Research and Development Recent NHTSA Dynamic Rollover Testing

Research and Development Recent NHTSA Dynamic Rollover Testing Experience Dr. W. Riley Garrott National Highway Traffic Safety Administration Vehicle Research and Test Center April 12, 2001 5 Mar 01, page 1

Research and Development Presentation Overview • • • Summary of Recent Testing Test Maneuvers Our Test Facilities Repeatability Outstanding Issues 5 Mar 01, page 2

Research and Development Summary of Recent Testing • NHTSA has been performing dynamic rollover testing steadily since fall of 1996 – – – – Isuzu Trooper investigation in 1996 Phase I-A research in 1997 Phase I-B research in 1997 – 98 Phase II research in 1998 Phase III research in 1999 – 2000 Ford Explorer investigation in 2000 Phase IV research in 2001 5 Mar 01, page 3

Research and Development Dynamic Rollover Testing Video AVI Not Included 5 Mar 01, page 4

Research and Development Test Maneuvers • Two broad categories – Open-loop. Handwheel steering angle is specified function of time ª J-Turn with Pulse Braking ª Fishhooks (reverse steer) ª Resonant Steer ª Single Sine – Each of above has many variations 5 Mar 01, page 5

Research and Development Test Maneuvers • Closed-loop. Handwheel steering angle varies according to actions of vehicle – Driver closes feedback loop ª Double Lane Change ª Off-Road Recovery simulation – Instrumentation closes feedback loop ª Fishhook with Roll Rate Feedback 5 Mar 01, page 6

Research and Development Our Test Facilities • VRTC located on the grounds of the Transportation Research Center, Inc. – Major automotive proving grounds – TRC’s Vehicle Dynamics Area – the large, flat paved area needed for dynamic rollover testing • Programmable steering controller • Rollover instrumentation suite 5 Mar 01, page 7

Research and Development TRC’s Vehicle Dynamics Area 5 Mar 01, page 8

Research and Development Programmable Steering Controller 5 Mar 01, page 9

Research and Development Rollover Instrumentation Suite 5 Mar 01, page 10

Research and Development Repeatability • During dynamic rollover testing, vehicles become highly non-linear – Small changes in inputs, test conditions can lead to large changes in test outcomes – Testing in early-70’s found up to 40% run-torun variability 5 Mar 01, page 11

Research and Development Repeatability • Have had good repeatability in our testing – Major improvement over 70’s – Less tire wear with radial tires plus better equipment • Open-loop maneuver repeatability – Peak lateral accelerations – 0. 05 g – Peak roll angles – 0. 5 degrees – Minimum speed for two-wheel lifts to occur – 2 mph • Closed-loop double lane change 5 Mar 01, page 12

Research and Development Issues • Maneuver(s) to use for rollover ratings • Ensuring that cannot get good rollover rating by degrading vehicle handling – By putting tires with poor traction on a vehicle, can prevent two-wheel lifts in these maneuvers – Safety may be degraded because cannot turn as sharply • Use of two-wheel lifts as safety-relevant measure – Minor two-wheel lifts may not be safety issue 5 Mar 01, page 13

Research and Development Issues • Longer-term repeatability – Effects of weather of results ª Summer versus winter – Changes to the same test surface with time • Reproducibility – Effects of testing on different test surfaces 5 Mar 01, page 14

Research and Development Issues • Outrigger effects – Must have for safety, prevention of test surface damage – How do they change a vehicles rollover propensity? • Tire wear – How much testing can be performed on a set of tires before wear effects become significant • Tire debeading – What to do if tires debead while performing rollover rating testing 5 Mar 01, page 15