelica language and verified its performance by a experiment at a first step of a digital twin technique. A magnetic brake has multiphysics in it, so that its computer model is composed of a dynamics model, a magnetic model and a electrical model. A modelica language was suit for this type of modeling. Finally, the computer simulation showed very close correlation with experimental data.

There are many contact interfaces including a thin liquid layer, which almost is machine oil, between two solids within machines. The purpose of this study is to evaluate contact pressure acting a thin liquid layer between two solids through measuring the liquid layer thickness. Changing the contact pressure, thickness of the liquid layer also changes. In this paper, we propose a thickness measurement method for the liquid layer using an ultrasonic pulse. In the proposed method, an ultrasonic pulse is sent from outside of one solid to the liquid layer. And we observe a reflected pulse from the liquid layer. The sent ultrasonic pulse is reflected at two boundary interfaces between the liquid and the solids several times. The reflected pulses interfere with each other, and received as an interfered pulse. When the liquid layer thickness changes, transmission paths of some of the reflected pulses expand or contract. It means that time delays of the reflected pulses also change. The interfered pulse is affected by the change of the time delay. The change of the interfered pulse is small. So we observe its instantaneous frequency to evaluate the change of the liquid layer thickness which causes the small interference change. In this study, we demonstrated the proposed method by applying it to some sample liquid layers whose thicknesses are known. To compare with the experimental results, we estimated the interfered reflected pulse by means of a numerical simulation. We discussed the mechanism of the proposed method and its effectiveness using these results. Additionally, we give a more accurate calculation method of the instantaneous frequency than existing one.

This paper introduces the design and implementation of a spherical range-scanned positioner based on a planetary gear combination. Specifically, the scanning mechanism based on the proposed positioner is proposed, allowing an installed sensor to draw a continuous spherical trajectory. What is the most important aspect from the practical point of view is to how to improve much more observable degree of freedoms and multi functionalities. For that purpose, the proposed mechanism has two-dimensional scanning capability as well as three-dimensional scanning. Moreover, the positioner is enabled to switch between three-dimensional and two-dimensional scanning. Since the proposed positioner is practically driven by a single stepper motor, it is expected to decrease the size, weight, and structural complexity of the any observation systems. Finally, we verify the validity and effectiveness of the proposed positioner through simulations and experiments.