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Key Technical Issues and Position Signal Detection Methods for Wheel Hub Motors

Wheel hub motor technology, also known as in-wheel motor technology, is characterized by the integration of power, transmission and braking systems inside the wheel hub, which greatly simplifies the mechanical components of electric vehicles.


Key technical issues in the research of wheel hub motor systems



Position signal detection methods for wheel hub motors without position sensors


Back-EMF method


The basic principle of this method, which is the most mature, effective, and common method, is to delay the detected back-EMF signal when it crosses zero by 30° electrical angle, yielding the switch signal of the power pipe. As there is no or weak back-EMF signal when the motor is stationary or rotating at low speed, the back-EMF method is generally used in conjunction with "three-stage" starting technology.


Freewheeling diode method


This method of wheel hub motors determines the rotor position by detecting the conduction state of the freewheeling diode on the anti-parallel and inverter bridge power switches.


Inductance method


This method observes changes in winding inductance with rotor position, and calculates the rotor position signal through certain calculations.


State observer method


This method of wheel hub motors estimates the rotor position of the motor by using the motor's three-phase voltage and current as coordinates based on the Park equation. As the coordinate transformation only considers the fundamental component, this method is mainly used for PMBLDCM with sine-wave back-EMF.