Force display is an important element to set up a user-friendly man-machine interaction system (e. g. haptic interface system). To display force easily and conveniently by means of a simple mechanism, we focus attention on the static characteristics of an omnidirectional mobile robot. This paper presents development of a prototype of a planar 3-DOF wheeled motion base consisting of omnidirectional mechanism, and the some experiments to estimate performance of the force display. In addition, for realizing a widely applicable motion base, a spacial 6-DOF motion base mechanically-expanded from the planar 3-DOF one is proposed and prototyped.
Copper plates of 1 mm in thickness were joined with a solder layer (60 mm in thickness) of Sn-3.8 mass% Ag-1.2 mass% Cu alloy, and then subjected to the shear fatigue testing. At required numbers of fatigue cycles, the specimen was subjected to the acoustic microscopy to measure the shape and the size of the bonded region. After fatigue testing, the fracture surface was observed through scanning electron microscope to verify the distribution of fine penny-shaped cracks in the bonded region. The area of the bonded region estimated from the acoustic image monotonically decreased with increasing number of fatigue cycles. The larger the initial bonded region, the longer was the fatigue life. The density of the penny-shaped crack in the bonded region decreased with the distance from the edge of the bonded region, and increased with the number of fatigue cycles. The average size of the penny-shaped crack slightly increased with the distance from the edge of the bonded region, but showed no dependence on the number of fatigue cycles. The numerical calculation was also conducted with a simple model to obtain the bonded area as a function of the number of fatigue cycles. The calculated change in the bonded area with the number of fatigue cycles agreed well with the estimated one from the acoustic image. Calculated distributions of the density and the average size of the penny-shaped crack explained the change in the measured ones with the distance from the edge of the bonded region.
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