A current control algorithm based on variable current threshold for four-switch three-phase BLDCM using intelligent controller

Cost minimization is the key to the large volume manufacture and application of the brushless DC motor. A novel four-switch three-phase brushless DC motor drive based on variable threshold direct current control is proposed to lower cost and improve performance. The real-time current threshold identifier working based on speed error and current of DC link, is made up of a radial basis function neural network. The current threshold value is adjusted synchronously with phase conversion to make sure that the phase current wave could keep in shape of trapezoid. Two single neuron PID controllers consist of the current controller. They individually regulate duty cycle of PWM signals working on the inverter bridge to make phase current fall in the specified threshold quickly and smoothly. Experimental system has the advantages of flexible control, strong adaptability, and achieves higher control accuracy and better robustness. Also the structure of system is simplified.