Parameter estimation for BLDCM in rescue hoist drive and reduction of torque ripple and winding loss using conditional extremum current model

Brushless dc motor (BLDCM) presents excellent performance in rescue hoist drive because of its high power&torque density. The development of control strategies greatly improve torque ripple and winding loss of BLDCM respectively. However, it is still a challenge to promote comprehensive performance of hoist system such as loss and vibration etc. in the unified control framework. To solve this problem, a comprehensive control strategy of phase current optimization to reduce winding loss and torque ripple simultaneously for BLDCM that utilizing phase current continuous conduction and estimated back-electromotive force (EMF) is proposed. Firstly, with the electromagnetic torque as the constraint, a conditional extremum model of phase current is built to obtain the minimal solution of three-phase reference current. Secondly, considering non-ideal characteristics of the actual back-EMF wave, a sliding-mode observer is designed to estimate the wave online. Experiment results show that under the same load condition, the torque ripple ratio, winding loss and the current harmonics are all lower in proposed strategy than those inconventional two-phase conduction method. Good performance can be achieved by employing the proposed method in non flux-weakening application like the hoisting.