Cell adhesion is critically important for a variety of cellular properties. However, an effective method to measure cell adhesion has not been reported yet. Here, we have designed a detachment method to detach cells by ultrasonic irradiation. To observe small amounts of cells, an ultrasonic irradiation device, which allow cell culturing in a PDMS chamber, was fabricated. In addition, an acoustic pressure probe of fiber optic type was fabricated to measure the acoustic pressure of the ultrasonic irradiated to the cells. With these devices, the acoustic pressure in the PDMS chamber was confirmed to be proportional to the applied current. Furthermore, by increasing the applied current of the piezoelectric transducer, the cells began to detach due to the ultrasonic irradiation was observed. That is, acoustic pressure of the cells in the PDMS chamber at the start of cell detachment was measured. These results provide additional insights into the physical characteristics of cell adhesion.

This paper presents detection of contact-type failure based on frequency down-conversion of elastic vibration. The detection method using linear ultrasonic vibrations or waves can detect small failures. However, it is difficult to detect contact-type failure because of transmissivity of ultrasonic waves in the vicinity of a failure. When the test object with a contact-type failure is vibrating at two ultrasonic frequencies with different frequencies, the contact condition of the failure interface fluctuates by ultrasonic vibrations. In this situation, an elastic vibration of difference frequency component is generated (frequency down-conversion). Since difference frequency component is caused by local non-linearity. The contact-type failure can be regarded as the exciting point of the difference frequency component. In this paper, the localization method by using time reversal analysis of transient vibration caused by frequency down-conversion is proposed. First, the transient response characteristic of the difference frequency component is investigated using ultrasonic burst waves. It is confirmed that the excitation time by burst waves are related to the waveform of the transient waves in low-frequency range. Second, the localization experiment of contact-type failure in a uniform beam structure is performed.

Non-destructive testing for bolt loosening which can evaluate fastening force quantitatively is needed to prevent accidents due to the bolt loosening. This study proposes an evaluation method for the fastening force of bolt-nut fasteners quantitatively using ultrasonic pulses. In this method, attaching two ultrasonic transducers on the nut, we observe the ultrasonic pulses which passes through the screw thread of the bolt. The projected ultrasonic pulse from one transducer splits into a transmitted pulse and a reflected pulse on a flank of the screw thread. The transmittance and the reflectance depend on contact stiffness on the flank between the bolt and the nut. The contact stiffness on the flanks is positively correlated with contact pressure on the flanks and fastening force of the bolt. If the contact stiffness on a flank becomes larger, transmittance of ultrasound on the same flank becomes higher. We thus can calculate the contact stiffness on the flank of the bolt-nut fastener from amplitude of the transmitted pulses which passes through the bolt. And the proposed method estimates the contact pressure of the flank and the fastening force of the target bolt-nut fastener using the calculated contact stiffness. In this paper, we demonstrate the proposed method for a sample bolt-nut fastener which consists of an M24 bolt and a nut. The proposed method provides valid results about the contact pressure and the fastening force as compared to the applied fastening torque.

There are many contact interfaces in machines, and contact pressure on the interfaces strongly affects machine performance. Some contact interfaces include lubricants, and they become liquid layers. This study proposes a novel evaluation method for measuring contact pressure by using ultrasonic waves. Ultrasonic pulse projected onto contact interface including lubricants is multiply reflected in liquid layer. This pulse changes depending on the thickness of the liquid layer on the contact interface, but the change is very small. Therefore, we tried to evaluate contact pressure by observing the instantaneous frequency and phase distribution. The phase distribution of interfered pulse has singularity point, and the point includes pulse parameter. In this paper, we proposed a highly reproducible shim ring shape first. And, we quantitatively evaluated the gap thickness using the phase distribution. Additionally, we considered the change of shim ring by finite element method and microscope imaging to confirm validity of the estimated result by the phase distribution.

A screw compressor is an important component in a factory. It works 24 hours 365days to supply air to many machines. If a screw compressor stops, whole operation in a factory stops. A screw compressor consists of many parts, i.e., bearings, screws and so on. To diagnose a compressor, effect of damage of each component by experiment or computer simulation. In this paper, we monitored several types of screw compressor and built physical models of their components by Modelica based on experimental observations. Then we showed that features of developed model well coincided with that of experiments.

In this paper, we discuss on fault detection method for a machine parts manufacturing equipment. For the fault detection, a machine learning technique is employed based on operating time data which is relatively easy to obtain. An issue to be solved is that it is not easy to obtain fault data to be detected by daily normal operation of the equipment. It is required to apply unsupervised learning techniques or prepare appropriate fault data for machine learning. In this paper, the fault data were generated from the distribution of the normal data and a multi-label deep neural network(ML-DNN) is applied to detect faults in multiple actions simultaneously. Some results show the effectiveness of the proposed procedure.

The purpose of this study is to develop an automatic attraction system for UAVs using EPM (Electro Permanent Magnet) to save labor in structural inspection. The automatic attraction system for UAVs can attract objects with a large attraction force by detecting contact by measuring the induced electromotive force (EMF). In this study, the EPM was impacted against attracted objects of various shapes, and the induced EMF generated in the coil of the EPM was measured to compare the voltage with the shape of the attracted surface. The results showed that in most cases, the larger the impact velocity, the smaller the curvature of the attracted surface, and the smaller the horizontal offset, the larger the induced EMF generated. Furthermore, it was shown that by using the voltage obtained from the results and using the automatic attraction system, the maximum speed that can be attracted is more than double compared to the case without the system.

Since electric motors (including generators) are used and play crucial roles in various industries, it is important to diagnose their conditions appropriately to avoid troubles in advance. A motor is a device that converts the electric energy into the rotational (mechanical) energy. Electric motors consist of multisystem and operate through the interaction between the magnetic field and electric current in windings to generate the torque applied on the motor shaft. So, it is effective to comprehensively diagnose the motor conditions by monitoring multi-measurement data such as vibration, electronic current and temperature etc. In this paper, we focus on a multi-physics simulation in order to diagnose the motor conditions and formulate the model of an electric motor with magnetic circuit network method to evaluate dynamic behavior including a motor shaft. Our analytical result shows the effect of mechanical behavior to electric current.

Permanent magnet synchronous motors are widely used in industrial rotating machinery such as automobiles. In this study, a torsional vibration test equipment with PMSM and two inertias was developed for basic research on torsional vibration control using a permanent magnet synchronous motor. To obtain the desired natural frequency, a plate spring is designed as torsion springs. We also obtain the frequency response from the experiment and estimate the stiffness and damping coefficient of the test equipment.

Integral resonant control (IRC) is a vibration control method in which integration of the measured displacements is positively fed back to the input force. It is necessary to know the transfer function of the control object for the model-based design of an IRC. This paper uses a piezoelectric bimorph beam used as the control object. The direct feedthrough term of the transfer function is usually positive, but we found the experimentally measured direct feedthrough was negative. This paper proposes a new model for the physical cause of the negative direct term of a piezoelectric bimorph. Even if the direct term is negative the negative imaginariness of the transfer function is not violated, and therefore stable vibration control by IRC is possible.

The metamaterial in which mechanical resonators are periodically mounted on the host structure can reduce the ambient vibration caused on the host structure by creating a bandgap in the frequency response properties. However, as a side effect, the addition of the mechanical resonators results in unwanted resonances outside the bandgap. The resonances will pose a problem in practical application because the resonances may lead to a breakage of the host structure at unexpected frequencies. To address this issue, we propose an application of a piezoelectric material and a damping circuit to the metamaterials. We also derive a coupled equation for the complex system. The analysis showed that the resonance intensities are decreased by over 70 % thanks to the proposed technique. The analysis also showed that the use of the piezoelectric material and the damping circuit will not change the properties of the bandgap. The proposed technique can compensate the disadvantage of the metamaterial using the mechanical resonators.

Currently, the main propulsion device for underwater exploration robots is screw propellers. Problems include low mobility, stopping due to feather rotation, failure, and the risk of harming living organisms.Therefore, in order to overcome the above limits, we propose a new propulsion mechanism that can be lifted and dropped. In this paper, we describe in detail the method of lifting and descending by the propulsion mechanism that manufactures and proposes a prototype. From this prototype, a series of operation controls are performed, and the effectiveness of the proposed propulsion mechanism is shown.

In recent years, IoT devices have become widespread for collecting big data, and the use of the energy harvesting using environmental vibration as a power source has attracted increasing attention. In this research, we propose a circuit for the dielectric elastomer power generator (DEG) to be used for a low voltage source. The proposed circuit, called the CW-DEG, is constructed from the 1-stage Cockcroft-Walton circuit with the AC voltage source replaced by the DEGs. Although the DEGs operated at a high voltage, the proposed circuit outputs the difference of the DEG voltages and does not require step-down by a Zener diode. We first derive the charge increment of the charging capacitor over a cycle and show that it can be approximated by a simple function of the magnitude change of the DEG capacitance. A numerical example shows that the proposed circuit produces higher charging capacitor voltage compared to a conventional self-priming DEG (SP-DEG) setup with a Zener diode.

Pipe supporting devices are very significant on maintaining not only pipe structure but also whole structure on thermal power plant or nuclear power plant. Selection and proper placement of supports is the one of the most difficult tasks on power plant design. Recently, many of skilled engineers have been retired in these areas and human resources shortage has become a social problem. Therefore, using accumulated know-how, automated pipe-support arrangement system is needed and optimization of design is also needed condensing past technics. In this study, we have developed optimization system of pipe-support combination to properly decide their position and type, using machine learning and deep learning. As a result, it is proven that machine learning and deep learning are sufficiently useful in design and their arrangement optimization of pipe-support on thermal power plant or nuclear power plant. In this study, PyCaret as a tool of automated machine learning has been used and it has been proved that LightGBM is the best algorithm.

In the authors’ previous report, a new piezoelectric cylindrical shell wind power generation flag had been proposed as a flexible and durable power generation structure that utilizes vortex excitation vibrations. Preliminary experiments showed that it was expected to generate more than 10 times more power than the conventional planar-shaped wind power generation flag. In the present flag, the cylindrical Bluff Body, which excites vortices, also plays the role of a vibrating structure. When actually generating power outdoors as a wind micro power generation device, it is not always the case that the wind is blowing from a certain direction. When considering the horizontal component of the wind, it is necessary to have a power generation device that can obtain a constant power generation efficiency for any direction of the wind, 360 degrees around the vertical axis. Since the piezoelectric cylindrical shell wind turbine flag is an axisymmetric structure with respect to the vertical axis, it can generate electricity from any direction in the horizontal plane, as long as the bending vibration of the cylinder can be excited. In this study, the effect of wind direction change on the power generation characteristics of the piezoelectric cylindrical shell wind turbine flag was investigated experimentally.

In recent years, flexible bodies such as cable have been used as part of multiboby system, for example cranes and elevators. When analyzing the behavior of these flexible bodies by the finite element methods, some elements move across the boundaries between the region which have different condition. So it is necessary to distinguish in which region each nodes exists, it makes the analysis more complicated. ALE-ANCF (Arbitrary Lagrangian Eulerian Absolute Nodal Coordinate Formulation) that previous study developed is an efficient solution for this problem because some nodes can be fixed at boundaries and other nodes can be arranged arbitrarily in each region. On the other Hand, there is a problem that the analysis accuracy is reduced when the element length changes significantly from the initial state. This study proposed a method to add or remove nodes according to the element length in order to eliminate the significant change in the element length.By analyzing the flexible body with time-varying length, this study tried to verify the validity of proposed methods.

The absolute nodal coordinate formulation (ANCF) has been widely used for nonlinear dynamic problems in multibody systems with large rotation and deformation. A distinctive feature of the ANCF is that the mass matrix is constant and symmetric by employing absolute nodal coordinates and global slopes as the element nodal coordinates. On the other hand, a mathematical description of elastic forces is one of significant topics in implementation of the ANCF due to the description with highly nonlinear terms from the standpoint of computational performance. This study focuses on the elastic forces for the ANCF shear deformable beam element utilizing strain measures based on the geometrically exact beam. Due to the mathematical descriptions of the rotation in the strain measures, numerical (spatial) integration techniques, such as the Gaussian quadrature rules, are implemented every time step for evaluating the elastic forces. The present method introduces interporlation of the rotation by polynomials with discrete rotation parameters at nodes on each element. It could contribute to reduction of computational costs regarding the evaluation of elastic forces. In addition, this study employs an augmented formulation technique based on the Lagrange’s equation for constrained systems in order to introduce the discrete rotation parameters as redundant degrees of freedom.

Crawlers are widely used as construction vehicles that require high trafficability in off-road situations. When being operated on a slope, such vehicles often slip due to skidding between the crawlers and the soil. When the posture of the front structures on a hydraulic excavator changes, the amount of skidding also dynamically changes. A highly skilled operator must deftly adjust the left and right crawlers to follow a target trajectory. Since the construction industry requires the development of assisted and autonomous technologies, a crawler-traveling simulation model on soft ground is needed. We established a traveling simulation model on a slope by terramechanics for a crawler vehicle with a changing center of gravity. The ground parameters in our simulation model were identified using the actual test data of the crawler vehicle. Then we compared the simulated, traveling results that were identified with actual vehicle experiments and verified that our simulation methodology reproduced the skidding of a crawler vehicle on off-road slopes. In addition, several case studies were performed to understand the effect of the changing center of gravity on the traveling trajectory.

It is known that snake-like robots have lower movement efficiency than four-wheeled mobile robots. Therefore, in this research, we propose a snake-like robot which can transform into a bicycle mode. Then the purpose is to improve the movement efficiency on flat ground. We have already designed a snake-like robot for stabilization analysis. In this paper, structural analysis is applied to the previously designed snake-like robot to examine whether the shape and wall thickness of each part is appropriate. In addition, since wiring cannot be passed through the infinite rotation axis, in this research, the servo motor farther than the infinite rotation axis is controlled using wireless communication. Therefore, we describe the XBee and ZigBee standards used for wireless communication, and explain the communication establishment and time synchronization through wireless communication. Finally, the program including wireless communication is implemented on the assembled snake-like robot. Then, it is confirmed that time synchronization and servo motor control are achieved by wireless communication.

Since rail corrugation causes vibration and noise as the vehicle moves, elucidation of its generation and growth mechanism is an important research subject in this field. In this study, factor that determine a frequency was investigated using an actual 1/10 scale model experimental machine and a numerical analysis model simulating the experimental machine. It is a circular type of experimental machine, which can be worn by repeatedly running on the same rail. Considering the coupled vibration of the front and rear wheels, so reproducibility can be expected in the evaluation of wear progress. From the experiment results, it is confirmed that rail corrugation of about 500 Hz occurred. The numerical analysis is also a model that can run multiple times on the same rail as in the experiment. From the numerical analysis results, it is confirmed that similar to the experimental results, rail corrugation of about 500 Hz occurred. Therefore, modeling of the vibration element of the numerical analysis model is considered to be valid. In a small range of contact amount, by assuming that the nonlinear contact force is linear, an eigenvalue analysis was performed with more accurate contact stiffness applied. As a result of eigenvalue analysis, factor that determine the frequency of about 500 Hz is considered to be the elastic contact of rear wheel when the front and rear wheels are in reverse phase.

One of the problems of high-speed railways is the phenomenon of hunting, in which the car body and bogies vibrate significantly from side to side during high-speed running. It is very important to understand the mechanism of the hunting because it not only makes the ride uncomfortable but also causes track damage and wear. In order to understand the mechanism of hunting, we model and carried numerical simulation of a two-axle bogie with a real tread geometry in a high-speed railway. In this study, the running stability of the bogie is evaluated by determining the critical speed of the two-axle bogie. When the initial lateral displacements are given as disturbances, the critical speed differs depending on the initial displacement, and the larger the initial displacement, the lower the critical speed. The reasons are presented as follows: the first reason is that the equivalent conicity of the wheel increases with large amplitude. Second, due to the nonlinear characteristics of the creep force, the creep force does not increase linearly even when the creep rate increases. Moreover, the results show that the hunting becomes a limit cycle above a certain initial displacement when given a speed below the critical speed determined by the eigenvalue analysis, and that the hunting becomes a limit cycle regardless of the amplitude when given a speed above the critical speed determined by the eigenvalue analysis.

We have conducted various tests and vehicle dynamics simulations using 1/10 model vehicles. In order to simulate the vehicle motion of the 1/10 model vehicle, firstly, it is necessary to build a numerical model system consists of springs and dampers. The frequency response is obtained from the vibration test of the model vehicle, and the parameters in the predetermined model are searched and modified to be determined as those of a numerical model. The brute-force search within a specific range is conducted using known parameters as clues in parameter identification. In more detail, some optimization methods, such as the least square method, are also used. However, in many cases, the validity of the parameters of the model is empirically evaluated by comparing with known specifications. Thus, a more quantitative method in parameter identification is desired. Therefore, we first investigate the behavior of parameters when they are optimized for the up-down system, which is relatively easy to identify empirically.

This paper describes the development of the autonomous flight system to create microgravity space. Currently, various microgravity environments are being conducted for the development in material science and combustion science because characteristic physical phenomena occur in microgravity space. However, existing microgravity generation methods have problems that experiments are only conducted in a specific place and expensive. Therefore, development of portable and low-cost system for creating microgravity space is desired. The proposed system realizes a microgravity environment controlling acceleration by a ducted fan and attitude by a motor while dropping. The study aims to design control system using backstepping method and consider motor dynamics. Also, the robustness against the change in aerodynamic force of the flap is evaluated by numerical analysis. The result of the numerical analysis shows that the proposed system controlled by backstepping method has the robustness against the change in lift of the flap.

Many studies have been conducted on the problem of suppressing residual vibration of stacker cranes for a long time, but most of the studies have been discussed by fixing either the cart or the carriage. In the previous report, the authors derived a dynamic model of the stacker crane considering the coupling of the motion and vibration, and proposed a new method to obtain a large vibration suppression effect by simultaneously operating the cart and the carriage in a coordinated manner based on the derived dynamic model. In the proposed method, the reference trajectories of the cart and the carriage were represented by the B-spline function, and the control points were optimized by the Hill Climbing (HC). However, since the HC is a local search method, there is a problem that it is easy to fall into a local minimum solution and the computational cost is large. Therefore, in this study, we try to efficiently search for a global optimum solution by applying Particle Swarm Optimization (PSO). The effectiveness and efficiency of the newly formulated algorithm are verified by numerical simulation.

This study focuses on a stabiltiy analysis for unstable phenomena such as parametric excitations and self-excited vibrations on multi-body systems. Due to a large number of DOFs and nonlinearlities, it is difficult to directly apply the general method of stability analysis to the multi-body systems. In this study, we utilize a method based on the Prony’s method that evaluates instability using time series data obtained from experiments and numerical simulations so that it can be applied to a wider range of systems such as those modeled by the multi-body systems. Specifically, this study aims to establish a highly versatile method for predicting unstable vibrations such as parametric vibrations and self-excited vibrations of multibody systems. The purpose of this study is to confirm the validity of stability analysis using the time series data obtained from the numerical simulation and to compare it with theoretical results.

In recent years, research and development of robots that exist in the same space as humans and can collaborate with humans have been actively carried out. If the body of a robot is made of a hard material, it may cause injury. Therefore, attempts have been made to make a robot with a soft body using rubber or resin. In order to accelerate such research on soft robotics, it is necessary to establish fast and stable simulation algorithm for robots containing viscoelastic bodies such as rubber and resin. Therefore, in this study, we consider to approximate viscoelastic bodies with finite rigid body segments and connect them with joints and linear viscoelastic elements such as Voigt model and Maxwell model to approximate viscoelastic properties. The recursive dynamics algorithm is used to speed up the calculation, and the generalization-α method is used to stabilize the numerical integration. In particular, we propose a new method on how to incorporate the Maxwell model into recursive dynamics algorithm and generalization-α method. The effectiveness of the proposed method is confirmed by some numerical examples.

In recent years, space manipulators have been used in various situations in space development. Arm length and multi-link of arms are increasing due to expansion of work area. Also, they have been reduced in weight and flexibility in order to restrict the weight of the launch vehicle and reduce launch cost. However, since each motor used for each axis of the manipulator requires one motor driver, increasing the number of motor drivers and the weight of the entire manipulator system are problems due to multi-linking. Therefore, this paper proposes a system that can operate with fewer drivers by switching the motor driver and the piezoelectric driver for braking on each axis. However, complex behavior occurs due to the non-smooth friction of multiple brakes, which affects the control performance. Therefore, it’s necessary to analyze and design the control system in consideration of them. In this paper, ANCF is applied to 2-flexible link manipulator and the formulation of non-smooth frictional force using LCP is introduced. Also, the behavior of the system is confirmed by numerical analysis.

The projection type iterative learning identification method has several advantages such as: (i) no time-derivatives of input/output signals are required and (ii) it gives unbiased estimations. However, this identification method requires a parameterized model obtained by projecting a tracking error signal onto a finite-dimensional subspace, and the parameterized model must be estimated in advance. The model is called a parameter space representation in this paper. This paper presents an approach for estimating the parameter space representation of a system with nonlinear friction. Its effectiveness is demonstrated through numerical example of a linear plant with nonlinear friction.

This paper considers wave analysis and control of two-dimensionally connected damped mass-spring systems. Considering two-dimensional field waves such as longitudinal vibration of plates and out-of-plane motion of membranes, mass motion in the longitudinal direction is considered. The system can be viewed as cascade connected layers composed of vertically connected elements. The system dynamics can be expressed by a recurrence formula. The eigenvalues of the coefficient matrix determine the propagation constants, and the eigenvector elements determine the characteristic admittances. It can be shown that the characteristic polynomial can be decomposed into second order polynomials, which reveals the properties of the propagation constants required for the wave analysis. It can also be shown that the characteristic admittance (impedance matching controller) is a positive real function, which guarantees the closed loop stability. A numerical example illustrates effectiveness of the impedance matching controller for vibration control.

With the real-time remote seismic monitoring system being established in several countries including Japan, a new preview-type active control system of structural systems subject to seismic disturbances has been proposed by the authors(1). The preview-type control uses the estimated future seismic waveform obtained by seismic wave data in remote observation sites and an AI-based future wave estimation system. In this study, we consider that multiplexing the preview-type control law with the remote waveform data in multiple monitoring sites improves not only the robustness of the control system in the case of the system down in some sites, but also the control performance by switching or scheduling multiple preview-type control laws. We propose a hierarchical method for scheduling multiple preview-type control laws so that the above system down does not impact crucially in carrying out the switching or scheduling control. We refer to the control method with the proposed scheduling law as the ensemble control. In the ensemble control based on the scheduling method, some schedulers to decide the switching or scheduling are needed. In this study, the schedulers are designed as artificial neural networks whose input data are the state-vector, the controlled output signal of the controlled structural system, and the available seismic disturbance, etc. We show the advantage of the present control methodology with a simulation example using a recorded seismic event.

In this study, we propose a seismograph controlled by a digital controller with state feedback control and absolute acceleration feedforward control. In this report, in addition to the state feedback controller designed in the previous research, the absolute acceleration feedforward controller was designed by frequency response simulation. These composite controllers were mounted on a digital controller to control the absolute displacement sensor. As a result of measuring and evaluating the frequency response and time history response, the target 0.1 Hz seismic wave was not reached, but the amplitude could be measured up to 224 times the movable range of the weight in the frequency band of 0.28 Hz to 1.5 Hz. This is a result that exceeds 100 times the range of motion of the target weight. However, the phase was not constant between 0.28Hz and 1.5Hz, and it was not possible to acquire seismic waves consisting of composite waves of various frequencies in that frequency band.

One of the problems of overhead cranes used for transporting heavy loads is causing long-lasting residual vibration without using dampers, which lowers safety and work efficiency. The purpose of this study is to suppress the residual vibration of the pendulum in the 1D translation type overhead crane by deciding the trajectory of the trolley by vibration manipulation function (VMF). We attempted open-loop finite-time-settling control by using VMF as a finite-time-settling function. We performed experimental works of vibration control transfer of the overhead crane by using a stepping motor to faithfully reproduce the transport trajectory calculated by VMF. Results of experiments was compared with simulations.

We perform vibration control transfer of a one-dimensional (1D) overhead crane under open-loop finite-time-settling (oFTS) control using vibration manipulation function (VMF) as reference input. A DC motor is used as an actuator of the overhead crane, and the DC motor is controlled by input signal that realizes trajectories designed along VMF. In the case of simple determination of the input signal from VMF, the experimental equipment does not move like the design trajectory due to the influence of friction. Therefore, we introduced correction terms using machine learning to modify the input signal. We have confirmed that the experimental equipment operates along the various designed trajectories with several pendulum. It was found that vibration damping transfer of a 1D overhead crane is possible under oFTS control with VMF as a reference input.

Compact vehicles manufactured for personal use, called personal mobility vehicles (PMVs), are becoming used commonly. PMVs include the inverted pendulum vehicle, sitting-type PMV, and standing-type PMV. In recent years, the automatic driving of vehicles has been expected to simplify driving operations and to correct erroneous maneuvers. Automatic driving levels range from 0 to 5, but Level 1 supports either acceleration/deceleration or steering. In this study, we investigated the effect of the vehicle trajectory on driver’s steering behavior. According to the past research, in the case of the driver’s intentional steering, we found that the driver’s center of gravity (COG) moved in the opposite direction to the centrifugal force before turning, which stabilized the driver’s posture. This study aimed to evaluate the driver’s behaviors during automatic steering that reproduces the preliminary movement by vehicle trajectory. As a result, the driver’s COG movement before turning has middle correlation with the vehicle trajectory.

In this study, we estimated joint moments of drivers of a stand-up type personal mobility vehicle (PMV) in order to simulate their behavior during turning, considering their intentions. First, we measured human behavior, handle reaction force, and floor reaction force using motion capture, a six-axis force sensor, and a reaction force meter attached to the foot in a vehicle experiment. From the obtained external forces and human behavior, the joint moments of the drivers were calculated using inverse kinematic analysis and inverse dynamic analysis. As a result, it was found that the joint moments of the spine were large, so regression analysis was used to estimate the joint moment of the spine. As explanatory variables for the regression analysis, joint angle and joint angular velocity were used in the conventional model, and joint angle and joint angular velocity, yaw rate, vehicle speed, acceleration, and jerk were used in the new model. As a result, the value of the adjusted R-square R^f₂, which indicates the accuracy of the model, was larger for the new model than for the conventional model. However, the values differ among the drivers. Then, one of the challenges is to increase the data and consider the behavior patterns.

This work offers an active damping technique for automotive drive systems with backlash and uncertainty on the update timing of control input due to the control cycle limitation. The backlash existing in gears of automotive drive systems induces undesired transient vibration characteristics, which deteriorate the riding comfort, when a driving torque becomes a step signal. Furthermore, in an engine employed for the vibration control, the mechanical process to generate torque makes the control cycle time-varying, resulting in uncertainty on the update timing of control input. Consequently, an active damping technique to compensate for the update timing should be important. To compensate for the maximal phase delay of the control input caused by the time-varying control cycle, the predictive processing utilizing the sampled-data controller and the unscented Kalman filter (UKF) is employed. As the main result of this paper, a fuzzy inference is introduced into the previous approach to cope with the uncertainty on update timing of control input. This paper presents the basic idea of the compensation with two fuzzy inference rules. Finally, to confirm whether the proposed idea can suppress the vehicle body oscillations, a basic simulation verification is conducted.

Advances in image processing technology have made it possible to measure the surface shape of the road ahead while driving. We propose a new semi-active suspension control method that considers the forward road surface shape. A vehicle model equipped with a semi-active suspension can be expressed as an MLD (Mixed Logical Dynamical) model. When the shape of the road ahead can be measured accurately, it can be considered that the information on the future disturbances is available before the vehicle undergoes. In this paper, we formulate the finite time optimization problem of the MLD model in consideration of the future disturbances as a MIQP (Mixed Integer Quadratic Programming) problem in the same way as the conventional optimal control problem without future disturbance. The solution to the MIQP problem can be obtained by a commonly available solver software. The performance evaluation of the proposed method was carried out by a simulation, and the simulation was performed on the road surface shape generated by the road surface shape generation method based on ISO 8608. In the simulation study, the proposed method was able to achieve better ride quality, i.e., a smaller suspension stroke compared to the traditional MLD predictive control and the Skyhook approximation methods.

Japanese society is rapidly aging, and its birthrate is low, leading to a reduction of the working population. Therefore, industrial robots are increasingly expected to serve as substitutes for human beings. Conventional teaching methods with robots include remote teaching and direct teaching. These teaching methods have problems in terms of difficulty teaching sensibly and teacher safety. In order to solve these problems, sensuous but remote teaching is ideal for the teacher. In this research, We propose a remote and sensuous teaching system by inertial sensors. We extracted the target position and posture information of the robot to be taught using inertial sensors and applied our system to the actual robot. In this paper, We attach one inertial sensor to trapezius, upper arm and forearm to estimate the trajectory of the wrist. And the 6 DoF robot arm remote teaching system was built. To verify the effectiveness of this system, wrist estimation position accuracy verification experiment, trajectory following experiment, position control experiment, and comparison experiment with other teaching device have conducted. As a result, the effectiveness of remote teaching system by inertial sensors was shown.

In this study, we performed analytic studies and simulations for damping rotations of a two or three-joint horizontal rotational robot arm in rest-to-rest motion as a model of flexible arm. They were controlled under open-loop finite-time-settling function termed vibration manipulation function. From an analytic study of a horizontal one-joint robot arm, damping rotation is possible in any operational period. Along the study of a horizontal two-joint robot arm, simultaneous damping rotation of two vibration modes is possible by choosing specific discrete operation times. Since a flexible arm with two weights can be approximated to the two-joint robot arm, it was verified by experiments whether the residual vibration of the flexible arm is suppressed by the same rotational operation. The longer the operation time was, the more residual vibration was suppressed. In addition, we deduced the condition of the simultaneous suppression of three modes in a horizontal three-joint robot arm. It was found that simultaneous damping rotation of the three-joint robot arm is realized under its specific design and specific operational period.

Japan is one of the most earthquake-prone countries in the world, and robots with a variety of mobility methods are used in disaster situations. However, the environment in which robots operate at disaster sites differs from that of everyday life in that there are many obstacles and the space in which they can move is narrow and limited. In addition, the footholds are unstable, and there are only a limited number of mobility methods that can respond to the situation. For this reason, small flying robots are considered to be effective in carrying out missions. Therefore, we focus on the flight of insects, which are small and agile in nature, and develop a flapping mechanism with two wings. This flapping mechanism is based on the flapping motion during hovering in order to realize the flight of two wings. The effectiveness of this mechanism will be demonstrated by conducting experiments using a prototype.

We live in Japan, an island nation surrounded by the sea. Therefore, fishing and commerce using ships are indispensable. However, there are times when ships run aground or collide accidentally. The impact of such accidents can cause heavy oil to leak from the ship into the sea. Therefore, it is thought that the presence of a heavy oil collection mechanism that can be moved quickly will make it possible to collect heavy oil efficiently. In this study, we propose a spherical propulsion mechanism to collect heavy oil leaked into the water due to accidents.

A kind of an air cushion vehicle (ACV) is known as a hovercraft which carries out a cruise by blowing off the air from the bottom of the body. The ACV has many advantages, such as amphibian vehicle, large payload, and so on. However, the ACV has drawbacks such as its drivability is bad. An improvement of the drivability is effective for the control of the ACV and the disturbance rejection performance of the controller is very significant. In this research we make an estimation method for the radius of curvature of the target trajectory with an image sensor. Using various sensors and image processing technologies, we get the control values which are required for controller. We verified usefulness of the proposed methods by driving experiments.

Although a snake-like robot can move in fluid as well as on the ground, it has to drive many actuators. Then it is necessary to reduce the power consumption and improve the moving efficiency. Also, for a planetary exploration, a snake-like robot must move in the environment such as not only water but also mud and clay by undulating locomotion. Therefore, the snake-like robot needs to adapt to changes in the environment and change undulating locomotion to maintain its moving efficiency. For this purpose, we focused on organisms that changes undulating locomotion in response to change in kinematic viscosity. In particular Caenorhabditis elegans (C.elegans), a type of nematode, can change undulating locomotion significantly compared to other organisms. Then we aimed to construct the numerical model of a snake-like robot that imitated the behavior translation of C.elegans. First, the numerical model of the snake-like robot whose swimming frequency changes according to the kinematic viscosity was constructed. Second, we performed experiments of the snake-like robot with 8 links swimming in three kinds of fluids, water and two kinds of oil with different kinematic viscosities, and measured the joint positions of the snake-like robot during the swimming motion. As a result, we obtained experimental results showing the same tendency as C.elegans.

In the airport, the conveyor sorter carries and sorts passenger’s baggage. As the speed of this sorter increases, many problems such as energy loss, noise, vibration, and wear occur. In this research, we apply magnetic levitation (maglev) technology to this sorter to solve these problems. First, we designed a magnetic support device using a finite element method of magnetic field analysis and manufactured this maglev unit. We could apply this unit to the existing cart of sorter without significantly changing its structure. Next, we manufactured a maglev suspension force measuring device and measured this force. Although the suspension force was lower than the analysis value, we clarified that this unit could support the sorter and baggage. We mounted the maglev unit on an actual cart and carried out the maglev control. To clarify the dynamic characteristics of sorter, we measured the time response when we changed the levitation position and when a load was applied. According to this experiment, we clarified that the maglev unit could support the weight of general baggage.

We introduce a control method of a magnetic levitation system (Maglev) suspended by an elastic element. A Maglev conveyance system has the merits of high efficiency and maintenance-free. Usually, the guide rail of the Maglev conveyance system is considered as a rigid structure, and its deformation and vibration are ignored. To reduce the weight and cost of the guide rail, we investigate a control method in the case of the flexible guide rail. In this paper, a one-degree-of-freedom Maglev system suspended by leaf spring is experimentally studied and stable levitation is achieved. The experimental device and the results of the levitation tests are shown.

High magnetic rigidity is required to optimize superconducting levitation. We proposed a hybrid stator comprising a superconductor and permanent magnets for improving levitation stability. In this study, we measured the levitation characteristics of a magnet levitating above several hybrid stators with rectangular magnet pairs of different intervals. For the measurement, a superconducting stator without magnets was compared against hybrid superconducting stators. The vertical and horizontal magnetic forces between the hybrid stator and the levitating magnet were measured by quasi-static displacement. The interval of the rectangular magnet pair has an optimum value for maximize magnetic stiffness. The horizontal restoring force of the hybrid stator acted over a wider displacement range. When used in an optimal design, the proposed hybrid stator is expected to exhibit better levitation characteristics than a simple stator.

In this research, we investigated the characteristic change of the magnetic flux pinning phenomenon caused by creating a step between three high-temperature superconductors. In order to investigate the characteristics, we created a levitation system that uses the superconducting pinning effect on the levitation body created by the magnetic flux concentration method. By analyzing the restoring force characteristics of the created levitation system, we verified how the restoration characteristics change depending on the step. As a result of the experiment, the restoring force was improved when the magnetic flux focusing part and the step of HTS were under specific conditions. From this, Experiments have revealed the usefulness of creating steps between superconductors.

One of the challenges of blood pumps that are being used for a long time is the synchronous control of flow rate with a natural heartbeat and the control of blood coagulation. To realize these control systems, it is usually necessary to use additional sensors in the blood pump system. This is, however, difficult in the case of implantable pumps due to the complexity and increasing size of the system. Hence, we have proposed a method in which a magnetic bearing is applied not only as a mechanism to support the impeller but also used as a sensor to measure biological information in real time, thereby achieving the heart rate synchronization control and the thrombosis detection and prevention in the blood pump. We conducted in vitro experiments with a mock circulatory loop to evaluate the proposed methods.

Mechanical circulatory support devices such as ventricular assist devices (VADs) are required for treatment of heart failure patients with small body size. However, clinically available rotary VADs which can be implanted in small pediatric patients still have not been developed. The implantable pediatric rotary VADs require compact device size, high mechanical durability and blood biocompatibility. Selection of impeller suspension methods is significant important for development of the rotary VADs. Magnetic suspension system is one of the strongest candidates to develop next generation VADs which can completely suspend a spinning rotor impeller without mechanical contact. Our research group has been developed an ultra-compact double stator self-bearing motor with 5-degrees of freedom (-DOF) control. The 5-DOF controlled self-bearing motor is 22 mm in diameter and 34 mm in height. This paper investigated magnetic suspension stability during pump operation. The developed maglev centrifugal blood pump produced flow rate of 0-3 L/min against head pressure of 60-100 mmHg at rotating speeds of 4000-5000 rpm. The centrifugal impeller was completely suspended with the proposed 5-DOF control concept. The results indicate sufficient pump performance for pediatric circulatory support and stable impeller suspension performance.

Vehicle localization is an important factor in autonomous driving vehicles. Particularly, accurate and precise information about the vehicle location, and robustness towards weather and road conditions is required for such uses. Vehicle localization using roadway magnets has proven useful regarding its precision and robustness. However, it is not widely used due to a concern that introduction and maintenance cost of such systems may be costly. A breakthrough in sensor technology has made it possible to pick up weak magnetic force, thus enabling the use of low-cost magnets. Combined with a new method, vehicle localization using magnetic markers is regaining attention as Magnetic Positioning System (MPS). This paper focuses on vehicle heading estimation of MPS using only one magnetic sensor array. Current system cannot measure vehicle heading with a single magnetic sensor array, so a novel approach is required. We propose a method to enable heading estimation: a sensor fusion of IMUs and marker position. This is further investigated in simulations, with some promising results.