Measured Vehicle Inertial Parameters- NHTSA’S Data Through November 1998 Gary J
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1999-01-1336 Measured Vehicle Inertial Parameters- NHTSA’s Data Through November 1998 Gary J. Heydinger Ronald A. Bixel S.E.A., Inc. W. Riley Garrott Michael Pyne National Highway Traffic Safety Administration J. Gavin Howe Transportation Research Center, Inc. Dennis A. Guenther The Ohio State University Copyright © 1999 Society of Automotive Engineers, Inc. ABSTRACT Parameter Measurement Device (IPMD) (2) and NHTSA’s Tilt Table (3), respectively, both which are This paper is primarily a printed listing of the National housed at NHTSA’s Vehicle Research and Test Center. Highway Traffic Safety Administration’s (NHTSA) Light Between September 1992 and September 1996, no new Vehicle Inertial Parameter Database. This database entries were made to the database. Inertia and tilt table contains measured vehicle inertial parameters from SAE results obtained from September 1996 to November 1998 Paper 930897, “Measured Vehicle Inertial Parameters - were measured with S.E.A., Inc.’s Vehicle Inertia NHTSA’s Data Through September 1992” (1), as well as Measurement Facility (VIMF) (4,5) and S.E.A., Inc.’s Tilt parameters obtained by NHTSA since 1992. Table, respectively. The proceeding paper contained 414 entries. This paper contains 82 new entries, for a total of 496. The LIGHT VEHICLE INERTIAL PARAMETER DATABASE majority of the entries contain complete vehicle inertial parameters, some of the entries contain tilt table results Due to the difficulty of obtaining such inertial only, and some entries contain both inertia and tilt table parameters as center of gravity height, pitch, roll, and results. yaw moments of inertia, and tilt table ratio, NHTSA This paper provides a brief discussion of the decided to place its measured values for these accuracy of inertial measurements. Also included are parameters into a database. The purpose of the selected graphs of quantities listed in the database for predecessor paper (1) was to make the content of the some of the 1998 model year vehicles tested. Light Vehicle Inertial Parameter Database available to other people and organizations that need to know values INTRODUCTION of inertial parameters. The purpose of the current paper is same. Knowledge of a vehicle’s inertial parameters is The timing of the current paper is based on the fact essential for safety research and accident reconstruction. that NHTSA revived its research efforts in the area of light Some inertial parameters, such as a vehicle’s wheelbase vehicle rollover. As part of this recent research, NHTSA and track width, can be measured using only minimal collected a significant amount of inertia and tilt table data equipment (a tape measure). The determination of a on late model year vehicles. NHTSA’s VRTC performed vehicle’s weight and lateral and longitudinal coordinates field tests on 12 vehicles (including three passenger cars, of its center of gravity needs special, but widely available, three vans, three pickup trucks, and three sport utility equipment (high capacity scales). Unfortunately, vehicles) as part of their rollover research activity. accurate measurement of several important parameters Complete inertia and tilt table results for these vehicles (vehicle center of gravity height, and pitch, roll, and yaw loaded with a driver, and with a driver and VRTC moments of inertia about the vehicle’s center of gravity) outriggers, are contained in this paper and in (6). NHTSA requires highly specialized test devices. also procured complete inertia measurements for 32, Inertia and tilt table results obtained prior to 1998 model year vehicles (including eight passenger September 1992 were measured with NHTSA’s Inertial cars, six vans, eight pickup trucks, and ten sport utility vehicles) that were mostly a subset of 1998 vehicles OVERVIEW OF 1998 NCAP VEHICLE RESULTS subject to New Car Assessment Program (NCAP) testing. All 32 vehicles were tested with a driver only and 20 of Table 2 lists 32 vehicles, referred to here as “1998 the 32 vehicles were also tested at their Gross Vehicle NCAP” vehicles, tested by NHTSA; and this section Weight Rating (GVWR). For the GVWR tests all vehicles contains graphs and discussion concerning the results of were loaded with up to seven occupants in all seating inertia measurements of these vehicles. (Four of these positions which had original equipment seat belts. Ballast vehicles, the Chevrolet Astro, Mazda Protégé, Mazda was then added to the roof rack (if present on the test MPV, and Toyota Tercel, where not actually tested in the vehicle) and to the cargo areas to bring the vehicles up to 1998 NCAP program.) All of the passenger cars, pickup GVWR. The test protocol specified that no front or rear trucks, and vans listed in Table 2 were two-wheel-drive axle weight ratings should be exceeded and no ballast vehicles; while all of the sport utility vehicles listed were should be added outside of a vehicle’s cargo area, so four-wheel-drive vehicles. some tests were done at somewhat less than GVWR. These vehicles covered a wide range of vehicle Details of the test vehicles and loading conditions can be classes and weights. Passenger cars, vans, light trucks, found in NHTSA Docket 3206 (DOT Docket Management and sport utility vehicles were tested with vehicle masses System number) (7). This paper also contains data on ranging from roughly 1050 to 2700 kg. In addition to the several other vehicles NHTSA had tested in the past two measurements contained in the database, Critical Sliding years as part of their ongoing crash avoidance research. Velocity (CSV) and the ratio of the distance from the C.G. to the front wheels over the vehicle wheelbase (a/L) were ACCURACY OF THE INERTIA MEASUREMENTS calculated. All of the vehicles were measured with a driver only, and 20 were also measured at GVWR, and While the meanings of most of the column headings they are indicated on Table 2. in the Light Vehicle Inertial Parameter Database listing are self explanatory, one, IPMD Ver., is not. This column TABLE 2: 1998 NCAP Vehicles Tested is used to indicate the configuration or model of the test Make Model GVWR device used to perform a particular test. Passenger Cars Since its completion in 1987, NHTSA’s IPMD has Honda Civic undergone several modifications that have increased its Mazda Protégé X accuracy. A number 1 in this column indicates that, when Nissan Sentra Saturn SL this test was performed, the IPMD was in its original, as- Toyota Tercel X built configuration. A 2 shows that one major set of Dodge Neon X improvements had been made to the IPMD before this Chevrolet Lumina X test, etc. A VIMF indicates that the inertia measurements Mercury Tracer were obtained using S.E.A., Inc.’s VIMF. A TT means Pickup Trucks that this test was only performed on the Tilt Table and not Ford Ranger Ford F150 on the IPMD or VIMF. Chevrolet C1500 X Table 1 provides a summary of center of gravity Dodge 1500 (C.G.) height measurement error bounds for the VIMF Chevrolet S10 X and various IPMD configurations. Toyota Tacoma X Dodge Dakota X Nissan Frontier TABLE 1: Inertia Test Device/Configuration Sport Utility Vehicles IPMD Ver. Date C.G. Error Bounds Ford Explorer X VIMF Aug. 1995 to present ± 0.5% C.G. Value Ford Expedition X ± Jeep Grand Cherokee X 5 3/14/91 to Sept. 1992 6 mm Chevrolet Blazer X 3 and 4 5/18/89 to 3/13/91 ± 19 mm Toyota 4Runner X 2 2/04/88 to 4/17/89 ± 25 mm Dodge Durango X ± Chevrolet Suburban 1 3/10/87 to 2/3/88 > 25 mm Isuzu Rodeo Nissan Pathfinder For the IPMD and VIMF, the errors in the Honda CR-V X measurements of pitch and roll moments of inertia are Vans Plymouth Grand Voyager strongly a function of the errors in the measurement of Ford Windstar X C.G. height. The error bounds for pitch, roll, and yaw Dodge Caravan X inertia measurements for the IPMD Version 5 are in the Chevrolet Venture X range of 3% (1,8,9). For the older IPMD versions, the Mazda MPV X pitch and roll inertia measurement errors are Chevrolet Astro X progressively greater, while the yaw inertia error bounds are believed to be in the range of 3-5%. The quoted error bounds for the VIMF are 1% for pitch and yaw inertia, 2% for roll inertia, and 6.8 kg-m2 for roll/yaw product of inertia (4). SSF vs. VEHICLE MASS CG/ROOF HEIGHT vs. MASS 1.5 CARS 0.45 1.4 VANS TRUCKS 1.3 SUVS 0.40 1.2 SSF CARS 1.1 0.35 VANS CG/Roof Height 1.0 TRUCKS SUVS 0.9 0.30 1000 1500 2000 2500 3000 1000 1500 2000 2500 3000 Vehicle Mass (kg) Vehicle Mass (kg) Figure 1: Driver Only SSF vs. Vehicle Mass Figure 4: Driver Only CG/Roof Height CSV vs. VEHICLE MASS 22 1.5 SSF vs. VEHICLE MASS CARS 21 CARS 1.4 VANS GVWR CARS 20 TRUCKS 1.3 VANS 19 SUVS GVWR VANS 18 1.2 SSF 17 CSV (kmh) 1.1 16 1.0 15 14 0.9 1000 1500 2000 2500 3000 1000 1500 2000 2500 3000 3500 Vehicle Mass (kg) Vehicle Mass (kg) Figure 2: Driver Only CSV vs. Vehicle Mass Figure 5a: Driver Only and GVWR SSF vs. Vehicle Mass SSF vs. CSV SSF vs. VEHICLE MASS 1.5 1.5 TRUCKS 1.4 1.4 GVWR TRUCKS SUVS 1.3 1.3 GVWR SUVS 1.2 1.2 SSF SSF CARS 1.1 VANS 1.1 TRUCKS 1.0 1.0 SUVS 0.9 0.9 14 16 18 20 22 1000 1500 2000 2500 3000 3500 CSV (kmh) Vehicle Mass (kg) Figure 3: Driver Only SSF vs.