Role of subsystem in vehicle
The gearbox control block diagram generates a gear ratio command and passes it to the gearbox, modeling a driver who chooses a gear based on engine load and speed and moves the gearshift lever accordingly.
Description of modeling approach
One-dimensional lookup tables, one for each gear, are used to implement the dependence of the shift command (up, down, or no shift) upon current gear, and engine speed and load assuming the current gear is maintained.
Red lines in the figure above indicate upshift and downshift lines in engine torque and speed space. The black curve near the top indicates the engine’s maximum torque envelope. The numbered curves are efficiency contours. (Note that although the plot’s y-axis is engine torque, the elbow points are in fact defined in terms of engine load, which is defined here as the engine torque at a given speed divided by its maximum torque at that speed. So the actual red lines used by ADVISOR are not straight in engine torque/speed space, since the maximum engine torque depends on speed. This is a subtle and generally not critical point, so don’t think about it too much.)
The elbow points in the rightmost red line are defined using variables named gb_gearX_upshift_spd and gb_gearX_upshift_load, where X should be replaced with the appropriate gear number. When the engine torque/speed point would fall to the right of the rightmost red curve, an upshift is commanded.
Likewise, gb_gearX_dnshift_spd and gb_gearX_dnshift_load define the leftmost red line. When the engine torque/speed point would fall to the left of the leftmost red curve, a downshift is commanded.
For example values of these variables, see the file PTC_CONV.m.
Variables used in subsystem
gb_gear1_dnshift_spd gb_gear1_dnshift_load gb_gear1_upshift_spd gb_gear1_upshift_load
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gb_gear5_dnshift_spd gb_gear5_dnshift_load gb_gear5_upshift_spd gb_gear5_upshift_load