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Continuous Scanning Laser Doppler Vibrometry (CSLDV) methods first appeared in the literature in the early 1990s and over the past three decades they have undergone an evolution in terms of procedures and applications which constitute a new state-of-the-art now described in this review paper. The advances in vibration measurement performed by Scanning Laser Doppler Vibrometers augmented the capability of measuring vibration data from a grid of a few hundred measurement points to a single scan which traverses and measures at many thousands of points on the same structure. The deflection shapes of vibration modes can be created by assembling two pieces of information from a scanning measurement - temporal and spatial - and the more measurement ‘points’, the better the spatial density and resolution of the deflection shape(s). The introduction of Continuous Scanning techniques challenged the traditional principle that the number of measurement points defines the spatial definition of the deflection shape. Thereafter, high definition deflection shapes could be achieved by measuring a single time series from a continuously sweeping trajectory covering the same surface area that would traditionally be covered by a set of fixed-point measurements, each of which spans a range of frequencies. The CSLDV approach compresses both the temporal oscillation and the spatial distribution of the deflection shape into one LDV output-modulated signal, whereby the harmonic oscillation and the spatial distribution across a swept area were now defined by a central response harmonic and its sidebands. This change of perspective in vibration measurements from the conventional stepped-scan method to the continuous-scan approach allowed several researchers to exploit and expand the potential of the scanning vibrometer further than its initial design specifications. This paper starts with the raison d’etre, with a brief historical account of how vibration measurements have developed over the past decades, and then moves to the theoretical background and applications of the CSLDV approach. Finally, the paper presents a philosophical and technical account of the research work carried out by several colleagues over the past thirty years and aims to provide a chronological order to the various advancements that CSLDV techniques offer in engineering structural dynamics.

This study measured spatio temporal parameters (STP) and their symmetry index (SI) in order to evaluate the differential effect on the gait pattern of individuals with unilateral transtibial amputations when using two different prostheses. Twelve individuals with transtibial amputations walked on level ground using an Energy Storage and Return (ESAR) prosthesis with fixed ankle and a prosthetic foot with adaptive ankle (PFAA). The STP were measured in the prosthetic and sound limbs and the symmetry index for each parameter was calculated afterwards. The results showed no statistically significant differences between the prostheses for the STP measured, and this was the case both for the prosthetic and sound limbs. Similarly, the SI did not reflect statistically significant differences when the different prostheses were used. Thus, the results suggest that the STP studied and their SI may not reflect differences when evaluating ESAR versus PFAA prostheses in the conditions proposed in this study.

Slope ambulation is a challenge for trans-femoral amputees due to a relative lack of knee function. The assessment of prosthetic ankles on slopes is required for supporting the design, optimisation, and selection of prostheses. This study assessed two hydraulic ankle-foot devices (one of the hydraulic ankles is controlled by a micro-processor that allows real-time adjustment in ankle resistance and range of motion) used by trans-femoral amputees in ascending and descending a 5-degree slope walking, against a rigid ankle-foot device. Five experienced and active unilateral trans-femoral amputees performed ascending and descending slope tests with their usual prosthetic knee and socket fitted with a rigid ankle-foot, a hydraulic ankle-foot without a micro-processor, and a hydraulic ankle-foot with a micro-processor optimised for ascending and descending slopes. Peak values in hip, knee and ankle joint angles and moments were collected and the normalcy Trend Symmetry Index of the prosthetic ankle moments (as an indication of bio-mimicry) were calculated and assessment. Particular benefits of the hydraulic ankle-foot devices were better bio-mimicry of ankle resistance moment, greater range of motion, and improved passive prosthetic knee stability according to the greater mid-stance external knee extensor moment (especially in descending slope) compared to the rigid design. The micro-processor controlled device demonstrated optimised ankle angle and moment patterns for ascending and descending slope respectively, and was found to potentially further improve the ankle moment bio-minicry and prosthetic knee stability compared to the hydraulic device without a micro-processor. However the difference between the micro-processor controlled device and the one without a micro-processor does not reach a statistically significant level.

Improved walking comfort has been linked with better bio-mimicking of the prosthetic ankle. This study investigated if a hydraulic ankle/foot can provide enough motion in both the sagittal and frontal planes during level and camber walking and if the hydraulic ankle/foot better mimics the biological ankle moment pattern compared with a fixed ankle/foot device. Five active male unilateral trans-femoral amputees performed level ground walking at normal and fast speeds and 2.5E camber walking in both directions using their own prostheses fitted with an aEchelono hydraulic ankle/foot and an aEsprito fixed ankle/foot. Ankle angles and the Trend Symmetry Index of the ankle moments were compared between prostheses and walking conditions. Significant differences between prostheses were found in the stance plantarflexion and dorsiflexion peaks with a greater range of motion being reached with the Echelon foot. The Echelon foot also showed significantly improved bio-mimicry of the ankle resistance moment in all walking conditions, either compared with the intact side of the same subject or with the anormalo mean curve from non-amputees. During camber walking, both types of ankle/foot devices showed similar changes in the frontal plane ankle angles. Results from a questionnaire showed the subjects were more satisfied with Echelon foot.

Gyroscopes have been proposed as sensors for ambulatory gait analysis and functional electrical stimulation systems. These applications often require detection of the initial contact (IC) of the foot with the floor and/or final contact or foot off (FO) from the floor during outdoor walking. Previous investigations have reported the use of a single gyroscope placed on the shank for detection of IC and FO on level ground and incline walking. This paper describes the evaluation of a gyroscope placed on the shank for determination of IC and FO in subjects ascending and descending a set of stairs. Performance was compared with a reference pressure measurement system. The absolute mean difference between the gyroscope and the reference was less than 45 ms for IC and better than 135 ms for FO for both activities. Detection success was over 93%. These results provide preliminary evidence supporting the use of a gyroscope for gait event detection when walking up and down stairs. Fil: Catalfamo Formento, Paola Andrea Lucia. Universidad Nacional de Entre Ríos. Facultad de Ingeniería; Argentina. University of Surrey; Reino Unido. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Acevedo, Rubén Carlos. Universidad Nacional de Entre Ríos. Facultad de Ingeniería; Argentina Fil: Ghoussayni, Salim. University of Surrey; Reino Unido Fil: Ewins, David. University of Surrey; Reino Unido

If a laser Doppler vibrometer is used in a continuously-scanning mode to measure the response of a vibrating structure, its output spectrum contains side-bands from which the response mode shape, as defined along the scan line, may be obtained. With impact excitation, the response is the summation of a set of exponentially-decaying sinusoids which, in the frequency domain, has peaks at the natural frequencies and at `sideband' pseudo-natural frequencies, spaced at multiples of the scan frequency. Techniques are described for deriving natural mode shapes from these, using standard modal analysis procedures. Some limitations as to the types of mode which can be analysed are described. The process is simple and speedy, even when compared with a normal point-by-point impact test survey. Information may also be derived, using a circular scan, on the direction of vibration, and angular vibration, at individual points.

The Surrey Virtual Rehabilitation System (SVRS) was developed for clinical use in physiotherapy for children with cerebral palsy (CP). The overall aim of this work was to evaluate the practicality of the SVRS for three simple lower extremity exercises. Two children with CP, two clinical engineering trainees and a physiotherapist performed the tests whilst parents and a paediatric physiotherapist observed the exercise sessions. The feedback collected during an open-discussion and the descriptive analysis of responses to 15 closed-ended questions suggest that the participants were satisfied with the practicality of the SVRS. Outcome measures derived from data collected during the sessions indicate that the SVRS may provide clinically relevant feedback on the performance of patients for themselves and their treating clinicians. In conclusion, the SVRS appears practical for rehabilitation purposes and is worthy of further evaluation and development. Copyright © 2014 Inderscience Enterprises Ltd.

Underplatform friction dampers are commonly used to control the vibration level of turbine blades in order to prevent high-cycle fatigue failures. Experimental validation of highly non-linear response predictions obtained from FEM bladed disk models incorporating underplatform dampers models has proved to be very difficult so as the assessment of the performance of a chosen design. In this paper, the effect of wedge-shaped underplatform dampers on the dynamics of a simple bladed disk under rotating conditions is measured and the effect of the excitation level on the UPDs performances is investigated at different number of the engine order excitation nearby resonance frequencies of the 1st blade bending modes of the system. The measurements are performed with an improved configuration of a rotating test rig, designed with a non-contact magnetic excitation and a non-contact rotating SLDV measurement system.

Gyroscopes have been proposed as sensors for ambulatory gait analysis and functional electrical stimulation systems. Accurate determination of the Initial Contact of the foot with the floor (IC) and the final contact or Foot Off (FO) on different terrains is important. This paper describes the evaluation of a gyroscope placed on the shank for determination of IC and FO in subjects walking outdoors on level ground, and up and down an incline. Performance was compared with a reference pressure measurement system. The mean difference between the gyroscope and the reference was less than –25 ms for IC and less than 75 ms for FO for all terrains. Detection success was over 98%. These results provide preliminary evidence supporting the use of the gyroscope for gait event detection on inclines as well as level walking.

International audience; There are a variety of abnormal running conditions in rotating machinery which lead to rotor/stator interaction dynamics which, in turn, can cause a rich mixture of effects associated with rub-related phenomena. These effects manifest themselves in the occurrence of multiple solutions for steady-state vibration response scenarios , including amplitude jumps during rotor acceleration, and vibration responses at different/multiple frequencies of excitation forces such as imbalance. This paper describes a numerical algorithm based on the harmonic balance method to calculate the periodic response of a non-linear system under periodic excitation. The algorithm also calculates the stability of the periodic solutions found, marks turning and bifurcation points, and follows a solution branch over varying system parameters via arc-length continuation.