Driver Brake Testing using the DaqBook/100
In an ongoing effort to improve transportation safety, government and private organizations study how drivers behave in emergency situations. This involves using test-and-measurement systems to collect a variety of data.
Application Summary
A major transportation research board funded a project to study safe stopping distances. The objective was to analyze braking behavior when drivers encountered unexpected objects in a variety of road conditions.
To increase test validity, engineers needed to gather data from everyday drivers in their own cars — not professional drivers in test vehicles. This imposed tough constraints on the engineers. For instance, the researchers were not permitted to drill holes or otherwise modify private-owner vehicles to install test equipment, which had to be properly installed in less than 30 minutes. These limitations also prohibited the use of bulky stand-alone strip-chart recorders and large groups of test-and-measurement instruments.
IOtech's Solution
The research team selected IOtech's DaqBook/100, a 100-kHz, 12-bit, portable data acquisition system. Connected to a notebook PC via the parallel port, the system provided the performance and accuracy required for the project. The DaqBook system's extensive line of expansion and signal conditioning options made it ideal for capturing various types of measurements. And the system's compact size — the same form factor as a typical notebook PC — gave the researchers the mobility that they needed.
Connected to various sensors, the system gathered data from four major sources. A pressure switch attached to the accelerator pedal let researchers know how the driver responded to braking situations, and a pressure switch attached to the brake pedal measured driver brake reaction time. Lateral and longitudinal force-balance accelerometers mounted on the floor behind the driver's seat revealed how much left and right swerving the car experienced, and pulse data from a fifth wheel installed on the passenger door helped determine vehicle speeds and distances traveled.
During a typical test, a car was fitted with the data acquisition system within the half-hour limit. Then the car owner drove the vehicle through a series of courses while a researcher sat in the passenger seat. First, the driver was instructed to drive down a road and stop the vehicle when a lamp along side of the road was illuminated. In a similar test, an audible signal was used to determine if there was a difference in reaction time between visual and audible stimuli.
During a second test, the researcher triggered a non-damaging cloth barrier that popped up in front of the car, requiring the driver to quickly stop. Finally, the road course was used to simulate a potential accident scenario: As the driver approached a pickup truck parked on the side of the road, a cardboard barrel was rolled off of the truck's bed and into the driver's path, causing the driver to make an abrupt stop.
Throughout testing, the data acquisition system collected a host of useful information that enabled engineers to evaluate driver-braking characteristics. The results were added to a database that is being used to improve highway designs, driver education, and intelligent vehicle highway systems.
Conclusion
The DaqBook/100's A/D performance and programmable channel/gain sequencer make the system particularly useful for vehicle test applications that require flexibility, high channel-count and fast data collection. The system's extensive I/O and signal conditioning capabilities, combined with its low cost per channel, make it an effective alternative to larger, less-capable strip-chart recorders and groups of test-and-measurement instruments.
IOtech, Inc., 25971 Cannon Road, Cleveland, Ohio 44146. Phone: (440) 439-4091; Fax: (440) 439-4093