Machine equipment usually comprises many mechanical elements that can fail because of functional deterioration and friction. For tribo-elements like plane bearings, it is extremely important to diagnose the abnormal conditions and prevent such parts from breakdown caused by wear. However, diagnosing tribo-elements requires expensive diagnostic equipment and expertise. This study aims to propose a cost- and time- effective system that detect the signs of breakdown during equipment operation by using machine learning to identify abnormalities. We conducted wear tests in contaminated oil and used multiple sensors to collect data regarding the friction force, the electrical contact resistance, the acoustic emission (AE) signal, and vibration. An appropriate learning sample was selected using k-fold cross-validation. The electrical contact resistance was found to contribute relatively little to the detection of abnormalities, whereas the friction coefficient contributed greatly. Furthermore, the AE signal and the vibration detected local changes on the sliding surface. Consequently, we found that machine learning can judge whether monitoring data are normal or abnormal.
Hardness representation in VR is one of the important problems to create virtual touch feeling as if the feeling is caused by real touch. In this study, we are attempting to improve the hardness representation method by combining the pseudo-haptics and tactile stimuli, which was presented in our previous research. In the current study, we investigated the ability of both of these methods to express tactile hardness stimulation: in Experiment A hardness was generated solely by visual stimulation using CG; and in Experiment B hardness was generated solely by the dot-matrix display. Based on the results of Experiments A and B, in Experiment C we conducted psychophysical experiments on the ability to express tactile hardness by combining the effects of pseudo-haptics and the tactile stimuli. In Experiment C, we were able to express six levels of distinguishable hardness, while only four and two levels were observed in Experiments A and B, respectively. In addition, the relationship between hardness evaluation and the six levels shows high linearity with R2 = 0.98.
Along with the extreme aging of the population in Japan, the number of elderly with dementia has been increasing. Measures to address their symptoms and suppress the onset of dementia have been demanded. Currently, treatments such as nursing care, medication, and psychological care are adopted. Psychological care includes reminiscence therapy, reality orientation, music therapy, and animal therapy. It is reported that animal therapy can be effective for those who are hard to deal with and have difficulty communicating, such as the elderly with severe dementia, those who tend to refuse general recreation and care, and those who are unresponsive and impassive and act purposelessly. However, having pets is sometimes difficult in hospitals or elderly-care facilities because of the necessity of caring for pets and possible problems such as allergic reactions, infectious diseases, and biting and clawing by pets. Therefore, animal therapy has generally not been popular. Under such circumstances, pet-robot therapy, instead of animal therapy, has been attracting attention. Research on cat-shaped, dog-shaped, and seal-shaped robots has been actively carried out. However, users cannot feel intimacy, joy, or peace with these pet robots over a long time, and robots fail to give a sense of comfort to users, which is a current problem with pet robots that should be solved. In this study, considering the problems of animal therapy, we propose pet robots that can be used in reminiscence therapy, which is reported to be effective for the alleviation and suppression of the symptoms of dementia, and we examine the shape and functions required of the pet robots.
Recently, there are increasing concerns about the evaluation of vehicles’ safety that frequently refers exclusively to the primary collision during an accident, while neglecting often involved subsequent collisions. Despite theoretical approaches to secondary collisions had already been proposed, they lack sufficient experimental verification as a vehicle’s post-collision motion appears largely unpredictable. The present study avoids the indicated drawbacks and addresses collision experiments performed for various impact positions and wheel rotation of a selected vehicle model. The results are obtained for various conditions, while the essential motion trajectory of struck vehicle is determined based on the movement of the vehicle center of gravity and rotation angle. The monitored translational and angular velocity of ‘struck vehicle’ confirms our claim that the impact position significantly affects primary and secondary impact rotation and moving distance of the vehicle involved in an accident. In sum, we present the accuracy and application range of the automobile motion theory to be validated while based on experimental data.
The cylindrical rubber is axially reinforced by the fiber and closed by the rigid ends. When the inner pressure is applied to this fiber reinforced rubber cylinder, the diameter expands and the length shrinks. Such the cylinder can be used as the soft actuator, that is, the artificial muscle. In this paper, this problem is analyzed theoretically. Firstly, the differential equation, which is satisfied the cylinder's profile, is derived. Secondary, the solution is obtained as the closed form, when the rubber is soft enough compared to the fiber. Finally, it is found that the profile of the rubber cylinder is given by the incomplete elliptic integral, when the inner pressure is large enough. Moreover, the spring constant, the contraction ratio and the maximum stress are obtained with respect to the length of the cylinder. The spring constant is linearly increasing with the inclement of the initial length of the cylinder. The contraction ratio is increasing with the inclement of the initial length of the cylinder and converged to 54.3%. The maximum stress is related to the elastic modulus of the rubber and is not related to the inner pressure. When the length of the cylinder is through three to five times larger than the initial diameter of the cylinder, the rubber has the small maximum stress and the large contraction ratio.
In order to realize deep laser welding, conceptual application of a supersonic jet as an aerodynamic window was investigated. Detailed characteristics of the supersonic jet as the aerodynamic window were studied experimentally. Flow field of the supersonic jet was examined based on the schlieren flow visualization technique. As compared to a free-vortex flow design applied to the aerodynamic window nozzle, in the case of supersonic jet, oblique shock waves were captured both at the nozzle exit edge and the shear layer on the aerodynamic window. The velocity field under the condition that the shock - expansion wave was formed in the aerodynamic window was measured by the PIV (Particle Image Velocimetry) system (Koncerto II, Seika Digital Image Corp.) . Both the vorticity magnitude and angular momentum were analyzed. Level of the vorticity magnitude in the core region of the supersonic jet was smaller by one-order than that in the shear layer in the region corresponding to the passage of laser-light (θ = 30 to 40° and r = 23.8 to 27.1 mm). The radial and circumferential velocity product in this region was similar to that observed under the free-vortex condition. In addition to the measurement mentioned above, pressure behavior was investigated using a multi-pressure measuring system (Scanivalve Corp. ZOC33). When the reservoir pressure was set at 800 kPa and diffuser width as 30.0mm, cavity pressure was reduced to 10.0 kPa. Under this reduced pressure environment, penetration depth increased by 2.6 times compared to penetration depth under atmospheric pressure environment. The effectiveness of the supersonic free-vortex aerodynamic window system tested in the high power laser welding manufacturing has been proven by the present study.
We have addressed a suspension composed of magnetic cubic particles, which have a magnetic dipole moment at the particle center magnetized along the diagonal direction of the cube, in order to elucidate the physical phenomenon of the attachment characteristics and the aggregation structure of these particles, by means of Monte Carlo simulations. The cubic particles are negatively charged and confined between the two parallel walls one of which is positively charged (i.e., electrode) and the other is connected to the ground. The main results obtained here are summarized as follows. In the case of no external magnetic field, if the magnetic interaction is sufficiently strong for the formation of stable chain-like clusters, then longer chain-like clusters are formed between the two parallel walls and these clusters are more significantly located along the surface of the electrode as the electric interaction strength is increased. In the case of the electric particle-wall interaction being stronger than the magnetic interaction, almost all constituent cubic particles of chain-like clusters more significantly attach to the surface of the electrode in a face-to-face contact manner between the face of the cube and the wall. To the contrary, if the magnetic interaction is stronger than the electric interaction, the chain-like clusters are formed in the space of the two parallel walls from the end particle attached to the electrode wall. In the case of an external magnetic field applied along the surface of the electrode wall, the chain-like clusters are formed and extended from the surface to the space of the two parallel walls with the end of the particle of the clusters attached to the electrode wall.
In the previous study, we investigated the adsorption phenomenon where the adsorption agent or spherical particles adsorb turbidity-causing (TC) particles in the sedimentation process in the gravitational field by means of Brownian dynamics simulations. These results may certainly contribute to the development of a technology for improving the visibility in small lakes and ponds. We here extend the previous study to an adsorption agent of non-spherical particles where the particle rotational Brownian motion is significantly expected to contribute to the adsorption performance in addition to the translational Brownian motion. Hence, we have employed the modelling of adsorption particles as large spherocylinder particles and TC particles as small spherical particles with a sub-micron size in order to perform Brownian dynamics simulations. For the case of a large aspect ratio rp =15, in the situation that the particle volumetric fraction is constant, the adsorption rate is much better than spherical particles by 75% improvement, and therefore it is seen that the rotational Brownian motion of the rod-like particles gives rise to a much more significant adsorption performance. From these results, we understand that the use of rod-like particles with a large aspect ratio as adsorption agents can adsorb TC substances much more efficiently in comparison with spherical particles.
The power loss due to the friction and the leakage in the sliding part between piston and cylinder of a swash plate type piston pump and motor affects the equipment performance and the efficiency. The friction and the leakage in the sliding part depend on the motion of the piston which relates to the lubrication characteristics. In this paper, for each straight cylindrical piston, forward and reverse tapered pistons, the motion of the piston under mixed lubrication has been numerically calculated, each power loss due to the friction and the leakage has been estimated based on the result, and the effect of geometric shape of the piston on the power loss of the equipment has been investigated. The results are summarized as follows: (1) The effective taper angle exists from the viewpoint of the friction power loss and minimization of total power loss, and the reduction rate of both power losses is closely related to the modified Sommerfeld number Sm with constituent parameters such as equipment operating conditions and design conditions. (2) The total power loss reduces when adopting the reverse tapered piston with an optimum taper angle for the pump and the motor, but it increases by adopting the forward tapered piston. (3) The reduction rate of the friction power loss for the pump is high in the region where the Sm value is small in the forward tapered piston and in the region where the Sm value is large in the reverse tapered piston. (4) The power loss due to the leakage of the pump and the motor decreases when adopting the reverse tapered piston, but increases in the case of adopting the forward tapered piston.
A new locally operated unilateral master-slave manipulator for endoscopic surgery performed by a surgeon in a sterilized area was developed. The manipulator system consists of a portable master device and a forceps slave manipulator (revised parallel-linkage mobile LODEM) as the third arm. We propose the mechanically separable portable device which can be set anywhere beside the operating table. The master device consists of a portable mechanical part that can be autoclave sterilized and an encoder sensor part connected to driving wires covered with a coiled steel flexible cable tube. The five-DOFs master devices use a magnetic ball joint and gimbals for the pitch and yaw axes, a linear guide for the insertion axis, a circular dial for the roll axis, and a handle for the grasp axis. The dimensions of the mechanical component are 130 mm × 130 mm × 350 mm, and its mass is 1.0 kg. The operating ranges for these axes are ±70 °, ±70 °, 100 mm, ±180 °, and 40 °, respectively. The mechanical backlash is 0.8 ° to 4.9 ° for the pitch and yaw axes, and 0.6 mm to 2.6 mm for the insertion axis. The modified mobile LODEM, which is used as the slave manipulator, is unilateral master-slave controlled by the master device. The master-slave manipulator was confirmed for the pitch, the yaw, the insertion, and the roll axes when the velocities are 15 °/s, 15 °/s, 50 mm/s, and 1080 °/s, respectively. Simulated laparoscopic cholecystectomy was performed on a surgically realistic model in a training box by an endoscope specialist. The forceps slave manipulator was driven under the surgeon’s master-slave control using the portable master device. The experimental results indicate that 5 mm backlash at the handle of master device is not large for the master-slave manipulator as the assistant. The results of the present study suggest that the proposed system could be used for robotically assisted laparoscopic surgery by a surgeon working near the patient.
In general braking control methods of adaptive cruise control, control input is decided based on relative distance and velocity between the preceding vehicle and the ego vehicle at the moment. Such an approach is affected by acceleration/deceleration of the preceding vehicle directly. Therefore, there is a possibility that the response of the ego vehicle becomes oscillatory, and ride comfort gets worse. In this paper, a braking control method based on driver's characteristics is proposed in order to perform adaptive cruise control considering not only safety but also ride comfort. We construct a system with following ways. First, driver's characteristics are extracted from driving data of an expert driver. The following results were obtained: the human braking behavior is divide into three parts, and it does not depend on vehicle velocity of the ego vehicle and the preceding vehicle. Second, the generation method of reference values for braking control is proposed with extracted characteristics. We consider regeneration of reference values when the preceding vehicle accelerates or decelerates during braking of the ego vehicle. Finally, a longitudinal control method is proposed, and the stability of the system is proved. From results of a simulation and an actual vehicle experiment, it was found that our method can reproduce an expert driver's braking behavior.
The aim of this study is to develop a systematic method to suppress residual vibration in overhead cranes that lowers operating performance and prevents automation of the system. In the previous paper, we proposed a control method which is based on the fact that residual vibration is completely suppressed in a linear undamped system excited by an external force that does not contain the natural frequency component of the system. The proposed method introduces the concept of the apparent external force which includes the influence of nonlinearity and damping, making it applicable to nonlinear damped systems as well as linear undamped ones. One possible drawback is that it needs the value of the natural frequency of a cargo whose on-site high-precision estimation is generally difficult. Therefore, this paper investigates the influence of the estimation error on the residual vibration, which reveals that the residual vibration increases with the estimation error. To improve the robustness against the estimation error, we employ two types of ways. One is to increase the number of frequency components eliminated from the apparent external force and the other is to make the derivatives of the frequency component zero at the estimated natural frequency. Numerical simulations demonstrate the effectiveness of these approaches, showing that they exhibit similar performance in robustness except in that the latter is easier to use since it does not need additional parameters to be determined.
In a previous report, the author presented a motion analysis method for rigid multibody systems, called nullspace matrix method of differential equation type. The method determines the nullspace matrix by solving a differential equation with respect to the nullspace matrix, while many other methods which use the nullspace matrix determine it algebraically. Due to this the presented method can obtain the nullspace matrix for systems with redundant constraints or continue the computation when the systems pass through the singular configurations by using relatively large value of stabilization parameters. The presented method uses the QR decomposition whose computational cost is moderately high. In addition, when the system passes through the singular configurations, the accuracy and stability of the presented method decreases since the differential equation for the nullspace matrix becomes incomplete. This paper improves the method in the previous report in the aspects of the computational efficiency and treatment of the singular configurations. The validity of the improved method is verified by numerical examples.
This paper considers the positive real property of the impedance matching controller for double cascade-connected damped mass-spring systems, whose mass is connected to beyond the adjacent masses. The system can be regarded as a linearized model of a tensegrity beam, one of the basic structures in tensegrity systems corresponding to a cantilevered beam in continuum case. In our previous work, we considered wave analysis and control of the systems, and showed that the impedance matching controller is effective for vibration suppression of the tensegrity beam. However, in the paper, analytical property of the impedance matching controller, i.e., positive real property, was not investigated; and thus the closed loop stability is not guaranteed from the theoretical point of view. This paper addresses this issue, and shows that the impedance matching controller is actually a positive real function.
For designing sensors, it is very important to know the mechanical strength of constituent thin film materials. Although material strength is generally measured by tensile experiment, it is difficult to apply it to thin films. In this work, we developed a new method which can easily evaluate the fracture strength of thin film. In the method, first, silicon nitride and silicon oxide are alternatively deposited on a silicon substrate. Then, a target thin film is deposited on the top surface of the specimen and the silicon substrate of the back side is removed to form a diaphragm at the central region. Since the substrate around the diaphragm is thick, the specimen can be easily handled without fracture. The multilayered diaphragm realizes to break the target film by tensile deformation. After an air pressure is applied to the top surface of specimen until the diaphragm is broken, the fracture strength of the target film is obtained by stress analysis based on the experiment results. Adapting this method to a titanium thin film of 230 nm thickness, the fracture strength was evaluated to be 2.3 ± 0.2 GPa.
This paper presents a numerical solution to shape identification problems on internal flow and external flow in unsteady viscous flow fields. In the internal flow problem, shape design problem that controlled the flow velocity distribution in the sub-domains of the unsteady viscous flow field was introduced. The square integration error between the actual flow velocity distribution and the target flow velocity distribution in the specified sub-domains was employed as the objective functional for the shape design. In the external flow problem, drag control problem for an isolated body located in uniform flow was formulated in the domain of unsteady viscous flow fields. The shape gradient of these shape identification problems were derived theoretically using the adjoint method, the Lagrange multiplier method and the formulae of the material derivative. Reshaping was accomplished using the traction method that was proposed as a solution to domain optimization problems. Numerical analysis programs for the shape identification problems were developed based on FreeFem++, and the validity of the proposed method was confirmed by the results of 2D numerical analyses.
In this study, we propose a parameter-free optimization method to control time-dependent responses of a shell structure, where the optimal thickness distribution is determined without design parameterization. The design objective is to minimize the vibration displacements or to control the dynamic responses at arbitrary domains and times for an arbitrary time-dependent loading under the volume constraint. The unsteady optimum design problems are formulated as distributed-parameter optimization problems and the sensitivity functions with respect to the thickness variation are derived based on the variational method, Lagrange multiplier method and the adjoint variable method. The derived sensitivity function is applied to the H1 gradient method with Poisson's equation, a gradient method in the function space newly proposed in this study to determine the optimal variation of the thickness distribution. With the proposed method, the optimal thickness distribution for time-dependent response problems such as a forced-vibration, a free-vibration or a transient response is obtained while minimizing the objective functional and maintaining the smooth thickness distribution of a shell structure. Several numerical design examples including a continuous dynamic force or an impulse force as an input force are demonstrated to show the effectiveness of the proposed method, and the results are discussed.
To diagnose hill-top branching and multiple bifurcation, which exhibit two critical eigenvalues of the tangent stiffness matrix in stability problems, a sophisticated computational asymptotic bifurcation theory is developed. The theory generally uses three modes which are composed of two homogeneous solutions (critical eigenvectors) and one particular solution of the singular stiffness equations. The first- and second-order derivatives of the stiffness matrix with respect to nodal degrees-of-freedom (DoF) are required to formulate the proposed computational asymptotic bifurcation theory. In two benchmark problems of hill-top branching and multiple bifurcation, the validation and performance of the proposed theory are discussed.
White etching area may be recoginized at the flaking part of a rolling bearing on which high contact stress of several GPa is applied repeatedly. Up to now, there have been less studies of the white etching area of a ball than that of inner and outer rings. In this study, as part of the flaking mechanism explication of white etching area in a ball of deep groove ball bearing, the form, the structure and chemical composition of white etching area were investigated. The form of the white etching area of a ball is mostly identical to the form of the white etching area of the inner ring and the outer ring. The white etching area of the ball is formed from the ferrite grains of tens of nm and is mostly identical to the white etching area of inner and outer rings. The carbon density of white etching area is higher than the carbon density of the matrix, and much carbon exists at the grain boundary of the ferrite grains of tens of nm.These results of carbon are mostly identical to the results of the carbon of the white etching area of cylindrical roller thrust bearing races.
In Japan, the Law Concerning the Rational Use of Energy (Energy Saving Law) has been revised to regulate the annual average of specific energy consumption at 1%. In December 2015, the United Nations Climate Change Conference (COP21) culminated in the Paris Agreement, which demanded global efforts to reduce greenhouse gas emissions. To solve these problems, industries have been becoming more important to evaluate and reduce energy consumption when designing, operating, and improving manufacturing systems. Therefore production management methods concurrently considering productivity and energy consumption are needed. Recently, production facilities which have an energy-saving idle state such as machining’s and industrial robots have been proposed and begin to be introduced. These facilities have two types of idle state such as an energy-saving idle state and a normal idle state. In the normal idle state, the facilities are possible to immediately start up to produce. In the energy-saving idle state, the facilities need a period to start to produce. Within keeping the energy-saving idle state, the amount of the energy consumption becomes a low level because auxiliary machines that support the facility behaviors are temporally stopped. However production management methods in a production line such as a decision support in each facility to operate the normal state to the energy-saving idle state does not propose. In this research, we propose a decision support method to operate production facility with the energy-saving idle state in production lines. We carried out a case study that is a production line which consists of three facilities.
This report describes the study on the lubrication characteristics of porous journal bearings as a DC spindle motor's bearing system made with oil impregnated sintered materials having some hydrodynamic shapes. Herring Bone (I & II), Three Lobed Type or Sleeve as radial hydrodynamic shapes were proposed, and four kinds of specimens were produced for porous journal bearings with pivot supported conditions. They were examined experimentally to optimize the hydrodynamic shape of porous journal bearings by measuring the lubrication characteristics at the shaft starting state under sine-wave vibrated conditions. This report particularly refers to the experimental examination for Settling Time, Lissajous Curve Diagram or Shaft Whirling by measuring the Time History Waveform (T.H.W.) of the shaft such as the above mentioned lubrication characteristics under the same conditions. Furthermore, it was investigated to discuss the influences of vibrated frequency changes to the lubrication characteristics by measuring the T.H.W. of the shaft under the above conditions.
High strength steel (HSS) have several advantages such as lightweight and high shock absorption. In sheet metal forming of HSS, twist springback occurs remarkably, which results in the low product quality. In addition, major defects such as wrinkling and tearing easily occur due to the low formability. Blank holder force (BHF) and blank shape have a direct influence on the twist springback, the wrinkling and the tearing. Variable BHF (VBHF) that the BHF varies through the stroke is valid for the twist springback reduction. In this paper, we propose a novel method to evaluate the twist springback, in which both the torsion angle of top of the product surface and the angle of left/light flange are evaluated. Based on the evaluation, a design optimization to determine the VBHF trajectory and blank shape is performed under several design constraints. The numerical simulation is so intensive that a sequential approximate optimization using radial basis function network is adopted to determine the optimal VBHF trajectory and the blank shape. Thorough the numerical simulation, the validity of proposed approach is examined.
This paper presents a discrimination method of Sleep Apnea Syndrome (SAS) and early detection of potential Sleep Apnea Syndrome (Pre-SAS) using sleep breath sound, by which each subject can take the required data for the diagnosis at home only with a voice recorder. Sleep breath sound of around two hours is analyzed statistically for detecting SAS patients. Long silence sections in the sleep breath sound and the biggest sound pressure typically occurred after them are compared for distinguishing Pre-SAS, SAS patients and non-patients. The k-means method is applied for classifying the above sound data. The proposed method drastically reduces the time and effort required for SAS diagnosis compared to the current medical approaches. Experimental results show the effectiveness of the proposed method, by which 100 % accuracy of discrimination is achieved.
Vascular smooth muscle cells (VSMCs), one of the main components of arterial walls, actively remodel arterial wall in which they reside through biomechanical signals applied to themselves. The contractile or differentiated VSMCs were observed in normal blood vessels. In pathological vascular conditions, they dedifferentiated from contractile to a non-contractile or synthetic cells, and a similar change is observed when VSMCs are placed in culture conditions. The mechanisms regulating VSMC differentiation remain unclear at this stage. Here we investigated the effects of substrate stiffness on the morphology, intercellular tension, and differentiation of VSMCs. Rat VSMCs were cultured on the polyacrylamide gels, whose elastic modulus was 15 kPa, 40 kPa, and 85 kPa. Using fluorescent microscopy image-based analysis, and nano-indentation imaging with atomic force microscopy, we found that cell spreading and cell stiffening was induced by substrate stiffening in VSMCs. Interestingly, VSMCs on the substrates with middle stiffness (40 kPa) showed significant elongation and shape polarization, and their expression ratio of α-SMA with F-actin cytoskeleton was significantly higher than that of the cells on the other substrates. These results indicate that there exists an optimal substrate stiffness to promote VSMC differentiation, and cell shape polarization might be a key factor for VSMC differentiation.
Moving-object tracking (estimating position and velocity of moving objects) is a key technology for autonomous driving systems and driving assistance systems in mobile robotics and vehicle automation domains. To predict and avoid collisions, the tracking system has to identify objects as accurately as possible. This paper presents a method for recognizing vehicles (cars and bicyclists) and people using a 64-layer ground laser scanner. When laser-scanned data are captured by the laser scanner, laser-measurement points related to objects are extracted by the background subtraction method and are clustered. Eight-dimensional features are extracted from each of clustered laser-scanned data, such as distance from the laser scanner, velocity, object size, number of laser-measurement points, and distribution of the reflection intensities. The machine learning methods (support vector machine (SVM) and random forests (RF)) are applied to classify cars, bicyclists, and people from these features. The experimental results using “The Stanford Track Collection” data set show that the classification accuracy using the SVM-based method is higher than the RF-based method. In addition, they show that the use of the proposed eight-dimensional features provides better classification accuracy and shorter processing time than the use of the conventional 26-dimensional features.
Some of the steering vibrations as the road information are useful signals for the drivers to acquire road conditions. This paper examined the relations of steering vibration and the road information by using a steering simulator. The actual steering vibration and random excitations were used for this study. It was investigated which frequency components of the actual steering vibration were necessary as the road information. Furthermore, the road information and solid feel of the steering system were investigated by changing the spectrum of balance and the vibration of the frequency of random excitations. Drivers recognized the frequency under about 4 Hz as unnecessary vibration of steering pull, and the frequency over 100 Hz as unnecessary vibration of itch feeling. When the steering amplitude of vibration was in a relation of 10 dB/dec. for a frequency, the drivers recognized the road information wealthily and steering stiffness.
It is necessary for pantographs of Japanese high-speed trains to satisfy both low noise characteristics and insensitive lift force characteristics toward the variation in wind direction and in the shape of pantograph head due to wear. Taking particular note of the profile of the pantograph head, streamline-wise profile generally leads to low noise but sensitive lift force characteristics, and rectangular profile leads to less sensitive lift force characteristics but generates larger noise. It is therefore difficult to achieve the two characteristics at the same time in a passive way. The authors propose a solution for this trade-off by applying the pantograph equipped with smoothed profile pantograph head, which gives better performance in terms of aerodynamic noise, and actuator to actively control the lift force. One of the most difficult problem to employ active control techniques on a pantograph is the measurement of its lift force. This paper proposes a method for lift coefficient estimation with realistic measurement points. The basic idea of this method is measurement of the surface pressure on the pantograph head with the use of static holes. By applying LASSO regression which is known as one of the sparse modelling technique, only 5 static holes enables to estimate the lift force with sufficient accuracy just as the lift force estimated by using 34 static holes data. This means that the proposed method allows us to materialize a simpler measurement system.
In order to establish a construction method for a large space structure of several hundred meters or more required by the Space Solar Power Systems (SSPS), it is necessary to carry out a long series of experiments on orbit while gradually expanding the structure size because the current technology level to realize the large space structure is low. If we can carry out the experiments as space use missions like telecommunication, earth observation and so on, we can increase the possibility to carry out the experiments because the cost-effectiveness of the experiments is improved. Therefore, we aim to establish a construction method for a 30-m-class large planar antenna required by a radar to observe precipitation from a geostationary orbit as the immediate target. In order to establish the 30-m-class large planar antenna construction method with high feasibility and expandability for the SSPS, we proposed a method to deploy and connect antenna panel rows one after the other. And we verified feasibility for critical functions of large planar antenna deployment and connection mechanisms used in the proposed method by two step ground experiments. First, we carried out the experiment for the Electromagnet Connection Mechanism (ECM) which is the key device of the antenna deployment and connection mechanisms and confirmed that the basic function concept of the ECM can be realized. Next, we carried out the deployment experiment for panel rows equipped with the ECM and demonstrated the deployment and connection function concept of second and subsequent row panels because these functions are the critical functions.