<title>Smart structures: the role of fiber optics</title>

Abstract

The concept of the smart structure integrates structural engineering, sensing, control systems and actuation to provide a mechanical assembly which is capable of responding to its environment and/or loading conditions. The realisation of the smart structure requires integration of skills in a variety of scientific and engineering disciplines ranging from mechanical engineering through materials science into signal processing, data analysis, sensing and actuation.The sensing technology must have a number of key features of which the ability to take distributed measurements of various parameters throughout the structure is paramount. Fibre optics technology therefore promises to have a significant role to play in the evolution of the smart structures concept. This paper analyses this role in detail, presents an assessment of the current state-of-the art in fibre optic technology related to smart structures and presents a scenario for future developments. INrRODUCTIONThe smart structure integrates mechanical engineering, control systems, signal processing and actuation in a way which can be visualised with reference to Figure 1 . The essential concepts are that the actuators and sensors are embedded within the actual structure and therefore form an integral part of its behavioural characteristics. The smart structure may then respond by adapting its dimensions, its stiffness, its vibrational characteristics, its damping constant, etc, in response to environmental and/or loading conditions. The realisation of a truly smart or adaptive structure requires advanced technology in sensing, processing, control and actuation and to date they have only been brought together at a relatively simplistic level for specialised applications such as space vehicles 1.The first step in the realisation of the generalised smart structure is the incorporation of the necessary sensor arrays to obtain the essential data concerning the state of the structure. In general this requires precision distributed measurements of the strain, temperature and sometimes chemical composition throughout the structure. Careful analysis of loading requirements and the structural characteristics can limit the number of sensory elements required, but in general, a complex sensing array is essential. This paper focuses on the needs in this sensor array and discusses these needs with reference to the properties of fibre optics systems, thereby demonstrating that fibre optics will have an important but not exclusive role to play in the evolution of smart structures.Potential applications for smart structures may be viewed either by the industrial sector under consideration or through the properties of the materials from which a particular structure is fabricated. There are potential applications in aerospace (especially for zero gravity structures), civil engineering, marine engineering, automotive engineering, and in the longer term, when the technology costs are pruned, in consumer products such as toys, leisure goods and domestic appliances. A discussion ba...

<title>Stabilization in an optical fiber interferometer using a semiconductor laser</title>

“…4=2itnL/X (1) While the compensation schemes using piezoelectric actuators can modify L, when an imbalance (the path difference LD 0) is introduced between the arms of a two beam interferometer, if the wavelength of the light is increased, then differential optical phase between the arms also have a proportional variation as it is expressed in equation (2), where X and &c are the wavelength and wavelength changes 6 Thus optical phase changes can be produced by tuning the wavelength of the source in order to compensate those phase displacements due to environmental fluctuations.…”

Hypersonic Aerodynamic Force Balance Using Micromachined All-Fiber Fabry–Pérot Interferometric Strain Gauges

“…Petuchowski et al [3] discussed the implementation of a FFPI device with fiber ends to serve as mirrors. On account of the advantages, such as capability of responding to a wide variety of parameters, high resolution, and miniature size, FFPI sensors were demonstrated to be especially attractive for the measurement of numerous physical and chemical parameters in past years [4,5,6,7,8].…”

Measurement of rotation axis transverse displacements based on diffuse reflective intensity modulated optical fiber sensor

“…3,4 These advantages have promoted worldwide research in intensity-modulated optical fiber sensors, especially in the modulation system. 5 Intensity-modulated FOSs for various applications have been demonstrated based on various modulation systems including offset coupling, 6,7 reflector translation and angular displacement, 8,9 reflectivity, 10 transmissivity, 11 refractive index, 12,13 varying, and microbending. 14 But for the measurement of rotation axis, it is difficult to establish a modulation between the rotation axis transverse displacements ͑RATD͒ and the optical intensity with the preceding modulation systems.…”