In the context of the multiple mobile robot system developed by our research group, we have implemented what we call virtual constraints, that is, user-defined lines that affect the behavior of the elements of the system. Experiments (herding and assembly tasks) show that virtual constraints help the user to control multiple mobile robots.
This paper deals with the stiffness analysis of a linear motion guide system using in machine tool table considering the crowning shape of guide block end portions. At first, the Hertz constant between rolling body and raceway sufaces is discussed, then the equilibrium equations for the external forces and moments, acting on the origin of the coordinate system as the statically equivalents and the rolling body loads distributed in each guide block are derived in accordance with the radial and lateral displacement, pitching, rolling and yawing angle. As the result, 5 non-linear simultaneous equations with 5 unknowns which are solved by using Newton-Raphson method are introduced.
Recently lasers have been recognized as an energy source and laser-beam-enhanced chemical machining methods have been accepted in the industry as a machining technique. This review describes chemical machining performed using laser beam irradiation, in particular, chemical processing in an aqueous environments. The topics include ceramics etching in water, and carbon film synthesis on a water substrate from methane.
It has been difficult with an automated production system to achieve compatibility between productivity and adaptability in the area where production volume and period are uncertain. Recently we have developed a new automated production system, APS (Adaptive Production System), by studying how a manual-operation system responds to uncertainties, and applied it to an automotive starter assembly line. The number of machines in the system can easily be increased or decreased according to the production volume fluctuation. The highlighted topic is integration of human-social functions such as autonomy, cooperation, and succession into a conventional automated line. As a result, we have realized an epoch-making automated production system which can change its production capacity between 4 700 and 61 000 units/month through a rapid transformation of system structure, while the automation ratio of this system is equivalent to that of the conventional transfer line whose production volume and period are certain.
This paper proposes a new feedforward controller called the direct velocity and acceleration feedforward controller (DVAFF) to improve the tracking performance. The controller is adapted to both minimum phase system and nonminimum phase system and it can also take the practical driving capability of actuator and saturation of D/A converter into account by tuning their gains. Simulation and experiment results show that the proposed new DVAFF scheme can effectively improve the motion accuracy.
Polycrystalline diamond (PCD) cutting tools are widely used for cutting non-ferrous metals, wood, and inorganic materials. Previously, PCD tools were used solely to finish such materials, because the PCD cutting tool was unable to withstand the high cutting force involved in rough machining. We have succeeded to develop tougher grade of PCD (SUMIDIA DA 2200). The high strength of SUMIDIA DA 2200 is almost equal to that of cemented carbide, and eliminates breakage of the cutting edge even under the most sever conditions.
The aim of this study is to evaluate the cutting edges on a grinding wheel surface under various dressing conditions. Therefore, the surface topography of the entire periphery of the grinding wheel is measured in three dimensions using a laser stylus unit on the machine table. In the present report, we investigated positions, numbers and profiles of the cutting edges on the grinding wheel from measurement results under various dressing conditions. As a result, it is clear that there are few cutting edges near the outermost periphery ( the depth of 3 mu m from the maximum height among the cutting edges) of the grinding wheel. In particular, the lead in dressing the wheel has influence on the surface topography of the grinding wheel. As the dressing leads decrease, the number and the vertical angles of the cutting edges increase.
Working on the development of a piezoelectric element that provides high displacement at a low cost, we have come up with a rolled type piezoelectric element as a test model. Its simple design and the ease with which to provide lead wires from electrodes means reduced production costs as compared with those of conventional multilayered type piezoelectric elements. This paper describes its construction and displacement capability.
A new dressing method for superabrasive wheels, named "Magnetic Abrasive Polishing assisted dressing method" or "MAP-dressing method" in short, is proposed. Dressing ability of the MAP-dressing method was investigated on various superabrasive wheels using some kinds of magnetic abrasives. As a result, it became clear that the proposed method is useful for the wheels containing superabrasive grits of #170-3000 mesh in terms of dressing efficiency and uniform protrusion of superabrasive grits from matrix metal.
This paper describes a theoretical model for the prediction of cutting forces and machining error in ball end milling of inclined flat surfaces. The instantaneous cutting forces are evaluated based on the uncut chip geometry and the properties of tool and workpiece material. The theory of oblique cutting is employed in this analysis, since the cutting edge of the ball end mill Is helical. The machining errors at various parts of the machined surface are evaluated based on tool deflections. This analysis is carried out for various tool-feed directions along the inclined surface The effects of various cutting conditions on cutting forces and machining error are investigated and discussed. In order to verify the theoretical results, experiments are carried out in ball end milling of 0.5% carbon steel. The experimental and theoretical results compare fairly well.
Excimer laser mask projection techniques have been developed and used to manufacture directly miniature thin film devices for the electro-manipulation and separation of bio-particles using travelling-wave dielectrophoresis effects. Multi-level devices with 10μm-wide electrode structures have been fabricated by using excimer laser ablation techniques in both static and mask scanning modes of operation. A prototype device produced in this manner has been used to identify viable and non-viable oocysts.
A technique for simulating the surface formation of a diamond grinding wheel is developed in order to evaluate typical characteristics of the surface topography. The simulation includes four procedures: simulating the:grains with long and short diameters according to those actual distributions in a mesh size; distributing the grains into the bond area of the wheel based an a random or uniform manner;truing and dressing the wheel surface to make cutting edges under a grain protrusion ratio as the criterion for grain remaining or falling off; and evaluating characteristic values of the surface topography like density of cutting edges. The results showed that the surface topography simulated by the random grain distribution resembled the actual one when maximum grain protrusion ratio was 30-35% in a resinoid bonded wheel and 35-40% in a metal bonded wheel The density of cutting edges, the length of cutting edges per unit area and the extent of maldistribution of grains were determined on wheels with grain sizes from coarse to fine.
Pointer-type micro strain gauges have been implemented by applying the standard CMOS (Complementary Metal Oxide Semiconductor) process. Micro strain gauges can be used to determine residual strain of thin films. By using an identical post-processing on the same chip, this work fabricates three kinds of micro stain gauges to measure residual strain of three CMOS thin film materials. The maskless post-processing requires only wet etching. The experimental results of residual strains for CMOS thin films of silicon nitride, silicon dioxide (compression) and aluminum (compression) are 1.665x10(-3), -2.667x10(-3) and -0.510x10(-3) respectively.
