Object Oriented Trim of Complex High-Fidelity Simulation Models

The paper describes the development and implementation of a MATLAB based object oriented computational tool that allows numerical t rimming of complex high fidelity simulation models implemented in SIMULINK. Equilibrium points for the simulation model are determined numerically by a nonlinear equation solver. The nonlinear trim equations to be solved are defined by so called trim templates, which are built around the simulation model, enforcing the desired flight condition by su perimposing numerical constraints to the model. Trim templates are implemented as objects on various levels that can be accessed by several methods. To trim complex simulation models with rigid body dynamics and a variable number of different subsystems, child trim template objects are specified that inherit from the parent trim template class. They a ddress rigid body dynamics and different subsystems and are combined in the model trim template assembling the trim condition for the complete simulation model. Objects of the class model trim template handle the correlation between the different subsystems and co ntrol possible trim procedures like integrated or nested trim. The object oriented impl ementation and the trim algorithm are applied to a complex simulation model featuring a high system order as many subsystem states (e.g. those of the propulsion system, actuat ors or sensors) augment the original rigid body states. The aircraft rigid body trim template allows to specify different flight maneuvers, e.g. steady-state straight horizontal fl ight, climbing and turning flight with the implementation of several constraints or more complex cases like steady heading sideslips as well as failure cases or quasi-steady maneuvers, e. g. the determination of the maximum achievable steady-state roll rate or acceleration.