Presentation on theme: "WLTP-06-31e WLTP correction algorithms progress report from TUG (chassis dynamometer corrections) and TNO (coast down corrections) preliminary results."— Presentation transcript:
1 WLTP-06-31eWLTP correction algorithms progress report from TUG (chassis dynamometer corrections) and TNO (coast down corrections) preliminary results ( )TU Graz: Stefan Hausberger David LeitnerTNO: Norbert LigterinkRob CuelenaerePim van MenschContent of TUG slides not yet discussed with TNO
2 Chassis dynamometer corrections January 20, 2014Chassis dynamometer corrections
3 Correction algorithms for variations in the WLTP testing January 20, 2014Correction algorithms for variations in the WLTP testingMethods drafted for chassis dynamometer test (TUG)Target is, to correct all test results to the target settings. Following deviations are analysed and lead to the listed correction methods:Correct test results for imbalances in battery SOC as drafted in WLTPSet up a vehicle specific Willans linear function (from WLTP subcycles) (k = DCO2/DkWh) from the SOC-corrected WLTC test data as basis for corrections of deviations in positive wheel power).Deviation against target speed: calculate from driven speed profile the actual power at wheels [P(t) = (R0 + R1*v+R2*v² + m*a) * v], Calculate difference in average positive power values
4 Correction algorithms for variations in WLTP testing January 20, 2014Correction algorithms for variations in WLTP testing4. Correct for deviation from target power: DPwheel = P pos-target – P pos-test Correct for deviation with vehicle based Willans function: DCO2 = DPwheel * k. Divide corrected CO2-value [g/h] by using target cycle distance [km] (not distance driven).5. Inaccuracy of road load simulation by the chassis dynamometer:make coast down directly after WLTC for proper road load values from chassis dynamometer.Calculate avg. positive power at wheels with chassis dynamometer parameters and with target parameters DPwheel DCO26. Temperatures from preconditioning and soak:to apply generic influence on FC, seems to be best option for small temperature ranges (linear or logarithmic):Δ𝐹𝐶 % =5.18∗ln( 𝑡 𝑡𝑒𝑠𝑡 𝑡 𝑡𝑎𝑟𝑔𝑒𝑡 ) (for 20°C < ttest < 26°C)
5 January 20, 2014Example for results passenger car 1 with diesel engine 6 repetitions WLTC under normal conditions Measured CO2 SOC-corrected complete correctionNote: * tests 2, 3 and 4 were out of WLTP temperature range to test temperature correction * correction for road load settings not applied (no coast down after each test available)
6 Cumulative application of corrections against measured CO2 January 20, 2014Example for result passenger car 2 with diesel engine 5 repetitions with wide variations in temperature, SOC at start, driver Stepwise effects of correction functionsCorr SOCCorr v-deviationsCorr temp.Cumulative application of corrections against measured CO2
7 5. Temperatures from preconditioning and soak January 20, 20145. Temperatures from preconditioning and soakΔ 𝐶𝑂 2 % =5.18∗ln 𝑡 𝑡𝑒𝑠𝑡 𝑡 𝑡𝑎𝑟𝑔𝑒𝑡𝐶𝑂 2 𝑐𝑜𝑟𝑟𝑒𝑐𝑡𝑒𝑑 = 𝐶𝑂 2 ∗ 1+ ∆ 𝐶𝑂 2 % 100This logarithmic function worked very well between 1°C < ttest < 90°C for the vehicles tested yet, so it should be applicable for the WLTC tests.This correction must be the final one to avoid influences of SOC or speed deviations in the CO2-value.
8 Overview on sequence of corrections January 20, 2014Overview on sequence of corrections1) Measured values in WLTC: CO2 [g], distance [km], DSOC [kWh], Oil temperature at start [°C] instantaneous velocity [km/h] to compute average Pwheel [kW] per phase2) DSOC correction: apply WLTP option (or detailed approach)DCO2 SOC [g] = kengine x DSOCCO2 SOC_corr [g] = CO2 measured [g] + DCO2 SOC [g]3) Establish vehicle specific Willans linear equation from CO2 SOC_corr [g/h] and Pwheel [kW] per phase4) Wheel power correction 4.1) deviation against target speed at times with power > ) deviations in road load settings at chassis dyno vs. target DCO2 [g] = k x DWwheel [kWh] CO2 v_corr [g] = CO2 SOC_corr [g] + DCO2 [g]5) Distance correction: CO2 d_corr [g/km] = CO2 v_corr [g] / target distance [km]6) Temperature correction: (different soak temperature): CO2 corr [g/km] = CO2 d_corr [g/km] x (1+ DCO2temp [%]/100)
9 January 20, 2014Optional: detailed approach for SOC correction (instead of WLTP method)generate vehicle specific Willans line and calculate gradient of Willans lineX-axis: 𝑃 𝑒𝑛𝑔𝑖𝑛𝑒_𝑝ℎ𝑎𝑠𝑒(𝑖) = 𝑃 𝑤ℎ𝑒𝑒𝑙_𝑝ℎ𝑎𝑠𝑒(𝑖) η 𝑝𝑜𝑤𝑒𝑟𝑡𝑟𝑎𝑖𝑛 + ∆𝑃 𝑎𝑙𝑡𝑒𝑟𝑛𝑎𝑡𝑜𝑟_𝑝ℎ𝑎𝑠𝑒(𝑖) η 𝑔𝑒𝑛 ∗η 𝑒𝑛𝑔−𝑔𝑒𝑛With DPalternator……additional power at alternator due to SOC imbalanceY-axis: average CO2 per phase in [g per s]~12% for WLTPIf 𝑃 𝑤ℎ𝑒𝑒𝑙 ∗ η 𝑝𝑜𝑤𝑒𝑟𝑡𝑟𝑎𝑖𝑛 is lower than Poverrun, the work for battery charging is not CO2 relevant: (regenerative braking in alternator assumed as standard electric energy is missing at times with positive engine power )∆𝑪𝑶𝟐= 𝑾 𝒅𝒊𝒔𝒄𝒉𝒂𝒓𝒈𝒊𝒏𝒈−𝒑𝒉𝒂𝒔𝒆 𝒊 − 𝑾 𝒄𝒉𝒂𝒓𝒈𝒊𝒏𝒈−𝒑𝒉𝒂𝒔𝒆 𝒊 ∗ 𝒕− 𝒕 𝒐𝒗𝒆𝒓𝒓𝒖𝒏 𝒕 𝜼 𝒈𝒆𝒏 ∗𝜼 𝒆𝒏𝒈−𝒈𝒆𝒏 ∗𝒌𝑊 𝑑𝑖𝑠𝑐ℎ𝑎𝑟𝑔𝑖𝑛𝑔 = 𝑈 (𝑡) ∗ 𝐼 𝑑𝑖𝑠𝑐ℎ𝑎𝑟𝑔𝑖𝑛𝑔_(𝑡) 𝑑𝑡𝑊 𝑐ℎ𝑎𝑟𝑔𝑖𝑛𝑔 = 𝑈 (𝑡) ∗ 𝐼 𝑐ℎ𝑎𝑟𝑔𝑖𝑛𝑔_(𝑡) 𝑑𝑡𝑡=𝑑𝑢𝑟𝑎𝑡𝑖𝑜𝑛 𝑜𝑓 𝑝ℎ𝑎𝑠𝑒𝑡 𝑜𝑣𝑒𝑟𝑟𝑢𝑛 =𝑡𝑖𝑚𝑒 𝑤ℎ𝑒𝑛 𝑃 𝑤ℎ𝑒𝑒𝑙 ∗ η 𝑝𝑜𝑤𝑒𝑟𝑡𝑟𝑎𝑖𝑛 < 𝑃 𝑜𝑣𝑒𝑟𝑟𝑢𝑛𝑘=𝑔𝑟𝑎𝑑𝑖𝑒𝑛𝑡 𝑜𝑓 𝑊𝑖𝑙𝑙𝑎𝑛𝑠 𝑙𝑖𝑛𝑒Poverrun
10 SOC correction effect for vehicle # 1 (diesel engine) January 20, 2014SOC correction effect for vehicle # 1 (diesel engine)Comparison of the SOC correction method of WLTP draft with detailed approach.Small differences but detailed method would be much more complex for type approvalSimple approach as outlined in WLTP is good option.
11 Coast down corrections January 20, 2014Coast down corrections
12 January 20, 2014Current WLTP coast down corrections are validated (no reasons found to augment existing methods)wind correction: (stationary method) in principle correct, but large: source of uncertaintyvehicle weight correction: physically sound, measured effect is somewhat larger (f1?)tyre temperature correction: magnitude reproduced, despite doubts on physical soundnessair pressure correction: limitation to f2 somewhat doubtful (role f1?), but effect reproducedroad slope: 1/T average yield appropriate correction for sloping trackstyre pressure correction: is based on a particular tyre pressure role of f1 (in “f0 + f1*v + f2*v2”) in the WLTP text could be reviewed
13 January 20, 2014WP 210 Correction parameters and algorithms for road load determinationNoParameterMethodCommentsR1rotational inertia correctionWeigh the wheels and tyres and use 60% of the weight as rotational inertia, compensate on dynamometer.The rest of the driveline (after transmission) has a limited contribution, effect may vary somewhat with rim sizes and wheel type (secondary effect).Inertia of wheels and tyres (separate tests):WLTP: “3% of unladen mass (UM=1201 kg)” kgnormal wheels: 38.0 kg (56% of wheel weight)18” wheels: 54.4 kg (64% of wheel weight)theoretical arguments leads to 60% - 70% of wheel weightfrom coast-downto chassis dynamometer
14 January 20, 2014WP 210 Correction parameters and algorithms for road load determinationNoParameterMethodCommentsR2tyre pressure correctionThe rolling resistance is corrected for difference between pressures by:f0final = f0test * (Ptest/Pset)Apply per tyre, average the result.Current WLTP text is based on specific case.NoParameterMethodCommentsR4tyre label correctionf0final =f0test*(RRCclass/RRCtest)Correct the actual tyre labels (Rolling Resistance Coefficients: RRC) back to the setpoint, or “class value” value, if RRCtest < RRCclass.Tyre aspects difficult to recover from vehicle tests:rely on tyre label testing for the appropriate correctionsrange in a single tyre label more than 10% still a flexibility, to be corrected for.How to include f1 in rolling resistance corrections is under investigation.
15 January 20, 2014WP 210 Correction parameters and algorithms for road load determinationNoParameterMethodCommentsR10air density correction r/r0Use air pressure and water vapour pressure. (Water vapour pressure depends on relative humidity and temperature.)Partly included in WLTP, update with humidity.Air viscosity effects are ignored.water vapour 37.7% lighter than dry airhumidity effectespecially athigh temperaturesair density r varies slightly with humidity:maximal 37.7% x 7.3% = 2.7%difference of densitywater vapour content at 40o CP0 = 100 kPaT0 = 293 Kr = r0 * (T0/T) * (P/P0) * (1.00 – 0.38 * (RH/100) * (Pvapour/P))Pvapour[bar] = * /( T[C])Antoine equation
16 Open issues, difficult to cover in simple corrections January 20, 2014Open issues, difficult to cover in simple correctionstest track surface: large effect on rolling resistance (up to 24%)probably more so because of tyre tread and pressuredifficult to correct for, road surface characteristics not knowntyre pressure variations during coast down testing: (up to 15%)not fully fixed by conditioning (average: up 7% from ambient)can be controlled somewhat by intermediate driving/text executionvariation in wind speed and direction during testing: (“gustiness”)wind has large effect need for back and fro testing (a and b)small remainder of a and b average largely affected by minute-to-minute variations
17 January 20, 2014preliminary results current status: final testing, reporting in progress thank you for your attention
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