1,721,089 research outputs found
Thick-film force, slip and temperature sensors for a prosthetic hand
No full textThick-film static and dynamic force sensors have been investigated for their suitability to measure the grip forces exerted upon an object held by a prosthetic hand, and to detect and correspondingly react to the possible slip of a gripped item. The static force sensors exploit the piezoresistive characteristics of commercially available thick-film pastes whilst the dynamic slip sensors utilise the piezoelectric behaviour of proprietary PZT pastes (lead zirconate titanate). The sensors are located upon stainless steel cantilever type structures that will be placed at the fingertips of each digit of the prosthetic hand. Temperature sensors are also included to provide temperature compensation for the force sensors and to prevent accidental thermal damage to the prosthesis. Results have shown that the static force sensor is capable of measuring fingertip forces in excess of 100 N, with an electrical half-bridge configuration sensitivity approaching 10 ?V/V•N (with scope for improvement) and maximum hysteresis below 4% of full scale, depending on the manner by which the cantilever sensor array is attached to the finger. Failure in the bonding mechanism that secures the PZT layer to the stainless steel cantilever meant that the proposed dynamic force sensor could not be evaluated. However, investigations using the same sensor design fabricated on an alumina substrate have shown the potential of the PZT dynamic force sensor to measure vibration and hence potentially operate as a slip sensor
Making sense of artificial hands
No full textA review of sensors for artificial hands is presented in terms of their range, specifications and characteristics. There is a growing need for sensors due to the development of prosthetic hands that have multiple degrees of freedom requiring finger coordination into different postures. The sensing of force, position (angle), object-slip and temperature allows for the control of these hands automatically and frees the user from cognitive burden. To make the best possible use of individual sensing elements, future controllers will need to combine data from different types of sensor. They may also have an integral power supply using a small battery or harvest energy from their environment and transmit data wirelessly
Variation in system gain when using voluntary EMG to control electrical stimulation of the same muscle
No full textThe functional form of the lognormal distribution as a sum of decaying exponential and sinusoidal terms applied to the isometric pinch force of human fingers
No full textThe transient data of the pinch force produced between the human forefinger and thumb have been shown to fit the functional form of the well-known lognormal density function. Isometeric force generation is achieved by the stochastic recruitment of individual motor units, which sum together. Evidence from animal and human experiments demonstrates that the force generation can be modelled by underdamped terms. It is shown that a lognormal time series (distribution) can be fitted to a sum of exponential decaying sinusoidal terms
Spectrophotometers for the clinical assessment of port-wine stain skin lesions: a review
No full textReflectance spectrophotometry is the most established and widely used objective technique for the assessment of port-wine stain (PWS) skin, and has been applied extensively in other dermatological applications. To date, no review has been published regarding the different spectrophotometric devices used on PWS skin. This paper comprises such a review, introducing the reader to the relevant background material and then discussing scanning, narrow-band and tristimulus spectrophotometers in turn. Scanning spectrophotometry is the most versatile of the three methods but it is noted that considerable expertise is required to interpret the acquired data. Narrow-band and tristimulus devices are available at a much lower price and can be considerably simpler to use. They do, however, provide limited information that does not account for the complex effects of melanin and other chromophores within the skin. Although scanning spectrophotometers would be the preferred choice for most investigations, cheaper, simpler and equally reliable options are available and may better suit the needs of some research projects
Surface EMG pattern analysis of the wrist muscles at different speeds of contraction
No full textThe aim of this study is to investigate the characteristics of surface electromyographic signals, particularly in pattern analysis. The data were collected from the wrist muscles (flexor carpi ulnaris and extensor carpi radialis) of 20 healthy participants. The study focuses on the movement of the wrist muscles at different frequencies. Participants were asked to contract their muscles at four different speeds (60, 90 and 120 cycles a minute and maximum speed) during wrist flexion and extension, co-contraction and isometric contraction. In this work, moving approximate entropy, mean absolute value and kurtosis are evaluated from the surface electromyographic signals at the four speeds. Moving approximate entropy and kurtosis analysis show that there are significant differences at three states of contraction; start, middle and end. It is shown that there are more regular data in a surface electromyographic signal at the beginning and end of a muscle contraction with low regularity during the middle part
Finite element modelling of skin on a cellular level
No full textEven though the electrical properties of skin have been investigated for more than 70 years, a better understanding is becoming ever more important for medical applications. This is because electronic and computational technology has advanced dramatically over the last decade, so there is much potential for creating improved prostheses for disabled patients. An improved understanding of the electrical properties of the skin will facilitate the design of non-invasive electrodes and the associated electronics for improving the efficacy of signals sent into the body, for instance for (i) stimulation of muscles and neurons, as well as (ii) sensing neuron, muscle or other ion transport processes in the body.A popular approach for considering the electrical properties skin in a theoretical model has been to use circuit equivalent models, where the skin structure is considered as a combination of resistors and capacitors. This method leads to a low resolution model, ignoring the potential effects of structures such as sweat glands and hair follicles, as well as heterogeneity within the dermis, epidermis and subcutaneous regions. More recently Finite Element Models have been developed to more accurately reflect the skin’s structure; so far these have been developed for the macro scale by modelling skin as homogenous layers with static dielectric properties. Here we will present our early phase studies where Finite Element Models are being developed to model the skin at higher resolution with a view to gain a better understanding of how physical changes and differences in the skin structure impacts on the electrical properties of skin, most notably of value for functional electrical stimulation applications
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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