This dissertation deals with the development of a model-based diagnostic system
for air brake systems that are widely used in commercial vehicles, such as trucks,
tractor-trailers, buses, etc. The performance of these brake systems is sensitive to
maintenance and hence they require frequent inspections. Current inspection techniques
require an inspector to go underneath a vehicle to check the brake system
for possible faults, such as leaks, worn brake pads, out-of-adjustment of push rods,
etc. Such inspections are time consuming, labor intensive and difficult to perform
on vehicles with a low ground clearance. In this context, the development of an onboard/
handheld diagnostic tool for air brakes would be of significant value. Such a
tool would automate the brake inspection process, thereby reducing the inspection
time and improving the safety of operation of commercial vehicles. In this dissertation,
diagnostic schemes are developed to automatically detect two important and
prevalent faults that can occur in air brake systems â leaks and out-of-adjustment of
push rods.
These diagnostic schemes are developed based on a nonlinear model for the pneumatic
subsystem of the air brake system that correlates the pressure transients in the
brake chamber with the supply pressure to the treadle valve and the displacement of the treadle valve plunger. These diagnostic schemes have been corroborated with
data obtained from the experimental facility at Texas A&M University and the results
are presented.
The response of the pneumatic subsystem of the air brake system is such that it
can be classified as what is known as a âÂÂSequential Hybrid SystemâÂÂ. In this dissertation,
the term âÂÂhybrid systemsâ is used to denote those systems whose mathematical
representation involves a finite set of governing ordinary differential equations corresponding
to a finite set of modes of operation. The problem of estimating the push
rod stroke is posed as a parameter estimation problem and a transition detection
problem involving the hybrid model of the pneumatic subsystem of the air brake system.
Also, parameter estimation schemes for a class of sequential hybrid systems are
developed. The efficacy of these schemes is illustrated with some examples
