Systems and methods for controlling engine speed in a hybrid vehicle

Abstract

Methods and systems are provided for controlling an engine speed in a hybrid vehicle system during steady-state conditions and in response to transient acceleration and/or deceleration requests. In one example, an engine speed is controlled to an optimal engine speed for fuel economy during steady-state conditions, and in response to an acceleration or deceleration request, a target engine speed is obtained from a rate-limited optimal engine speed to vehicle speed ratio, and the engine is controlled to the target engine speed provided the target speed is below a threshold difference from optimal engine speed. In this way, the vehicle system may simulate a fixed ratio transmission during accelerations and decelerations, while maintaining optimal engine speed for fuel economy at steady state.

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