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fix issue #542 - changing convergence crit. for brk torque and disengage condition for GBauto

fix issue #542 - changing convergence criterion for brake torque computation if GB is automatic and in 1st gear & tightening AT disengage condition

  • Error observed: brake torque determination method converges to a value fitting tolerances, but the effective request tolerance is exceeded and result in very small underload that leads to a crash the change of criterion in brake torque determination method

  • This is due to the fact that DryRun request of brake torque determination method send back a DeltaDrag located at the torque converter output level when overload or underload (instead of the ICE output when an ICE operating point is reached). This deltaDrag is used as criteria to determine the brake torque. To avoid false positive (point valid on Torque converter level, but not on ICE level), and keep tendencies in the model this DatadeltaDrag is multiplied by 10.

  • Increasing this factor by 10% (from 10 to 11) is sufficient to avoid the error, as well as increasing the criterion in Driver/SearchBrakingPower, which is the solution selected here: This partially fix issue #542: the computation does not crash for HeavyUrban P31SD LowLoading,but still does for Urban P31DD RefLoad an unexpected behavior is observed: going downhill, strategy does not engage from 1C to 1L when it could due to the fact that acceleration is zero when gearshift timing is reached, and prefers to go to neutral and brake, leading to ice idling and overconsumption compared to other cases allowing upshift because gearshift timing is reached during previous acceleration

  • tightening AT disengage condition when Tice>0 and Tout<0 by imposing that acceleration should be negative, strictly (instead of <=0) completely fix issue #542: computation does not crash for HeavyUrban P31SD LowLoading and for Urban P31DD RefLoad, while behavior in gear selection works as expected

  • the fix has been tested on different case of vehicles and previous issues: no significant change observed in consumption results (max -0.08%) except for the input file of issue 542 where consumption is reduced for the cycles that previously crashed.

Edited by Guillaume ALIX

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