Wave energy is attracting a lot of attention as a form of renewable energy and various studies are conducted around the world for the practical application of wave power converters. Among the various methods of wave power generation devices proposed so far, a point absorber wave energy converter (WEC) is more efficient and easier to install than the others. A WEC with a tuned inerter, which consists of a tuning spring and a rotational inertial mass, was proposed by the authors to enhance the power generation performance by taking advantage of the resonance effect. However, the frequencies of ocean waves vary from hour to hour in real sea state thus a mechanism to adjust the change of wave frequencies is required to improve the power generation performance. Therefore, in this research, a WEC with a variable tuned inerter, which can change the inerter value, is proposed. Also, to detect the dominant wave frequency, the Fast Fourier Transform (FFT) technique is applied. Then numerical simulation studies are carried out on a point absorber WEC using the one-day wave height data measured off the coast of Fukushima-Ken and in Kashima port. The results show that the proposed system with the FFT can improve the power generation performance.

We develop high power magnetostrictive vibration power generator for battery-free wireless electronics. The generator can efficiently extract power from vibration when the device resonates with a frequency of a vibration source, but the power generation amount significantly decreases if it deviates from the resonance frequency. As a solution, it has studied that adjusting resonance frequency by changing electrical loads. In this paper, we investigated design of generator’s coil for wide resonance frequency adjustment by electric control. In experiment, we made prototypes with a different coil and connected a capacitor to control resonant frequency. Then we measured the change in resonant frequency of the generator by changing capacitance. In the result, we found that the coil design to strengthen the coupling between the electrical part and the mechanical part while keeping the internal resistance small was necessary to widen the resonance frequency adjustment width.

This article aims to verify the power generation efficiency of a inerter-controlled tuned inertial mass electromagnetic transducer (TIMET) experimentally. The TIMET consists of a ball screw mechanism, rotational mass, turning spring, and permanent magnet synchronous motor (PMSM) and its energy absorption capability can be increased by taking advantage of the resonance effect of the rotational mass due to the tuning spring. However, the TIMET cannot show maximum performance for vibrations that change its dominant frequency because of the mechanism. To address this issue, this paper proposes the a variable tuned inerter mechanism which can adapt to the frequency change of external disturbances for the TIMET . By calculating the dominant frequency of vibration by the fast Fourier transform using the measured data, the mechanism can be adjusted to the external frequency change automatically, leading to improved power generation performance.

The maximum power generation efficiency of the vibrational generator is obtained by matching the resonance frequency with the vibration frequency. Therefore, techniques for adjusting the resonant frequency of the generator are important. At present, adjustment is carried out by changing the mass of the tip of the generator, but this work is complicated and not practical. And, there is a problem that it is difficult to change the resonance continuously in the vibration in addition to the difficulty of the accurate adjustment. One of the solutions to this problem is to change the resonance by bending the tin plate attached to the tip of the generator. In this paper, the adjustment mechanism was changed to improve the power generation characteristics and the accuracy of fine adjustment. And, by using this adjustment mechanism, adjustment of resonance frequency under cutting vibration of actual machine tool was carried out, to evaluate power generation characteristics of the generator.

In recent years, energy harvesting from vibration is drawing attention as one of the methods to supply power to sensors. The aim of our study is to obtain design guidelines for energy harvesters with high energy conversion efficiency through vibration testing and analytical modeling. In this study, an energy harvester that generates power by the principle of electromagnetic induction caused by vibrating two permanent magnets that are linearly placed along a cylindrical housing are proposed. The prototype of the energy harvester has been designed and fabricated. By mounting the harvester on an electrodynamic shaker and applying base excitation to the harvester, vibration testing was performed. Parametric studies have been conducted by changing the conditions such as the input displacement, the polarity of the magnets and the frequency of the input base displacement. According to the results of experiment, it is shown that it increases the amount of generated power when the magnets are installed with opposite polarity with each other. In addition, in the case of attractive force, the numerical analysis model of the electromagnetic induction type energy harvester using the twodegree-of-freedom oscillator was constructed and the dynamic analysis was performed. In the numerical analysis, the damping coefficient was identified so that the natural frequency and the resonance peak coincided with each other. Good agreements between the experimental results and the numerical analysis results have been observed near the resonance, and the validity of the constructed model and the damping coefficient identification results were confirmed.

Electromagnetic shunt damping is a method of damping by connecting a shunt circuit to the terminals of the voice coil motor (VCM). When controlling the VCM current using an amplifier, the control law has a function equivalent to that of a shunt circuit. In this paper, we propose a new method that analyzes not only the performance of conventional shunt vibration control, but also the response performance of generated force and energy consumption for current controlled VCM.

Piezoelectric NC-shunt damping is a technique for vibration suppression by connecting an external circuit called the NC-shunt circuit (Negative capacitor shunt circuit) to a piezoelectric element attached to a mechanical structure. In this paper, we formulate the multimodal NC-piezoelectric shunt-damping problem by minimizing the weighted 𝐻_∞-norm, which enables to evaluate multiple resonance peaks. We have carried out simulations and experiments in order to evaluate the effectiveness of the proposed method, discussed the mismatch between simulation and experiment in terms of stability margin, and improved the parameter tuning method.

The conventional analytic way based on the linear piezoelectricity cannot reproduce the frequency response of the piezoelectric smart damping structure connected to the self-sensing synchronized switch damping on inductor (SSDI) technique. Firstly, necessity for incorporating the nonlinear piezoelectricity into the model was discussed, using the stressstrain properties, and the polarization- and strain-electric field loop of the piezoelectric materials. After the discussion, a new calculation methodology was proposed in order to predict the electromechanical properties for such a smart structure. A new governing electromechanical equation was derived based on the nonlinear piezoelectricity. The harmonic balance method (HBM) and the nonlinear optimization method was employed in order to determine the nonlinear parameters. After deriving the governing equation, the two-way coupled simulation technique, which can simulate real performance of the piezoelectric smart damping structure connected to the self-sensing SSDI circuit, was developed. The proposed calculation methodology and technique will allow us to simulate and predict the electromechanical properties for the piezoelectric smart device.

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. we aim to improve the movement efficiency on flat terrain. In this paper, we added a rotation axis that allows the body to roll to general bicycle, and designed the snake-like robot that can be transformed into a bicycle. Feedback control was performed to stabilize the snake-like robot to prevent falling dawn while it was stationary or driving. Thus, the static stability and driving stability of the snakelike robot were evaluated from the time history of the angle indicating the state of the robot.

This paper describes evaluation of vibration characteristics and running stability of a railway vehicle. In order to improve ride comfort it is necessary to decrease carbody elastic vibration. Transmission excitation force by longitudinal vibration from bogie to carbody induces carbody elastic vibration. For reducing transmission excitation force it is effective to soften longitudinal vibration isolator between carbody and bogie. However, it is commonly considered that running stability becomes worse when longitudinal vibration isolator is softened. Therefore, we should make a device which copes with both elastic vibration reduction and running stability and an advanced model of longitudinal vibration isolator between carbody and bogie. To make a car model including longitudinal vibration isolator, excitation tests of a full-scale test vehicle to verify the vibration isolation performance was carried out in the rolling stock test plant. Then, we made a simulation model of railway vehicle with multi-body dynamics software to confirm the vibration isolation performance on the tests, and to evaluate running stability by obtaining the critical hunting speed. As a result, we confirm that vibration characteristics results at 13.3 Hz on the simulation qualitatively conform to the test, and stiffness of rubber bush through traction link do not greatly contribute to the critical hunting speed.

Adhesion and wheel slip phenomena should be well clarified when improving the performance of re-adhesion control of the railway truck, therefore the detailed modeling of the truck including traction device is important. However, in many studies, only two-dimensional dynamics of truck, were taken into account. In this paper, three-dimensional model including roll motion of truck with parallel Cardan drives is presented. A detailed model of tangential force coefficient considering the influence of wheel load and velocity is also introduced into the detailed model. Simulation result shows that tangential forces of the four wheels are different each other. This is caused by the difference of wheel loads with not only longitudinal direction but also lateral direction. Furthermore, it is shown that truck flame rotates to specific direction with driving torque. Relation of vertical axle spring force and wheel load is described and compared with previously mentioned phenomena in running experiment.

Angle of attack between a rail and a wheel of a railway vehicle is an important physical quantity for evaluating the curve passing performance because the derailment occurring at curved tracks is related to it, though it is difficult to be measured continuously and easily. The authors have proposed the continuous estimation method of it using Kalman filter based on the constitutive law of the creep force. The numerical calculation results show that the proposed method can estimate continuous responses for the angle of attack qualitatively. However, in the proposed method, there still remain problems which be considered from the viewpoint of accuracy. This paper states the investigation results about the performance of proposed method from the viewpoint of the dependence on the saturation of the creep force.

It is generally known that the groove on tire tread can increase the friction force between the tire and the road surface under wet condition because of the improvement of drainage performance. Although wheel tread of actual railway rolling stocks has a machined contact surface like the groove on tire tread, the characteristics of tangential force of the wheel/rail under wet condition is not clarified in detail. In this study, the tangential force measurement using a pair of small cylindrical specimens was carried out to investigate the relationship between the machined contact surface and the friction force under wet condition. The experimental result shows the friction force under wet condition does not increase due to high iron’s stiffness if the machined contact surface provided on the tread. On the other hand, it is also confirmed that the machined contact surface has a reduction effect of the variation of the friction coefficient under wet condition. From the numerical analysis based on these experimental results, it is clarified that the longitudinal vibration of the vehicle can be decreased if the wheel has the machined contact surface in case of the braking running under semi-wet-condition.

Railway vehicles use rolling contact between wheels and rails to obtain propulsion, which results in low running resistance and excellent energy efficiency. However, since the friction coefficient between the wheel and the rail is small, and it becomes smaller in bad weather such as rainy weather, the wheel tends to slip. Also, when slipping, the propulsive force acting between the wheels and rails tends to be small, so sufficient propulsive force cannot be obtained, which causes a delay in train schedule. In order to prevent slipping, in the case of an electric vehicle, a method (re-adhesion control method) is known in which the main motor torque is controlled to control the rotational force of the wheels to prevent slipping. In this paper, we report the fact that we investigated the influence on the traction coefficient using a mini-model electric vehicle in order to utilize it for the design guideline of re-adhesion control considering the movement of the vehicle body.

It is important to understand the dynamic behavior of overhead contact lines and pantographs to achieve stable power supply. For this purpose, simulation of catenary/pantograph dynamic interaction is often performed. However, since lumped-mass model of a pantograph has been used in the conventional simulation, the three-dimensional dynamic behavior of the pantograph is not able to be calculated. The authors developed a new simulation method using a threedimensional model of overhead contact lines and a pantograph. This paper shows contact analysis between contact lines and a pantograph, and a simulation result when a pantograph passes a crossing section.

It is essential to study the reduction of damage to the railway vehicle caused by natural disasters. A 1:10 scale model vehicle is made for various tests such as an overturning test, which is almost impossible to be performed with a full-scale model. Large displacement shaking tests in the lateral direction, in which the model vehicle can derail or overturn, are carried out using the shaking table. It is found that the shape of the structure under the vehicle floor affects the amplitude value by which the vehicle may overturn. This suggests that there is some possibility which the resilience for overturning can be improved if the vehicle's parameters are set appropriately.

This paper treats analysis of rigid multibody systems subject to friction force. The authors has presented analysis methods of motion and constraint forces. In the presented motion analysis method, a nullspace matrix for the constraint Jacobian is obtained by solving a dierential equation. In the constraint force analysis method, relative displacements which violate the constraints are introduced. In this paper, motion analysis method of rigid multibody systems subject to friction force is presented. The friction force is assumed to be of Coulomb friction type. In the Coulomb friction model, kinetic friction depends on the normal reaction force and is given as a unique valued function, while static friction depends on the state of the system and is not a unique valued function. Thus in the presented method, treatment of the analysis is separated according to the relative velocity between bodies subjected to friction. A numerical example is given to show validity of the presented method.

Multibody dynamics is an effective method for dynamic analysis of mechanisms composed of multiple rigid and flexible bodies, and is used in many simulations. In recent years, it has become possible to simulate complex and multidegree-of-freedom mechanisms using multi-body dynamics. However. some mechanisms have parameters that can not be measured. In such cases, those parameters are estimated from measurable data. In previous researches proposeed the identification method for multibody system using adjoint method. The adjoint method is an approach for the computation of the gradient of a cost function to identify parameters. Incidentally, the equation of motion for multibody systems are described in differential algebraic equations (DAEs) consisting of differential equations and constraint equations. When solving the DAEs, it is common to use the second over time derivative of the constant equations. However, that method has a problem that the configuration level constraints are not properly maintained. It becomes a big problem for complex system. Therefore, this study proposed the parameter estimation method using adjoint method by solving the DAEs without using the second over time derivative of the constant equations. The equations of motion were discretized by the midpoint scheme and solved by the Newton-Raphson method. Two examples show that the correct parameters are found by the present parameter estimation method.

Non-smooth DEM (N-DEM) is a particle method used to analyze systems with various particle behaviors. It is a method that uses the contact law, and it is possible to analyze with a larger step width than the conventional DEM. However, it has been confirmed that penetrating behavior occurs in the analysis result by N-DEM when the step width is too large. N-DEM does not generate a force that reduces the penetration amount, which affects the analysis accuracy. Therefore, the purpose of this research is to reduce penetrating behavior by introducing the DEM concept, consepuently to analyze the particle behavior more accurately. Since DEM calculates the repulsive force from the overlap amount and the overlap rate, it is possible to reduce the penetration. In addition, the proposed method, which combines N-DEM and DEM, can realize more accurate behavior of particles in a shorter analysis time. In this paper, the results of the proposed method are shown for the penetration caused by the collision of two particles. DEM is only applied in the normal direction when the normal penetration is large in the collision of two particles. And the energy was evaluated for the analysis result by the proposed method.

The absolute nodal coordinate formulation (ANCF) has been applied to a problem for large rotation and deformation in multibody system. A distinctive feature of the ANCF is to employ absolute nodal coordinates and global slopes as the element nodal coordinates. Accordingly, it gives a constant and symmetric mass matrix. On the other hand, elastic forces, which are gieven by highly nonlinear terms, affects computational performance. Therefore, one of significant topics in the implementation of the ANCF is to derive mathematical descriptions of the elastic forces which can be calculated efficiently. This study focuses on the elastic forces for the ANCF shear deformable element based on a crosssectional coordinates system approach and a mixed interpolation technique for the strain components of the beam element. Then, in order to improve a mathematical treatment of the rotation for the cross section, the present method introduces an augmented formulation technique with algebraic constraints regarding the definition of the shear angles at nodes of discretized elements defined as the functions of nodal coordinate. The equations of motions of this constrained system are derived by the Lagrange's equation for constrained systems. As the result, equations of motion are given by the differential algebraic equations (DAEs) with index-1. Then, outlines of numerical procedures for simple explicit and implicit schemes are introduced. Moreover, a reduction techniques for the derived DAEs with index-1 is presented. In order to calculate the DAEs formulated by the present method, this study employed a numerical integration technique incorporating the mid-point schemes with the Newton-Raphson iterative procedures. After that, in order to evaluate the proposed method,it is applied to the large deformation problem in the plane case.

In recent years, flexible multibody dynamics has been used to solve this problem. When solving this spaghetti problem by finite element method, some elements move across the boundaries between the constrained area and non-constrained area,so it is necessary to distinguish which nodes is in the constrained area, it makes the analysis more complicated. Using the ALE (Arbitrary Lagrangian-Eulerian) finite element method, some nodes can be fixed at boundaries and other nodes can be arranged arbitrarily in each area. This will make it easier to analyze the flexible body with time-varying length which occurs the spaghetti problem. This study developed a method for analyzing flexible bodies with time-varying length by combining the ALE finite element method and the ANCF (Absolute Nodal Coordinate Formulation), which is one of the formulation of flexible multibody dynamics. In this model, the element coordinates of each nodes are used as the generalized coordinates, and by changing these coordinates with time, it is possible to express the arrangement of the nodes like ALE finite element method and the time varying length of the flexible body. In order to verify the validity of the analysis using this model, this study analyze the flexible body with time-varying length, and compares the result with previous study. As a result, it was shown that the analysis could be performed with the time step larger than in previous The increase in the vibration that occurs when material length varying with time is known as the spaghetti problem.

This research proposes a method for analyzing the motion of a multibody system with members that are subject to large plastic deformation by contact and collision. This analysis method is based on the mathematical similarity between the non-smooth behavior of contact and collision phenomena and the complementarity about the nonlinearity of plastic deformation. The material nonlinearity of plastic deformation is described as a complementarity condition regarding stress and plastic strain as a yield criterion. On the other hand, Pfeiffer et al. developed an analysis method of rigid non-smooth contact and collision phenomena to a linear complementarity problem by using the complementarity condition for state transition. In this research, the transition to the yield state is introduced into the concept of contact and collision state transition in the method of Pfeiffer et al.. Thereby, the complementarity conditions of contact problem and plastic deformation are integrated into one complementarity condition. Furthermore, the linear relationship is derived from equation of motion, and formulated as a linear complementarity problem. As a result, by solving one linear complementarity problem, it is possible to analyze considering both contact phenomenon and yield phenomenon. In order to verify proposed method, a numerical analysis using a model consisting of basic elements is performed. In proposed method, contact phenomenon and yield phenomenon comes down to contact force, so these phenomena can analyze as dynamics. Furthermore, since the same numerical analysis as the conventional rigid body contact problem is possible, efficient analysis is expected.

In helical type fusion reactor, a spiral coil is used for the internal structure, which results in very severe structural constraints and is a major obstacle to the maintenance systems. Due to structural restrictions, it is necessary to perform replacement work using an overhead crane while control vibration and interference with other parts. Furthermore, the payload has thin plate structure, then the deterioration of control performance is expected due to the influence of shape and flexibility. Therefore, the influence of the deterioration should be evaluated for efficient maintenance operation. This research deals with a feed-forward recoil control method that is constrained to the target trajectory by combining feedforward and nonlinear optimization calculation. The control method is applied to the two-dimensional payload with two-point suspension, the influence of the control when the payload is flexible body is confirmed, and the control system is examined. Since the rope length changes with time, the two-point suspended overhead crane model is represented by a linear time-varying system. The input shaping method, which is a feed-forward type compensator, is used for vibration control. Optimization calculation is performed to obtain the rope length profile that follows the target trajectory. The validity of the proposed method by numerical analysis was confirmed and the proposed method, was evaluated when applied to flexible body suspended matter.

JAXA plans to apply transformable spacecraft to a space telescope that performs astronomical observation. It is necessary for the telescope to keep pointing in the same direction (attitude) with high precision for a certain period of time for observation. Here, a transformable spacecraft refers to a spacecraft that can change its shape. Conventionally, the attitude of a spacecraft has been disturbed by solar radiation pressure. However, in the transformable spacecraft, it is expected that by changing the structure of the spacecraft, it is possible to control the influence of solar radiation pressure and to perform attitude control using it. In the transformable spacecraft, the equilibrium point can be obtained by changing the shape with respect to an arbitrary angle. At the equilibrium point, the moment of attitude change caused by solar radiation pressure is small, which is an advantage. Therefore, the equilibrium point is an important point for attitude stabilization. In this research, an initial study on highly stable attitude control around an unstable equilibrium point using solar radiation pressure by a deformable spacecraft is performed. Since it is expected that the calculation will be complicated by three dimensionalization, a study using reinforcement learning will be performed to realize attitude control that does not require a model.

In recent years, space manipulators have been used in space development for building large structures and recovering damaged satellites. 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, our group has proposed a system that can operate with fewer drivers by switching the motor driver and the piezoelectric driver for braking on each axis. Then, Complex behaviors in which flexibility and friction interact may occur. 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. An energy minimization trajectory is derived for solving the efficiency deterioration which is a problem in the proposed system.

This paper focuses on a driver-less shuttle (level 4 driving automation) with four-wheel-drive in-wheel motors. We aim to construct a control law for a braking/driving force distribution of the front and rear wheels to prevent passengers from falling over inside the shuttle. Therefore, this manuscript models the shuttle by using a half-car model which considers the braking/driving force to establish the equation of motion and a passenger by using a rigid body. The passenger system uses a zero-moment point (ZMP) to set an evaluation index for the possibility of falling over inside the shuttle.

Since the occupant is not negligibly light relative to the weight of the vehicle body, it is required to consider the occupant's dynamic characteristics at the design stage. For that purpose, a model capable of simulating the physical behavior of the occupant during traveling is required. In this study, we first conduct vibration test on humans to investigate the characteristics of body behavior. After that, principal component analysis by singular value decomposition is performed to evaluate the characteristics of body behavior and to extract the primary motion modes. Then, the vehicle occupant is approximated as a two-link model in which one point is subjected to displacement excitation, and the equations of motion are derived using multibody dynamics. As a body control model, a model using both nonlinear PD control and deep learning will be examined. Finally, the effectiveness of the proposed occupant body control model is verified by comparing the behavior predicted by the proposed model with the behavior obtained by the experiment.

Japanese traditional folding fan has the unique 3D expression that does not arise in the other work of art. The painted image on the fan deforms, when it is folded into convex-concave configuration and fixed to the bamboo bones，due to the difference between the shrinking percentage of the outer arc and the inner arc. Many of the fans made until the Edo era are thought to be painted in consideration of the deformation, but it still hasn't been recognized. In this study，we try to have the digital fan model for clarifying the deformation on the fan face due to some parameters such as length of the bones. Further, we try to obtain the original plan view from the images of the folded fan as one of the reverse problems.

Various structures and materials have been developed to improve the sound insulation, and a lot of experiments have been conducted to verify these things. For reason that this method is time-consuming, a simulation using finite element method for a one-dimensional long and narrow acoustic tube has been proposed. However, the calculation result does not agree with the theoretical value and needs to be corrected. This acoustic tube has an incidence side and a transmitted side with a test piece in between. The sound pressures in front of and behind the test piece are obtained to calculate the transmission loss as the sound insulation characteristics of the test piece. In this model, the end of the transmitted side is used to set as a reflective boundary. The reason for the difference from the theoretical value is that the sound pressures obtained by FEM include both forward and backward waves. According to the definition, the sound insulation is calculated using the forward sound pressure at both sides by setting the end of the transmitted side as a non-reflective boundary. In this paper, to generalize this method, it is theoretically examined that the FEM sound pressure can be accurately separated to the forward and backward wave pressures from Helmholtz's equation. Then, the validity is confirmed by evaluating the sound insulation characteristics of the flat plate with theoretical values. In addition, the sound insulation characteristics of the plates with single core are compared with that of equal weight flat plate, and the effect for the sound insulation characteristics by the aspect ratio is examined.

In this study, we investigated vibration isolation performance of the foldable cylindrical structure with torsional buckling pattern. The foldable structure is numerically modeled by 12 independent side walls and two top/bottom surfaces connecting by rotational hinges all together. Under static compression, air sealed in the structure is simultaneously compressed to work as air spring. It was revealed that the foldable structure with air could be a high-static-low-dynamicstiffness spring by adjusting a beam radius that was virtually modeled on the hinges to supplement bending stiffness of the fold lines of the actual foldable cylindrical structure. Next, we performed transient response analysis to obtain frequency characteristics of the vibration system consisting of the foldable structure with air. In cases that displacement amplitudes of input signals were small, the resonance frequency was close to zero and transmissibility of the system was less than 1.0 in a whole frequency range. While, for large amplitudes, the resonance frequency went high and the resonance peak was observed. This trend results from nonlinear spring stiffness of the vibration system and is consistent with a theoretical resonance frequency of a nonlinear spring system given as a solution to the Duffing equation.

In recent years, ecology, sustainable, ethical, etc. have been paid attentions. From this aspect, the existence of foldable aluminum beer cans is expected, however it has not been realized yet so far. Here, it is conceivable to use folding characteristics of origami structures such as a reversed spiral structure. A diamond-cut can with the Yoshimura pattern is similar to this structure. In the case of aluminum, making the folding lines deeper affects the durability. And so, the folding lines showing the Yoshimura pattern is very shallow and cannot be folded as it is. To fold actually, the lines of diamond cut should be thinned with nails etc. and folded. First, how much load is required to crush the current diamond cut can in the axial direction is confirmed together with the usual can by both of experiments and FEM simulations.

In the crash collision, the vehicle energy absorbers play an important role in the energy absorbed performance. Because vehicle energy absorbers are hollow columns by weight reduction, they are easily bent. To prevent bending, beads such as notch are placed properly on the column. However, such beads make the reaction force smaller and the collision energy absorption performance decreases. From the point of Origami structure, a column called Reversed Spiral Origami Structure (RSO) has been developed which solves the defects of easily bending and low energy absorption performance. However, for RSO with the same thickness of conventional energy absorbers, the manufacturing cost of hydroforming in the existing technology is too expensive to be applied in real vehicle structure. Here we investigate a new Origami structure, named Flange Polygonal Origami Structure (FPO), and apply for the crash box of truck body. And we show the superiority of this new structure and this new structure can be developed cheaply by new manufacturing technique.

With the declining birthrate and aging population of society and the diversification of work styles, robot technology to cover the physical abilities of the elderly and women is required. The author examined actuators that apply the origami structure, which has been developed as a result of origami engineering in recent years, as a highly efficient artificial muscle suitable for robots with high affinity with humans and ultra-light flexible robots. As a result of the simulation of the artificial muscle, it was found that stable actuator operation characteristics without snap through buckling can be obtained by giving moderate spring characteristics in the folded portion of origami. Next, considering the flexibility of the robot using origami artificial muscle, by nonlinear matrix method analysis based on the relationship between actuator force- hand displacement, 2-dimensional motion of a 3-DOF flexible origami robot was we simulated. As a result, it was confirmed that it is possible to perform the operation along the target trajectory while keeping the robot hand horizontal.

This paper introduces the rotation angle estimation of a single stator type axial-flux self-bearing motor supported by passive magnetic bearings. Because the damping force of passive magnetic bearings is quite small, the rotational vibration may occasionally diverge. To solve this problem, a sensorless vector control is effective. In this paper, the back electromotive force is estimated from the stator voltage and the voltage drop of the resistance of the stator coil. The experimental results show that the rotation angle can be estimated by the proposed method.

HOPG (Highly Oriented Pyrolytic Graphite) means highly oriented graphite. The diamagnetic current flowing through the hexagonal mesh plane of the carbon that constitutes this causes the diamagnetism of HOPG. We introduce that the diamagnetic force can be calculated by a model that assumes that the current flowing through the hexagonal mesh surface is a ring current. Furthermore, we show from the measurement and calculation results that the diamagnetic force changes depending on the direction of the magnetic field and the direction of the hexagonal mesh plane of carbon. We show that the combination of HOPG with another HOPG whose carbon hexagonal plane orientation is different by 90 degrees can generate a larger diamagnetic force than one HOPG.

General conveying device have many problems such as metal powder occurred by abrasion and lubrication oil. Magnetic levitation linear sider has solved the problems and has used in semiconductor factory. It consists of actuator device and levitation device, and they are functioned with separate electromagnets. E-shaped iron cores are used in magnetic levitation systems and linear motors. In this linear slider, magnetic flux that produces thrust force and levitation force are mutually shared in E-shaped iron core like a bearingless motor. Electromagnet unit is designed by FEM analysis and check thrust force, levitation force and piching torque. In addition, it is checked experimentally that two functions can be organization.

A magnetic suspension system using rotational flux-path control mechanism is developed. In the developed fluxpath control mechanism, a pair of gear-shaped flux control plates are attached to the top and bottom of a permanent magnet (magnetic source); they are surrounded by a ferromagnetic outer yoke with teeth facing the control plates. The gear-shaped control plate is rotated to change the relative angle to the teeth of the outer yoke. The attractive force acting on the ferromagnetic floator is adjusted by rotating the control plates. Stable suspension is achieved in the developed apparatus. It is experimentally shown that the suspension is maintained in the presence of a disturbance.

A new type of small bearing-less motor was developed. The feature of this bearing-less motor is that it is composed of only electromagnets without using permanent magnets. The rotor has a structure in which the generated magnetic forces of adjacent teeth are in opposite directions and the diagonal teeth are excited in the same direction so that the amount of magnetic force is balanced. Power is supplied to the rotor by a resonant contactless power supply mechanism that uses a bridge rectifier circuit, a coil, and a capacitor. The power receiving part of the contactless power transfer mechanism is installed in the center of the rotor, and the power transmitting part is installed directly under the power receiving part. As for the levitating method, the teeth of the rotor are attracted to the teeth of the stator, and the rotor is levitated while suspended. Rotation controlled by applying 3-phase AC to the stator, but not in the height direction. The rotation method uses the difference in the number of teeth between the stator and the rotor and controls the rotation by adjusting the current in the stator coil. In the previous studies, we calculated the rotating torque and the levitation force of the designed mechanism using electromagnetic field analysis software to miniaturize the non-contact power feeding mechanism. In this paper, we confirmed the maximum levitation position and the controllability in the horizontal and tilt directions using electromagnetic field analysis software and explained the prototype and the control system.

In this paper, a new active steering system for motorcycles, which may be thought of as a steer-by-wire system, is proposed together with a controller design method. One of the features of the system is to use a single motor to keep the system as safe as possible in case of system failure, while two motors are used in most steer-by-wire systems to provide reaction torque to a driver (rider). However the reduction of control freedom makes it more difficult to improve the maneuverability and safety simultaneously. With this mechanism, therefore, two kinds of operation modes; 1) normal driving, 2) emergency assist are realized. In this paper we discuss controller design only for the normal driving mode by using the idea of output zeroing or regulation together with sliding mode control.

In this paper, we discuss a circular path based on the control response of a two-wheeled vehicle. For the circular path, two methods can be applied to a two-wheeled vehicle system, namely rotational coordinate transformation and expansionary coordinate transformation. However, we discovered that, unlike the latter method results in an undershoot in the initial response. we considered the problem and confirmed it via simulation.

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 controller that can run along an arbitrary curve whose shape has not been determined in advance and can changes speed of ACV for each radius of curvature. And we verified usefulness of the proposed controller by running the simulation. Using various sensor and image processing technology we get control value which required for controller. We verified usefulness of the proposed methods by executing control experiments.

Global Magnetic Positioning System(GMPS) using magnetic impedance sensor with high sensitivity has been developed through pilot tests for automated driving bus in Japan. It has been revealed that GMPS has high accuracy and robustness even in snow, rain, or other bad conditions. The intervals of magnetic markers should be larger than 2m considering costs of their installation and maintenance. In this paper, the localization method using GMPS with Extended Kalman Filter is proposed, and its accuracy are verified by experiment. Experimental results show that the intervals of magnetic markers could be increased and the maximum values of intervals should vary depending on curvature of the reference path.

This paper describes the performance of semi-active vibration suppression by a shear-type MR grease damper with the high dynamic range. The shear-type damper using magnetorheological grease (shear-type MR grease damper) is controllable; the damping force is controlled by the electric current since the rheological properties of MR grease is substantially changed by an external magnetic field produced by the built-in electromagnet. The shear-type MR grease damper was developed to overcome the two issues in conventional pressure-type MR fluid dampers: the low dispersion stability and the low dynamic range. By applying MR grease with high dispersion stability, the damping performance could be maintained for a longer time. Furthermore, the higher dynamic range could be achieved by applying the semisolid MR grease to the shear-type damper not requiring sealing elements. In this study, in order to verify the advantage of the high dynamic range of the shear-type MR grease damper, the vibration suppression test using a small model structure is conducted. A skyhook-based control law is used as an algorithm for semi-active vibration suppression. The effect of the dynamic range on the vibration suppression performance is investigated by comparing the performance under conditions of high dynamic range and lower dynamic ranges. The experimental results demonstrate that the higher dynamic range results in higher suppression performance over a wide frequency range. Therefore, it is indicated that the shear-type MR grease damper with the high dispersion stability and the high dynamic range can exhibit high performance in semi-active vibration suppression of single-degree-of-freedom systems.

One of the practical vibration control devices is dynamic vibration absorber (DVA). In principles it consists of an absorption mass and a spring. It can eliminate vibration at a specified frequency that equals the resonant frequency of DVA. To eliminate low frequency vibration, it is necessary to increase the absorption mass or lower the spring constant. The former method increases the size of the device and the latter method may cause difficulty in supporting the absorption mass. Therefore, a new device is required to suppress low frequency vibration effectively. This work proposes to insert a negative spring between the vibration absorption masses in a parallel dual-mass DVA. It is shown that the anti-resonance frequency can be set lower than that of the original DVA with an interaction through negative stiffness.

Railway vehicles are equipped with rotating machinery such as engine, motor and compressor. Vibrations generated by the rotating machinery affect the riding quality of the customer when the vibrations are transmitted to the floor of the carbody. In order to isolate the vibrations, the rotating machinery is generally supported by rubber isolator whose spring coefficient is adjusted for each device. However, depending on the mounting structure, it is difficult to obtain a sufficient vibration isolation effect in some cases. This paper introduces a reduction method of the vibrations by setting an active mass damper (AMD) near the rotating machine for such cases. First, stationary excitation tests using a test vehicle and a vertical exciter are performed. In the test, the controller design method to obtain the effective vibration reduction was established, and the effectiveness of the proposed method was confirmed using a test vehicle. Secondly, a test using commercial vehicle equipped with the actual rotating machinery was performed. In the test, the rotating machine was driven while the vehicle was stopped, and the AMD was controlled as designed. The test results show that the vibration from rotating machinery can be reduced by controlling AMD.

This paper offers an active vibration suppression technique for automobile drive systems with backlash and limitation on the control cycle. The gear backlash in automotive drive systems causes undesired oscillations, which degrade the riding comfort, when a driving torque changes stepwise. In addition, an engine used as an actuator for the vibration control involves a limitation that makes the control cycle longer and time-varying due to the slow mechanical process to update the control input (i.e., engine torque). Consequently, an active vibration control system with compensation for the control cycle limitation is investigated in this paper. First, a drivetrain model, which is simplified to make it easy to evaluate only the effect due to backlash and the improvement by vibration control, is presented. The control cycle limitation whose only the negative effects are equivalent to those of a real engine is reproduced by applying program processing to command signals from a controller. To cope with the long cycle, the sampled-data controller, which can be designed without discretization, is used. In this paper, the sampled-data 𝐻𝐻_∞ controller is designed in consideration of the robustness. The time-varying effect induces the phase delay of the control input. Hence, predictive processing using the sampled-data controller and the unscented Kalman filter is introduced to compensate for the phase delay. Considering calculation loads, it is modified so that the number of iteration times of predictive simulation is reduced. Finally, simulation studies using the simplified drivetrain model verify the effectiveness of the proposed approach.

A belt drive system by a toothed belt, transmits energy between gears, and controls the rotary angle of the load by the torque from a drive motor. The purpose of this research is to develop an appropriate control method about factors of deteriorating the control performance in the tracking control of the belt drive system. Backlash is an element caused by the gap of the meshing of the gear, and a delay occurs in the load side. Therefore, the backlash is considered as the deteriorating factor. Another one is the uncertainty that exists in the dynamics of the system. By such deteriorating factors, the positioning accuracy is deteriorated, and it may cause the limit cycle, the steady-state error, the response delay and instability. In this paper, a design method of the tracking control system is proposed for the belt drive system in which backlash and characteristic uncertainties exist simultaneously. The influence of the backlash is suppressed, which is the nonlinear element regarded as a disturbance of the linear system. A control system that guarantees robust stability with respect to uncertainty is designed based on the robust control theory. Experiments show that the effectiveness of the proposed method comparing with other conventional control system design methods.

Motion control technology is developing rapidly due to the improvement of computer performance in recent years. In the motor drive systems such as industrial robots, high-speed and high-precision motion control is required. Many methods have been studied to improve the response by suppressing the vibration due to torsional resonance. Above all, the method based on the feedforward control using the inverse model is effective in order to get the ideal response under the case of less modeling error or disturbance. On the other hand, in many systems such as industrial drives, there is a backlash due to the gears and the joint mechanism between the motor and the load. When the motor torque changes quickly from positive to negative over zero, the gears run idle in the backlash section and the torque shock caused by a collision accelerates resonance and excites vibration. In the systems such as manipulators that frequently switch between positive and negative torque, vibration due to backlash is a particular problem. In this paper, we propose a method to suppress the resonance of a two-inertia system with backlash by feedforward control that considers the nonlinearity due to backlash. The transfer characteristic including the nonlinear characteristic of backlash is converted as the equivalent model of the dead zone characteristic. Then, by using the inverse model of the calculated transfer characteristics, the feedforward control that suppresses the resonance of the spring reaction force including the influence of backlash is constructed. Finally, the effect of the proposed method is verified by simulation in a system which the control of the spring reaction force can be evaluated equivalently by controlling the load displacement.

Since many robot arms have multiple joints, multiple vibration modes occur. However, most of the previous studies treat merely a fundamental mode vibration, and higher modes are ignored. We proposed rotational vibration manipulation function to suppress the residual rotational oscillation of robot arm with an elastic reduction gear of harmonic drive. In this study, we performed simulations to discuss reference input for rest-to-rest angular motion that suppresses fundamental and secondary mode residual vibrations of a horizontal 2DOF robot arm. In vibration manipulation functions consisting of half-integer trigonometric functions, we show that such external force can be designed by appropriately selecting the operational period.

The usage of unmanned aerial vehicles (UAVs) varies from construction inspection to disaster response. Cable attachment benefits the UAV with longer operation time and larger data transmission, while the tension, inertia, and contact forces of the cable work to disturb its operation. This paper introduces a numerical modelling method of a cable with frictional contact forces using an absolute nodal coordinate formulation (ANCF), and extracts and evaluates the influences of the cable on the mechanical system’s motion. The contacting cable length, that affects frictional contact forces, is derived using the catenary curve. The numerical analysis results present errors and vibrations at the connection point of the cable and the rigid body. These are the influences when the cable contacts the ground. In this paper, the compensation system, and its validity for mitigating these influences, using an unscented Kalman filter (UKF) to estimate the state of the cable, are presented. Although there was a small error in the mechanical system’s final position in relation to the target position, the numerical analysis indicated that the proposed control system stabilizes the mechanical system’s motion.