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6 pages; International audience; Wires and cables are valuable components for the design of mechanical structures, due to their high strength-to-lightness ratio. Their efficiency is only guaranteed when they are subjected to tensile stress: indeed, they exhibit a unilateral behaviour with a lack of stiffness in compression. The tensile state depends on the distribution of stress through the whole structure. The computation of this stress state requires to deal with nonsmooth relations arising from the modelling of the unilateral behaviours, leading to specific numerical strategies. Two examples of such structures are investigated. Tensegrity structures are light reticulated systems composed of bars in compression and a large number of tensioned cables. As poetically defined by Fuller [1], they are viewed as “islands of compression in an ocean of tension.” TexSol is a reinforced geomaterial made of sand and wires. This type of material is adapted for the embankments requiring a strong slope or works which may be subjected to a dilatation strain. In this case, the nonsmoothness is not reduced to the wire behaviour but concerns as well the frictional contact between grains and between grains and wires.

This paper describes the application of identification techniques in the design and optimization of a vertical navigation (VNAV) autopilot for a light sport aviation (LSA) high performance aircraft(Flight Design CT 2K). The whole design has been based, to reduce global costs, weight and complexity, on the control of the stabilator trim instead than, as is more common, on the direct control of the stabilator by means of a dedicated servo actuator. This solution, despite the abovementioned advantages, is characterized by some critical aspects due to the introduction of additional delays in the control chain and also to potential safety problems thatmust be carefully considered. The first design step has seen the construction of an accurate model concerning the aircraft response to the stabilator trim. This model has been obtained by means of identification techniques applied to data sequences collected in specific flights and has been validated by means of simulations performed on data sets concerning different flights. The model has then been used to design and optimize a PID controller whose performance has been tested first in simulation contexts and subsequently, after its implementation into the autopilot, in flight conditions. This design approach has allowed, on the one hand, a sensible reduction of inflight tests and of trial and error procedures and, on the other hand, to obtain a good final autopilot behavior confirmed by all inflight validation tests.