For the development of industrial heat pump system supplying a high-temperature heat source, the application of chevron type plate heat exchanger is being considered. In the present study, experiments and numerical simulation on flow characteristics in single chevron channel with chevron angle 30°, 45° and 65° were respectively performed. In the experiment, the pressure drop of the whole chevron channel and local pressure drops in each chevron channel were measured and path lines were also observed. Besides, numerical simulation reproduced the experimental results well. From both of the experimental and simulation results, it was confirmed that the pressure drop of the chevron channel became larger with increasing the chevron angle due to the strong mixing of fluids in the respective furrows of adjacent chevron plates especially in the high chevron angle channel. In such the high chevron angle channel, velocity and pressure drop gradient distributions were almost uniform in the channel width direction normal to main flow. While, in the small chevron angle channel, the fluids mixing between furrows of adjacent plates was weak and the velocity and pressure drop gradient distributions were markedly large in the width direction. Furthermore, it was found that large pressure drops occurred in the inlet and outlet regions where the channel had flow width expansion and contraction, respectively. The large pressure drops in the inlet and outlet regions affected the overall pressure drop in the chevron channel, especially in the low chevron angle channel. For each chevron angle channel, the local friction factor was obtained and the loss coefficient for the flow expansion and contraction at inlet and outlet regions was determined. Based on these results, the prediction method of overall pressure drop in the chevron channel was proposed.
Railway vehicles are equipped with many kinds of machines such as traction diesel engines and their failures sometimes lead to service disruptions and accidents. Vibration monitoring systems are expected to prevent their failures by detecting their abnormalities at an early stage. In order to make an effectual action after abnormal vibration detection, it is necessary to make a root cause diagnosis. To address this issue, a simple diagnosis method is proposed in this paper. In the method, a measured vibration octave spectrum is divided into three frequency bands and abnormality detections are conducted for the spectra to narrow down the root cause of the vibration. A one class classification method, which is an anomaly detection method in machine learning, is used in the abnormal vibration detection to make a general purpose vibration monitoring system. In addition, the ratios of abnormal vibration are calculated for the three frequency bands to show the progress of the fault. The effectiveness of the method is verified using vibration data acquired on simulated abnormality tests of traction diesel engines, i.e., auxiliary drive shaft failure test and engine abrasion test. The test results show that the proposed method is effective in detecting the abnormality and diagnosing the cause and the degree of the failure.
In case of analyzing the wind turbine design conditions and power productions accurately, the wind data at hub height is generally ideated for simulation. Recently, due to the increase in the size of the wind turbine, it is difficult to measure wind data of hub height by the cylindrical observation tower. Therefore, lattice tower mast is adopted and there are cases where high altitude measurement is performed instead of cylindrical tower mast. However, even in case of measuring wind data using lattice tower mast, there are some uncertainty of flow distortions by tower shadowing. This paper shows a study on wind speed correction method of lattice tower mast using CFD simulations (Fluent). As a result of performing the wind speed correction using the inflow wind speed ratio by CFD calculation, the uncertainty of corrected wind speed fell by less than 1 % which is recommended by IEC 61400-12-1.
The neck is an important body part that links the head and chest sections. However, very few analyses of cervical movement derived from muscle contractions have been conducted with numerical simulation. This study aimed to construct a multi-body model of the neck comprising the bones, muscles, and ligaments (including the intervertebral disc) and to apply flexion and extension movements to analyze the behavior of each cervical segment. We created bone models (including cervical vertebrae C1-C7) from X-ray computed tomography (CT) images of the upper half of the human body. Each bone model was bound by 17 types of ligaments constructed as 51 wire models. We set six types of muscles as the protagonists for neck flexion and 12 types for the neck extension. Muscle strength was defined with a parallel contraction element model and an elastic element model. The intervertebral discs represented five spring models with repulsion characteristics on compression and attraction characteristics on extension. The neck section could flex up to 38.1° and extend up to 61.0° with contraction in the flexor and extensor models. The maximum cervical segment angles on flexion and extension were measured at C0-C1 and C4-C5, and their contribution rates were 20.7% and 19.3%, respectively. Each cervical segment angle when flexing and extending closely matched the experimental results measured by other studies. The centers of rotation for cervical segments from C2-C3 to C4-C5 on maximum flexion were different from those in previous experimental result. This may be because of the settings pertaining to the interspinous ligament, nuchal ligament and supraspinous ligament. On the other hand, our results for maximum extension were consistent with past experimental result. An improved neck model will allow the analysis of cervical segment movement through the joint restrictions based on damage to the ligaments and muscles or arthrodesis when flexing and extending.
Some organisms using undulatory locomotion show the transition of the swimming frequency and the wavelength of the undulation. This transition of swimming behavior is achieved by sensory feedback, and may have the role to cope with the environmental change. Especially, one of the nematode: Caenorhabditis elegans can modulate its frequency from approximately 0.3 to 2 Hz, and vary the wavelength of undulating body from less than a single body length to almost twice the body length. With this modulation, C. elegans achieves the movement under the conditions from in water to on the surface of an agar. Inspired by this finding, we propose the adaptive control for the multilink swimming robot because the environmental change demands a mobile robot the change of the pattern of the locomotion. Proposed adaptive control employs the sensory feedback from joint angles to inputs of actuators at joints to generate the self-excited oscillation. At first, we construct the multilink model in fluid with sensory feedback. After that, we construct the linearized model to obtain the relationship among the external resistive force, parameters of the multilink model and the swimming frequency by using the eigenvalue analysis. We confirm whether the proposed adaptive control simulates the modulation of undulation like C. elegans. Moreover, we specify parameters of the multilink model which are related to the frequency and wavelength of undulation significantly.
This paper presents a method of data reduction for long-term robotic mapping using a 2D laser scanner. The proposedmethodintroducesobservationfrequencyintotheoccupancygridmap, andcalculatestheimportance of each scan through the ray-casting algorithm. The importance of a scan is high if the scan observes many occupancy cells which are new in terms of the observation frequency. Also, the method calculates the coverage of a subset of scans to examine how the subset covers the map well. Then, the method determines the threshold of the scan importance according to the designated coverage, and removes the scans which are less important than the threshold. The reduced laser scans improve computation time and memory consumption for pose adjustment and map reconstruction in loop closure. Experiments using real-world data show the proposed method effectively reduces data size and computation time in robotic mapping.
The field of multi-robot systems (MRSs), which deals with groups of autonomous robots, is recently attracting much research interest from robotics. MRSs are expected to achieve their tasks that are difficult to be accomplished by an individual robot. In MRSs, reinforcement learning (RL) is one of promising approaches for distributed control of each robot. RL allows participating robots to learn mapping from their states to their actions by rewards or payoffs obtained through interacting with their environment. Theoretically, the environment of MRSs is non-stationary, and therefore rewards or payoffs learning robots receive depend not only on their own actions but also on the action of other robots. From this point of view, an RL method which segments state and action spaces simultaneously and autonomously to extend the adaptability to dynamic environment, named Bayesian-discrimination-function-based Reinforcement Learning (BRL) has been proposed. In order to improve the learning performance of BRL, this paper proposes a technique of selecting either of two state spaces: one is parametric model useful for exploration and the other is non-parametric model for exploitation. The proposed technique is evaluated through computer simulations of a cooperative carrying task with six autonomous mobile robots.
Power assist devices are worn by users, directly transmit actuator power to the users’ bodies, and can deliver assistance in activities of daily living, such as load lifting. In this study, we built a wearable power assist device for lower limbs driven by pneumatic actuators. Pneumatic power assist devices are safe for users, owing to the compressibility of air; however, the weight of the devices and assist torque often have a negative effect on the wearer’s body balance. Here, an assist control strategy is proposed for the pneumatic power assist device. In this strategy, the relationship between the lower-limb joint angles and the center-of-gravity (COG) of a human body is represented based on a simplified human body model during squatting. Assuming that the anterior and posterior movement of the COG follows the knee joint flexion and extension, the desired COG position is calculated from the knee joint angle measured with a sensor. The desired hip and ankle joint angles are found with the desired COG position, and the desired assist torque is obtained with these joint angles based on the human body model. The power assist device based on this principle was worn by research subjects, and its assistive performance was evaluated through experiments from the viewpoint of the COG fluctuation and muscle activity reduction.
SU8 is a negative photoresist shows superior characteristics of heat resistance and chemical resistance. And, it is used to make high-aspect ratio micro structures such as master of electroforming. However, it is extremely difficult to remove SU8 from substrate. Researchers have investigated a means of SU8 removal. Therefore we proposed a new SU8 removal method “DI water (H2O) and lithium chloride (LiCl) doped NMP” which promises swelling furtherance of SU8, and we demonstrated that the new method could remove fine SU8 patters from substrate at proper level. The mechanism of SU8 fine patterns removal is presented as follows. A doped NMP broadens the width of SU8 patterns by swelling effect and reduces buckling stress of SU8 patterns. SU8 patterns reducing buckling stress increases the potential of buckling.
The ductility factors of nonlinear SDOF systems at Service Limits Ds “using elastic analysis design” in JEAC4601 are investigated, and it was confirmed that the ductility factors depend on the natural frequencies of systems, seismic motions and constant loads. Based on the above results, an acceptance criterion of components to prevent ductile failure and plastic collapse is proposed. The criterion is given as a limit of ductility factor for Service Limits Ds “using elastoplastic analysis design”. The proposed limit of ductility factor allows single state for nonlinear systems, and doesn't depend on the natural frequencies of systems, seismic motions and constant loads.
In this study, vibration characteristics of a single-degree-of-freedom linear oscillator with the fractional order derivative are examined in terms of the critical damping over a wide range of the order of the fractional derivative by using numerical analysis. Two types of the definitions of the critical damping used in the previous studies are considered. It is shown that (i) the critical viscoelastic damping ratio changes according to the order of the fractional derivative and its minimum value for both types of the critical damping is less than 1; (ii) no critical viscoelastic damping ratio is observed in a certain range of the order; (iii) the difference in the existence of the critical damping between the oscillators with the derivative of order 1/3 and 2/3 is caused by the change of the behavior of a component of the response corresponding to one of the roots of the characteristic polynomial for the oscillator. Finally, the impulse response characteristics are classified into three classes depending on the order of the fractional derivative and viscoelastic damping ratio of the oscillator.
Argon ion sputter-etching of SUS420J2 and SUS316 stainless steels was carried out at a power of 250W for 10.8ks to form cone-shaped sharp protrusions with bottom diameter of 10-30 μm and fine quasi-column-shaped protrusions with diameter smaller than 500 nm respectively by using a radio-frequency magnetron sputter-apparatus. Effects of two types of plasma-nitriding on gripping ability were examined; one is the nitriding of both steel specimens using nitrogen gas of 0.53 Pa mixed with argon gas of 0.67 Pa at a power of 50W for 1.8 ks to maintain the original sharpness of protrusions, and another is the nitriding of SUS420J2 steel specimen using only nitrogen gas of 1.2 Pa at a power of 200 W for 7.2 ks to obtain the cone-shaped protrusions with round top. The coefficient of static friction, or gripping ability, of the plasma nitrided sharp protrusions of SUS420J2 steel specimen to polyethylene, polyvinyl-chloride, polyethylene-naphthalate sheets and a copy paper was about 1.8, 2.4, 1.1 and 1.5, respectively, at a large nominal compressive stress of 18 kPa. The reason for such large frictional coefficients is due to localized deformation of sheet under the sharp protrusions or piercing of the protrusions into the sheet. Although the sharp protrusions were partly broken, the frictional coefficients of these sheets were still about 1.6, 1.8, 1.1 and 1.4 after the second series of tests, which are more than twice as large as that of the specimen ground with #100 emery paper. The plasma-nitrided round protrusions of SUS420J2 steel and the fine protrusions of SUS316 steel were not broken during the friction tests of the polyethylene sheet and the copy paper but the frictional coefficients are smaller than those of the sharp protrusions. The protrusions with large frictional coefficients can be applied to the surface of a frictional conveying roll.
The conserved scalar and progress variable have been modified and proposed for spray and engine combustion simulation with chemical kinetics. The global equivalence ratio (GER) and progress equivalence ratio (PER) were proposed as the conserved scalar and progress variable in multi-zone model for engine simulations with chemical kinetics (Babajimopoulos et al., 2005). The combination of GER and PER work in lean mixture without EGR gas. But these would not work under rich mixture or EGR gas conditions. Thus, the modified GER is proposed to apply the EGR gas conditions where CO2 and H2O mix in air. Furthermore, the progress variable based on the chemical energy also proposed with modified GER. The zero-dimensional combustion simulations are done under constant pressure and adiabatic conditions to validate the proposed indexes. The reaction mechanism is the detailed chemistry of n-dodecane. That consists of 1,255 chemical species and 3,075 reactions. The results show that the conventional GER works in any mixture as conserved scalar and is good agreement with equivalence ratio under the ambient gas of air. But, the conventional GER overestimates equivalence ratio in lean mixture and underestimates equivalence ratio in rich mixtures. The modified GER is good agreement with equivalence ratio under the ambient gas of air and EGR gas including CO2 and H2O, regardless of lean and rich mixtures. The results also indicate that the PER works in lean mixtures. But that do not work in stoichiometric and rich mixture. The progress variable based on the mass fraction of some chemical species (Van Oijen and De Goey, 2010) works in any mixture, but the that can not compare the reaction progress between different GER conditions. The proposed progress variable works in any mixture and compares the reaction progress at different GER conditions quantitatively.
Surface modification of polystyrene (PS) dish used as a cell culture substrate is an indispensable strategy to enhance cell adhesion. In general, plasma treatment is employed to enhance the hydrophilic nature on the PS dish surface, and sterilization treatment of the PS dish is performed after the plasma treatment. We reported on a simultaneous process of surface modification and sterilization on the PS dish in a sterilization bag by using active oxygen species (AOS) generated via ultraviolet (UV) lamps, whose wavelength are 185 and 254 nm respectively. Herein, we attempt to investigate the dependency of the distance between UV lamp and PS dish on the surface modification by using the AOS. After exposure of AOS, the oxygen content of the PS dish was increased, whereas the water contact angle was decreased along with the decrement of the distance between PS dish and UV lamp owing to increase in the AOS concentration. Cell adhesion was also enhanced with decrease of the distance between PS dish and UV lamp compared with untreated PS. Especially, chemical states such as atomic concentration and chemical bonding affect cell adhesion rather than the surface wettability. Illumination of the UV lamps and AOS concentration at the PS dish surface affects the resultant cell adhesion.
A basic single-degree-of-freedom magnetic suspension system consists of one floator, one electromagnet and one amplifier. For multi-degrees-of-freedom control, multiple electromagnets and multiple amplifiers are necessary, which increases the cost of total system. As a means of overcoming this problem, parallel magnetic suspension has been proposed which controls multiple floators or multi-degree-of-freedom motions with a single power amplifier. In this system, all of the suspended points move simultaneously even when a disturbance acts on one of the suspended points solely because all electromagnet's coils are connected. This paper studies the moving direction of each suspended point with respect to a step disturbance in double parallel magnetic suspension system. The analytical study shows that the response direction is determined by the system parameter that relates the response speed of each subsystem. In the slower subsystem, the suspended point moves in the same direction as the applied force while in the faster subsystem, the suspended point moves in the opposite direction. In other words, the slower subsystem has positive stiffness while the faster system has negative stiffness. To confirm this prediction, step responses are measured in the experimental apparatus.
Stents are one of devices for the invasive cardiac catheterization (Percutaneous Transluminal Coronary Angioplasty) and especially for pediatric catheterization, the stent is manufactured by superelastic alloys including TiNi alloy. Transradial coronary intervention (TRI) is an invasive treatment in comparison with transfemoral coronary intervention (TFI), as TRI can reduce the risk of bleeding complications. To perform TRI, it is necessary to reduce the thickness of stent and diameters of delivery system. Therefore, one of the solution is to improve the strength of the materials for the stent. In this study, the medical application to stents was investigated by manufacturing high-strengthened Ni-rich powder metallurgy TiNi alloy using pure Ti powder and pure Ti pre-mixed powder. Ni-rich TiNi shape memory alloys showed much high plateau stress and enough shape recovery rate compared to the conventional ingot metallurgy TiNi alloy used in the commercial stent devices. In the simulation of the stent radial force by a finite element analysis (FEA), it was clarified that the radial forces of Ti-52.0 at.%Ni (stent wall thickness; 80 μm) and Ti-50.5 at.%Ni (stent wall thickness; 200 μm) were equivalent. The improvement of plateau stress of TiNi alloys successfully reduced the thickness of the stent by 120 μm (60 %). In fact, the stent using Ni-rich TiNi alloy resulted in the thinned stent with a high radial expansion force. When implanting the stents made of Ni-rich TiNi alloy into the external iliac artery of pigs, no stent fracture was observed, and in-stent occlusion never occurred after 1-month and 3-month placement of the stents. They are similar biocompatibility to commercial stents because of the similar results of inflammation.
Intense sound is radiated due to aeroacoustic feedback loop from a flow around the trailing edge of a curved plate with a kink shape such as a bonnet of an automobile. For the reduction of this noise, the control by a plasma actuator (PA) was investigated. The aim of this investigation is to clarify the effects of flow control by the PA on noise reduction and the noise reduction mechanism. To do this, wind tunnel experiments with a half-scale bonnet model and direct numerical simulations of flow and sound fields were performed. The investigation of the effects of the position for the installation of the PA on the control presents that the control at the position close to the flow separation point around the kink is effective for the noise reduction. Also, the control effects were compared between co-flow and counter-flow configurations regarding the direction of the mean induced flow by the actuator to the freestream. The mean velocity profiles showed that the flow separation was suppressed by the control with both configurations, while this control effect is more effective for the counter-flow configuration. The measured velocity fluctuations present that the power in broadband frequency range in the downstream of the actuator becomes larger by the control with both configurations. The predicted results show that small-scale vortices are shed near the wall around the actuator due to the large counter-flow induced flow. This introduction of the vortices and the intensification of the broadband velocity fluctuations lead to the suppression of the flow separation. Also, the development of the power of the velocity fluctuations at the fundamental frequency of the baseline tonal sound is weakened by the suppression of the flow separation. This supports the predicted results of the suppression of the two-dimensional vortices contributing to the acoustic radiation around the re-attachment point by the control. Consequently, the control can lead to the suppression of the feedback loop of the radiating mechanism of tonal sound.
Motors are used in many appliances, and noise reduction is strongly demanded. One of the main causes of noise is electromagnetic excitation force and it is well known that the excitation force is increased by the eccentricity of the rotor to the stator. For this reason, it is very important to decrease the eccentricity, but there are limits because the eccentricity is due to inevitable manufacturing tolerances or assembly errors. So, we propose a method to estimate the eccentricity of the motors in the process of manufacturing by using windings as a sensor. When the rotor and the stator are in an eccentric condition, the impedance of each winding is different. We developed an experimental apparatus that can set the amount of eccentricity and verified that the terminal voltage of each winding changes proportionally to the eccentricity. In order to produce motors with eccentricity of almost zero, we need to estimate the two-dimensional amount of eccentricity in a very short time. When the number of turns of each winding is different, there is interaction between each winding and so the accuracy of the estimation decreases. To solve these problem, we applied a different frequency of voltage to the winding located on the x axis and the winding located on the y axis, so that we can estimate the amount of eccentricity for the x direction and the y direction with high accuracy at the same time. We also developed a way to produce motors by using this technology. After detecting the terminal voltage of each winding under the tentative assembly situation, we adjust the amount of eccentricity to almost zero and fix the motor by laser welding. As a result, we were able to mass produce motors with eccentricity of under one micrometer and with a very low noise level.
It is one of the important issues to investigate the vibration behavior of railway bogies, since the vibration of the bogies may result in loosening bolts which fix the parts to the bogie frames or/and fatigue fracture of the parts themselves. A technique for predicting the vibration of bogie parts is proposed by which the acceleration power spectral densities (PSDs) at evaluated points are predicted with the use of frequency response functions (FRFs) between the axle boxes and the evaluated points, together with the use of measured accelerations of axle boxes. Stationary excitation tests are conducted to identify the FRFs, and the axle boxes or rails were hit with impulse hammers to excite the bogies. Alternatively, the new approach without the stationary tests is also proposed in this study. In this case, the FRFs are identified with the accelerations acquired in the preliminary running tests in car depots. The proposed technique is applied to the vibration prediction of the bogies for several types of railway vehicles including electric cars and a diesel car, and the differences or ratio between the predicted and actually measured PSDs are evaluated. It is confirmed that the preliminary running tests are preferable to stationary excitation tests for improving the prediction accuracy. It is also verified that the prediction error can be reduced in the case where not only the vertical but the lateral and longitudinal accelerations of axle boxes are considered as the excitation inputs under the conditions that the principal component regression is applied to identify the FRFs.
Object detection function of turnout and switch mechanism is one of an important function for safety of railway system. An object between a tongue rail and a stock rail on a turnout is detected by a lock mechanism of a switching machine and circuit controllers, which are applied on high-speed railway. Designer of switch mechanism has checks his detecting function design by experiments, which were sole way to check it, using real turnout and switch mechanism. In this paper, we described an equation of motion of the switch mechanism and the turnout using multi-body dynamics and flexible multi-body. Moreover, we described a method, which calculate shape of tongue rails inserted an object between rails. By results of calculations, we confirmed that the proposed method could simulates the shape of rails, which is affected by object. Computing time is 40% shorter than an experiment, however, the result includes an error which causes that the model was assumed deformation of tongue rails as 2-d deformation.
Research on seismic isolation technology was also a question of how much restoring force can be reduced. The seismic isolation rubber with thin film like rubber and metal plates stacked in multiple stages to reduce the restoring force has achieved great success. However, there still exists restoring power, measures against long-period earthquakes are not perfect and vertically unprotected. This research is an effort to make three-dimensional seismic isolation more realistic with higher performance by further minimizing resilience in all directions. The developed three-dimensional seismic isolation mechanism consists of an air levitation mechanism that isolates horizontal vibration and a spring link mechanism that isolates vertical vibration. Excitation experiments of the prototype were carried out using real-scale three-dimensional seismic waves by the E-defense shaking table. As a result, excellent characteristics of horizontal periodicity and vertical natural period of 5 s were confirmed. The vibration isolation performance at 1 Hz was about 20 dB in all three directions, and the high isolation performance not found in conventional equipment was verified. They were also supported by analytical models.
This research studied an influence of the inertia of the hoisting rope on the dynamics of a mobile crane system. Two dynamics models of the mobile crane were formulated with the inertia included rope model and the massless rope model, and their dynamics response were compared. The floating frame of reference formulation was used in formulating the model of the deformable components. In the simulations, we variated the length of the rope and the mass of the hoisted load then applied the slewing motion to the boom for 10 seconds and let the system underwent free vibration for another 10 seconds while the boom angle was fixed. The deformation of the rope and the comparison of the hoisted load motion between two models were considered. The results illustrated that the rope model with included inertia was able to illustrated its bending during the crane operation and this deformation increased with the length of rope. It appeared that the deformation of the boom tip had influences on the deformation of the rope. In the motion of the hoisted load, the time - history data illustrated that the inertia included rope model had slightly higher frequency than the massless rope model during the free motion, and the trajectory also showed the slightly larger sway. In addition, the total calculation time of the inertia included rope model was around 13 times longer. The difference in the motion of the hoisted load from both models increased with the length of rope but decreased when the mass of load increased. In conclusion, the model with included inertia of rope showed different response to the massless rope model at long rope and light load condition, and this difference was decreased at short rope and heavy load condition.
In this paper, deterioration diagnosis for distribution main pipe was studied using the uniform cylindrical shell approximation and in-plane bending mode. The in-plane bending mode is expected to have high accuracy in detection of deterioration, because the eigen frecuency of the mode is proportional to pipe thickness. First, using the finite element method, the characteristics of in-plane bending mode are investigated. It is confirmed that in-plane bending mode has little small dependence on the pipe length and the boundary conditions at the pipe ends, it appears in the audio frequency bands, and it has linear dependence on the pipe thickness. In addition, formula with two dimensional ring approximation is derived. Moreover, the average thickness and the uniform-cylindrical shell approximation are introduced for deal with the deteriorated pipe. Using the thinning pipe thickness of previous study, validity of the average thickness and the uniform-cylindrical shell approximation were confirmed. On the other hand, actual pipeline has the sub-structure, for example, valve, hydrant, and so on. In order to deal with the coupled vibration between the cylindrical shell and the sub-structure, eigenvalue analysis are conducted using the Semi-Analytical Receptance Method (SARM). The experimental consideration were conducted in case of that the sub-structure non-attached case. The in-plane bending mode is observed experimentally on the actual pipe system and its resonant frequency shows good match with the theoretical values.
This paper proposes an algorithm to generate the augmented reference position trajectory for the realtime 3D robotic phantom system which is used in the quality assurance of the radiation therapy. Quality assuarance is the important clinical part of the radiation therapy which ensures the delivery of the prescribed dose to the tumor of the patient. High precision quality assurance can be a difficult task if the tumor exhibits respiratory induced motion inside the body of the patient, as the motion fluctuates along with time and it suffers large inter-patient difference. This paper presents several algorithms to modify and/or correct the reference tumor trajectory of the patient and generate the augmented reference trajectory sequence for the already existing and tuned control system of the robot manipulator to yield high precision tracking to the original tumor motion trajectory. Experimental validation has been carried out for four lung tumor trajectories in the clinical environment using equipments used in the radiotherapy treatment and it has been shown that the clinical demand on the precision of tumor motion tracking has been satisfied for all the four cases.
In this paper, we propose a novel two-stage approach on picking an object from randomly stacked pile. We especially consider a situation where it is difficult for a 3D depth sensor to identify the pose of objects such as shinny ones and black ones. For such objects, our method first roughly grasps some of the objects from the pile without using the visual information and roughly place them onto a working table. After some of the objects are placed on a working table, a robot picks one of them by detecting the 2D position of objects placed on a working table by using the 2D RGB image. We performed experiments for several objects with different shape and weight. Through experimental study, we confirmed that a robot can identify the position of one of the objects after the objects are placed on a working table and that one of the objects can be successfully picked up by a robot.
Reduction of particulate matter (PM) in exhaust gas from automobile engines is in high demand. Fuel stuck on the engine wall causes incomplete combustion, and generates a large amount of PM. To prevent this, shape of fuel injection spray must be controlled with precision. We focused on the valve offset of the injector as a factor influencing the spray shape. Computational analysis was conducted to investigate the effects of the valve offset on inner nozzle flow and spray shape (spray direction and liquid penetration). Simulated spray behavior image, footprint, and liquid penetration agreed well with experimental results. From the inner nozzle flow simulation results with the valve offset, it was found that fuel tends to flow in the direction of the valve offset near a sac in the nozzle to provide the fuel to the holes. This flow was caused by the smaller flow path fomed in the valve offset direction. From the spray simulation results, shifts in the spray direction of the plumes were caused by the flows near the sac. Some plumes were injected in the direction opposite to the valve offset. The holes with larger drill angle located in the valve offset direction, and larger valve offset caused larger changes of spray directions. Furthermore, liquid penetration was investigated. We showed that the flow separation in the holes caused by the valve offset affects the velocity distribution at the hole outlet and results in changes of the penetration length when the drill angle is small. It was found that the valve offset causes the change in the inner nozzle flow, and results in the change of the spray shape. We concluded that the correlation of nozzle geometry and valve offset is important for controlling the spray shape.
In disaster areas, rescue work by humans is extremely difficult and dangerous. Therefore, rescue work using rescue robots in place of humans is attracting attention. This study specifically examines peristaltic crawling, the movement technique used by earthworms, because it can enable movement through narrow spaces and because it can provide stable movement even in various difficult environments. Moreover, we designed each part of the robot based on required specifications and developed a real robot. We present results of motion experiments conducted with robot movement on level ground.
Hydrogen combustion is attracting attentions because of zero CO2 emission. Recently, a gas turbine which uses hydrogen-rich fuel is being developed. In our previous study, we examined the influence of hydrogen-containing ratio on combustion oscillation for fuel mixtures of hydrogen and town gas (13A) experimentally. In the experiment, pressure oscillations were measured by a sensor which is installed at the bottom of the combustor. It is found that two oscillation frequencies near 200 Hz and 400 Hz were simultaneously detected in the case of hydrogen-containing fuels, whereas single oscillation frequency around 350 Hz was observed in the case of only 13A fuel. To understand this difference of oscillating frequencies, we conducted acoustic analysis using one-dimensional different diameter acoustic model. However, this simplest model could not reproduce three types of oscillating frequencies obtained by the experiment. Besides, we used an acoustic impedance of the bottom of the combustion chamber as an acoustic boundary condition. The acoustic impedance is measured experimentally under the noncombustion (cold) condition and corrected by combustion temperature obtained by equilibrium calculation. As a result of applying the corrected acoustic impedance, the three types of oscillating frequencies could be reproduced by acoustic analysis. Furthermore, to express the difference among fuel mixtures, delay times, flame positions, and the mean temperature in the chamber were calculated by the CFD simulation. Consequently, it is found that the acoustic analysis result could reproduced the difference among fuel mixtures; hydrogen makes the oscillating frequencies a little higher, because temperature becomes higher and delay time becomes shorter.
Inverted pendulum vehicles controlled by movement of driver's center of gravity (COG), such as Winglet or Segway are the examples of Personal Mobility Vehicles (PMV). PMV is sometimes expected to be used in pedestrian spaces. When a driver brakes an inverted pendulum vehicle suddenly, the driver has to move his/her COG backward largely and has the risk to lose his/her balance due to the characteristics of vehicle control. Therefore, we aim to achieve a vehicle control system that is friendly to drivers in emergency. In the previous study, the coupling model of a vehicle and a human had been built on Multibody Dynamics and the technique to brake an inverted pendulum vehicle automatically had been proposed using that model. In this study, we carried out two experiments to decide the timing of the automatic braking system defined as Time To Collision (TTC). We carried out two experiments about stopping distance when a driver brakes an inverted pendulum vehicle suddenly and when the automatic braking system is operated, and we compared those results. Then, it was shown that stopping distance operated by the automatic braking system is shorter than by human driver's sudden braking operations. In addition, we derived TTC1 ( 0.7 s ) of inverted pendulum vehicles from these experiments about stopping distance by human drivers' sudden braking. Then, we derived reaction time ( 0.4 s ). Finally, we proposed a safety system using TTC1 and the reaction time. When TTC reaches 1.1[s], the alarm makes a human brake an inverted pendulum vehicle suddenly. Then if a human doesn't brake an inverted pendulum vehicle suddenly and TTC reaches 0.7[s], the automatic braking is operated.
The high productivity of gear skiving has caused the process to attract a lot of attention in recent years and taper shaped skiving cutters are generally used in current gear skiving. A cutter axis in gear skiving is inclined to a gear axis and a taper shaped skiving cutter could cause tooth profile deviations of skived gears after re-sharpening of tool faces. Adjusting cutter position and/or re-profiling of cutter flanks are applied to enable tooth profile deviations of skived gears to remain within acceptable ranges when the adjustment is necessary. Adjusting cutter position is preferred to re-profiling of cutter flanks due to desire for low production cost. However, the universality of the current methods of calculating cutter positions is still not confirmed. The present study explains that the current methods for obtaining cutter positions could require individual calculating formulas according to cutter specifications for each particular gear. A universal method which avoids such complexity of making various formulas could contribute to permit gear skiving to become more useful in the gear machining field. Then such a desirable method is proposed and the reasonability of the method is confirmed by experiments. In addition, this study discusses the existence of scope in which the method can be applied and a method for checking collisions between cutter flanks and gear tooth flanks being cut after adjustment of cutter position.
The wear acceleration mechanism of a DLC film lubricated with MoDTC solution was investigated by using in-situ and ex-situ analytical techniques: Raman spectroscopy, SEM-EDS, ToF-SIMS, and nano-indenter. From the results, the structural change of the DLC film strongly related to the formation of Mo-carbide containing tribofilms, which were much harder than DLC used in this study. Therefore, the MoDTC-induced wear acceleration of the DLC film is caused by hard Mo-carbide containing tribofilms on a counter-face steel surface.
Dynamic behavior of binary water droplets approaching each other in cloud is simulated by the improved two-phase lattice Boltzmann method with the Continuum Surface Force (CSF) model. This method does not need to solve the pressure Poisson equation and enables us to calculate two-phase flows with high density ratio accurately and efficiently. In this study, we investigate the effects of the Reynolds number Re, the Weber number We, the impact parameter B (the relative distance between the centers of two droplets), and the droplet size ratio on the behavior of the binary droplets for liquid-gas density ratio of 800. We first simulate a stationary liquid droplet in a gas to confirm the validity of the present method. We next simulate off-center approach of two equal-size droplets and investigate the effects of the Reynolds number and the Weber number. It is seen that at low Weber numbers of We ～ O(10-2), there are two types of behavior during approach of two equal-size droplets, namely coalescence and deviation. In this Weber number region, it is found that they can deviate from each other at low Reynolds numbers of Re ≲ O(1) in spite of B ≤ 1.0, whereas collision and subsequent coalescence occur at higher Reynolds numbers of Re ≳ O(10). We finally simulate approach of two unequalsize droplets with various size ratios. It is found that the behavior of the droplets is different from that in the case of the equal-size droplets owing to asymmetric velocity field and droplet deformation. In addition, the smaller droplet tends to deviate from its original path more significantly than the larger droplet.
In design of rotating machines, analysis of external force is important for stable rotating operation. The various external forces such as unbalance force, seal contact force and rotor dynamic fluid force effect on the rotor system, dynamic characteristics of rotating system is changed by the external forces. The external force can vary depending on a rotor trajectory. In previous studies, a mathematical model of the dynamic characteristics had been formulated for small amplitude orbit around the equilibrium point for the rotor trajectory. However, the formulation hasn't been yet established in the rotor trajectory with large amplitude or eccentricity caused by the external forces. In this study, an experimental system using active magnetic bearing (AMB) is developed to achieve the formulation. The system can generate any arbitrary trajectory assuming various external forces and the rotor system follow the generated trajectory. The system can estimate the external force at the same time. Current flowing through coil of the AMB is controlled by a controller designed based on the frequency response to follow the arbitrary orbit. Then, the external forces are estimated from the control signal by the disturbance observer. Experiments were performed by assuming unbalance forces generated in the elastic rotor. From the results it was confirmed experimentally that high precision tracking control and estimation of external force are possible. The various rotor trajectory under the action of the external forces can be repeated by using the system, and the external force can be analyzed by the experimental data.
Hydraulic breakers, which are used to demolish concrete structures or rocks etc., make a loud noise. It is considered that one of the major noise sources of the breaker is the longitudinal vibration resonance of the breaker's chisel. Hence, in order to suppress the noise, a chisel in which a dynamic damper is integrated is proposed in this paper. The proposed dynamic damper consists of ring-shaped weight and ring-shaped plastic spacers. To install it on the chisel, a portion of the chisel must be made slender because the diameter of the chisel is limited by size of the chisel holder of the breaker. Because of this structure, the resonance frequencies of longitudinal vibration modes of the chisel are changed with parameters of the dynamic damper, such as the sizes and the position, etc. Therefore, it is difficult to design the dynamic damper with conventional ways. First, vibration response of the proposed chisel is derived with the transfer matrix method theoretically. Second, experimental results of the frequency response are shown and confirm the validity of the theoretical model. Then, effects of the parameters of the dynamic damper are investigated with the model. Finally, the experimental results of the impact noise during demolishing work are shown. These results show that the proposed chisel is valid and feasible for reducing the noise from hydraulic breakers.
This paper presents a dynamic simulation technique for the rigid body system coupled with the hydraulic system considering the digging behavior of the soil. The rigid body system and hydraulic system is modeled based on the Newton-Euler formulation, while the soil is modeled by the discrete element method (DEM) using the cohesive model proposed by Utili and Nova(2008). The co-simulation is carried out for the rigid body/hydraulic coupling system and the soil. Firstly, the digging simulation of the soil for the bucket of the hydraulic excavator is carried out for the cohesive soil and the sandy soil. The digging behavior of the soil and the digging force are discussed. Secondly, the co-simulation technique for the rigid body/hydraulic coupling system and the soil is presented. Finally, the dynamic simulation of the hydraulic excavator is carried out for the digging operation, the behavior of the hydraulic system and the soil is discussed for the cohesive soil and the sandy soil. It is shown that the digging power of the arm driving system for the sandy soil can be reduced by considering the cohesive force. It is clarified that the present technique can evaluate the hydraulic system of the hydraulic excavator for any characteristics of the soil.
As a method for mining offshore gas fields, a floating production, storage and offloading (FPSO) system is attracting attention. However, sloshing in the oil-gas separator installed in FPSOs excited by sea waves is expected to cause significant difficulties. To suppress sloshing wave heights, one possibility may be to install perforated plates in a tank. In this study, a method is proposed for the accurate estimation of the first resonant wave height in the horizontal cylindrical tank with a perforated plate under pitching excitation in less time. To accomplish this purpose, the pressure loss due to the perforated plate in the open channel must be estimated accurately. Therefore, the pressure loss is modeled using steady CFD calculations considering the effects of the distribution of the flow velocity and the distribution of the inflow angle. The first order sloshing wave height is calculated in the theoretical analysis by substituting the pressure loss calculated in steady CFD. The wave heights determined using the pressure loss utilized by steady CFD are compared with the experimental value measured with a small-scale model. Using the method proposed in this study, the first resonant wave height of sloshing wave height is calculated accurately in less time.
This paper considers the implementation of a cascade type PIS compensator for the pneumatic anti-vibration apparatuses (AVA) control system. In precedence research the parallel type PIS compensator was used. This is composed of a PI and S compensators connected in parallel. However a PIS compensator is interpreted as a special case of what is used in repetitive control. In this case, a cascade connected compensators is used. According to this, the PIS compensator should be in series type. Also, parallel type PIS compensator generates swing of the output signal. Through above problems, cascade type PIS compensator is considered. However, the AVA control system with the compensator causes collision and steady-state deviation. In order to resolve these problems, we improve the structure of the compensator and its switching method. This experimental result shows that the normal operation of the AVA control system with cascade type PIS compensator. From the above, we show that the implementation of cascade type PIS compensator for the AVA control system.
Although, in designing blades, it is assumed that all blades on a disk are identical (tuned system), the vibration characteristics of the blade is slightly different due to the manufacturing tolerance, the deviation of the material property, and so on (mistuned system). As a result, in the forced response of an actual bladed disk caused by the flow distortion, the responses of all the blades on a disk become different, and the response of a certain blade may become extremely large, due to the split of the duplicated natural frequencies, the distortion of the vibration modes, and so on. On the other hand, it is suggested by many researchers that the mistuning suppresses the blade flutter, because the complete travelling wave mode is not formed in a disk. In other words, the effect of the mistuning acts on the dangerous side for the forced vibration, while on the safety side for the blade flutter. In this study, the stability analysis and the frequency response analysis of mistuned bladed disks are carried out using the reduced model with high fidelity, in order to research the vibration characteristics of typical mistuned bladed disks. Based on the analysis results, an optimal design procedure of mistuned bladed disks considering both the forced response and the self-excited vibration is proposed.
The traction drive - integrated drive generator (T-IDG®) has been developed since 1999 to replace current hydrostatic transmission drive generators. The T-IDG® consists of a generator and a half-toroidal traction-drive continuously variable transmission (CVT), which maintains a constant output speed of 24,000 rpm. In terms of coping with recent trends of high-power electric drive aircraft (MEA) and the need for weight reduction, a high-speed traction-drive CVT is advantageous over current hydro-static drive transmissions. To control a speed ratio of the high-speed CVT accurately, it is essential to know the speed-changing response. In conventional study, the speed-changing response is approximately proportional to a rotational speed; however, in the high speed CVT, a minute deformation during the speed change affects its response. This paper describes the analysis and a developed theory of the speed-changing response of a toroidal CVT, with showing test results which verify the response of the high speed CVT, whose input speed is 20,000 rpm at maximum with a peripheral speed of traction contact of 70 m/s.