Development of Transmission Hardware-in-the-Loop Test System 2003-01-1027
The automotive industry has long relied on vehicle testing to evaluate drive train components for new vehicle applications. In the past it has been impossible to fully evaluate components such as transmissions in a laboratory environment using electric motors as prime movers and absorbers. Although some durability and performance testing can be accomplished on such test stands it is impossible to perform high fidelity controller calibrations, durability tests, and NVH evaluations. Since the electric motors on these test stands cannot duplicate the exact characteristics of an engine such as inertia and firing pulses many manufacturers have resorted to vehicle testing or engine driven testing.
Vehicle and engine based tests have many downfalls that could be avoided through the use of a laboratory based test system with electric prime movers. Vehicle testing with human drivers is often subjectively controlled and the exact test conditions are often unrepeatable. Vehicle tests are subject to weather changes and other environmental factors that can fluctuate tremendously during a test program. Engine driven testing requires special facilities with exhaust removal systems and fuel storage capabilities. Engines require more maintenance than electric motors during lengthy durability tests. The biggest downfall to vehicle and engine driven testing of drive train components for new vehicles is that power train engineers often wait months for prototype vehicles and engines to become available for there test programs. This is especially frustrating to drive train engineers because in most cases they want to utilize existing transmission designs for new vehicle applications. They simply modify or recalibrate a transmission from their product line to work in the new vehicle with a new engine. The drive train development team has to wait months before they know if an existing component will work or if a new design is needed. It is not beneficial to the schedule of a new vehicle launch to perform the engine and drive train development in series rather than in parallel.
The solution to this problem is to develop a transmission test system that can simulate all characteristics of an engine and vehicle through the use of properly controlled electric motors. The reasoning behind this solution is that even if the new engine or vehicle does not yet exist there are computer-based models that can predict the performance of a concept engine or loads of a vehicle.
The objective of this paper is to review the development of a laboratory based test system that uses electric motors and real time physics based models to subject a transmission to transient loading conditions that are identical to those experienced in an actual vehicle.