The disadvantages of the Brushless DC Motor over the AC motors are:
higher maintenance (due to brushes)
more expensive
In addition to the above the Brushless DC Motors have the same advantages over AC motors but they also have more advantages over Brushed DC Motors
lower maintenance (no brushes)
even higher starting torque ( Due to rare earth magnets)
even higher efficiency (over 90%) on sub fractional motors
even more compact design
better heat dissipation
lower noise
The design and implementation of a DSP microprocessor based DC motor servo driver are presented. The integral variable structure control (IVSC) approach is proposed for the outer loop of the driven system. Conditions are derived which ensure the existence of a nonideal sliding motion for the IVSC approach and also prove that the described motion in the nonideal sliding region will be close to the ideal sliding motion. Simulation and experimental results show that the proposed scheme can achieve an accurate velocity/position servo tracking result and is robust to plant parameter variations and external load disturbance
