Multibody Model-Based Multi-Objective Parameter Optimization Of Aircraft Landing Gears

Abstract

Landing gears of commercial passenger transport aircraft play an increasingly important role for safety, comfort and for weight considerations. As a result and in particular for future large aircraft with take-off weights up to 600 metric tons, the contribution of the landing gears to the structural weight would become prohibitive if standard designs would simply be extrapolated.

Thus research has been performed to investigate new concepts for advanced landing gears and optimize their associated design parameters to achieve minimum weight, maximum comfort under strict requirements with respect to safety and even increase lifetime by reducing the loads during landing impact and taxiing. A detailed and verified mechanical model is derived for an existing aircraft (Airbus A300); because this model will be used for simulating the standard design as well as the active optimized landing gear it needs rather careful and detailed modelling, e.g. it requires fuselage and wing flexibility to be taken into account.

The simulation was performed within SIMPACK, DLR’s prime multibody computer code [1]. SIMPACK has the major features to allow for arbitrary complex elastic mechanical systems including active components. Using the complete SIMPACK model the concept for a semi-active actuator is considered and realistic model assumptions for its dynamic behavior are made. Even though SIMPACK allows for the portation of the full nonlinear multibody simulation (MBS) model into any of the common design packages like ANDECS, MATRIX_x or MATLAB it is very useful to reduce the model complexity to the necessary effects because of the further, computationally very involved design procedures. Order reduction is performed through physical and engineering reasoning and formal mathematical procedures, both supported by SIMPACK modules.

Results will be presented on using the multi-objective parameter optimization software MOPS (Multi-Objective Programming System) implemented in ANDECS [2]. The design case study concentrates on taxiing of a flexible aircraft where reduction of the so-called “beaming effect” (e.g. dynamic coupling of runway excitation with elastic fuselage eigenmodes) is the major design goal. Comparisons are made showing the achieved improvements.