Vehicle powertrains are increasingly automated. The gearshift strategy that is built into an automated (non-powershifting) transmission (AMT) has to determine when to shift and to which gear. AMT has the potential to reduce environmental impact and improve vehicle performance. However, the gearshift strategy is far from obvious, especially for heavy duty trucks with many gears. This paper presents an analytic tool for finding the ultimate gearshift sequence for any given vehicle and driving situation. The paper includes some case studies (uphill acceleration, engine torque down control) that show credible results. The optimisation criterion used is minimum acceleration time. The tool based on a trajectory optimisation method called dynamic programming. There is a certain limitation with dynamic programming: Although it is cery computationally efficient, as compared to testing all possible combinations in the state grid, the required computational efforts increase rapidly if more dimensions are introduced in the state grid. The cost function is formulated using simulation results from a dynamic system model, which can be implemented in Simulink. Simulink is a very commonly used modelling and simulation software and it has an easy interface for defining dynamic models. A general computer code for trajectory optimisation has been developed and successfully applied to gearshift sequence optimisation. The generality is proved by the fact that the code has also been used in another case: fuel consumption optimisation for a city bus with automatic (powershifting) transmission. The analysis of the optimisation results seems reasonable in all aspects, which is why the optimisation method is regarded as credible. Issues which could be adressed in further research are implementation of engine dynamic chracteristics, e.g., turbo dynamics and optimisation of a gearbox layout. This could be done by optimisation of a sequence with a very tightly stepped, virtual gearbox. The gear ratios chosen would then point out the optimal ratio layout for the real gearbox. Another existing attempt to approach optimisation of gearbox ratio layout is based on pure simulation, a statistic test plan and regression.


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    Title :

    Gearshift sequence optimisation for vehicles with automated non-powershifting transmissions


    Additional title:

    Optimierung der Gangschaltungsfolge für Fahrzeuge mit automatisierten Wechselschaltgetrieben


    Contributors:

    Published in:

    Publication date :

    2003


    Size :

    21 Seiten, 18 Bilder, 4 Tabellen, 13 Quellen




    Type of media :

    Article (Journal)


    Type of material :

    Print


    Language :

    English





    Gearshift sequence optimisation for vehicle with automated non-powershift transmissions

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