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(Gfu amax /3600+C D Au 3 amax /76410)/η T .
P e
(1)
Where, the P e is the power of the motor, the η T which equals to 0.912 is the
transmission efficiency, the G equals to 2000kg multiplies 9.8 is the weight, the f
equals to 0.014 is the roll resistance coefficient, the u amax equals to 100km/h is the
maximum speed, the C D equals to 0.35 is the wind resistance coefficient, the A equals
to 1.9 is the aweather.
The driving resistance power curve which is shown is Fig. 1 can be plotted using
MATLAB according equation (1), the required power of the motor is 17.8kw. So a
permanent magnetic motor whose power is 20kw is chosen.
Fig. 1. Driving resistance power curve
3 Computer Aided Analysis Method for the Character of the
Motor
The output torque and the efficiency of the system which composed by the motor and
the motor controller are measured using dynamometer. The voltage of the
accelerating pedal is varied from 0.9V to 4.28V. The character of the motor is
measures from the 1.0V to 4.2V taken the 0.2V as the interval. Then, seventeen
groups of data are obtained.
Here, the analysis process of the data measured while the pedal voltage is 2.8V
using MATLAB is described.
After importing the mdf file which generated by the experimental device, the
curve of the output torque and efficiency can be plotted as Fig. 2 and Fig. 3 using
“plot” command. For the convenience of following analysis, the curve should be
fitted using the fitting tool provide by the MATLAB. It is shown in Fig. 2 that there
is an inflexion between the torque of low speed and the torque of the high speed, so
the output torque curve is fitted piecewise. But the efficiency curve is smoothly, so
the efficiency curve is fitted in total. The fitted curves are shown in Fig. 4 and
Fig. 5.
The fitted output torque curves and the efficiency curves of the seventeen groups
data are plotted in Fig. 6 and Fig. 7. Then, the fitted power and the efficiency curve
while the pedal voltage is 4.2V is plotted in Fig. 8 and Fig. 9.
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