Video of the 2005 NHR Lola Champ-Car performing constant-radius-corner maneuvers around circles marked on the vehicle dynamics area surface.

Six-time Champ Car World Series winner Newman/Haas Racing has refocused its simulation activities to include tire models and rough road surfaces in its vehicle dynamics simulations for predicting handling.  Tires and rough road surfaces are crucial for damper setup and for predicting and understanding how a car will handle on a given track.  Accurate tire models are difficult and costly to generate and the ability to run vehicle dynamics predictions and damper simulation over a rough surface can be cost prohibitive.

Since its first season in 1983, Newman/Haas Racing has collected many wins, poles and track records with talented drivers such as Mario and Michael Andretti, Nigel Mansell, Cristiano da Matta and most recently, Sebastien Bourdais. These have resulted in one of the most successful racing teams in the history of Champ Car.
 
Owners, Paul Newman, one of the most famous actors in the world, and Carl Haas, "One of the most powerful men in the history of auto racing - USA Today," have won six Champ Car Championships, and started their 24th season with a win in the 2006 Toyota Grand Prix of Long Beach.

Building cars to achieve and maintain such success requires continuous innovation and engineering excellence.  Using a manufacturer's tire model that only predicts smooth surface performance instead of replicating the rough surface of a real track produces inherently inaccurate results.  Obviously, the need is for accurate results leading to improved handling and the potential for more wins.

Tire Modeling and Simulation

"The first thing to understand whenever generating a vehicle model is that the most important and the most difficult part of the car to characterize are its tires," said Brian Lisles, general manager, Newman Haas Racing.  "Typically, racing teams rely on tire companies to provide tire data, but tire testing machines are expensive to operate and the tire companies don't necessarily generate the required data or in the manner required by the racing team."

Newman/Haas Racing uses equipment that allows the tires to be tested on the car and measure the forces and moments produced by tires.  In order to understand exactly how the tire is presented to the road, the team uses ADAMS/Motorsports to emulate the maneuvers performed during the test, thereby producing and defining the same conditions that existed when the tire data was measured. 

This involves running the vehicle in constant-radius circles on a skid-pad at gradually-increasing speeds, running at fixed speed with either stepped or gradual steering inputs or emulating an on-track corner-entry/mid-corner/exit maneuver to gather steady state and dynamic tire information.  A skid-pad is a large flat area made of the same material as a race track. 

All of the data is measured and recorded and then regressed to produce a tire model.  The model is input to ADAMS to make sure its behavior matches the observed behavior of the tire during the physical test.

"Effectively, we do our own tire testing to create our own tire models, which is time and cost effective," said Lisles. 

Rough Road Handling

In the past, tire data measurements were made on a smooth surface, so when dynamic simulations were run, the user must assume a smooth surface.  All the irregularities and bumps inherent in a real race track are absent - an idealization applied when performing pure handling analysis. 

"We use ADAMS as a virtual a 7-post rig, i.e. put the car on four hydraulic platforms, vibrate the platforms underneath the wheels, and observe the response of the car," said Lisles.  "Consumer cars use four post test methods, but a racing car requires three more actuators to apply the downforce, which is the aerodynamic load applied to the body.  We built an ADAMS model of the vehicle/rig system and then validated the virtual vehicle and test rig against the physical ones."

This is a very straightforward thing to do.  Having validated the results, the standard vehicle handling model can be run on a rough road instead of just a smooth road.  This allows damper (shock absorber) development and setup to take place virtually, instead of requiring a four-post shake test. 

Conclusion

Newman/Haas Racing has been using ADAMS to process independently-gathered tire data that can be applied to a dynamic vehicle simulation on a rough surface.  This enables their engineers to develop and tune damper settings for cornering over a rough road.

"There are several ways of achieving our objectives including measuring real car data and working backwards to construct why the car responds the way it does.  The surface determines how the car responds.  The information can be regressed from the measurements to what the road surface would be to make the car respond in that manner." 

To achieve this, a high fidelity model is required, which is why Newman/Haas Racing validates the ADAMS/Motorsports handling model on a virtual seven-post shake rig.  The virtual model provides the flexibility of applying any input to the vehicle to produce a simulated response.  
By making a virtual rig in ADAMS and correlating the results, the tire parameters can be adjusted until they match physical test results.  According to Lisles, the engineers get the same response with the ADAMS model as measured on a test rig. 
"In an ideal world, we could measure the track on a Friday afternoon, send it away and Saturday morning process the information, run the analysis and have suggestions for solving any problems," said Lisles.  "We were trying to improve the vehicle dynamics simulation to answer more and more questions.  We kept finding the tire information was out of date and wasn't what we wanted.  With ADAMS, we found a way of overcoming the inaccurate data problem using the current tires and eventually we'll be able to do this very quickly."

"Instead of using expensive rig test time to test tires, we can just go and run a series of standard tests and get the information," said Lisles.  "The nice thing is you are running on a real surface with a real car at real speeds.  It's the real thing compared to just doing it on a tire testing machine."