Development of an Innovative Magnetorheological Fluids-based Haptic Device Excited by Permanent Magnets

A number of haptic displays based on smart fluidic materials such as electrorheological (ERFs) and magnetorheological fluids (MRFs) have been fabricated. These displays are relevant to medical virtual environments where it is important to create realistic simulations of soft tissues with varying stiffness. In this paper a new haptic device is described that was designed in consideration of the limitations of an earlier MRF display. The new prototype consists of 400 permanent magnets (PMs) arranged in a 20x20 array that is underneath a chamber filled with MRF. The magnetic field within the fluid is controlled by 400 PM stepping motors that move the magnets vertically. The magnetic behavior of the device was simulated using FEM which indicated that its spatial resolution was substantially improved when compared to the earlier prototype and that objects as small as 10 mm can be rendered. The device was fabricated and assembled and measurements demonstrated the accuracy of the FE model. Its novelty is demonstrated by the increased intensity of the magnetic field produced and the enhanced spatial resolution. These features will enable the dynamic presentation of haptic information such as object shape and compliance which will be characterized in future psychophysical experiments.