This paper proposes the online learning controller for PID gain tuning to regulate the speed of robot on parallel two-wheeled electric scooter. We define this speed regulation as “speed governing behavior”. The proposed system based on Iterative Feedback Tuning (IFT) contributes the online continuity during learning control not to interrupt and reset/restart the controller. PID gain update during control has the problem that the integral gain change affects the divergence of control input. To this problem, we propose the digital integrator which modifies the previous integrated value of control error. This proposed integrator solves the impulsive control input without any anti-windup or reference shaping. In conclusion, this paper shows the experimental results based on the online learning control and demonstrates the speed governing behavior by life-sized humanoid robot. We finally aim the driving of parallel two-wheeled electric scooter by speed control of humanoid robot.
Some organisms using undulatory locomotion show the transition of the swimming frequency and the wavelength of the undulation. This transition of swimming behavior is achieved by sensory feedback, and may have the role to cope with the environmental change. Especially, one of the nematode: Caenorhabditis elegans can modulate its frequency from approximately 0.3 to 2 Hz, and vary the wavelength of undulating body from less than a single body length to almost twice the body length. With this modulation, C. elegans achieves the movement under the conditions from in water to on the surface of an agar. Inspired by this finding, we propose the adaptive control for the multilink swimming robot because the environmental change demands a mobile robot the change of the pattern of the locomotion. Proposed adaptive control employs the sensory feedback from joint angles to inputs of actuators at joints to generate the self-excited oscillation. At first, we construct the multilink model in fluid with sensory feedback. After that, we construct the linearized model to obtain the relationship among the external resistive force, parameters of the multilink model and the swimming frequency by using the eigenvalue analysis. We confirm whether the proposed adaptive control simulates the modulation of undulation like C. elegans. Moreover, we specify parameters of the multilink model which are related to the frequency and wavelength of undulation significantly.
In this study, we measured and analyzed the degree of posture discomfort with respect to the coordinated range of motion (ROM) of the thumb. For ergonomic assessment of a product CAD model using a digital hand model, such joint properties are necessary to be clarified when estimating possible natural postures to use the product. We concentrated on the thumb, which plays an important part to form various grasps by opposition. To model range of motion considering coordination among joint variables, each subject's hand during a given set of exercises was captured by an optical mocap system. A posture of the carpometacarpal (CM) joint of the thumb was expressed with spherical coordinates to integrate different subjects' ROM easily. The result was shown some characteristics of the thumb such as coordination among joint variables or collision between thumb and other parts of the hand. The posture discomfort data was collected through the experiments for four adults with healthy hand. To control variety of the postures, each subject was asked to reproduce about 45 displayed postures and to answer whether the subject felt discomfort or not in terms of keeping that posture for 10 seconds. The discomfort experiment results were combined into a discomfort possibility map with respect to joint postures. This map can assist product design, for example considering interface layout.
This paper proposes a method to compute positioning error of a parallel mechanism having passive spherical joints with clearances in motion without numerical integration nor iterative calculation. A model of passive spherical joints, in which the relationship between the relative displacement between the joint elements and the joint force obtained without taking the clearance into consideration is defined, is presented. Based on this model and the principle of virtual work, a procedure to calculate the output position error caused by joint clearance is proposed. Experiments for a DELTA parallel robot with joint clearances were conducted to evaluate the effectiveness of the proposed method comparing the measured output position error with the computational results. The applicability of the proposed method was discussed with a time variable for the relative displacement of the joint elements to converge, when the joint reaction force changes, defined as stabilization time. An index, representing an approximation of the stabilization time, was defined under consideration of rebounding and sliding motions between joint elements. The validity of the index was confirmed by investigating the correspondence between calculated index and the stabilization time obtained with experiments when changing the acceleration of the robot.
This paper presents a method of data reduction for long-term robotic mapping using a 2D laser scanner. The proposedmethodintroducesobservationfrequencyintotheoccupancygridmap, andcalculatestheimportance of each scan through the ray-casting algorithm. The importance of a scan is high if the scan observes many occupancy cells which are new in terms of the observation frequency. Also, the method calculates the coverage of a subset of scans to examine how the subset covers the map well. Then, the method determines the threshold of the scan importance according to the designated coverage, and removes the scans which are less important than the threshold. The reduced laser scans improve computation time and memory consumption for pose adjustment and map reconstruction in loop closure. Experiments using real-world data show the proposed method effectively reduces data size and computation time in robotic mapping.
People adjust their gait by interacting with the surrounding environment. Thus, hidden factors in the environment such as fall risk that influence the gait can be exposed by measuring its change during daily walking. For this purpose, in this paper, we employed wearable IMU sensors that enables measurement of stride length and stride time of the pedestrian without environment fixed MoCap system. We also used the GPS receiver for measuring the global position of the pedestrian simultaneously, since the IMU sensors only offer a local change of the gait. The change of the stride length and the stride time were calculated from the IMU sensors and mapped onto the geographic map referring to the GPS data for constructing the Geographical Information System (GIS) of the gait. These gait indices changed according to the type of the walkway, plane, stair, and slope. Also, even in the same walkway, the indices changed by the environmental factors such as obstacles, walking direction and traffic light. The experimental results suggest that measurement of the gait during daily walking in the daily environment seemed to have the potential to expose the factors hidden in the environment such as the fall risk that influence the gait.
The purpose of this study is to develop a walking assist device by controlling trunk and pelvis motion. Human gait motion consists of whole body exercise including lower body motion and upper one. As all exercises are performed normally, walking with less energy loss is performed. If any exercises are incomplete, compensatory motion is performed and it is considered that there is energy loss. Therefore, this study aims at developing the walking assist device to make normal exercises and reduces energy loss by applying external forces, focusing on the trunk rotation and the pelvic rotation that involved in stride length and walking speed.
A synthetic fiber rope, which is lightweight and has a high tensile strength and flexibility, is receiving much attention as a replacement for a stainless steel wire rope. To exploit the maximum tensile strength of the rope, it is essential to develop a terminal fixation method with the sufficient fixing force. However, practical difficulty exists in the case of the synthetic fiber ropes because the synthetic fiber ropes have very small frictional coefficients compared with a stainless wire rope. This paper proposes a new terminal fixation method using a grooved pulley, a loop with figure-eight knot, and a pin. The grooved pulley is introduced to increase the friction between the synthetic fiber rope and the pulley by wedge effect, and the rope is wound around the grooved pulley. The end of the rope is hanged at a pin by a loop with a figure-eight knot. We experimentally derived the appropriate groove shape, and demonstrated that our method permits the maximum fixation force over 90 % of the rope breaking force. An example of implementation for a prototype model of a coupled-tendon multi-joints manipulator is also described.
In this paper, we describe a motion planning method for cloth manipulation. We address the problem that only the current shape of the cloth product and its target shape are given. To accomplish this task, it is necessary to determine how to manipulate the cloth and to predict the manipulated shape of the cloth. Therefore, we propose a novel method using deep neural network. An input of the network is a voxelized cloth shape and conceivable manipulations, and an output is a voxelized cloth shape after the manipulations. The effectiveness of the proposed method was proven by experiments using a dual-armed robot. It included quantitative evaluation about the manipulated shape of a rectangular cloth. It was also studied that how to prepare appropriate learning data and do learning well.
In this paper, we present motion analysis and prototype design of a new omni-directional wheel mechanism "ACROBAT-S". The authors group has proposed a special kind of transmission with a dual-ball configuration for transmit drive powers to wheel shaft and steering shaft of an active-caster mechanism (ACROBAT). In the transmission design, two balls are required where one ball is used for combining the two motor powers to rotate the ball in 2D way while another ball is for distributing the combined power to the wheel and steering. The transmission design enables an omnidirectional robot with three active casters for controls 3D motion of a robot by three motors with no redundancy. To reduce the number of friction drive between balls and rollers in the first design, a new type of ACROBAT with a single ball transmission (ACROBAT-S) is proposed in this paper. The proposed new design with single ball configuration contributes to reduce the number of friction drives between balls and rollers for enhancing an energy efficiency and accuracy of robot movement. To design a proposed mechanism, a kinematics of a ball, a roller and active-caster motions are analyzed to derive a mechanical condition for the prototype design. In this paper, we design and build a prototype of a single wheel and conduct experiments. From the results, it was confirmed that an expected motion can be realized.
Constructing way of functional safe systems using artificial intelligence has not been sufficiently discussed. In order to develop and understand safe systems using artificial intelligent technology, we should first clarify the role of artificial intelligence technology in safety systems. We propose to classify the role of artificial intelligence in safe systems into following three policies. (1) Use AI independently from safety related system. (2) Use AI as part of safety related system. (3) AI is used as a human substitute. Generally, the reliability required for safety related systems is extremely high, and there is a gap with the reliability of artificial intelligence technology. As a measure against this problem, we propose asymmetric classification methods for improving reliability on a viewpoint of functional safety. These are to bias decision on non-safety side, are to prevent ambiguous cases mis-recognizes as safe state while possessing the judgment function on the safety side. By these methods, we expect that these techniques will lead to the utilization of artificial intelligence technology in functional safety systems.
In this paper, we introduce an online collision avoidance algorithm for multiple command based manipulators with a concept of job and command priority. Considering application to factory use, we adopt a robot controller which is close to actual industrial controller with a sequence of point-to-point motion command. Previously, our colleagues have developed online collision avoidance methods with interlock algorithm and with advanced collision map. But these two methods have some disadvantages; for example, they cannot restrict to have an collision avoidance motion during commands which must be done continuously such as insertion of a peg into a hole. We introduce a concept of priority with continuity to P-to-P command and job which is a group of some commands; pick an object from a certain position, place an object on a certain position etc. When deadlock is occurred, one robot must get out of the others way. To determine a getting out robot, priority has an important role. When a robot must get out, its priority changes to the same high priority of the other to let other robots on the getting out path move to avoid new collision. With some simulations, we have verified that our new algorithm works well in the case of mutual collision of multiple robot manipulators.
This paper studies the feasibility of a hopper for planetary exploration rovers. The proposed hopper is designed based on shape memory alloy(SMA) actuators, because SMA actuators are light in mass compared with traditional electric motors. This paper discusses a design strategy for the proposed hopper to achieve sufficient locomotion capability on planetary surface. Firstly, this paper presents a basic hopper mechanism and its design strategy with SMA physical model. Secondly, semi-optimized design parameters of the hopper are determined based on brute-force searching. Finally, the experimental results show the effectiveness of the proposed hopper for lunar or planetary exploration.
This paper illustrates the development of active self-melting bolt aiming at self-healing tendon-driven robot with high-load endurance. Recent pioneering research has explored several methods for applying self-healing principles for robotics. For example, exploiting reversible crosslinking bonds are a major approach. They enable conventional robots to gain selfrepairing capability from micro damages such as stubs and so on. However, providing a healing module with large load endurance and autonomous healing capability is yet a challenging task. Then, we categorized design challenges to construct such a module. In addition, we introduced some alternatives to overcome the problems. First, we formulated fracture and healing energy ratio to select proper material for active healing structure. The measure leads the authors to the statement that a low melting point alloy is a powerful alternative. Next, the authors insist that bolted joint structure is a candidate for self-healing module with high-load endurance. Finally, we validated the feasibility of the module with tensile tests using motor-driven tendon unit that has been developed by our group. The result showed that proposed structure had healing capability in spite of its low healing ratio. In summary, the paper presents design, manufacturing method and validation for active self-melting bolt.
In this study, the skill of automotive engineers in sheet metal repair is analyzed. Because no two damage situations are identical, every damage is reconsidered on a case-to-case basis, and flexible responses are required. This work requires considerable human technical skill and relies on experienced workers. When the skills depend on experience, human resource development is essential to impart such skills. The overall objective of this research is to propose a personnel training tool. The fender of an automobile was repaired by workers by a sheet metal working technique. The work was recorded using a video camera and a three-dimensional motion measurement system. Then, the results were analyzed. Experts and non-experts were recorded when performing the task, and the differences in the process behaviors and hammer-strike positions were examined. The results showed that the experts initiated their strikes in the peripheral part of the dents. Thereafter, they applied several broad strike patterns in their repairs: for example, avoiding striking the peripheral part of the dent; striking the central part while avoiding the press line, followed by striking both the peripheral and central parts; and applying many strikes on the press line in the central part of the dent.
In this paper, convenient analysis methods are proposed for analyzing the singular index and the intensity of singular stress field (ISSF) at the vertex on the interface in the three dimensional (3D) bonded body. The analysis methods focus on FEM stresses at and around the vertex. The singular index is determined from the FEM stress ratio at the vertex obtained by performing FEM analyses for the finely and coarsely meshed models. Then, the ISSF is determined from the average FEM stresses around the vertex obtained for the reference and unknown models by applying the similar mesh pattern. The validity of the present methods is examined by comparing the results of 3D bonded models with/without fixed free surfaces. It is found that the obtained singular index has the same accuracy as the FEM eigenvalue analysis. The asymptotic solutions with the singular index and ISSF obtained by the present method correspond to FEM stress distributions. Since the ISSF obtained by the body force method (BFM) is used as the reference solution, the present method for ISSF has the same accuracy as BFM. Moreover, the critical ISSF values are calculated from the experimental results of the butt joints under various adhesive thicknesses. The critical ISSF at the side of 3D butt joint is in good agreement with the critical ISSF of 2D butt joint model. It is shown that the critical ISSF at the vertex of 3D joint is constant as well as the critical 2D ISSF independent of the adhesive thickness.
The influences of film thickness of vinyl and silicone resin coatings on cavitation erosion were examined quantitatively in seawater using a vibratory apparatus. The maximum instantaneous volume loss rate indicates the increase, decrease, or constant with a decreased top coat thickness less than the critical thickness, depending on the combination of the top coat and primer of the acoustic impedance. The critical thickness can be calculated approximately from the duration of impulsive force and propagation velocity of a longitudinal wave created by the collapse of a cavitation bubble, when covered with a resin coating material.
To quantitatively investigate the cause of the changes in arithmetic mean roughness Ra of austenitic stainless steel under low-cycle fatigue loading, precise observation focusing on slip bands was conducted on SUS316NG. During the loading, the specimen's surface topography was regularly measured using a laser microscope. The topography was then characterized by frequency analysis to identify the surface reliefs due to persistent slip bands (PSBs), and their heights were measured. The heights increased with the usage factor (UF). The amount of the increase with respect to UF increased with the strain range. These tendencies are similar to those for Ra. A comparison between Ra and the heights of surface reliefs caused by PSBs showed that the values were strongly correlated. The number of PSBs formed on the surface was estimated from the area ratio of PSBs. The area ratio increased with UF, which is similar to the relationship for Ra. A comparison between Ra and the area ratio showed that these values were also strongly correlated. The product of the height due to PSBs and the area ratio was calculated and it was compared with Ra. As a result, the product was in good agreement with Ra. Consequently, the surface texture parameter Ra represent both the change in the height and the number of surface reliefs due to PSBs.
A propeller fan jet with a duct and straightening plates for the purpose of making a high velocity jet at the far away of propeller was experimentally investigated. As a result, following conclusions were obtained. When the duct and the straightening plates are attached to the propeller, the center velocity at the position away from the propeller becomes fast, because the swirl of the jet becomes weak. As the number of plates increases, the center velocity increases. But when the number of plates exceeds a certain value, the center velocity becomes slow. This is similar about the length of the plates. When the plate is tilted, the larger the tilt angle of the plate is, the slower the center speed becomes in the downstream.
Tube pump transfers liquid inside an elastic tube by moving rollers that squeeze the tube from the outside. This working principle enables a simple design free from watertight requirement, clean and contamination-free transfer due to the non-contact nature and easy re-configuration by changing the tube and the liquid at the same time. However, under the simplest implementation with U-shaped tube and revolving two rollers at constant speed, flow fluctuation is inevitable when one roller leaves the tube and negative pressure is generated by the tube restoration. In this paper, the problem to reduce the flow fluctuation via open-loop control of the roller speed is considered. The ideal speed of each roller is determined from the tube deformation model and realized and tested with two motors configuration. Tracking to the periodic reference speed is achieved by repetitive control. Then the same control strategy is realized with single motor and non-circular gears. The effectiveness of the proposed method is demonstrated by experiments.
Autonomous driving systems (ADSs) could reduce the degrees of human control, and which would result in lack of flexibility of controlling the vehicle. In this study, we proposed a method to allow the driver to control its lateral and longitudinal motions with a time lag, in order to increase the flexibility. We first derived a set of vehicle movements, such as lane changing, overtaking, merging, turning, speed changing, and parking, and related them to a set of control functions that the driver can input. We then developed a joystick-type interfaces with kinesthetic (force) and tactile (vibration) feedback for vehicle control, called haptic force feedback interface (HIF). This interface enables bidirectional interaction between the driver and the ADS, which allows the system to deny inputs from the driver due to collision danger as well as to inform environmental and vehicle states. We performed comparison experiments with a driving simulator among HIF and a previously developed hand-gesture interface (GIF), in addition to manual driving with steering wheel and pedal and autonomous driving with touchscreen interface to designate the destination. The results of experiments showed that the proposed HIF significantly reduced the average input time and input error compared with GIF, and drivers preferred the HIF due to its ability to provide immediate, active, and passive feedback, compared with manual and autonomous driving.
In a conceptual design phase of noise and vibration performance, CAE (Computer Aided Engineering) is frequently introduced to design appropriate properties of individual members. One of the most commonly used computational methods for conceptual design is the eigenvalue analysis of finite element (FE) models. However, since this method ignores formation process of natural vibration, structural engineers cannot adequately comprehend the mechanisms of eigenmode formation in a sense of the superposition of waves. This paper proposes a design method for nodal position control of a mode shape based on three-dimensional wave analysis. First, a ray trace method is introduced to comprehend the eigenmode formations by means of superposition of transmitted and reflected waves in a general three-dimensional beam structure. Summations of computed wave vectors coincide with modal vectors of the structure. The method was then used to discuss the formation of bending mode shape of a three-dimensional beam structure of block geometry. Finally, it is shown that nodal position of bending mode shape of interest can be controlled based on phase changes of bending propagative waves.
The identification of external force acting on a machine or a structure is important for diagnosis. One of the force identification methods is based on the frequency response function (FRF). The method is very useful although it requires the information of the location of acting force. In this study, an identification method is proposed for the case of unknown excitation points. In the method, the inverse problem of force identification is solved by increase the number of FRF by adding a mass on the target structure and truncated singular values. The optimum identification condition is determined by the combined objective function of the reconstruction accuracy of measured data and the variation of the identified external force. The identification method proposed is checked using the actual measured data. A beam structure elastically supported at both ends is considered. The beam is excited by using an electromagnet. This excitation method is non-contact way so the magnitude of the external force cannot be directly measured by the load cell. The external force is identified using the measured data with an excitation frequency. It was shown that the identified external force was feasible using the proposed method. Then the numerical simulation, which was almost similar situation of the experiment, was carried out and the adequate result could be obtained. As the result, it was concluded that the force identification method was very useful for the actual application.
In magnetic hard disk drives, it is important to secure the stability and durability of head–disk interface in relation to a submonolayer lubricant film because the spacing between a head and lubricant surface has to be reduced to ~0.5 nm to achieve a high density recording far beyond 2 Tb/in2. As a succeeding paper of the newly proposed diffusion equation for a submonolayer liquid film, this paper presents a rigorous derivation of the disjoining pressure (DP) from the Lennard–Jones potential (LJP) and formulated the rigorous diffusion equation incorporating the DP. The flow equation for a submonolayer film and viscosity model are the same as in the previous paper. The difference of the rigorous DP and diffusion equation from the previous ones are not significant except in a small thickness regime less than the van der Walls (vdW) distance. Theoretical relationship between the vdW distance in DP and the molecular force equilibrium distance in LJP is elucidated. Rigorous expressions of the conventional DP and diffusion equation for multilayer film are shown. Superiority of the submonolayer diffusion theories to the conventional theory are demonstrated by comparing their theoretical diffusion coefficients with Waltman’s experimental data.
The particle methods are suited to simulate fluid flow problems with large boundary deformation. The moving particle semi-implicit (MPS) method is one of the representative particle methods for incompressible flow. In recent years, the MPS method has received a great deal of attention in various fields of science and engineering. However, the numerical treatment of complicated wall geometry is still an open question. The conventional approaches have severe issues in handling arbitrary shape or calculation accuracy. In these circumstances, this study has been done to propose a novel numerical treatment of solid wall boundary in the MPS method. In this approach, the wall contribution in the discretization scheme is described in a form of volume integral over object domain. Thus, arbitrary-shaped boundaries represented by a polygon mesh can faithfully be considered. Moreover, since the distribution of physical quantity inside object is given by linear extrapolation, it satisfies the prescribed boundary condition with high accuracy. While the volume integral cannot be numerically evaluated with affordable computational cost, it can be transformed into a boundary integral form based on the divergence theorem. The derived boundary integral can be calculated with reasonable cost and acceptable accuracy using a projection technique and the Gaussian quadrature. The proposed method has been examined through several numerical test cases in 2D and 3D. As a result of the numerical tests, the present method is shown to have considerably higher accuracy compared to conventional methods, and its validity is verified.
Previous studies investigated the wear mechanisms under dry sliding conditions and in new oil. However, in practice, wear particles and dust are introduced into the lubricating oil of the machinery. Therefore, it is difficult to conclude that the wear mechanism of the machinery was accurately reproduced in those studies. In this study, we aimed to clarify the wear mechanism of a sliding bearing material, WJ2, under lubrication using seven types of oil contaminated with solid particles. Wear tests were conducted with the contaminated oil using a block-on-ring tribo-tester. The results showed that, even though the ISO cleanness codes were almost the same for all the oils, the wear mechanisms of WJ2 were different. There were three different action modes of iron particles. The gaps between the iron particles and the WJ2 matrix are formed when iron particles were buried into the surface of the WJ2 matrix. In the case of oil contaminated with a mixture of iron particles and soft particles, shear fracture occurred from the gaps formed by the buried iron particles and pits were formed. The sizes and depths of the pits varied with the mutual solubility between the mixed soft particles and the block material; with another type of metal with a low mutual solubility, the concavities were small and shallow. The wear mechanisms of WJ2 were clarified under lubrication with the contaminated oil.
In order to achieve both high precision and high productivity in machining operation, machining error compensation of finished shape named as correction machining is more effective. In general, the correction machining requires additional CAD/CAM operations to generate the NC program for the correction machining, and it takes lots of time and effort. Hence, elimination of additional CAD/CAM operations for the correction machining is effective to reduce time and effort for correction machining. In this study, it is realized by integrating a newly developed On-Machine Measurement (OMM) system using a laser displacement sensor into the Digital Copy Milling (DCM) system. The DCM system was developed in our previous studies and achieves elimination of CAM operation for machining operations like a 3D printer. The OMM system can generate measurement paths automatically from a CAD model of the part based on copying principle. Tracing and measuring accuracy verified by experimental measurement of a reference sphere. Subsequently, a modified surface model represented by 3D point group data for the correction machining is generated immediately from the measurement paths and the measured machining error. Finally, the correction machining is performed immediately based on the modified surface data by the DCM system without CAM operation to generate an NC program. The effectiveness of the correction machining is validated by comparison between the finished sphere surfaces generated by the conventional and the proposed methods.
It has been considered that obesity and metabolic syndrome would be caused by the accumulation of lipid droplets in adipocytes, and would cause a severe problems. To treat these diseases, functional foods to suppress the lipid accumulation are being actively developed, and manufactures are required to approve the efficacy of these foods. However, the quantitative and accurate evaluation methodology of efficacy has not been established yet. Since lipids have a high electrical impedance, it is considered that the amount of lipid droplets in adipocytes is related to the electrical impedance. Therefore, culturing adipocytes and monitoring their electrical impedance simultaneously would enable to evaluate the amount of lipid droplets, and to establish the screening system for functional foods. In this study, mouse preadipocytes (3T3-L1) were cultured on comb-shaped indium-tin oxide (ITO) electrodes to measure the electrical impedance. Moreover, the relationship between the electrical impedance, adipogenesis, and lipid accumulation was evaluated. Briefly, the 3T3-L1 cells were cultured with and without adipogenesis factors for 288 hours. Complex impedance Z and phase angle θ of the cultured cells were monitored during the culture time. As the results, the cell viability was maintained on the ITO electrode-array surface. The complex impedance Z of cells cultured under adipogenesis condition increased during the adipogenesis process. During the lipid accumulation process, phase angle θ tended to increase. These results indicated that the change in impedance Z and phase angle θ could be related to adipogenesis and lipid accumulation respectively. In conclusion, our novel culturing and monitoring device for preadipocytes showed the possibility to evaluate the efficacy of functional foods.
Electroencephalogram (EEG) which has a chaotic fluctuation is difficult to analyze. However, quantitative analysis is sufficiently possible since EEG behavior is deterministic dynamics. Our method identifies EEG model parameters experimentally in consideration of chaotic dynamics of EEG. The purpose of this study is to examine the specific characteristics of model parameters. Validation of the method and investigation of characteristics of model parameters were conducted based on alpha frequency EEG data in the relax state and stress state. The results of the parameter identification with the time sliding window for 1 second, the nonlinear mathematical model is shown to produce outputs that can closely match the complicated experimental EEG data. Further, the results showed that the existence of nonlinear term in the EEG analysis is important and the linearity parameter shows a certain tendency as the nonlinearity increases. Furthermore, the activities of EEG become linear on the mathematical model when suddenly changing from the relax state to the stress state. Therefore, it is the effective analysis method that can calculate the degree of concentrate from the dynamics of EEG signal directly. The results suggest that our method may provide useful information in various field including the quantification of human mental or psychological state, diagnosis of brain disease such as epilepsy and design of brain machine interface.
When an elevator rope for a high-rise building is forcibly excited by the displacements of the building induced by wind forces and/or by long-period ground motion, rope displacement becomes large even if the ground acceleration and the buildings acceleration is small. To prevent this problem, vibration suppressors are used to change the natural frequency of the elevator rope and prevent resonance. The elevator rope is generally modeled using a string, and linear string vibration is well researched. However, the vibration of the string equipped with vibration suppressor encounters geometric nonlinearity, and hence, its characteristics have been studied under a few conditions. In this paper, theoretical solution to the free vibration of the rope is obtained, in the case where the position of vibration suppressor is L/N and the pulled position is (N-i)L/N. Where L is rope length, N and i are integer. Further, finite difference analysis of the rope vibration with vibration suppressor is also performed to obtain the frequency response curves. Resonance frequencies obtained by the finite difference analyses are in good agreement with the natural frequencies for the free vibration, and the number of resonance frequencies near original natural frequency is N-1 when position of vibration suppressor is L/N of the rope.
In Japan, elevator cannot be used during an earthquake, and out-of-service hours tend to be long after large earthquake. It leads to difficulty in evacuation, rescue, and so on. Thus, it is important to suppress vibration of the whole elevator system during operation of an elevator in a vibrating building. In this paper, a vibration control method of compensation rope is proposed as a first step. Considering feedback control, responses are used to compute control force. However, response measurement or response estimation of the rope is too difficult to keep enough accurate. The proposed control method doesn’t require the rope response but elevator car position and acceleration. First, an analysis model is derived by a partial differential equation. Then, control methods based on time-varying natural frequencies of the rope are formulated. Finally, the effectiveness compared with constant tension cases is verified. Two car motions, upward motion and downward motion, are analyzed in a vibrating building. It is confirmed that vibration responses are suppressed by avoiding resonance condition. By contrast, as raising tension method cannot reduce the initial tension by compensation rope's own weight and a compensating sheave weight, the relation between the initial natural frequency of the rope and the frequency of external force effects the control performance.