Sensorless control method of 3-Phase BLDC motor through the real time compensation of back-EMF constant

摘要

This paper proposes the novel sensorless control algorithm for 3-Phase BLDC motors with trapezoidal back-EMF. The proposed algorithms include both the new back-EMF estimation method by using the DC current model and a compensator for the electric parameter errors of the BLDC motor to improve performance of sensorless control more exactly. The back-EMF can be easily calculated from the electrical voltage equation. However, it has some errors at the commutation period. This error can be reduced by using the proposed sensorless control algorithm which is derived by using the mechanical and electrical equation simultaneously for the accurate estimation of the back-EMF. In this case, the back-EMF estimation is affected by the electric parameters. If the motor parameters have errors, there will be some errors of the estimated back-EMF. Therefore, a new algorithm is needed for parameter error compensation. Among the motor parameters, stator resistor and back-EMF constant are mainly affected by the temperature. Therefore, this paper proposes the new sensorless control algorithm with the real time compensation of the motor parameter variation according to temperature. The main attractive features of the proposed algorithm have the robustness to the parameter variation and the transient state, and the less torque ripple by using the DC-current model. The usefulness of the proposed sensorless control method is verified through the simulation.