Failure mechanism of composite laminates with impact damage subjected to compression was studied using finite element analysis. The impact damage was modeled as a double-spiral-damage which consisted of fan-shaped delaminations and matrix cracks. Cohesive element was used to simulate the damage growth. First, the damage growth before the unstable propagation of the damage was discussed from the results of static implicit analysis. Next, the failure process of laminate was analyzed by a dynamic explicit analysis. The damage grew in the transverse direction to the compressive load due to the through-thickness local buckling of the damaged area. Unstable propagation of the damage accompanying large load drop occurred suddenly after the small stable growth of the damage. The transverse damage sizes of all delaminations tended to become in equal size.
This paper presents the theoretical solution of a two-dimensional isotropic elastic medium (matrix) with eccentric two circular inclusions (ring model) under the in-plane problems. Inner inclusion is perfectly bonded to the outer inclusion. These inclusions have different elastic moduli, radii and central points. The matrix is infinite extent and subjected to arbitrary in-plane loading, for example, uniform stresses at infinity, as well as a concentrated force at an arbitrary point. These inclusion problems have many applications in discriplines such as engneering. The purpose of the present study is to apply the reflection principle and produces a general solution. Using these solutions, several numerical examples are presented graphically.
Pole side impact is one of the most common types of vehicle collisions. The pole side impact at high vehicle speed induces not only local collapse but also bending of the vehicle body. However, the estimation method of the vehicle speed with consideration of the bending has not been established yet. In the present study, the deformation of the vehicle body at the pole side impact experiment with impact speed of 80 km/h was investigated. The results revealed that the collapse deformation first occurred and then the bending deformation followed. In order to understand the deformation of the vehicle at high-speed pole side impact, lateral local compression test and three-point bending test of rectangular steel tubes were performed. It was found that the deformation of the tube was similar to that of the vehicle at the pole side impact experiment, when the specimen was subjected to the sequential test of lateral local compression and three-point bending. The change in the energy absorbed by the deformation of tube in the sequential test was also found to be similar to that in the vehicle experiment. These similarities are useful to investigate the vehicle collision speed at high-speed pole side impact based on the deformation and the absorbed energy of rectangular metal tubes.
In Japan, new developments of liquid rocket engines are now underway for Japan's next flagship launch system. In the development, front-loading design process is applied to reduce development costs and to increase reliability. Therefore it is indispensable to precisely evaluate life time of a combustion chamber, which is exposed to the most severe heat and loads among engine components, in an early design phase. In order to improve accuracy in the life prediction, we focus on the interaction between thermo-fluid behaviors and structural responses, and have been developing the multi-physics coupled simulation. By applying this simulation and the linear damage rule, we have clarified the mechanisms and the dominant factors of cracks occurred in the throat, which were experienced under development of the upper stage engine. It has been revealed that the damage is caused by creep and low cycle fatigue and depends on structural temperature histories. Structural temperature overshoots in the start-up process are affected by the transient flows of both combustion gas and coolant. Due to overshooting temperature, creep and low cycle fatigue damage are accumulated.
Impact forces applying to a thin acrylic foam film on the end of a bar were measured to clarify relation between thickness of the film and effect of impact reduction: decreasing impact force and impact energy absorption by using a manufactured falling ball testing machine. The specimens were the acrylic foam films having thicknesses of 700 to 200 µm and density of 0.50 to 0.30 mg/mm3 on a polyethylene terephthalate substrate film with a thickness of 38 µm. A stainless steel sphere with a diameter of 19 mm was dropped onto the specimen on the flat end of a steel bar. The impact loads were measured from the strain histories of the steel bar. The maximum impact force for the foam film of mere 200 µm thick was 50% smaller than the one for no foam film. As the results, logarithmic values of the maximum impact loads were found to be reduced relative to the film thicknesses and the durations of the loads were also found to be proportional to the thicknesses. The absorbed impact energy of the foam films was calculated by the impulses of the impact loads. The acrylic foam film absorbed approximately whole potential energy of the ball. Therefore, the thin acrylic foam films were found to be effective in the reduction of impact load and absorption of impact energy.
An inverse analysis method was proposed for estimating nonlinear stress-strain curve with plastic deformation from load-deflection curve of three-point bending test of simply supported beam with rectangular cross section. This method was based on a small deformation theory under a few assumptions. Curvature was derived from the relation of load-deflection by applying the moment area method and geometrical relation, and bending strain was derived from the relation of strain-curvature. Then bending stress was derived from the relation of moment-curvature. Finite element analysis was conducted for verifying that these equations could estimate stress-strain curve. The estimated stress-strain curve showed good agreement with the actual one, verifying the usefulness of the proposed method for estimating stress-strain relation from the load-deflection curve of three-point bending test.
To investigate the effect of peening treatment on fatigue properties, laser peening (LP) treatment and shot peening (SP) treatment were applied to an A7075-T651 aluminum alloy, and high-cycle plane-bending fatigue tests were conducted with a stress ratio of R = 0. Typical peening effects, including the surface roughness value, residual stress distribution, hardness distribution, and half-value breadth distribution, were measured. As a result, it was found that the LP treatment significantly improved fatigue life but that the SP treatment only slightly improved fatigue life. Because the negative peening effects due to a combination of the notch effect from the larger surface roughness and the embrittlement of the microstructure from strain hardening are greater than the positive peening effect of the compressive residual stress, the SP treatment decreased crack initiation life and fatigue crack propagation life. However, the LP-treated specimen had larger residual stress and deeper zero residual stress crossing the distance from the surface, both of which can improve fatigue life.
This study aims to develop the electro-fusion joining method for continuous fiber reinforced thermoplastic (cFRTP) composites using various carbon fibers as a resistance heating element. The material used for the experiment was woven CF/PPS laminates. The effects of processing conditions such as applied voltage, time and current and also material conditions such as thickness of the inserted PPS films on the fusion behavior of cFRTP composites were investigated. The optimum condition for electro-fusion joining were obtained from experimental results such as surface condition of joint section peeled off after applying current and welding area obtained from those images. The electro-fusion mechanism was revealed by investigating the electro-fusion condition such as applied voltage, conducting time and thickness of PPS films. The welding area was increased with increasing the applied voltage and the conducting time. It was revealed that there was optimum applied voltage and conducting time in order to prevent the thermal deformation and thermal degradation of CF/PPS laminates. It was also revealed that the uniform welding area was obtained by inserting the PPS film with the optimum thickness. When the fusion joining was carried out at the current control, the conducting behavior became stable compared to the voltage control. The results of single lap tensile strength tests revealed that the LSS value was more than 28MPa. When the spread carbon fiber 0° was used as heating element, the joining layer was reinforced with carbon fiber to the load direction.
In this paper, dominant factors influencing the weld angular distortion were discussed on the theoretical basis of the relation between weld angular distortion and distribution of inherent strain for the more accurate quantifying and managing the weld angular distortion. Based on the experimentally observed relation between highest temperature and inherent strain distributions, the mechanical melting zone was focused as the temperature distribution corresponding the generation area of inherent strain controlling the weld angular distortion. TIG bead-on-plate welding of high tensile strength structural steel was performed under the various welding conditions to investigate the effect of welding conditions on the weld angular distortion. And then the weld angular distortion was arranged by the conventional parameters of weld penetration and weld heat input, and the newly proposed parameter of the mechanical melting zone. As the results, it was confirmed that the weld angular distortion could be arranged more coordinately by the proposed parameter of mechanical melting zone rather than the conventional parameters of weld penetration and weld heat input. Thus, it was concluded that the mechanical melting zone should be focused as temperature distribution controlling the weld angular distortion for the more accurate quantifying and managing the weld angular distortion.
Pressure sensitive paint (PSP) using poly(TMSP) as a polymer binder has high pressure sensitivity for low gauge pressure conditions observed in low-speed flows, which is important for research and development in mechanical engineering fields. Although the response time of poly(TMSP)-based PSP is of the order of milliseconds, which is slower than fast-response porous-type PSP, it may be useful for the measurement of nonstationary pressure distribution with low pressure amplitude as high as 100 Pa, if the frequency is not higher than the order of 100 Hz. In this study, we have investigated the nonstationary response of poly(TMSP)-based PSP, to evaluate the feasibility of the polymer-based PSP as a measurement tool for nonstationary low-speed flows. We have applied the poly(TMSP)-based PSP to measurement of nonstationary pressure distribution around a circular cylinder in low-speed flow, and compared the amplitude spectra of PSP and that of pressure probe, both of which are obtained by FFT analysis. As a result, it is clarified that the poly(TMSP)-based PSP can detect nonstationary pressure of 90 Hz with the amplitude of 70 Pa. For higher frequency the sensitivity of the poly(TMSP)-based PSP decreases, but the nonstationary pressure of 850 Hz with the amplitude of 310 Pa can be detected. Furthermore we have visualized the distribution of the integrated intensity of the PSP amplitude spectrum around the peak, to visualize the area with large pressure fluctuation on the cylinder.
Lift and drag variations by plasma actuators have been investigated under flow at low Reynolds numbers ranging from 1.7×104 to 6.6×104. Wall-normal-jet type and counter-jet type plasma actuators are attached on the pressure surface near the trailing edge of NACA0015 airfoil, and jets are induced from x/c = 0.9 toward wall normal and opposite directions against the main flow. Appreciable variations of lift and drag coefficients are not observed in the case of flow control by the wall-normal-jet type plasma actuator. On the other hand, it is confirmed that the counter-jet type plasma actuator is effective for improving aerodynamic characteristics. As the most effective case at Re = 3.3 ×104, lift coefficient is enlarged up to 30% under lower angles of attack α ≤ 8°, and velocity distributions analyzed by PIV shows that flow near the trailing edge accelerates to y-axis negative direction. Effects of lift enhancement by counter-jet type plasma actuator tend to fall off with increasing Re. Lift and drag coefficients of NACA0015 with conventional Gurney flap (h/c = 0.03) are also compared with that by the counter-jet type plasma actuator. It is found that the lift enhancement by Gurney flap is effective over a wide range of angle of α, but counter-jet type plasma actuator suppresses enlargements of drag coefficient in high α.
Catalyst degradation on both the anode and cathode sides is one of the most critical problems caused by lack of hydrogen in each channel in the active area of a polymer electrolyte fuel cell. Especially when a fuel cell stack is in a start-up sequence for an automotive fuel-cell system consisting of hundreds of fuel cells, the initial air filling all the anode flow fields should be exchanged with hydrogen as soon as possible to avoid forming a hydrogen-air front on the cell surface, as this front can create a “local cell” within a single cell causing carbon corrosion and platinum dissolution on the catalyst layer in a membrane electrode assembly. This local cell should thus be prevented from forming in any cells of a fuel cell stack. Just as importantly, to avoid the hydrogen-air front in any cell, hydrogen should be distributed between the cells equally even if this gas distribution process is for a transient manifold. Gas distribution in a gas and coolant manifold has been well reported, but usually for the steady state. In this study, to comprehend the flow condition in the anode flow field, especially in a distribution manifold, we performed transient three dimensional numerical analysis on the anode flow field of a fuel cell stack. Without any simplification such as using an equivalent pressure drop model like porous material, the full geometry was directly calculated for flow simulation in the all channels of 200 cells of a fuel cell stack. It was clarified that (1)the flow pattern in the manifold causes a maldistribution between the cells in a transient state, (2)this maldistribution grows arrogant with the increase of initial Rein,0 number and (3)the initial maldistribution in the transient process persists during the start-up process and is never fully obliterated.
LDV (Laser Doppler Velocimetry) measurement has been made in the high Reynolds number (1010≦Reτ≦20700) turbulent pipe flow to clarify its mean flow quantity. The accuracy of the mean velocity in LDV measurement was checked by a comparison between the integration of the mean velocity profile and the actual flow rate measured by a weighting system in AIST (Advanced Industrial Science and Technology), NMIJ (National Metrology Institute of Japan). Near wall measurement is achieved by evaluating accurately the effect of refraction at the pipe wall and the actual center of measurement volume. Mean velocity profiles are compared with functional forms in the overlap region proposed by previous studies (such as, Barrenblatt, Afzal, Wosnik, et al. and McKeon, et al.). As a result, the regions which satisfy power law or log law are consistent with the one suggested by Zagarola&Smits and McKeon, et al. However, the constants are γ = 0.143, C = 8.61, κ = 0.389 and B = 4.83, respectively, and are different from values proposed by McKeon et al. Especially in log law, the present data satisfies Wosnik's formula including the mesolayer. We assume that the differences of log low and power law coefficients from the previous result may be affected by some factors, such as differences of friction coefficient, velocimetry method, working fluid and pressure operation.
Intense tonal sound radiates from flows around a trailing edge with an upstream kink shape such as found in an automotive body. To clarify the acoustic radiation mechanism and the effects of the kink shape angle on tonal sound, direct numerical simulations (DNS) of flows and sound fields and wind tunnel experiments were performed. As a result, the feedback loop of the sound generation was clarified as below. A vortex is shed between the kink shape and the trailing edge, and convects downstream. The acoustic wave radiates from distortion of the vortex due to the interference with the wall around the trailing edge. The acoustic waves are propagated and lead to the vibrating of shear layers around the kink shape. The disturbances due to this vibrating are amplified in the downstream of the reception point of sound, and a vortex is again shed. The reception point is located slightly downstream of the flow separation point. The positions of the acoustic source and the acoustic reception in this feedback loop were also clarified. Meanwhile, the tonal sound dose not radiate for smaller kink shape angle, where the vortex formation does not occur around the kink shape by the lack of flow separation. Also, for the larger kink shape angle, the large separation prompts turbulent transition and the tonal sound does not radiate.
A large amount of energy is consumed by people around the world. Most of the consumed energy is originated from fossil resources of which deposits are limited. Therefore, it is necessary for a sustainable society to use energy without waste. Fuel Cell (FC), which supplies energy effectively by Co-generation, attracts attention as a high-efficient distributed energy device for residential use. However, FCs are generally operated with City gas derived from fossil resources. Then, a FC system using hydrogen (H2) fuel produced by Photovoltaic power generation (PV) is proposed. The FC is driven with H2 generated from “surplus power”, which comes from the gap between PV output and electricity demand in residence. This PV-FC combined system approaches energy independence in the residence because consumed electric and thermal power generated by PV and FC originates from solar energy. In this study, PV and Solid Oxide Fuel Cell (SOFC) combined system (PV-SOFC system) is discussed. A SOFC, which has the highest electrical efficiency among FCs, can accept mixed fuel of H2 and City-gas. Additionally, heat-to-power ratio of SOFC output may be able to be controlled by changing H2 concentration of the mixed gas fuel. Thus, it is possible to realize the energy supply synchronizing the each variation of electricity and heat demand in residence. In this paper, the energy reduction by introducing a heat-to-power ratio controllable PV-SOFC system to a residence is simulated. The results show that primary energy consumption in the PV-SOFC system is reduced by 53.8 % for a year.
In this study, we propose a Photovoltaic power generation (PV) and Fuel Cell (FC) hybrid system for residential use to reduce consumption of energy originated from fossil resources. In the hybrid system, FC supplies electricity and heat into residence with hydrogen fuel, which is produced by power of PV installed at house. So, consumed energy is generated by PV and FC which are operated with renewable energy. Therefore, energy independence in residence is approached with applying the proposed system. In the first report of this study, primary energy consumption in PV and Solid Oxide Fuel Cell (SOFC) combined system were calculated by simulation with optimizing method. The results of the first paper showed that the energy reduction of PV-SOFC combined system was larger than the sum of those in PV only and SOFC only system. In this second paper, energy saving performance and cost of PV -SOFC are compared with other energy systems —PV -Battery system in which PV power is stored as electrical energy, and PV-EHP system in which power of PV is converted into hot-water as thermal energy, to evaluate the effectiveness to store PV power as hydrogen energy in PV-SOFC system.
This paper proposes an analytical method to evaluate vehicle maneuverability based on the comparison of null-controllability regions that are defined as the set of all initial states which can be transferred to the origin of the state space by means of admissible controls. Assuming that the multidimensional null-controllability region can be analyzed by a number of two dimensional cross sections, an optimization-based algorithm combined with a trajectory reversing approach and a ray gridding method to compute the projection of multi-dimensional controllability region onto a two-dimensional cross section is proposed. In this algorithm, the problem to determine the boundary of the controllability region is formulated as an optimal control problem to find the control inputs that maximize the norm of the terminal state of a time-reversal system starting from the origin. The null-controllability region and a reachability region of two simple examples are computed and compared with the results of previous research to demonstrate the validity of the proposed algorithm. Then the effect of tire nonlinear property on vehicle maneuverability is evaluated by comparing the size and shape of the null-controllability regions for two vehicle configurations. The results clarify the effect of tire property on the null-controllability region.
This paper proposes a design method of the fault-tolerant attitude control system for spacecraft. In recent years, there has been requirement for accurate and agile attitude control of spacecraft. To meet this demand there has been an increasing use of Control Moment Gyros (CMGs), which can generate much higher torque than reaction wheels that are used as conventional spacecraft actuators. Furthermore, it is important for attitude control systems to be fault-tolerant. In a conventional 4 CMGs system, the CMGs are placed in a pyramid mounting arrangement with a skew angle set to 54.74 degree. The maximum angular momentum of the CMG system is changed according to the skew angle. A suitable skew angle should be designed to consider normal and failure situations. Moreover, the suitable parameters of spacecraft attitude and CMG control systems are changed according to the skew angle. In the proposed method, the skew angle and the parameters of the control system are tuned simultaneously using a genetic algorithm. To verify the fault-tolerance of the proposed method, numerical simulations for the case when one CMG has failed are carried out.
Anomaly detection methods are becoming important for condition-based maintenance. This paper proposes an automatic creation method of extraction condition of sensor data for an anomaly detection system. To achieve high performance for anomaly detection, it is important to extract a machine steady state in the learning phase and the anomaly detection phase. This creation method can generate extraction condition candidates automatically using the observed frequency and expected frequency of machine sensor data. Experimental results demonstrate that the proposed method can create extraction condition candidates more accurately than the conventional method does.
Recently, a blade with friction damper has been used in a steam turbine and a gas turbine to improve the blade reliability. Especially, for the gas turbine blade in the upstream stage, a platform type damper has been widely used, where the damper pieces with variable geometries are inserted into the platforms between the adjacent blades. The damper piece is designed so that its surface gets contact with the platform surface uniformly. The contact condition of the damper piece (in other words, the equivalent stiffness and the damping caused by the damper piece), however, may change remarkably blade by blade, because of the manufacturing tolerance, the blade deformation in operation, the wear of the damper piece, and so on. Therefore, it is indispensable to consider the mistuning effect caused by the deviation of the contact condition of the damper piece, in evaluating the response of the bladed disk with the platform type damper. In this study, the mistuned bladed disk with the platform type damper is represented by the equivalent spring-mass model, and the frequency response analysis is carried out, using the direct method and the Monte Carlo simulation. The effect of the deviation of the contact condition caused by the damper piece on the response of the bladed disk is examined by the numerical simulation.
The authors propose an absorber that generates electrical power in order to not only suppress vibration but also get electrical energy when many traffic signal poles are oscillated by wind, traffic turbulence. The absorber consists of a displacement magnifying mechanism by using levers, solenoid coils and rare-earth magnets. It is useful for small deformation between a beam and a column of the traffic pole. Vibration modes of the pole are analyzed by using FEM, and then a small scale model of the traffic pole is built up. The small scale model has 2.7 m high, consists of a steel column and a cantilever beam due to rescale about 1/3 times of a real scale model, and the natural frequency of first mode is arranged to 3.5 Hz. Trial absorber is manufactured and a damping force, which is caused by the coils crossing magnetic field, is adjusted. Dynamic characteristics of the trial absorber are measured by a shaking actuator. In order to confirm vibration reduction and energy conversion, harmonic vibration test of small scale model when the trial absorber is installed is carried out by using a shaking table. The experimental results of the harmonic responses are compared with the calculated results which are derived by FEM. Effect of vibration suppression and efficiency of generating electrical power are evaluated experimentally and numerically.
This paper deals with flutter experiments and analysis of a rectangular cylindrical shell based on the non-planar unsteady lifting surface theory. In this study, experiments are conducted with a cantilevered rectangular cylindrical shell subjected to inner fluid flow, and flutter characteristics are examined. The unsteady fluid force acting on the shell surface is calculated by using Doublet-point method, which is based on the unsteady lifting surface theory. The equation of motion of the shell coupled with the fluid flow is derived by employing the finite element method. The stability of the system is clarified by using the root locus based on the complex eigenvalue obtained from the flutter determinant. Flutter characteristics are clarified by comparing the analysis results with experimental results. Moreover, the local work by the fluid force on the shell surface, and instability mechanism are clarified.
We describe a measurement method of respiration and heartbeat using a Smart Rubber sensor, a rubber-based flexible tactile sensor sheet that we developed. This method is useful for unconstrained recording of a person sleeping soundly, sleeping lightly, lying down, sitting on a bed, and so on. Our goal is to monitor those who require nursing care. The proposed method measures respiration and heartbeat as follows. First, we measure body pressure by using the Smart Rubber sensor placed on a bed. Then, the method applies a frequency analysis to the time series data of body pressure. Finally, respiration and heartbeat are obtained by extracting suitable frequency bands. In the experiments, we show that respiration and heartbeat are successfully measured. Moreover, we report that the stability of the measurement method of respiration and heartbeat.
In fabrication process for electric devices, high precision patterning on sheet substrates is required. To pattern with high precision, high precision positioning of the sheet to the target location is needed. On the other hand, a sheet is deformed locally and ununiformly by stress, temperature, humidity and so on. These sheet deformations may cause reduction of sheet positioning accuracy. Therefore, in sheet handling process, it's important to reduce and/or control these deformations. However, the state and the mechanism of these deformations are not clear. So, it's needed to measure and understand sheet deformation. In this research, we have developed a new apparatus which can measure the sheet deformation with high accuracy. The developed apparatus consists of four CCD cameras and laser height sensors fixed on a stiff frame. The measured sheet is previously patterned with the alignment marks at predefined pitch. This apparatus simultaneously detects some positions of the marks on the sheet by cameras and calculates sheet strain by the relative displacements among the marks. Furthermore, this apparatus can move above the sheet surface to measure at any place. We confirmed that this apparatus can measure sheet deformation at any place to an accuracy of a few micrometers. Furthermore, this apparatus can measure sheet deformation for perpendicular direction to the sheet surface with micrometer precision. We report the results of consideration for measuring method of sheet strain and the developed apparatus.
Ground gears sometimes brings ‘ghost noise’ whose frequency is non-integer order of mesh frequency and the cause of ghost noise is surface undulation due to manufacturing process. But the undulation is slight and it becomes difficult to detect with tooth surface measurement. To point out source gear of ghost noise, we propose ‘amplitude fluctuation analysis’ that assumes ghost noise has the cycle of least common multiple meshing period because just the same tooth pair mesh again. The proposed method can make clear which gear pair is the source of ghost noise. Combining this method and synchronous averaging method, we can point out the source gear completely. Experimental verification results with double stage helical gear system shows that proposed method is effective.
In this paper, we propose the novel directional Wavelet Transform based on the Complex Discrete Wavelet Transform(CDWT). The CDWT is one of the Wavelet Transform and widely used as space-frequency analysis method for the signal and the image. The CDWT decomposes the image into directional components from the frequency analysis. And then, we can get the border, discontinuities and edges in the image. This property is called Directional Selection and this property is expected to give us shape information and geometric features. But, previous Directional Selection only offers the six directional components and features. Thus we firstly design the directional filter that can extract many directional feature rather than previous one. Secondly we propose the novel directional Wavelet Transform combining with previous CDWT and designed directional filters. Finally, we apply the proposed method into medical image processing.
This paper discusses the parametric resonance of the metallic bellows which is connected to the fluid filled pipe subjected to the seismic excitation. The axial stiffness of the metallic bellows varies due to the internal fluid pressure variation, and this stiffness variation by the pressure variation excites the parametric resonance in the metallic bellows. Finite element model of the metallic bellows that is connected to the fluid filled pipe was developed to investigate that parametric resonance is excited in the metallic bellows or not when the piping system is subjected to the seismic excitation. Numerical simulations were carried out assuming that the metallic bellows was connected to the L-shaped pipe to examine the parametric resonance was induced due to the seismic excitation. The L-shaped piping system with a metallic bellows was excited by the shaking table to verify the numerical simulation results. As the results, it is clarified from both numerical simulations results and experiment result that the parametric resonance was excited in the metallic bellows when the natural frequency of the pipe is close to the twice of the bending natural frequency of the bellows and the piping system is resonant with the predominant frequency component of the earthquake though earthquake motion is unsteady.
Absolute Nodal Coordinate Formulation (ANCF) is a kind of finite element method for the flexible multibody system with large deformation and large rotation. While there are few studies which extract controllers from the mathematical expressions derived by ANCF, a robust controller design procedure using ANCF model was proposed by author. The proposed controller design method has a drawback that the controller performance depends on number of elements used in ANCF model, and larger number of the elements leads to inefficient design procedure. Therefore, the main aim of this study is to propose a dimension reduction method of a controller design procedure proposed by author's previous study. A flexible beam is introduced as a controlled object and the control torque is applied to one end of the beam. Control objective is to rotate the beam to the desired position as well as to suppress the residual vibration of the beam. In the proposed method, dimension reduction based on component mode synthesis is employed, and some modifications of the ANCF model are introduced for the effective application of dimension reduction. The validity of the proposed method is demonstrated by numerical simulations.
Structural health monitoring is intended as a mechanism to ensure the operation and to evaluate the durability of the structure whose use is expected during a long time. It reduces life-cycle costs with ensuring the safety and the reliability of the structural systems. In addition, the optical fiber sensing systems are used for structural health monitoring because the high accuracy measurement and the transmission line, can be combined by the optical fibers. On the other hand, accurate measurement of horsepower for a rotary shaft in ships is needed for higher fuel efficiency and the energy regulation in international shipping. The FBG (Fiber Bragg Grating) optical fibers sensing are applied to measure several strains at different location which are induced by the torsion for the rotary shaft rotating in 100-400 rpm. The measured data of the strains have to be transmitted to the outside of the rotary shaft to use the FBG optical fiber sensing. The optical space transmission system makes it possible to transmit the data of the strains on the surface of the rotary shaft to outside the measurement system. In this study, we propose to use FBG optical fiber sensor to the shaft horsepower meter of main rotary shaft in ship. The optical transmission efficiency of the FBG measurement system is studied by a static and rotational experiment. Based on the experimental results, we verify the effectiveness of the optical space transmission performance of the system, and of the metrics for its improving performance.
The various kinds of the electric personal mobility, which is one or two-seater, are being developed all over the world. These mobilities are applied into the substantiative experiment held in the several cities in order to investigate the effectiveness and popularity. The main specification of the personal mobility is the small footprint to reduce the parking space and alleviate traffic jam. However, the small footprint causes the deterioration of the posture stabilization. The authors are developing the personal mobility, which has a lean actuator to tilt the upper body for keeping the posture stabilization not only during turning motion but also on the uneven road surface. In this paper, the motion model considering yaw motion around roll axis is derived. In addition, the posture control method based on the motion model is proposed to realize the desired roll angle, which ensures the required range of the zero moment point. The effectiveness of the proposed approach is verified by the experiments using a prototype.
Ride comfort is an important issue in improving passenger comfort in an automobile. Quantifying ride comfort is difficult because it affects a person's emotions and physiology. In this paper, we measure brain activities using near-infrared spectroscopy to clarify the features of brain activities while sensing vibration. Hopefully, the results obtained in this study can be applied to quantify subjective evaluation for ride comfort. Moreover, we measured brain activities while sensing vibrations which are uncomfortable and not uncomfortable vibrations. Uncomfortable and not uncomfortable vibrations were determined on the basis of sensory evaluation. Results showed that the concentration of oxygenated hemoglobin (oxy-Hb) levels in the prefrontal cortex change with the sense of vibration. In addition, during uncomfortable vibration, the oxy-Hb level declined more than that while sensing not uncomfortable vibrations. In addition, we measured brain activities while sensing a vibration which is divided over subject's feeling to the vibration and found that oxy-Hb of the subjects sensing uncomfortable vibration declined in the prefrontal cortex. Therefore, we infer that decline of oxy-Hb in the prefrontal cortex is relative to an uncomfortable feeling.
As accuracy of industrial product was reduced by several vibrations of a machine tool, a tool and a workpiece during cutting, there are several countermeasures for machining field. Recently the M2052 was used for reducing vibration. The M2052 has a property of very high damping ratio for vibration, however it has low static stiffness and very expensive. On the other hand, we developed the technology for creating new materials with hybrid properties. In this research, the sintered alumina and magnesium composite with both high static stiffness and high damping ratio was developed and evaluated. The manufacturing method was firstly developed. Then the consisted materials for the composite were selected by using FEM analysis. Properties of the composite were evaluated. At last the composite was used for the structural material of the lathe, the machining properties of the lathe were evaluated for surface roughness of a product and tool life in the experiment. It is concluded from the results that; (1) the manufacturing method for new composite was established, (2) the sintered alumina ceramics, magnesium and epoxy resin were used for the composite with both high static stiffness and high damping ratio, (3) the machine tool using the composite is very effective for high accuracy of the product.
In hybrid electric vehicles (HEVs), an internal combustion engine (ICE) and electric motors (EMs) are equipped for improving the fuel consumption as well as the exhaust emissions. To improve them simultaneously, a well-organized energy management system (EMS) should be developed. In this paper, a novel EMS considering torque control is developed, in which a function called the torque control function is introduced. This function controls the driving mode, the target ICE torque, and the target EM torque. Numerical simulation of HEV is so numerically intensive that a sequential approximate optimization using a radial basis function network is adopted to determine the torque control function. CO2 and NOx are so closely related the fuel consumption and the exhaust emission, and they are then simultaneously minimized in this paper. A multi-objective design optimization is the formulated, and the torque control function is determined with a small number of simulation runs. The worldwide harmonized light duty driving test cycle is used to examine the validity of the proposed EMS using the torque control function.
Nowadays, infrared thermographic technology has been attracting attention in various industrial fields. We therefore focus on it as a novel method for monitoring surface tool temperature to improve end-milling conditions for difficult-to-cut materials. However, a problem has emerged; it is difficult to measure the tool surface temperature when there is a coolant because the coolant prevents monitoring of the surface of the end-mill tool. Thus, we developed a wireless tool holder system equipped with a thermocouple in the end mill to monitor the tool internal temperature under coolant conditions. In the present report, we compared the temperature measured by infrared thermographic imagery with that measured by a wireless tool holder system when end milling the stainless steel under dry coolant conditions. The thermocouple, which has a diameter of 1.0 mm, was used to ensure stable measurement in the proposed wireless tool holder. We obtained the tool temperatures by infrared thermographic imagery and by wireless tool holder equipped with a thermocouple at a sampling time of 1/30 of a second. We confirmed that the tool internal temperature measured by the wireless tool holder agrees with one calculated by FEM model based on infrared thermographic imagery. As a result, we demonstrated that the developed method with a wireless system is effective to estimate the tool temperature in end-milling processes and makes it feasible to measure it under coolant conditions.
Application of robotic systems to the field of joint biomechanics studies has been performing in the last 2 decades. While a variety of studies have employed commercially available articulated robots we have designed and developed a material testing machine-like 6-degree of freedom (DOF) robotic system for higher load capacity and accuracy. The previous system consists of serially linked 2 translational and 3 rotational axes and a translational axis. All the servomotors at the 6 axes are controlled by a PC through a high-speed motion network. In the present study, we developed a novel 6-DOF robotic system that has a decoupled mechanism consisting of serially linked 3 translational axes and serially linked 3 rotational axes. All the servomotors at the 6 axes are controlled by a real-time controller through the EtherNet and EtherCAT. With knee joints fixed to the robotic system, either force control or position control can be applied with respect to the 6-DOF knee joint coordinate system. The velocity-impedance control was modified and applied to the force control while the velocity control was applied to the position control. The clamp-to-clamp stiffness of the novel robotic system was 541-1027 N/m and 262-355 Nm/rad which are more than 1.5 times higher than those of previous system. Responses to a step-function force input and a ramp-function force input were faster and more precise in the novel system than in the previous system. Moreover, joint forces and moments during 2-DOF and 6-DOF joint loading tests were controlled more precisely in the novel system than in the previous system. These results indicate the superiority of the novel robotic system over previously developed robotic systems. We believe that, with the system, it is possible to simulate physiological situations of the knee joint such as slow gait, standing up from a chair, and so on.
Owing to the population aging, it is expected that the number of patients undergoing acetabular bone and hip joint disease will increase. A total hip arthroplasty (THA) is one of the treatments for serious disease of hip joint. However, in the situation of massive acetabular bone loss, an acetabular reconstruction cage is additionally needed to reconstruct the hip joint. In this study, we focus on the acetabular reconstruction cage. The conventional cage is mainly made of metal. However, due to the lack of mechanical biocompatibility, there is a serious problem of ‘stress shielding’ of metal. The acetabular reconstruction cage made of CFRP could be possible to reduce the stress shielding, but the applicability for strength should be guaranteed. Therefore, the purpose of this study is to develop a numerical modeling method for acetabular reconstruction cage, and estimate the mechanical behaviors of bone and the cage. According to the numerical simulation, relative displacement of CFRP cage to bone was almost the same as Ti-6Al-4V cage. Moreover, strain energy density of CFRP was higher than Ti-6Al-4V in a wide range. Therefore, it was concluded that CFRP enables to design acetabular reconstruction cage which is more excellent for restraint of bone atrophy and promotion of bone remodeling than ready-made without influence on micromovement.
The aim of this paper is to build a methodology to predict the evaluation of vehicle's dynamic performance. At the evaluation process, driver is integrated into driver-vehicle system. Therefore, if we estimate the evaluation grades, a specific mechanical property of vehicle is not sufficient but multilateral properties related to driver's characteristics are required. On experiment side, there are two way: measuring vehicle responses related to driver feeling (open-loop approach) and marking achievement level of driving task related to driver's driving intention (closed-loop approach). On analytical side, open-loop approach is easy to execute with detailed vehicle model, closed-loop requires optimal control methods which demands strong restriction to model complexity. The primary reason for model limitation comes from incompatible formulation in jacking force, a part of load transfer expression among each wheel. To settle this problem, this paper investigated the problematic part of jacking force and inserted virtual mechanism to convert tire lateral forces into load transfer with jacking force. Along with this formulation, verification procedure to check the tolerance of load transfer disparity is built. When optimal control calculated vehicle motion, path following vehicle model with correct jacking force expression identify the accuracy of computed result. As a result of these procedural steps, practical level vehicle model, including tire load transfer mechanism, is now applicable to optimal control problem. For exemplify the usefulness of this methodology, simulation of lane change task with different load transfer property (roll stiffness distribution) is shown. When we use driver modeling for closed-loop simulation based on forward dynamics, there always exists ambiguity of the modeling. With optimal control simulation, we can specify driver's driving intention with terminal constraints and cost function more clearly. This paper's methodology expands the possibility to estimate the evaluation of vehicle dynamic performance on closed-loop simulation.
For the design of steering assistance system when running at high speed and modeling of a driver model necessary to effect evaluation and inspection, goal of this research is to make the driver model which models the driver's steering torque over a series of steering behavior. First step of this research, modeling of a driver steering in high-speed running is targeted for the steering torque behavior during the lane change that a driver steers actively and lane keeping that a driver keeps the lane under the crosswind disturbance passively. So the modeling for the steering torque behavior is proposed considering the lateral deviation in the front view point and the reaction torque from the steering wheel. It is proposed that the steering torque state transition changes from a course change action to a lane keeping action. It is confirmed that reproducibility of lane keeping action to an experimental result improves. Significant test did the driver parameter and its feature is made clear.
Space Situational Awareness (SSA) has been recognized to be important for safe space activities. As low-thrust propulsion technology becomes increasingly popular, SSA for low-thrust spacecraft may become an area of increasing interest. In this paper, we propose an orbital estimation method to predict the long-term evolution of spacecraft trajectory under unknown low-thrust acceleration. In particular, by the use of the perturbation theory and a nonlinear Kalman filter, long-term variations of orbital elements and thrust accelerations can be estimated from observation data of mean orbital elements. Performance of our method are evaluated for both controlled and uncontrolled orbits.
As low-thrust propulsion technology becomes increasingly popular, orbital estimation for low-thrust spacecraft may become an area of increasing interest. More frequent use of low-thrust propulsion to place satellites in orbit gives more opportunities for collisions and radio frequency interference as these spacecraft travel slowly through altitude ranges. The purpose of this paper is to develop a method for estimation of the osculating orbital elements for low-thrust spacecraft. To overcome the instability of the estimation problem with low-thrust acceleration, we estimate the mean elements instead of osculating elements. By use of the averaging technique, Hudson and Scheeres proposed an analytical model of secular variations of orbital elements under thrust acceleration. The resulting averaged equation has a nice property in which only a finite number of Fourier coefficients of the thrust acceleration appear because of the orthogonality of the trigonometric function. Based on the nonlinear state equation representation for the extended state variables which include not only orbital elements but also unknown Fourier coefficients, mean orbital elements and thrust history are estimated from perturbed observation data of mean orbital elements. Then, the mapping from mean to osculating elements which is derived from the perturbation theory is used to estimate the osculating elements. The proposed method is demonstrated through numerical simulations.