The Research Of Sensoless Control Method Of The BLDC Motors

The brushless direct current thruster motor system is replacing the brush direct current motor system as the thruster motor of underwater vehicles. The underwater vehicle requires the thruster motor has high reliability ,so it is important to research the brushless thruster motor system's reliability. For the control method of brushless DC Motor, it is very important to check that passing turns sub-position. But the usage position sensor of brushless DC motor spread the corrupt practice increasingly. For the sake of better in the industrial realm application, the sensorless brushless DC Motor is put forward, and carried on an extensive and thorough research. This dissertation will carry on a related research of the problem which current research has meet.About the simulation of BLDCM system, Based on the mathematical model of BLDCM, a novel method for modeling and simulation of BLDCM system in Matlab has been proposed. In Matlab/Simulink, the isolated functional blocks have been modeled. By the organic combination of these blocks, the model of BLDCM can be established easily. To guarantee the validity and speediness in simulation, the back-EMF is generated using piecewise linear curves. In the double loop of control system, a PI controller is adopted in the speed loop and a hysteresis current controller is adopted in the current loop. The simulation results testify the validity of the method for modeling. In addition, the model can be applied to verify the rationality of other control calculate ways, and offers a new thoughtway for designing and debugging actual motors.At present, the principle of zero-crossing detecting back-EMF is one of the most successful technology in detecting of the rotor-position. But there are several drawbacks in this method, which caused the motor system to be less reliable. In this paper, the theory of the principle of zero-crossing detecting back-EMF is analyzed, and the reasons of rotor-position error using zero-crossing detecting back-EMF are discussed. The paper improved the principle of zero-crossing detecting back-EMF and proposed compensation methods of rotor-position error.At last, it deduced a new improvement method from the theories, and make use of a new physical concept—the independent of speed function for accuracy checking up the turns sub-position and the communication point so as to control sensorless brushless DC motor with the breadth regulating-speed scope from zero to high speed. Based on the function, it will research the new control method. Then based on Matlab/simulink, it will simulate brushless DC motor and study the state characteristic and analyse and discuss the result, to prove the possibility and the rationality of its theories.