Patent Document ID: 20090012762
Application ID: 12078711
Patent Flag: 0

Claim One:
1. A method of constructing a piecewise linear engine performance model, comprising the steps of: (a) providing a non-linear engine performance model which iteratively calculates engine performance variables y from a plurality of sub-models, each sub-model representing the performance of a component of the engine; (b) defining a plurality of engine power conditions, each engine power condition being defined by one or more engine state variables x; (c) for each of the engine power conditions, using the non-linear engine performance model to determine partial derivatives δy of the engine performance variables y with respect to engine control variables u and with respect to the engine state variables x, the values of the partial derivatives δy being determined so that, on integrating the partial derivatives δy, the error between steady state values for the engine performance variables y calculated by the non-linear engine performance model and steady state values for the engine performance variables y calculated from the integrated partial derivatives δy is reduced or eliminated; and (d) constructing a piecewise linearised engine performance model in which calculation of the engine performance variables y involves combining each of the engine control variables u and the engine state variables x with the respective partial derivative δy.