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

In recent studies, it has become apparent that a set of safety–related performance measures for heavy vehicles can be useful in the design process as well as in the more conventional realm of screening heavy vehicles by regulation. In Canada, these regulations control, separately, the combined trailer length and overall vehicle length, total vehicle weight, maximum axle–load, multiple–axle group spacing, and the characteristics of a few selected components of new vehicles (e.g. service and emergency air and/or hydraulic brake systems). None of the existing regulations has been applied for quantifying the dynamic properties of individual vehicles, either newly designed or already in service; instead they have been used to qualify classes or groupings of vehicles. The objective of this paper is to present an overview of the efforts made in North America to develop a set of safety–related performance measures and promote their use for determining and controlling the dynamic quality of heavy vehicles on an individual basis from both the design and regulatory standpoints.

An overview of performance measures for heavy commercial vehicles in north america.

This report describes the results of experimental evaluation of longitudinal control algorithms for commercial heavy vehicles (CHVs). Given the problem of delays in the fuel and brake actuators of automated CHVs, the researchers present improved modeling of air brakes for CHVs, and novel nonlinear algorithms for the longitudinal control of CHVs without intervehicle communication. The significance of these results in terms of Intelligent Transportation Systems (ITS) deployment is that one of the major obstacles to autonomous vehicle following for CHVs has now been removed The authors also point out that adaptive cruise control can now be implemented in CHVs that are not equipped with Electronic Brake Systems.

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Longitudinal Control Of Heavy Duty Vehicles: Experimental Evaluation

This report focuses on the design of longitudinal control algorithms for commercial heavy vehicles (CHVs). The algorithms use nonlinear spacing policies, backstepping control design, and aggressive prediction schemes to deal with the presence of significant delays and saturations in the fuel and brake actuators. The algorithms can also deal with delays both in the presence and in the absence of intervehicle communication. A by-product on this research is the development of two software packages, Platoon-Builder and TruckVis, for simulation and animation of CHV platoons. Additionally, another important result of this project is a new simplified framework for evaluating the longitudinal string stability properties of platoons of automated vehicles.

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Analysis, Design, And Evaluation Of Avcs For Heavy-duty Vehicles With Actuator Delays

We present adaptive nonlinear longitudinal controllers designed for automated commercial heavy vehicles (CHVs), which take into account the large actuator delays inherent in the air braking system. After a description of the dynamics of air brakes and delay sources, we present a new controller designed using the backstepping technique. We conclude with a simulation results which illustrate the effectiveness of our controller.

Sidney F. Williams

Papers

Antilock Systems for Air-Braked Vehicles

The Importance of Maintaning Air Brake Adjustment