Patent ID: 7601092

Claim:
A vehicle propulsion system, comprising: an internal combustion engine having an engine output; an electro-mechanical transmission including a transmission input and a transmission output, said transmission input operatively coupled to said engine output, at least one planetary gear set operatively coupling the transmission input to the transmission output at a speed ratio, at least one rotatable electric machine operatively coupled to said at least one planetary gear set, and at least one torque transfer device applied and released to selectively establish one of (a) an electrically variable operating mode wherein the speed ratio is a function of the at least one rotatable electric machine's speed and (b) a fixed operating mode wherein the speed ratio is fixed; and a control system operable to monitor operator inputs and operating conditions of the engine and the transmission, determine permissible ones of the electrically variable and fixed operating modes and respective optimum operating costs, control operation of said engine, said at least one rotatable electrical machine, and said at least one torque transfer device to effect the one of said permissible ones of the electrically variable and fixed operating modes having a preferred optimum operating cost.