COSWORTH MOTION CONTROLLER
A major Japanese car manufacturer has made important gains in vehicle development thanks to implementation of a new Cosworth Motion Controller (CMC) system, which has improved the speed, accuracy and value of its windtunnel work.
The CMC, which had previously been deployed on scale models at the Penske Technology Group (PTG), augments Cosworth’s Diablo suite, which is designed to enhance productivity and repeatability in the windtunnel environment.
The CMC provides dynamic and precise attitude control of vehicles, leveraging the speed and accurate timing of EtherCAT®. The solution uses real-time, closed-loop control, based on measured axis feedback, to compensate for vehicle or motion system deflections. The result? Optimised repeatability.
In this latest commission, the CMC allows the manufacturer to control full-size vehicles that sit on a moving belt on standard, flexible tyres. The size and mass of the cars, plus their elastic link to the road create unique challenges for accurate, fast positioning as oscillations may set in.
The CMC has been tuned to prevent such oscillations from occurring. Modifications allow for the large, undamped mass of a car on flexible tyres, with a non-linear suspension. Out of the box, the CMC has provided a significant improvement in positioning accuracy, 0.1m vs. 0.4mm, as well as a 40% reduction in test time.
More importantly, the CMC introduced continuous motion playback to full-size car testing, which allows for even greater efficiency and gathering of richer data. In this mode, a long motion profile is predefined, through which the vehicle moves continuously with concurrent data acquisition. It also greatly reduces vehicle set-up time by removing the need to conduct a time-consuming motion calibration prior to running.
“This second deployment of the CMC demonstrated its capability to control the attitude of full size vehicles in a wind tunnel very accurately, successfully coping with flexible tyres and no damping,” said Cosworth. “Support for conventional point-to-point motion and continuous profile playback led to reductions of test time in excess of 40% out of the box, with potential for further improvements. The CMC’s ability to cope with non-linear suspension systems with no need for prior calibration saves a significant amount of vehicle setup time, greatly improving productivity.”
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