M. Silva Significant changes have been occurring in industrialized countries since the Second World War. Production is moving towards sophisticated high- qUality products, economy of scale has been replaced by economy of scope, jerky demands are progressively replacing steady demands, and competi- tiveness is becoming a worldwide phenomenon. These trends require highly automated manufacturing systems with small set-up times and high flex- ibility. As a consequence, implementation and running costs of modem manufacturing systems are drastically increasing, whereas their fields of application...