A hybrid sensorless control solution for an automotive drive application

Hybrid sensorless control solutions can offer the possibility of closed loop vector controlled operation when it is impractical or sometimes even impossible to rely on typical position sensors for position feedback. The hybrid approach combines the complementary benefits of mathematical model approaches and saliency tracking methods to allow operation across the entire speed range with the ability to produce high torque at zero speed. This paper presents the results of an investigation into the use of a hybrid approach for an automotive application. The hybrid approach considered consists of a Model Reference Adaptive System (MRAS) and a High Frequency (HF) Injection method which uses a square wave with a frequency equal to half the PWM frequency as the injection signal. The proposed methods were chosen such that the computational burden is minimized making operation at high PWM switching frequencies (12.5 kHz) possible. The results show that an engine mounted starter generator can be satisfactorily controlled using this methodology to deliver high starting torque and that once started, use of the MRAS minimizes the current distortion, torque ripple and audible noise associated with HF injection techniques.