Properties of a swept-volume defined by a solid object moving in a three-dimensional space are theoretically discussed in this paper. First, the generation mechanism of the boundary of a swept-volume is formulated based on a concept of 'forehead' and 'rearend' faces on the object boundary. Next, the geometric necessary condition on the generation mechanism is derived using the minimal analysis theory under an object expression as a set-theoretical combination of volumes with C∞-class boundaries. Moreover, the geometric necessary condition is used for classification of swept-volume boundaries. The discussion in this paper gives fundamental knowledge for engineering applications such as NC machining simulation, optimization of cutter path, kinematic simulation and so on.
The elastic behavior of screw thread has been studied by tensile test on the screw thread of M6-M20×1.5, and by Finite Element Method. Elastically equivalent cylinder's cross sectional areas of threaded bar approximately coincide with experimental and calculated values. Both values are small compared to the usual value called stress area, which is used to estimate the tensile strength of the screw thread. Then a new equivalent cross sectional area is proposed expressing the relation between load and elongation in the screw thread, and an empirical equation is obtained that the equivalent area of the screw thread is considered to be a function of the ratio of pitch to major diameter on the external thread.
In this paper, a new method for designing the structure of manipulators based on evaluation of their adaptability to tasks is proposed. In the method, task directions are classified into three kinds of direction; operational direction, constrained direction and free direction. On each direction, condition of constraints by task environment is represented. The tasks are represented by a set of direction and condition of constraints. A new criterion, operability, is defined to quantify adaptability of manipulator to tasks, taking account of mobility in operational directions and immobility in constrained directions. The mobility and immobility is calculated based on the Jacobian matrix of manipulator. The operability evaluation method is implemented, and applied to structural design of manipulators, in which link parameters are optimized by the genetic algorithm. This system can derive suitable structure of manipulator to various tasks. The effectiveness of the system is shown concerning examples of welding tasks.
The time-dependent distribution of abrasive grain size in a lapping process was simulated by means of essentially the same method as that in the last report. However, the following two parameters were newly obtained by a crushing experiment of grains and used in the simulation, those were a multiplication rate of the number of grains and the probability of transition between different divisions of grain size. The breakage probability of grains was also revised on the basis of an experimentally observed change of the mean grain size. The main results obtained are as follows; (1) The value of 3.67 was obtained for the multiplication rate. (2) The transition probability is expressed by a continuous function of grain size x as shown in Fig.5, which is approximated by Eq. (6) in the text. (3) The revised values mentioned in (1) and (2) were found to give more advanced simulation by comparing with the experimentally obtained change of distribution. (4) The difference of breakage probability function φ (x) did not seriously affect the transition behavior of simulated distribution.
This paper deals with a machining method for making a large non-axisymmetric aspheric surface with a high accuracy. An electric micrometer has been set near a grinding head on 5-axis control ultra-precision grinding machine for measuring the shape error of ground surface in conformity with the machine movement due to the cutter location data. A series of the measured shape errors corrects the former cutter location data automatically and the next grinding operation will be performed by the new cutter location data. A large CVD-SiC sample 110 by 510 mm has been ground into a toroidal surface of 0.75 μm in shape accuracy by the fifth grinding operation with the fourth correction of cutter location data. The machine has been also installed in a constant temperature room of ±0.5K in variation.
To evaluate the hardness of Diamond-like carbon (DLC) thin films formed by ion beam assisted deposition, the indentation load-depth behavior of some materials were tested using an ultra-micro hardness tester with a Vickers indenter. The hardness constants related with the Vickers hardness and the elastic modulus of the materials used were defined, similar to Meyer's law. The evaluation using the hardness constants was applied to TiN thin films of three different thickness on glass plate and the raw hardness of TiN thin films which was independent of film thickness was determined. Furthermore, the hardness of DLC thin films formed with different methods on two substrate materials was discussed. From these results, it was concluded that the hardness evaluation method for the thin films in this paper was useful.
In order to predict the cutting performance of grooved rake face tools quantitatively, the orthogonal and steady-state metal cutting processes are analyzed by a finite element method. The finite element method specially developed in this study can be applied to the tools having various kinds of rake face geometry. It is made clear analytically that when the grooved tools are used, the shear angle increases and the cutting temperature and cutting forces decrease because the tool-chip contact is restricted to a small area. The chip curl radius obtained by the analysis decreases with an increase in the depth of cut. The analytical results obtained above are in good agreement with experimental results. It is also made clear analytically that the chip curl radius decreases with an increases in the height of the back wall while the cutting forces seem to be independent of the back wall height.
The measurement of errors in the axis of rotation is of growing interest, because spindle is the most important part of ultra-precision machine tool and precision measuring instrument. In most of the measuring methods for precision spindle, capacitive type displacement transducers are used to measure relative displacement between spindle and transducers. However, the electrical noise due to NC controller or spindle motor affect accuracy of these measuring methods. In an attempt to reduce electrical noise and to increase the accuracy, an optical spindle error analyzer has been developed. At first, principle of the measuring method and optical system layout are described in detail. Then, the result of the consideration on measuring sensitivity is shown.
This paper deals with the automatic compensation of analog data measured by the circular test method developed by one of authors. In the circular test method, a 2-dimensional displacement probe, a master disk and an analog XY recorder are needed. The trajectory recorded on the XY recorder does not coincide with the actual trajectory. In this paper, at first, the analog data detected by the 2-dimensional probe is precisely observed, and some problems to be solved are investigated. In addition, a new trigger method to acquire the digital data automatically is proposed. Through the experiments, it is found that-there are some problems to be considered in the acquired data digitally; those are the effects of trigger method, friction between a stylus and a master disk and acceleration of axis. These effects are automatically compensated in the computer and the trajectory processed by the proposed method is compatible to the other method such as the rθ method.
The light intensity diffracted from superimposed dual transmission gratings having uniform pitch is sensitive to their relative lateral displacement. In the case that change of light intensity is used for measurement of lateral displacement, the intensity change has some distortion (deviation from sinusoidal variation) and is affected by changes in the air gap between two gratings. This paper shows that an index grating with modulated pitch can be used to reduce signal distortion. The index grating does not have uniform pitch lines but has periodical patterns of UN-uniform pitch lines. Experiment shows that the signal distortion is reduced and is almost independent of the gap. This method can reduce interpolation error under ±0.125% of grating pitch, and is effective for an encoder in precision machining.
From the economical efficiency, the manufacturing system in which the mentality and flexibility of human operators are utilized positively is occasionally superior to a fully-automated system. In order to take the manual operation into a manufacturing system reasonably, the operation should be rightly appreciated and the arrangement in the system should be fully investigated. In the well-arranged system, the operators can become swiftly accustomed to their job, their performance can be high and their fatigue can be low. The purpose of this research is to clarify the characteristics of the manual operation systematically. To do this, a virtual manually-operated-machine or simulator has been developed. By using the simulator, it is possible to monitor the behavior of the operator precisely. In the present paper, as the first step to the research, operating efficiency and fatigue of the operators have been analyzed experimentally, when they got operating force as auditory information besides force perception. The examined operation is a cut-off turning with a virtual lathe. As the results, the auditory feedback is significantly effective in improvement of efficiency and reduction of fatigue, though the effectiveness is different according to timbre of the feedback sound.
Pneumatic cylinders are used in factories because of easy handling, and large power. But the usage manners of the pneumatic cylinders are in many cases, under ON-OFF control. The stop positions of pneumatic cylinder are fixed beforehand so there is no flexibility in positioning. In the case of positioning, mechanical stoppers are used, which cause a large impact force to the equipments. The reasons why the position and velocity feedback control is not realized in the pneumatic cylinder are the characteristics of air compressibility and the lack of high performance valves. Recently some closed loop control systems are developed, in pneumatic system using proportional valves or other fast response valves. But commonly their cost performance is not so good, and the system is rather complicated. In this report, a new positioning and force control method is proposed, which uses ultrasonic valves under PWM control. The ultrasonic valve is switched by ultrasonic sound produced electrically actuated vibrator, so it has simple structure and the cost is low. In this report the response time of the ultrasonic valve is estimated experimentally. A test experimental equipment of closed pneumatic positioning system is constructed. The measured response time of ultrasonic valve is about 40 ms. The total performance is estimated by numerical simulation and by some experimental results, under the restriction of the valve response time.
This paper treats the intelligent inspection system for particle suspension by using a neural network. The automated inspection system for particle suspension by an image processing has almost not been reported in the past, because of the complexity of image processing of water with particles. If the features of image processing data of particle suspension are recognized by a vision system and a neural network, the degree of surface contamination before and after washing processes will be clarified in relation to the water analyses, and also the deterioration process of many kinds of fluid, such as lubricants and finishing compounds will be cleared. The objectives of the paper are to analyze the water image by using the texture analyses, to investigate the limitation of image recognition for concentration of particles in water, and to construct the neural network system which' is able to estimate the concentration of particle suspension. It is found that the features of image data of the liquid containing particles can be decided by the texture analyses. As the results, it is possible to construct the neural network system which is composed of the features of water image as input data and the degree of particles concentration as output data.
This paper describes the practical design method of an advanced servo system for industrial robot manipulators, where it includes a disturbance and velocity observer. At first, it is assumed that the feature on frequency response of the robot is approximated to the feature of two mass mechanism. Actually this fact is confirmed by the some experiments. On the other hand, it is insisted that the actual servo system should be simple for industrial use. And the observer is designed for the load which has the feature of single moment of inertia. On the assumption that there is a difference between these features, it is introduced that the servo system can be effectively used if only the qualified gains are selected considering low-stiffness. And then, the special relation between the frequency analysis and the pole allocations are shown. Finally, the experimental results are introduced.