Issues regarding the vtcpmf_fuel_model

[yuanjinghui]

Issues Identified in the vtcpmf_fuel_model Function within the Physics Model Class:

1. Unit of v_speed:
   The current implementation uses meters per second (m/s) for v_speed. However, the correct unit should be kilometers per hour (kph). This discrepancy needs to be addressed to ensure consistency with the intended model specifications.

2. Vehicle Mass:
   The function currently uses a vehicle mass of 3152 kg, which is not a realistic value for typical vehicles. The mass should be verified and updated to a reasonable value in kilograms (kg).

3. Correction to r_f Equation:
   In the r_f equation, the first element is missing a division by 25.92. This correction is necessary for accurate computations.

Verification:
To validate the estimation results, we should calculate the fuel efficiency in Miles per Gallon (MPG). The expected MPG value for this model should be approximately 20 MPG. This step will ensure that the model produces realistic and reliable outputs.