Design of Permanent Magnet Brushless DC Motor Drive System for Energy Recouping in an Electric Automobile

As an alternative to IC engine driven automobiles, electric vehicles are emerging as attractive means of transportation. Taking into account the different operating conditions of an automobile, viz. acceleration, coasting and regenerative braking, BLDC motor-based electric drive system is considered. A BLDC motor-based drive system has many advantages including independent variable speed and variable torque operation along with regeneration capability. In addition to the main battery to supply motive power, an auxiliary battery at lower voltage is normally provided for meeting loads like front and back lights, wiper control, window operations, interior lighting, music system etc. Hence it is possible to charge the auxiliary battery by recouping the kinetic energy of the automobile during braking interval through a DC–DC boost converter. In this paper, automobile dynamics including road friction, aerodynamic forces and transmission, are considered for calculating the shaft torque of the BLDC motor, while following a specified speed-time characteristic and designing a drive system and its controller for closely following the above profile. The problem is formulated by integrating all the above aspects and solved using multiple feedback loops and developing two alternate controllers, viz. MPC and PI controllers, to cover the above three modes of operation. A simulation schematic containing the above functional blocks as subsystems has been created and integrated for the simulation of the entire system, and the results are presented. The results indicate that auxiliary battery regeneration scheme makes significant energy capture possible. Experimental work on a laboratory set up consisting of a BLDC motor drive system, and ARM CORTEX M4F Microcontroller board has been carried out to validate the simulation results.