Design and experimental testing of an adaptive shape-morphing tensegrity structure, with frequency self-tuning capabilities, using shape-memory alloys

Abstract

Abstract. The present paper explores the capabilities of a tensegrity-inspired tower with regard to frequency tuning by shape morphing. To change the configuration of the proposed structure, shape-memory-alloy actuators are used. This actuation principle also takes advantage of the variation of the elastic modulus of shape-memory alloys associated with the martensitic transformation. The temperature modulation of the shape-memory-alloy wires is successfully achieved by Joule heating, through a proportional-integral-derivative controller, to change between a low-temperature shape and a high-temperature shape. The implementation of a short-time-Fourier-transform control algorithm allows for the correct identification of the dominant input frequency, associated with the dynamic excitation. This information is used to automatically change the configuration of the structure in order to shift its natural frequency away from that of the dynamic excitation. With this frequency tuning, one obtains a reduction of the accelerations throughout the structure up to about 80%. The good performance of the proposed control approach gives promising indications regarding the use of tensegrity systems, in combination with shape-memory alloys, for shapemorphing applications, and, in particular, for self-tuning structures.

Synthesis of minimum energy adaptive structures

“…Applications of this concept have been suggested for space cranes, scaffolding and large structural rings for antennas (Miura and Furuya 1988;Campanile 2003;Subramaniam and Kramer 1992). Active tensegrity structures, structures whose stability depends on self-stress, have been used for deployable systems (Tibert 2002) as well as for control of displacements (Fest et al 2003;Veuve and Smith 2015) and of the structure fundamental frequency (Santos and Micheletti 2015;Bel Hadj Ali and Smith 2010). Active compliant structures, which can be thought of as structures working as monolithic mechanisms (Hasse and Campanile 2009) have been investigated for shape control of antenna reflectors (Jenkins 2005), for shape morphing of aircraft wings to improve on manoeuvrability (Previtali and Ermanni 2012;Kota et al 2003) as well as for the control of direct daylight in buildings (Lienhard et al 2011).…”

Adaptive glass panels using shape-memory alloys

“…the SMA wires, through temperature modulation by Joule effect. SMAs are a new generation of silent actuators, with no moving parts, in which the activation is derived from the material itself due to the so-called 'shape-memory effect' (SME), see for example (Cismasiu and Santos 2008;Santos et al 2015). The SME allows the material to recover its original shape through a thermal cycle, after withstanding large deformations.…”

Vibration health monitoring for tensegrity structures

“…Some real measurements of vibrations of tensegrity structures have been done and results published [21,22]. These, however, do not exclusively discuss the possibilities with pre-measurement analysis, which might reduce the variations between real and numerical results if the pre-simulations are accurate enough.…”