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We are developing an optical three-axis tactile sensor capable of acquiring normal and shearing force, with the aim of mounting it on a robotic finger. The tactile sensor is based on the principle of an optical waveguide-type tactile sensor, which is composed of an acrylic hemispherical dome, a light source, an array of rubber sensing elements, and a CCD camera. The sensing element of silicone rubber comprises one columnar feeler and eight conical feelers. The contact areas of the conical feelers, which maintain contact with the acrylic dome, detect the three-axis force applied to the tip of the sensing element. Normal and shearing forces are then calculated from integration and centroid displacement of the gray-scale value derived from the conical feeler's contacts. To evaluate the present tactile sensor, we have conducted a series of experiments using a y-z stage, a rotational stage, and a force gauge, and have found that although the relationship between the integrated gray-scale value and normal force depends on the sensor's latitude on the hemispherical surface, it is easy to modify the sensitivity according to the latitude, and that the centroid displacement of the gray-scale value is proportional to the shearing force. When we examined repeatability of the present tactile sensor with 1 000 loading-unloading cycles, the respective error of the normal forces was 2%.

This paper describes design of a tendon-driven articulated finger hand that has similar properties to those of a Remote Compliance Center (RCC) device, i.e., it generates resolved displacements for disturbance forces applied to a grasped object and it can also adjust the elastic coefficients semiactively using the nonlinear elasticity of tendons. After introducing some basic results with respective to a tendon-driven mechanism, the stiffness matrix which relates the restriction forces applied to a grasped object to the small displacements of the object is derived. It is shown that more than six tendons are necessary, for each finger to adjust all elements of the stiffness matrix using only the nonlinear mechanical elasticity of tendons. After that, the wiring and pulley system is designed that cannot only drive the fingers freely without loosing the tension forces but also can diagonalize the stiffness matrix and adjust the elements. It is also shown that the hand can grasp different sized objects without losing the property using the tendon redundancy.

A capacitance-based void fraction sensor has been developed for the rocket or airbreathing engines, which is simple and do not disturb the flow. Typical conventional sensors usually have two concave electrodes mounted on the outer wall of the dielectric tube. They are relatively low accuracy if they have a noise shield; the maximum measurement error is over 30% in our research. The aim of this study is to improve the measurement accuracy while keeping the advantage of simplicity, mountability and non-intrusive characteristics. A theoretical formulae and electromagnetic field analysis, EFA, are used to design the sensors and are compared to an experiment using air/silicon-oil mixture flow. As the result, a newly developed asymmetrical type sensor which consists of asymmetric flat electrodes with side walls shows good performance; the inaccuracy between true void fraction and measured void fraction is 6% for the stratified flow.

Designing mechanical systems by means of special-purpose languages is very effective because they can define objects preciesly. However, this causes serious problems. First, the amount of description is very large in the case of designing complex systems. Second, those languages are not suited for modeling objects at higher abstraction levels. To solve these problems, this paper presents a novel description language for mechanical design called MODEL (Mechanical-design-Oriented DE scription Language). MODEL is designed in order that the designer's intentions can be efficiently reflected in the specifications of mechanical systems. We introduce a new concept, design granularity, so that designers can model objects of a mechanical system at different abstraction levels. Moreover, to reduce the amount of description, we use knowledge bases for mechanical design as a library for MODEL. The design process with MODEL is discussed in detail to clarify the capabilities of the language.

In this paper, we apply stress stimulation to a rabbit's tibia under the same conditions as the previous paper using an improved apparatus in which the applied load is measured and controlled automatically by a personal computer. We apply not only compressive load but tensile load to the rabbit's tibia in order to clarify the difference in the influence on bone formation. The bone formation around the circular defect is estimated accurately by using a image processing technique. We discuss the relationship between the bone apposition and stress stimulation quantitatively from the experimental result. Furthermore, the computer simulation of the bone apposition in the experiment is carried out using an algorithm based on the theory of time-dependent bone remodeling proposed by Beaupre' et al. and the effectiveness of the theory is discussed compared with the experimental results.

The contact stress analysis of elastic bodies is important for mechanical engineering in areas such as friction, wear and fatigue. The point-matching method is the well-known analytical model that satisfies Hertzian-contact theory. However, the point-matching method has critical problems, i.e., large amounts of computation time and memory are required as the number of cells increases. Although there have been many studies on its accuracy to date, there are a few studies on efficient processing of the point-matching method. This paper proposes an efficient discretization method for the contact region to accelerate processing time and save memory space in the point-matching method