Tactile sensor array using microcantilever with nickel-chromium alloy thin film of low temperature coefficient of resistance and its application to slippage detection

A tactile sensor consisting of microcantilevers has been fabricated using the NiCr-thin-film strain gauge with low noise by surface micromachining and the slippage has been detected by using the fabricated tactile sensor array. The NiCr alloy thin film of Cr: 75 wt% has very low temperature coefficient of resistance (TCR) and is employed to suppress the temperature noise and drift. The fabricated tactile sensor with the NiCr thin film (Cr: 75 wt%) has linear dependencies of the resistance on normal and shear forces, and shows lower noise and temperature drift than that with conventional NiCr (Cr: 20 wt%) film. Normal and shear forces measured by fabricated sensor well coincide with applied forces with errors of 3-3.5 kPa. Moreover, the gripping status of the robotic hand was detected by using fabricated tactile sensor array, and the slipping condition can be judged at the rate of 76.5%.