Optimization of aircraft units mounting by using a database of their virtual computer models

Аuthors

Chotchayeva S. K.^1*, Shevtsov S. N.^2**, Flek M. B.^3***

1. Rostvertol Helicopters, 5, Novatorov st., Rostov-on-Don, 344038, Russia
2. Southern Scientific Center of the Russian Academy of Sciences, 41, Chekhov str., Rostov-on-Don, 344006, Russia
3. Don State Technical University, DSTU, 1, Gagarin square, Rostov-on-Don, 344003, Russia

*e-mail: semo_s@mail.ru
**e-mail: sergnshevtsov@gmail.com
***e-mail: michflek@gmail.com

Abstract

The paper proposes a method for ensuring the required accuracy during the aircraft units mounting. The method was developed for the cases when the dimensional coupling structure of the assembly is represented by multi-link coupled three-dimensional chains. In such cases the assembly accuracy is attained via the adjustment method. Any change of one of the varied dimensions (of the so-called «variable compensators») during the attainment of the accuracy of assembly of such systems leads to the changes of all resulting parameters of the assembly precision. This is due to the fact that such dimensional chains are coupled. The output dimensional parameters are usually measured indirectly due to the difficulties of direct measurement of the relative spatial positions of the large-sized and heavy units. The adjustment process for such systems is implemented according to the trial-and-error method. The sizes of each variable compensator are consecutively changed and all output accuracy parameters are measured at each step of this process. The spatial positions of the adjusted points and output dimensions control points are separated by a relatively long distance. Therefore the adjustment requires the joint work of the assembly crew. This in turn leads to a considerable increase of the manufacturing cost and duration of the mounting and assembly.

The presented method implies the development of mathematical (numerical-analytical vectorized) model of the mounted units. This model describes the whole geometrical structure and all dimensions of the assembly. The numerically stable algorithms, which allow the operator to solve both direct and inverse problems, are constructed for this model. The database with the virtual assemblies is created by using these algorithms. Random values are assigned to all internal dimensions of each assembly in the database. These values are distributed according to a certain law within the given tolerance ranges. Each record of this database contains information about the changes in the variable compensators, which are required to attain the required output dimensional precision of the assembly. During an actual assembly this information is taken from a similar virtual assembly and used to tune the output assembly precision.

The proposed method is illustrated on the example of engine mounting technology for a single-rotor helicopter with two engines. The paper concludes with a discussion of the advantages and problems of implementation of the technology, which is based on the offered approach, in small- and medium-scale production of aircraft and rotorcraft.

Keywords:

assembly technology, dimensional analysis, process performance, model of coupled dimensional chains, controlled object, computer modeling, database

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