One of the applications of multi-phase machines is series multi-phase system and feeding them from a single multi-phase inverter, in this way for some special applications the cost is decreased. Up to now the standard control of such servo drives has been vector control. However because of coupling dynamics and unmeasurable state variables, control of such motors is complicated. The vector control is implemented to control torque and flux separately, but this method is not capable to control torque and flux during the transient of the flux; thus using robust nonlinear methods are necessary especially in series multi-motors drives with a common dc-link. In this thesis, using state feedback linearization and sliding mode control, a two series six-phase servo drive is designed. In addition, a suitable method is proposed for implementation of a six-phase space vector PWM to feed a two-motors system. To investigate the performance of the proposed control system, a real-time computer based system is designed and implemented. The comparison of the simulation and practical results shows the compatibility of these results and the desired performance of controllers and estimators. Moreover, to show the performance and feasibility of the proposed control method, as an example, these drives are used in tension and speed control of a web winding system with three motors. The web winding system is an integrated system included some motors to traort and process elastic materials, the speed and tension control in different sections of this system is very important. Because it is not possible for us to practical implement of the web winding system, in this thesis, the theoretical and simulation results of this example are illustrated. The contributions of this thesis are: using nonlinear methods for series drive control, design of a space vector PWM to generate two independent frequencies, using of series motor drives in web winding systems and design of a robust nonlinear controller for web winding system. Keywords 1- multi-phase machines 2- multi-motors systems 3- nonlinear control of electrical drives 4- space vector PWM 5- web winding system