20-04-2012, 11:36 AM
Control Prototyping for an Anti-Lock Braking Control System on a Scaled Vehicle
INTRODUCTION
The design, implementation and testing of advanced controls
has received considerable support from the development
of computer-aided analysis and design tools and more recently
from rapid control prototyping platforms. Commercially
available tools offer a wide range of capability, cost, ease of
use, and compatibility with existing (and future) hardware and
software technologies. Together with virtual prototyping software,
it has become possible to develop sophisticated models,
designs, and simulations on the desktop. This capability can
provide valuable insight into a system’s performance at early
stages in the design/development process.
Physical testing remains an essential albeit costly requirement,
whether for model validation, hardware-in-the-loop simulation,
or to evaluate an embedded control design. Learning
how to use rapid control prototyping tools, and testing and
evaluating designs can be slow and expensive. Cost/timeeffective
physical testing can be employed before full-scale
evaluation, and a traditional approach is to use scaled laboratory
systems to focus on one or more features of interest.
Scaled vehicle testing offers a low-cost solution for studying
advanced vehicle controls, as reported recently by Brennan
and Alleyne [1] and Altafini, et al [2].
CONTROL PROTOTYPING
Control analysis and design has been aided significantly
by modern software tools that combine an interactive user
environment and a suite of canned routines to aid the control
designer. Block diagram descriptions also aid the implementation
of control designs, being compatible with system and
control modeling techniques. Integration of software with
hardware to form control prototyping has made commercial
off-the-shelf products available and affordable for a wide
range of users. These products can significantly accelerate the
development process, and this is one reason for their increased
application. A specific example of the modeling and control
prototyping approach employed in this study is illustrated in
Figure 1. Both Matlab/Simulink and LabVIEW are used to
form a control prototyping approach, utilizing complementary
features to arrive at an effective solution.
SCALED VEHICLE LABORATORY
The laboratory setup consists of a test vehicle (a 1/5 scale
FG Modellsport Posche GT2) complete with a gas powered
IC engine, servo-controlled steering, and servo motor driven
electromechanical disk brakes on the two front tires. The
vehicle has been instrumented for these studies with optical
encoders to measure speed of the two front tires and the rear
differential. A triaxial accelerometer is mounted on the vehicle
body to provide acceleration measurement.
WHEEL SLIP REGULATION IN ANTI-LOCK BRAKING
An Anti-lock Brake System (ABS) is designed to prevent
the wheels from locking up during braking, thereby ensuring
that acceptable levels of traction and lateral stability are maintained
even during emergency braking conditions. Challenges
include implementation and robustness given the wide variety
of road surfaces and terrains that might be encountered, as
well as changes in the vehicle system itself.
CONCLUSION
This paper has presented a basic scheme for control prototyping
using off-the-shelf modeling, simulation, and realtime
control software and hardware. The specific combination
of Matlab/Simulink and Real-Time Workshop with LabVIEW
Real-Time and the Simulation Interface Toolkit has been
described. This platform has been used to develop several
controllers for antilock braking control of a scaled vehicle in
a testing laboratory [5], [6], [7].