Structural synthesis method

The synthesis is based on Multibody Systems Method (MBS) according to which a mechanical system is defined as a collection of bodies with large translational and rotational motions, linked by simple or composite joints [5]. The functional design process at structural level consists in the following stages:

♦ Identification of all possible graphs on basis of the following input data:

— spatiality of the multibody system;

— type of the geometrical constraints gc (simple or/and compound);

— number of bodies nb;

— the mobility of the multibody system M.

♦ Selection, from multitude of the identified graphs, of the graphs that are admitting supplementary conditions imposed by the specific field of utilisation.

♦ Successive transformation of the selected graphs into mechanisms by:

— mentioning the fixed body and the role of the other bodies (ex.1-fixed body, 2-input body, 3-output body etc.);

— identification of distinct graphs versions based on the preceding particularisation;

— transformation of these graphs versions into mechanisms by mentioning the types of constraints gc (rotation, translation etc.) [2], [7].

The graphs of the multibody system are defined as a features based on the modules introduced in the next figure and are considering the number of bodies and the relationships between them.

The identification of all possible graphs starts with definition of the types of the geometrical restrictions between the bodies considering the chosen space S (gc, min= 1, gc, max = S-1) [9]. In the Fig.4 the notations “R” and “T” represent restriction rotation type and respective translation restriction type. All the other notations represent composite joints as combinations of the ones mentioned before.

Fig.4 Restriction types

For example, in the planar space (S = 3), all the possible graphs can be designed using the restrictions types from Fig.4, where gc= 1 (Fig.4.a), gc = 1+1 (Fig.4.b), gc = 2 (Fig.4.c), considering the correlations between the number of bodies nb, the mobility M and the sum of the geometrical constraints Igc.

The relation between M, S, nb, Zgc is [8.]:

M=S(nb-1)-Zgc (1)

In respect with the relative motions of the sun on the sky dome the mobility of the mechanisms that orients the receiver of the conversion system deals with a degree of freedom equal with 2.