A Model for the Mechanical Subsystem of an Air Brake System

This paper presents the approach and methodology of the Large Truck Crash Causation Study (LTCCS), undertaken jointly by the Federal Motor Carrier Safety Administration and the National Highway Traffic Safety Administration. The LTCCS is a study of a nationally representative sample of serious and fatal heavy truck crashes occurring between 2001 and 2003. The data collected provide a detailed description of the physical events of the crash, along with an unprecedented amount of information about the vehicles, drivers, truck operators, and environment. The LTCCS was designed to include all elements in a traffic crash--vehicle, driver, and environment. In addition, extensive information is collected about the operator of each truck involved, including details about driver compensation, vehicle maintenance, and carrier operations. Rather than crash experts assigning causes to each crash, the LTCCS approach is based on statistical associations in the aggregate data. The crash assessment data provide information on what physically happened in the crash, including prior movements of each vehicle, the critical event in the crash, and the reason for the critical event. "Causes" can be determined through the analysis of this information, by identifying associations between vehicle, driver, and environmental characteristics, and particular crash types or modes of involvement. The approach of the LTCCS is consistent with the probabilistic nature of traffic crashes. Analysis of the data proceeds by searching for associations between the various descriptive variables and involvements in particular types of crashes. The broad range of actors included permits a wide range of hypotheses to be tested.

The large truck crash causation study

The safe operation of vehicles on roads depends, among other things, on a properly functioning brake system. Air brake systems are widely used in commercial vehicles such as trucks, tractor-trailers, and buses. In these brake systems, compressed air is used as the energy transmitting medium to actuate the foundation brakes mounted on the axles. In this paper, a model-based diagnostic system for air brakes is presented. This diagnostic system is based on a nonlinear model for predicting the pressure transients in the brake chamber that correlates the brake chamber pressure to the treadle valve (brake application valve) plunger displacement and the pressure of the air supplied to the brake system. Leaks and "out-of-adjustment" of push rods are two prominent defects that affect the performance of the air brake system. Diagnostic schemes that will monitor the brake system for these defects will be presented and corroborated with experimental data obtained from the brake testing facility

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A Diagnostic System for Air Brakes in Commercial Vehicles

A brake warning system for vehicles with pneumatic air brakes monitors various factors to provide an indication of a pending or actual brake failure condition. According to one embodiment, vehicle brakes are tested by determining a delay time between pressure changes in a control brake line from a treadle valve and the response of the brake. According to another embodiment, brake performance is measured by monitoring applied brake line pressure versus known brake performance values. Measurements are taken with the brakes in a known good condition, during a "training mode," and data is then compared, on a continuous basis, with data acquired by ongoing measurements. The invention provides an on-board, real-time, assessment of vehicle brake performance, through measurement of a relatively small number of parameters.

On-board brake warning device for air brake equipped vehicles

Heavy truck deceleration rates as a function of brake adjustment

Continuing research in brake condition monitoring for vehicles equipped with air brakes considers the feasibility of using air pressure data to determine brake stroke, a vital parameter in determining the effectiveness of the total braking system. Recent statistics show there is an alarming number of vehicles operating with brakes that are out of adjustment even with the introduction and requirement of automatic slack adjustment in 1994. The importance of brake stroke information is thus highlighted. To address this problem, a mathematical model of an air brake chamber is developed and used to investigate parameter sensitivity. A method capable of indirectly determining brake stroke by examining air pressure data is formulated and its effectiveness is proven through simulation and testing.

A Model for the Mechanical Subsystem of an Air Brake System

References

The large truck crash causation study

A Diagnostic System for Air Brakes in Commercial Vehicles

On-board brake warning device for air brake equipped vehicles

Heavy truck deceleration rates as a function of brake adjustment

Determination of air brake adjustment from air pressure data