A bicycle wheel consists of a hub, spokes, nipples and a rim. The rim deforms from true circle to irregular circle when a worker assembles the wheel. People can ride a bicycle in safety when the rim is the true circle. The worker needs to correct the deformed rim. The worker can correct the deformed rim through the use of a relation between a nipple position to rotate a nipple rotation angle and rim displacements. I developed a task support equipment to correct the deformed rim through the use of the relation. The worker does not need to know the relation through the use of the developed task support equipment. The worker can correct the deformed rim through the use of the developed task support equipment. The developed task support equipment shows the worker the nipple position to rotate the nipple rotation angle. The worker rotates the nipple as shown by the developed task support equipment. I measured the relation between the nipple rotation angle and the rim displacements. I suggested a method to calculate the corrected rim displacements through the use of the relation. I made up a hardware and a software in the task support equipment. I implemented the method in the software. I checked performance of the developed task support equipment. I corrected the deformed rim through the use of the developed task support equipment. The results have shown the usefulness in the developed task support equipment for correcting the deformed rim.
This paper describes a novel mechanism with passive crawlers that will realize a stair-climbing rescue robot with simple system. The proposed mechanism is called “SMART-III”, it is named after “Simple Mechanism Adaptive for Rough Terrain”. Some quasi-static dynamic analysis were implemented and effectiveness of limitation for crawler rotation angle were verified. A prototype robot with the SMART-III mechanism had been improved. Experimental results show the effectiveness and performance of the proposed mechanism against a step and continuous stairs.
In this paper, a high-speed three-dimensional map generation method using direct estimation of the motion parameters of the sensor is proposed. The method aligns range images between frames after estimating the motion parameters of the sensor using two kinds of information. One is the relationship of the range images and the motion parameters of a small motion. The other is the relationship of the intensity gradient information of the color images and the motion parameters. The method can create three-dimensional maps quickly because the method does not need to obtain the correspondences of features. Both the processing time required for the motion parameter estimation and the accuracy of the map are verified by experiments using a developed fast RGB-D sensor. It is also shown that the method is applicable to the Kinect sensor.
In this paper, we propose a target-tracking system for a mobile robot equipped with a stereo camera. Mobile service robots with the ability to track a specific person in dynamic environments have been required. In such environments, varying illumination and the presence of multiple people are challenges to carrying out target tracking. Color and location information is used for the target's features, that are useful for distinguishing a target from the other people. However, color information is not resilient to illumination changes. On the other hand, location information might be infeasible when non-target people present in the environments. Therefore, it is necessary to combine each information according to the situations, in which either information is infeasible to use as the feature. In order to make the system robust to varying illumination and presence of non-target people, a parameter of illumination changes is introduced in this paper. The parameter is defined using automatically adjusted white balance. The color and location features are weighted based on white-balance changes to determine a target. The effectiveness of the proposed system is verified through target-tracking experiments in outdoor environments. It is demonstrated that the proposed method can successfully recognize a target in the environments where the lighting condition changes extremely and non-target people present.
In this present paper, we propose algorithm for selecting appropriate standing support equipment and a robot for persons in need of care based on the physical ability of the user. Although we have been developed assistive robots but users have not known which devices are appropriate for their physical abilities. We defined a maximum of vertical bearing forces of foot, hip and hand (foot : FF, hip : FHi, hand : FHa, normalized by weight) as parameters of physical ability because a person supports his or her body on foots, hip and hands when standing. Experimentally, we analyzed vertical bearing forces of foot, hip and hand and discussed the relationship between standing support equipment and robot and a maximum of vertical bearing forces during standing; we also investigated the algorithm for selecting appropriate standing support equipment and robot. Finally, we set the physical ability of the user of a standing support robot that FF is under 0.896±0.019 or FHi is under 0.802±0.010 and FHa is under 0.263±0.039, and confirmed that algorithm using physical ability measurement system in RT-Frontier.
This paper presents a novel algorithm that estimates energy consumption of exploration robots for the efficient mobility in natural terrain. The energy estimation method is beneficial to the energy management problem to establish the robot autonomy, especially in energy-limited environments such as planetary surfaces and isolated volcanoes. The key idea of the proposed approach is to employ the terrain classification into the dynamics-based energy estimation model, so that it can adapt to the variability of terrain properties. A vibration-based terrain classifier is proposed in this paper, which analyzes vibration signals in the time-frequency domain and learns terrain patterns by a supervised learning technique. The terrain classification results are used to determine terrain-dependent parameters in the energy estimation model. A field test has been conducted in a volcanic field to show the validity of the proposed algorithm. The proposed method successfully demonstrates the capability to estimate energy consumption, while it raises discussions about determining terrain types in real natural terrain.
The purpose of our research is to improve robot motion ability without depending on only actuator power by effectively exploiting the dynamic properties of a robot. In this paper, we focused on swing motion (e.g., throwing or kicking motion). The prime purpose in swing motion is to increase the kinetic energy of the end-link (e.g., hand or foot). In this paper, using a multi-link planar robot, we proposed a method to generate a robot motion for an explosive increase of the kinetic energy in the robot end-link. Humans increase the kinetic energy of the end-link by exploiting the dynamic properties during swing motion. The kinetic energy of the end-link increases because large energy produced by strong muscles in the center side of the body is transferred toward the end side. We constructed mathematical models to explain this mechanical phenomenon on the basis of the free vibration. Furthermore, we proposed a method to generate a robot motion for an explosive increase of the kinetic energy in the robot end-link using the models. The results of simulation experiments showed that the kinetic energy of the end-link increases because large energy produced by actuators in the center side of the robot is transferred toward the end side. Furthermore, the robot motion generated by our method is similar to a trajectory optimized based on energetic cost. Then, we proposed a method to generate a robot motion considering the torque limits of actuators by revising the method mentioned above. The results of simulation experiments showed that torques required by actuators are reduced by using the revised method.
We propose a new Grid-based SLAM method with partial map matching for considering previous sensor data in Rao-Blackwellized Particle Filter. The partial maps are built probabilistically as accumulated scan shapes for each particle. In conventional Grid-based SLAM methods, Rao-Blackwellized Particle Filter is often used. However, the conventional methods sometimes fall into misalignment and fail to build proper maps in large or limited visibility environments. In those environments, the sensor data becomes insufficient shape to match with maps for localization since the sensor field of view is limited. It causes misalignment and failure in localization and map building. Rao-Blackwellized Particle Filter of the conventional methods is based on a Hidden Markov Model that uses only current sensor data to estimate robot poses. Hence, if the current sensor data is insufficient, it is difficult to estimate robot poses and build maps correctly. In our new method, the Hidden Markov Model has been extended to utilize a series of sensor data from the past in several seconds to the present. The series of sensor data is accumulated to make scan shape sufficient for the matching in localization. Thus, the proposed method is expected to cover the lack of sensor field of view by means of the accumulation of sensor data, and is capable of mapping in large or limited visibility environments. In our experiments at Tsukuba Challenge 2014 and Tsudanuma Campus, consistent maps were built only by the proposed method. Shape errors of the maps built by the proposed method were smaller than the conventional method.
In many sports, essential skills exist in terms of muscle activation in order to improve performance. However, it is difficult to identify the important muscle activation, and moreover novices cannot observe and imitate it since muscle activation is hardly visible. This study especially focuses on human rowing motion to extract an important skill in terms of muscle activation and we develop skill education system for novices to learn the skill. Firstly, strength and activation timing of lower leg muscle are evaluated to detect the expert skill based on their peak value and cross correlation during movement. Next, new skill education system is suggested by simultaneous presentation of real human movement and muscle activations of the targeted muscle. In the proposed system, muscle color is continuously changed based on its activation level for novices to perceive their muscle activation visually. Both experts and novices participated at our skill extraction experiment to compare their muscle activation. Results showed that experts had larger peak activation level and different profile in rectus femoris muscle. Therefore, our skill education system focused on rectus femoris muscle to present its activation level and movement simultaneously. In order to evaluate efficacy of the developed system, four different education instructions were conducted to novices; linguistic education, simultaneous presentation of motion and muscle activation of the expert, off-line presentation of novice's motion and muscle activation, and real time presentation of novice's motion and muscle activation. Performance of novices was evaluated after each instruction based on peak activation level, cross correlation, and exerted power on the rowing ergometer. These performance change after each education implied providing integrated view of novice's motion and muscle activation in real-time could improve performance of rowing motion.
The hammering test has been widely used for inspection of social infrastructures because of its accuracy and efficiency of operation. In order to automate and apply the method to actual inspection sites, it is important for the system to calibrate itself against various environmental noise sources, such as strong winds, that influence the accuracy of the acoustic diagnosis. In this paper, a boosting based diagnostic algorithm with an updation rule for the weak learners that constitute the whole defect detector is proposed. Both clean and defective hammering sounds are templatized in the frequency domain, and inner parameters of the weak learners are optimized by using the pair of frequency template vectors. Furthermore, a new updation rule for template vectors is proposed. In experiments, our method was applied to defect detection of concrete test-pieces having slant cracks, which are considered to be serious defects in inspection sites. From the results, the effectiveness of the proposed method was confirmed.
Three-dimensional analysis of aurora is important for the research of solar wind and magnetic storms, because aurora reflects the relationship between solar wind and terrestrial magnetism. Therefore a method to reconstruct a three-dimensional shape of aurora precisely is demanded. In this paper, a method to measure three-dimensional shape of auroa by using only two fish-eye cameras is proposed. Two fish-eye cameras were installed at Fairbanks, Alaska, U.S.A to get the time series images of aurora. The images photographed by the cameras are performed calibration by using the star to estimate the camera attitude. The dense feature points are detected from the images of aurora by using template matching though the image of aurora has few characteristic pattern. Moreover, a feature point tracking between two images continuing in time is performed to improve precision of the feature point detection. Then the three-dimensional coordinates of feature points are calculated by triangulation, aurora shape is measured and visualized.
Low cycle fatigue tests at elevated temperature were conducted on a Ni-based directionally solidified superalloy subjected to transverse loading. To investigate the effect of the arrangement and the orientation of crystal grains on the crack initiation, the electron back-scatter diffraction (EBSD) method was applied on the surface of the tested specimens. In addition, finite element analysis that considered the plastic behavior of crystal grains and the crystal grain shape on the specimen surfaces was performed to evaluate the relationship between the crack initiation and the local stress that develops near the grain boundaries. The results are summarized below. As for the effect of crystallographic properties in the specimen surface, many cracks initiated near the grain boundaries that neighbored the grains whose secondary axis was inclined to the normal direction of specimen surface by more than 35 degrees because the longitudinal stress larger than the nominal stress developed near those boundaries. The crack location was not confirmed to correlate with the grain boundary misorientation between the neighboring grains on the surface. However, most cracks initiated near the grain boundaries that neighbored the grain whose secondary axis was more inclined than the grain located in the opposite surface. The results of FEM analysis revealed that high stress developed near those grain boundaries. In addition, the location where high resolved shear stress developed generally corresponded to the crack location and that it correlated with the number of crack initiation cycles.
In this study, a systematic investigation on the effect of welding conditions on longitudinal bending and angular distortions generated in welded thin plate was experimentally performed with a focus on whether or not the weld buckling distortion occurs. Real-time measurements of temperature profiles and distortion behavior during welding of thin plate were also performed for a more detailed understanding of generation process of weld distortion in thin plate. As the results, longitudinal bending distortion monotonically increases, in which the degree is different depending on the plate thickness, with the weld heat input. Meanwhile, angular distortion does not show a linear increase with the weld heat input and can be arranged coordinately by a curve convex to the parameter of mechanical melting zone, which was proposed based on the theory of inherent strain by authors in previous study, when the weld buckling distortion does not occur. In this regard, however, angular distortion also approximately monotonically increases with either the weld heat input or the parameter of mechanical melting zone, when the weld buckling distortion occurs. This is because the angular distortion-generation process proceeds in the following two stages; angular distortion is primary generated due to inhomogeneous temperature distribution through thickness during welding and secondary in association with buckling behavior during cooling process after welding. This secondary stage results in buckling-induced large angular distortion in welded thin plate. It was thus clarified that it is important to understand the generation characteristics of weld buckling-induced inherent stress and strain especially in the secondary stage for accurate predicting and controlling the weld buckling distortion in thin plate.
Structural health monitoring has been used to confirm the durability evaluation and safety of a structure in which long-term use is required. Because the transmission loss of the optical fiber sensor is extremely small, it can measure the present status of structures from far away. Generally the FBG (Fiber Bragg Grating) optical sensing systems are often used to get reliable indices from structures. The shipping industry recently, there has been a growing interest in fuel efficiency improvements and energy regulation in international shipping. Therefore, during sailing, to measure the exact power of the main shaft of the ship has become important. We proposed the monitoring system using space optical transmitting of the FBG optical fiber to get information from a rotational shaft. And we evaluated the performance of the space optical transmission of the FBG optical fiber sensing system for rotational shaft in the previous study. Consequently, we reported that it can be effectively measured and space optical transmission metric is effective for performance prediction. In this paper, the strain and the temperature on the rotating torsion shaft, is measured by the FBG optical fiber sensor and the space optical transmission. We confirm reliability of the information that is retrieved from the rotating shaft subjected to torsion in the experiment. The conditions for reliable data from the rotating shaft under loading is obtained on the basis of the experimental results of the proposed systems.
High-strength, light-weight metal materials are required to improve safety and reduce transportation cost. Ultrafine-grained metals produced by severe plastic deformation have attracted interest as high-strength materials. In the case of ultrafine-grained metals, strong rolling texture induced by severe plastic deformation influences anisotropy of yield surface remarkably. However, measurement for the yield surface of ultrafine-grained metals requires a great deal of labor. A computational model predicting the yield surfaces of ultrafine-grained metals is desired in the field of materials science and engineering. In this study, using results obtained by electron backscatter diffraction, information on crystal orientation and shape of grains are introduced into a computational model for multiscale crystal plasticity simulation considering the effects of grain boundaries and dislocation sources. Finite element simulations for polycrystal of aluminum under biaxial tension are performed in order to predict yield surface of the ultrafine-grained metal. A genetic algorithm is used to derive the higher-ordered yield function of ultrafine-grained metal. The effects of crystal orientation on the macroscopic mechanical properties of the ultrafine-grained metals are investigated by the obtained numerical results.
In hydraulic turbine runners, accidents due to cyclic loading often occur, which are caused by large defects and residual stress introduced while making welding repairs of a part eroded by cavitation. In this study, we have aimed at improving the fatigue property of SCS6 stainless cast steel which has a propensity to develop large cracks and other defects, and bending fatigue tests were carried out to characterize the fatigue properties and fracture mechanism of the SCS6 when subjected to needle peening. The test result are summarized as follows: (1)The bending fatigue limit of 107 cycles on materials that underwent needle peening improved by 60% compared to that of untreated materials. A semi-circular slit measuring 2c=3.0mm and a=1.5mm is rendered harmless by needle peening. The high stress amplitude below the bending fatigue limit of 107 cycles, even if repeated, does not relax the residual compressive stress. (2) The bending fatigue limit is not affected by fatigue strength in the peening direction. Fatigue strength does not decrease even with a small amount of peening at a right angle and in a parallel direction. (3) It is possible to evaluate the fatigue life of the SCS6 by using the defect size √area and the initial stress intensity factor range calculated from the sizes of the defect and of the artificially induced semi-circular slit. The value of the threshold stress intensity factor range ΔKi･th for the defect corresponds to ΔKi+R･th, its value for the artificially induced semi-circular slit created by needle peening.
During heat-treatment when forging a large shaft, stress occurs due to temperature change and phase transformation, and special care should be paid to the heat treatment in order to prevent cracking. Therefore it is important to use the finite element method to estimate the stress and deformation resulting from the heat treatment. However, few previous studies treating large forgings in heat treatment simulations include phase transformation. In this report, the residual stress distribution of the test material after water-cooling and air-cooling was measured based on inherent strains, and heat treatment simulations considering the phase transformation and transformation plasticity were performed. It was found that, especially, the transformation plastic strain plays an important role to simulate the residual stress due to the heat treatment of the large shaft.
The fretting wear is caused by the very slight relative slip between the contacting surfaces of the inner ring side face and the backing ring of an axle journal bearing in railway applications, but its mechanism is not clear. In this work, first we have conducted a reproduction test using a full-scale railway axle journal bearing in order to understand the fretting wear behavior of the axle journal bearings. Secondly, laboratory tests using a full-scale railway axle journal bearing were conducted to investigate the contact pressure distributions by inserting a film pressure sensor between the inner ring side face and the backing ring of the axle journal bearing under the conditions of radial loads. It has been found that the fretting wear of the backing ring becomes larger in the proximity to its outside diameter, the contact pressure of the opposite of the load side is larger than that of the load side and the contact pressure becomes larger in the proximity to its outside diameter. Accordingly, the fretting wear area of the backing ring is approximately coincident with the area where the amplitude of the contact pressure is large.
This report deals with the influence of the interference between an elastic sphere and a spherical cavity on the stress distribution and displacement around cavity, which has simply a smooth elastic sphere, in an elastic solid under tension at infinity. The contact stress between the sphere and the cavity is expressed with series of Legendre functions, and the stress and displacement are numerically analyzed by point matching method. Using the numerical results for the elastic solid, the effects of interference and loads are shown on the stresses around the spherical cavity boundary. The main results are as follows: (1) The contact region and stress distribution of the elastic solid are independent of the magnitude of load, when diameter of sphere and spherical cavity are initially the same. (2) When diameters of them are not same, the contact region and stress distribution of the elastic solid vary with a change in magnitude of load.
A technique for high-accuracy predicting performance curve instability in pumps and clarification of the phenomenon in order to control the instability is required for designing high performance pumps. We analyzed internal flow of a test mixed-flow pump by using Large Eddy Simulation (LES) and clarified that Euler's head drop caused by stall near the tip of impeller blade is a dominant factor of this test pump's instability. We looked carefully at internal flow of impeller before and after the head drop, and also in the middle of the head drop. When the Euler's head drops, recirculation on the leading edge of the tip of impeller blade extends towards trailing edge. Angular momentum between tip and mid span decreases, and angular momentum near the tip is high. Work drop of the impeller on the side of leading edge caused by the stall on leading edge exceeds angular momentum increment caused by decreasing in flow rate on trailing edge, and so the angular momentum on the trailing edge drops. At that situation, the impeller blade load on the tip side shows state of stall. And, the stall fields occurred on the trailing edge cover whole impeller blade passages near the tip. When the head is in the middle of drop, only some impeller blade passages are covered with the stall fields.
It is necessary to evaluate the geometry factor for predicting the flow accelerated corrosion (FAC) in the plant piping. Geometry factor is defined as the ratio of the wall mass transfer coefficient in the piping systems such as elbow to that in a straight pipe. In this study, the mass transfer coefficient in 90-degree elbow with curvature radius of 1.5 times the pipe diameter is computed by using large eddy simulation (LES) and is also measured with electrochemical method. Numerical simulations and experimental measurements were conducted at Reynolds number of 15000. In order to simulate the mass transfer coefficient, we adopt the analogy between mass transfer and heat transfer, and calculate the unsteady temperature field using the numerical data of LES. The experimental measurement is conducted with point electrode. However, concentration boundary layer developed over the surface of point electrode is different from that developed for whole surface of pipe wall such as FAC in the plant piping. To cope with this problem, we calculated the temperature field in the two different boundary conditions. As a typical case, whole pipe wall is heated uniformly (in this paper, referred as ‘overall heat condition’). In addition, localized area is heated to simulate working point electrode (referred as ‘point heat condition’). Geometry factor obtained from the heat transfer rate in point heat condition agrees well with that measured with point electrode, however, both of them are qualitatively different from that obtained from the heat transfer rate in overall heat condition. Analysis of heat transport revealed that heat conduction is dominant form of the wall heat transfer in point heat condition, in contrast, turbulent heat flux affects strongly the wall heat transfer in overall heat condition.
Experiments were performed to investigate the deflagration-to-detonation transition (DDT) process in the channel equipped with repeated obstacles. A premixed gas of hydrogen-oxygen was ignited and the DDT process was visualized by using a high-speed video camera with an aid of schlieren optical method. A configuration of the repeated obstacle such as a spacing, d and a height, h were varied to investigate effects of these parameters on the detonation induction distance (DID) as well as DDT process. Furthermore, the flow-field was visualized by changing the directions of obstacle installation, such as vertical installation and transverse one. The DDT process could be clarified in detail, because the transverse installation of obstacle could acquire the flow-field in depth direction of the obstacle. As a result, it was clarified that the DDT was occurred by highly accelerated flame caused by the interaction between deflagration wave and the vortex-ring behind obstacle. Thus, the vortex-ring generated by the diffraction of compression waves was interacted with the deflagration wave, and this behavior produced a high-velocity deflagration wave through the unburned gas pocket behind obstacle. This high-velocity deflagration wave propagated in the depth direction could be a trigger of DDT onset via local-explosion. The detonation induction distance was also determined by observing a fish-scale pattern on the soot which was typical of the detonation propagation, and the relationship between DID and the configurations of repeated obstacle was also obtained.
There is increasing interest in the use of hydrogen as an energy source in fuel cells, and such cells are expected to find practical applications in the near future. However, the reaction rate of a hydrogen-air mixture is so high that the deflagration wave generated during ignition can easily become a detonation wave, even though only a small amount of energy is supplied to the premixed gas. Such a detonation wave can cause serious damage because of the high-pressure and temperature at the wavefront. Despite such concerns, the onset conditions for producing a detonation wave in a non-uniform mixture of hydrogen and air have not yet been fully clarified. In the present study, these conditions were investigated by changing the concentration of hydrogen to understand the onset condition of detonation wave. A vertical detonation tube was divided into two chambers using a slide valve; the upper chamber was filled with air and the lower chamber with hydrogen. A hydrogen concentration gradient was produced by opening the valve for a specific period of time. A pair of electret sensors was used to determine the concentration of hydrogen and the equivalence ratio by measuring the speed of sound in the premixed gas. The onset conditions for detonation were investigated by changing the overall equivalence ratio, φ, and the elapsed time, td, from the onset of diffusion. It was found that for φ= 1.67 and td ≥ 540 s, a detonation wave was produced leading to a large increase in pressure. Furthermore, the results indicated that the local equivalence ratio in the vicinity of the spark plug had an important influence on the initiation of the detonation wave.
Recently, electronics thermal management faces problems in the wake of component miniaturization, which has led to higher demands on heat flux dissipation. Pulsating heat pipe (PHP) can be used for cooling devices of electronics because of its potential for removing high heat flux. It is well known that various parameters affect the performance of the pulsating heat pipe. Therefore, many researchers have done research on the improvement of performance. This paper presents heat transfer characteristics of the open-loop pulsating heat pipe (OLPHP) using a self-rewetting fluid as working fluids. The heat transfer characteristic results were obtained by PHP that was made of copper tubes of internal diameters 1.8 mm. On the other hand, flow visualization tests were conducted by the use of a PHP that was made of Pyrex-glass tubes with the dimension of the copper tubes PHP. The experimental results indicate that OLPHP using self-rewetting fluid as working fluids can be observed anomalous liquid film behavior in adiabatic section. Especially, it was found that the liquid film was strong wavy when liquid slug moved to cooling section from heating section. The findings showed that the wavy liquid films and liquid slug behavior contributed to the thermal performance improvement.
The aim of this research is to investigate the operator's motor skill obtained by the skill training during the human-robot cooperative task. There are many studies to investigate the perception of the motion of the robot and the electromyography (EMG) signal of the operator's muscles in the human-robot cooperative task. The time series data of the motion of the robot and the EMG signal of the muscles differ depending on the individual motor skill of the human operator. Therefore, it is necessary to investigate the variation of the operator's motor skill. In former studies, the operators were made to subject the skill training to become skilled in performing the indicated task, however the motor skill acquired by the skill training have not been investigated in the field of the human-robot cooperative task. In this research, operators classified into three groups were trained on the following either of three kind of method; (i) the positioning task between the two target points (PTP), (ii) the tracking task following the target point, and (iii) the compound operation of the positioning task and the tracking task. In the positioning tasks after particular skill training, the motions of the robot are measured to investigate the operator's motor skill. To investigate the motions of the robot and the activity of the motor area of the subjects, the experiments were conducted in every month over a period of five months. The experimental results showed that there were significant differences in the motor skill and the activity of the motor area among the three groups.
For unmanned helicopters to be used in industrial applications, autonomous flight control is necessary. This study aims to shorten the time required to tune a controller and design a stable control system for model variation of unmanned multi-rotor helicopters. Designing model based controllers requires a significant amount of time and effort for model identification and the tuning of controller parameters. Additionally, changes in the dynamics of the plant lead to deterioration of control performance. In this paper, we propose adaptive I-PD control having on-line system identification mechanism for change-of-altitude direction of a helicopter to solve the problems that have been presented. First, the calculation of the altitude model and system identification mechanism are described. In order to guarantee the minimum phase property of the altitude model, we use the delta operator for system identification. We show the accuracy of the altitude model and the validity of the proposed system identification algorithm using flight data. Next, we design an adaptive I-PD controller based on the identified parameters. I-PD gains are adjusted sequentially by a partial model matching method. Finally, we demonstrate the validity of the proposed control system by way of a flight experiment. The experimental result shows we were able to design a highly precise altitude controller in about 10 seconds.
Many conventional robots consisting of rigid frames and active joints have been controlled based on the information regarding collision avoidance in human environments. When these robots collide with a human, he/she can be seriously injured if their sensor systems have a defect or the power supplies are shut down. So, we have developed a human friendly robot that consists of two arms, a body, and a mobile base. It is covered by an air cushion bag which simulates the skin of a human. In this paper, its waist is described, which consists of pitch, roll, and yaw axes. Also, a passive collision force suppression mechanism that is installed in each joints of the human friendly robot is proposed. The passive collision force suppression mechanism consists of two fixed and linear guides, two compression springs, a release system, and a disk damper. When a collision between the robot and the environment occurs, collision/constant forces are first suppressed by the air cushion bag. If a larger collision force is exerted on the robot, the suppression mechanisms will become passively activated and the joints of the waist will disconnect. The robot, moreover, is capable of returning to a desired task by using the suppression mechanisms if the environment is cleared. Through collision experiments, the effectiveness of the waist mechanism and the suppression mechanism is verified.
In human gait motion analysis, which is one useful method for efficient physical rehabilitation to define various quantitative evaluation indices, joint angles and joint loads are measured during gait. Recently, it is thought that trans-femoral amputees with the prosthetic limb must regain motion pattern by refined rehabilitation program using joint moments as a representative joint loads and understanding them is indispensable for biomechanical consideration. On the other hand, human keeps a high correlation among the motion of all joints during gait. Joint motion analysis of the correlation extracts a few simultaneously activating segmental coordination patterns, and the structure of the intersegmental coordination is attracting attention to an expected relationship with a control strategy. However, when the evaluation method using singular value decomposition has been applied to only joint angles of the lower limb, joint moments related to the rotational motion of the joints have not yet been considered. In this paper, a novel quantitative analysis method concerning rotational motion of lower limb joints by using joint moments as well as joint angles aims to be proposed. Each parameter of the healthy subject and trans-femoral amputee is measured by using mobile force plate and attitude sensor, split-belt treadmill simultaneously and their motion patterns are analyzed by the proposed method. As a result of the experiments, patterns of each evaluation index are obtained as the remarkably different feature quantities between healthy subject and trans-femoral amputee especially pertaining to joint moments. Finally, the effectiveness of the quantitative analysis concerning human motion is validated.
To reduce noise, Helmholtz resonators are widely used in internal-combustion engine intake systems, in the rocket engine's combustion chambers and building wall materials. As a bass-reflex-type loudspeaker, Helmholtz resonators may also be used to increase the sound pressure level. The advantage of using a Helmholtz resonator is that the frequency used to change the sound pressure level can be easily controlled by the resonance frequency and can be more easily applied to lower frequency noises than can porous sound-absorbing materials. A Helmholtz resonator is usually described in one-degree-of-freedom systems, wherein the neck portion is modeled as a mass, the damping of the neck as a damper, and the cavity as a spring. The noise reduction effect of a Helmholtz resonator (as in porous materials) is evaluated by its normal incidence sound absorption coefficient or acoustic impedance. Meanwhile, the effects obtained when the resonator is added to the main acoustic system are described in the same way as are the effects of the mass-tuned damper used to reduce mechanical vibration; such effects are determined by comparing the acoustic transfer functions of the main system with the main system after a Helmholtz resonator is added. This study first describes the two-degree-of-freedom mass-spring-damper model, which represents an acoustic system with a Helmholtz resonator. Next, the equation of the two-degree-of-freedom acoustic system is shown to be the same as that of the vibration system with a mass tuned damper when the damping coefficients are zero. Finally, the transfer function of the acoustic system using a Helmholtz resonator with heavy damping was found to approach that of the acoustic system without a resonator.
This paper deals with the quenching problem of electromagnetic vibration of the inverter motor stator. The iron stator of the inverter motor is modeled by a perfect circular ring. Single or two Houde dampers are installed on the outside of the circular ring to quench the forced vibration caused by the rotating distributed electromagnetic force. Moreover, single mass is set also on the circular ring. The solutions of forced vibration are obtained by the theoretical analysis. The following were made clear; (1) When the angle between two Houde dampers is equal to that between loop and node of the mode to be quenched, the resonant amplitude of the stator is reduced most. (2) By setting not only two Houde dampers in the suitable positions, the setting angles are apart almost 35°～65°each other, but also setting single mass which is imperfection for perfect ring, the vibration of motor stator is quenched over wide frequency region around resonance. (3) By installing single Houde damper and single mass, the vibration of motor stator is quenched over wide frequency region around resonance also. (4) The results by the ring theory coincide with those by finite element method.
Stability of a hydraulic operation stabilization system during valve returning motion was investigated by the measurement and numerical analysis of the hydraulic circuit. Inadequate selection of hydraulic circuit constants causes the returning motion unstable and valves repeat open-close motion periodically. Hydraulic circuit constants related to the valve returning motion were set as parameter and analyzed. The volume of the back space of a discharge valve which is connected with hydraulic return circuit is important on the motion stability, and hydraulic vibration occurs by the combination of the volume with other hydraulic circuit constants. The reach of the constants which influence the motion stability was considered. The small volume and proper selection of other hydraulic circuit constants make a hydraulic operation stabilizing system stable.
In Japan, a dry cask for spent nuclear fuel attached to a storage pallet should be transferred and stored in the vertical orientation on the concrete floor in an interim spent nuclear fuel storage facility at or outside reactor site, and a transfer system using air supply will be adopted for such pallet. In case of the hypothetical event, the shutdown of the air supply due to the strong earthquake motions, it is important to evaluate a stability of the metal cask on the concrete floor during seismic motions. A dynamic analysis by the analysis code "TDAPⅢ" was executed with a simple lumped mass model by adopting joint elements between a concrete floor and pallet, to reproduce the rocking and sliding behavior. Joint stiffness values were equivalently set to the vibration modes obtained by an eigenvalue analysis. The seismic analysis results were compared with the previous shaking table test results with 2/5 scale model of a real size cask. As a result, although discrepancies of the velocity response of the converted from maximum uplifting potential energy appeared in the range of μ ± 3σ (0.57～1.46) among 45 analysis cases comparing with experiment results, it was confirmed that maximum value was about 110kine considerably less than the overturning threshold value 190kine. Moreover, an applicability of the proposed prediction methodology to the real size model was also confirmed.
Oil film bearings are applied for large rotational machineries owing to their large load capacity and damping effect. However, a swirling flow of the lubricant induces self-excitation at high rotational speed. The stability margin changes during many years due to the mechanical wear and fatigue. Thus, stability diagnosis of the rotor-oil film bearing systems is required. In this paper, we focus on the onset rotational speed of self-excitation as a stability index. Firstly, a 2-DOF rotor-oil film bearing model is constructed using the mode synthesis method and Bently/Muszynska model for oil film bearings. Then, an estimation method of the onset rotational speed using frequency responses measured at lower rotational speeds than the onset one is derived from the model. Finally, a test rig consisting of a rotor supported with two oil film bearings and a radial magnetic bearing is fabricated and frequency response functions with forward circular excitation are measured by utilizing the magnetic bearing. The experimental result shows that the predicted onset rotational speed using the frequency responses at 30, 40 and 50 rps is 60.4 rps, and the error between the estimated and measured onset rotational speeds is less than 4 rps (6%).
In this paper, we propose a formulation method for flexible multi-body systems with mass loss. The method derives the equation of motion using the velocity transformation method, in consideration of the shift of center-of-mass. There are three research purposes in this paper. The first purpose is to extend the velocity transformation method for describing flexible bodies. Conventional velocity transformation method has only focused on the dynamics of rigid bodies. The restoring force due to flexibility is introduced to the equation of motion as generalized external force. Our proposed method can deal with rigid, elastic, or geometric connections, such as hinge and sliding joints. The second purpose is to formulate flexible multi-body systems with mass loss. Conventional Kane's technique only deals with the dynamics of particles. On the other hand, the proposed method can express the dynamics for the mixed model of particles and rigid bodies, where particle elements express the mass change of the system. The third purpose is to verify the high usefulness of our method for the dynamics simulation of a flying rocket. The rocket is a representative multi-body system whose mass varies. We analyze the flight characteristics, such as pitch angle, for rocket models associated with the variation in stiffness. The simulation indicates that the mass loss greatly affects the dynamics of rockets. The calculation demonstrates a large difference in the flight dynamics between rigid and flexible models.
In recent years, surgical robots have come into wider use. These robots do not yet provide a force sense to the surgeon, but such force sense will be necessary on the next generation of surgical robots. When the slave motor needs to generate a larger or smaller driving force than the master motor, mechanical gearing is normally used. This leads to large mechanical losses. A small force sensed at the slave cannot be transmitted back to the master. We have proposed a master-slave system of the series connection type that generates a force sense using conventional bilateral control. However, when linking together motors of different output power, the allowable current of the small power output motor is insufficient to drive the large power output motor. We now propose a method that combines a motor with a shunt resistor. If a resistor is connected to a motor in parallel, the allowable circuit current increases, removing the current limitation and increasing the circuit current. This approach also allows the variable force to be sensed by changing the shunt resistor. We experimentally confirmed the effectiveness of the proposed method. In this paper, the principles of using a shunt resistor for changing the force sense are explained, and our experimental results are presented.
Remotely operated mobile robots are demanded in many disaster fields, such as Nuclear/Biological/Chemical(NBC) terrorist attacks, earthquake and tsunami, and even in minefields, to assure safety for the human workers. It is a common choice to use commercial game controllers with joysticks and buttons to control such robots, but many complex manipulation tasks require much higher operability only achieved by Master-Slave systems. In this research, we propose a new bilateral remote controller called “Armrest Joystick” which has Master-Slave function and also presents high operability characteristics. It consists of : (i) a 3DOF position arm mechanism which is attached to a foldable portable chair, and the foremost link part acts as an armrest to support the operator's arm; (ii) a 3DOF wrist posture mechanism whose rotation centers were carefully designed to match the human hand; (iii) a gripper mechanism which has good follow-up performance for fingers. Furthermore, all 7 joints (axes) are equipped with electrical motors and are actuated to give the operator Force Feedback. In this paper, we report the basic concept and explain in detail the mechanism design of the Armrest Joystick, and then show the experiments to check basic performance, specially about the armrest, and which we conducted using an actual rescue robot as “slave”. The results verify the validity of the mechanical design, and show that the Armrest Joystick can be more intuitively used than the former commercial game controllers.
On a metal wire with a self-healing function of a crack using electric field trapping of metal nanoparticles, we examined a healable crack width by using the different particle size. The electric field trapping is a phenomenon where the nanoparticles are trapped in the crack by the electric field in the region of the crack only, when a voltage is applied to the cracked wire covered with the nanoparticle solution. In this paper, first, we theoretically analyzed and calculated the particle size dependence of forces acting on the nanoparticles. Next, we fabricated gold wires with patterned cracks on a glass substrate, and measured the healable crack width by comparing 20 nm, 100 nm and 200 nm in particle radius. In the experiments, gold nanoparticles aqueous solution was used as nanoparticles solution. As a result, in the each case of 20 nm, 100 nm and 200 nm in particle radius, cracks up to 1.5 μm, 2.5 μm and 4.0 μm were successfully healed by applying less than 4.2 V in amplitude and 100 kHz in frequency of AC voltage, respectively. These results indicate that the larger nanoparticle can heal the wider crack with the same cross-sectional shape of the wire and the approximately same applied voltage. After the experiments, we confirmed that assembled nanoparticles were bridging the crack at the inside of the crack through scanning electron microscope (SEM) observations.
This paper proposes a novel implementation scheme of geometrically nonlinear finite element programs, which automatically compute exact internal force vectors and element stiffness matrices by numerically differentiating a strain energy function at each element. This method can significantly simplify the complex implementation procedure which is often observed in conventional finite element implementations, since it never requires B matrices, stress tensors, and elastic tensors by hand. The proposed method is based on a highly accurate numerical derivatives which use hyper-dual numbers and never suffer from any round-off and truncation errors. Several numerical examples are performed to demonstrate the effectiveness and robustness of the proposed method.
Smoothed particle hydrodynamics (SPH) is a particle method for analyzing physical problems. But this method has numerical problems when treating multilayer problems and free surface. In this report we propose equations to treat multilayer heat conduction problems and normalized equations to avoid the edge effect which is caused by the lack of particles at the free surface. Numerical results, in the case of 1 layer heat conduction model has good agreement with results of difference method. Numerical results in the case of 2 layer heat conduction model, where the ratio of heat conductivity of 2 layer is changed from 5 to 50 shows that normalized equations are effective to treat multilayer heat conduction problems.
In this study, we developed an intuitive remote-controlled manipulator system that was operated using a touch panel display and a mouse. We examined its application possibility to pick out the shoot apical meristem from sprouting potatoes. The shoot apical meristem is not easily affected by plant viruses. Therefore, we can obtain a virus-free seedling that has a high production efficiency by culturing this part. This technique is called “mericlone” and is known widely in agriculture; however, it is tedious because of the precision work involved with a microscope. Thus, our system not only reduces the burden on the technician but also has high precision control and saves space. In this study, using the loop-mediated isothermal amplification method, we confirmed that we could get the potato meristems that do not contain Potato Virus X. The newly designed primer set can achieve results more rapidly, more easily, and with higher sensitivity than other virus detection methods, thus indicating the possibility of industrial implementation.
The kinematic motion deviations of the five-axis machining centers are deeply influenced by the geometric deviations of the components, such as guide-ways and bearings. A systematic design method is required for specifying suitable geometric tolerances of the guide-ways, in order to improve the kinematic motion deviations of five-axis machining centers. The objective of the present research is to establish a computer-aided design system for specifying a suitable set of the geometric tolerances of the guide-ways considering the trade-off between the requirements on the kinematic motion deviations and the ease of the manufacturing processes. A mathematical model was proposed in the previous papers to represent the standard deviations of the shape generation motions, based on the tolerance values of the guide-ways of the five-axis machining centers. A systematic method is proposed here, by applying an optimization method, to determine a suitable set of the tolerance values of all the guide-ways under the constraints on the kinematic motion deviations between the tools and the workpieces. The method is applied to some design problems of the geometric tolerances of the guide-ways included in the five-axis machining centers.
In recent years, needs for micro drilling are increasing, accompanying the development of higher wiring density of printed circuit board (PCB). When drilling PCB for the purpose of making the electric through holes, it has been said that the drill breakage is caused by being filled the chips of GFRP and copper of PCB in the drill flutes. Series of drilling tests of PCB have been carried out to investigate the shape of chips produced and the chips evacuation behavior out of drilling hole of the drill at the rotational speed of from 20×103min-1 to 160×103min-1. The chips evacuation behavior out of drilling hole of the drill is filmed by a high-speed motion camera and the shape of chips produced is observed by a microscope. The chips of GFRP are short and small pieces with an increase in the drilling rotational speed. The evacuation out of drilling hole of the drill is very well and both of maximum cutting torque and average cutting torque are decreasing with an increase in the drilling rotational speed. When drilled at rotational speed of 160×103min-1, the chips of GFRP are long and large pieces, on the other hand, the chips of copper are short pieces, and chips evacuation out of drilling hole of the drill is almost not worse with an increase in the tool wear.
How a wound roll stress distribution will change when a nip roller is used during winding, and how a wrap angle around the nip roller will affect the roll stress distribution, these are investigated by simulating a winding process of two-dimensional models composed of a web, winding core and nip roller using a FEM software. The results show that the roll stress distribution is classified into the following three groups, (G-I) no nip roller, (G-II) nip roller with zero wrap angle and (G-III) nip roller with non-zero wrap angle (90, 180 deg.). The roll stresses increase in this order. The stress distribution of (G-III) is almost the same even though the wrap angle changes. Macroscopic slipping patterns (like J-line) of wound rolls indicate that large friction forces due to a nip load pull the outer layers to the core rotational direction. A summation of friction forces acting on the web surface having contact with the nip roller is zero, when no external torque acts on the nip roller. This indicates the stress distribution of (G-III) is almost the same. The friction force (the slipping velocity) is generated by a strain increase due to the wrap angle and a V-shaped tangential strain distribution due to contact with the nip roller.
Taylor-made designs are required for golf clubs, in particularly for golf shafts, because the golf equipment have great effects on the performances of players. Our objective is to establish an optimal design method of golf shafts for each player depending on their swing motions. We measured the swing motions with a 6-axis sensor that inserted into the grip end not to prevent normal motions. We analyzed the head motions at the impact using FEM with the swing data, and we tried to figure out the best shaft spec for an optimal impact. The optimization algorithm was followed 4 skilled shaft designers, which means that we had optimized the 4 SPECs in turn as below; 1) Weight, 2) Torque, 3) Flex, 4) EI pattern. As a result, the distance of a subject, a female professional golfer of JLPGA, was improved 11yrd more with the optimized shaft, and she uses the optimized shaft for more than 2 years. Thus our method was proven to be efficacious for some typical players. On the other hand, we were not able to get desired results for another 2 subjects. We believe the causes of undesired results are that some players change their swing motions depending on the shaft spec. We ought to consider the motion adjustment depending on the shaft spec in order to design optimal golf shafts for each player in the near future.
In this paper, two foot strike patterns, which are the rear foot strike (RFS) and the fore foot strike (FFS), are compared from the viewpoint of the joint moment, joint reaction force and muscle activity using the actual measurement of running for two subjects. As the results, the landing reaction force has two peaks for RFS while one peak for FFS, and the significant features can be observed in the ankle joint rather than the knee and hip joint. The joint moment of the ankle joint for RFS acts toward the dorsal flexion direction at the beginning of landing, and then toward the plantar flexion direction, while the one for FFS acts toward the plantar flexion direction during landing. The bone-on-bone force for RFS shows two peaks as similar with the landing impact force. For RFS, the Tibialis anterior much works while for FFS, the Gastrocnemius and the Soleus works much. Moreover, the differences of subject A and B are shown as the contribution of joints on the running.
In this paper, we propose a visualization method to integrate significant amounts of information relative to human motion to facilitate convenient visual perception during motor learning. This motor learning system helps subjects acquire developed motor skills by referencing integrated information of optimized motion data using a visualized motor skill map. In the proposed method, a self-organizing map (SOM) is employed to visualize the integrated motion data. It is expected that subjects can perceive optimized motor skills involving the activation of various muscles easily by comparing the trajectories of integrated data of optimized motion and that of human subjects wearing inertial and electromyography (EMG) sensors. Here integrated information is comprised of muscle activation signals, joint angle and joint angular velocity, and was visualized with a SOM as a two-dimensional map. To search an optimal landing motion, the human body was modelled as a musculoskeletal system composed of eight rigid bodies and nineteen muscle-like actuators. We performed numerical optimization using muscle-actuated forward dynamics simulations with a multi-objective genetic algorithm. Then, we created a motor skill map by using SOM with motion data that we got by optimization and experiment. We visualized motion characteristics as a color map, and compared optimized motor skills and subject’s motor skills using the obtained SOM.
The objective of this study is to reduce intersection collisions that are one of the most common types of accidents in Japan. This paper proposes an autonomous driving system that stops at the stop line automatically before entering intersection, re-start and autonomous brake with safety confirmation against crossing vehicles to reduce intersection collisions. This is so-called autonomous “Two-stage stop and start driving operation”. The system is based on recognition of surroundings by digital map and millimeter wave radar. Millimeter wave radars are used to detect crossing vehicles since they have long detection range and excellent robustness to weather condition. Furthermore, the designed autonomous driving system is implemented in the experimental vehicle and the effectiveness of the system is verified by performing test drives in a test course intersection. As a result of running test, the experimental vehicle certainly stops at the stop line before entering intersection, and in the re-start phase, the vehicle can stop automatically when a crossing vehicle is detected and then accelerates again when the safety is confirmed.