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ROAD GRADE INFERENCE FOR OBD MONITOR ROBUSTNESS

IP.com Disclosure Number: IPCOM000238353D
Publication Date: 2014-Aug-19
Document File: 1 page(s) / 223K

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The IP.com Prior Art Database

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ROAD GRADE INFERENCE FOR OBD MONITOR ROBUSTNESS

Vehicles sold in North America are required to perform Evap leak detection as part of OBDII requirements. Green states required to monitor for 0.02" leaks whereas federal states have to perform
0.04" leak tests.For regular gasoline engines, the 0.04" Evap leak detection monitor executes during engine running while cruising at 40 MPH. The Evap system is evacuated using engine manifold vacuum (opening the canister purge (CPV)), the system is then sealed by closing canister vent valve (CVS), and finally the Evap system vacuum bleedup is monitored to infer leaks in system. Excessive bleedup is indicative of a leak, while small bleedups indicate a good system. One noise factor that can result in artificial bleedups is an altitude change. An upward pitch in the road can also cause tank pressure to rise and a false leak failure can result. A downward pitch results in tank pressure drop and a false pass can result. Evap monitors are not robust to road surface pitch.

Method

The method infers an altitude change (characterized by road pitch) without utilizing additional sensors such as inertial sensors or accelerometers. The road pitch or grade inference is calculated by establishing a vehicle weight profile on flat ground engine using load/torque information and monitoring for loss for change in acceleration when road grade changes. The inference uses nominal vehicle weight on flat ground as the baseline for a acceleration p...