Road-Lab-Math Strategy and Implementation in the Development of Manual Transmission Systems

The global engineering community at General Motors pursues the Road-Lab-Math (RLM) strategy as a means of improving efficiency in the product development process. This paper presents the targets of the strategy as pertaining to passenger vehicle Manual Transmission System (MTS) development at Adam Opel GmbH. The term MTS includes not only the base gearbox itself but also the external shift components and the clutch and flywheel system. As part of the RLM approach, current design criteria for components and subsystems are being optimised for even better correlation with customer expectations. At the same time, there has been significant progress in transferring dynamic MTS testing and validation from the road and vehicle to the test rig. Prerequisites for this are highly dynamic electric test benches, capable of simulating both combustion engine torque irregularities at the transmission input and wheel slip at the output. General durability tests, transmission specific high load tests as well as misuse procedures can be pulled ahead in time, now no longer relying on prototype vehicle availability. Track based testing methods with virtual vehicles being driven across a digitized proving ground enable flexibility: vehicle specific parameters, such as weight, engine torque maps and rolling resistance, can be varied effortlessly. Inherent driver variation when testing in vehicles is more significant for some subsystems, e.g. clutches, than others, e.g. bearings. It is statistically evaluated and taken into account during parameterization of test rig procedures.