Delayed fracture susceptibility of 1.8 GPa-class ultra-high strength bolts was evaluated by an outdoor exposure test. Low-alloy steel bars with a chemical composition of Fe-0.4%C-2%Si-1%Cr-1%Mo (mass%) were quenched and tempered at 500 °C for 1 h, caliber-rolled at 500 °C with a rolling reduction of 78%, in order to create fail-safe steels (FS steels) with an ultrafine elongated grain structure. Subsequently, FS steel bars were formed into JIS M12 hexagon head bolts with a nominal length of 60 mm (FS bolts). Bolt heading was performed at 700~730 °C, and screw part was formed by thread-rolling at 500 °C to maintain the ultrafine grain structure with a strong <110>//rolling direction fiber texture. Conventionally quenched and tempered bolts (QT bolts) with a tempered martensitic structure were prepared for comparison. A steel plate was fastened by the bolts on 23 April 2013, and the outdoor exposure test was started on 21 May 2013 in Miyako Island test site of Japan Weathering Test Center. The bolt fastening force was 122 kN (=0.85 σ0.2 at thread part) for FS bolts and 89 kN (=0.70 σ0.2 at thread part) for QT bolts. The outdoor exposure test demonstrated an excellent delayed fracture resistance of FS bolts at the ultra-high tensile strength of 1.8 GPa; FS bolts have not been broken for 53 months, in contrast to QT bolts exhibiting delayed fracture. Intergranular cracking along the prior-austenite grain boundaries was commonly observed in the broken QT bolts. The accelerated laboratory test using tensile tests of pre-hydrogen-charged specimens and immersion test (30 °C, pH2) showed that the FS bolts had high resistance to hydrogen embrittlement, and it was in good agreement with the result of outdoor exposure test of the FS bolts.
This paper discusses the surface modification processing of Co-elinvar alloy (Fe-26.50mass%Co-9.50mass%Cr-15.50mass% Ni-0.50mass%Mn-0.30mass%Si) using Na2SO4 electrolyzed oxidizing water (hereinafter to as EO water). Co-elinvar alloy is widely used as the material of watch main hair spring. To improve the disentangled characteristics of hair spring after shape processing, it is necessary to roughen the surface. First, the roughening effect of Na2SO4 EO water on the surface of Co-elinvar alloy was elucidated by immersion test. The result of immersion test showed that when using supersonic together, compared with the case of only immersion, the scar of etching in test pieces surface becomes more homogeneous, but the section size and the Young's modulus of sample pieces decrease. Also, if processing time with supersonic use is optimization, the surface roughness becomes smooth and stronger. Next, the relation between roughening effect of Na2SO4 EO water and when it was produced was clarified. The results showed that if it was produced within 180 minutes, etching rate of Na2SO4 EO water was not influenced by elapsed time and becomes constant approximately, and the micro- shape of the surface isn't influenced by the elapsed time, it was smooth. By this study, we received the suggestion that Na2SO4 EO water could be applied to surface processing such as the roughening process of Co-elinvar alloy.
Image-based deformation simulation of microstructures in metals is attracting attention; however, the data conversion processes from the images of microstructures into the geometric models for the deformation simulation are now inconvenient, and there is a possibility that it prevents diffusion of the image-based simulation. In order to solve the problem, we developed an interface to convert the data of crystal orientation maps obtained by Electron Back-Scatter Diffraction (EBSD) patterns into that of geometric models for Crystal Plasticity Finite Element (CPFE) analysis. The interface incorporates several functions for data cleaning and coarse graining of the microstructures: functions to narrow down the limits of Eulerian angles presenting crystal orientations, integrate crystal grains with similar crystal orientations, eliminate small crystal grains, select representative crystal orientation in each crystal grain, and so on. The interface was applied to an orientation map of polycrystal microstructure in pure titanium, and the course-grained geometric models were successfully obtained. Image-based CPFE analysis was conducted using the geometric models with different number of finite elements. The numbers of crystal grains were assumed to be around 50 in any geometric models. A dislocation density dependent constitutive equation was employed and uniaxial tensile loading was applied to the geometric models by the forced displacement. The results showed that spatial distributions of stress, strain, and dislocation density were good agreement among geometric models with different number of elements in both elastic and plastic ranges while values of the strain and dislocation density showed quantitatively dependency of the number of elements on their distributions in the plastic ranges. These features indicate that the qualitatively similar results can be obtained using the developed interface on the condition that coarse graining of the microstructures does not occur even though the number of elements is changed.
Fiber reinforced thermoplastics (FRTP) attracts attention as a lightweight material for mass-produced automobiles due to advantages such as excellent formability and recyclability in addition to high specific strength and specific rigidity. Many factors influence the improvement of the mechanical properties of FRTP. We have revealed that the tensile strength of injection-molded glass fiber/polyamide66 (GF/PA) improves as the reinforcement fiber diameter decreases in the wide strain rate range in previous researches. In addition, it was suggested that by using a strength prediction model of discontinuous fiber reinforcement, if the strength can be obtained for one diameter, the strength can be predicted for other diameters. In this study, we investigated the mechanism of the strength enhancement of the GF/PA associated with thinning of the reinforcement fibers and increase of the strain rate. To ascertain the interface properties, single-fiber pull-out tests were conducted on the GF/PA and it was confirmed that the interfacial shear strength (IFSS) of the GF/PA had strain rate dependency. The strength prediction of the GF/PA with the strain rate dependency of IFSS taken into account showed values closer to the experimental values than the values obtained from the prediction with an assumption that IFSS is constant regardless of the strain rate. Furthermore, investigating the factor of the increase in strength due to the thinning of the fibers suggested that the increase of the fiber strength is the dominant factor.
Carbon nanotube yarn, which is an aggregation of Carbon nanotubes (CNTs), enables CNTs to be used on macro scale. However, tensile strength of the CNT yarn is much lower than CNT itself, and improvement of the mechanical properties is a challenge for practical application of the yarns. CNTs composing the yarns include some defect structures and impure materials, and their presence can cause a decrease in tensile strength of the yarn. In this study, untwisted CNT yarns were fabricated by dry spun method and graphitized at a temperature of 2800°C for the purpose of improving mechanical properties. Additionally, strength of a CNT composing the yarn and interactive force between the CNTs were evaluated to clarify strength development mechanism of the graphitized CNT yarn. Crystallinity of the CNT yarn was improved more than ten times, and defect structures and impure materials was removed by the graphitization treatment. As a result of single fiber tensile tests, strength of the yarn was increased by 20~35% after the graphitization. On the other hand, strength of the CNT composing the yarn was decreased. The breaking form of the CNT yarn was changed from pulling out of CNT bundles to rapture of the bundles by the graphitization, indicating an increase of interactive force between the bundles. In addition, as a result of pulling out simulations by molecular dynamics method, it was indicated that the pulling out of the CNT bundles were suppressed by increase in van der Waals force. Consequently, the improvement of mechanical properties of the untwisted CNT yarns was not due to the change in the strength of the CNT in the yarns but the main cause was the increase in the interactive force between the CNTs.
The gas-lift effect appears in various types of gas-liquid two-phase flows. Information on the effect in a still liquid however is very limited compared to that in a moving liquid. Experiments were carried out in this study on the case that air bubbles rose in sill water contained in a vertical circular pipe made of transparent acrylic resin. The flow pattern covered bubbly and slug flow regimes. The effect is composed of bath surface elevation effect and liquid flow induction effect. The latter effect was quantitatively evaluated in terms of the pipe friction loss in the pipe. An empirical equation on an apparent frictional coefficient was proposed for predicting the loss. The experimental results reveal that the liquid flow induction effect is weak in the bubbly flow regime, while prevails significantly in the slug flow regime.
We have elucidated the aggregation phenomena in a suspension composed of spherical magnetic particles in an alternating magnetic field by means of Brownian dynamics method. The relationship between aggregate structures and heating phenomena has been discussed using the hysteresis loops of the magnetic field-magnetization curves, which were obtained from Brownian dynamics simulations. A large heating effect is inevitably necessary in applying a magnetic particle suspension to magnetic hyperthermia treatment in the medical engineering field. We here focus on the Brownian relaxation mode of magnetic moments of particles as the factor inducing the heating effect. The main results obtained here are summarized as follows. In the situation where stable chain-like clusters are formed in the field direction, the magnetic particle-particle interaction induces a significant delay for the magnetic moments inclining in the alternating magnetic field direction. These chain-like clusters respond to a change in the magnetic field without collapse and reformation of the clusters, by the magnetic moment of each constituent particle rotating to incline in the field direction. These behaviors of chain-like clusters in an alternating magnetic field exhibit a hysteresis loop with large area in the magnetic filed-magnetization curve, which gives rise to a significantly large heating effect. On the other hand, in the situation where large clusters are formed but these clusters do not strongly tend to incline in the field direction, the area of the hysteresis loop becomes small and therefore a large heating effect cannot be obtained.
Homogeneous charge compression ignition (HCCI) engine has some advantages such as high efficiency and low emissions. On the other hand, it has challenges that it is difficult to avoid knocking and misfire. Therefore, the precise control system of HCCI combustion is necessary. In this paper, firstly, a control-oriented model which was discretized to several representative points in 1 cycle of an HCCI engine was developed. Secondly, a control system based on the modern control theory was constructed. It consists of a feed-forward controller and a feedback controller with Kalman filter to estimate state variables. The controller based on only a sole linear model has a disadvantage that its performance deteriorates except when the controller works at equilibrium points. Therefore, a gain-scheduling controller was introduced to the nonlinear system. The control simulation was conducted for the nonlinear plant model with the developed gain-scheduling controllers, and both IMEP and the in-cylinder pressure rising rate were controlled over a wide range IMEP.
A simple and quick in situ measurement technique for liquid viscosity is expected to enhance the quality of products and the production efficiency in many fields of engineering such as food production, film coating, medical application, and so on. For example, the in-process viscosity measurement is required to determine the economic feasibility of recovering hydrocarbon from subterranean strata. The real-time viscosity monitoring of organic liquid thin films can realize the control of the rheological and morphological characteristics of film-devices as well as the quality of film. Furthermore, the simple and fast measurement of blood viscosity realizes a diagnosis of cardiovascular disorders with new perspective. Therefore, in situ viscosity measurement could provide a breakthrough in sensing under specific conditions. However, conventional viscometers are inapplicable to in situ measurement because the contact-manner is utilized in these methods, and these methods require a long time for measurement. In the present study, a novel optical hand-held viscosity sensor (OHVS) has been developed to realize in situ viscosity measurement. The proposed sensor enables non-contact and high-speed viscosity measurement based on the optical measurement method called laser-induced capillary wave method. In order to robustly detect the optical signal which contains the information of the viscosity under hand-held condition, we developed the incident angle control system and integrated on the compact handy sensor. Through the experimental study, the irradiation angle was stabilized vertically under hand-held condition by the incident angle control system, and the standard deviation of the irradiation angle during control was smaller than 0.03 degrees that was enough to detect the viscosity signal. Finally, the optical signal which contains the information of viscosity has been observed by OHVS under hand-held condition. The applicability of the proposed sensor for the simple and quick measurement was verified.
Liquid-vapor phase distribution and displacement in the capillary evaporator of loop heat pipes (LHP) is a key phenomenon to understand the steady state and transient behavior. However, the phenomenon has not been investigated sufficiently thus far. In this study, the liquid-vapor phase behavior on the contact surface between the wick and evaporator case at start-up is observed with a transparent evaporator case coated with an ITO heater. Visualization experiments are conducted during the LHP operation at 0.59 - 5.6 W/cm2 of heat flux applied to the evaporator. Nucleate boiling and temperature drop on the evaporator wall by superheating are observed when the grooves and vapor line inlet are initially saturated with liquid. Right after nucleate boiling, the whole surface of the wick is dried instantaneously, then liquid in the compensation chamber (CC) wets the wick. In the imbibition, two regimes where the liquid filling rate into the wick is different are found. At a high heat flux, vapor pockets are observed at the contact surface between the wick and evaporator case even in a steady state. Thermo-fluid simulations which take into account disordered porous media and effective thermal conductivity of the wick obtained from directly solving a heat conduction equation in reconstructed porous media using X-ray computed tomography are conducted. The simulation results of evaporator wall temperature and saturation at the contact surface agree with the observation at 5.6 W/cm2 of heat flux. Both simulation and observation results show residual liquid phase along the three-phase contact lines within the case, wick, and grooves.
In this paper, a model of yarn considering stretching, bending and twisting motions is constructed. The proposed yarn model is based on rigid multibody dynamics and expresses the dynamical behavior of flexible yarn. The yarn model is made of successive computational units. The computational unit consists of a rigid sphere with mass, a massless cylinder and three sets of springs and dampers for stretching, bending and twisting motions. In the numerical simulation of the unwinding motion of a yarn from bobbin, the computational units located at the ends of a yarn are easily generated or extinguished. The proposed yarn model has the following features: it can easily treat the contact force interacting with walls, and it can reduce the computational cost. In this study, validity of the proposed yarn model is confirmed by comparing the numerical simulation results of unwinding motion of the yarn with the experimental ones. Furthermore, the torsional angles of the yarn rolling on the eyelet guide wall, which is difficult to be measured in experiments, is numerically investigated. Particularly, the occurrence of false twist is observed and explained.
Overhead traveling cranes are widely used at ports and factories, and they play an important role in mass transportation systems. The main problem with such cranes is that residual vibration of the cargo often occurs at the end of transportation. At present, prevention of residual vibration depends on the skills of the crane operator. Therefore, an automatic operation system for overhead traveling cranes is strongly desired for efficient and safe transportation. In this paper, a new type of open-loop control method is proposed for suppressing the residual vibration. This method is based on the fact that residual vibration is completely suppressed in a linear undamped system excited by an external force that does not contain the natural frequency component of the system. We apply this to a nonlinear damped system and develop an efficient method for determining a trolley trajectory that prevents residual vibration. Numerical simulations confirm that this method can prevent residual vibration. Furthermore, we employ a trigonometric series as well as a power series created by modifying Legendre polynomials in order to construct the trolley trajectory, then examine which is more advantageous for transportation. The results demonstrate that the power series exhibits a better performance in terms of the maximum swing angle of the cargo during transportation and limit of transportation time.
This paper proposes a transfer function of rotating shaft system considering both an open crack and anisotropy in bearing support stiffness, which are both fundamental characteristics often observed in the rotating machinery. Due to the interaction of anisotropy in bearing support and rotor crack, vibration component is generated without limitation. In this paper, the order of generated component is evaluated and a transfer function focusing on five vibration components is derived. Each transfer function is analyzed and characteristics of all resonances are explained theoretically. Then, the validity of this derived transfer function is confirmed by comparing with numerical simulation result. Furthermore, the experimental system of the rotating shaft supported by the bearing with anisotropic support stiffness is developed, and the harmonic excitation was added to this system by the active magnetic bearing. Several harmonic excitation experiments were carried out, and the resonances due to anisotropy in bearing support, rotor crack, and the interaction of anisotropy in bearing support and rotor crack were examined. The vibration characteristics of observed resonances showed quantitatively almost agreed results to the expected theoretical results. These theoretical and experimental results clarified the usefulness of the derived transfer function.
This paper proposes a new mechanism and a modeling method for continuum manipulators. The new mechanism is an anti-twist mechanism. Continuum manipulators have the merit of flexibility. However flexibility causes unexpected motions such as twisting under heavy loads. The proposed mechanism avoids only twist motion without affecting the other two bending motions. The mechanism is composed of 3 plastic parts. The effect of the proposed mechanism is verified by the experiments. The modeling method for continuum manipulators are used for inverse kinematics. It will make the motion of the tip more precise. Continuum manipulator has a nonlinear relationship between the input wire length and output manipulator configuration. A new model which uses minimum total potential energy principle is proposed. The validity of the proposed model is examined by comparison of the experimental results while the bending stiffness is changed. Both proposed new mechanism and model will make the continuum manipulator motion better.
In order to improve the noise and vibration characteristics of mechanical structures, it is well known that an identification of modal properties is important. Therefore, experimental modal analysis is widely operated for identifying modal properties represented by natural frequency, damping characteristics and mode shape from vibration test result. However, in the case that the damping characteristics is very small or large, it is difficult to identify the modal properties by the existing method. In the previous study, we proposed the identification method of natural frequency and damping characteristics for a lightly damped element. This method using simultaneous equations of the real and imaginary parts of frequency response function is the one degree of freedom method and can not be directly applied to a multi-degree-of-freedom system. In this study, we propose the identification method for a multi-degree of freedom system by using both simultaneous equations of the real and imaginary parts of frequency response function and mode separation method. First, it is explained that the theory of identification using simultaneous equations of the real and imaginary parts of frequency response function in one degree of freedom. Secondly, we investigate the identification accuracy and the analysis frequency range including the measurement error and non-targeted mode components. Finally, it is shown that identification result of modal parameters in multi-degree of freedom system using numerical analysis and its validity.
For pneumatic anti-vibration apparatus (AVA) used in the precision positioning field, the authors have pursued the possibility of applying Central Pattern Generator (CPG) and realized its application in order to suppress flow disturbance caused by the pressure variation of the compressed air supplied to the pneumatic AVA. In the past, CPG has been mainly used for generation of desired values, such as analysis of biological movement and motion control of a quadruped walking robot. On the other hand, CPG has been implemented in the loop of the control system to improve the damping ability of the structure by the mass damper. The authors have also tried to improve the suppression effect of the disturbance by implementing CPG in the same way. However, the background of determining the parameters of CPG is not shown in any relevant documents. Therefore, this paper describes the parameter setting method for implementing CPG to the pneumatic AVA in detail. In addition, the characteristics and performances of CPG which have not been mentioned so far are revealed. Concretely, when switch input and signs for CPG input stage are changed, the influence of these is verified. These are summarized as consideration for application of CPG to the pneumatic AVA.
In order to improve the efficiency of combustion engines, variable compression ratio (VCR) engine is researched. VCR engine changes the compression ratio according to its mechanical configuration. One of the solutions to construct VCR engine is the multi-link type. Multi-link type has an advantage for reducing high order shaking force which is the source of mechanical vibration. Since piston motion strongly influences shaking force, it is required to make the piston displacement profile close to sine curve. However, conventional combustion engine is designed based on four-link piston crank mechanism. Because of the design constraint due to four-design parameters regarding the four-link piston crank mechanism, piston displacement profile diverges from sine curve. In order to solve this problem, six-link piston crank mechanism is applied to VCR engine. Since six-link piston crank mechanism has six-design parameters, the piston displacement profile becomes closer to sine curve than that of the four-link piston crank mechanism. A Stephenson type six-link piston crank mechanism whose constitute four-bar mechanism is the double-crank mechanism is newly designed. Basic characteristics of VCR engine model, that includes the piston displacement profile and its similarity for sine-curve, and peak acceleration amplitude with respect to different compression ratio, was researched based on kinematic analysis. The obtained theoretical results are compared with experimental ones. As a result, experimental values almost agree with theoretical values.
Based on the worldwide situation, it is necessary for the Japanese mechanical industry to consider risk-reduction strategies that match real production site. We have established a new risk-reduction method named supportive protective system (SPS), which targets integrated manufacturing system (IMS). The aim of the SPS is to provide effective residual risk-reduction using a combination of appropriate information and communication technology (ICT) equipment without depending on workers’ attentiveness. Workers' qualifications and rights, the target machine, the work content, the place of the work and the operation time would become clear by introducing SPS. Under the SPS, work will only be allowed when ID information and the target machine of the tag held by a worker are matched with information from the control machine located in the work area. It is possible to prevent dangerous side errors caused by human. The SPS should be used in parallel with the "protection plan"—the education and training management. The SPS was developed with a combination of a time of flight 3D (TOF3D) camera and radio frequency identification (RFID) equipment in the present study. The SPS was experimentally introduced into an IMS site of company A, which produces large motors. The qualifications and rights to perform non-routine work tasks, such as cleaning or maintenance work at this site, were examined using the SPS. In addition, we examined the accuracy of the SPS in counting workers’ access to the workspaces. When using appropriate ICT, the SPS is an effective risk-reduction method that decreases the probability of errors derived from human error and intended unsafe behavior. The results of the present study demonstrated that the SPS might reduce risk when applying a TOF3D camera and RFID equipment. The SPS is an effective risk reduction method that does not depend on workers’ experience and ability.
Monitoring the operation status of machine tools using IoT is widely carried out in order to improve productivity. However, at manufacturing sites, a lot of legacy machines, which are old and lack the capability of sending data on their operation status to networks, are still in use because the average useful life of machine tools is more than 20 years. Therefore, we developed method for recognizing the operation status of machine tools using a spindle motor current acquired by a current sensor. Because this current is in proportion to the spindle torque, a conventional method recognizes the operation status when the current amplitude is above a threshold value. However, in a high-mix low-volume factory, the threshold value must be reset frequently because a drill and the cutting process change per order so the spindle torque varies. In contrast, we propose an automatic recognition method that can learn the variance in spindle motor current by unsupervised learning and with labelling scheme based on prior knowledge. We app..lied the proposed method to eight kinds of machine tools in a real factory, and the accuracy rate of the operation status estimation was more than 80% for all the machines. This result shows that all machine tools could be monitored by using this method.
Page turning technology is widely used in many applications, such as Automated Teller Machines (ATM) to deal with passbooks, automated book scanning machines to convert paper books to electronic books, and so on. Among them, ATM especially requires high reliability because ATM is used in unmanned operation. Therefore, in this paper, a new page turning roller is developed for a high reliable page turning process on ATM. ATM has to turn both a high stiffness cover page and low stiffness inner pages of passbooks. First, press force of the page turning roller is considered to turn a cover and inner pages stably. Next, we constructed a simulation model about the press force of the page turning roller and considered the shape of the page turning roller by using the simulation model. The developed page turning roller has the desired press force characteristic to turn a cover and inner pages stably. By applying the developed page turning roller, a page turning machine for ATM can stably turn cover pages and inner pages of passbooks.
Polishing processes are critical to high material removal rate and excellent surface roughness. To realize the highly-efficient polishing of glassware, which are used as materials for flat-panel displays, glass lens, substrates of magnetic disks, a new-type polishing pad composited with an epoxy resin and polymer particles was developed, in this study. Authors focused on a surface asperity of the polishing pad for improving the abrasive retention capability of polishing pads and the slurry invasive activity to the polishing area. For changing the hydrophilic property of polishing pads, various type polymer particles were added to the epoxy resin. The hydrophilic polymer particles can improve the polishing characteristics of a normal epoxy resin pad. Because wear rates of the polymer particles and the epoxy resin, a rough surface of the polishing pad generals in polishing process. The rough surface advances the slurry invasive activity. The polymer particles assist the epoxy resin to grip the abrasives on the polishing pad. The material removal rate increases with increasing in the grain size and the hardness of the polymer particles added in the polishing pad. The addition amount of the particles and the hardness of epoxy resin affect the polishing characteristics of the polishing pads. The perfect addition amount and the hardness of epoxy resin were discussed.
There have been many reports dealing with the motion accuracy of a five-axis controlled machining center. However, there have been few reports dealing with a synchronous accuracy between the spindle rotation and the feed driving motion. In the present report, we propose a novel method to control the cutting trace shape on machined surface in radius end milling, focusing on high repeatability of period in a fixed cycle feed motion to keep a synchronous motion between the spindle rotation and the feed driving motion. Moreover, we attempt to estimate the quality of machined surface with a proposed method for radius end milling of hardened die steel. As a result, a proposed machining method is found to be effective to improve the machined surface quality for a finishing process.
This paper proposes a new topology optimization method for steady state incompressible viscous flow. Since fluid flow profiles, such as velocity and pressure profiles, describe specific behavior on walls that fluid contacts, defined boundary conditions in such profiles should be precisely evaluated. The immersed boundary method is implemented here to represent fluid flow profiles, and enhanced accuracy is obtained through their rigorous use during optimization. The topological derivative is derived for the sensitivity analysis and the finite volume method is used for numerical analysis during the optimization process. Several numerical examples are provided to confirm that the optimal configurations accurately represent flow distributions, in contrast to previous research in which a specific treatment for internal wall boundaries was not considered.
In this study, an automatic process planning system for end-milling operation is proposed, in which CAM operator's intention for process planning is considered. In the previous process planning systems, the machining sequence is calculated geometrically, based on the Total Removal Volume (TRV) and the machining region split from TRV. However, it remains difficult to determine the best machining sequence from the large number of the calculated machining sequences. The previous process planning systems also do not consider CAM operator's intention in the determination of the appropriate machining sequence. First, our new process planning system stores the priority of machining feature and the geometrical properties of the selected machining region when a CAM operator decides the machining sequence. After storing the priority of machining feature and the geometrical properties, the appropriate machining sequence can be automatically determined by referring this information. CAM operator's intention, which is involved implicitly in the stored geometrical properties of the machining region, can be applied to decide machining sequence. A case study was conducted to show the effectiveness of our new proposed process planning system. In the case study, user-specific machining sequences were automatically determined based on the implicit relation among the geometrical properties of the machining region and the individual CAM operator's intention.
Heart rate is one of the biological rhythms and has fluctuating properties. This fluctuation is induced by various causes, and it is said that, by analyzing the fluctuation, useful information on the health state such as the stress index and prognosis of cardiovascular system can be obtained. However, because heart rates are usually measured with cumbersome sensor devices or electrodes, the measurement of instantaneous heart rate, which has equivalent information to heart rate variability, is also difficult to be conducted on a daily basis. To solve this problem, we are developing systems to detect instantaneous heart rate from output of a soft rubber-based tactile sensor put on a bed. We expect that information on heart beat is contained in pressure time series obtained from the tactile sensor. Using a signal processing technique called complex demodulation, the instantaneous frequency of the oscillation in the heart rate frequency range can be obtained from the pressure time series. To confirm that the detected instantaneous frequency coincides with the conventional instantaneous heart rate obtained from ECG, we measured ECG and pressure time series from the tactile sensor simultaneously, and compared the detected instantaneous frequencies using cross-correlations. The results were quite promising. This shows the possibility that we may be able to develop a nonrestraint health monitoring system using a tactile sensor. The system may record heart rate variability on a daily basis, and detect stress indices and symptoms of diseases. In this paper, we propose the instantaneous heart rate detection method from tactile sensor output, and show its promising experimental results.
An infrasound sometimes occurs in an industrial field like a paper factory and it becomes a cause of complaints from neighborhood resident of the factory. The infrasound has acoustic features of a long wave length and little effects of conventional countermeasures such as an acoustic absorbent and sound insulator. Therefore once it happens, it has been difficult to do countermeasure. This paper describes that the rotating stall occurred in a fan (IDF: Induced Fan) becomes the cause of the infrasound generated from the EP (Electric dust collector) set in the factory. This is a very scarce and interesting phenomenon. So it is considered of value to describe the event. A lot of measurements were carried out to clarify the cause of this event. As a result, the cause of the infrasound is the resonance of the EP and the cause of the resonance is the rotating stall of the fan. Therefore the countermeasure is to exchange a new fan with P-Q characteristics of a large gradient (∂p/∂Q). As a result, the infrasound disappeared.
In the preventive safety field, AEBS (Advanced Emergency Braking System) has been widely spread to the market. AEBS is composed of alert-braking phase and full-braking phase. When AEBS functions, ABS (Antilock Brake System) is often used simultaneously. ABS has the work braking to be a target tire slip ratio which is constant in general. In order to use braking force to its maximum range, it is desirable for ABS to use information of the road surface condition, the road friction coefficient. Because the relations between the tire slip ratio and the tire braking force are varied with the road friction coefficient. However, the road friction coefficient estimator is difficult to be realized. As the control of ABS depends on only tire slip ratio, it is impossible to generate enough tire braking force on the various road surface conditions. In this paper, we propose a method to estimate the road friction coefficient during alert-braking phase. In addition, we changed the target tire slip ratio required by ABS and hastened the start timing of full-braking phase based on the road friction coefficient. The possibility of reduction of the collision speed compared with the conventional system was shown by using the method mentioned above.
In recent years, engineering technology has become essential for our daily life. We cannot live without civil engineering or information technology even for one day. At the same time, as utilizing technologies sometimes infringe human rights, many laws and regulations exist in our society. In spite of importance to collaborate with legal experts for engineer to realize implementation of their new technologies into society, and a lot of efforts of the Professional Committee of Law and Technology in the Japan Society of Mechanical Engineers, it has not been understood in Japan for a long time. Many issues have been discussed relating to the growing concern about autonomous vehicles, but it seems insufficient from the view of legal and engineering collaboration. In this paper, a case study is introduced that is an example of legal engineering showing countermeasures for legal issues to realize autonomous shipping performed by Robotics Laboratory in Tokyo University of Marine Science and Technology. Furthermore, knowledge obtained by this case study is proposed as legal engineering which presents how engineers may identify legal issues and perform risk assessment of their developing technologies. By communicating with legal experts, engineers might be able to perform technology development with legal risk mitigation and take a role for rulemaking especially in the field of soft-law.
The purpose of this study is to design a sustainable supply chain of wood biomass fuel by applying a mixed integer programming (MIP: Mixed Integer Programming). To evaluate the effect of routing choice quantitatively, two objective functions are defined; cost minimization and energy consumption minimization. In the Railway case, 4 t truck can be used to transport wood logs and pellets, and railway can be used to transport pellets. In the Heavy truck case, three types of trucks (4 t, 10 t, 20 t) can be used to transport wood logs and pellets. As a case study area, five prefectures of Japan's Tohoku region are selected. The computational result provides that supply cost becomes 17,058 - 24,773 JPY/tpellet. In any case, since cost of pellet supply is lower than distribution price of pellet which is 45,000 JPY/tpellet in Japan, letting break-even point to distribution price of domestic pellet, this system has competitiveness to Japanese pellet suppliers. Effective utilization rates of biomass resource through supply chain show 0.802 - 0.834 that is higher than the previous study using waste woods. The CO2 reduction by coal substitution shows 0.967-1.029×106 t-CO2/year which shares 65 - 69 % of CO2 emission from the coal combustion.