Direct torque control with an optimized observer for multi-machine systems J. Belhadj, I. S. Belkhodja, M. David and B. de Fornel Eur. Phys. J. Appl. Phys., 33 1 (2006) 23-33 Published online: 18 January 2006 DOI: 10.1051/epjap:2006004