Papers by Kenneth Grattan
A number of studies on the use of optical fibre sensor techniques for structural monitoring are d... more A number of studies on the use of optical fibre sensor techniques for structural monitoring are discussed and results obtained, both in the laboratory and in the field, are reported.
IEEE Transactions on Industrial Electronics
Self-running piezoelectric robots have the advantages of being low cost, high load ratio and fast... more Self-running piezoelectric robots have the advantages of being low cost, high load ratio and fast speed of operation, as well as showing few limitations in confined spaces or for underwater applications. Controlling the speed of motion of such robots by adjusting the Standing Wave Ratio (SWR) along the vibration plate of the robot is important. Compared to the conventional dual-mode excitation method which is based on the adjustment of the excitation frequency, f, a novel SWR-based control method, using the adjustment of the temporal phase shift, θ, has been first derived by the authors. It has been found that the travelling wave component could be maximised using both methods, either by setting the value of f to the root mean square of the two adjacent modal frequencies, or by programming θ to have a sum of π when added to the spatial phase difference. It can be seen that using the 'θbased' traveling wave control method, smoother motion and higher resolution of the motion speed is achieved. In this research, by using the novel θ-based method to drive the robot, its motion characteristics, such as voltagespeed, load capacity and ability to move on different surface materials, have been tested through a series of experiments carried out and reported. Index Terms-self-running piezoelectric robot, dualmode excitation method, temporal phase shift, adjacent modal frequencies, Standing Wave Ratio (SWR) The authors acknowledge the support of the National Natural Science Foundation of China (52275014) and the support of the British Council through the 'Going Global Partnerships-Enabling Grants to Strengthen UK-China Institutional Partnerships through academic collaboration 2021' program. the ground"to do this on the ground with any material and to "dive in water" in a liquid medium. The piezoelectric self-running robot can be driven by Standing Waves (SWs) or Traveling Waves (TWs), according to the type of vibrational waves used [6]. Leg-shaped or toothshaped structures (in the SW-type robot) are often mounted on a vibrating plate, to convert the vertical vibration on the plate to the horizontal motion of the robot, when it is walking on a surface [7]-[10]. This kind of leg-shaped or tooth-shaped structure, which resembles the design of many ultrasonic motors [11]-[16], is not only difficult to fabricate, but the position, shape, size and material properties of the leg or tooth will also affect the performance of the robot [17], [18]. In addition, the use of such leg-shaped or tooth-shaped structures means that SW-driven robots are not easy to miniaturize, and this restricts their potential range of applications. By comparison, TW-driven robots have no such limitations because of their simple structureonly one or more pairs of ceramic piezoelectric patches are glued at both ends of a vibrating plate [19]-[21]. Moreover, the robots are able to move faster when driven using the TWs, but it is essential, however, to efficiently excite and control the traveling waves to allow TW-driven robots to be developed further. It has been reported that TWs can be generated using the Exciter-Absorber method or the Exciter-Exciter method [22]-[24]. The first of these, the Exciter-Absorber mode can be realized when a passive electric network is connected to one of the ceramic piezoelectric patches, glued to the vibrating plate, to absorb the energy. The circuit parameters required can be calculated using transmission line theory [25], [26]. However, this circuit not only produces heat, but also cannot be programmed to adjust both the TW component and its direction. An alternative method, the Exciter-Exciter mode can be used, allowing the direction and amplitude of the TWs to be adjusted by programming the excitation frequency between the two adjacent modal frequencies (this is known as Dual-Mode Excitation) [27]-[31], at a fixed phase shift value (θ=90°). In this way, the direction and speed of the TW-driven robot could
IEEE Sensors Journal
Thermocouple measurements Linear correlation model with temperature Modelling using FCM method Te... more Thermocouple measurements Linear correlation model with temperature Modelling using FCM method Temperature calibrated using the proposed method Temperature measurements using thermocouple Decompose nonlinear information using EMD
Optical Fiber Sensors for Marine Structural Condition Monitoring
Encyclopedia of Maritime and Offshore Engineering, 2017
On the Physical Origin of Strain Sensitivity in Optical Fibre Rare Earth Fluorescence Sensors
Sensors and their Applications XI, 2018
<title>An integrated probe design for measuring food quality in a microwave environment</title>
Third European Workshop on Optical Fibre Sensors, 2007
ABSTRACT The work presented describes the development of a novel integrated optical sensor system... more ABSTRACT The work presented describes the development of a novel integrated optical sensor system for the simultaneous and online measurement of the colour and temperature of food as it cooks in a large-scale microwave and hybrid oven systems. The integrated probe contains two different sensor concepts, one to monitor temperature and based on Fibre Bragg Grating (FBG) technology and a second for meat quality, based on reflection spectroscopy in the visible wavelength range. The combination of the two sensors into a single probe requires a careful configuration of the sensor approaches in the creation of an integrated probe design.
Sensors and Actuators B: Chemical, 2012
This paper presents a novel, pH-mediated protocol for the surface modification of gold nanorods (... more This paper presents a novel, pH-mediated protocol for the surface modification of gold nanorods (GNRs), which provides a robust platform for the assembly of localized surface plasmon resonance (LSPR)-based sensors, by facilitating functionalization at the surface of the nanoparticles. This is achieved by replacing the surface bilayer of cetyltrimethylammonium bromide (CTAB) with 11-mercaptoundecanoic acid (MUA) at alkaline pH after seed-mediated growth of GNRs. This method fully exploits the characteristics of MUA (i) the carboxylic acid functionality enables ligand exchange in an aqueous environment; (ii) the hydrophobic nature of the molecule stabilizes the nanorods and prevents aggregation via a selfassembled monolayer and (iii) the sulfur moiety binds to the gold surface. Critically, this procedure also simplifies subsequent functionalization, overcoming the limitation arising from commonly used CTABonly preparation. XPS (X-ray photoelectron spectroscopy) was used to confirm the ligand exchange at the surface of the GNRs. The surface modification facilitates the preparation of a LSPR-based biosensor based on human IgG for the detection of anti-human IgG and a detection limit of 0.4 nM was observed.
Nonlinear Optics '98. Materials, Fundamentals and Applications Topical Meeting (Cat. No.98CH36244)
Accurate modeling of second harmonic generation in optical waveguides
Physics and Simulation of Optoelectronic Devices VI, 1998
ABSTRACT An accurate numerical approach has been developed and is presented, based on the use of ... more ABSTRACT An accurate numerical approach has been developed and is presented, based on the use of finite element method (FEM) to study the nonlinear effect of Second Harmonic Generation (SHG) in optical waveguides. The evolution of the fundamental and second harmonic fields is followed by the implementation of a beam-propagation-type program using a split-step Crank Nicholson procedure based on the FEM. For the purpose of comparison, second harmonic generation using the Cherenkov radiation scheme in a planar waveguide is first considered and the results obtained in this research show very close agreement with those of earlier published work. Also presented are results obtained on frequency doubling for guided modes in planar waveguides using the quasi-phase matching scheme. Whilst planar waveguides allow for a comparatively easy analysis and modeling, practical waveguides are 2D devices with arbitrary diffusion profiles, and in this paper the work is extended to SHG in channel waveguides, with confinement in two transverse dimensions. Results are presented for both Cherenkov and quasi-phase matched devices. This method could prove to be very useful in the design and optimization of optical guided-wave devices and the present approach can be extended to the study of cascaded effects in nonlinear devices.
Design and performance evaluation of polyvinyl alcohol/polyimide coated optical fibre grating-based humidity sensors
The Review of scientific instruments, 2013
Optical fibre grating based sensors make a significant contribution to relative humidity measurem... more Optical fibre grating based sensors make a significant contribution to relative humidity measurement for various applications and a number of different designs and sensor configurations have been produced and discussed in the literature. Recent developments have included using sensitive polymers and indeed other materials that experience a variation of their physical and optical properties as a result of the absorption of moisture and which thus creates a modification of the characteristic spectral features of the gratings used. The strain and the effective refractive index of the gratings are affected by the change induced by the polymer and these effects were calibrated against the relative humidity variations that initially induce variations in the polymer layer. In this work, an evaluation is made of the performance characteristics of two different moisture sensitive polymers, i.e., polyimide and polyvinyl alcohol, as the basis of such sensors, while at the same time using diffe...
Silica optical fibre based temperature and strain sensors [A]
<title>Accurate modeling of second-order nonlinear effect in optical waveguides using the finite element method</title>
Design, Fabrication, and Characterization of Photonic Devices II, 2001
ABSTRACT The rigorous and efficient FEM based beam propagation method is used to model SHG in sem... more ABSTRACT The rigorous and efficient FEM based beam propagation method is used to model SHG in semiconductor waveguides. The effect of material loss on the overall efficiency of SHG is also analyzed. It is shown that under certain conditions, GaAlAs based devices with a lower non-linear susceptibility tensor could be more efficient than GaAs with a higher non-linear susceptibility tensor due to their low material loss. Numerical results are also presented, of the effect of domain fabrication error, in the case of quasi phase matched devices on the efficiency of SHG. The finite element method is also extended to the study of cascaded second harmonic generation in optical waveguides. The accuracy of the method is demonstrated by comparison with previously published results. The effect of the second harmonic on the fundamental in the presence of an intense input beam is discussed, through application to a practical waveguide structure.
Optical fibre sensor systems: new solutions for structural monitoring applications?
SPIE Proceedings, 2005
ABSTRACT Optical fibre sensor technology has advanced rapidly in recent years, with a feature of ... more ABSTRACT Optical fibre sensor technology has advanced rapidly in recent years, with a feature of current work a strong applications-focus which has become one of the major driving forces for innovation in the field. This paper focuses upon the nature of the background needs and the development of technologies well suited to tackling a range of problems in the assurance of the quality and stability of modern structures, and as a consequence the optimization and the minimization of the costs associated with maintenance of such structures. A number of topical sensor applications are considered and results of recent work presented.
Design issues for high-speed electro-optic modulators
SPIE Proceedings, 2003
ABSTRACT
<title>Effect of device parameters on the bandwidth calculations of ultrahigh-speed optical modulators</title>
Physics and Simulation of Optoelectronic Devices XI, 2003
The effect of velocity matching, impedance matching, conductor loss and dielectric loss on the op... more The effect of velocity matching, impedance matching, conductor loss and dielectric loss on the optical bandwidth of an ultra-high-speed lithium niobate (LN) modulator is reported by using the finite element method. It is shown that for an etched LN modulator the product VπL could be reduced by 30% and it is also relatively easier to match both Nm and Zc simultaneously. The work indicates that both the dielectric loss and impedance matching play a key role for velocity matched high-speed modulators along with the low conductor loss. The effects of etch depth, buffer thickness, electrode width and the gap between the electrodes on device performance are also illustrated.
Transverse force sensitivity of photonic crystal fibres
2012 IEEE Sensors, 2012
A tunable multiwavelength fiber laser source with an elliptical-core fiber Sagnac loop filter
SPIE Proceedings, 2005
A tunable multiwavelength fiber laser source with an elliptical-core fiber Sagnac loop filter. [P... more A tunable multiwavelength fiber laser source with an elliptical-core fiber Sagnac loop filter. [Proceedings of SPIE 5623, 910 (2005)]. Duan Liu, Nam Quoc Ngo, Xin Yong Dong, Kenneth TV Grattan, Tong Sun, Le Nguyen Binh, Swee Chuan Tjin, Song Yang Li. Abstract. ...
Sensors and Actuators B: Chemical, 2012
This paper discusses a systematic optimization process for the fabrication of better surface plas... more This paper discusses a systematic optimization process for the fabrication of better surface plasmon resonance (SPR)-based optical fibre sensors in order to enhance their performance when used for refractive index measurement. A set of key optimization parameters has been investigated, including the size of the gold-nanoparticles (AuNPs), the pH of the gold-nanoparticle solutions prior to the coating, the coating time of the gold-nanoparticles on the fibre substrate and the coating temperature used. A series of tests undertaken has confirmed that the increase of the gold nanoparticles size (within the limits of the experiment carried out) makes the device more sensitive. The variation of the pH of the gold solutions within the range investigated appears not significantly to affect the sensitivities of the devices created. Under the circumstances considered, the longer coating time results in a higher surface density which therefore allows a stronger SPR effect, creating a higher level of sensitivity of the device. In addition, the coating temperature has been investigated in this paper for 60 nm AuNP solutions and it has been concluded that the sensor fabricated at a temperature of 25 • C has demonstrated a better performance compared to others, evaluated when the surrounding refractive index of the sensors was varied over the range from 1.333 to 1.424.
Ranging measurements over a 20 metre path using an intensity-chirped laser diode
Measurement Science and Technology, 1994
An optical sensor has been developed and used to measure ranges of up to 20 m with an accuracy of... more An optical sensor has been developed and used to measure ranges of up to 20 m with an accuracy of a few centimetres. The frequency modulated continuous wave (FMCW) technique was employed in conjunction with an intensity modulated laser diode and optical fibres.
Journal of Physics: Conference Series, 2007
Fibre optic strain sensors offer a number of advantages over the current electrical resistance ty... more Fibre optic strain sensors offer a number of advantages over the current electrical resistance type gauges, yet are not widely used in civil engineering applications. The use of fibre optic strain sensors (with a cross comparison with the output of electrical resistance gauges) to monitor the production of corrosion by-products in civil engineering concrete structures containing reinforcement bars has been investigated and results reported.
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Papers by Kenneth Grattan