Delphi Automotive uses VisSim to Reduce Brake Control System Prototyping Time from
2 Months to 2 Days
Author: Gary Fulks, Senior Design Engineer at
Delphi Automotive describes his use of VisSim & VisSim/RealTime to Peter Darnell,
President of Visual Solutions.
In the past, it took up to two months of special
machine shop work, circuit design, hand coded software development and
in-car testing to determine whether a design was feasible for production.
Now, with the combination of fast and powerful block diagram-based modeling
and simulation software from Visual Solutions and highly reliable, noise-immune
data acquisition cards from National Instruments, such testing can be
done in two days or less.
Delphi Automotive configured a system of VisSim running on a lap top with two
PCMCIA DAC Card 1200s, 16 analog inputs, 4 analog outputs and16 digital
I/Os. With their complex control system, they achieved closed loop sampling
rates of over 200 Hertz running a 100 MHz Pentium laptop. VisSim/Real-Time
is capable of closed loop sampling rates of up to 5000 Hertz depending
upon the complexity of the closed loop system and the CPU speed.
A typical use of this setup is to test out electronic braking assist equipment.
Both the closed loop control as well as data logging can easily be developed
and configured with VisSim. Once the sensors and equipment under test
are installed in the vehicle, it is a simple matter to mount the laptop
in the passengers seat, secured with a standard 2" nylon web tie-down,
then plug in the ribbon cables to the DAQ Card 1200s, and turn on the
laptop. Because it is difficult to view the laptop display during daylight
driving, an LED display panel, driven by the digital I/O of the DAQ Card,
is used for critical function monitoring. Five-minute runs with strip
charts tracking user inputs, pedal pressures, accelerations, controller
outputs are typical.
In over a year of use, VisSim has never failed
during a real-time run. The system has proven robust under the harsh demands
of vigorous brake testing, lack of good electrical ground, wide temperature
and humidity variations common to Ohio, and general garage lab treatment.
We also use VisSim in lab bench situations such as automated performance
testing of hydraulic valves. Using map blocks, it is easy to create time-based
test sequences and correlate sensor outputs with command inputs. The wide
array of plotting capability and data export makes it easy for data analysis.
We feel that VisSim has been an important addition to the set of tools
we use in automotive design and test.
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