Flight control system with position compensation applicable to trajectory tracking of agile maneuvers that require an attitude rotation and a reverse of main rotor thrust of single-rotor helicopters is proposed. The outer loop position compensator calculates the desired attitude and rotor thrust which reduce position tracking error by utilizing a kinematics equation established near the reference trajectory. The desired attitude is set using the magnitude of the rotor thrust in the reference trajectory, which enables continuous position feedback compensation based on the fact that the relationship between rotational and translational motion becomes independent as the rotor thrust decrease. To achieve high-bandwidth control of lateral-longitudinal angular rates in the inner loop, two-degree-of-freedom servo system is designed using a linear model with blade flapping motion dynamics. The control system is applied to autonomous control of flip maneuvers which include transition between upright and inverted hovering. The reference trajectory of a flip maneuver is generated as a parameterized simple equation which can be adjusted to the helicopter ability. Simulation and outdoor flight tests of the autonomous flip maneuvers demonstrated the capability of position feedback compensation that reduces position tracking error during out-of-trimmed flight state. This control technique can be extended to various agile flights for quick execution of flight tasks or recovery maneuvers from dangerous state.
Sport riding performance on racing circuits and other locations is seen as an important element in the marketability of motorcycles. In sport riding, some riders start a turn while braking or start acceleration (driving) while turning. Furthermore, the braking aspect of sport riding performance is also critical to accident avoidance performance since it is similar to that of the braking during cornering performance. Consequently, in this paper a fundamental study was carried out to determine methods for improving the cornering limit performance during driving and braking. In the case of four-wheeled vehicles, the G-G diagram is used as a method to indicate the cornering limit performance. In the G-G diagram the longitudinal driving and lateral driving of the vehicle are set as the two axes. Therefore, the first part of this paper proposes a G-G diagram for motorcycles theoretically. In the latter part of this paper, this paper discusses the braking force distribution ratio of front wheel that would maximize the maximum lateral driving, the influence of the normal load distribution ratio of front wheel on the limit cornering property and the influence of the height of the center of gravity on it. From these result, this paper proposes methods for improving the cornering limit performance while braking.
This paper presents a method of correcting distortion in 3D laser-scan data from in-vehicle multilayer laser scanner. A robot identifies its own 3D pose (position and attitude) in a laser-scan period using the normal-distributions transform (NDT) scan-matching method. Based on the pose information, the robot's pose in a period shorter than scan period under the assumption that the robot moves at almost constant linear and turning velocities. The estimated pose of the robot is applied to map laserscan data onto a world coordinate frame. Subsequently, the robot again identifies its own 3D pose from the mapped scan data using NDT scan matching. This iterative process enables the robot to correct the distortion of laser-scan date and accurately map the laser-scan data onto the world coordinate frame. Two methods for correcting the laser-scan data are presented: linear-interpolation based and Kalman-filter based methods. The former applies the extrapolation and interpolation to estimate the vehicle pose, while the latter applies the prediction, estimation, and smoothing. Experimental results of mapping a signal light in a road environment show the performance of the proposed two methods.
This paper considers ways to increase stability of wheelset hunting. The aim of this study is to introduce formulas which represent the damped natural frequency and its damping. This has been done by analytical and not by numerical calculation. These formulas are functions of mass, creep coefficient and other wheelset parameters. These formulas are obtained with a 2 degree of freedom wheelset model whose radius of gyration of yaw equals to a half of gauge and whose creep coefficient is isotropic, in the first part of this paper. In the second part, based on one of these formulas, ways to increase damping of wheelset hunting are discussed. First, it is shown that a longer wavelength of geometrical hunting is effective in reducing hunting at all vehicle speeds. Secondly, it is shown that at speeds slower than a certain speed, the damping is increased when the ratio of the wheelset mass to the creep coefficient is larger. Further, a symbolic formula for this boundary speed is obtained. Thirdly, if it is assumed that the wheelset mass is proportional to the square of the wheel radius, then at speeds higher than a certain speed, the damping is increased when the wheel radius is larger. Moreover a symbolic formula for this boundary speed is also obtained.
In recent years, railway system is attracting attention in terms of energy efficiency and environment friendliness. Rail of railway is one of the most important elements in constructing railway system. Railheads are subjected to severe contact with wheels during repeated passage of vehicles. As a results of severe contact with wheels, wear of rail or rail defect have been occurred on railheads. Rail profile will be changed due to wear development. Worn profiles of rail have changed complexity in each section because the condition of wheel/rail contact has changed gradually, according to the running condition of vehicle and track geometry condition. Therefore, it is very important to predict the worn profiles of rail based on the analysis of vehicle dynamics. Previously, we constructed the prototyped model for predicting worn profiles of rail with Simpack. However, the validation of this model has not been verified. In this study, we conducted the wear experiments by use of full-scaled wheel/rail rolling contact equipment to distinct the coefficient of wear and to measure the worn profiles for validating the prediction model. Moreover, we analyzed the worn profile of rail in the same contact condition with the wear experiments. Finally, we considered the results of wear depth and the contact patch of wheel/rail discs of this equipment in analysis and experiments. As a result of the analyses and experiment, the analytical model was confirmed being valid to predict worn profile of rail.
It is pointed out that the yaw dampers, which are often installed in between carbody and bogie frame of a high-speed railway vehicle, have such unfavorable points that the damping force is generated not only in the yawing direction but also in other direction. As a result the damping force is generated also to the longitudinal or pitching vibration of a bogie, and the excitation force acts in the longitudinal direction of the carbody resulting in the increase of the carbody vibration of the longitudinal or vertical direction. In this research, to enable the reduction of the excitation of the carbody vibration while maintaining the original function of yaw dampers to prevent bogie hunting motion, a new mounting structure of yaw dampers on railway vehicles has been developed. The new mounting structure enables to reduce the excitation force transmitted from a bogie frame to a carbody through yaw dampers. In this paper, the effect of yaw dampers on the carbody vertical vibration is firstly shown based on the results of an excitation test of a full-scale vehicle, then the outline of the new mounting structure for yaw dampers and the design and manufacture of the prototype device are presented. The vehicle dynamics model based on multi body dynamics was constructed and the suppression effect of the yaw damper force generated to movement in the direction other than the yawing direction of a bogie was verified by the numerical simulation. Moreover, the prototype device was installed on a full-scale test vehicle and a bogie hunting motion test was carried out to verify the running stability.
It has been well known that the drivers' looking aside behavior is one of the cause of traffic accidents. However, it is difficult to investigate the causal relationship between the looking aside and accident. The authors analyzed the features of drivers' looking aside behavior by using the drive recorder data. It is found that this behavior occurs when three conditions stated below are satisfied. The first one is that the time headway is long enough. The second one is that the required deceleration for collision avoidance is supposed to be small. The third is that there is enough time for the drivers to push brake pedal and stop the car safely. Drivers' looking aside behavior under dangerous situation doesn't always lead to an accident, but when the looking aside period is too long, this behavior tends to cause an accident. In addition to the above, it is found that in the low speed range, drivers try to keep a constant headway distance. The mechanism of this trend is clarified.
It is thought that the first step to understanding vehicle movement is to measure and analyze that movement in order to confirm that it falls within the range of the laws of physics. In the case of a four-wheeled vehicle, in general, the friction limit is defined within the circle of longitudinal acceleration and lateral acceleration through the use of a G-G diagram. Then measurements are taken to confirm that the driving state is within that range. Two-wheeled off-road vehicles are mainly ridden on slippery dirt roads that include steep slopes and rough, uneven surfaces. An analysis method for the driving state and the vehicle movement limits that would be suitable for analyzing the movement of such two-wheeled off-road vehicles under these conditions was examined. These movement limits were then formulated by taking into consideration the coefficient of friction and the road surface gradient in accordance with the basic laws of physics and also by focusing on the vehicle movement in the longitudinal direction. Measurements were also taken during actual off-road riding by top-class Japanese off-road motorcycle riders. It was confirmed that this measurement data was distributed within the range of the assumed vehicle movement limits. Consequently, it was confirmed that it is possible to use such measurements to accurately grasp the vehicle movement limits and the associated driving state for two-wheeled off-road vehicles.
Aiming at the realization of agile autonomous flight for the extension of the flying range of single-rotor helicopters in the limited flight time, the flight control system design and the control performance verification for the high-speed turn flight are conducted. To achieve the reference following control for large attitude angles and the rotor thrust, the control system is composed of the main-rotor thrust and body torque centralized controller based on the MIMO (Multiple-Input, Multiple-Output) helicopter model including the blade motion dynamics, rotor speed proportional-integral controller, the attitude controller designed via the backstepping method based on the quaternion attitude model, and the guidance controller based on translational motion model. Simulation results show that the hovering and 10-m/s straight cruise flight followed by over 45-degree bank turn is feasible by using the proposed control system. In addition, flight tests have been conducted using the experimental small unmanned electric helicopter equipped with the flight control computer, and the high speed turn agile autonomous flight was successful in the real environment.
In this study, the relation between the thermal environment and the thermal comfort of occupants in a main line vehicle in the summer was investigated. At first, to understand the characteristics of the thermal environment in a main line vehicle, a field survey was conducted by measuring the temperature and humidity in regular passenger services from the morning to the night. The observation range of the temperature was from 23°C to 28°C, and that of the humidity was from 38%rh to 68%rh. Then, to obtain the fundamental data about the occupants’ thermal comfort, a subjective experiment in which 44 subjects in total participated was carried out. The subjects rode a main line vehicle stationed at a rolling stock center, and they experienced the temperature changing approximately in the range observed in the field survey and answered the questionnaires about their thermal comfort. Furthermore, the relationships between the thermal indices called PMV/PPD and the subjective evaluation values were analyzed. As a result, it was indicated that the error of the PPD in predicting the percentage of dissatisfied subjects became large in the range PMV>0, where the effect of the sweat sensation became significant. However, the PPD agreed well with the actual percentage of people who reported to have the feeling of ‘slightly cold’, ‘cold’ or ‘slightly hot’, ‘hot’. Our results suggest that the PPD can be used as an index of the variability of thermal sensation, but not as an index of thermal comfort in a main line vehicle in the summer; in order to use the PPD as an index of thermal comfort all the year around, it should be corrected taking into account the seasonal characteristics of the relation between the PMV and the actual percentage of dissatisfied occupants.
Many articles have reported that the white lines painted on both sides of highways are used by automatically driven vehicles to control their lateral movement when driving. They are detected by stereo cameras or radars. And GPS is used as an additional information for improving its robustness and reliability. However, when we think about an urban area, the stereo cameras and radars cannot recognize any white lines because white lines do not exist at intersection. Therefore, a method for controlling a vehicle without environmental recognition becomes necessary. In our method, the steering angle is controlled by using simple map information comprising nodes and links of roads, which are widely used in navigation systems, and the data of the vehicle's position, which is obtained continuously. In addition, by using two front gaze points to solve the problem associated with one front gaze point, we propose a method that allows a vehicle to steer smoothly when turning at intersection. We performed an experiment using an actual vehicle under the same conditions as those used in the simulation. The results confirmed the validity of our proposed method because the target steering angles at each corner and the driving trajectory of the actual vehicle were almost the same as those obtained using the simulation.
This paper proposes mathematical models to predict preceding car's deceleration intent and evaluates its effect on the following car driver in terms of the mitigation of risk of rear-end collision. Assuming a four-vehicle convoy, an unscented Kalman filter (UKF) integrated with a conventional car-following model attempt to estimate the headway and velocity of the 1st to 3rd vehicles in the platoon. The car following model used in this research is the conventional Gazis-Herman-Rothery model (GHR model). Then, another GHR model is used to predict the deceleration intent of the 3rd vehicle, which is expected to occur 1.5 seconds later based on the estimates of headways and velocities. In addition, this study proposes an interface to inform the predicted intention to the following vehicle by using a windshield display (WSD). Numerical analyses showed that the UKF integrated with the GHR model succeeded in estimating the vehicle platooning states and predicting the deceleration intent accurately. However, the prediction does not always shows the perfect match with the actual observation due to the uncertainty of driver's behavior. Although it is not completely accurate, it is a quite useful information to mitigate the collision risk so that we decided to design the interface by the WSD to inform the predicted deceleration intent to the following car driver. A driving simulator experiment was carried out to present the 3rd vehicle deceleration intent expected to occur 1.5 seconds later to the 4th ego car. It was found that the maximum deceleration rate of the 4th vehicle was suppressed and the value of the Time-To-Collision was increased not only in an ordinal deceleration case but also in a situation where the collision risk became significant.
This paper describes an investigation on the nonlinear filter that can realize its gain and phase characteristics independently. In the driver-vehicle closed loop system, it is reported that there is an optimal value in vehicle phase delay, i.e., excessive large or small delay deteriorates vehicle maneuverability. However, there is a strict relationship between the gain and phase delay in linear system. It is difficult to evaluate the gain and phase delay of vehicle response independently. In this investigation, we tried to design a non-linear filter that can set the relationship between gain and phase delay arbitrarily by using neural network. We investigate the effect of the gain and phase delay corresponding to the steering angle input on the ease of driving by using driving simulator, and evaluate the control performance on the lane change task. We verified that the ease of driving is improved by reducing a phase delay and decreasing a high frequency gain.
Considering in design by analysis, four types of tests, slow-strain-rate tensile (SSRT), fatigue life, fatigue crack-growth (FCG), and elasto-plastic fracture toughness (JIC) tests, were conducted with low-alloy steels, JIS-SCM435 and JIS-SNCM439, in 115 MPa hydrogen gas and air at room temperature (RT). In addition to above tests at RT, the SSRT tests were also conducted in 115 MPa hydrogen gas and air at 120 oC and in 106 MPa hydrogen gas and 0.1 MPa nitrogen gas at -45 oC. The low-alloy steels used in this study had tensile strengths (σB) ranging from 824 to 1201 MPa with fine and coarse tempered-martensitic microstructures. In the SSRT and fatigue life tests, the tensile strength and fatigue limit were not degraded in hydrogen gas. The FCG tests revealed that the FCG rate (da/dN) was accelerated in hydrogen gas; however, there existed an upper bound of the FCG acceleration, showing the FCG rate in hydrogen gas was about 30 times larger than that in air, when σB was lower than 900 MPa. The JIC tests demonstrated that the fracture toughness (KIC) in air was 207 MPa·m1/2 at σB = 900 MPa, whereas the hydrogen-induced crack-growth threshold (KI,H) was 57 MPa·m1/2 at σB = 900 MPa. Based on these results, we proposed advanced guidelines on the use and design for SCM435 and SNCM439 on design by analysis in 115 MPa hydrogen gas, which enable to design the storage cylinders used in 70 MPa hydrogen station with lower cost without compromising safety.
We have investigated the sedimentation phenomenon in a colloidal dispersion composed of spherical ferromagnetic particles using Brownian dynamics simulations. We have attempted to clarify the conditions under which all particles settle down and a thin film is formed, by varying the applied magnetic field, magnetic force between particles, mass density, and temperature of the solution. The particle concentration was set so that the average inter-particle distance was 2.5 times the particle diameter. The main results obtained are summarized as follows. When the mass density is increased, the sedimentation rate increases due to the influence of gravity. The sediment is deposited at the bottom layer immediately after being dropped, and the particles display a stronger tendency to settle down at the bottom layer. However, as the magnetic force between the particles increases, the bonding between the particles becomes strong and clusters are formed, which makes it difficult to obtain the desired thin film in which all particles precipitate at the bottom layer and exist separately. Even in such a situation where the influence of the applied magnetic field is dominant, a thin film can be obtained if the magnetic moment of the particle is strongly restrained in the direction of the magnetic field, thus preventing the formation of clusters. In addition, when the density ratio is as large as 30 as is in this case, a planar cluster may be formed in the lowermost layer even when all the particles have settled down. On the other hand, if the temperature of the liquid is too low, the clusters remain intact without collapsing because of the low random force. As a result, the desired thin film cannot be obtained. However, there is a limitation where in the number of conditions under which the thin film formation occurs does not increase when the random force value exceeds a certain level.
We propose image processing method for road white-line detection using brightness gradient direction of edges. Many methods for white-line detection have been proposed for standardized roads. These methods use model fitting for the detection of edges on white-line contour. So it is difficult to apply these methods to non-standardized roads for which modeling is difficult. To expand the scope of white-line detection to common roads in the future, it is necessary to achieve processing without models. Clustering based on position proximity of edges is one approach. However, there is concern about degrading noise reduction that has so far been done by model fitting. In this study, we developed an edge clustering method that utilizes the characteristics of edges on white-line contours; proximity of position as well as proximity of brightness gradient direction. In the proposed method, edges are first clustered based on proximity of gradient direction. And for each cluster, edges are again clustered based on proximity of position. Edge filter bank is specially designed for the first clustering and the effectiveness compared to conventional filter bank is explained. By applying the method to the images taken by on-board camera, we demonstrate that white-line detection that can apply to diverse road environments but is hardly affected by noise can be realized.
This paper presents a laser-based tracking (estimation of pose and size) of moving objects using multiple mobile robots in Global-navigation-satellite-system (GNSS)-denied environments. Each robot is equipped with a multilayer laser scanner and detects moving objects, such as people, cars, and bicycles, in its own laser-scanned images by applying an occupancy-grid-based method. It then sends measurement information related to the moving objects to a central server. The central server estimates the objects’ poses (positions and velocities) and sizes from the measurement information using Bayesian filter. In this cooperative-tracking method, the nearby robots always share their tracking information, allowing tracking of invisible or partially visible objects. To perform a reliable cooperative tracking, robots have to correctly identify their relative pose. To do so in GNSS-denied environments, the relative pose is estimated by scan matching using laser measurements captured by both sensor nodes. Such cooperative scan matching is performed by 4-points-congruent-sets (4PCS)-matching-based coarse registration and Iterative-closest-point (ICP)-based fine registration methods. The experimental results of tracking a car, a motorcycle, and a pedestrian with two robots in an outdoor GNSS-denied environment validate the proposed method.
This paper deals with the vibration quenching problem of the one-degree-of-freedom system with a limited power supply. This system is forced by centrifugal force of rotating unbalance, and the system is quenched using a Hula-Hoop and a motor to assist the rotation of Hula-Hoop. The entrainment region, the amount of vibration quenching, and the energy consumptions of the system are studied from the approximate analysis using the averaging method, the numerical integration analysis, and the experiment. Following was made clear: (1) When the unbalance is large, the entrainment region of the voltage of the assistant motor is large. On the other hand, when the unbalance is small, the entrainment region becomes narrow. (2) When the unbalance is large, by setting the voltage of the assist motor to a value smaller than the optimum value for vibration control, within the range that satisfies the allowable vibration amplitude level, the increase amount of the energy consumption becomes low. (3) The approximate solutions obtained by the averaging method are in good agreement with those obtained by the numerical integration method, and the characteristics of these results coincide with those of the results obtained by experiment.
Pneumatic anti-vibration apparatus (AVA) has been used for suppressing the vibration from the floor. Compressed air produced by the air compressor is supplied to air spring, which is used as an actuator in AVA. This paper considers the suppression of flow disturbance, which is caused by pressure variation of compressed air. Based on the internal model principle, the suppression of vibration of AVA due to flow disturbance has been confirmed by using Central Pattern Generator (CPG) in parallel with a displacement controller. In biological study, CPG in bodies playing a significant role in the walking have been learned. Moreover, mathematical models of CPG have been reported, and some researchers have been studying about walking of biped-robots by using CPG to generate desired value. On the other hand, this paper proposes asymmetric CPG as new model for further vibration suppression, compared with the symmetric CPG which is the conventional model. This new model introduces asymmetry by changing its parameters into different values in order to improve reproducibility of waveform which shows the variation of supplied air pressure. Validity of the proposed model is presented by experimental result of AVA. The effectiveness is shown by analyzing and comparing the results of experiment and simulation of symmetric and asymmetric CPGs.
The quadrotors are useful for periodic inspections of tunnels and bridges. However, the conventional quadrotor has a problem such that it is impossible to control the rotational motion and the translational motion independently. Therefore, if the camera is attached on the bottom of the quadrotor, it is difficult to observe its upward direction. In this paper, we develop a novel quadrotor that has a parallel link to tilt itself. By increasing one degree of freedom of the quadrotor, we resolve the problems described above. And we derive a model of the developed quadrotor. Then, we consider a PID controller for the stabilization of the quadrotor at a specified hovering state. We derive gain parameters of the PID controller by which the controlled quadrotor is stabilized.
A switching stiffness control and a modified variable stiffness control were applied to reduce vibration in the lateral directions in active magnetic suspension system with electromagnets operated in the differential mode. The magnetic suspension system using the attractive force between magnetized bodies is inherently unstable in the normal direction so that feedback control is necessary to achieve stable suspension. In contrast, it is usually stable in the lateral directions because of the edge effects in the magnetic circuits. However, damping in the lateral directions is poor so that vibration is easily induced. In this work, a switching stiffness control was applied to attenuate such vibration. The effectiveness of the switching stiffness control was confirmed experimentally. In addition, a modified control method that varies stiffness continuously was proposed to overcome problems occurring in switching. The efficacy of the modified control method was also confirmed experimentally.
Response spectrum analysis method is widely used for the seismic design of equipment and piping systems of nuclear power plant, or other industrial facilities. Some of the equipment and piping systems are multiply supported with plural floors, or several different points. In these cases, conservative design methods, such as uniform response spectrum (URS) method that envelopes all of the individual response spectra, or independent support motion (ISM) method are commonly accepted. These design methods are not practical, but often mislead to design with unnecessary conservatism. This paper presents the practical seismic analysis methodologies considering the correlation coefficients of seismic responses with multi-directional excitations, which is extended to apply the correlations between modal responses and between support motions, called cross-oscillator, cross-floor response spectrum by Asfura, A. and Kiureghian, A,D., and numerical examples are also presented to examine the validity for the seismic analysis method of multiply supported secondary systems, with simultaneous three directional excitations of each X, Y, Z axis.
In order to improve living space for stable walks by elderly people, this paper discussed assessment of living space with unique-shaped support objects. Four evaluation indices expressing capability of balance recovery corresponding to the support object were derived based on directionality of generative force by human's upper extremity and directionality of reaction force depending on surface shapes of the objects. Experiments were carried out to (1) obtain the parameters necessary to calculate the proposed indices and (2) carry out organoleptic evaluation of the support objects. Compared to the results obtained in these experiments (1) and (2), effects of the proposed indices were discussed, and an effective index among the four for evaluating the effect of the support objects was clarified. Assessment of a support object using the index was shown as an example.
In this paper author proposed a unique vibration suppression device that has variable inertia mass using continuously variable transmission (CVT) in order to obtain vibration isolation when a harmonic frequency was coincided with an anti-resonance frequency of 1DOF system. The device complies a ball screw mechanism, a flywheel, servo motors and CVT. The CVT is composed of toroidal wheels and power transmission wheels. The device has a small inertia force when an attitude angle of the power transmission is low by the servo motor as depending on a contact radius between two half toroidal wheels, on the other hand the large inertia force under high angle, so variable inertia force which acts as series inertia mass can be controlled continuously. The trial device was manufactured and the resisting force characteristics were measured. Theory of the variable inertia force was introduced, and compared with the experimental results. In order to confirm vibration control, an optimized inertia mass which always adjusts to anti-resonance frequency was determined in case of 1DOF system with the device, frequency response tests were carried out by using a shaking table, and experimental results were compared with calculated ones. Finally, the theory of resisting force and effects of vibration suppression were confirmed.
Several adaptive feedforward control methods have been proposed in previous research on active noise control. In those methods, noise control is achieved by adding in a reverse-phase control sound of the same amplitude to noise near an error microphone. Because this method is aimed at controlling only noise near the error microphone, the control area is inherently narrow. Here, we propose an alternative method of noise control for an entire closed space. The proposed method is based on state feedback control and modeling of the acoustic space by the concentrated-mass model. The acoustic space is modeled as masses, connecting springs, and connecting dampers. Further, a loudspeaker as control source is also modeled as a mass-spring-damper system. We previously reported a method for simple one-dimensional acoustic space control. In this paper, we show the design of a control system for two-dimensional acoustic spaces. The acoustic space and loudspeakers are modeled in a concentrated-mass model, and the state feedback control system is realized as a Kalman filter with pole placement. The number of degrees of freedom is reduced by using modal analysis, which reduces the computation time of the controller. Experiments and numerical simulation of the coupled system were conducted to confirm the validity of the analysis model. Noise in the acoustic space was experimentally controlled, with the finding that noise in the entire acoustic space was reduced around the resonance frequencies. Furthermore, the limit of the control effect are considered within the proposed system.
In this paper, formulations and some computational results of cycle jump method based on the nonlinear finite element method are presented. Problems, involving nonlinear cyclic deformation, such as low cycle fatigue problems can be solved by the proposed cycle jump method. To solve the problems of nonlinear cyclic deformation of structure by the nonlinear finite element method with a cycle-by-cycle approach, a large amount of computational time is generally required. Thus a cycle jump method is presented from a view point of temporal multi-scale analysis. Then, an alternative analytical procedure consisting of three steps is proposed. They are a few cycles of nonlinear analysis in a cycle-by-cycle fashion, computations of jumps of strain history dependent quantities (extrapolations) based on the results of the cycle-by-cycle analysis and a cycle jump for several dozen to several hundred cycles using the results of the extrapolations. The results of cycle jump analyses are presented and their accuracies are critically examined. It was found that the results of several load cycles at the beginning of each cycle-by-cycle analysis step should be excluded from the computations of the extrapolation step.
A topology optimization method is proposed for the design of shallow-flow channels based on quasi-three-dimensional flow models of laminar and turbulent flows. The models for laminar flow and turbulent flow are derived from the Navier-Stokes equations and the Reynolds-Averaged Navier-Stokes (RANS) equations, respectively, by integrating along the direction of channel thickness. The thickness is employed as the design variable in the topology optimization. The design variables are updated using a time-dependent diffusion equation with a design sensitivity which is calculated by a discrete adjoint approach. Numerical examples for minimizing dissipation energy or variance of flow velocity magnitude using the topology optimization demonstrates that the proposed method is capable of finding optimal solutions that satisfy the KKT conditions. In the former example, the design domain was clearly divided into domains where the thickness was either near the upper limit or near the lower limit. However, in the latter example, the thickness was at an intermediate level in almost the whole the design domain. The distribution of the thickness varied depending on the Reynolds number in both examples.
The product design project includes many uncertainties. It causes risk that a project target cannot be accompolished within lead time. In order to flexibly handle the uncertainty and avoid the risk, adaptive planning that can switch easily to another plan by preparing options for a task is needed. When a challenging design alternative is difficult to be accompolished, a project manager should decide either to continue the design taking a risk or to switch to a conservative alternative disliking a risk. This paper proposes a new optimization-based project planning method that aims at a Pareto-optimal of the potential technical performane of designed product and a project failure risk. A task option model is employed for risk assesment of option-based project management. As its planning includes a number of various design variables and various evaluation indices, in order to solve such a complicated problem with a reasonable computation cost, this research separates the optimization problem into two phases, i.e., (i) defining of process architecture and organization structure and (ii) scheduling of resource allocation into activities. This paper demonstrates its application to a student formula design project. A proposed optimization method facilitates a project manager to explore various process plans with assessing their risks.
In recent years, many assist devices have been developing to enable the users to walk by an electric control system. However, introducing an electric control system makes the price rise of the device. It is difficult for users to purchase an expensive device, even if it is easy to use. In order to spread an assist device in daily life, a development with a low price and a simple device is expected. The device driven by external power sources disturbs users' independent action, there is a risk that it could be make users' physiologic function decline and users disincentive to do daily actions. An appropriate control system should be constructed in order to avoid an interference between a user's motion and a device's output motion. In case that the control system has the problem, an appropriate assisting motion can not be obtained, and it is in danger of harming to the user's body. So the design of devices is needed to consider for safety. The purpose of this research is the design and the development of a simple device for assisting walking motion which is driven by users' self, considering users' own physical condition. The assist device is designed by using a planar 6-link mechanism which transforms a rotational motion into an oscillating motion. The respective lengths of the links are determined by comparing the movement of the link, which the user's foot is put on, with the movement of the human leg in the action of walking. We optimize the device by using the Genetic algorithm while we consider the max value of input-torque to drive the device. In this study, the device assisting the user's legs are driven by the user's arm. Authors evaluate the device's supporting performance by the method of measuring the leg motion and the EMG of the leg. The transmissibility is also evaluated by the method of measuring the output force with load cells. The results are verified by comparing the values derived from the static analysis. From these results, authors investigated that the driving arm motion interlocked with the assisting leg motion, even though it had only one degree-of -freedom. The measurement result of the transmissibility shows that the output is enough to support the walking motion in the swing phase.
An optimum design method for determining the cross-sectional sizes of thin steel plate columns used for steel framed house was developed to maximize their buckling strength under a constraint of constant volume using evolutionary computing and cold forming. Buckling analysis was performed by finite strip method (FSM) that can analyze the buckling loads of local, torsional, and total buckling within less computational time. Differential evolution (DE) was used for the optimization algorithm because it is a fast and reliable method for non-linear, non-convex, and multimodal optimization problems. In this research, an optimum design method is proposed, which combines DE and FSM to achieve an efficient global optimum design considering comprehensive buckling modes. This method was applied to overcome the optimum design problems of the thin steel plate columns with a lip channel cross-section. Normal axial compression capacity (Nc) of the column under a constant volume was maximized by considering design variables such as web height, flange width, and lip length of the cross-section. The search performance of the optimization method was evaluated by obtaining an objective function (1/Nc), which was calculated at the lattice points of the design variables. The optimum design point obtained by the optimization method included a global minimum point of the objective function surface, hence ensuring the validity of the proposed method. Furthermore, the optimum design problem was solved under the deformation constraint by considering connection to the wall panels for the column length of 1000 mm, 2000 mm, and 3000 mm. Optimum designs with the open profile cross-section was obtained for all the abovementioned column length. The optimum designs obtained by the proposed method can be used for practical purposes because of their open profiled cross-section and can be produced by cold forming.
This paper addresses a novel lightweight and low starting torque bearing with looped carbon fiber brush (LCFB). LCFB simulates bristle of living being. Moreover, the static friction coefficient is nearly equal to the kinetic friction coefficient. By applying LCFB to a slide bearings, where a shaft is supported by multiple LCFBs, it is realized low starting torque bearings as well as lightness compared to conventional ball bearings. In this paper, we manufacture prototype LCFB slide bearings. With the bearings, we compare friction torque between LCFB slide bearings, slide bearings and deep groove ball bearings. As results, the ratio of starting torque to regular torque of LCFB slide bearing is from 0.93 to 1.07 which is smaller than that of the slide bearing. When micro-spline shaft is used as a mating material of LCFB slide bearing, the torque reduces because of decrease of real contact area between LCFB and mating materials. In addition, since LCFB utilize elastic deformation of fibers, LCFB slide bearings are not endurable in heavy radial load as high as load rating of ball bearing. Therefore, we define the load capacity of LCFB slide bearing from buckling load of a carbon fiber bundle to avoid overload state. We propose the load capacity as a design guideline of LCFB slide bearings.
Power transmission systems using gears require both large capacity and miniaturization. As a result, the gears used in power transmission need to be strong enough to withstand high loads and high engine speeds. Because surface damage and temperature are related, it is very important to know the surface temperature of gears in operation. However, measuring the surface temperature of gears in operation is difficult. As an effective means to measure the surface temperature, method of using dissimilar metals is known. The voltage proportional to surface temperature was produced by contacting dissimilar metals. This is known as Seebeck effect. The authors tried to use two simple ferrous metals. In this study, S55C (Carbon steel) and SUS316 (Stainless steel) were selected to dissimilar metals. Both dissimilar metals were heat-treated and surfaces were hardened. SUS316 was performed plasma carburizing process and S55C was performed induction hardening. As for the gear, it is known that the two or more teeth will mesh simultaneously. In order to remove the influence of the number of tooth in operation, the gear of two sheets were made into the one structure meshed by turns (combined lacked gear). When making the gear of two sheets into one structure meshed by turns. The experiments were operated on maximum condition of contact pressure 1.47GPa in a pitch point. As a result, surface temperature measured almost successfully by combined lacked gear by SUS316 plasma carburizing process and S55C induction hardening. When we compared the experimental values and the theoretical values using Blok's formula, surface temperatures on gear teeth values were largely same.
Non-contact supports involving air or magnetic forces are used as guide supports for linear motion mechanisms. In the present study, non-contact supports are generated using the effect of the static pressure force produced by a squeezed air film. The linear slider is supported at just two of its ends. Applying a different excitation amplitude to the two transducers leads to a difference in the floating height at either end of the slider due to the different air-film thicknesses. This causes the slider to tilt, which produces a propulsion force due to the dead load. An experimental apparatus with a flat plate slider was developed and its floating characteristics were examined. In addition, the propulsion force was measured for sliders with different weights. The results indicated that the floating height was 2 to 3 times the excitation amplitude. The slider was capable of travelling all over the movement stroke. The traveling force increased with increasing slider weight, and was about 0.15-0.35 mN. The measurement results were in good agreement with theoretical calculations. Thus, the present study showed that the slider could be successfully supported in a non-contact state and was capable of movement under the influence of a propulsion force generated only by the dead load.
Separation technique of the circulating tumor cell (CTC), which would be a sample for diagnostics of cancer, is important. In the present study, a micro flow device, which has gaps between micro-cylinders, has been fabricated by photolithography technique to distinguish between cancer cells and red blood cells. Two kinds of cells were used in the test: Hepa1-6 and swine red blood cell. The mean diameters of two kinds of cells measured by ImageJ were 21 μm and 6 μm. Variation was made on the dimension of the gap: 10, 15, 20 and 25 μm. The micro cylindrical pattern was fabricated on the slide glass with a photomask of titanium film. The negative resist material (SU-8) was coated on the glass plate to make the 60 μm height of the micro cylindrical pattern. A micro flow channel was made between the glass plate with the micro cylindrical pattern and the flat polydimethylsiloxane (PDMS) disk. Swine blood was diluted 100 times by the saline solution. The concentration of Hepa1-6 was adjusted to 5000 cells/ml by the physiological saline solution or by the swine blood. The cell suspension of 30 μl was injected into the channel by a micropipette, and the trap rate at the gap of the micro pattern was measured. The experimental result shows that trap rates of micro cylindrical pattern gap of 10, 15, 20 and 25 μm are 100, 80, 37 and 26%, respectively. Most of the swine red blood cells can pass through the 10 μm gap. The result shows that the microchannel device developed in the present study is effective for the separation of the CTC.
Control technique of orientation of a biological cell is expected to be applied to tissue engineering. It is known that morphology of the scaffold affects the cell behavior. For example, the micro stripe pattern can control cell orientation. The effect of aspect ratio of the micro checkered pattern on cell orientation has been investigated in the present study. The dimension of each unit of the micro checkered pattern is as follows: the length is 10 μm, and the height is 0.7 μm. Variation has been made on the width of the micro pattern: 5 μm (A), 8 μm (B) and 10 μm (C). Each type of repeated micro pattern was formed in the square area of 500 μm × 500 μm. The micro pattern was made of the negative photoresist material (SU-8 2) coated on a glass plate by the photolithography technique. C2C12 (mouse myoblast cell) was cultured for 24 hours on the micro pattern. The angle between the longitudinal axis of each cell and the width of the micro pattern was measured on the microscopic image. In each pattern, the average angle was as follows: 62.8 degrees on A, 50.2 degrees on B and 41.2 degrees on C. The experimental results show that the aspect ratio of micro checkered pattern controls cell orientation.