The performance of servo control system determines the reliability and stability of VTR (video Tape Recorder), and enables ultimately VTRs to record and replay video signal accurately.

And after the discrete mathematic model for stability analysis and design a set of military reinforcement machine load of embedded system with ac servo device combined with the dynamic control system.

A design method of variable structure control for the d. C. servo system is proposed. Also the sliding state stability of the system is analyzed.