Modelling of a sensorless rotor Flux oriented BLDC machine

This paper presents the modelling and simulation of a low-power Brushless DC machine in a Rotor Flux Oriented mode in MATLAB/Simulink. The modelling of the machine is presented in the synchronous dq frame. Using this model suitable Proportional Integral controllers have been designed for the Rotor Flux Oriented speed and current loops. Sensorless simulation estimates obtained from a back-emf observer for both electrical angle and rotor speed are presented. The dynamic response of the model is also shown in sensorless closed-loop whereby the estimates obtained are used for control purposes. The error in the estimated position and speed during closed-loop are kept below 1.9 % and 0.1 % respectively such that the speed controlled system is stable throughout a wide range of speeds.