P H Chappell

Salisbury NHS Foundation Trust, New Sarum, England, United Kingdom

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Publications (119)59.54 Total impact

  • [Show abstract] [Hide abstract]
    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.
    2013 International Conference on Electronics, Computer and Computation (ICECCO); 11/2013
  • 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.
    Human movement science 08/2011; 31(2):386-96. · 2.15 Impact Factor
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    ABSTRACT: A new method for texture sensing, based on a calculation of the average standard deviation of the data from a thick film piezoelectric sensor, is presented. The repeating patterns in the surface texture of gratings as they move past the sensor are observable in the output signal. A comparison with a previous method has shown an improvement in the variability of the analyzed data. The method applied is not only able to distinguish two patterns of gratings, but also provides the dimension of each grating. The results have demonstrated the suitability of this approach as a fingertip texture sensor.
    04/2011;
  • 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.
    Journal of Medical Engineering & Technology 01/2011; 35(1):1-18.
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    ABSTRACT: User perceptions are critical, yet often ignored factors in the design and development of rehabilitation technologies. In this article, measures for collection of patient perceptions are developed and applied to a novel upper limb workstation that combines robotic therapy and electrical stimulation (ES). Five participants with chronic upper limb hemiplegia post-stroke used a robotic workstation to undertake supported tracking tasks augmented by precisely controlled ES to their triceps muscle. Following a 6 week trial, a purpose designed set of questions was developed and individual interviews were conducted by an independent health psychologist. The simple, quick to administer question set showed that participants had a positive response to the system, and contributed valuable feedback with regard to its usability and effectiveness. Participants want a home-based system targeting their whole arm. This article demonstrates the value in assessing user perceptions of a rehabilitation system via a simple question set. While the results of this study have implications for a wider audience, our recommendations are for a qualitative study to develop a generic evaluation tool which could be used across the growing number of devices to provide feedback to enhance future development of any new technology for rehabilitation.
    Disability and rehabilitation. Assistive technology 01/2011; 6(2):130-8.
  • Tom Lister, Philip Wright, Paul Chappell
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    ABSTRACT: Reflectance 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.
    Lasers in Medical Science 05/2010; 25(3):449-57. · 2.40 Impact Factor
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    ABSTRACT: The primary objective of the experiments was to investigate the wrist motion of a person while they were carrying out a prehensile task from a clinical hand function test. A sixcamera movement system was used to observe the wrist motion of 10 participants. A very light sphere and a heavy sphere were used in the experiments to study any mass effects. While seated at a table, a participant moved a sphere over a small obstacle using their dominant hand. The participants were observed to move their wrist at a constant angular velocity. This phenomenon has not been reported previously. Theoretically, the muscles of the wrist provide an impulse of force at the start of the rotation while the forearm maintains a constant vertical force on a sphere. Light–heavy mean differences for the velocities, absolute velocities, angles and times taken showed no significant differences (p¼0.05).
    Journal of Medical Engineering & Technology 03/2010;
  • 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.
    Measurement Science and Technology 01/2010; 21(3):035203. · 1.44 Impact Factor
  • 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
    01/2010: pages 231-234;
  • 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.
    01/2010;
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    ABSTRACT: An inability to perform tasks involving reaching is a common problem for stroke patients. This paper provides an insight into mechanisms associated with recovery of upper limb function by examining how stroke participants’ upper limb muscle activation patterns differ from those of neurologically intact participants, and how they change in response to an intervention. In this study, five chronic stroke participants undertook nine tracking tasks in which trajectory (orientation and length), speed and resistance to movement were varied. During these tasks, EMG signals were recorded from triceps, biceps, anterior deltoid, upper, middle and lower trapezius and pectoralis major. Data collection was performed in sessions both before, and after, an intervention in which participants performed a similar range of tracking tasks with the addition of responsive electrical stimulation applied to their triceps muscle. The intervention consisted of eighteen one hour treatment sessions, with two participants attending an additional seven sessions. During all sessions, each participant’s arm was supported by a hinged arm-holder which constrained their hand to move in a two dimensional plane. Analysis of the pre intervention EMG data showed that timing and amplitude of peak EMG activity for all stroke participants differed from neurologically intact participants. Analysis of post intervention EMG data revealed that statistically significant changes in these quantities had occurred towards those of neurologically intact participants.
    Journal of electromyography and kinesiology: official journal of the International Society of Electrophysiological Kinesiology 10/2009; · 2.00 Impact Factor
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    ABSTRACT: In the April 2008 issue of Progress,we featured an article describing a new technique for improving arm movement following stroke developed at the University of Southampton.The technique involves the use of a robotic workstation delivering precisely controlled electrical stimulation mediated by iterative learning control to improve task performance.Here,the scientists who developed the system discuss the promising results of their pilot clinical study using this technique. Copyright © 2009 Wiley Interface Ltd
    Progress in Neurology and Psychiatry 08/2009; 13(5):16 - 20.
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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.
    Journal of Physics Conference Series 07/2009; 178(1):012022.
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    ABSTRACT: An overview is provided of the design, operation and performance of an experimental test facility that has been developed for stroke rehabilitation. The aim of the system is to improve sensory-motor function of the impaired upper limb, and it has recently been used in clinical trials with stroke participants. During treatment subjects were seated at the workstation and their impaired arm strapped to the robotic end-effector. Their task was to follow elliptical trajectories that were projected onto a target above their arm, using voluntary control with the addition of electrical stimulation mediated by advanced control schemes. The design of the experimental system is first summarised, and then details are presented of the modelling, identification and control techniques used by the workstation over the course of treatment.
    Rehabilitation Robotics, 2009. ICORR 2009. IEEE International Conference on; 07/2009
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    ABSTRACT: A summary is presented of the tracking and surface electromyographic (EMG) results obtained using a robotic workstation that was designed and built for use by stroke participants in order to improve voluntary control of their impaired arm. The intervention consisted of eighteen sessions in which five chronic stroke participants performed a range of tracking tasks using their remaining voluntary effort, with the addition of responsive electrical stimulation (ES) applied to their triceps muscles. Unassisted error tracking was measured during each intervention session. EMG, which may be related to impaired performance and function, was recorded in separate sessions before and after the intervention, in order to investigate changes in muscle activation patterns resulting from treatment. In these sessions, participants tracked similar trajectories without ES, and their muscle activity has been compared against that of eight neurologically intact subjects. Results are presented which describe changes in tracking ability and EMG, and their inter-relationship.
    Rehabilitation Robotics, 2009. ICORR 2009. IEEE International Conference on; 07/2009
  • 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.
    Journal of Medical Engineering & Technology 05/2009; 33(5):376-85.
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    ABSTRACT: An experimental test facility is developed for use by stroke patients in order to improve sensory-motor function of their upper limb. Subjects are seated at the workstation and their task is to repeatedly follow reaching trajectories that are projected onto a target above their arm. To do this they use voluntary control with the addition of electrical stimulation mediated by advanced control schemes applied to muscles in their impaired shoulder and arm. Full details of the design of the workstation and its periphery systems are given, together with a description of its use during the treatment of stroke patients.
    Medical Engineering & Physics 04/2009; · 1.78 Impact Factor
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    ABSTRACT: A model of the upper extremity 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 tests that can be performed in a short period of time. Examples of identified parameters obtained experimentally are presented for both stroke patients and unimpaired subjects. A discussion concerning the identification's repeatability, together with results confirming the accuracy of the overall representation, is given. The model has been used during clinical trials in which electrical stimulation is applied to the triceps muscle of a number of stroke patients for the purpose of improving both their performance at reaching tasks and their level of voluntary control over their impaired arm. Its purpose in this context is threefold: Firstly, changes occurring in the levels of stiffness and spasticity in each subject's arm can be monitored by comparing frictional components of models identified at different times during treatment. Secondly, the model is used to calculate the moments applied during tracking tasks that are due to a patient's voluntary effort, and it therefore constitutes a useful tool with which to analyze their performance. Thirdly, the model is used to derive the advanced controllers that govern the level of stimulation applied to subjects over the course of the treatment. Details are provided to show how the model is applied in each case, and sample results are shown.
    Journal of Biomechanical Engineering 04/2009; 131(3):031011. · 1.52 Impact Factor
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    ABSTRACT: In this paper iterative learning control schemes are used to apply functional electrical stimulation to the triceps of unimpaired subjects in order to perform trajectory tracking tasks. The subjects supply no voluntary effort and a robotic workstation is used to constrain their movement, impose known dynamics at the point of interaction with the robot, and provide assistive torque about the shoulder. Results from eighteen subjects are presented and show that a high level of performance can be achieved using the proposed method. In addition to illustrating how stimulation and robotics can be successfully combined in order to perform reaching tasks, the results provide justification for the system to be subsequently used by stroke patients for rehabilitation.
    03/2009;
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    ABSTRACT: Background: An inability to perform tasks involving reaching is a common problem following stroke. Evidence supports the use of robotic therapy and functional electrical stimulation (FES) to reduce upper limb impairments, but current systems may not encourage maximal voluntary contribution from the participant because assistance is not responsive to performance. Objective: To investigate whether iterative learning control (ILC) mediated by FES is a feasible intervention in upper limb stroke rehabilitation. Methods: Five hemiparetic participants with reduced upper limb function who were at least six months post stroke were recruited from the community. No participants withdrew. Intervention: Participants undertook supported tracking tasks using twenty-seven different trajectories augmented by responsive FES to their triceps brachii muscle, with their hand movement constrained in a two dimensional plane by a robot. Eighteen one hour treatment sessions were used with two participants receiving an additional seven treatment sessions. Outcome measures: The primary functional outcome measure was the Action Research Arm Test (ARAT). Impairment measures included the upper limb Fugl-Meyer Assessment (FMA), tests of motor control (tracking accuracy) and isometric force. Results: Compliance was excellent and there were no adverse events. Statistically significant improvements were measured (P≤0.05) in: FMA motor score, unassisted tracking for three out of four trajectories and in isometric force over five out of six directions. Changes in ARAT were not statistically significant. Conclusion: This study has demonstrated the feasibility of using ILC mediated by FES for upper limb stroke rehabilitation.
    Neurorehabilitation and neural repair 02/2009; · 4.28 Impact Factor