Practical cases

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Powertrain control

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Powerful and comfortable powertrain control

For more than 10 years, Acsystème has cooperated with PSA in designing innovative powertrains. These innovations deal with the transmission system (robotised gearbox, clutch control …) or the whole powertrain, particularly with hybrid systems. In the last few years, Acsystème has acquired strong competencies in modelling and conceiving control for this kind of systems.

Projects of this kind generally go through the following steps:

  • Physical modelling of mechanical components and related actuators (hydraulic and electric): we collaborate with PSA’s specialists to define and build the models that will be used to conceive and validate the control system.
  • The creation of the control system aiming for a comfortable driving experience and a consumption optimisation. At this step, the major difficulty is to synchronise the different actuators control on the whole powertrain (for instance, while taking-off or switching gear with a piloted gearbox). We participate in projects involving eight different actuators that need to be governed in a coordinated manner. To respond to this need, we developed a generic, flexible and modular architecture for a control system.
  • Validation and implementation of the control system into a dynamic simulator. This system is coupled with several projectors and speakers to reproduce vehicle behavior in a very realistic way.
  • Validation and implementation of the control system in a vehicle prototype, only if previous tests were conclusive.

Matlab/Simulink/Stateflow environment is used to develop these projects. In a first step, tasks are realised by performing simulations on a computer. Then, real-time validation of system control, on simulator and/or real system, is achieved with automatic code generation tools (Real-Time Workshop) and a platform dedicated to fast prototyping.

Most of the projects we have been brought to work on are confidential. However, we can do a brief overview of one of those projects to illustrate our involvement with more accuracy.

For several years, PSA has commercialised semi-automatic transmissions (SAT), which names are “Sensodrive”, “BPM6” and “ETG”. This technology offers automation functions (removal of the clutch pedal, automatic switching gear management) at lower cost than a traditional automatic transmission (AT). Moreover, SAT’s efficiency is better than AT. Unfortunately, SAT are often criticised for an uncomfortable driving experience due to the torque fracture related to the necessity of opening the clutch while gear shifting.

During the exploratory phase, we worked on control system creation for SAT to:

  • improve vehicle take-off (first seconds of driving after stopping), thanks to better synchronisation between the combustion engine and the automatic transmission, according to the clutch pedal position chosen by the driver.
  • embed creepingfunction and idle speed function, in order to obtain better maneuverability at slow speed.
  • improve transitional regime related to gear shifting: owing to their mechanical architecture, SAT needs a complete opening of the clutch while gear shifting, triggering a short but annoying deceleration. Our actions enhanced the synchronisation of events on the combustion engine and the automatic transmission during crucial periods.

The following article presents the latest SAT developed by PSA group, the ETG: http://automobile.challenges.fr/dossiers/20131016.LQA5237/etg-quand-la-boite-pilotee-peugeot-citroen-devient-frequentable.html (in French)

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These many projects helped Acsystème acquire substantial experience in the fields of:

  • actuator modelling and control (hydraulic and electric)
  • modelling the powertrain’s components: combustion engine, clutch, gearbox, drive shaft, …
  • designing powertrain control with different kinds of transmissions and powertrains (including hybrid solutions)
  • implementation and validation of a control system with simulator and prototype

Sébastien Saliou, November 2014

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