The flow disturbance to a pneumatic vibration isolation table causes periodic fluctuation of the table. In current study, one cycle of flow disturbance is estimated offline using a disturbance observer. The time series data of one cycle estimated disturbance is then stored in the memory of digital signal processor. The program codes are prepared which can detect every cycle of the flow disturbance based on the threshold of table position. The estimated signal is then repeatedly injected from the memory through a compensator to the servo valve to suppress table fluctuation due to periodic actual flow disturbance. The effectiveness of this method is demonstrated by experimental results.
Rotary diamond dressers are one of the most widely used dressers for the dressing of vitrified grinding wheels. In this study, we develop a relatively comprehensive dressing mechanism for the rotary diamond dresser that takes into consideration the relationship between the dressing conditions and the dressing trajectories of diamond grits formed on the working surface of a grinding wheel. The dressing mechanism can be used to determine the dressing performance, i.e., whether or not the diamond grits come in contact with the entire circumferential surface of the grinding wheel, known as complete dressing. A computer-aided simulation of the dressing process is developed to visualize the dressing trajectories formed on the working surface of the grinding wheel for a given set of dressing conditions, i.e., the velocity ratio of the rotary diamond dresser to the grinding wheel, up-cut or down-cut dressing, and single-pass or multipass dressing. Using the simulation process, the maximum feed speed of the rotary diamond dresser in single-pass dressing and the minimum number of passes in multipass dressing required to realize complete dressing are examined.
In recent years, environmental issues and high labor costs have been receiving increasing attention. One example is the manufacturing process of conventional oil tempered shaped wire which is high cost, time-consuming and polluting. The aim of this study is therefore to attempt to solve the problems of producing this particular form of wire. In this study we investigate the shape rolling process combined with the in-line induction heat treatment process for tempered trapezoidal wire. The round wire was heated to austenitic temperature using in-line induction heating equipment, and the wire was formed into a trapezoidal shape using a tandem cantilever type rolling mill, then quenched in water and tempered. The entire sequence was carried out in a single procedure with an automated line, the above-mentioned shape rolling process was verified by means of the finite element method, and finally the tempered trapezoidal wire was coiled to a helical form, i.e., rectangular wire die springs, which then underwent fatigue testing. The results revealed that the mechanical properties and the fatigue testing results of the die springs all satisfied industrial standards. The advantages of the manufacturing process of this study are that is highly efficient, low cost, and more environmentally friendly than the conventional process.
This study raises a new electric wheel with active control of suspension for in-wheel motor. Proceeding from the reality, we made a simulation analysis on these four models: a sample car with no motor, a motor with fixed joint, and active/inactive control suspension for in-wheel motor. During the analysis, less-than-10mm relative vertical displacement was used as a prerequisite, reducing the car's acceleration, the suspension flexivety, and the wheel's load as basic conditions, reducing the wheel's vertical acceleration as the primary target, LQR control of active suspension as the motive. According to the analysis, by optimizing the parameter of inactive control suspension for in-wheel motor, we can solve the vertical problems caused by the electric wheel's mass, but the vertical impact to in-wheel motor is still heavy. However, using active control suspension for in-wheel motor can not only rise the smoothness and safety of the car, but also reduce 64% of the vertical impact comparing to inactive control suspension. This improves the active control suspension for in-wheel motor can effectively resolve the electric cars' vertical problems both theoretically and practically.
In a companion paper, part 1, a computer-aided design method for pocket elliptical bearings has been developed. Its application is discussed in the current paper, which mutually related goals are: to understand how bearing design and particularly pocket geometry affect the bearing performance, to determine optimal values of the driving variables that control bearing profile and pocket width, to choose a suitable supply groove layout. As explained in part 1, the developed method does not include an automatic optimization tool. Therefore, in order to reduce the number of the variables that control the bearing geometry involved in the optimization task, the clearance of the assembled bearing (pocket clearance) is kept constant. Hence, the optimization of the bearing shape is performed by changing pocket opening, pad eccentricities, pocket width, lubricant supply mode.
Two important factors are related to haptic hand-motion perception: one factor is the sensations employed for perception and the other is the person's initiative in the hand movements. The following two sensations are considered representative for the sensation factor: the proprioceptive sensations that return the physical states of joint rotations and muscle activities with extension and flexion and the cutaneous sensations of fingerpads. Since these are primary and secondary in haptic motion perception, we examined the following two sensation modes: (1) cutaneous-combined proprioceptive mode, “Co” and (2) without-cutaneous proprioceptive mode, “Pr”. The former is expected to surpass the latter. For initiative factors, we considered the following two initiative modes important: (a) active mode, “Ac,” where persons move their hands with their intention and (b) passive mode, “Pa,” where their hands are pulled by a device against their intentions. The former is expected to surpass the latter. Considering these two factors, we examined haptic hand-motion perceptual performances among the following four perceptual modes by psychophysical experiments: (1-a) cutaneous-combined proprioceptive active, “CoAc mode,” (1-b) cutaneous-combined proprioceptive passive, “CoPa mode,” (2-a) proprioceptive active, “PrAc mode,” and (2-b) proprioceptive passive, “PrPa mode”. From the viewpoints of systematic and random errors, statistical test results suggest that two factors, sensation and initiative, almost independently contribute and additively enhance performance: CoAc mode showed the largest sensibility and the minimum random errors. We also found other haptic directional perceptual characteristics in systematic and random errors.
A computer-aided design procedure suitable for pocket elliptical journal bearings for turbomachineries is proposed. After the description of their geometry and manufacturing, the driving geometric parameters characteristic of the pocket bearing are identified together with the design variants that influence their choice, like supply groove layout and the axial size of the pocket. The concept of journal mobility plot, capable to ease the post-processing of results and useful in journal vibration monitoring, is adapted to pocket elliptical bearings and, in general, to non-circular bearings. The proposed design evaluation includes a calculation sequence involving geometric parameters, FEM simulation and the calculation of proper performance indicators, from which the global performance of the bearing is finally computed.
In this study, a flat thrust bearing is developed by active exploiting the slip flow generated on a water-repellent surface. In order to produce a load, this bearing has a structure that generates a pressure flow by using the discontinuity of shear flow rate between a water-repellent surface and an untreated or a hydrophilic surface. This structure results in the completely flat bearing that has no geometrical variations in its surface. Friction tests were carried out with respect to the water-repellent thrust bearing that consists of three water-repellent parts and untreated or hydrophilic parts. The results verified that this partial water-repellent thrust bearing functioned well with a low and stable friction coefficient (less than 0.002). And lubrication surfaces had no damages at all because both surfaces are separated with fluid film which enables to avoid the solid contact. The friction coefficient became lower for the bearing having large difference of contact angle (thus, shear flow rate) between both parts. Furthermore, a friction coefficient for the bearing of which water-repellent part and hydrophilic part had same area was the lowest, and friction coefficient became larger than its value in case of not only wide water-repellent part but also narrow one. These results suggest a possibility that this thrust bearing operates by the same mechanism as a conventional bearing under fluid lubrication.
The purpose of this work is to improve the throughput of step-and-scan lithography equipment to shorten the production time of a wafer. For this purpose, we propose a method for solving the MSOP (Movement Sequence Optimization Problem), which is the problem of computing the fastest schedule for visiting all shots on a wafer. It is well-known that the MSOP on step-and-repeat lithography equipment can be modeled as a traveling salesman problem. In contrast to step-and-repeat lithography equipment, a schedule for step-and-scan lithography equipment must also indicate the scanning direction of each shot, in addition to the sequence of the shots. For this reason, the traveling salesman problem formulation for step-and-repeat lithography equipment cannot be applied to solve the MSOP on step-and-scan lithography equipment directly. We overcame this difficulty by introducing auxiliary vertices to model the scanning directions in the traveling salesman problem formulation. By this method, we were able to compute exact optimal sequences considering the scanning directions of shots for several MSOP instances. Our numerical experiments demonstrated that our proposed method was capable of computing exact optimal solutions for real-world MSOP instances having up to 232 shots on a wafer. These optimal solutions gave a 0.25% to 4.66% improvement in productivity over solutions computed by previously known methods.
When electrical pitting occurs, the sound level and vibration of a rolling bearing increase, and a ridge mark appears on the internal surface of the bearing. The frequency at which the sound and vibration increase is attributable to the undulation of the ridge mark formed on the surface. However, the phenomenon of electrical pitting was observed without the occurrence of a ridge mark. Therefore, in this research, the vibration acceleration was measured independently of the occurrence and nonoccurrence of a ridge mark. Then, the frequency at which the vibration acceleration increased was clarified experimentally. The conclusions are as follows. (1) Under the nonoccurrence condition of a ridge mark, multiple integral of frequency components for rotation speed increased. (2) In the occurrence condition of a ridge mark, the vibration acceleration increased in the frequency caused by the number of undulations per round for a ridge mark. (3) The number of undulations per round in the ridge mark and the frequency at which the vibration acceleration increased varied even when the experiments were performed under the same conditions.
Structural topology optimization has been applied to nonlinear structural problems, but conventional methods considering geometrical nonlinearity encounter difficulties during nonlinear analysis using the FEM (Finite Element Method). In this study, we propose a new level set-based topology optimization method considering geometrical nonlinearity, using a meshfree particle technique, for optimizing elastic structures that undergo finite displacement. In the proposed method, the MPS (Moving Particle Semi-implicit) method is used for solving the state equation, since it does not use a mesh for geometrically nonlinear analysis. In this paper, first, a topology optimization problem is formulated based on the level set method, and a method for regularizing the optimization problem using the Tikhonov regularization method is explained. The reaction-diffusion equation that updates the level set function is then derived and an optimization algorithm, which uses the FEM to solve the reaction-diffusion equation when updating the level set function, is constructed. Next, the particle interaction model and the treatment of geometrical nonlinearity in the MPS method are described and the implementation that combines the level set-based topology optimization with the MPS method is explained. Finally, several numerical examples are provided to demonstrate the effectiveness of the proposed topology optimization method for geometrically nonlinear problems.
A multi-chip module substrate is designed for packing two or more semiconductor chips. On a substrate, there may exist two types of faults; one in a wiring and the other at an intersection of two wires, called via, and the faults must be detected. The testing is performed by a pair of probes, which touch the two ends of an inter-chip wiring. The completion time of the whole testing is the time when it has been confirmed that no fault exists on the substrate. A two-probe routing problem is considered to design efficient routes of the two probes for minimizing the completion time of the whole testing. In this paper, the two-probe routing problem is formulated as a constrained shortest path problem, and a heuristic algorithm by local search techniques is proposed. Computational experiments demonstrate that the proposed heuristic algorithm outperforms a known two-phase heuristic.
The electret condenser microphones (FilmECMs) with film lamination and silica agglomerates were fabricated and the influence of the silica agglomerates on the characteristic of the FilmECM was investigated. The silica agglomerates was formed on PFA (perfluoroalkoxy) films by the application of colloidal silica using inkjet printing. The silica agglomerates for spacers formed the microgaps between the insulation films in the gap. Eventually, The silica agglomerates drastically enhanced the sensitivity of FilmECM while the resonance frequency was decreased. The size and the interval of the silica agglomerates influenced on the sensitivity and the resonance frequency. Such a influence can be explained by the density of the contact points of the films and silica agglomerates in the gap of FilmECM. Thereby the FilmECM which had the comparable sensitivity with commercial ECM was obtained. The resonant frequency was much higher than audible frequency (around 50 kHz). Hence, a wideband ECM could be obtained using FilmECM if the poor sealing of the gap and the diffraction of the sound is eliminated.
Pneumatic active anti-vibration apparatuses (AVAs) are widely employed for the highprecision positioning of wafer stages in semiconductor lithography equipment. However, there exists delay of transmission of air supplied to air springs. In this paper, we consider the suppression of vibration caused by the time delay (i.e., dead-time) of AVAs. The dead-time is compensated by using a Smith predictor, which is well-known as a control method for time delay systems. In the implementation of the predictor, the plant model and the dead-time are needed. For this reason, this paper focuses on the tuning of Smith predictor effective for the control of AVAs. To improve the model accuracy of AVAs, the approximation model of pipe resonance is utilized. Moreover, to determine suitable time delay in the Smith predictor, our methods utilize the resonance frequency of the control system and the tracking error of the isolated table. Conventionally, the nominal value of the dead-time can be obtained by using step response of the control system. On the other hand, it is difficult to exactly estimate the dead-time of AVAs due to position sensor noise. Therefore, the time delay is precisely tuned by proposed methods instead of the step response approach in order to improve the performance of the Smith predictor. Experimental results show that when the error of the time delay in the predictor is zero, the resonance frequency and the time integral become minimized.
In this paper fundamental sound absorption characteristics of expanded polystyrene beads with several geometries are reported when they are packed in some thick layers with and without back air space. The normal incidence sound absorption coefficients, which were obtained by the experiments using two-microphone impedance tube, were evaluated comparing to theoretical estimations. Experimental data were also compared to the similar conditions but hard material particles like glass beads whose acoustic property was investigated by Sakamoto et. al. in a preceding study. Then following results were obtained; packed layer with expanded polystyrene beads has almost equal sound absorption coefficient to the similar layer with hard and solid material: numerical estimation of sound absorption coefficient is valid enough except for the case having large back air space: lowering peak frequency of sound absorption coefficient is available by overfilling and compressing particles. The authors also consider that applying soft, light, and low cost material to the sound absorbing structures is very meaningful. Because human damage caused by falling of wall and ceiling panel of buildings is avoidable particularly under an earthquake attack.
Sound transmission loss is relatively small in thin louver boards with a high aperture ratio. This study investigated louver elements with a sound attenuating function. Using narrow tubes, an array silencer was built into composite louver boards and a high aperture ratio was maintained. Several constructions for such louvers were prototyped, measured, and analyzed theoretically. Sound transmission loss was measured using four-microphone impedance tube. Then, sound transmission loss was calculated by a transfer matrix based on one-dimensional axial coordinate system analysis. The attenuation of sound in tubes should be calculated because a thin louver board must comprise narrow tubes. Therefore, an accurate propagation constant and a characteristic impedance based on two-dimensional analysis were introduced to enable theoretical analysis. The calculation results, including attenuation, and the experimental results had good coincidence. Moreover, the theoretical analysis confirmed that the silencer worked effectively and could be applied to silencer designs.
This paper describes the optimum design of recess shape for the proposed hydrostatic bearing, and dynamic control of oil film thickness for an active compensating hydrostatic bearing by using a servo valve and a proposed controller. First of all, this study is theoretical study concerning static performance of a hydrostatic bearing having recess of optimal shape parameters. Because of the recess of the traditional hydrostatic bearing only has one oil outlet that is easy to concentrate the pressure of the recess at the outlet, leading to non-uniform pressure distribution. Hence, the objectives of this study are to design a hydrostatic bearing with high load capacity, high stiffness, low flow rate and uniform pressure distribution by using HTGA/Gray optimal approach. In addition, this study integrates servo control technology to compensate the pressure of the bearing with an intelligent nonlinear controller to maintain a constant oil film thickness. However, the hydrostatic bearing is a nonlinear system and is affected by numerous uncertainties; that is, the parameters can be changed by factors, such as temperature, leakage, and disturbance. Therefore, the proposed controller proposes a self-tuning mechanism to modify the output scaling factor, and adds a dead zone compensator to avoid the insensitive area of a servo valve. Finally, the experimental results are used to verify the feasibility and practicality of this study.
To improve positioning accuracy in a head-positioning control system for hard disk drives, we have developed a triple-stage-actuator system on a spin-stand tester. In this system, the first stage is a VCM actuator for moving a head-stack assembly, the second stage is a PZT actuator for moving a suspension, and the third stage is a thermal actuator for moving read/write elements. The frequency response of the thermal actuator showed that the thermal actuator system has no mechanical resonant mode. Therefore, this head-positioning system with a thermal actuator can control the head position in high frequency range without negative impact from mechanical resonances. As a result, the servo bandwidth of the proposed triple-stage-actuator system can be higher than that of the conventional dual-stage-actuator system which consists of the VCM and the PZT actuators. This improvement is similar to the improvement from the single-stage-actuator system to the dual-stage-actuator system. Experimental results on the spin-stand tester showed that the proposed control system can dramatically improve the positioning accuracy during a track-following control.
Assistive robotic technology can play a major role to improve the quality of life of the physically weak people such as aged, injured, disabled or handicapped. Many assistive devices have been developed according to the needs of such individuals. Especially, upper-limb power-assist exoskeletons have been able to draw attention, as the upper limb motions are very important for the daily activities. Electromyography (EMG) signals of the upper limb muscles have frequently been used as a primary signal to control the upper-limb power assist exoskeletons, because the EMG signals directly reflect the motion intention of the user. However, one of the main problems for EMG-based control is the muscle fatigue, because the muscle fatigue can affect the EMG patterns. When the user's muscles get fatigued, it is required to consider the variety of EMG signals on the EMG-based controllers. In this paper, the effects of muscle fatigue on EMG-based control are analyzed based on upper-limb elbow flexion/extension motions and fuzzy-neuro modifiers which intend to compensate for the muscle fatigue effects based on a combination of EMG Root Mean Square (RMS) and EMG Mean Power Frequency (MPF) are proposed. The effectiveness of the proposed fuzzy-neuro modifiers for compensation of the effects of muscle fatigue are evaluated by conducting experiments.
In recent years, Japanese society has been aging, engendering a labor shortage of young workers. For a robot that is often in contact with people and which must provide safety and flexibility in nursing and welfare, the development of a soft, lightweight, and compact actuator has been sought. Particularly robots that are intended for use in fields of medical care and welfare should be safe when functioning around humans because they often come into contact with people. Therefore, a tendon-driven balloon actuator (balloon actuator) has been developed for a robot hand to be used in such environments. For this study, we developed a stroke control system for the balloon actuator using a predictive functional control (PFC). The PFC is one of model predictive control (MPC) schemes, which predicts the future outputs of the actual plant over the prediction horizon and computes the control effort over the control horizon at every sampling instance. This paper reports the PFC control performance of the balloon actuator. We compared the control performance for the actuator with that of the PFC and a PID control system.
The tribological characteristics of sliding parts can be controlled by creating a microstructure on their surface. However, the effect of microstructures on the surface of a small hole of an inner sliding part or a hardened part has not been investigated. Thus, an efficient method, electrical discharge texturing (EDT) was previously developed to create a microstructure using a single discharge. In this study, whirling electrical discharge texturing (whirling EDT: WEDT) was developed as a method of creating microstructures on the inner surface of small holes and mechanical parts made of high-hardness materials. It was examined whether the WEDT equipment can be used to texture the inner surface of small holes and high-hardness materials. In addition, the fundamental characteristics of WEDT were studied. It was verified that, it is possible to create microstructures via the whirling phenomenon and single discharge of WEDT. The shape and texture-area ratio can also be controlled by WEDT, where the texture-area ratio is controlled by varying the feed speed.
A large portion of patients of larynx cancer tekes total laryngectomy and loses their original voice consequently. Some ways to obtain substitute voice for total laryngectomees have been presented, however, each of them cannot conquer inconveniences, tone quality, extremely low tone, monotonousness etc. We invented very simple, small enough to be built in TE (tracheaesophageal) shunt valve but functional substitute voice that is driven by patient's own expiration and its tone pitch can be controlled by expiratory pressure simultaneously. The new device has an outward-striking membrane as an oscillating valve and a set of piston-cylinder mechanism, which controls oscillator's tension and alters pitch of sound. As results of performance experiments applied to the prototype model made as twice scale as an actual dimension, the device produces the lowest sound frequency of 205 Hz and pitch range of 374 cent being approximately proportional to driving air pressure between 0.8 and 2.2 kPa. It is said that normal pitch of female voice is around 210 Hz, thus we consider the possibility of the device as a new substitute voice was shown that contributes to improvement of total laryngectomees' QOL particularly to female patients.
In this paper, a new kind of gas foil journal bearing using multi-decked protuberant foils as elastic support structure has been developed. Experimental test on the multi-decked protuberant foil journal bearing has been conducted on the high speed turboexpander. The maximum speed of 25 mm diameter rotor reached as high as 100 krpm. Meanwhile, at the same gas supply pressure, the rotor speed is higher in speed-down process than that in speed-up process due to the coulomb friction between the foils. In the whole test, the subsynchronous whirl can be suppressed effectively using the new structure. This all metal hydrodynamic gas foil bearing may be a promising candidate in cryogenic systems.
In many linear quadratic (LQ) optimal regulator problems, the tuning of design parameters such as weighting coefficients in the criterion function depends on trial-and-error simulations. In this note, an LQ optimal regulator is used to prevent tumbling from power-assisted carts. The cart has two actuators: a DC servomotor that drives the cart, where power assistance is realized by impedance control of the motor; and a linear motor actuator to prevent the conveyed objects from tumbling. This note mainly discusses a systematic LQ optimal regulator design method for the latter actuator. The relationships between the feedback gain tuning of the tumble prevention actuator and controlled object responses were examined by simulation. Actual feedback gains were then determined by gain scheduling of the gains obtained a priori based on the relationships, control specifications and constraints. The effectiveness of the design method was verified by simulation examples.