Low-Speed Maneuverability, High-Speed Roll-Stability, and Brake Type Performance of Heavy Truck 33-ft Double Trailers

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Virginia Tech

This dissertation details the methods and analysis of extensive physical tests and simulation conducted by the Center for Vehicle Systems and Safety (CVeSS) at Virginia Tech on the maneuverability, roll-stability, and brake type performance of 33-ft double trailers. Little literature exists for 33-ft doubles because they are uncommon on the U.S. roads due to current federal restrictions limiting long-combination vehicles to 28-ft doubles. With the continual rise in e-commerce, however, there is a push by package carriers on legislation to permit carriers to introduce 33-ft doubles into their fleets. Three separate studies detailed herein highlight 33-ft double trailers' off-tracking, roll-stability with stability control systems, and brake type influence on braking performance.

The first study compares low-speed off-tracking of a 33-ft double to 28-ft double and 53-ft single configurations via simulation and full-scale tests. Novel numerical tractrix models are introduced and compared to existing models commonly used to evaluate low-speed off-tracking of long combination vehicles (LCVs). Unlike pre-existing models, accuracy of one of the proposed models is largely unaffected by input path resolution and regularity—a significant benefit for reducing computational cost and easing implementation for many applications. Full-scale tests are conducted at Virginia Tech and an extensive uncertainty analysis is detailed for the test procedure and measurements. Field tests compare favorably with simulations for all tested maneuvers and trailer configurations and clearly demonstrate the order from least to most off-tracking as 28-ft double, 33-ft double, and 53-ft single. The 33-ft doubles have slightly larger off-tracking than 28-ft doubles, whereas 53-ft singles have substantially larger off-tracking than 28-ft and 33-ft doubles.

The second study evaluates 33-ft double straight-rail trailers rollover propensity with different stability control system implementations: stock (none), tractor electronic stability control (ESC), trailer roll-stability control (RSC), and RSC+ESC. Extensive test vehicle instrumentation and structural reinforcement are detailed for the test preparations. Tests are conducted on a test track with either driver or robot steering. On their own, both ESC and RSC clearly reduce the rollover propensity of the trailers for all maneuvers, and the trailers exhibit the highest roll-stability when both RSC and ESC are active. The tested ESC and RSC modules are off-the-shelf products from industry suppliers chosen by the program sponsor.

The third study compares trailer drum and disc brake performance in three conditions: straight-line braking distance, brake type influence on RSC performance, and roll dynamics in a combined braking and turning maneuver. A braking robot is designed, fabricated, and implemented to provide precise and repeatable brake pedal application. Test results suggest that disc brakes tend to provide reduced braking distance and are less susceptible to brake fade than drum brakes. Anti-lock braking system (ABS) and suspension dynamics react differently to the two brake types. Small, noticeable differences in RSC performance are evident between the two brake types. Within the test limitations, rollover dynamics were not clearly different between the two brake types for braking-in-turn maneuvers, performed for a large range of entry speeds and brake activation delay relative to the start of steering.

vehicle dynamics, long combination vehicles, off-tracking, disc brakes, drum brakes, roll-stability control, electronic stability control