This paper proposes a method for optimizing the operating conditions of industrial robots in order to improve their reliability, as an application of a facility life cycle simulation to life cycle management. In the life cycle simulation, operational and environmental stresses acting on components are evaluated and their deterioration processes and resultant functional degradation are simulated based on task descriptions, robotic models, and deterioration models. By means of hybrid genetic algorithm, a layout of the robot and velocity patterns for executing specific operations is optimized so as to minimize deterioration of the joint gear, while maintaining a constant total execution time for the operation. Application of the method to robot manipulators in an automatic assembly line is described as an illustrative example.
The main purpose of this research is to make clear the walking mechanism by a dynamic model based on walking principles, that is, ZMP principle and minimum consumption energy principle. We have used ZMP principle for stable walking and minimum consumption energy principle for optimum configuration. First, we have developed a two-dimensional dynamic model. This model generates a trajectory of the center of the gravity of the body employing the above-mentioned principles and yields successively stable walking cycles. Next, we have extended the two-dimensional model to the three-dimensional model which includes the ZMP principles in the lateral plane. The dynamic simulation of the three-dimensional walking shows a behavior much closer to a real human being's one. Finally, we found out that these two walking principles take an important role for human like walking.
This study proposes a new coordinate measuring machine (CMM) based on a three-degree-of-freedom parallel kinematics. This paper presents a kinematic calibration method using three-dimensional ball plate calibrated beforehand by accurate conventional CMMs. The least square method using Jacobian matrix estimates the kinematic parameters so that the ball position errors obtained by measuring the ball plate are minimized. The above calculation has been repeated in both numerical simulations and experiments. An increase of the number of estimating parameters has decreased the position error of the ball plate from 180 μm to 6μm in the experiments. Furthermore, accuracies of both length measurement with block gauges and profile measurement with an optical flat have been improved significantly after the calibration. The measurement accuracy most improves when the repetitive operation is discontinued after three calculations. The balls of the ball plate must be extensively located in a three dimensional space.
This paper describes a surface encoder with a multi-spot light source. The surface encoder consists of an angle grid having a two-dimensional (2D) sinusoidal angular pattern on its surface, and a 2D angle sensor used to detect the 2D angle profile of the grid surface. The 2D XY displacements and tilt motions (pitch, roll and yaw) can be detected by the surface encoder. In this paper, a multi-spot light source is employed in the angle sensor. The multi-beams from the light source are projected onto the angle grid surface at the same phase positions in different periods. An averaging effect greatly reduces the effect of the dispersion of the pitch spaces of the angle grid, which acts as the measurement reference of the surface encoder. A laser diode and a grid film are combined to generate the multi-spot beams with pitch spaces of 300 μm, which are the same as those of the angle grid used in the experiments. The surface encoder with the multi-spot light source shows a good performance. A selfcalibration technique is also applied to calibrate the surface encoder.
The aim of this study is to consider positioning characteristics of floating object suspended by steady-state squeeze air films. For the columned thrust squeeze air bearing model, the numerical analysis technique based on Lees' difference approximation method is applied to solve the Reynolds equations. The piezo-driven oscillating pad generates the steady-state squeeze air film and step motion for shifting the floating object. The numerical results for the step response of the object position and air film pressure extremely agreed with the experimental ones. The step response showed the strong nonlinearity of dynamic air film characteristics. The phase lag between squeeze motion and step feed motion has a great influence on the step response. Because the squeeze motion is sinusoidal oscillation, the acceleration which acts on floating object affects with phase lag. Therefore minimizing the acceleration by controlling the phase lag can decrease the overshoot. The numerical results are shown in case of single air film generation on lower side and in case of dual air films on upper and lower sides. As a result, the operation with dual air films increases the damping characteristic and is effective to decrease the overshoot especially for the large step width.
TiNi shape memory alloy has been recently investigated for use in microactuators because of the high power to volume ratio. Conventional sputtering methods, such as RF and DC sputtering and magnetron sputtering, have previously been used by other workers in order to deposit TiNi thin films. As deposited films produced by these methods are amorphous, and are then crystallised typically by annealing at 500 °C for 1 hour in order to exhibit the shape memory effect. These deposition methods have invariably used alloyed targets to grow thin films. In this investigation, an Ion Beam Sputter Deposition (IBSD) method has been used by which argon ions are used to bombard non-alloyed targets. The thin films grown by this technique demonstrate the characteristics of the shape memory effect. Films have been characterised by electrical resistivity and change of resistance against heating and cooling temperature, giving physical properties in excellent agreement with those quoted in the literature. Compositional and density measurements were done by X-ray reflectometry and were consistent with equi-atomic composition and nominal density for TiNi.
A micro bimorph-type resonator, 10 mm in length, 1.014 mm in thickness and 0.97 mm in width, made of 130-degrees-rotated Y-cut lithium tantalate with a large piezoelectric effect and a large Q-factor was developed for use in an angular rate sensor. For a sensor with high sensitivity, the resonant frequency of the driving-mode vibration must correspond to that of the detecting-mode vibration. Therefore, we experimentally adjusted the two resonant frequencies by YAG-laser trimming. This experiment showed that the difference between the two resonant frequencies was 1580 Hz before the adjustment by the YAG-laser trimming but decreased to 5 Hz, at the rate of approximately 18 Hz per microgram of trimmed tantalate, after it. Moreover, it was found that the resonator after the adjustment can vibrate, at the same resonant frequency, without mechanical coupling not only in the driving-mode but also in the detecting-mode. It is thus concluded that such desirable vibration characteristics make the resonator suitable for the sensing element of an angular rate sensor.
This paper describes that the proposed method is able to evaluate accurately the resistant torque acting on rotating spindle system which includes rolling bearing, under high-dm N condition lower than two million mm rpm. The resistant torque is calculated as the product of the angular acceleration during free-running and the equivalent moment of inertia of spindle. The acceleration is calculated from the accurate measurement of change in series of each rotation-cycle under free-running. The equivalent moment of inertia is the sum of the moment of inertia of spindle rotor, the effect of rolling elements and the effect of retainer for the elements.
Automatic estimation system of human operator's fatigue is considered valuable for prevention of industrial accidents and hazards as well as improvement of operational efficiency, if it can be realized. In the system, from the standpoint of practical use, the information required for the estimation must be the operational and physiological ones, which can be detected easily with little disturbance of operator's action. In this research, the objective task is small hole drilling and the authors have chosen fluctuation of operator's body motion, cutting force, task time, task error, blood pulse period, respiration period, electromyogram, electroencephalogram, etc. as the information. And then, the relation between the information and fatigue has been investigated by using the multiple regression analysis. The fatigue has been evaluated by the critical flicker fusion value and subjective fatigue symptom point. As the result, it has been found that there was a close relation between the detected information and fatigue for every operator individually, though a unique regressive equation for all operators could not be found.
At the edge portion of the wafer sliced in ID-Blade sawing, edge-chippings are usually broken out. This has become an important factor which should be improved in the manufacturing process of semiconductor devices. This study aims to reduce the edge chipping size by means of utilizing slurry which mixed a little free abrasive grains into the working fluid. This method brought the buffer effect between diamond grains adhered to the ID-Blade and the edge portion of workpiece. In this paper, reduction of the edge-chipping utilized slurry and influence of engage and disengage angle of ID-Blade to the workpiece are described. Consequently, edge-chipping size at the edge portion of the wafer was reduced compared with the case in which usual working fluid is used and it became small when an engage and disengage angle are shallow.
An operation called 'tensioning' is performed on the disk of tipped-saw used in the cutting-off process in order to add a residual tensile stress and to raise consequently a natural frequency. The conventional tensioning method which deforms plastically the disk by roller and/or hammer requires a very high skill. This paper proposes two tensioning methods as named 'expansion fit' and 'internal pressure' in order to simplify the operation, and investigates the property of disk such as natural frequency, rigidity etc. In addition, the cutting-off performance of these tipped-saws is compared with that of the conventional method. The new methods proposed can prepare an adequate residual stress in the disk and consequently increase the natural frequency and the rigidity as same as the conventional method. When sawing S45C steel under low cutting speed, however, the cutting edge has broken down due to large amplitude of run-out of the disk and high sawing force from the beginning of sawing.
Micromanipulator technologies have been developed in various fields such as micromachine production, medical operation and so on. In these fields it is necessary to obtain not only micro displacement information but also sensitivity to minute reactional forces. Hysteresis linearization on piezoelectric actuator is achieved by the computer control, including turns at arbitrary points.The compensation method for the transmission error is assumed to be effective also in case that different type manipulators are used on each side.
In the case of internal finishing of SUS304 stainless steel pipe by a magnetic field assisted finishing process, the smooth rotational motion of the magnetic abrasive along the inner surface of the pipe is necessary to achieve a smooth surface. Lubricant is considered indispensable to obtain the smooth rotational motion of the abrasive since it reduces the friction between the abrasive and inner surface of the pipe as well as cools the finishing area and ejects chips from the finishing area. However, lubricant can lead to environmental pollution and requires chemical cleaning after finishing. It is, therefore, desired to minimize the lubricant in the finishing process. This paper discusses the role of the lubricant in the process and proposes a method of environmentally conscious magnetic field assisted finishing. The internal finishing experiments of pipes demonstrated that the dry condition is unacceptable in this process. Distilled water was, therefore, applied as substitute for commonly-used soluble type barrel finishing compound. This achieved smooth internal finishing of the pipe without disturbing constituent components of the pipe material as the commonly-used lubricant does, showing the feasibility of an environmentally conscious magnetic field assisted finishing process.
To address the problems of throughput rate, post-process cleaning, environmental aspects as well as to achieve the total surface integrity for large-scale silicon wafers, the semiconductor industry is looking for a fixed abrasive solution as the alternative. As the result of intensive R&D, many achievements have been seen in machine tools, grinding wheels and process technologies, which make it possible to control the motion of each cutting edge very precisely. This paper kinematically analyzes the motion and path of cutting edge at plunge grinding with a cup-type grinding wheel, where the contact area is unchanged. Two facts have beenrevealed; 1) the cutting path pattern is determined only by the rotational speed ratio of the wafer against the wheel. 2) Once the grinding reaches the steady state, the cutting edge goes over the same path so that the cutting path pattern remains unchanged. Three problems have then been addressed from the cutting path pattern; 1) Different rotational speed ratio grants a different cutting path density, thus achieves significantly different surface roughness. 2) The cutting path density in the wafer center is higher than that at the fringe so that the surface toughness is inconsistent over the whole wafer. 3) The vaziation in the cutting path density also leads the ground wafer to a concave profile. Solutions are proposed on the basis of analytical and experimental results. 1) The criteria to terminate the grinding proccss are established to improve the surface roughness. 2) The whecl geometry is optimized to attain a consistent cutting path density. The results achieved in this research are also applicable to the generation of large-scale flat surface other than silicon wafer.
In order to measure independently forces acting on rake face and on chip breaker, a tool dynamometer has been designed and constructed. Using step-type and groove-type chip breakers, orthogonal cutting and oblique cutting experiments have been performed. For a step-type chip breaker, decreasing the distance between cutting edge and a chip breaker (chip breaker distance) gives the chip formation for tools with smaller tool-chip contact length than that of a conventional tool. The thrust force acting on the rake face decreases about 75% of that of the conventional tool. For groove-type chip breakers using tools with shortly restricted tool-chip contact lengths, it is found that the magnitudes of forces acting on the rake face are constant in spite of the chip breaker distance. This shows that the forces acting on the cutting point are scarcely influenced by external forces acting near the chip breaker. Even in the case of small broken chip produced at small chip breaker distance in oblique cutting, chip flow direction calculated from forces on the rake face approximately supports Stabler's chip flow rule.
To realize a high-efficiency machining by solid square end mill, it is important to increase the number of teeth, improve the rigidity by increasing the moment of inertia of the cross-sectional area, and also to design a flute geometry that can evacuate the generated chips smoothly. However, it is not easy to satisfy all the above specifications, as a larger flute is more effective for chip evacuation but it causes lower rigidity and as such makes the increase of the number of teeth more difficult. This paper analyzes the motion of chips generated when using a spiral cutting edge and points out that there exists a different component of the angular velocity of chip from up-curl and sideward curl, which has not been discussed so far. Based on the analysis, a simulation model of chip flow is proposed and a high performance end mill was developed that has 45°helix angle and employs a flute geometry to guide the up-curl. The three-dimensional motion of chips is shown in side and groove cutting. The chips generated by the simulation are then compared with chips collected after actual machining.