Patent ID: 8296027

Claim:
Method for controlling an electro-mechanical transmission through an unlocking state of a clutch, the transmission mechanically-operatively coupled to an internal combustion engine and an electric machine adapted to selectively transmit mechanical power to an output member, said method comprising: decreasing a reactive torque acting upon said clutch, said decreasing said reactive torque comprising overriding torque commands to said engine, and overriding torque commands to said electric machine; and simultaneously decreasing a clutch torque capacity, comprising in a lead period selected according to an engine command reaction time, commanding an intermediate clutch torque command maintaining sufficient clutch torque capacity to exceed an initial reactive torque calculated at an initiation of said unlocking state, and in a second period following said lead period, progressively decreasing through a ramp down said clutch torque capacity, said decreasing said clutch torque capacity maintaining sufficient clutch torque capacity to exceed said decreasing reactive torque.