There are many studies on hardware and software experiments to control a modular robot. The modular robot consists of homogeneous or heterogeneous simple modules. A feature of them is that the modular robot behavior obtained by an each module movement is based on local communications between linked modules. This study focuses on a computer simulation for a virtual modular robot obeying physics laws. This simulation aims at achieving given tasks autonomously for the virtual modular robot in specific circumstances. Our goal is to acquire a control system in evolution for the virtual modular robot and to analyze and evaluate their behavior.

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In order to achieve high torsional stiffness and uniform force distribution among rolling elements against load torque, a new type of ball reducer having no eccentric input cam has been designed. In the formulated reduction principle, wave motion (cycles of rise and fall) of rolling element is described as an elliptical motion along the fixed cam locus, and the reduction cam advances a distance of one tooth at each one wave motion. This one wave motion is imparted by m(=1,2,...) turns of the input cam. If the number of lobes of the input cam is defined as the number of wave motions imparted by one turn of the input cam, then the number of lobes is considered as 1/m. The locus of the input cam is the looped curve of m turns, then the self-intersections of the looped curve occur at m-1 points. Occurrence of interference at the intersections was avoided by employing ball as rolling element. In this paper, the number of lobes of the input cam, 1/m, is assumed to be 1/2 as the simplest configuration. Based on this assumption, the suitable value of the design parameter which gives allowable pressure angle is analyzed. The conditions that can avoid undercutting of the reduction cam are also discussed. Furthermore, the minimum wall thickness between adjacent teeth of the fixed cam is shown.

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Using a new type of linear motor which has some advantages over conventional linear motor, we developed an ultraprecision positioning device whose stage was supported by linear ball guide ways. With very rigid structure of the device, the stage displacement was fed back by PI-D control using linear encoder of 0.034nm resolution. In this study, much attention was paid to the electric control system. It can compensate for the disturbance of induced electromotive voltage, which is generated in proportion to the stage velocity. We studied how the equivalent time constant T of control system has influence on the motor electric current I_o and stage displacement deviation Δx, when the command of stage displacement x_r was kept to be zero. The following results could be obtained. 1)With decrease of the time constant T of the current control system, the change of motor current I_o became smaller and at the same time the change of stage deviation Δx became smaller. 2)At the smallest time constant T of the current system, the displacement resolution of 0.2nm could be obtained. 3)There is a possibility obtaining the displacement resolution of less than 0.1nm with more decrease of T.

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Linear actuators driven by ball screw mechanism lead to non-linear relations between the linear motion of the nut and the rotary motion of the screw shaft when the ball screw drive is reversed even if the ball screw is preloaded with a double nut to remove backlash between the screw shaft and the nut. The behavior of the ball screw mechanism that is referred to as “lost motion”, can contribute positioning errors of linear actuators.
This paper deals with a relationship between the lost motion and the ball behavior of the X-table which is composed of a preloaded precision ball screw and a couple of linear air bearings, and ball rolling behaviors. Ball rolling behavior is measured by the gap sensor which is inserted into a hole which is bored in the perpendicular to the outer surface of the cylindrical nut and is located on the opposite side of the ball circulation tube. The results are summarized as follows : (1) “Ball wedging” and ball wedging direction can be measured by developed experimental device. (2) The ball wedging direction is reversed when the ball screw drive is reversed in two-point contact ball screws. Therefore, the differences between forward stroke and backward stroke in ball rolling speed are occurred. (3) It is considered that the lost motion is produced in two-point contact ball screws when the ball wedging direction is reversed.

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Hobbing is a kind of plain milling, in which the sectional area of a chip is continuously changing during cutting. Hob wear is considerably affected by the chip length and the thickness. In this paper, after developing a method to divide the cutting length of a chip into four equal parts, investigation were carried out on the distribution ratio of hob wear when cutting each of the parts in the cases of dry cutting, MQL system and flood using TiN- and (Al,Ti)N-coated tools. Experiments were conducted by simulating hobbing by fly tool cutting on a milling machine. As a consequence, the following points were clarified : (1) When using the TiN-coated tool, the distribution ratio of wear is greatest at the end of producing a chip in the four parts in the cases dry cutting and MQL system. However, it is almost the same in the four parts in the case of flood. (2) With the (Al,Ti)N-coated tool, the distribution ratio of wear decreases from the beginning to the end of cutting a chip in the cases of dry cutting and MQL system, but in the case of flood, it shows almost the same value in the four parts.

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High-aspect-ratio microdrilling of borosilicate glass has been demonstrated by the forth harmonic of nanosecond Nd:YVO₄ laser. In this paper, we investigated about the influence of the pulse width on the hole profile. The pulse width was expanded by splitting the laser beam and mixing after passing through optical passes with different length. Firstly, the holes drilled with various polarized beam. As a result, depths of the holes drilled with different polarization of the beam were same. Then depths of the drilled holes with different pulse width were measured. Deeper holes were obtained with faster pulses when the deep holes were drilled. However, no clear difference was observed when the drilled holes were shallow. The profiles of the holes drilled with different pulse width were measured. As a result, the profiles were almost same around the entrance. On the other hand, the diameters of the holes drilled with slower pulses were a few μm smaller than that with faster pulses around the bottom. It was shown that pulse width influenced more when deep holes were drilled.

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In this study, tension, bending, torsion, and compression tests were carried out to examine the effect of loading mode on fracture strength of SKH51 (AISI M2) high speed tool steel. In addition, the fracture mechanism of each loading mode was examined using scanning electron microscope. Specimens were tempered up to 650°C after solution treatment in the range from 1160°C to 1260°C. It was shown that bending strength was higher than tensile strength up to 1240°C. This phenomenon was explained by introducing the concept of effective volume. Brittle fractures occurred in both tension and bending. Quasi-cleavage fracture patterns were observed on fracture surfaces, and primary carbides were found at the origin of fracture. On the other hand, plastic deformation occurred in torsion and compression, and dimple patterns were observed on fracture surfaces. It was proved that the deformation characteristic of high speed tool steel was dependent on hydrostatic stress component.

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Cemented carbide has many excellent properties like high strength, high hardness and high wear-resistance. However, it is often difficult to apply conventional surface finishing or surface modification methods because of its excellent mechanical properties. The purpose of this research is to improve the surface characteristics of cemented carbide by large-area electron beam irradiation. The possibilities of surface smoothing and surface modification were discussed with varying the energy density of electron beam and the number of pulse. The following results were obtained from the experimental analysis. The frequency of surface roughness of surface irradiated by large-area electron beam became lower, and glossiness was higher than those of initial surface. The contact angle of water on electron beam irradiated surface was higher than that on initial surface, which means that the surface has high water repellency. Oil extension area investigated for evaluating lipophilicity was smaller than that of initial surface. The separation force of molded resin measured for releasability evaluation could be reduced by large-area electron beam irradiation. From these experimental results, it was made clear that the surface characteristics of cemented carbide can be improved by large-area electron beam irradiation.

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This paper presents an optimization method for facility maintenance scheduling in re-entrant flow shop using Multi-start and Greedy method. The proposed approach regards maintenances as jobs within limits of starting and finishing time, so that the schedule can realize not only proper maintenance to prevent facility troubles but also high productivity with short scheduling time. A case study is presented for a semiconductor manufacturing system, in which it is difficult to find a proper plan because of complex process flow so that the jobs often re-enter into the facilities. The feasibility of the proposal is discussed comparing to Lagrangian decomposition coordination method in the first; the proposed method can realizes feasible solutions within acceptable calculation speed in real. Also, the feasibility is studied in a real semiconductor manufacturing system and confirmed the proposed method can gain its productivity.

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Vibrations of a tool or a workpiece in cutting shorten tool life and deteriorate a surface roughness. In this research, we propose a method to reduce vibrations of the workpiece at a cutting point. An algorithm that generates a cutting path to minimize workpiece displacements at a cutting point is developed. In this algorithm, the cutting path is generated with changing feed directions, tool posture and material removal process by considering workpiece compliance matrices and cutting force vectors. Feed directions and tool posture are changed to control the direction of the cutting force vector. Material removal process is changed to control the change of the workpiece compliance. FEM (Finite Element Method) is used to calculate workpiece compliance matrices. SVD (Singular Value Decomposition) is used to calculate the direction which has the lowest compliance in the workpiece compliance matrices. Minimum workpiece displacement at a cutting point is calculated from these calculated results. The algorithm is applied to the cutting path of end milling for a simple bar and the cutting path is compared with two conventional cutting paths by conducting a simulation and a cutting test. As a result, mean values of workpiece displacement were reduced by applying the algorithm.

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