In situ measurement of friction on curved surfaces

In situ measurement of frictional properties, particularly of human skin, is challenging. A major challenge is that the measured surface may be curved and oriented arbitrarily relative to the measurement device, making it difficult to obtain accurate and reliable friction estimates. Here we propose a method to simultaneously estimate the orientation of the surface during friction measurements, using a custom-made hand-held tribometer. The method accounts for the position and orientation of the tribometer relative to the shape of the measured surface. Our simple calibration method allows lightweight tribometers to be built with cheaper materials like plastic, without sacrificing accuracy.