Direct Torque Control of Bearingless Induction Motor

Due to the limitations such as complexity,unsteady torque and nonlinearity in the gap flux direction algorithm,this paper introduces the direct torque control in the bearingless induction motor decoupling control.In this paper,small signal model is used to analyze the influence of torque current ripple on Maxwell force and a space vector pulse width modulation(SVPWM) direct torque control algorithm is studied further.The outputs of torque PI modulator and flux PI modulator are flux phase angle increments and amplitude increments respectively and a regulator for phase angle increment is adopted to solve the disturbance problems in torque loop and flux loop.The total harmonic distortion(THD) of SVPWM is analyzed in this paper.In the experiments on a bearingless induction motor,DSP(TM320F2812) was adopted to realize the suspending control which based on the two direct torque control(DTC) algorithms.The experimental results validate that the studied algorithms have a better performance in reducing disturbances of current and torque.Thus the suspending performance of motor is improved.