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UBC Theses and Dissertations

Roll sensing of heavy trucks Cocosila, Mihail


Rollover, according to accident statistics in North America, is not the most frequent cause of road accidents but is the most significant cause of injuries and fatalities within the trucking industry. The Fatal Accident Reporting System (FARS) for 1991 shows that 23.8% of the deaths occurred in this type of accident. Furthermore, this type of events caused significant damages to the environment and public health as 95% of the accidents involving bulk spillage of hazardous commodities were caused by rollover. There are many factors which contribute to a rollover event: high center of gravity loads, loads which can shift laterally, excessive speed entering a corner or lane-changing and the need to execute emergency maneuvers to avoid an accident, to name a few. Because of economic constraints, the only direction which can be acted upon with efficiency today for reducing rollover incidence seems to be the human component of the accidents. It was noticed that the human factor intervenes not only due to the errors but also due to the limitations of the human being. It is reasonable to assume that incidence of some rollover accidents (those assessed as "preventable" or "potentially preventable" only) might be reduced if early warnings were given to the driver in an incipient stage of the progression towards an accident. The driver thus warned might be able to stop the progression and avoid an accident. Alternately, a warning device might educate a driver to avoid potential accidents. The objective of this work is to develop a method for sensing the roll motion of a heavy truck. In order to reach the above objective, the mechanical factors associated with rollover are first explored. The roll behavior diagram for a one-axle and a three-axle heavy truck model are presented and discussed. As it was found by several authors that the rollover threshold of a heavy truck is closely related to the tractor drive axle wheel lift-off, several possible approaches for detecting the progression towards this moment are examined. Both theoretical solutions and already existing devices are critically examined. A solution for roll sensing by means of tilt sensors is then presented and supported with theoretical and practical arguments. The most important one is that a rollover warning device should be placed entirely on the tractor of a tractor-trailer combination as many tractors pick-up and drop-off a variety of trailers. The work also presents static, dynamic and on-road tests done in order to assess the suitability of a commercial tilt sensor for the roll sensing purpose. A special arrangement of tilt sensors was mounted on a minivan featuring a truck-like rear axle and on-road tests were performed. All of the tests done show that roll sensing of a road vehicle may be done by means of an arrangement of tilt sensors. This information might provide a good indication of the roll state of a vehicle and, by extrapolation, of its progression towards rollover. Obviously, further tests performed on heavy trucks are yet necessary before assessing the accuracy of the roll sensing method presented here. Other aspects such as reliability and, especially, cost should be also examined before concluding upon the feasibility of a rollover warning device based on the roll sensing method described in this work.

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