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A simplified, modular, and generic simulation model of an automatic transmission has been developed for use in control system development. This model employs a two clutch concept to simulate the range pack of an automatic transmission. As a result, this model can be adapted to any transmission which relies on clutch-to-clutch (oncoming and offgoing) shift transitions. The model simulates rotating clutches as well as stationary clutches by simply setting the proper gear configuration and ratio around the clutch. The model is capable of continuous simulation of the power train by instantaneous change of gear ratio and associated parameters particular to each shift. Lockup clutch and torque converter models are integrated in parallel and represent the alternative power paths between the range pack and engine. Also included are models of the engine, brake, retarder, and road load. An optional hydrostatic steer model is also incorporated.

As regulations continue to require low and ultra-low vehicle emissions, Hybrid Electric Vehicles (HEV) are becoming an increasingly popular and attractive alternative to conventionally powered vehicles in the light, medium and heavy-duty markets. Computer modeling and simulations are used to develop HEV control algorithms and to investigate various system configurations. The use of simulations significantly reduces development time and expense. Additionally, the HEV designer is afforded a level of freedom to experiment with various algorithms and configurations without the expense of building prototypes for each new idea. This paper examines the modeling and simulation efforts currently being applied to hybrid electric vehicle development at Allison Transmission.