P H Chappell

University of Southampton, Southampton, England, United Kingdom

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Publications (70)32.51 Total impact

  • N.H.H.M. Hanif · P.H. Chappell · N.M. White · A.W. Cranny
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    ABSTRACT: Executing daily chores with missing limbs is undoubtedly very challenging. For a person who has lost his lower arm, it is highly desirable to replace this loss with a device that not only identical in appearance, but closely mimics its capabilities. While there are many prosthetic products of multiple functionalities in the current market, the capability of the device to replicate the tactile sensory system are often neglected. This research looks into supplementing a vibrotactile sensory feedback to the residual arm of prosthetic hand users. Surface information obtained at the fingertip of the prosthetic device becomes the input signals to the haptic actuator in generating vibration output. An Eccentric Rotation Mass (ERM) miniature motor has proven its capability to produce the required vibration in 2 dimensions within frequency bandwidth that matches the mechanoreceptor of the human skin. These findings are a stepping-Stone in creating a real tactile sensation for prosthetic users.
    No preview · Article · Jan 2014
  • N. H. H. Mohamad Hanif · P. H. Chappell · A. Cranny · N. M. White
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    ABSTRACT: One of the capability of a prosthetic hand device that is highly preferred is that it should be able to mimic the functionality of the lost arm, and that loss includes the tactile sensory system. A miniature DC motor has been identified to be the best haptic actuator to deliver the required sensory feedback. Experiments and simulations were carried out to predict the transient responses, driving frequencies as well as vibration amplitude of the motor. The results have shown that the motor is reliable in matching the optimum frequency response of the mechanoreceptors in the residual arm, which is important in providing an efficient supplementary sensation.
    No preview · Conference Paper · Nov 2013
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    T Lister · P A Wright · P H Chappell
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    ABSTRACT: A new Monte Carlo program is presented for simulating light transport through clinically normal skin and skin containing Port Wine Stain (PWS) vessels. The program consists of an eight-layer mathematical skin model constructed from optical coefficients described previously. A simulation including diffuse illumination at the surface and subsequent light transport through the model is carried out using a radiative transfer theory ray-tracing technique. Total reflectance values over 39 wavelengths are scored by the addition of simulated light returning to the surface within a specified region and surface reflections (calculated using Fresnel's equations). These reflectance values are compared to measurements from individual participants, and characteristics of the model are adjusted until adequate agreement is produced between simulated and measured skin reflectance curves. The absorption and scattering coefficients of the epidermis are adjusted through changes in the simulated concentrations and mean diameters of epidermal melanosomes to reproduce non-lesional skin colour. Pseudo-cylindrical horizontal vessels are added to the skin model, and their simulated mean depths, diameters and number densities are adjusted to reproduce measured PWS skin colour. Accurate reproductions of colour measurement data are produced by the program, resulting in realistic predictions of melanin and PWS blood vessel parameters. Using a modest personal computer, the simulation currently requires an average of five and a half days to complete.
    Full-text · Article · Oct 2013 · Lasers in Medical Science
  • Y. Zhuang · G. Chen · P.H. Chappell · M. Rotaru
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    ABSTRACT: Surface potential decay measurement is a widely used tool to test the electrical properties of insulation materials. However, physical mechanism of the surface potential decay is still poorly understood. In this paper, the effect of corona charging time has been investigated. It has been found that as charging time gets longer initially the surface potential decays faster which is consistent with the existing observations. However, after the charging time reaches a certain length (changing with charging voltage), the surface potential decay becomes slower as the charging time increases. This type of behaviour has not been reported in literature. Further study on this phenomenon using the Pulsed Electro-acoustic (PEA) method which quantifies charge distribution and dynamics inside the sample validated the observation. Finally, the surface potential decay curves were analysed by fitting a double exponential decay equation and simulated by a bipolar charge transport model.
    No preview · Conference Paper · Oct 2012
  • M B Warner · P H Chappell · M J Stokes
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    ABSTRACT: The aim of the present study was to examine the acromion marker cluster (AMC) method of measuring scapular kinematics during the arm lowering, eccentric, phase. Twenty six participants completed arm elevation and lowering in the sagittal, frontal and scapular plane. The participants held their arm at 30° increments while the orientation of the scapula was recorded using an AMC and a scapular locator (SL). There were no significant differences between the AMC and SL during the lowering phase for sagittal and scapular plane arm movements. The AMC significantly underestimated upward rotation (max RMSE = 6.0°), and significantly overestimated posterior tilt (max RMSE = 7.2°) during arm lowering in the frontal plane. The reported root mean square errors, however, were within the ranges observed during the elevation phase and reported in previous literature. The AMC therefore provides a reasonable description of scapular kinematics during the arm lowering phase.
    No preview · Article · Aug 2011 · Human movement science
  • P H Chappell
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    ABSTRACT: A 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.
    No preview · Article · Jan 2011 · Journal of Medical Engineering & Technology
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    N. Muridan · P. H. Chappell · A Cranny · N M White
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    ABSTRACT: This research has shown for the first time that the physical dimensions of small surface patterns in an object surface are detectable from sensors integrated into the fingertip and mechanical links of a prosthetic hand. A further novel aspect of this work is the use of the standard deviation of data used in the analysis. Charge amplifiers are used to extract the signal from the piezoelectric sensors when an object that has two grating surfaces moves past a fingertip. Similar signals have been observed from all the sensors. An analysis of the data has shown that the repeating pattern from the gratings is detectable from a calculation of the mean standard deviation. An estimate of the grating widths can also be made from this analysis. Approximately 32 and 58 grooves are in contact with fingertip (width 15mm) representing a resolution of 2 grooves and 4 grooves mm-1 respectively.
    Full-text · Article · Dec 2010 · Procedia Engineering
  • R J Lowe · P H Chappell · S.A. Ahmad
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    ABSTRACT: A slip sensor, using accelerometers, has been investigated for use in prosthetic design. The basis of this report is the characterization of this sensor including how it performs in re-gripping a falling object. The possibility of using three-axis vibration control is investigated and the limitations of this method are reported. A controller was produced to determine how reliable the sensor is when using both open- and closed-loop control methods. The conclusion is that the sensor is robust, and in addition to basic vibration, it is possible to use the sensor to calculate a reliable value for the distance of slip. Using statistical measures, a minimum grip force is given for successful re-grip without knowledge of the tangential friction forces.
    No preview · Article · Jan 2010 · Measurement Science and Technology
  • S. A. Ahmad · P. H. Chappell
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    ABSTRACT: An investigation of the fundamental operation of an artificial hand has been carried out with the aim to study the automatic control feedback for this system. The hand is modeled as a simple prehension system with three sensing elements; force, acceleration and slip. This prehension study focused on the object’s gripping and slippage processes. An automatic closed loop feedback control algorithm is developed to re-grip the object when it starts to slip which is similar in form to Hooke’s Law. The algorithm uses information from the distance of the object has slipped to re-grip the object and control the amount of force required. Also, a method called approximate entropy has been used to analyze and detect when the object begins to slip. This method can be used to prevent the object from slipping. KeywordsProsthesis control-prehension system-automatic feedback control-slip detection
    No preview · Chapter · Jan 2010
  • N Muridan · P H Chappell · D P J Cotton · A Cranny · N M White
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    ABSTRACT: A Piezoelectric thick-film sensor is a good candidate for the extraction of information from object slip in hand prosthesis. Five slip sensors were fabricated on different linkages of an artificial hand. The signals from each sensor were compared to the output from the sensor mounted on the fingertip. An analysis of the output signals from all the sensors indicates that the linkage sensors also produce similar output signals to the fingertip sensor. In the next phase of the research, velocity and acceleration of the slipped object will be considered in the analysis.
    No preview · Article · Jul 2009 · Journal of Physics Conference Series
  • S A Ahmad · P H Chappell
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    ABSTRACT: The 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.
    No preview · Article · May 2009 · Journal of Medical Engineering & Technology
  • C T Freeman · A-M Hughes · J H Burridge · P H Chappell · P L Lewin · E Rogers
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    ABSTRACT: A model of the upper limb is developed in which the forearm is constrained to lie in a horizontal plane and electrical stimulation is applied to the triceps muscle. Identification procedures are described to estimate the unknown parameters using a small number of tests. Examples of identified parameters obtained experimentally are presented for both stroke patients and unimpaired subjects. The model has been used to derive controllers which have been applied during clinical trials to reduce the level of impairment of stroke patients.
    No preview · Article · Jan 2009
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    ABSTRACT: This paper presents a compact analogue circuit for the controlling of prosthetic hands. The circuit captures directly surface EMG signals as the input by which the user will be able to select different postures. The proposed circuit is able to work using only one EMG source targeting patients with different levels of amputation. It is also adaptable for different users with different EMG amplitude signals and the motion of each finger can be varied in the circuit even with the single EMG. Real captured EMG signals are applied to the design and simulation results demonstrate the capability of the circuit in processing EMG signals and controlling the prosthetic hand in an efficient way. The circuit is designed and implemented with 0.12 mum CMOS technology and consumes 4 mW power for a set of sample postures.
    Full-text · Conference Paper · Dec 2008
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    ABSTRACT: A kinematic model is presented based on surface marker placement generating wrist, metacarpal arch, fingers and thumb movements. Standard calculations are used throughout the model and then applied to the specified marker placement. A static trial involving eight unimpaired participants was carried out to assess inter-rater reliability. The standard deviations across the data were comparable to manual goniometers. In addition, a test-retest trial of ten unimpaired participants is also reported to illustrate the variability of movement at the wrist joint, metacarpal arch, and index finger as an example of model output when repeating the same task many times. Light and heavyweight versions of the tasks are assessed and characteristics of individual movement strategies presented. The participant trial showed moderate correlation in radial/ulnar deviation of the wrist (r = 0.65), and strong correlation in both metacarpal arch joints (r = 0.75 and r = 0.85), the MCP (r = 0.79), and PIP (r = 0.87) joints of the index finger. The results indicate that individuals use repeated strategies of movement when lifting light and heavyweight versions of the same object, but showed no obvious repeated pattern of movement across the population.
    Full-text · Article · Apr 2008 · IEEE Transactions on Biomedical Engineering
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    C T Freeman · A-M Hughes · J H Burridge · P H Chappell · P L Lewin · E Rogers
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    ABSTRACT: The concept of ‘learned disuse’ is thought to be a significant barrier to recovery of sensory-motor function following a stroke. Unimpaired individuals learn new skills though practice, with feedback in various forms, but the problem facing the stroke patient is that they are unable to practice because of impaired motor control. Functional electrical stimulation (FES) can provide the experience for the patient of moving and consequently may limit the problem of learnt disuse and has been used with some success to improve recovery of upper limb motor control. Recent studies have shown that when stimulation is associated with a voluntary attempt to move the limb, improvement is enhanced but these techniques do not allow feedback that could be used to adjust stimulation parameters and thus provide more precise stimulation. This paper describes the design and construction of an experimental test facility that has been designed as part of a current project whose aim is to investigate the use of iterative learning control (ILC) and related strategies to mediate the electrical stimulation applied to a number of muscles of the shoulder and upper limb of stroke patients.
    Full-text · Article · Feb 2007 · Measurement and Control -London- Institute of Measurement and Control-
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    P.H. Chappell · P.N. Taylor
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    ABSTRACT: The 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.
    Full-text · Article · Jan 2007 · Computers in Biology and Medicine
  • D.P.J. Cotton · A Cranny · P H Chappell · N M White
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    ABSTRACT: INTRODUCTION Piezoelectric sensors produce a charge when mechanically deformed (for example through the action of an applied force). This charge decays with time dependant upon the connected electronics. This makes piezoelectric sensors an ideal candidate for detecting the vibrations (change in surface forces) associated with object slip from a prosthetic hand. Most previous work undertaken with piezoelectric sensors to detect object slip from upper limb prosthetics has used polyvinylidene fluoride strips (PVDF) (Dario 1996) (Howe 1989). This type of sensor has a low sensitivity of around 20-30 pCN-1 and comes in a sheet format so would have to be adhered manually to a hand. Thick-film piezoelectric sensors offer a superior alternative for this application with a much higher sensitivity than PVDF of around 130pCN-1 (Torah et al 2005) and the thick-film fabrication technique allows the sensors to be accurately printed onto the flat surface of a prosthesis finger or fingertip.
    No preview · Article · Jan 2007
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    ABSTRACT: This paper describes the experimental test facility that has been designed as part of a current project whose aim is to investigate the use of iterative learning control (ILC) and related strategies to mediate the electrical stimulation applied to a number of muscles of the shoulder and upper limb of stroke patients. ILC is a technique that has its origins in the area of industrial robotics and is especially targeted at systems operating in a repetitive mode with the additional requirement that a specified output trajectory over a finite interval (or trial) is followed to a specified level of precision. Motivated by human learning, the basic idea of ILC is to use information from previous executions of the task in order to improve performance from trial to trial. In the context of this work, ILC offers the opportunity of allowing the user to learn how to perfect a given task by controlling the amount of additional stimulation applied from one trial to the next. If this has been achieved, then further refinement is possible to reduce the stimulation effort supplied by the control scheme and thereby increase the effort necessary from the subject. In particular, ILC requires a basic representation of the underlying (dynamic) relationship between stimulation (or input) and response (or output) and also the specification of a target (or reference) trajectory to form the goal for the ILC scheme to achieve
    Full-text · Conference Paper · Oct 2006
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    D.J. Hart · P.N. Taylor · P.H. Chappell · D.E. Wood
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    ABSTRACT: Correction of drop foot in hemiplegic gait is achieved by electrical stimulation of the common peroneal nerve with a series of pulses at a fixed frequency. However, during normal gait, the electromyographic signals from the tibialis anterior muscle indicate that muscle force is not constant but varies during the swing phase. The application of double pulses for the correction of drop foot may enhance the gait by generating greater torque at the ankle and thereby increase the efficiency of the stimulation with reduced fatigue. A flexible controller has been designed around the Odstock Drop Foot Stimulator to deliver different profiles of pulses implementing doublets and optimum series. A peripheral interface controller (PIC) microcontroller with some external circuits has been designed and tested to accommodate six profiles. Preliminary results of the measurements from a normal subject seated in a multi-moment chair (an isometric torque measurement device) indicate that profiles containing doublets and optimum spaced pulses look favourable for clinical use.
    Full-text · Article · Jul 2006 · Medical Engineering & Physics
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    D.P.J. Cotton · A Cranny · P.H. Chappell · N.M. White · S.P. Beeby
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    ABSTRACT: Some of the traditional methods used to control a conventional prosthetic device are described alongside the current state of new control techniques and how they may progress. The review includes implantable myoelectric sensors and describes the potential of connecting directly to the peripheral nervous system. Control methods are then deduced for each technique, where the application is a six degrees of freedom hand having integral slip, force and temperature sensors.
    Full-text · Article · Jan 2006 · Measurement and Control -London- Institute of Measurement and Control-