Vanja Ranogajec

Bond Graph Analysis of Automatic Transmission Shifts including Potential of Extra Clutch Control

New generation of torque converter automatic transmissions (AT) include a large number of gears for improved fuel economy. Control requirements for such transmissions become more demanding, which calls for the development of new shift optimization and analysis tools. This paper presents two contributions to the field of transmission dynamics analysis: (i) bond graph method-based shift transient analysis, and (ii) deriving a unique set of conditions for beneficial use of a third (normally-open) clutch for any upshift or downshift, with emphasis on inertia phase. The derived conditions are examined on an example of 10- speed AT based on the clutch torque input trajectory optimization results. The examination results point out that the extra clutch has a potential of significant performance improvement for any single- transition upshift in the inertia phase, in terms of reduced vehicle jerk RMS value due to the suppressed inertia bump effect. The shift quality improvement is possible in the torque phase, as well, but it is of much smaller extent when compared to that related to the inertia phase.

On smoothing HEV/EREV supervisory control action using an extended ECMS approach

The paper first describes the previously proposed control strategy for a series-parallel hybrid electric vehicle (HEV) and an Extended Range Electric Vehicle (EREV), which combines a heuristic RB controller with an instantaneous optimisation strategy. The optimisation algorithm is based on the equivalent consumption minimisation strategy (ECMS), which optimises the engine operating point over proper 1D or 2D regions of the engine torque map at every sampling instant. In order to try to minimise the equivalent fuel consumption, the ECMS approach can command frequent changes of engine operating points, thus affecting NVH features of the HEV/EREV power train. The paper proposes and verifies an extended ECMS approach that penalizes for frequent changes of engine operating point, thus being able of reducing the NVH content and in fact improving the fuel economy when applied to a full (forward-looking) power train model.