Abstract:  In order to study the cause of the deterioration of wheel hub electric car ride comfort and the quality
requirements of the driven motor, set up a quarter wheel body with two degrees of freedom vehicle vibration
system model, calculate the invariant point to indicate the reasons for the deterioration of ride comfort, also give
the weight requirements of the driving motor to improve ride comfort, and use Simulink to simulate and verify the
result. The results show that the frequency invariant point does not change with the change of spring stiffness and
damping coefficient, and the amplitude frequency characteristic value of the input speed of road surface for the
vehicle body acceleration corresponding to frequency invariant points is close to the maximum value, it has a
great influence on ride comfort, causing wheel hub electric vehicle ride comfort deterioration, and we can give
the quality requirements of the drive motor.

Key words: invariant point,  hub electric drive, amplitude-frequency characteristics, hub motor;riding comfort