“Real-world” fuel consumption and emissions testing is becoming central to OEM new car/new powertrain programs. But it brings new challenges and potentially financial headaches to a highly complex area. A major concern is the efficacy of virtual testing—long established as part of vehicle development and a huge contributor to cost saving—in meeting real world driving emissions (RDE) legislation requirements.
Helping to achieve that is the aim of U.K. software specialist rFpro, which has extensive experience in virtual road and track (via F1) testing; see http://articles.sae.org/14181/ and http://articles.sae.org/13603/.
Chris Hoyle, rFpro’s Technical Director, states that creating a fully convincing virtual environment, in which a driver feels totally immersed, enables driver-in-the-loop (DIL) testing with a driving simulator to be applied, for what he claims as the first time, in areas where human reaction to a situation affects the vehicle’s behavior.
“Used effectively, virtual testing enables critical decisions to be made early in an automotive engineering program and certainly long before any commitment to significant financial investment," Hoyle told Automotive Engineering. "One such area, not previously associated with simulators, is emissions testing because when RDE tests take the place of today’s artificial rolling road test cycles, variations between different drivers will significantly influence the results obtained.”
RDE tests will be influenced by driving style and road conditions, said Hoyle. But the capability to evaluate the vehicle’s behavior under repeatable laboratory conditions using drivers of different abilities and with different habits in order to maximize confidence ahead of approval testing, can provide a massive saving in costs and time.
“One of our clients estimates that over 30% of the costs incurred in developing driving attributes could be saved by frontloading the engineering activity on a DIL simulator with subjective feedback,” he noted.
Virtual technology testing has been accepted for many years, its scope having broadened to embrace evaluation of the effects of a very wide range of areas under repeatable conditions, without weather or traffic variations. However, where human driver input is required, virtual testing "is of little value unless that driver responds to the test scenario in exactly the same way as he or she would do in a ‘real world’ situation,” explained Hoyle.
The need to ensure, in advance, that a vehicle will achieve the target results during RDE testing threatens to add significant additional cost to the typical development program. Understanding driver influenced variables, such as poor throttle modulation when cruising, or failure to anticipate traffic ahead reducing speed, will be central to optimizing the calibration of the vehicle.
Quantifying the influence of driving habits on vehicle emissions is difficult and time consuming using on-road testing. Software developed by rFpro for DIL simulators creates a sufficiently high level of realism that drivers behave in a representative way, claims Hoyle. He said this gives manufacturers the necessary confidence that a car’s virtual emissions performance, in the hands of a human driver using the simulator, "will be equivalent to its ‘real world’ results.”
Historically, driving simulators have reacted too slowly to driver input to create the realism necessary to trigger driver behavior that is fully representative of ‘real-world’ driving. But when used with the latest generation of lighter motion platforms with faster responses, rFpro’s software is designed to provide what Hoyle regards as “unprecedented realism” via use of lag-free, high resolution graphics and finely detailed road surface models including cambers, gradients, bumps and potholes.
This allows vehicle manufacturers to identify and isolate those aspects of human driving which differ significantly from computer controlled operation.