Position estimation and control of BLDC motor for VVA module with unbalanced hall sensors

VVA (Variable Valve Actuation) technology, varying intake valve of the engine, is the next-generation engine technology to improve the fuel economy and performance of the engine. Unlike conventional engines by inlet cam operated valves directly, VVA engine is precisely controlled by inlet cam, motor and control valve. This technology reduces the losses generated by the engines and improves the fuel economy and the performance of the engines. In addition, vehicles equipped with VVA engine improves the vehicle´s response, and can reduce emissions. This is the key vehicle components technology to meet the recent trend to pursue low-carbon green growth. The drive unit applied to VVA engine precisely should control the output and torque without sacrificing reliability. The motor for VVA module should be made compact and increasing the efficiency causing limited automotive volume. However it is difficult to control precisely BLDC motors with hall sensors. Because it is difficult for the hall sensors to be positioned exactly 120 electrical degrees apart. BLDC control with unbalanced hall sensors cause the current ripple and torque ripple. Sensorless configuration may be inappropriate for VVA, because of the slow response speed and difficult operating at low speed. This paper deals primarily with the design aspects of the permanent magnet brushless dc motor and simple method of measuring rotor position using hall sensors.