Abstract
ABSTRACT
The paper presents a methodology for the dynamical modeling of automatic transmissions for automobiles, through the use of the bond graph language. Two major approaches were presented, regarding the exemplified automatic transmissions models: the variable-dynamics system (which switches from a dynamic model to another) and the static causality approach (that uses the same state equations for any operation mode of the gearbox). In other words, an exact and an approximate model are analyzed and compared. Some epicyclical automatics mechanicals are modeled in this paper: an older three-speed unit, a four speed unit and a five speed transmission. Bond graph models are given for every transmission, in 1st and 2nd gears, ans in speed phase of shifts. The complex electro-hydraulic control system was not modeled; open-loop hydraulic pressure inputs to clutches and brakes were provided instead. As a basis for dynamic models investigation, a standstill acceleration simulation is performed for every transmission (assuming its coupling with an appropriate engine and vehicle). Conclusions regarding the suitability of various dynamic models are made.