Subsequently, in 1985, by Professor Ruhr University M.  Depenbrock[5]  first proposed the theory of direct torque control, and then again it extended to weakening speed range. Compared with vector control technology, direct torque control largely solved the vector control of three-phase induction motor characteristic susceptible to change motor parameters for this problem. The birth of Direct Torque Control, with regard to his own novel control thought, concise system architecture, excellent static and dynamic performance have had widespread concern and have had a rapid development. At  present, the technology has been successfully applied in the electric locomotive technology[6]. After the 1990s, with the development of microelectronics and computer control technology, high speed, high integration, low cost microprocessors and the advent of commercialization, the all-digital AC servo system became possible. By computer control, the motor speed performance has greatly improved, so that complex vector control and direct torque control can be achieved, simplify the hardware, reduce the cost and improve the control precision. In addition, changing the control strategy, and the model parameters correction control has become easier, thus, greatly improving the flexibility, reliability and system availability. In recent years, advanced digital AC servo system, a number of companies have introduced chip specifically for motor control can quickly complete the system speed loop, current loop and position loop rapid adjustment precision and complex vector control[7], to ensure that the algorithm for motor control, such as direct torque control, vector control, variable structure control, neural network control high-speed, high-precision finish.. Vector Control Simulation of Surface- mounted Permanent Magnet Machine(3):http://www.751com.cn/yingyu/lunwen_41335.html