Gentlemen, start your computers

DN Staff

May 5, 1997

14 Min Read
Gentlemen, start your computers

How often would you want a driver taking his eyes off the track while clocking 250 mph to check the speedometer? the oil gauge? throttle position?

Data-acquisition, or DAQ, systems can do the checking far more often than any driver--they check car sensors and store the reading every tenth or hundredth of a second. Actually, sensors continuously measure oil pressure, wheel speed, suspension movement, and dozens of other parameters. An on-board computer samples the sensor readings at specified time intervals, and stores the data while the car circles the track. Much of this equipment is standard on Indy cars.

There are two ways to get the data from the racecar computer. Many teams transfer data through a cable to a laptop computer while the car is stopped in the pits. Most Indy cars transmit data to a trackside computer by radio, either in real time or in burst mode.

What to do with all this data? Dragsters can generate 16 mega-bytes in 5 seconds. Engineers use PCs with specialized software to analyze the data and display it graphically in just seconds. The results don't yield immediate answers, but point to what direction to take the vehicle setup or how to improve driver technique. Vehicle changes can range from changing entire parts for improved aerodynamics to modifying the igni-tion timing.

Many professional racing teams run two cars so they can collect data twiceas fast. Data from each car can be superimposed on a graph to show where one driver is faster on the track than another. Engineers can use the data to speed up the slower car. Also, engineers can make different changes to a car to ad-dress the same problem, and see which setup works best.

Data recreation. Gary Denton, an engineer for Penske Racing, which participates in the CART (Championship Auto Racing Teams) series, uses a data-acquisition board from Keithley-Metrabyte that has two analog outputs to test Indy cars.

The setup is a chassis rig with a hydraulic ram at the front corner of the car that recreates a lap to test the suspension, wheel, and shock. Road input comes from the Keithley DAS-1802 card's outputs.

The card acquires road data from a DAQ system that actually sits in the car during races. "Our cars have a DAQ system from Pi Research Ltd. (Cambridge, England) that measures suspension travels and loads," says Denton. Approximately 100 channels working at different rates collect 200 kbytes per lap in the Pi system.

The DAS-1802 ISA board acquires data at 333,000 samples/sec, and offers 16 single-ended or 8 differential inputs. Its two analog outputs can send the collected data to actuators or other devices for engineers to experiment and evaluate.

An IBM 486-based desktop PC that is part of the test rig interfaces to the Keithley card via Visual Basic. During the test, engineers measure tire deflection and accelerations that are difficult to measure while the car is actually racing because of engine vibration. On the chassis rig, the engine isn't running.

Engineers view the data with Excel and use results to tune the dynamics of the car; for example, changing damping and spring rates to minimize accelerations.

"We focus on making the cars better," says Denton. "Our drivers are Al Unser Jr. and Paul Tracey, who usually finish a tenth to a hundredth of a second of each other and don't need us telling them how to drive.

"Cars are always going to get faster," continues Denton, "Everything steps up, and DAQ has accelerated that."

As speeds increase, the racing rules change to slow them down for safety reasons. This year, the maximum turbocharge boost for CART cars has been reduced from 45 to 40 inches, which reduces horsepower by about 100 hp. Also, the car aerodynamics has changed to reduce downforce by about 20%, which reduces cornering speeds.

Five-second race. Kell's Automotive, in Las Vegas, uses National Instruments' LabWindows/CVI version 4.1 for Windows 95 as the user interface and control software for custom data-acquisition hardware it designs to take data on engine parameters and optimize race performance. The software package lets users generate C code to control data-acquisition systems--as well as any "virtual" instruments--using function panels instead of writing the code line by line. Kell engineers also write a lot of their own C code, and call it up from LabWindows/CVI.

The heart of the custom DAQ system is a ruggedized computer designed and built by Terry Kell and his partner Blake Gover over the last seven years. The biggest challenge for them was making sure the system would work in the harsh racing environment.

"Just about everything you don't want around a computer is in a racecar," says Kell. "With the cars we run, the ignition's wires can't be radio-suppression wires. And so the interference is just massive. Most computers, when you get them anywhere near an engine like that, they just flat sign off."

Kell and Gover designed their computer in their own engine shop. Most DAQ hardware is usually designed in some electronics firm and then adapted to the automotive world.

The John Force drag racing team is currently using the system. Force, the six-time Funny Car champ, was elected Driver of the Year in 1996--the first time in the award's 30-year history that the honor has been bestowed on a drag racer. He set the national elapsed time record of a quarter mile in 4.88 seconds while racing at Heartland-Park Topeka in July 1996, making him the first Funny Car driver to break the 4.90 barrier.

"On Force's car, we're sampling 100,000 samples/sec/channel on four analog and four digital channels" says Kell.

The digital channels monitor engine speed and crank-shaft harmonics by reading zero-speed digital magnetic sensors.

"One of the things we measure that people said we'd never be able to get on an engine like this is cylinder pressure inside the combustion chamber," beams Kell. "We have a fiber-optic analog sensor mounted inside the cylinder that reads the pressure as it builds."

Analog channels also monitor the ignition wave trace. When the spark goes to the cylinder, it creates a wave pattern that Kell logs so he can categorize it to make sure the ignition timing is where it should be. Otherwise, warns Kell, the performance suffers or the engine can explode when the car is halfway down the track.

Engineers turn on the DAQ computer in the dragster just prior to making a run. Kell built a special fiber-optic communications link to download data at the end of the race because that way the data couldn't be corrupted from other cars. Plus, they wouldn't have to worry about electrically glitching one computer or the other by plugging them in when both are turned on. The 4 million byte/second data-transfer rate certainly didn't hurt matters, either.

On one 5-second run, the computer acquires about 16 megabytes of data. "You have to be able to get it out of the car in a hurry and look at it and decide what adjustments to make for the next run," stresses Kell. As the day goes on, the runs get closer and closer together--the minimum time between races is about an hour and a half. "But you gotta realize they've got to completely disassemble the car, completely disassemble the engine, put everything back together, have it fired up, checked, and back up at the line in that time. And somewhere in there, somebody's got to analyze all this data."

First the engineers download the data into an off-board computer that sorts the data and presents it in a graphical format. Kell estimates that they have the data up and analyzed within two minutes. "We picked LabWindows/CVI because it gets rid of that mundane task of generating all your grids for the graphics," he says. "We'd have to reinvent the wheel if we didn't have a software package like that."

After analyzing the data, the team sometimes makes adjustments right away for the next race. Other times the data leads engineers to machine different components to counteract a problem in a future race.

The process never ends: "There's no such thing in racing as a perfect car," notes Kell. "You always know you can go faster."

Speed records have been broken because of the increased sophistication of data acquisition and the lessons engineers have learned, according to Kell. In the world of drag racing, there was a major increase in performance and reliability when the DAQ systems started appearing on racecars about 15 years ago. The race continues for the most perfect car possible.

Built for racing. Indy cars, such as the ones Penske races, come with a built-in digital dashboard and an optional data-acquisition and telemetry system from Pi Research.

Pi supplies "black box" data loggers, transmitters, receivers, motor racing computers (MRCs), programmable LCD dashboards, and software that lets the teams gather, display, and analyze telemetry data and make changes to the cars' suspension, shocks, aerodynamics, engine, and tires.

Pi also supplies sensors for engines, tires, suspension positions, and strain gauges mounted on the suspension tubes to sense load, as well as steering angle, throttle angle, and brake line pressure sensors.

Pi's systems have a connector that lets the vehicle's engineers plug in signals coming from the engine. The system generates more than 1,000 direct and derived parameters that enable the engineers to continually monitor and fine-tune the car. During a race, a car's transmitter sends data to the pit. At the race's end, engineers plug in their laptops to download data from the MRC's RAM so they can analyze the entire race.

Trucking for data. Indy car racing is comfortable compared with off-road truck racing--a brutal sport for both truck and driver. Races cover 500 or even 1,000 miles of rugged desert terrain with drivers maneuvering their trucks as fast as possible over bumps--often flying 6 to 10 feet in the air. The primary factor limiting truck speed under these conditions is driver discomfort, making the suspension system the key to a winning vehicle.

The bumps are 2 feet tall and spaced about 30 feet apart. Without a good suspension system, the jarring becomes so great that the driver is forced to slow down. A suspension that permits a great deal of wheel travel integrated with precisely tuned shock absorbers lets the tires "kiss" the tops of the bumps. Since the cab remains level, the driver can maintain speeds of 60 to 90 mph.

A typical off-road truck suspension has up-and-down wheel travel of 24 to 30 inches in the rear wheels and 18 to 25 inches in the front. Each wheel sports three shock absorbers with remote reservoirs for cooling fluids. A high degree of wheel travel is an advantage in rough terrain because it allows a truck to stay on top of bumps and skip across them, rather than crawling up one side and down the other.

To perfect a suspension system for Team MacPherson's off-road truck, Light Racing Inc., Catheys Valley, CA, tested system components under simulated race conditions and recorded performance data using the Model 2100 Field Computer System from SoMat Corp., Champaign, IL. This small, portable data-acquisition system withstands the elements and is rugged enough to take the jolts of off-road racing.

The Model 2100 is a series of stackable modules in a bus-like architecture. Up to 20 modules can be stacked to handle virtually any data-collection chore. Reconfiguring the system to acquire different data involves removing one module and adding another, and modifying the test setup file using SoMat's Test Control Software on a notebook computer. After collecting data, engineers can transfer it to another computer or software package for further analysis.

With the goal of increasing tire contact with the ground for as much traction as possible, Light Racing performed tests to perfect the shock-absorber system. The shocks used on off-road vehicles differ from typical velocity-sensitive shocks--they also provide position-sensitive control. With increased speed, normal shock absorbers deliver increased load, regardless of wheel position. An off-road race vehicle needs a shock that gets stiffer as the wheel travels up farther--shock absorption is a function of wheel position in addition to velocity.

To take full advantage of position-sensitive shocks, engineers needed information about wheel position during a race. Position transducers attached to the wheels were connected directly to the Model 2100, located in the cab, to record wheel position during a simulated race. Position data also gave them wheel velocity since velocity is a function of time, which was continuously monitored by the 2100. By determining wheel velocity in various positions of wheel travel, engineers were able to fine-tune the shock-absorber valves for optimal performance at all wheel positions--and a much more comfortable ride for the driver.

Anatomy of a data-acquisition system

Many data-acquisition systems involve a desktop or laptop PC to store, analyze, view, and archive data. For racing applications, these PCs need to be tough. Whether they're in a vehicle, in the pits, or in a trailer, the PCs need to stand up to electrical noise, vibration, heat, and dust.

A typical PC-based data-acquisition (DAQ) system also includes software, a plug-in DAQ board containing analog-to-digital signal-conversion circuitry, sensors, and signal-conditioning hardware. The memory of the PC on board the vehicle stores the sensor readings. After transmitting or downloading the data to another computer--usually a battery-powered laptop--the on-board computer is reset and ready to gather more data.

Easy-to-use software is a necessity for PC-based DAQ systems--some packages require no programming, and some offer intuitive graphical programming. Driver software provides access to DAQ-board functions. And application software simplifies combining those functions with data analysis and presentation.

The most common DAQ hardware device is a multifunction board. It typically has analog inputs for measuring parameters such as voltage and temperature, digital inputs for sensing power outage or switch closures, digital outputs for controlling power to equipment, and timing I/O for synchronization. It may include analog outputs for generating calibration signals or outputting sampled waveforms.

Analog sensor outputs typically monitor parameters such as temperature or force. For example, thermocouples, thermistors, and RTDs typically measure temperature; strain gauges measure force.

In most cases, the analog signal a sensor generates requires conditioning before it connects to an analog input on the DAQ board. Signal conditioning can be amplification, filtering, linearization, or cold-junction compensation for thermocouples. Strain gauges require excitation and bridge completion. And digital signals are computer-ready.

CART, IRL change the rules

Two groups race Indy cars: Championship Auto Racing Teams (CART), a group founded by Indy car owners Roger Penske and Pat Patrick in 1978, and the Indy Racing League (IRL), a new Indy car circuit started by the president of the Indianapolis Motor Speedway (IMS). The IRL held its first race in January 1996; its 5-race circuit includes the Indianapolis 500, held at the IMS.

Last year, the IRL's first season, CART ran the U.S. 500 at Brooklyn, MI, on the same day as the Indy 500. This year, CART has backed off the direct challenge, running a race instead on the day before the 500 at a new track near St. Louis.

A recent out-of-court settlement between CART and the Indianapolis Motor Speedway has opened the door for CART teams to again take part in the Indy 500--the sporting world's richest and most prestigious race.

In 1996, the IRL used racecars that were similar to those CART used. But this year, the IRL has all new cars and engines. For example, CART still uses 2.65l turbocharged engines, but 1997 IRL cars have 4.0l engines without turbochargers. Thus a CART car cannot run an IRL race.

Derrick Walker, the last CART owner to also participate in the Indy 500 says he won't be at Indianapolis in 1997 because he doesn't have the resources to field two different cars.

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