3422. Weight Prediction of UAV Structures and Subsystems Using Parametric Design Methods

Paper

Abstract

For larger UAVs with more than 500 kg MTOM, technologies and assembly methods similar to man-carrying systems are used. These allow the use of known preliminary design methods according to Raymer, Roskam, or Stinton. In the case of smaller vehicles, the use of empiric equations made for man-carrying systems, most of the time, cause significant errors due to unscale-effects. Among other effects, this is based on a smaller decrease in size of connecting elements when decreasing overall part dimensions. Bonds of ribs with the outer skin can make up to 50% of the mass at small sizes. At reduced dimensions, breakouts for mass reduction cannot be made, which causes an unproportional mass increase of small parts. Since these problems appear in a similar way in nearly all parts of a UAV structure, a calculation using equations based on statistics for larger structures is no longer applicable. In order to accomplish a reasonable preliminary design of small UAV systems, the possibility of a preliminary design method by using a complete parameterization will be presented. Parameterization, in this case, means the computation and respective sizing of all system components with some key values and a number of model-changing parameters. Numerous structural elements as well as a large number of subsystems (e.g., starter and alternator-systems, reduction gear, retractable undercarriage, recovery system, etc.) were built as parametric models. The level of detail is set to a very high value, in fact down to the smallest shim, in order to take into account all unscale effects. These complex models were analyzed by a systematic variation of different parameters to get simplified mass-estimation equations which are now available for the mass prediction of small UAVs, including the effect of integrating different subsystems.