Digital signal processing for biaxial position measurement with a pyroelectric sensor array

This paper proposes a new full digital approach to estimate biaxial position with a pyroelectric sensor array. Previously developed analog interface shows its limits in calibration procedure, requiring several trimming adjustments. A DSP-based hardware has been developed to experimentally evaluate three digital methods: radial basis function neural network (RBF), best fitted plane (BFP) and look-up table (LUT) in the least mean square error sense. Experimental results show that no dramatic improvements are obtained by RBF despite the long training required and the external PC support for weights calculation. BFP reaches performance comparable to the analog processing system using only 9 calibration points, but the best tradeoff has been found with the LUT technique. Actually, with a 64-points calibration set, LUT gives a RMSE of 0.5% FS, offering a valid in-circuit compensation of array structural defects.