Low-Cost Sensorless Scalar Control of a Brushless Motor for Automotive Fan System Application

This paper presents a simplified sensorless scalar control algorithm of a permanent magnet synchronous motor (PMSM) for cost-effective automotive applications. Such a simple and low-cost control algorithm could be used in an engine-cooling fan (ECF) system to provide a competitive solution to the automotive market. Although field-oriented control (FOC) algorithm has higher performance, the computational burden results in higher-priced microcontrollers with higher specifications. Consequently, some design constraints should be considered in order to achieve reasonable motor control system performance at a lower cost. The proposed control algorithm computes the motor position based on the phase and dc-link voltages. Furthermore, the expected motor position is calculated using the reference motor speed, the amplitude of the voltage vector applied, and the battery current. The difference between the calculated and expected motor positions is then used to compute the precise rotor position. The appropriate voltage vector is then applied to the motor terminals using space vector pulse width modulation (SVPWM). Both simulation and experimental results are presented to validate the performance of the proposed control algorithm.