An optimized H infinity strategy for robust control of sensorless BLDC propulsion motor in submarines for improved maneuverability

Brushless direct current motor finds its applications in electric propulsion due to its reliability, reduced electromagnetic interference and improved life cycle cost. Rotor position sensing with sensorless techniques exhibit better performance with varying temperature and humidity conditions as well as continual motion of the vessels and also overthrow the use of hall sensors. A control technique with direct implementation of an optimal H infinity controller in the speed control feedback loop of a sensorless BLDC motor that is insensitive to disturbances and uncertainties is proposed in this paper. This provides a robust dynamic performance compared to conventional PI controller and simulation results of the comparison are presented. For optimum weight selection of H infinity controller, particle swarm optimization technique is employed so that sensitivity function is small for low frequency region and complementary sensitivity function is low for high frequency region which is the trade off required for good reference tracking, disturbance rejection, being insensitive to modeling errors and noise. Results of the case study conducted based on the operational profile of submarine VII C available with British admiralty report have been presented. The reduced torque ripples along with 50% reduction of steady state error results in enhanced maneuverability, low noise and vibration.