Showing papers in "Transactions of the Japan Society of Mechanical Engineers. C in 2013"
17 citations
TL;DR: In this article, an anti-vibration tribometer (AVT) was developed to measure true values of kinetic friction coefficient in a force balance between the frictional force and spring force, which utilizes a novel principle that an angular misalignment between the two velocities produces a positive damping effect to stabilize the equilibrium point and suppress frictional vibration autonomously.
Abstract: To measure true values of kinetic friction coefficient in a force balance between the frictional force and spring force, an anti-vibration tribometer (AVT) has been developed. The AVT utilizes a novel principle that an angular misalignment between the two velocities (i.e., the driving velocity of one of contact surfaces and the moving velocity of the other surface) produces a positive damping effect to stabilize the equilibrium point and suppress frictional vibration autonomously. For example, when a sliding contact between a steel ball and a steel plate is lubricated by glycerin, the AVT provides a force balance situation at a misalignment angle φ = 30° (i.e., an anti-vibration setting), although strong frictional vibration occurs at φ = 0° (i.e., a conventional setting). By comparing the kinetic friction coefficients obtained at φ = 0° and 30°, it has been found that frictional vibration can lead to a serious error of measuring kinetic friction coefficient (e.g., a 35% underestimation at a low driving speed).
15 citations
13 citations
12 citations
TL;DR: An efficient expression of 3D map by considering of LIDAR intensity is proposed, which shows successful localization in a trail through outdoor open grass fields.
Abstract: ©2013 The Japan Society of Mechanical Engineers This paper presents the technique for improving the accuracy and reliability of an autonomous mobile robot localization. Localization based on 2D LIDAR is not always satisfactory due to occlusion. Use of 3D LIDAR improves the reliability by greater field of view. However, lack of 3D objects around the robot may result in poor matching between the observation and the 3D map. Even in this case, the different brightness of the ground surface helps localization. In this paper, we propose an efficient expression of 3D map by considering of LIDAR intensity. Experiment result shows successful localization in a trail through outdoor open grass fields.
11 citations
TL;DR: A method to predict pedestrian movement for collision avoidance of mobile robots and pedestrians is proposed and a database of human movement tendencies is generated and applied to the prediction of future pedestrian movement.
Abstract: In order for mobile robots to coexist with humans, both safety and efficiency should be satisfied. We propose a method to predict pedestrian movement for collision avoidance of mobile robots and pedestrians. In the proposed method, the pedestrian trajectories are measured and a database of human movement tendencies is generated. The database is applied to the prediction of future pedestrian movement. To decrease the initial time cost for database generation, environmental geometric configuration is considered in the form of virtual forces. To verify the usefulness of the proposed method, we generated the database based on five-hour observation and conducted three types of experiments based on the generated database. The first experiment showed the prediction performance of the proposed method and proved the method guaranteed the safety. The second experiment showed that the proposed method satisfied both the safety and efficiency through the comparative simulations. The third experiment showed the method could apply to the real mobile robot.
10 citations
TL;DR: This paper investigates the formulation of the relationship between energy consumption and production throughput taking into account breakdown states, and investigates the relation between lot size and energy consumption per production throughput.
Abstract: 1 Abstract Industries have been becoming more important to evaluate and reduce energy consumption when designing, operating, and improving manufacturing systems. In our past research, manufacturing system simulation to evaluate productivity and energy consumption concurrently has been proposed and developed for designing, operating, and improving the manufacturing systems. We also proposed a formulation for relationships between lot size and energy consumption per unit of production throughput. However, on our proposed formation, we did not consider the breakdown states in each facilities. In this paper, we propose a formulation concerning relationships between lot size and energy consumption per unit of production throughput considering breakdown states. This proposed formulation is an approach for the theoretical realization of the production conditions that affect a productivity or energy consumption. We investigate the formulation of the relationship between energy consumption and production throughput taking into account breakdown states, and verify it by using our developed simulation. Concerning the investigation, a middle-scale semiconductor manufacturing line which consist of three facilities, a solder printing facility, an IC mounting facility, and a solder reflow facility is simulated. Through the investigation, the relation between lot size and energy consumption per production throughput, production throughput are being understood.
10 citations
TL;DR: In this article, the influence of the grinding atmosphere on the ground surface characteristics of unidirectional carbon fiber reinforced plastic (CFRP) was investigated by using a vitrified bond diamond wheel with the water soluble coolant and the liquid nitrogen.
Abstract: CFRP (Carbon Fiber Reinforced Plastics), which is increasingly applied to airplanes, automobiles, production equipment for electronic device, and so on, is machined after molding process. Grinding is often used for edge finishing of CFRP parts. This paper deals with the influence of grinding atmosphere on grinding characteristics of CFRP by the experimental investigation of ground surface characteristics, surface finish, grinding force, grinding temperature, etc. in surface grinding of unidirectional CFRP using a vitrified bond diamond wheel with the water soluble coolant and the liquid nitrogen in addition to dry grinding. The grinding temperature has been measured by a developed thermocouple system using carbon fibers being made up CFRP and a constantan wire setting between CFRP specimens. The grinding temperature at wheel contact area on CFRP is higher than the glass-transition temperature of CFRP at larger setting wheel depth of cut. The wet grinding prevents in worsening ground surface of CFRP and increasing grinding force that occur in dry grinding of CFRP. The liquid nitrogen makes some effect on prevention in wheel loading and delamination of carbon fibers in dry grinding of CFRP, however the grinding force supplying liquid nitrogen becomes larger than that in dry grinding because of an increase in hardness of CFRP by freeze up. The bending strength of ground CFRP, which suggests the scale of affected layer, is improved by supplying the water soluble coolant and the liquid nitrogen in grinding process.
9 citations
TL;DR: In this paper, the effects of the diameter (dg) and the velocity (vg) of a hydroxyapatite particle on PJD process to human enamel were investigated by using a smoothed particle hydrodynamics (SPH) method.
Abstract: Powder jet deposition (PJD) is a coating process using accelerated particles. In this process, accelerated ceramic particles are impacted on a substrate, and fractured particles partly adhere to it. We have proposed to apply this process to dental treatment. In this study, the effects of the diameter (dg) and the velocity (vg) of a hydroxyapatite particle on PJD process to human enamel were investigated by using a smoothed particle hydrodynamics (SPH) method. Optimized conditions were clarified through the SPH simulations, and PJD experiments were conducted under the obtained conditions. It was found that the surface of the enamel substrate was partly removed when the mean particle diameter dg = 4.65 μm and the mean particle velocity vg = 250 m/s, and coated layers were formed on the human enamel substrates when dg = 4.65 μm and vg = 200 m/s, or dg = 3.18 μm and vg = 200, 250 m/s.
8 citations
7 citations
TL;DR: In this paper, the response distribution of an asymmetric nonlinear stiffness system to non-Gaussian random excitation is investigated, and the effect of the asymmetry of the system appears clearly in the response distributions.
Abstract: ©2013 The Japan Society of Mechanical Engineers Response distribution of an asymmetric nonlinear stiffness system to non-Gaussian random excitation is investigated. The excitation is a stationary stochastic process characterized by the non-Gaussian probability density and the power spectrum with a wide range of bandwidth. Both bimodal and Laplace distributions are considered as the non-Gaussianity of the excitation. A non-Gaussian stochastic process is generated by calculating an Ito stochastic differential equation in which the drift and diffusion coefficients are determined according to the given probability density and spectral density of the process. Monte Carlo simulations are carried out to obtain the stationary response distributions of linear system, Duffing system, and asymmetric stiffness system subjected to the non-Gaussian excitation. It is shown that the response distribution varies markedly depending on the bandwidth and non-Gaussianity of the excitation, and furthermore, the effect of the asymmetry of the system appears clearly in the response distribution.
TL;DR: The features of the scheme are that the user can easily instruct the robot how to perform the object picking task by simple clicking operation, and the robot can pick up the indicated object placed in a complex environment without any previous knowledge of the target object.
Abstract: ©2013 The Japan Society of Mechanical Engineers This paper presents a task instruction system for picking up an indicated object in a complex environment. The basic setup of the system consists of a manipulator, a stereo camera, and a monitor. The task instruction scheme comprises the following four main steps: 1) The user indicates the target object on the camera image by a mouse click, and selects the object category and grasping form from a pop-up list. In this way, the system obtains information about the 3D position coordinates of the clicked point on the target object, the primitive shape of the object, and the task model for object picking with the selected grasping form. 2) The system acquires the information about the target object and constructs an environment model around the target by stereo vision using the information obtained from the task instruction. 3) The system finds a grasp point based on a grasp evaluation using the acquired information. 4) The robot performs picking up the indicated object. The features of the scheme are that the user can easily instruct the robot how to perform the object picking task by simple clicking operation, and the robot can pick up the indicated object placed in a complex environment without any previous knowledge of the target object.
TL;DR: In this paper, the authors verified the hunting characteristics of a new-type independently rotating wheelset (IRW) with negative tread conicity and showed that the hunting stability can be improved with longitudinal stiffness.
Abstract: In this study, the hunting characteristics of a new-type independently rotating wheelset(IRW) with negative tread conicity is verified experimentally. In order to improve curving performance of low-floor light rail vehicles(LRVs), the new-type IRW has been proposed. In previous study conducted by Prof. Suda et al., it has been demonstrated with numerical simulation that unstable hunting motion whose frequency decreases as the running velocity increases occurs in the new-type IRW. In addition, it has been proved that the hunting stability of the new-type IRW can be improved with longitudinal stiffness. In this investigation, experimental equipment with scaled-model roller rig is developed to clarify those characteristics of the new-type IRW. It is demonstrated that the new-type IRW used in experimental vehicle has same hunting characteristics of the simulation model. Furthermore, improvement of hunting stability of the new-type IRW with longitudinal stiffness is proven.
TL;DR: In this article, an algebraic solution to a similar minimax optimization problem of minimizing the maximum value of the tire workload where the direct yaw moment is explicitly specified is derived.
Abstract: The direct yaw-moment control (DYC) poses an optimization problem of determining the traction/braking forces distribution that is to be solved online to minimize the risk of tire force saturation to avoid instable vehicle behaviors. One of the authors has derived an algebraic solution to a similar minimax optimization problem of minimizing the maximum value of the tire workload where the direct yaw moment is explicitly specified. In this study, this algebraic solution is applied to the solution procedure for the extended minimax optimization problem where the total value of the traction/braking forces, that of the lateral force by the steering of the front and rear wheels, that of the yaw moment by the direct yaw moment and by the lateral forces of the front and rear wheels are specified. The proposed numerical approach that uses the golden section method rapidly converges to the exact solution of the essential decision variables as the traction/braking forces of the four wheels. The effects of problem relaxation are demonstrated through numerical examples.
TL;DR: In this article, the results of the laboratory experiments carried out in relation to tangential force coefficient between contacting two cylindrical test specimens under different surface conditions, and the numerical analysis results of hunting stability of railway vehicle with the fine unevenness on wheel tread.
Abstract: It is generally known that tangential force characteristics of wheel/ rail have a great influence on the vehicle dynamics characteristic. However, according to one author’s previous researches, it is difficult to estimate tangential force characteristics of actual-wheel/rail interface correctly, because the shape of contact patch of actual-wheel/ rail may not be a complete ellipse shape due to existence of fine unevenness on wheel tread. This paper presents the results of the laboratory experiments carried out in relation to tangential force coefficient between contacting two cylindrical test specimens under different surface conditions, and the numerical analysis results of hunting stability of railway vehicle with the fine unevenness on wheel tread. In the laboratory experiments, the tangential force coefficient of specimens with/without a variety of fine unevenness under different attack-angles has been obtained by means of a two-disk rolling contact machine. The experimental results showed, in the case of attack-angle is zero, the longitudinal tangential force coefficient becomes smaller when the fine unevenness is larger than the case without fine unevenness. On the other hand, in the case of the attack-angle is about 0.2deg, the lateral tangential force coefficient is small when the interval of the fine unevenness is large. Furthermore, a numerical analysis was carried out to estimate the relationship between a variety of fine unevenness and the hunting stability of railway vehicles. As a result of this study, it is clarified that the fine unevenness on wheel tread has an improvement effect on the hunting stability of railway vehicle.
TL;DR: In this article, the authors constructed a model for predicting the worn profile of rail incorporated in SIMPACK and carried out the analysis under the several conditions, and examined about the influential factor of wear of rail.
Abstract: Rail wear is one of the phenomena caused by rolling contact of rail and wheel. Situation of rail wear changes with complexity because the contact of rail and wheel changes gradually according to the running condition of vehicles and track geometry condition. Therefore, it is important to predict the wear profile of rail continuously. However, predicting the change of rail profile due to wear has been mostly examined based on one contact condition of rail and wheel. SIMPACK, which is one of the Multi-Body Dynamics (MBD) software is very useful to analyze vehicle dynamics, contact conditions of rail and wheel and so on. In this research, the authors constructed a model for predicting of worn profile of rail incorporated in SIMPACK and carried out the analysis under the several conditions. Furthermore, we examined about the influential factor of wear of rail.
TL;DR: In order to realize a premixed compression ignition (PCI) engine by utilizing bio-alcohol, combustion characteristics of bioalcohol blended with gas oil were compared between ethanol and n-butanol in a diesel engine as mentioned in this paper, and the effects of the ethanol blend ratio and the butanol blend ratio on ignition delay, premixed combustion, diffusion combustion, fuel consumption and exhaust emissions such as smoke density, nitrogen oxide (NOx) and so on were investigated experimentally.
Abstract: In order to realize a premixed compression ignition (PCI) engine by utilizing bio-alcohol, combustion characteristics of bio-alcohol blended with gas oil were compared between ethanol and n-butanol in a diesel engine. The effects of the ethanol blend ratio and the butanol blend ratio on ignition delay, premixed combustion, diffusion combustion, fuel consumption and exhaust emissions such as smoke density, nitrogen oxide (NOx) and so on were investigated experimentally. It is found that ethanol almost burns out together with low evaporation temperature composition of gas oil in the premixed combustion period and the heat release in the diffusion combustion is based on mainly high evaporation temperature composition of gas oil, then, soot is formed in the diffusion combustion of gas oil. On the other hand, a part of butanol burns in the diffusion combustion, and the combustion of butanol in the diffusion stage is not the cause of soot formation. Butanol is more useful in diesel engine compared with ethanol because butanol can be blended with gas oil without surface-active agent, and fuel consumption and smoke are almost equal in both blend fuels if the alcohol blend ratio is the same.
TL;DR: In this paper, the tensile strength of the solid structure fabricated by a direct metal lamination under various lamination conditions is examined and the suitable conditions to realize a solid structure without weld defects are clarified.
Abstract: The tensile strength of the solid structure fabricated by a direct metal lamination under various lamination conditions is examined. The direct metal lamination is a kind of the additive manufacturing process using the arc welding technology; where the molten metal made by the arc discharge is accumulated successively in this process. Combinations of lamination conditions such as welding current, torch feed speed and the cross feed of the torch are explored and the suitable conditions to realize a solid structure without weld defects are clarified. Then it is shown that the laminated modeling object has enough tensile strength compared with the same bulk material. In addition, the welding torch moving direction doesn’t affect the strength of the object because the accumulated overlapping beads melt into each other under the suitable condition.
TL;DR: In this article, a method of detecting and estimating the pose of coil springs using highlights made by illumination with stereo vision was proposed, which was used in a bin-picking system with an industrial robot.
Abstract: ©2013 The Japan Society of Mechanical Engineers It is difficult to recognize each of coil springs randomly placed in a pile by conventional machine vision techniques because of their shape characteristics such as a succession of identical shapes and a complicated outline. In this paper, we propose a method of recognition and pose estimation of coil springs using their highlights made by illumination with stereo vision. In this method, we extract and discriminate their highlights. They are grouped into highlight groups in left and right images so that a highlight group includes highlights that belong to a coil spring. Then, we find correspondence between left and right highlight groups to estimate the pose of coil springs by stereo vision. We implemented this method as a bin-picking system with an industrial robot. Bin-picking of coil springs was almost successful on the system. A main reason for picking failure was collisions between the fingers of the hand and the part box, and those between the fingers and other coil springs. Therefore, implementation of collision avoidance would make bin-picking more reliable.
TL;DR: In this paper, the damping effect due to passengers was examined by using actual railway vehicles and compared the measurement results to the cases that iron blocks or water tanks are loaded. But, the authors did not consider the effect of passengers boarding on a railway vehicle.
Abstract: ©2013 The Japan Society of Mechanical Engineers Passengers boarding on a railway vehicle are usually treated as additional mass in designing carbody and the natural frequencies of carbody flexural vibrations are considered to decrease as the number of passenger increases. However, some previous studies indicate that on-board passengers behave not as additional mass but as damping. This paper examines the damping effect due to passengers by using actual railway vehicles and compares the measurement results to the cases that iron blocks or water tanks are loaded. A stationary excitation test in the rolling stock testing plant for a commuter-type vehicle and a running test on a commercial line for a Shinkansen-train were conducted. From both tests, relatively large vibration reduction effects upon different natural modes of flexural vibration of the carbodies and little change of their natural frequencies were observed when passengers were aboard. On the other hand, natural frequencies were decreased when iron blocks or water tanks were loaded. The authors also tried to develop a numerical model to express the flexural vibration of carbody with passengers. It was found that a simple 1-DOF mass-spring-damper system with low natural frequency and high damping ratio can simulate a passenger well. According to those measurement results, it is expected that a new and valuable damping device against carbody flexural vibrations can be realized if we can simulate or mimic the effect of passengers correctly. Some basic directions or policies to develop such damping devices were discussed.
TL;DR: In this article, an impulsive force sensor which can be attached to a column part of the baseball bat is presented. But, the performance of the sensor is investigated by the pipe punch test and the ball drop test, and the impulsive forces are measured by the test that a batter hits the ball which the pitcher threw.
Abstract: Impulsive force acting when the ball is hit with a baseball bat is interesting from the field of sports engineering. This study intends to develop an impulsive force sensor which can be attached to a column part of the baseball bat. The pipe surface sensor is a pressure sensor suitable for the measurement of high speed impulsive force. The pipe surface sensor consists of a thin pad sensor, a cover-plate and metal adhesive tape. The metal adhesive tape plays a role to wrap the sensor and cover-plate and fix these together to the bat tightly. First, a friction removal mechanism in contact interface, a bendable sensor configuration and a method of sensor installation on the surface of the pipe are discussed. Then, prototype sensors that can be installed on a pipe with diameter of about 70mm are made. The performance of sensor is investigated by the pipe punch test and the ball drop test. Then, the impulsive force is measured by the test that a batter hits the ball which the pitcher threw. A metal bat and a hard ball are used for the experiment of hit and bunt.
TL;DR: In this paper, the authors proposed a statistical energy analysis (SEA) method for high frequency noise prediction considering the number of modes at the frequency of interest, where the turbulence generated spartial distributed fluctuated surface pressure computed by Computational Fluid Dynamics (CFD) is decomposed to the wavenumber-frequency spectrum for describing the wave component in detail.
Abstract: The wind noise typically covers broad band frequency range, for example, from 100Hz to 5kHz in the case of automobile. For the high frequency noise prediction, Statistical Energy Analysis (SEA) is the most suitable method considering the number of modes at the frequency of interest. In SEA development progress, the excitation model for Turbulent Boundary Layer (TBL) has been developed based on the Corcos type models. In low mach number flow, however, due to the difficulty in describing the wavenumber component distribution of the fluctuated surface pressure caused by turbulence using the TBL excitation model, especially in describing the acoustic wavenumber component which is sensitive to transmission to passenger compartment, SEA has not been applied to the analysis of the wind noise of automobile. In this paper, the turbulence generated spartial distributed fluctuated surface pressure computed by Computational Fluid Dynamics (CFD) is decomposed to the wavenumber-frequency spectrum for describing the wavenumber component in detail. The SEA modeling for predicting the wind nosie using the wavenumber-frequency spectrum is proposed considering the main path to the interior cavity. Then, the validation of the proposed method is done by comparing with the measurement and shows good agreement.
TL;DR: This paper proposes a new method that uses multiple SOMs for estimating values lacking in data analysis and shows the advantages of the method over some traditional techniques including a technique that uses single SOM.
Abstract: In this paper, we propose a new method that uses multiple SOMs for estimating values lacking in data analysis. Recently, development of information technology grows the importance of data analysis. In actual data, however, some values will be sometimes missing, and then dealing with such insufficient data has become one of the important subjects in data analysis. Estimating and completing the empty values are required to applying various data analysis techniques. Such an estimation method is also applicable to data prediction problems. In the former methods that use SOM, many empty values would have caused the lack of data for learning process. Our system can achieve effective learning by using multiple SOMs even for data that includes many missing values. Moreover, the system is still available for nonlinear data because of using SOMs. We performed some numerical simulation using the proposed and other methods. By the simulation results, we showed the advantages of our method over some traditional techniques including a technique that uses single SOM.