Characterizing engine load
Aspects of the disclosure are directed to characterizing effective vehicle frontal area. As may be implemented in accordance with one or more embodiments, one or more operating parameters of the vehicle are obtained. Such parameters may be obtained during one or more qualifying periods of time, such as those periods in which an operating parameter or parameters such as speed and/or acceleration are within a range of values. A value that provides an estimate of the vehicle frontal area is then generated based on the one or more operating parameters.
1. A method comprising:
detecting signals from an on board diagnostics (OBD) port of a vehicle that is connected to an engine control unit within the vehicle, while the vehicle is moving along a surface;
obtaining, from the detected signals, operating parameters of the vehicle including a power parameter and a speed parameter; and
estimating effective frontal area of the vehicle based on the power parameter and the speed parameter.
2. The method of claim 1 , wherein estimating the effective frontal area includes
determining at least one period of time during which the vehicle is moving along the surface at a constant speed; and
for one or more of the detected signals obtained during the at least one period of time, estimating the effective frontal area by:
determining a total power of an engine of the vehicle,
determining a rolling resistance power to overcome a rolling resistance of the vehicle at the constant speed,
determining a power loss value attributable to the effective frontal area by subtracting the determined rolling resistance power from the determined total power, and
utilizing the power loss value to determine the effective frontal area.
3. The method of claim 2 , wherein determining the at least one period of time includes determining the at least one period based on the speed parameter, the speed parameter including one or more of vehicle speed, vehicle acceleration, engine speed and engine load.
4. The method of claim 3 , wherein determining the at least one period includes comparing the one or more of vehicle speed, vehicle acceleration, engine speed and engine load with one or more predetermined reference values.
5. The method of claim 2 , wherein determining the rolling resistance includes determining the rolling resistance based on a gradient of the surface along which the vehicle is moving.
6. The method of claim 2 , wherein determining the power loss value includes:
determining an expected power at a crank of the vehicle during periods of steady state and at a constant speed without aerodynamic resistance;
determining an actual amount of power applied to the crank based on engine load values provided by the one or more detected signals; and
determining the power loss value based on a difference between the actual amount of power applied to the crank and the expected power at the crank.
7. The method of claim 1 , wherein estimating the effective frontal area includes estimating aerodynamic resistance of the vehicle, and estimating the frontal area based on the estimated aerodynamic resistance, the speed parameter and a coefficient of drag for the vehicle.
8. The method of claim 1 , further comprising estimating total current power for the vehicle during a period in which the vehicle is travelling at a constant speed, wherein estimating the effective frontal area includes using the estimated total current power.
9. The method of claim 8 , wherein estimating the total current power includes using an engine load parameter obtained from the detected signals.
10. The method of claim 8 , wherein estimating the total current power includes estimating the total current power based on expected transmission losses.
11. The method of claim 10 , wherein estimating the total current power based on expected transmission losses includes subtraction and/or multiplication of an obtained power value by one or more empirical power factors.
12. The method of claim 1 , further comprising estimating total current power for the vehicle during each of a plurality of periods in which the vehicle is travelling at a constant speed, and determining a moving or weighted average of the total current power over the plurality of periods, wherein estimating the effective frontal area includes using the moving or weighted average of the total current power.
13. The method of claim 12 , wherein determining the moving or weighted average of the total current power includes, for each of the plurality of periods:
calculating an average value of the total current power over the period; and
at an end of each period, calculating a weighted average between the calculated average value and a value obtained from previous periods.
14. An apparatus comprising:
a first circuit configured and arranged to couple to an on board diagnostics (OBD) port of a vehicle that is connected to an engine control unit within the vehicle, and to detect signals from the OBD port while the vehicle is moving along a surface; and
a second circuit configured and arranged to estimate frontal area of the vehicle by:
obtaining, from the detected signals, operating parameters of the vehicle including a power parameter and a speed parameter; and
estimating effective frontal area of the vehicle based on the power parameter and the speed parameter.
15. The apparatus of claim 14 , wherein the second circuit is configured and arranged to estimate the effective frontal area by:
determining at least one period of time during which the vehicle is moving along the surface at a constant speed; and
for one or more of the detected signals obtained during the at least one period of time, estimating the effective frontal area by:
determining a total power of an engine of the vehicle,
determining a rolling resistance power to overcome a rolling resistance of the vehicle at the constant speed,
determining a power loss value attributable to the effective frontal area by subtracting the determined rolling resistance power from the determined total power, and
utilizing the power loss value to determine the effective frontal area.
16. The apparatus of claim 15 , wherein the second circuit is configured and arranged to determine the at least one period of time based on the speed parameter, the speed parameter including one or more of vehicle speed, vehicle acceleration, engine speed and engine load.
17. The apparatus of claim 15 , wherein the second circuit is configured and arranged to determine the power loss value by:
determining an expected power at a crank of the vehicle during periods of steady state and at a constant speed without aerodynamic resistance;
determining an actual amount of power applied to the crank based on engine load values provided by the one or more detected signals; and
determining the power loss value based on a difference between the actual amount of power applied to the crank and the expected power at the crank.
18. The apparatus of claim 15 , wherein the second circuit is configured and arranged to determine the power loss value by further subtracting estimated transmission losses in the vehicle, and to determine the effective frontal area by utilizing the power loss value to estimate aerodynamic resistance of the vehicle and to determine the effective frontal area based on the estimated aerodynamic resistance.
19. The apparatus of claim 14 , wherein the second circuit is configured and arranged to:
estimate total current power for the vehicle using an engine load parameter obtained from the detected signals during a period in which the vehicle is travelling at a constant speed, and
estimate the effective frontal area using the estimated total current power.
20. The apparatus of claim 14 , wherein the second circuit is configured and arranged to
estimate total current power for the vehicle during each of a plurality of periods in which the vehicle is travelling at a constant speed,
determine a moving or weighted average of the total current power over the plurality of periods,
and estimate the effective frontal area by using the moving or weighted average of the total current power.