Control systems are small components that control the behavior of larger systems. In the last years, sophisticated controllers have been widely used in the hardware/software embedded systems contained in a growing number of everyday products and appliances. Therefore, the problem of the automatic synthesis of controllers is extremely important. To this aim, several techniques have been applied, like cell-to-cell mapping, dynamic programming and, more recently, model checking. The controllers generated using these techniques are typically numerical controllers that, however, often have a huge size and not enough robustness. In this paper we present an automatic iterative process, based on genetic algorithms, that can be used to compress the huge information contained in such numerical controllers into smaller and more robust fuzzy control systems. © springer-Verlag Berlin Heidelberg 2007.