Specialized Test Equipment

Data Acquisition System

All data is conditioned in instrumentation amplifiers, and anti-alias-filtered in tenth-order 14.2 hz Butterworth active filters. Available conditioners include DC General Purpose; DC Strain Gauge; Shaft Encoder; Frequency Input. The filters use precision operational amplifiers, one-percent resistors, and temperature-stable capacitors matched to 0.1 percent. The filter characteristic is flat to one part in 4000 at 10 hz and is down 66 db at 30 hz. The filtered data is sampled 60 times per second, digitized to 12 bit accuracy and resolution, and stored with 12 channels on one horizontal line of the video recorder. Each data line appears as a dot-dash line across the top of the visible video picture.The digitized data can be shown as an overlay on the video picture, either as a 12 channel horizontal analog bar display, or as a vertical array of numerics, each ranging from -1000 to +1000 full scale. Both displays can be used simultaneously, if desired. The numeric display can be updated 60 times per second, on every video field, for single-framing analysis, or at slower rates (4 times per second and 2 times per second) for real-time viewing. In running the test, these displays are shown on a video monitor usually placed on the floor of the passenger side, for a visual check of proper transducer operation.

Only the data line must be recorded, as the other displays can be regenerated during playback, or recorded on the picture during editing.

The system has a plug-in 12 channel 12 bit Digital to Analog converter module, to provide strip-chart recording capability or analog recording into other data systems.

The system also has a plug-in "RAM Buffer" module, which serves as an interface to an IBM - PC computer. Thru this module, the computer sees the data being reproduced as RAM that is updated with twelve 12-bit data samples in a 53 microsecond burst occurring sixty times per second. Various "handshake" lines and data flags are provided for easy software access.

Unique Capabilities of Data Acquisition System
In many test programs there is visual and auditory "data" which can be seen or heard but not measured. The ATI "Real-time Video Data Acquisition System" (US Patent 4,819,896) overcomes this problem by recording all three sources of information - sight, sound, and instruments - simultaneously and in synchronism, on videotape.

Display Capabilities - The real-time data display overlaid on the video picture has proved to be particularly useful. For example, in accident scene drivethroughs, in demonstration of avoidance maneuvers, and in standard lane-change tests the video picture can be single-framed, with steering wheel angle, lateral acceleration, and other variables shown in 1/30 second increments against the driver's view of lane boundaries or other obstacles.

Video G-G Diagram - The ATI "Driver-Vehicle Display Apparatus" (US Patent Number 4,716,458) shows the instantaneous cornering/braking/acceleration state of a car with respect to its various limits, overlaid on the "Driver's eye view" video picture. With acceleration/braking as the vertical axis and lateral acceleration as the horizontal axis, various diagrams bit-mapped in PROM are used to represent the driver unwillingness limit, the 
vehicle's control limit,  the rollover limit, etc. The actual forward and lateral accelerations experienced by the test vehicle are combined into a moving dot on the screen. The instantaneous relationship between the vehicle and its limits are immediately obvious. The "Video G-G Diagram" has been utilized in demonstrating safety margins in vehicle scene drive-throughs, in showing the severity of lane change maneuvers, and in demonstrating the margins between vehicle handling limits and rollover limits.

Race Car Video G-G - In the adoption of the video G-G diagram, horizontal bar graph representations of throttle and brake are added at the top of the screen, and lap time in a numeric display at the bottom of the screen. The lap time is reset by a radio signal sent by a stopwatch operator at the side of the track.

Real-Time Split Image - The output of up to three video cameras can be combined into one composite picture, maintaining the capability for data overlay. Typical applications have a master "driver's eye" view through the windshield, with smaller picture-in-picture views to show disconnected components, wheel lift, etc. The Heitz PIP system is done in real time, using three cameras and one recorder, for economy and to enhance admissibility.