Magnetorheological (MR) fluids are materials that change their rheological behavior upon applying a magnetic field. They have been promising as functional fluids that can improve the properties of mechanical systems. We have developed an actuator using MR fluid. In the previous paper, a method of designing MR-fluid actuators was proposed on the basis of magnetic circuit theory. The basic experiments were carried out and static properties that agreed well with the design were obtained. However, the transient response, which was not considered in the design phase, was not very fast. In this study, we investigate the dynamics of the MR-fluid actuator and aim to improve the response. The transient magnetic analysis is examined in consideration of the eddy current. Two approaches to improving the response are proposed. Finally, we realize a much faster MR-fluid actuator.
This paper introduces a device for enhancing detection of surface undulation through active touch. This device, which we call a "tactile contact lens," is composed of a sheet and numerous pins arranged on one side of the sheet. Experimental results show that a small bump on a surface can be detected more accurately through this device than by bare finger and than through a flat sheet. A mathematical analysis of this phenomenon suggests two possible explanations for this phenomenon. One lies in the lever-like behavior of the pins. The pins convert the local inclination of the object surface into the tangential displacement of the skin surface. The second is the spatial aliasing effect resulting from the discrete contact. Due to this effect, the temporal change in the skin surface displacement is efficiently transduced into the temporal change in the skin tissue strain. The results of this analysis are then discussed in relation to other sensitivity-enhancing materials, tactile sensing mechanisms, and tactile/haptic display devices.
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