%R 10.1109/CDC.2012.6426755 %B Proceedings of the IEEE 51st Annual Conference on Decision and Control (CDC), 2012 %X In this paper, a piecewise-affine direct virtual sensor is proposed for the estimation of unmeasured outputs of nonlinear systems whose dynamical model is unknown. In order to overcome the lack of a model, the virtual sensor is designed directly from measured inputs and outputs. The proposed approach generalizes a previous contribution, allowing one to design lower-complexity estimators. Indeed, the reduced-complexity approach strongly reduces the effect of the so-called "curse of dimensionality", and can be applied to relatively high-order systems, while enjoying all the convergence and optimality properties of the original approach. %L eprints1471 %D 2012 %K Complexity theory; Estimation; Observability; Sensor systems; Vectors; Voltage control. %A Matteo Rubagotti %A Tomaso Poggi %A Alberto Bemporad %A Marco Storace %I IEEE %O 51st IEEE Conference on Decision and Control December 10-13, 2012. Maui, Hawaii, USA %P 656 -661 %T Piecewise affine direct virtual sensors with Reduced Complexity