Effects of driving functions’ reorganization on subsystems in electric drive systems
In context of drive systems’ electrification, drive functions have to be fulfilled by new systems and subsystems. Thereby, various aspects could be differentiated. The first one is the substitution, which means: new subsystems carry over the functions of conventional drive systems. For example, an electric machine replaces the combustion engine within a central drive. Another aspect is a new kind of assignment of established functions to one or more subsystems. Thus, in multi-speed gearboxes the electric machine instead of frictional-locking elements like synchronisation and clutches should perform the synchronisation of speed. In addition, the electrification offers the realisation of new drive functions, which were not feasible yet. These functions are e.g. recuperation and torque vectoring. (s. section 2.2) Especially, if new drive functions have to be fulfilled – like combustion engine start in hybrid-electric vehicles –the consequences for the residual drive system and the user as well as the achievement of development objectives are not evaluable.
Even serial production battery electric vehicles provide less complex drivetrain topologies, it is rewarding to have a look at alternative solutions using multi-speed gearboxes. Thereby, the fulfilment of established functions by new or established subsystems is sufficient challenging the development of electric vehicles regarding the changes in operation conditions.
Manifold possibilities of function realisation in electrified drive systems result in a high degree of freedom within the development. Their benefit and effects have to be analysed considering the interdependencies in whole system context. This article discusses possible solutions of functions’ fulfilment and reorganisation in battery electric drive systems and their benefits. The associated effects on the residual drive system and its subsystems are derived and discussed.
KeywordsElectric Vehicle Drive System Electric Machine Brake System Planetary Gear
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