New Publications are available for Velocity, acceleration and rotation measurement
http://dl-live.theiet.org
New Publications are available now online for this publication.
Please follow the links to view the publication.Applications of waist segment kinematic measurement using accelerometry for an autonomous fall-detection system during continuous activities
http://dl-live.theiet.org/content/conferences/10.1049/cp.2010.0512
Through the measurement and thresholding of different kinematic and angular signals, from the waist using accelerometry, distinguishing between simulated falls and normal scripted and continuous, unscripted activates was performed and evaluated using these signals. Different combinations of individual signal thresholding algorithms were used to compile a suite of Fall-detection algorithms suitable for an autonomous waist worn system. The suite of algorithms were tested against a comprehensive data-set recorded from 10 young healthy subjects performing 240 falls and 120 activities of daily living and 10 elderly healthy subjects performing 240 scripted and 52.4 hours of continuous unscripted normal activities. Results show that using a simple algorithm employing IMPACT+POSTURE+VELOCITY can achieve a low false-positive rate of less than 1 FP/day (0.94FPs/day) with a sensitivity of 94.6% and a specificity of 100%. The algorithms were tested using continuous unsupervised activities performed by elderly healthy subjects, which is the target environment for a fall detection device.Physical activity classification using a single triaxial accelerometer based on HMM
http://dl-live.theiet.org/content/conferences/10.1049/cp.2010.1045
This study focuses on physical activity classification method using a single triaxial accelerometer attached on chest. With acceleration data acquired by a wearable wireless device, features are extracted using sliding window to describe different activity types. Hidden Markov Model (HMM) is used to recognize physical activity sequence. A modified Viterbi algorithm is used to find the optimal state sequence. The experimental results on 6 subjects have achieved an overall accuracy of 99.59% using our method, which is the best result so far.Ultra low power wireless communication for biomedical monitoring: trade-offs and design challenges
http://dl-live.theiet.org/content/conferences/10.1049/ic_20060298
This papers presents a solution to the shortcomings of current implantable and wearable sensors - the Sensium. This Toumaz solution is a low cost disposable integrated sensor chip that uses ultra low power. It is a tiny, non-intrusive module, a generic wireless sensor, and locally intelligent. Sensium-enabled `digital plaster' is a non-intrusive monitoring for chronic disease management and does not require battery change. Sensor input types supported include, ECG, 3-axis accelerometers, pressure, temperature, amperometric-N, amperometric-P, potentiometric, auxiliary voltage input and direct digital input.Estimation of moving statuses by fuzzy reasoning method using a triple axes accelerometer
http://dl-live.theiet.org/content/conferences/10.1049/cp_20060396
Moving statuses for walking, going up and down on the stairs are estimated using fuzzy reasoning method. In order to estimate those statuses, the frequency distribution is made for each variable by obtained data. After that strategic values are decided. And membership function for each value are defined based on experience, obtained each membership function is weighted and combined each membership function after that finally rules are decided 208 patterns. The rules and membership are examined the statuses in order to get validity for daily use. Although more adjust membership function, the study shows enable to use for daily use to estimate statuses. The result also can apply to estimate consumption calorie for activating our daily living. (4 pages)Design of a new type three-axis acceleration sensor
http://dl-live.theiet.org/content/conferences/10.1049/cp_20061124
A new type of three-axis full shearing strain acceleration sensor has been developed. It uses strain gauge as sensing element for the detection of acceleration. The sensor consists of an elastic body and inertial mass. The elastic body is a thin cylinder on which four holes are opened evenly in two levels. There are three Wheatstone bridges on the beams to detect the acceleration in three directions. The sensor was designed from the results of finite element method (FEM) simulation. As indicated by the calculations and experiments, this sensor is not only of high sensitivity and adequate rigidity in the three directions, but also of fairly small cross sensitivities and low hysteresis.Identification of an optimum accelerometer and gyroscope configuration for fall detection during simulated falls
http://dl-live.theiet.org/content/conferences/10.1049/cp_20050342
This paper describes the development of an accurate, accelerometer and gyroscope based fall-event detection system to distinguish between activities of daily living (ADL) and fall-events. Using simulated fall-events onto crash mats (under supervised conditions) and ADL performed by elderly subjects, distinguishing between falls and ADL is achieved using accelerometer and gyroscope-based sensors, mounted on the trunk and thigh of the person. Data analysis was performed using MATLAB<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">®</sup> to determine the peak accelerations and angular velocities recorded during eight different types of falls. A fall detection algorithm was proposed using thresholding techniques. Results from an evaluation of the detection algorithm show that a fall-event can be distinguished from an ADL with 100% accuracy using a single threshold applied to the resultant acceleration signal from a tri-axial accelerometer located at the chest. Thresholding was thus demonstrated to be capable of discriminating between an ADL and a fall-event, when those falls were simulated falls.Quantitative analysis of gait using footswitches and accelerometers in elderly fallers
http://dl-live.theiet.org/content/conferences/10.1049/cp_20050343
Falls are a leading cause of accidental death in the elderly. Orthostatic hypotension (OH) has a high prevalence in the elderly and is a significant risk factor for falls. We evaluated the gait variability of older adult fallers who were falling due to OH and compared it to the gait variability of older adult fallers in whom OH was excluded as a cause and a healthy control group of older adult non-fallers. We hypothesised that persons with OH might have subtle underlying gait abnormalities as a result of repeated episodes of cerebral hypoperfusion. Using footswitches the temporal gait parameters of these subjects were examined; stride time, swing time, stance time, percent stance time and walking speed, and the variability of these parameters from stride-to-stride was determined. Simultaneously, using accelerometers we examined the stride-to-stride variability of head and trunk acceleration in both the anterior-posterior (AP) and medio-lateral (ML) directions. The OH fallers were shown to walk significantly slower and to spend a greater proportion of the gait cycle in the stance phase than the control group - gait adaptations that were also evident in the NOH faller group. Despite reducing their walking speed, the gait variability was significantly increased in the OH faller group compared to the control group. This demonstrates measurable gait abnormalities in patients with OH suggesting that haemodynamic changes may not be the only contributing factor to falls.Computer aided measurement of velocity fields in liquid flows
http://dl-live.theiet.org/content/conferences/10.1049/cp_19970988
This paper presents a computer aided measurement of velocity fields based on the hydrogen bubble method. This method uses streaks of hydrogen bubbles to trace how the water flows. The bubbles are generated in a transparent section of a pipe and the images are captured using a video camera with a stroboscopic lamp. The data collected is further processed off-line by a workstation. The processing comprises two main stages: image and data processing. In the first stage the electrode and hydrogen streaks are located and measured. The second stage performs a numerical processing of data and creates a graphical output. The software was used for processing sixteen sequences, each ten images long and 94.6% of all hydrogen streaks were measured correctly compared with manual processing. On a typical workstation, processing takes of the order of minutes compared with weeks of manual work. The paper describes these stages in details and shows the results.Measurement of multiple velocities in multiphase flow
http://dl-live.theiet.org/content/conferences/10.1049/ic_19960580
The work described consists of investigating an entirely novel technique for measuring the velocity of the flowing components in vertically upward, gas/liquid flows in the “Cap bubble” and “Taylor bubble” flow regimes. The technique consists of mounting an array of 64 axially separated conductivity sensors in a vertical pipe through which an air/water mixture is flowing (water is the continuous component). By cross-correlating the output signals from any two of these conductivity sensors it is possible to obtain the mean Cap bubble (or Taylor bubble) velocity and hence an estimate of the mean gas velocity. The novel element of the work is to demonstrate that by appropriately combining the output signals from the array of 64 conductivity sensors it is possible to determine the output signals that would be obtained from one or more “simulated impedance sensors” that are travelling through the flow at the same speed as the Cap bubbles (or Taylor bubbles). Cross-correlation of the outputs from two of these simulated conductivity sensors, travelling in between the Cap bubbles, allows the liquid velocity relative to these moving sensors to be determined. Since the velocity of the simulated sensors is known, the liquid velocity can be determined. (4 pages)Mechanical characterisation of a polysilicon accelerometer
http://dl-live.theiet.org/content/conferences/10.1049/ic_19961219
This paper describes a measurement system which has been developed to determine, experimentally, the dynamic characteristics of microstructures. These characteristics include dynamic mode shape of free vibration, natural frequencies and modal damping factors. The system is demonstrated by determining the dynamic characteristics of a polysilicon accelerometer designed and produced at DRA Malvern. The accelerometer takes the form of a 2 μm thick polysilicon plate supported at as corners by beam like ligaments. Acceleration causes bending defections of the plate against the elasticity of the ligaments and this is taken as a measure of acceleration. The mechanical design of the sensor was carried using finite element analysis (ANSYS). In the experimental evaluation of the dynamics of the accelerometer the sensor was mounted within a general purpose piezoelectric staging and excited into vibration by applying a swept sine excitation to the piezoelectric. Using a laser vibrometer the notion of an array of selected test points on the accelerometer was measured and point frequency response functions calculated over a frequency range of 0 to 100 kHz. Using this data the dynamic mode shapes, natural frequencies and modal damping factors were calculated and the experimental behaviour of the sensor observed by animating a wire framed drawing of the structure. The mechanical damping of the accelerometer is determined by the behaviour of the squeeze film between the plate and the supporting substrate. (7 pages)Chemically resolved NMR velocimetry
http://dl-live.theiet.org/content/conferences/10.1049/ic_19960570
Of particular relevance to process engineering is the potential sensitivity of NMR imaging to fluid displacement, which allows measurement of fluid velocities (in the range mm/s to m/s), even in opaque fluids, in three spatial dimensions (NMR velocimetry). The chemical sensitivity of the NMR technique has often been overlooked in NMR velocimetry implementations, but we present one protocol for the simultaneous measurement of fluid velocity for the separate components of a flowing mixture of chemical compounds. The fluid flow in the expansion/contraction pipe system is found to be fully characterised in three spatial dimensions. Thus, chemically resolved NMR velocimetry allows a five-dimensional (three spatial, one temporal and one chemical shift) measurement to be made, non-invasively and in optically opaque liquids. (4 pages)Analysis of human muscle activity
http://dl-live.theiet.org/content/conferences/10.1049/ic_19960642
Illustrates the use of visualisation techniques in the analysis of recordings of muscle activity. Surface electromyogram (EMG) and mechanomyogram (MMG) signals were recorded simultaneously, along with muscle force from the quadriceps of 10 able-bodied subjects during isometric exercise. The MMG signal records muscle vibrations via a small accelerometer attached to the skin surface over the muscle belly and the EMG is recorded using standard electrodes attached to the skin over the muscle. The signals were recorded over four seconds for each of 11 levels of muscle force ranging from 0 to 100% maximum voluntary contraction. Model order estimation methods provide us with an insight into the number of processes involved in the generation of complicated signals. They also provide a means of assessing the suitable dimensionality of input data for subsequent classification methods. The visualisation method discussed in this paper is based on unsupervised learning, i.e. the target labels of the input data are not used during training. Although they provide an indication of the likely success of classification methods, it should be commented that the reduction from a high dimensional space to a lower dimension will generally incur a loss of information. Therefore, classification techniques which make full use of the higher dimensional space, such as radial basis functions, generally give better results than those based purely on the output positions of the Kohonen map. (6 pages)Usage of the spatial filter method for measurements of local particle velocities in multiphase flows
http://dl-live.theiet.org/content/conferences/10.1049/ic_19960574
The optical spatial filter method is based upon the evaluation of light distributions by grating-like structures. The velocity of objects moving through the measuring volume is obtained by determining. the center frequency of a signal delivered by a light receiver observing that volume. The most common realization of this method is laser Doppler anemometry. The measurement volume is located within an intersection of two focused laser beams; a grating results from interference. A single light receiver observes an integral over the intersection area. In our present work, the grating function is performed within the optical receiver. The active gratings simplify the optical arrangement. In order to apply the spatial filter measuring system to multiphase flows with high solid concentrations or optically dense fluids a special probe has been designed. This probe guides light to the measurement volume at its tip and ensures the visibility of particles in this volume for the light receiver. Thus, it is possible to measure the particle velocity at any position inside a gas/solid or fluid/solid flow. The measurement range can be adjusted to the process easily by changing the focal length of the used lens. (3 pages)Fibre optic reference beam laser Doppler velocimetry
http://dl-live.theiet.org/content/conferences/10.1049/ic_19951211
A compact reference beam laser Doppler velocimeter, constructed using a semiconductor laser diode, optical fibre components and semiconductor detectors, is reported. The device has been designed to overcome many of the problems commonly associated with reference beam configurations. The anemometer may be operated with the laser diode operating in cw and pulsed modes, demonstrating its applicability to wavelength and time division multiplexing schemes for 3D laser Doppler velocimetry. The probe is used to measure the velocity of a spinning disk in the range -20 m/s to +20 m/s. (6 pages)Enhancing speed management by in-car speed assistance systems
http://dl-live.theiet.org/content/journals/10.1049/iet-its.2009.0038
Intelligent speed adaptation (ISA) systems support drivers to comply with the legal speed limits. This functionality is expected to become increasingly important in speed management if integrated well with more traditional speed management measures. Based on state-of-the-art scientific literature, this study describes the current knowledge on the effects of ISA and the willingness of stakeholders to adopt ISA. Although the expected effects of the various ISA types are promising and stakeholders are willing to adopt ISA, the large-scale deployment of ISA is still lacking. The main challenges with respect to ISA deployment relate to its social and political feasibility. Overall, a more active role of public authorities is recommended on ISA deployment, especially for ISA systems that actively intervene in the driving task.Estimation of activity energy expenditure based on activity classification using multi-site triaxial accelerometry
http://dl-live.theiet.org/content/journals/10.1049/el_20082139
A wireless networked multi-site triaxial accelerometry system has been devised to estimate activity energy expenditure during daily life. A notable feature of the devised system is the utilisation of activity classification based on multi-site acceleration signals. During performance evaluation tests on a single subject, the proposed method showed higher correlation (adjusted <i xmlns="http://pub2web.metastore.ingenta.com/ns/">R</i><sup xmlns="http://pub2web.metastore.ingenta.com/ns/">2</sup>=0.952) and smaller estimation deviation (0.76 kcal/min) than two methods without activity classification (multi-site case: adjusted <i xmlns="http://pub2web.metastore.ingenta.com/ns/">R</i><sup xmlns="http://pub2web.metastore.ingenta.com/ns/">2</sup>=0.924, estimation deviation=0.892 kcal/min and single-site case: adjusted <i xmlns="http://pub2web.metastore.ingenta.com/ns/">R</i><sup xmlns="http://pub2web.metastore.ingenta.com/ns/">2</sup>=0.855, estimation deviation=1.18 kcal/min).Classification of basic daily movements using a triaxial accelerometer
http://dl-live.theiet.org/content/journals/10.1049/mbec_20043915
A generic framework for the automated classification of human movements using an accelerometry monitoring system is introduced. The framework was structured around a binary decision tree in which movements were divided into classes and subclasses at different hierarchical levels. General distinctions between movements were applied in the top levels, and successively more detailed subclassifications were made in the lower levels of the tree. The structure was modular and flexible: parts of the tree could be reordered, pruned or extended, without the remainder of the tree being affected. This framework was used to develop a classifier to identify basic movements from the signals obtained from a single, waist-mounted triaxial accelerometer. The movements were first divided into activity and rest. The activities were classified as falls, walking, transition between postural orientations, or other movement. The postural orientations during rest were classified as sitting, standing or lying. In controlled laboratory studies in which 26 normal, healthy subjects carried out a set of basic movements, the sensitivity of every classification exceeded 87%, and the specificity exceeded 94%; the overall accuracy of the system, measured as the number of correct classifications across all levels of the hierarchy, was a sensitivity of 97.7% and a specificity of 98.7% over a data set of 1309 movements.Low cross-axis sensitivity micro-gravity microelectromechanical system sandwich capacitance accelerometer
http://dl-live.theiet.org/content/journals/10.1049/mnl.2011.0137
This Letter presents the design and implementation of a highly symmetric microelectromechanical system sandwich accelerometer using a double-device-layer silicon-on-insulator (D-SOI) wafer. The proof mass of though-wafer-thickness is suspended by eight L-shaped beams mirror-symmetrically. The suspension system provides flexible mechanical suspension without large chip area consumption. Therefore the accelerometer is immune from trade-off between sensing capacitance and structure flexibility. The sensing mode (first vibration mode) of the accelerometer is successfully decoupled from other variation modes that followed. Thereby, the accelerometer is insensitive to the lateral acceleration and the rotation disturbance. The symmetric beam-mass structure is fabricated from both sides of the D-SOI wafer symmetrically using a combination of anisotropic wet etching and dry etching process. The accelerometer has high opened-loop capacitance sensitivity of 55 pF/±1 g. The closed-loop sensitivity is 1.096 v/g and the cross-axis sensitivity is 0.356%. The resolution of the accelerometer is 4.167 µg/√Hz (0–200 Hz at 1 atm).Investigating body motion patterns in patients with Parkinson's disease using matching pursuit algorithm
http://dl-live.theiet.org/content/journals/10.1049/mbec_20043839
Several recent studies have quantified abnormalities in Parkinsonian gait. However, few studies have attempted to quantify the regularity of body motion during walking in patients with Parkinson's disease. The aim of the paper was to characterise body motion patterns in healthy, elderly subjects and patients with Parkinson's disease during walking. Body motion was recorded during walking for 16 patients with Parkinson's disease and ten healthy, elderly subjects using a tri-axial accelerometer device. To characterise the body motion patterns, time–frequency patterns of the body acceleration signal were estimated using a matching pursuit algorithm. Data from the study showed that the healthy, elderly subjects and patients with Parkinson's disease had different time–frequency patterns. The time–frequency patterns were classified into four distinct patterns based on their time durations: vertical (<0.15 s), circular (0.15–0.5 s), short horizontal (0.5–2.0 s) and long horizontal (>2.0 s). The data showed that the energy of the long horizontal patterns, representing long-term smooth and regular (rhythmic) activities, significantly decreased, but the energy of the circular patterns, representing irregular activities, increased in the patients with mild Parkinson's disease, compared with those of the healthy, elderly subjects (<i xmlns="http://pub2web.metastore.ingenta.com/ns/">p</i><0.01). Futhermore, these features were seen more clearly in the body motions of severe case patients than is that of mild case patients. It was concluded that these differences are probably due to a lack of ability to control normal and smooth movement is Parkinson's disease.Analysis of head movements coupled with trunk drift in healthy subjects
http://dl-live.theiet.org/content/journals/10.1049/mbec_20054005
Accelerometers were used to measure sequential head tilt and trunk drift in 14 healthy young subjects while they performed three kinds of head task. First, maximum inclination angles in anterior, posterior, right and left directions were measured to estimate cervical ranges of motion for flexion–extension and lateral bending. The inclination angles measured (61.2° on average for flexion, 51.7° for extension, 42.7° for right bending and 43.9° for left bending) were consistent with previous findings. Secondly, cross-correlation analysis was applied to evaluate the degree of functional coupling between the head and trunk during flexion–extension and lateral bending. Significantly higher correlation coefficients were found between head tilt and trunk drift when these movements were in the same (iso-) directional condition than in a different (allo-) directional condition. The coupled trunk drift in flexion–extension for the iso-directional condition (10.3° on average) was much larger than for the allo-directional condition (2.3°). Finally, head turning was recorded as oval traces in a biaxial plane. In both clockwise and counter-clockwise head turning conditions, the maximum inclination angles of the traces were larger in the anterior–posterior direction (59.8° anterior and 58.2° posterior, in the clockwise condition, and 47.4° and 47.4° in the counter-clockwise condition) than in the right–left direction (36.3° right and 39.0° left, in the clockwise condition, and 40.5° and 36.7° in the counter-clockwise condition), and the angles in the four directions were almost equal to flexion–extension and lateral bending. The characteristics of the traces recorded and a possible application of the present recording system are discussed.Optical inertial rotation sensor using semiconductor ring laser
http://dl-live.theiet.org/content/journals/10.1049/el_19981249
A novel optical inertial rotation sensor using a semiconductor ring laser (SRL) is proposed. The Sagnac frequency shift was detected for the first time as a beat note by the terminal voltage change of an SRL without branching the circulating optical power. These results show the feasibility of very small, simple optical gyroscopes.Realisation of silicon piezoresistive accelerometer with proof mass-edge-aligned-flexures using wet anisotropic etching
http://dl-live.theiet.org/content/journals/10.1049/mnl.2011.0717
This Letter presents simulation, fabrication and testing of a high-performance quad-beam silicon piezoresistive accelerometer with very low cross-axis sensitivity. Cross-axis sensitivity in piezoresistive accelerometers is an important issue particularly for high-performance applications. In the present Letter, low cross-axis sensitivity is achieved by improving the device stability by placing four flexures in line with the proof mass edges. The accelerometer device is realised in a single-step double-sided bulk micromachining technique using a 5% dual-doped tetra methyl ammonium hydroxide solution as an anisotropic etchant. Test results of four fabricated devices show an average prime-axis sensitivity of 559.5 µV/g/5 V, a maximum cross-axis sensitivity of 0.62% full scale (FS acceleration=13 g) of the prime-axis sensitivity and nonlinearity at a level of 0.5% of FS which are comparatively better than already reported devices and commercially available piezoresistive sensors.<i xmlns="http://pub2web.metastore.ingenta.com/ns/">In vitro</i> validation of some flow assumptions for the prediction of the pressure distribution during obstructive sleep apnoea
http://dl-live.theiet.org/content/journals/10.1049/mbec_20053951
An adequate description of the pressure distribution exerted by the fluid flow on pharyngeal walls is a first requirement to enhance the understanding, modelling and, consequently, the prediction of airway collapse during obstructive sleep apnoea. From a fluid mechanical point of view, several flow assumptions can be formulated to reduce the governing flow equations. The relevance of some major flow assumptions and the accuracy of the resulting flow description with respect to obstructive sleep apnoea was investigated on a rigid geometrical replica of the pharynx. Special attention was given to the influence of geometrical asymmetry and to the position of the flow separation point. An in vitro experimental and theoretical study of steady pharyngeal fluid flow is presented for different constriction heights and upstream pressures. Pressure and velocity distributions along a rigid in vitro replica of the oro-pharyngeal cavity were compared with different flow predictions based on various assumptions. Fluid flow models were tested for volume flow rates ranging from 5 to 120 l min<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">−1</sup> and for minimum apertures between 1.45 and 3.00 mm. Two-dimensional flow models were required and predicted experimental results with an accuracy of 15%. Flow theories classically used in the case of a Starling resistor provided poor agreement.Quaternion-based fusion of gyroscopes and accelerometers to improve 3D angle measurement
http://dl-live.theiet.org/content/journals/10.1049/el_20060124
Two methods to fuse a 3D gyroscope with a 3D accelerometer in order to measure rotations are presented. They are compared with a method requiring only a 3D gyroscope and assessed with a reference system. The good reported accuracies make this system suitable for clinical evaluation.Accelerometer-based gait recognition via voting by signature points
http://dl-live.theiet.org/content/journals/10.1049/el.2009.2301
A novel algorithm to recognise human identities via gait by body-worn accelerometers is presented. It uses acceleration information to measure human gait dynamics. Acceleration-based gait recognition is a non-intrusive biometric measurement, which is insensitive to changes of lighting conditions and viewpoint. The proposed algorithm first extracts signature points from gait acceleration signals, and then identifies the gait pattern using a signature point-based voting scheme. Experiments with a data set of 30 subjects show that the proposed algorithm significantly outperforms other existing methods and achieves a high recognition rate of 96.7% for the case of five accelerometers.Command control for functional electrical stimulation hand grasp systems using miniature accelerometers and gyroscopes
http://dl-live.theiet.org/content/journals/10.1049/mbec_20033829
Recent commercially available miniature sensors have the potential to improve the functions of functional electrical stimulation (FES) systems in terms of control, reliability and robustness. A new control approach using a miniature gyroscope and an accelerometer was studied. These sensors were used to detect the linear acceleration and angular velocity of residual voluntary movements on upper limbs and were small and easy to put on. Five healthy subjects and three cervical spinal cord injured subjects were recruited to evaluate this controller. Sensors were placed on four locations: the shoulder, upper arm, wrist and hand. A quick forward-and-backward movement was employed to produce a distinctive waveform that was different from general movements. A detection algorithm was developed to generate a command signal by identifying this distinctive waveform through the detection of peaks and valleys in the sensor's signals. This command signal was used to control different FES hand grasp patterns. With a specificity of 0.9, the sensors had a success rate of 85–100% on healthy subjects and 82–97% on spinal cord injured subjects. In terms of sensor placement, the gyroscope was better as a control source than the accelerometer for wrist and hand positions, but the reverse was true for the shoulder.Surface myomechanical responses recorded on a scanner galvanometer
http://dl-live.theiet.org/content/journals/10.1049/mbec_20023706
A moving magnet galvanometer equipped with lever and indentor was evaluated for mechanomyography (MMG). First, the precision of the galvanometer was tested on a piezo-electric disc actuator. Using a 50 mm lever, synthesised micro-motions with an amplitude of 1 µm could be detected (noise level<0.2 µm) at static indentation forces ranging from 0.1 to 2 N. Then the galvanometer was mounted on an isometric ankle dynamometer to sense calf-muscle responses (<i xmlns="http://pub2web.metastore.ingenta.com/ns/">N</i>=6). In the first protocol, twitch contractions were elicited by electrical stimulation while the indentation force was increased. Twitch amplitudes, twitch contraction times and twitch half-relaxation times were analysed from the surface and contraction responses. With indentation force (0.1–0.5 N), the amplitude of the surface responses increased (+61%), contraction and half-relaxation times, however, were not influenced. The mean twitch contraction time from the surface responses (60±11 ms) was shorter than that from the contraction responses (115±7 ms), indicating more fast-contracting fibres under the indented area. In the second protocol, voluntary target contractions were produced, and the surface responses were simultaneously recorded on an accelerometer. After double differentiation of the galvanometer signal, both acceleration MMGs showed a high coincidence in the time and frequency domains. With an indentation force of 2 N applied on the accelerometer, the signal amplitude (−10%) and the mean frequency (−19%) decreased. A specific application of this galvanometer–dynamometer test system is the assessment of regeneration processes in paraplegics with long-term denervated muscles.High performance fibre optic accelerometers
http://dl-live.theiet.org/content/journals/10.1049/el_19970087
The authors report the design and performance of fully packaged, field ruggedised, high performance fibre optic (FO) accelerometers. Appropriate design considerations have resulted in FO accelerometers with many desirable engineering features which include: (i) high sensitivity (>20 dB re rad/g), (ii) low noise (<1 micro-g√Hz at 1 kHz) (iii) broad frequency response (100 Hz to 14 kHz), (iv) low sensitivity to extraneous measurands (e.g. static pressure sensitivity < –200 dB re rad/µPa), (v) small size (<35 gms total), and (vi) low cross-axis sensitivity (<–35 dB). Single device or arrays of such devices can be incorporated in many structural and vibration sensing applications at low cost.Analysis and decomposition of accelerometric signals of trunk and thigh obtained during the sit-to-stand movement
http://dl-live.theiet.org/content/journals/10.1049/mbec_20053985
Piezoresistive accelerometer signals are frequently used in movement analysis. However, their use and interpretation are complicated by the fact that the signal is composed of different acceleration components. The aim of the study was to obtain insight into the components of accelerometer signals from the trunk and thigh segments during four different sit-to-stand (STS) movements (self-selected, slow, fast and fullflexion). Nine subjects performed at least six trials of each type of STS movement. Accelerometer signals from the trunk and thigh in the sagittal direction were decomposed using kinematic data obtained from an opto-electronic device. Each acceleration signal was decomposed into gravitational and inertial components, and the inertial component of the trunk was subsequently decomposed into rotational and translational components. The accelerometer signals could be reliably reconstructed: mean normalised root mean square (RMS) trunk: 6.5% (range 3–12%), mean RMS thigh: 3% (range 2–5%). The accelerometric signals were highly characteristic and repeatable. The influence of the inertial component was significant, especially on the timing of the specific event of maximum trunk flexion in the accelerometer signal. The effect of inertia was larger in the trunk signal than in the thigh signal and increased with higher speeds. The study provides insight into the acceleration signal, its components and the influence of the type of STS movement and supports its use in STS movement analysis.Phase spectrum method for time delay estimation using twin-plane electrical capacitance tomography
http://dl-live.theiet.org/content/journals/10.1049/el_20060338
Flow velocity distribution can be measured by means of a twin-plane tomography system and cross-correlation techniques. However, the use of these techniques based on finding the argument that maximises an estimated cross-correlation function (CCF) of corresponding pixels from two planes, in practice is limited by their low accuracy in reconstructed concentration. Presented is a method permitting the time delay to be measured with higher accuracy. The method is based on utilising the phase of the cross-spectral density of the CCF to estimate a time delay. The method is found to be more promising than the classical correlation method.Evaluation of a fall detector based on accelerometers: a pilot study
http://dl-live.theiet.org/content/journals/10.1049/mbec_20054044
As falls and fall-related injuries remain a major challenge in the public health domain, reliable and immediate detection of falls is important so that adequate medical support can be delivered. Available home alarm systems are placed on the hip, but have several shortcomings. A fall detector based on accelerometers and placed at head level was developed, as well as an algorithm able to distinguish between activities of daily living and simulated falls. Accelerometers were integrated into a hearing-aid housing, which was fixed behind the ear. The sensitivity of the fall detection was assessed by investigation into the acceleration patterns of the head of a young volunteer during intentional falls. The specificity was assessed by investigation into activities of daily living of the same volunteer. In addition, a healthy elderly woman (83 years) wore the sensor during the day. Three trigger thresholds were identified so that a fall could be recognised: the sum-vector of acceleration in the xy-plane higher than 2 g; the sum-vector of velocity of all spatial components right before the impact higher than 0.7 m s<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">−1</sup>; and the sum-vector of acceleration of all spatial components higher than 6 g. The algorithm was able to discriminate activities of daily living from intentional falls. Thus high sensitivity and specificity of the algorithm could be demonstrated that was better than in other fall detectors worn at the hip or wrist at the same stage of development.Detecting absolute human knee angle and angular velocity using accelerometers and rate gyroscopes
http://dl-live.theiet.org/content/journals/10.1049/mbec_20013589
Knee joint angle and angular velocity were calculated in real time during standing up and sitting down. Two small modules comprising rate gyroscopes and accelerometers were attached to the thigh and shank of two able-bodied volunteers and one T<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">5</sub> ASIA(A) paraplegic assisted by functional electrical stimulation (FES). The offset and drift of the rate gyroscopes was compensated for by auto-resetting and auto-nulling algorithms. The tilt of the limb segments was calculated by combining the signals of the accelerometer and the rate gyroscope. The joint angle was calculated as the difference in tilt of the segments. The modules were also tested on a two-dimensional model. The mean differences between the rate gyroscope–accelerometer system and the reference goniometer for the model, able-bodied and paraplegic standing trials were 2.1°, 2.4° and 2.3° respectively for knee angle and 2.3° s<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">− 1</sup>, 5.0° s<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">− 1</sup> and 11.8° s<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">−1</sup> respectively for knee velocity. The rate gyroscope–accelerometer system was more accurate than using the accelerometer as a tilt meter, possibly due to the greater bandwidth of the rate gyroscope–accelerometer system.Measuring orientation of human body segments using miniature gyroscopes and accelerometers
http://dl-live.theiet.org/content/journals/10.1049/mbec_20053979
In the medical field, there is a need for small ambulatory sensor systems for measuring the kinematics of body segments. Current methods for ambulatory measurement of body orientation have limited accuracy when the body moves. The aim of the paper was to develop and validate a method for accurate measurement of the orientation of human body segments using an inertial measurement unit (IMU). An IMU containing three single-axis accelerometers and three single-axis micromachined gyroscopes was assembled in a rectangular box, sized 20×20×30 mm. The presented orientation estimation algorithm continuously corrected orientation estimates obtained by mathematical integration of the 3D angular velocity measured using the gyroscopes. The correction was performed using an inclination estimate continuously obtained using the signal of the 3D accelerometer. This reduces the integration drift that originates from errors in the angular velocity signal. In addition, the gyroscope offset was continuously recalibrated. The method was realised using a Kalman filter that took into account the spectra of the signals involved as well as a fluctuating gyroscope offset. The method was tested for movements of the pelvis, trunk and forearm. Although the problem of integration drift around the global vertical continuously increased in the order of 0.5° s<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">−1</sup>, the inclination estimate was accurate within 3° RMS. It was shown that the gyroscope offset could be estimated continuously during a trial. Using an initial offset error of 1 rad s<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">−1</sup>, after 2 min the offset error was roughly 5% of the original offset error. Using the Kalman filter described, an accurate and robust system for ambulatory motion recording can be realised.Computational method and feasibility of detecting the whole body centre of gravity using an accelerometric device
http://dl-live.theiet.org/content/journals/10.1049/el_20071656
A novel computational method is presented and the feasibility of accelerometer measurement to accurately determine gait stability by means of estimating the centre of gravity (COG) during locomotion is highlighted. The inverse problem theory and methods were used to compute COG displacement data more accurately because any <i xmlns="http://pub2web.metastore.ingenta.com/ns/">a priori</i> information of initial displacement data was unknown.Inertial-grade in-plane resonant silicon accelerometer
http://dl-live.theiet.org/content/journals/10.1049/el_20061774
A micro-G detectable in-plane vibrating accelerometer is implemented by using a single crystalline silicon and glass-silicon anodic-bonded vacuum packaging technique. The sensing principle of the accelerometer is a gap-sensitive electrostatic stiffness changing effect. A mixed surface-bulk micromachining technology has been developed to use 40 µm-thick silicon as a structure material. The fabricated accelerometer shows a resolution of 5.2 µG and 128 Hz/G at the nominal frequency of 23.4 kHz.Gold nanoparticle distribution monitor for drug delivery system based on optically assisted ultrasonic velocity-change imaging
http://dl-live.theiet.org/content/journals/10.1049/el_20072106
Optical absorption images of the tissue mimic phantom including gold nanoparticles were obtained by detecting the ultrasonic velocity-change caused by light irradiation. A series of experimental results showed the possibility as a nanoparticle distribution monitor for the drug delivery system.40 dB fibre optical preamplifier in 1064 nm laser Doppler anemometer
http://dl-live.theiet.org/content/journals/10.1049/el_20000786
With a neodymium-doped fibre amplifier a small signal gain of 40 dB at 1064 nm has been achieved. Using the same amplifier as an optical preamplifier in a conventional 1064 nm laser Doppler anemometer (LDA), an improvement in the SNR of the LDA radiation and sensitivity enhancement in comparison to that for direct detection with a highly sensitive avalanche photodiode was obtained.Effect of accelerometer location on mechanomyogram variables during voluntary, constant-force contractions in three human muscles
http://dl-live.theiet.org/content/journals/10.1049/mbec_20043853
To understand better the features of the mechanomyogram (MMG) with different force levels and muscle architectures, the MMG signals detected at many points along three muscles were analysed by the application of a linear array of MMG sensors (up to eight) over the skin. MMG signals were recorded from the biceps brachii, tibialis anterior and upper trapezius muscles of the dominant side of ten healthy male subjects. The accelerometers were aligned along the direction of the muscle fibres. One accelerometer was located over the distal muscle innervation zone, and the other six or seven accelerometers were placed over the muscle, forming an array of sensors with fixed distances between them. The array covered almost the entire muscle length in all cases. MMG signals detected from adjacent accelerometers had similar shapes, with correlation coefficients ranging from about 0.5 to about 0.9. MMG amplitude and characteristic spectral frequencies significantly depended on accelerometer location. The MMG amplitude was maximum at the muscle belly for the biceps brachii and the tibialis anterior. Higher MMG characteristic spectral frequencies were associated with higher amplitudes in the case of the biceps brachii, whereas the opposite was observed for the tibialis anterior muscle. In the upper trapezius, the relationship between characteristic spectral frequencies, MMG amplitude and contraction force depended on the accelerometer location. This suggested that MMG spectral features do not only reflect the mechanical properties of the recruited muscle fibres but depend on muscle architecture and motor unit territorial distribution. It was concluded that the location of the acce"lerometer can have an influence on both amplitude and spectral MMG features, and this dependence should be considered when MMG signals are used for muscle assessment.Classification of sit-to-stand locomotion task based on spectral analysis of waveforms generated by accelerometric transducer
http://dl-live.theiet.org/content/journals/10.1049/el_20062623
A new method to evaluate the ability to rise from a chair by means of the analysis of the sit-to-stand locomotion task is introduced. In particular, the method is based on the frequency analysis of the acceleration measurements supplied by a home-made transducer.Quadrature demodulation technique used in laser Doppler velocimetry
http://dl-live.theiet.org/content/journals/10.1049/el_19980389
The authors present a technique for applying quadrature demodulation to determine the frequency of Doppler signals. This technique enables low-frequency signals with less than one signal period to be measured. The dependence of measurement error on signal-to-noise-ratio and measurement time is also investigated.Analysis of dynamic cerebral autoregulation using an ARX model based on arterial blood pressure and middle cerebral artery velocity simulation
http://dl-live.theiet.org/content/journals/10.1049/mbec_20023691
The study aimed to model the cerebrovascular system, using a linear ARX model based on data simulated by a comprehensive physiological model, and to assess the range of applicability of linear parametric models. Arterial blood pressure (ABP) and middle cerebral arterial blood flow velocity (MCAV) were measured from 11 subjects non-invasively, following step changes in ABP, using the thigh cuff technique. By optimising parameters associated with autoregulation, using a non-linear optimisation technique, the physiological model showed a good performance (<i xmlns="http://pub2web.metastore.ingenta.com/ns/">r</i>=0.83±0.14) in fitting MCAV. An additional five sets of measured ABP of length 236±154 s were acquired from a subject at rest. These were normalised and rescaled to coefficients of variation (CV=SD/mean) of 2% and 10% for model comparisons. Randomly generated Gaussian noise with standard deviation (SD) from 1% to 5% was added to both ABP and physiologically simulated MCAV (SMCAV), with ‘normal’ and ‘impaired’ cerebral autoregulation, to simulate the real measurement conditions. ABP and SMCAV were fitted by ARX modelling, and cerebral autoregulation was quantified by a 5 s recovery percentage <i xmlns="http://pub2web.metastore.ingenta.com/ns/">R</i>5% of the step responses of the ARX models. The study suggests that cerebral autoregulation can be assessed by computing the <i xmlns="http://pub2web.metastore.ingenta.com/ns/">R</i>5% of the step response of an ARX model of appropriate order, even when measurement noise is considerable.Influence of muscle fibre shortening on estimates of conduction velocity and spectral frequencies from surface electromyographic signals
http://dl-live.theiet.org/content/journals/10.1049/mbec_20043902
The study of surface electromyographic (EMG) signals under dynamic contractions is becoming increasingly important. However, knowledge of the methodological issues that may affect such analysis is still limited. The aim of the study was to analyse the effect of fibre shortening on estimates of conduction velocity (CV) and mean power spectral frequency (MNF) from surface EMG signals. Single fibre action potentials were simulated, as detected by commonly used spatial filters, for different fibre lengths. No physiological modifications were included with changes in fibre length, and thus only geometrical artifacts related to fibre shortening were investigated. The simulation results showed that the dependence of CV and MNF on fibre shortening is affected by the fibre location, electrode position and the spatial filter applied. With shortening of up to 50% for a fibre of 50 mm semi-length, the variations in CV and MNF estimates with shortening in bipolar recordings were 0.5% (CV) and 0.7% (MNF) for superficial fibres, and 3.6% and 5.1% for deeper fibres. Using the longitudinal double differential filter, under the same conditions, the percent variation was 0% and 0.2%, and 24.7% and 15.8%, respectively. The main conclusions were, first, muscle fibre shortening can significantly affect estimates of CV and MNF, especially for short fibre lengths. However, for long (semi-length >50 mm) and superficial fibres, this effect is limited for shortenings of up to 50% of the initial fibre length. Secondly, CV and MNF are almost equally affected by changes in muscle length; and, thirdly, sensitivity to fibre shortening depends on the spatial filter applied for signal detection.Adaptive processing bandwidth adjustment for laser Doppler flowmetry
http://dl-live.theiet.org/content/journals/10.1049/mbec_20043874
A novel laser Doppler flowmetry scheme is reported that adjusts the processing bandwidth adaptively to optimise the estimation of flow. To obtain an adequate processing bandwidth, the Doppler spectra is first fitted to the Lorentzian function, and the bandwidth at half the maximum of the Lorentzian function is used as an indicator of the major frequency range of the signal. The processing bandwidth is then tuned accordingly, and a frequency-weighted algorithm is applied to compute the fluid velocity. To investigate the influence of the processing bandwidth, an <i xmlns="http://pub2web.metastore.ingenta.com/ns/">in vitro</i> experiment was performed. In the experiment, the flow rate was controlled at constant velocity in the range from 0 to 18.52 mm s<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">−1</sup>, and the fluid velocity indices were calculated using adaptive and fixed processing bandwidths, respectively. The results showed that the adaptive processing bandwidth adjustment, not only significantly reduced the biological zero (9.6% of the case using 100 kHz bandwidth), but also enhanced the sensitivity of the laser Doppler measurement (over 20%) and linearly responded to a wider velocity range (R<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">2</sup>=0.979 for velocity from 0 to 18.52 mm s<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">−1</sup>).Computational methods to detect step events for normal and pathological gait evaluation using accelerometer
http://dl-live.theiet.org/content/journals/10.1049/el.2010.0532
The presented study highlights the feasibility and accuracy of novel computational methods based on a morphological filter and a least square acceleration filter to detect step events for evaluating normal and pathological gait parameters using a single accelerometer. This is the first evidence that demonstrates the feasibility and accuracy of the novel accelerometer-based system and methods in both normal and pathological populations.Reliability of the mechanomyogram detected with an accelerometer during voluntary contractions
http://dl-live.theiet.org/content/journals/10.1049/mbec_20033757
The accelerometer is used for mechanomyogram (MMG) recordings of muscle contractions. Although the mechanical characteristics of other MMG transducers have been determined with reference to the accelerometer, mechanical aspects of the accelerometer itself, including the weight of the transducer, have not been verified. This study was designed to reinvestigate the mechanical variable of the MMG signal detected with an accelerometer, with reference to a laser distance sensor (LDS), and then to clarify the influence of the accelerometer weight on the MMG recording during muscle contractions. The study was performed during mechanical sinusoidal vibrations and during voluntary contractions of the quadriceps muscle. Maximum differences in the amplitude spectral density functions between the LDS signal and the double integral of the accelerometer signal were approximately 4 µm. The results verified that the MMG signal from the accelerometer accurately reflected the acceleration of body surface vibration. However, the MMG signal was gradually distorted when weight was added to the accelerometer: the addition of 4.0 g (total 6.0 g, including 2.0 g of accelerometer) substantially attenuated the MMG signal. The results suggest that the appropriate weight for the accelerometer should be less than 5.0 g for measurements of the quadriceps muscle and indicate that the transducer weight must be taken into account for accurate measurement of muscles of different sizes.The mathematical theory of vibratory angular tachometers
http://dl-live.theiet.org/content/journals/10.1049/pi-c.1958.0021
A mathematical theory for a vibratory rate-of-turn measuring device is developed in order to bring out the more important characteristics.By using properties of Mathieu's equation it is shown how performance depends on the parameters of the system, particularly the resonant frequency and damping factor of the torsion mechanism. These results are compared with those obtained from the more simplified theory.New laser interferometry methods of measuring the velocity of high-speed model missiles
http://dl-live.theiet.org/content/journals/10.1049/ree.1970.0061
A modified Doppler technique is discussed, whereby a moving object is simultaneously illuminated by two intersecting laser beams which are coherent with one another. By comparing the different Doppler-shifted signals scattered, refracted, or diffracted from two overlapping light beams at the object, the velocity of high-speed missiles has been measured with good accuracy.Fibre-optic transit velocimetry using laser diode sources
http://dl-live.theiet.org/content/journals/10.1049/el_19880355
A simple fibre-based transit anemometer has been constructed using laser diode sources. A pair of single-mode optical fibres is used to facilitate the production of the input waists for the beamforming system directly and so reduce the required number of optical components. Extension to a twodimensional transverse system is straightforward.Confocal Fabry–Perot sensor
http://dl-live.theiet.org/content/journals/10.1049/el_19820155
The use of a spherical mirror Fabry–Perot (confocal) interferometer as an optical displacement sensor is described. The device incorporates a simple electronic servo to maintain the interferometer at an operating point of maximum sensitivity. Applications as vibration and acceleration sensors are forseen, with sensitivities for sinusoidal accelerations of 10<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">−3</sup> μg achievable at 10 Hz.DC fibre-optic accelerometer with sub-μ<i xmlns="http://pub2web.metastore.ingenta.com/ns/">g</i> sensitivity
http://dl-live.theiet.org/content/journals/10.1049/el_19860307
We describe a fibre-optic accelerometer, based on the technique of nonlinear displacement-to-strain conversion (NDSC), suitable for use at DC and low frequencies. The sensor exhibits a minimum detectable acceleration of less than 1 μ<i xmlns="http://pub2web.metastore.ingenta.com/ns/">g</i> RMS (<i xmlns="http://pub2web.metastore.ingenta.com/ns/">g</i> = 9.8 m/s<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">2</sup>) at 0.5 Hz and a linear dynamic range greater than 10<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">6</sup>.