Patent ID: 8688245

Claim:
A method of controlling a gas turbine engine, the method comprising the steps of: (a) providing a model M of the gas turbine engine which is in explicit form and which predicts one or more gas turbine engine performance variables y from one or more gas turbine engine control variables u, such that y(k+1|k)=M u(k+1|k), where k is the present time, and k+1 is the time in the future after the passage of a time increment of predetermined length; (b) at time k, measuring or estimating the present values of the performance variables y, and then using a deterministic algorithm to optimise a cost function: J = âˆ‘ i = 1 N â¢ F â¡ ( u â¡ ( k + i | k ) , y â¡ ( k + i | k ) ) , where: N is selected such that the cost function J is convergent, k+i is the time in the future after the passage of i of the time increments, u(k+i|k) and y(k+i|k) are restricted in the cost function J to values of the respective control variables u and performance variables y which are compatible with predetermined gas turbine engine operational constraints, and for each time increment i=1 . . . N, values for F(u(k+i|k),y(k+i|k)) are calculated using the gas turbine engine model M to determine y(k+i|k) for a plurality of respective discrete values of u(k+i|k), the discrete values being limited to and representatively sampling the range of possible values of u which are compatible with the predetermined gas turbine engine operational constraints, the cost function J being optimised by identifying the combination {u(k+1|k),u(k+2|k), . . . u(k+N|k)} of respective discrete values u(k+i|k) over the N time increments which combination yields an optimised value for J; (c) selecting values for the control variables u which correspond to u(k+1|k) in the identified combination {u(k+1|k),u(k+2|k), . . . u(k+N|k)}; (d) at time k+1, controlling the gas turbine engine with the selected values for the control variables u; and (e) repeatedly performing steps (b) to (d), time k+1 becoming the new time k after each performance of step (d).