Here, we analyze the energy loss that occurs owing to slippage between tires and the road surface in four-wheel-steering electric vehicles. We investigate the determination of tire force distribution for minimizing the energy loss as an optimization problem under the following constraints. We formulate the problem with the constraints that the total values of the traction/braking forces, of the lateral forces due to the steering of the front and rear wheels, and of the yaw moments generated by differences in the steering and the traction/braking forces between the left and right wheels are equal to the corresponding reference values. The analysis algebraically determines the tire force for the four wheels and the steering angles of the front and rear wheels. We also determine the optimum direct yaw moment analytically on the basis of the solution. We demonstrate, through numerical examples, the effect of energy loss reduction by comparing the optimization method with an alternative tire force distribution without the direct yaw moment control.

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This paper proposes a driving/braking and lateral force distribution of front steering electric vehicle using feedback control. The proposed method employs quadratic programming to distribute the driving/braking and lateral force in order to equalize the tire load factor on all wheels and consider the limits of the driving/braking force. The effectiveness of our proposed method is proven by a numerical simulation.

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This study examines the assistance system to predict driving behavior considering the pre-preceding vehicle information. The assistance system indicates the evaluation index considering not only the relation (Time HeadWay) between the preceding and following vehicles, but also the relation (Time To Collision) between the pre-preceding and following vehicle. Driving simulator experiments are examined with two participants who follow the preceding vehicle follows the visible pre-preceding vehicle. The participants with the assistance system make it possible to follow the preceding vehicle with a small relative velocity to the pre-preceding vehicle, while the participants without the assistance system with a large relative velocity to the pre-preceding vehicle.

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Pedestrian collision avoidance in urban environments is an important active safety technology to protect vulnerable road users and realize zero-traffic-accident society. Especially, reduction of vehicle-pedestrian collision accidents at intersections by using active vehicle control technology is a promising approach. This paper focuses on the driving situation which drivers need to negotiate pedestrians near crosswalk region. This paper describes an autonomous pedestrian collision avoidance system by automatic braking. The intensity of braking maneuver is determined by the application of Potential Fields theory with considering occlusions in intersection environments. Finally, the effectiveness of the autonomous collision avoidance system is verified by computer simulation which employs driving scenario from a near-miss incident database.

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In order to prevent the global warming, the emission of greenhouse gases must be reduced. In the public transportation, an electric bus is suitable for realizing this. However, electric vehicles have been limited to political uses in public corporations due to the constraint of the battery weight. Therefore, the electric bus system charged at every bus stop has been proposed. In addition, the charging of electric power generated from green energy sources has been proposed. One of the characteristics is light weight of the storage device. A simulator calculating the consumption energy between bus stops is required in order to utilize this advantage. Therefore, the author has developed the simulator using a single-seat electric vehicle. However, the effect of the number of passengers can not have been confirmed. In this study, a minivan is converted into the electric vehicle, and the effect on the passenger number is examined. Then, the simulator, which calculates the consumption energy between bus stops considering the effect of the passenger number, is developed.

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A nonlinear controller for accelerating a mobile inverted pendulum (MIP) with a center of gravity moving mechanism is proposed. The controller shapes the total energy of the system and utilizes instability of the MIP for acceleration. The body angle and the displacement are controlled to keep statically unstable but dynamically stable states. The intentional destabilization leads to indirect control of translational acceleration. The total energy of the system is shaped such that the energy becomes minimum at given desired states, and the system is controlled to converge to them. To derive the energy shaping controller, the system has to be described as a port-Hamiltonian (PH) system. In this study the MIP is shown to be appropriately described as a PH system and the controller is obtained. It can achieve various control properties through the energy shaping procedure. Especially an energy function that will lead to safe operation of the MIP is proposed. The function ensures that motion of the MIP is restricted within predefined regions, and converges to the desired states. The controller also returns the system back to the desired states with state-dependent gains that become large if the MIP comes close to fall over. Effectiveness of the proposed controller and utilization of instability for the MIP with a center of gravity moving mechanism are verified through simulations.

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Recently, many attentions have been paid on a Personal Mobility Vehicle, as it is expected to be a new transportation vehicle. However as it is not always recognized as a safe vehicle in Japan, riding a PMV on public road is not permitted. The authors propose the new transportation system using PMVs as automatic driving vehicles, adapting a path following control and a spacing control. Prototype vehicles are produced and the basic performance and the feasibility of the proposed system are examined through the experiments and the numerical simulations.

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Stability of a two-wheeled inverted pendulum vehicle was evaluated using rider-vehicle modeling, electromyography of leg's muscle of rider, and subjective evaluation. A rider and the vehicle are synthetically modeled as a series type double inverted pendulum. Utilizing auto-regressive exogenous (ARX) model methods, correlative relations were found between control gains and stability of the vehicle that achieves better ride comfort. The experimental results show that the higher the control gains, the smaller the activities of leg's muscles. However, according to subjective evaluation of ride comfort, higher gains did not always achieve better ride comfort. Moreover, the rider-vehicle model has no unstable poles, even when the vehicle model has an unstable pole. The poles of the rider-vehicle model had tendency to have bigger negative real numbers, which suggests stability of the vehicle can be evaluated by the positions of the poles of the rider-vehicle model. Through identification of the rider-vehicle model, the control gains of the rider's posture were calculated. It was found that the control gain against the rider's posture is dominant, and the higher the control gains of vehicle, the smaller the gain against the rider's posture. The results show stability of the vehicle can be evaluated by the control gains against the rider's posture.

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A mobile inverted pendulum (MIP) draws attention as a next-generation energy saving vehicle especially for urban life because it is energy-efficient to transport a person and has a small footprint. It is important for the MIP to run safely on various type of road. However, there are few studies on the MIP considering slopes or steps. We focus on a change of slope angle and aim to improve safety when the MIP runs on such a road. To achieve this goal, a simulation model of the MIP which runs on a road with a change of slope angle is constructed. This simulation model introduces constraint contact formulation to consider change of a contact point. Motion of the MIP is analyzed when it runs on the road. The results of the analyses indicate that there is a correlation between the acceleration of human body and time rate of change of slope angle. It is also shown to be difficult to balance safety with running velocity following capability with a fixed feedback gain. Based on the results, we propose to switch controllers on level ground and on a slope. Effectiveness of the proposed method is verified in simulations.

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A unique shield system has been developed utilizing electrostatic force to remove dust breaking into bearings and mechanical seals of equipments used for lunar exploration. A single-phase rectangular voltage was applied to insulated parallel plate electrodes printed on a substrate at the clearance of the mechanical sealing part. Because the performance of the former system was not satisfactory at an inclined angle of 30°, we added support electrodes outside of the main electrodes so that the system with the support electrodes generates wide electrostatic field to improve the performance. As the result more than 80% of dust was repelled from the clearance, and it was predicted by the numerical calculation using the distinct element method that the cleaning performance to charged particles would be further improved in the low-gravity and vacuum environment of the Moon. This technology is expected to increase the reliability of equipment used in long-term manned and unmanned activities on the lunar surface.

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In this study, we propose a collision avoidance control method using the model predictive control for omnidirectional mobile robots which have convex polygonal shapes. It is possible to modify the conventional oval potential field method to consider the shape of the robot, but this potential field may have local minimum points. Thus, we execute the path planning based on the conventional oval potential field method within the predictive interval to reduce local minimum points. Then, the model predictive control which has an artificial potential function term considering the shape of the robot is executed. We use this planned path as the reference; the inputs of the model predictive control reduces local minimum points which comes from the artificial potential field considering the shape of the robot. Hence, the proposed method achieves both consideration of the shape of the robot and reduction of local minimum points. Moreover, we conduct numerical simulations and experiments to verify that the proposed method can prevent local stationary points and achieves the collision avoidance, while it takes into consideration the shape of the robot.

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The total length of sewer pipelines in Japan is over 420,000 kilometers. Quantitative measurement methods for regularly scheduled inspection of those pipelines have been desired instead of experienced observation on in-pipes animation images, which are obtained from an autonomous vehicle robot equipped with a CCD camera. In this study, we developed vehicle robots equipped with integrated sensing system using two types of sensors, so that measuring unevenness of the sewer pipe precisely and quantitatively is achieved by a simple measurement way at comparatively low cost. To accomplish these missions, two vehicle robots are designed and manufactured respectively. The first vehicle is specialized in the function of driving to pull a rope, which is connected to the second vehicle. The second one is specialized in the function of measurement to be towed. Two methods to integrate the data on the evenness, which are obtained by a gyro sensor and an inclinometer, are proposed so that each sensor faults are mutually compensated. The first integration method is to estimate the attitude angle applying the Kalman filter algorithm, and the second method is to assign well-performed sensor data to static and dynamic state each other. The experimental study shows that the integrated algorithms obtain the unevenness effectively and precisely.

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It is necessary to do absorption of the impact and preliminary operation for the following jump at the same time to achieve a continuous jump. Then, the extension spring is built in. An extension spring extends because of the joint torque that occurred by a crash force at the time of the landing for knee joint to synchronize with the ankle joint and to move. As a result it made it to the structure that the knee joint and the ankle joint expand in the restoration power. The knee joint is excited in the sine wave at the resonance frequency of the installed spring in this research. An increase in the jump power by the use of the energy when landing is confirmed. We verify the utility of energy accumulative jump robot that uses the spring element.

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This paper describes the methodology of environmental risk map construction based on driving personal mobility using LIDARs. First, an omni-directional sensing platform is built up by attaching two LIDARs on the vehicle. In addition, an algorithm to distinguish pedestrians and others is implemented and the quantitative parameters of pedestrian motion are extracted from environmental data on driving in a pedestrian walking space. Furthermore, an environmental risk map during driving is constructed the risk potential field based on the potential field method. Finally, an algorithm to avoid collision risks is described and its effectiveness is verified by simulations based on the environmental risk map during driving.

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Recently, autonomous driving vehicles, such as those developed for the DARPA Urban Challenge, have been researched all over the world. In Japan, some autonomous vehicles such as those developed for Tokyo Motor Show 2011 held at last year, have also been developed. For such autonomous vehicles, perception of surroundings around the vehicle is one of the most key technical issues. In the field of perception for the autonomous vehicle, it is important to detect static obstacles and reveal drivable region. Moreover, it is also necessary to detect dynamic objects and to predict its future trajectory, since traffic environment is highly dynamic environment. In this paper, we propose a method to percept surroundings using LIDAR. In this method, obstacles and drivable area is recognized base on Occupancy Grid Maps, which is the method to estimate posterior probability of being occupy. Moreover, dynamic objects are detected based on the Occupancy Grid Maps.

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This paper presents the posture and position control technique for a quadrotor UAV(Unmanned Aerial Vehicle) during hover by using gyros, inclinometer and profile sensor. In previous paper a developed quadrotor UAV performs short-time hovering by 3-axis gyroscope. For the long-time hover the integral error is accumulated and UAV is notable to maintain the posture angle. Then, this paper introduces the posture sensing method which is combined with inclinometer and integration of gyroscope. Moreover, in order to control the hovering position. This paper is developed a high-speed light-marker sensing unit using a profile sensor S9132. Experimental results show the advantage of this unit and measurement system.

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In this research project the developed an autonomous quadrotor helicopter is used for in indoor search applications. The helicopter body weighs 0.83 kg and can carry a payload weighing 0.4 kg. It is equipped with MEMS sensors (gyro, acceleration, magnetic, and pressure), a PSD unit, an ultrasonic sensor, and an optical position sensor. The control system employed an RX CPU. To measure the attitude angle, the output signal of the gyro sensor is passed through a filter to eliminate vibration components and then integrated. Correction based on the acceleration sensor is applied to suppress the drift of integration. Position calculation is performed by the optical position sensor, which is observed infrared LEDs placed on the floor. As a result, hovering was achieved with an accuracy of ±0.3 meter.

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This paper discusses an estimation method of auto frequency response function using additional masses. The input forces in vibration testing cannot be applied to the excitation points of the structure, if it is difficult to secure space for excitation to structures with complex shapes. In order to improve the accuracy of estimated unmeasured frequency response function, maximum likelihood method for reducing random noise effect is introduced in this method. Additionally, reliability factor of the estimated unmeasured frequency response function is obtained by considering the propagation of random noise from measured frequency response functions. The feasibility of the method is verified by comparing the unmeasured frequency response function of a lower arm that is a part of car's suspension system estimated by the method and obtained by impact testing.

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In order to measure the vibration characteristic of a product, the experiment modal analysis is used well. However, in the method of moving a measuring point, sensor weight affects the frequency response function (FRF) to measure. Therefore, by the conventional method, it was not in agreement by the place which natural frequency measures, and there was a problem that it was difficult to extract mode shape correctly. In this paper, we propose the method of eliminate the influence of sensor mass from the measured FRF for the experiment modal analysis of light weight products, and extracting more exact mode shape. Improvement in a MAC value has been checked because it is adapted in the proposed method. So, the usefulness of the proposed method was shown.

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In the experimental modal analysis, the treatment device has to be fixed on the target structure in order to obtain the vibration response to the moment excitation. However, if the treatment device is used, the vibration property must be changed because of the additional mass of the device. Hence, it is difficult to obtain the accurate vibration response to the moment excitation. A detach type moment excitation device that an impulse moment can be impacted on the structure without using treatment device was proposed. The proposed device is easy to handle and realizes the accurate measurement without additional weight. But, in this way, excitation force and moment are limited to the small value. In this study, an attachment for the device that bigger moment and force can be impacted on the structure is proposed. First of all, the principle of the proposed device is shown. Then, the experimental results are shown to confirm the validity of the proposed technique.

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It is very important to grasp the dynamic characteristics of machinery. Modal analysis is widely used as a basic technology for machine design. Various methods to identify the modal parameters of structures by the vibration test have been proposed. Recently, the frequency domain subspace method has been developed. Generally, it is easier to overview the dynamic properties of structures in frequency domain than in time domain. Therefore the frequency response functions (FRFs) are employed. In this paper, the modal parameters are identified by the frequency domain subspace algorithm. Then the residual terms derived from rigid body motions are considered. Additionally, it is important to determine the actual model order which is related to the identified state space model. Thus Akaike Information Criterion (AIC) is used to estimate the model order. The proposed procedure is applied to identify modal parameters of an aluminum circlar plate with a hole.

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A method of extracting the component modes from the modal analysis result of a complex finite element model, such as that of a car body, is proposed in this paper. The relationship between the assembly modes and the component modes is studied in terms of the modal energy contribution. Compared with the conventional approach by which the dynamics of the assembled system is evaluated through the superposition of mode-reduced components, the validity and the advantages of the proposed method are demonstrated.

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A method for efficient vibration analysis of high mode density is proposed. The purpose of this study is classifying many modes into several groups for reducing the work to analyze modes. The grouping is based on the similarity of principal motion from which abstracting mode shapes. Applying the method to simple model shows effectiveness of grouping many modes.

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In this study, target level setting method for reference signal of operational TPA was considered using principal component regression method. A principal component having high contribution to the response signal was selected and target levels of the reference signals were calculated using the principal component by principal component sensitivity analysis. In addition, a consideration method for countermeasure was proposed using analysis of principal component behavior. Principal component behavior analysis shows the vibration behavior at a principal component having high contribution to the response signal. By referring to the behavior, a guideline for countermeasure to reduce response signal vibration could be obtained. To verify the effectiveness of these methods, operational TPA with the new methods were applied to a small model vehicle. In the experiment, floor vibration was set as the response signal and nine measurement points such as motor attachment point were used as the reference signals. The reduction target level of each reference signal was calculated by principal component sensitive analysis and the countermeasure guideline was obtained by the principal component behavior analysis. By referring to the analytical result, a countermeasure was performed actually. As a result, the floor vibration level was reduced almost same as the target level. Through these consideration and experiment, operational TPA could have more function in which the method could set the target of reference signals and suggest the countermeasure guideline in addition to performing contribution separation.

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This paper presents a method for comparing the input powers and contribution rates from a power source to a structure during machine operation determined by statistical energy analysis (SEA) and transfer path analysis (TPA). Identifying external forces and contribution rates from input power sources during machine operation is important for analyzing machine, equipment, and dynamic designs. SEA is used for systems with many resonant modes, and predicted results are based on space averages. In contrast, TPA is based on estimation of a frequency response function between an excitation point and a response point. In this study, a method is proposed for comparing SEA evaluated by the power injection method and TPA evaluated by the matrix inversion method. The proposed method is validated through numerical analyses, using a finite element method, of a partial car model consisting of four subsystems. As a result, the proposed method is effective and quantitatively accurate.

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To reduce the structure-borne sound is an important issue to increase the value of the product. Structure-borne sound is caused generally by natural vibration of structure. Natural vibration is generated by the superposition of reflected and transmitted wave. To quantify the degree of wave reflection and transmission, reflection and transmission coefficients are used. This paper describes a method which quantifies wave reflection and transmission coefficients of discontinuities in one-dimensional structure using the finite element model. The method is based on the transfer matrix representing the relationship between wave amplitude of both ends of target structure. By modelling a discontinuity by using finite element method, reflection and transmission coefficients at discontinuity can be obtained. In order to verify the accuracy of this method, reflection and transmission coefficients obtained by our proposed method were compared with those of the two part beam that have theoretical solution. Finally, feasibility of this method was checked by several examples.

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The series of the previous studies have concentrated on diagnosis of damage and deviation in structures using non-destructive tapping test. We have demonstrated the efficiency of tapping diagnostics using a simple structural model of the aluminum bar with a free end. This study deals with diagnosis of defect using a simple structural model of ABS resin bar with a free end. According to FEM model simulation, it becomes clear that natural vibration frequencies of the bar decrease when there is an internal crack. On the other hand, when the crack is located near the natural vibration node, there are very small or no changes at all. Whether or not the crack exists was assessed from correlation of the Wavelet coefficients for test ABS resin bars with and without crack. Rough location of the damage is determined from the relationship among natural frequencies. Using RMS analysis carried out by the maximum correlation of spectrogram of tapping sound signal, the analysis results demonstrate that the method by RMS can be an effective means to find position of defect and to judge presence of defect.

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For the forced excitation of a large structure such as airplanes using one actuator, natural vibration mode cannot be excited because the vibration does not spread in the entire structure. So vibration tests of a large structure use a lot of actuators. When we drive a lot of actuators by centralized control, we have to adjust command signal, such as excitation frequencies, the magnitude and phase of the excitation force, to every natural vibration mode. Thus, we used a method for driving at resonance point by using the self-excited vibration generated by the local feedback control that an excitation point corresponds to a vibration detection point. The excitation target is a laminar structure modeled on an airplane. The sixth mode is excited by using sixteen voice coil motors with the local feedback controller. The self-excited vibration cannot excite all natural vibration modes, because some natural vibration modes have changed to the other one which is easily excited. So we use forced entrainment to excite a desired mode of vibration.

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The dispersion curve of a curved beam has negative slope at a frequency region. A wave packet which is synthesized by more than two waves at the region of negative slope has negative group velocity. This paper addresses an issue of engineering application of the negative group velocity. Firstly, a dimensionless frequency of dispersion curve was introduced to achieve negative group velocity, in order to establish a design method of vibration reduction in mechanical structures. Then, backward movement of wave energy with negative group velocity was realized by using the design method, and was verified using transient response analysis of a FE-model of a curved beam. Validation was carried out from the standpoint of both negative group velocity of a wave packet and backward movement of vibration intensity. The results show that the wave energy in a curved beam does not propagate in the positive direction along the axial direction of a waveguide.

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This paper deals with dynamic transient responses of a viscoelastic structure in an automotive wiper blade. Restoring force of the viscoelastic structure includes buckling phenomena and nonlinear time lag between load and deformation. We found that large differences appear in the restoring force between a path under increasing load condition and a path under decreasing load condition. The restoring force is measured using Levitation Mass Method(LMM) proposed by Fujii. In this paper, we carry out numerical analysis of dynamic response for the structure under the same conditions with the experiment. The viscoelastic structure is modeled using nonlinear concentrated springs with nonlinear hysteresis. This nonlinear spring is connected to the levitated block, which is modeled by three-dimensional finite elements. The experimental data are compared with the calculated ones using our proposed FEM.

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Gear system is one of impact vibrating systems in the field of mechanical engineering. Generally, various dynamical behaviors or bifurcations are arised on the impact vibrating system. These behaviors and bifurcations produce the noise or abrasion on gear system. The two-mass impact model is proposed as the simplest model of gear system. However, there is little experimental study for it. In this paper, we make an experimental device of the two-mass impact model and study the dynamical behaviors or bifurcations arised on it. On the other hand, we calculate equations of motion of this model and compare the numerical results and our experimental results. As a result, it is found that the grazing bifurcation arised on this system when the gap between masses is varied.

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This study deals with the vibration characteristics of a SLR camera's internal mirror rebound. The mechanism of the mirror rebound phenomena is considered by using a simple rectangle metal plate models. In the experiment, the behavior of vibration during rebound of the camera mirror is observed. The mirror models are supported with rotational axis at long axis of the model. The mirrors are swung down freely from the horizontal plane and then hit with a stopper. Amount of rebound is measured by a laser displacement meter. The rebound amount depends on the stopper position. The Vibration behavior after the collision varies by stopper position. The Vibration after the collision depends on the deformation while in contact with the stopper at the time of collision.

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This research proposes reduction in the amplitude of the primary resonance combined with the parametrically horizontal oscillation in a High-Tc superconducting levitation system. High-Tc superconducting levitation systems have very low damping and stable levitation without control. However in such low-damped systems, complicated phenomena of dynamics can easily generated by nonlinearity of the magnetic force. Our previous research showed that when the frequency of vertical excitation is in the neighborhood of double the natural frequency in the horizontal direction, horizontal oscillation can occur parametrically through nonlinear coupling between vertical motion and horizontal motion. This research discusses on the parametrically horizontal resonance's effects on the primary resonance. We discussed possible nonlinear interaction called internal resonance between the vertical direction and the horizontal direction whose natural frequency is chosen as half that of the vertical direction. The primary resonance reduction based on this mechanism was successfully verified numerically. This kind of nonlinear oscillation can be useful for reducing resonance of a high-Tc superconducting levitation system.

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In high-Tc superconducting magnetic levitation systems, due to the strong pinning force, a levitated body can keep stable levitation without contact and control. So, there are many applications, but this system has a problem that nonlinear vibrations that derive from nonlinearity of electromagnetic force often occur. Further, structures of such a levitated body can show elastic deformation if the large electromagnetic force acts on it. Thus, nonlinear characteristics can easily appear in this elastic oscillation as follows. If the excitation frequency is the sum of two modes' natural frequencies, both of the two modes can resonate simultaneously, which is called combination resonance. If the excitation frequency is multiple of some modes' natural frequency, that mode can resonate, which is called parametric resonance. Those two resonances derive from the nonlinearity of electromagnetic force. This research investigates how parametric resonance and combination resonance affect each other. We dealt with a beam levitated above superconducting bulks which has a permanent magnet on its each end. The initial height of the beam is adjusted so that the two resonances can occur simultaneously. Numerical and experimental results show following. When excitation frequency is increasing, the above two resonances cannot occur simultaneously and transition between the two resonances rises. Furthermore, under some condition, combination resonance doesn't occur and only parametric resonance occurs. When excitation frequency is decreasing, there are states in which both resonances simultaneously occur, in which only parametric resonance occurs and in which only combination resonance occurs.

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Intrinsic Localized Modes (ILMs) are investigated in a mechanical system where N pendula are connected with each other by week linear springs when this system is subjected to horizontal excitation. The purpose of this study is to resolve the dynamical mechanism and the behavior of ILMs. In the theoretical analysis, the equations of motion for the system are derived and then van der Pol's method is employed to determine the expression for the frequency response curves. In the numerical calculation, the frequency response curves are shown for the cases of N=2 and 3 and compared with the results of the numerical simulation. Patterns of oscillations are classified from the results of the response curves, and it is found in which pattern ILMs appear. The influence of the spring constants of the connecting springs on the occurrence of the ILMs is examined. The change of the values of those spring constants may cause to Hopf bifurcation followed by amplitude modulated motion.

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1/2-order subharmonic oscillations are investigated in the multi-degree-of-freedom system where N nonlinear, identical oscillators with spatially periodic structures are connected by weak linear springs, when the system is subjected to sinusoidal excitation. Van der Pol's method is employed to determine the frequency response curves for the 1/2-order subharmonic oscillations when N=2 and 3. All patterns of vibrations are classified depending on the results of the response curves, and it is determined in which pattern intrinsic localized modes (ILMs) appear. The bifurcation set is also calculated to examine the influence of the connecting spring constants on the response curves and the occurrence of Hopf bifurcations, followed by amplitude modulated motions. Furthermore, The influence of the imperfection of the system on the response curves is investigated by slightly changing the value of the spring constant of the nonlinear oscillator. Numerical simulations are also conducted to confirm the validity of the frequency response curves and the occurrence of amplitude modulated motions.

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Stochastic resonance as an important physical phenomenon has experienced a strong development in many fields in these last years. This paper concentrates on an experimental study on the application of stochastic resonance in a mechanical vibration system. A cantilevered beam with one end magnetic is used, to perform as a bi-stable non-linear vibration system. Generally, nonlinear vibration can be resulted from the elastic force of the beam and the magnetic force, excited by an ambient vibration. The nonlinear vibration of the system becomes into bi-stable status through adjusting the distance of the two magnetic-irons. Moreover, an electromagnet generator was used to provide a weak periodical vibration for producing bi-stable stochastic resonance. The conditions of the occurrence of the bi-stable stochastic resonance were evaluated with the experiments. The results indicated that the mechanical vibration system is suitable to produce the bi-stable stochastic resonance under specific conditions. Furthermore, possibility of bi-stable stochastic resonance was also validated by the theoretical analysis of the model of the mechanical vibration system, and simulating processing was also demonstrated.

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A control method has been developed to always excite a multi-degree-of-freedom system efficiently at a resonance frequency. We proposed control methods to Multi-degree-of-freedom system can self-excite at all resonance frequency in ideal conditions. It's local FB control and cross FB control. The local FB control is a distributed control system that has a phase lag of 90° and a constant gain in a wide frequency range, and the cross feedback control mutually exchanges control signal between adjacent local feedback controllers. By using these control methods, all natural vibration modes can be excited, and maintained against a disturbance. However, we must consider large damping to putting this control method to practical using. In this paper, integral control is added to damping element of distributed control to form all self-excited vibration mode with low active damping gain in large damping conditions. Increasing gain of damping element at low frequency can assist formation of the self-excited vibration modes. We verified performance of this control system in large damping condition. At first, we verified all the natural vibration modes are excited by adding integral control into damping element. Additionally, we verified the natural vibration modes are excited at resonance frequency. Finally, we verified amplitude of the vibration is maintained against large damping.

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This paper proposes the measurement system of cubic nonlinear elasticity of tissues. The system consists of a vibrator, a measuring object and a control circuit. We apply a nonlinear feedback proportional to velocity and displacement squared of the vibrator to actuate the vibrator for inducing van der Pol type self-excited oscillation and control the amplitude of the oscillation by changing the nonlinear feedback gain. When the vibrator touches the measuring object, the frequency shift of the vibrator occurs depending on elasticity of the object. When the object has nonlinear elasticity, it causes a natural frequency shift related to the amplitude of the vibrator. Therefore, by the change of the response amplitude based on the variation of the nonlinear feedback gain, we estimate the nonlinear elasticity of the object. We theoretically examine the validity of the above proposed measurement method for the cubic nonlinear elasticity of the object and experimentally confirm the performance for the cubic nonlinear elasticity of the system with magnetic restoring force.

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The purpose of the present research is to develop a hand-held vibrating tool using self-synchronization phenomena in order to address the problem of the hand-arm vibration syndrome. We focus on the development of a vibration mechanism for a tamping rammer used to compact cohesive soils and asphalt. The prototype with a generation mechanism of synchronous vibration suitable for a tamping rammer has been developed based on the mechanism of the impact model with four oscillators developed in the previous report. This model consists of an upper block and two lower blocks coupled by coil-springs, and two rotor-type oscillators are mounted on each of the lower blocks. In the present study, the availability of the synchronous vibration generated in the prototype is investigated based on sand compaction tests and a numerical computation using the shooting method. The results confirm that synchronous vibration which is able to achieve a good balance between vibration control and the excitation can be generated.

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The purpose of this research is to develop a synchronous vibration mechanism in order to reduce the hand-transmitted vibration. In this paper, we target an electric hammer and devise the impact model with two oscillators (Model 2). This model is examined analytically and is confirmed that the synchronized vibration for achieving a good balance between vibration control and excitation can be occurred. Also the impact model with one oscillator (Model 1) based on a common tool mechanism is devised as a target for comparison and the two models are examined analytically. As the result, the objective synchronized vibration exists in larger area in Model 2 than in Model 1 in the case that upper block is applied by static load and that the stiffness of constant of piecewise-linear spring which imitates crushed objects changes.

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A rotary machine is a significant component of many mechanical systems and it is important to clarify the dynamic characteristics under many rotational conditions. In this paper, we theoretically and experimentally analyze the steady state responses in a horizontally supported Jeffcott rotor produced in the cases when the rotational speed is in the neighborhood of twice the natural frequencies in the horizontal and vertical directions. First, we derive the equations of motion by considering the effects of gravity and the cubic nonlinearity of restoring force by the support condition. These synergistic effects produce the difference between the linear natural frequencies in the vertical and horizontal directions and make the stiffness in the vertical direction asymmetric. Secondly, we perform nonlinear analysis by the method of multiple scales and derive two unstable regions and frequency response curve. These indicate that the nonlinear resonances can be produced in the neighborhood of twice the natural frequencies in the horizontal and vertical directions and the frequency response curve of the resonance near twice the horizontal natural frequency is hardening-type, while the frequency response curve of the resonance near twice the vertical natural frequency is softening-type.

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Recently superconducting magnetic bearings have been applied to many engineering products, such as flywheels and turbo-chargers. This is due to the fact that such bearings, unlike other bearings, can support rotating rotors without any contacts, and make it possible to rotate a rotor up to an extremely high rotational speed. When superconduction bulk material is used as a bearing, it traps a magnetic field received from a permanent magnet, and restoring force acts to return it to the initial cooling position. We considered a case in which the permanent magnet has asymmetry in the circumference direction. Their system is hardly able to be constructed completely symmetric in the circumference direction, and anisotropy can occur in the magnetic field. Equations of the motion that assumed the anisotropy of the magnetic field are derived. We then investigated the behavior of the system numerically, and confirmed that the system has the characteristic of a bearing which has anisotropic restoring force, a flat axle, and the nonlinearity of the restoring force at the same time. According to these effects, the frequency band showing instability of the rotor can be changed.

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This paper deals with the problem of vibration quenching of the system with a limited power supply using a Hula-Hoop and a motor to assist its rotation. Quenching of horizontal vibration of the one-degree-of-freedom system forced by centrifugal force of unbalance is researched. Following was made clear from the numerical analysis, the approximate analysis using the averaging method, and the experiment: (1) By cancelling the rotational resistance of the Hula-Hoop using an assistant motor, the amplitude of the main system becomes zero theoretically. (2) In the case that the power source and the torque assist equipment are both motors, the optimal voltage for the assistant motor to quench the main system vibration perfectly is obtained from the approximate analysis using the averaging method. (3) The results obtained by the averaging method and those obtained by the numerical integration were in good agreement not only qualitatively but also quantitatively, and those results and that obtained by the experiment were in good agreement qualitatively.

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We develop an algorithm to compute an approximate solution to the Hamilton-Jacobi equation for the generating function for a nonlinear optimal control problem in this paper. We prove that an approximate generating function based on Taylor series can be obtained by solving a sequence of first-order ordinary differential equations. Once we obtain a generating function for a certain boundary condition, we can solve any trajectory generation problem of the same system for different boundary conditions. Numerical examples illustrate the effectiveness of the proposed method.

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This paper is concerned with analysis and control of systems based on spatial discretization, i.e., a cellular discretization of planar special Euclidian space. We apply this idea to multi-agent systems (e.g., obstacle clustering system and sheepdog system), and the mobile robots which undergoes holonomic constrains due to multiple rigid linkages and nonholonomic constrains due to wheel rotations.

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In this paper, a new identification method for non-parametric piecewise affine (PWA) models is introduced and applied for a mechanical system with non-linear friction. The method is based on the non-parametric data-based representation of PWA maps and the data compression with l_1 optimization technique, which enable the method to deal with large data sets. This method can be applied to a wide range of modeling problems, and an actuator with harmonic drive system is analyzed in this paper.

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This paper deals with a distributed control based on gradient methods for load frequency of power networks including distributed generations, batteries, and renewable energies. In recent years, energy problems and global warming have become the hottest worldwide social problems. Therefore, a lot of distributed generations such as the photo voltaic and wind power generations, the biomass power generations, and the co-generations, are going to be installed in large scale power network systems from viewpoints of energy conservation and the cost reduction. At the same time, it is well-known that they have adverse affects on system frequency and fluctuation of voltage in power systems. Hence, it is necessary to explicitly control every generation cooperatively and optimally and ensure safety. The control objective is to minimize the cost function of load frequency control problem of power networks and to operate power systems optimally by means of distributed control based on gradient methods with Armijo and Wolfe type line search. Finally, simulation results of power networks including distributed generations show the effectiveness of the load frequency control.

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This paper deals with prediction algorithm applying for photovoltaic (PV) systems in smart grid. This prediction is aim to predict the amount of the next day of generation using the previous data and the weather forecast which get from Japan Meteorological Agency. The procedure of prediction consists of two steps, the data processing and the unknown parameters estimation. In the data processing, our proposed method considers the characteristics of PV generation using cluster ensemble. We propose the cluster ensemble based on k-means to choose the groups with a correlation with previous data. In the unknown parameters estimation, we provide the regression model for PV generation and the unknown parameters are estimated via H_∞ filtering. The effectiveness of the proposed prediction method is demonstrated through numerical simulations.

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In this paper, we present a cooperatice distributed energy management scheme over energy networks. We first list local objective functions distributed over the network and then formulate the global objective function to be minimized by collecting the local functions. Then, we present an energy management algorithm achieving the total optimization in a cooperative and distributed fashion based on receding horizon control and multi-agent optimization techniques. We finally demonstrate its effectiveness through simulation.

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