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The Design of Advanced Transmissions
Technical Paper
2006-05-0297
Sector:
Language:
English
Abstract
This paper describes the creation of novel transmission
mechanisms, both conventional as well as hybrid, using algebraic
design techniques. The objective is to create novel transmissions
comprised of one or more planetary gear sets, a pair of
motor-generators and several torque-transmitting mechanisms
(clutches and brakes). The algebraic design procedure represents
the planetary gear sets, fixed interconnections, clutches/brakes,
and motor-generator sets as algebraic constraints. Appropriate
subsets of constraint equations are solved to identify viable
transmission mechanism designs.
The steps of the design methodology may be summarized as
follows. After deciding on the number of planetary gear sets,
clutches, brakes, and motor/generators to be used in the proposed
transmission, we enumerate by computer, all possible kinematic
combinations of these elements to create an exhaustive candidate
pool. The transmission governing equations are then used to
identify viable candidates. These constraint equations include
requirements on torque ratio values, ratio steps, ratio spread,
shift complexity, and element speeds. In the case of hybrid
transmissions, we also investigate the level of electrical energy
required and the ability to execute mode-shifts. The design process
uses graph theory to handle issues related to mechanism planarity
and isomorphism. Following the identification of attractive
transmission candidates at the lever diagram level, we prepare
layouts and detailed stick diagrams, taking into account the
packaging of bearings, hydraulic circuitry, supporting shafts and
structures.
We have used the above design approach to create several novel
candidate multi-speed transmissions as well as EVT concepts. The
main benefit of the algebraic design procedure is that it allows
the designer to generate and assess novel designs without relying
on intuition and prior experience. Another benefit of the above
design procedure is its ability to identify minimum-content
designs, wherein the emphasis is on achieving the maximum level of
functionality with the fewest components.