Patent ID: 8689539

Claim:
A counter-rotating open-rotor gas turbine engine comprising: a forward un-ducted rotor including a plurality of forward rotor blades and including a forward rotor angle actuator for setting blade pitch angles of the plurality of forward rotor blades; an aft un-ducted rotor including a plurality of aft rotor blades and including an aft rotor angle actuator for setting blade pitch angles of the plurality of aft rotor blades; a gas turbine engine driving forward and aft un-ducted rotors and including a fuel actuator for setting the fuel flow to the gas turbine engine; and an open rotor control system including, a forward rotor blade pitch angle command (BetaF) electrically connected to the forward rotor angle actuator, an aft rotor blade pitch angle command (BetaA) electrically connected to the aft rotor angle actuator, a fuel flow command (Wf) electrically connected to the fuel actuator, a forward rotor speed feedback signal (Nf), an aft rotor speed feedback signal (Na), and at least two of the engine pressure measurement feedback signals for calculating the engine pressure ratio (EPR) and an engine core speed signal (N 2 ); the open rotor control system including a control algorithm including, a 2×2 multi-input-multi-output (MIMO) control solution for the forward rotor blade pitch angle command (BetaF), the aft rotor blade pitch angle command (BetaA), the forward rotor speed feedback signal (Nf) and the aft rotor speed feedback signal (Na); and a single-input-single-output (SISO) control solution for the fuel flow command (Wf) and the at least two of the engine pressure measurement feedback signals for calculating the engine pressure ratio (EPR) and the engine core speed signal (N 2 ).