Flexible Tri-Axis Tactile Sensor Using Spiral Inductor and Magnetorheological Elastomer

This paper describes a flexible and soft tactile sensor that measures the tri-axis force based on inductance measurement. The proposed sensor has four spiral inductors printed on a flexible circuit board and a mounted cylindrical elastomer (silicon rubber). A disk-shaped magnetorheological elastomer (ferromagnetic marker) is embedded in the cylindrical elastomer and its 3-D displacement is estimated by monitoring the inductance changes of the four inductors. In this paper, we investigated the relationship between the applied tri-axis force and inductance changes. Our results can be summarized as follows: 1) the inductance changes of the four inductors were monotonic and linear against the applied normal and shear force; 2) the applied tri-axis force could be estimated well with linear functions of the sum and difference of the measured inductances; and 3) the estimation error of the tri-axis force increased when a larger force was applied and/or faster contact speeds were used.