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Rehabilitation Engineering, IEEE Transactions on

Issue 3 • Date Sep 1998

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Displaying Results 1 - 11 of 11
  • Three-dimensional tactile display for the blind

    Page(s): 249 - 256
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (168 KB)  

    A tactile display device that can present tangible relief graphics for visually impaired persons has been developed. The tactile surface consists of a 64×64 arrangement of tactor-pins with 3 mm interspacing. The tactor-pins are aligned in a hexagonal, rather than a square formation, to assure smooth depiction. The matrix has a total area of 200 mm×170 mm. Each pin can be raised in 0.1 mm steps to a maximum height of 10 mm. Users can get certain information by touching the pins raised at varying heights with fingers and/or palms. Laboratory assessment of the device with six blind subjects showed its ability to transmit various kinds of information View full abstract»

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  • Theoretical performance and clinical evaluation of transverse tripolar spinal cord stimulation

    Page(s): 277 - 285
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    A new type of spinal cord stimulation electrode, providing contact combinations with a transverse orientation, is presented. Electrodes were implanted in the cervical area (C4-C5) of two chronic pain patients and the stimulation results were subsequently simulated with a computer model consisting of a volume conductor model and active nerve fiber models. For various contact combinations a good match was obtained between the modeling results and the measurement data with respect to load resistance (less than 20% difference), perception thresholds (16% difference), asymmetry of paresthesia (significant correlation) and paresthesia distributions (weak correlation). The transversally oriented combinations provided the possibility to select either a preferential dorsal column stimulation, a preferential dorsal root stimulation or a mixed stimulation. The (a)symmetry of paresthesia could largely be affected in a predictable way by the selection of contact combinations as well. The transverse tripolar combination was shown to give a higher selectivity of paresthesia than monopolar and longitudinal dipolar combinations, at the cost of an increased current (more than twice) View full abstract»

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  • Impact of a poka-yoke device on job performance of individuals with cognitive impairments

    Page(s): 269 - 276
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    Job performance and production related issues are important not only to successful vocational training and ultimate job placement for individuals with cognitive disabilities, but also for their ability to have expanded vocational options. This study hypothesized that the application of Kaizen philosophy, and poka-yoke techniques in particular, could create job opportunities and improve productivity of individuals with cognitive disabilities. Poka-yoke or error-proofing techniques are part of the collection of Kaizen techniques. Kaizen refers to continuous improvement in performance, cost/effectiveness, and quality. Kaizen strives to empower the worker, increase worker satisfaction, facilitate a sense of accomplishment, and thereby create pride-of-work. These techniques typically reduce the physical and cognitive demands of a task and thereby render the task more accessible. The job was a fuel clamp assembly. A redesigned assembly fixture was the poka-yoke intervention. Consistent with poka-yoke principles, the intervention improved the productivity of everyone attempting the assembly. In particular, the workers in this study showed an 80% increase in productivity and an average percent error drop from 52% to about 1% after the process redesign. Furthermore, the workers showed improved morale, self-esteem, and pride-of-work. Prior to the process redesign, only the higher functioning workers could successfully perform the assembly. After the redesign a greater number of workers could successfully perform the assembly. These results not only validated the study hypothesis, but demonstrated that the success facilitated by applying Kaizen techniques had similar results with individuals with cognitive disabilities as with nondisabled workers View full abstract»

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  • A mathematical model for skeletal muscle activated by N-let pulse trains

    Page(s): 286 - 299
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    A physiologically based mathematical model for skeletal muscle activated by neural impulses is presented. This model is developed specifically to capture the behavior for mammalian skeletal muscle activated by M-lets (sets of N high-frequency pulses with variable interpulse intervals). N-let pulse trains have been demonstrated as a possible means of producing contractions with reduced fatigue and fiber-type transformation, while maximizing the force-time integral per pulse (FTIpP) of electrically stimulated muscle. This model is developed by modeling the underlying biophysical processes responsible for the initiation and maintenance of force generation in muscle. The release and reaccumulation dynamics of calcium ions from the sarcoplasmic reticulum are modeled and proposed as the governing mechanism for the observed N-let effects. It is found that the new model is robust, numerically stable and easily implemented. Simulation results are presented that demonstrate the model's ability to capture a variety of the nonlinear summation, force and stiffness variation effects seen experimentally when activating skeletal muscle with N-lets. General properties of FES muscle are also predicted by the model. The significant insight provided by this model into the internal dynamics of skeletal muscle is used to assess a variety of mechanisms proposed for N-let behavior. It is postulated that the calcium release and reaccumulation dynamics, as incorporated in this model, are responsible for the N-let effects found in experiment View full abstract»

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  • A static dynamometer measuring simultaneous torques exerted at the upper limb

    Page(s): 309 - 315
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    The majority of available dynamometers are designed to measure force or torque in one specific direction, one joint at a time. For the quantification of motor incoordination in neurological patient populations, these dynamometers provide limited information about the global behavior of the limb under investigation. This report describes the potential use and function of a static dynamometer measuring torques exerted simultaneously at the shoulder (flexion-extension, abduction-adduction, internal-external rotation), elbow (flexion-extension), and forearm (pronation-supination). Orthogonal forces were measured at the arm and wrist using strain gauge transducers interfaced with a laboratory computer. The lever arms were specified to a software program and the joint torques were calculated in real time according to static equilibrium equations. The use of the dynamometer is illustrated by characterizing for one hemiparetic subject, the joints torques recorded at the shoulder, elbow, and forearm during isolated submaximal grip exertions at different force levels on both sides. The torques generated at the shoulder, elbow and forearm during the hand grip tasks on the affected side were significantly higher than those obtained on the nonaffected side and increased with the grip force level. These differences probably reflect the loss of movement selectivity observed following a lesion in the central nervous system. Further studies are currently being undertaken in neurological patient populations to characterize and quantify motor deficits using this dynamometer. As a long term goal, the authors hope that the method and technologies described here will contribute to the evaluation and rehabilitation of these populations View full abstract»

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  • Design, control, and characterization of a sliding linear investigative platform for analyzing lower limb stability (SLIP-FALLS)

    Page(s): 334 - 350
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    A novel device, the Sliding Linear Investigative Platform For Analyzing Lower Limb Stability (SLIP-FALLS), has been designed to study the detection and discrimination thresholds of humans to uniaxial horizontal step, ramp, or sinusoidal translations of the surface upon which they stand or stride. The device also can be used to test the human potential for, and mechanisms of, slips and falls. The SLIP utilizes air bearing technology and a noncontact linear motor to produce ultra-low-vibration translations. The FALLS system measures the forces on four load cells, platform linear and head tri-axial accelerations, four channels of electromyographic data, motor voltage, and a subject's psychophysical response; and derives other physiological and biomechanical measures, like center-of-pressure and shear force. The effect of acceleration and shear force on the accuracy of the center-of-pressure calculations is presented. Operating ranges depend on the interactions among displacement, velocity, acceleration, and jerk parameters for linear translations, and between amplitudes and frequencies for sinusoidal translations. Displacements from 5 μm to 0.277 m, velocities from 5 μm/s to 0.3 m/s, and accelerations up to 2.5 m/s2 are achievable with precise control (i.e., without overshoot), but tradeoffs exist such that all three maxima cannot be reached simultaneously. For a 0.15 m/s linear translation at 4 m/s2 , SLIP-FALLS produces substantially less vibration than the worm-driven NeuroTest system. The usefulness of having precise control over movement parameters is discussed View full abstract»

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  • EEG-based communication: improved accuracy by response verification

    Page(s): 326 - 333
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (152 KB)  

    Humans can learn to control the amplitude of electroencephalographic (EEG) activity in specific frequency bands over sensorimotor cortex and use it to move a cursor to a target on a computer screen. EEG-based communication could provide a new augmentative communication channel for individuals with motor disabilities. In the present system, each dimension of cursor movement is controlled by a linear equation. While the intercept in the equation is continually updated, it does not perfectly eliminate the impact of spontaneous variations in EEG amplitude. This imperfection reduces the accuracy of cursor movement. The authors evaluated a response verification (RV) procedure in which each outcome is determined by two opposite trials (e.g., one top-target trial and one bottom-target trial). Success, or failure, on both is required for a definitive outcome. The RV procedure reduces errors due to imperfection in intercept selection. Accuracy for opposite-trial pairs exceeds that predicted from the accuracies of individual trials, and greatly exceeds that for same-trial pairs. The RV procedure should be particularly valuable when the first trial has >2 possible targets, because the second trial need only confirm or deny the outcome of the first, and it should be applicable to nonlinear as well as to linear algorithms View full abstract»

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  • A photoelastic study of ligament strain

    Page(s): 300 - 308
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    The anterior cruciate ligament (ACL) in the human knee is known to exhibit as large as 10-20% of strain in association with knee flexion, while usual Hookean elastic materials exhibit at most 0.3%. Furthermore the complex ACL in shape deforms in highly variable manners due to the complicated three-dimensional (3-D) movements of the insertions in association with knee flexion. Such large and highly variable deformations of the ACL cannot be adequately quantified by one-dimensional (1-D) and/or localized measurements. In order to measure strains over the entire area of the ACL, the authors employed the photoelastic coating method to analyze stress on the basis of the strains. A specific kind of polyurethane possessing optically high fringe-sensitivity was found to be most suitable for measurement purposes. From the preliminary experiments, it was found that a linear relation with 99% of correlation coefficient between the birefringence order and the strain on the polyurethane film continued up to 45% of strain. This study was done in two steps. In the first step, a study was done using a unique model of a knee joint fabricated in a way which allowed deformation and strain distribution in the model ACL to be directly observed and measured by means of the photoelastic coating method. It was confirmed that the film, having negligible effect on the mechanical properties of some biological soft tissues, closely reflected the strain behavior of the tissue. Thus in the second step, the photoelastic method was employed to measure the strains on an actual ACL during free flexion-extension of the knee. A specially designed apparatus was used to allow a natural motion of the knee. The photoelastic measurements demonstrated the potential utility of the application to measuring strain distributions not only on a model ligament but also on an actual ligament. The measurement of an actual ACL led the following results: the principal strain lines well depicted its fiber directions; a reciprocal function between the anterior and posterior bundles was observed; and there was a zero-strain area on the central and posterior sides near the tibial insertion View full abstract»

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  • A microfabricated electrostatic haptic display for persons with visual impairments

    Page(s): 241 - 248
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (160 KB)  

    An electrostatic haptic display with three 7×7 electrode arrays of three different sizes was fabricated on a 4-in wafer using lithographic microfabrication techniques. The display utilizes electrostatic stimulation to generate a tactile sensation of texture on a scanning finger. The tactile sensation appeared to be a result of increased friction and vibration due to the electrostatic forces between the finger skin and the electrodes. Various spatial tactile patterns (lines, circles, squares, and triangles, etc.) can be presented on the display. Experiments of threshold, line separation, and pattern recognition were performed on subjects with visual impairments to study the spatial resolution and information transmission on arrays of variant electrode size and spacing. Two columns with two-column spacing can be resolved with 80% accuracy on the small array, for a spatial resolution of 5.8 mm in terms of edge-to-edge electrode distance. The overall percentages of correct recognition for the patterns were 68.3, 72.1, and 71.3% on the small, medium, and large arrays, respectively. While subject is an important factor for both threshold and pattern recognition, electrode size was statistically significant for threshold only. Frequency and duty cycle of the stimulation waveform did not show statistical significance View full abstract»

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  • Speech modifications algorithms used for training language learning-impaired children

    Page(s): 257 - 268
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    In this paper, the details of processing algorithms used in a training program with language learning-impaired children (LLIs) are described. The training program utilized computer games, speech/language training exercises, books-on-tape and educational CD-ROMs. Speech tracks in these materials were processed using these algorithms. During a four week training period, recognition of both processed and normal speech in these children continually increased to near age-appropriate levels. The authors conclude that this form of processed speech is subject to profound perceptual learning effects and exhibits widespread generalization to normal speech. This form of learning and generalization contributes to the rehabilitation of temporal processing deficits and language comprehension in this subject population View full abstract»

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  • Separability of EEG signals recorded during right and left motor imagery using adaptive autoregressive parameters

    Page(s): 316 - 325
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    Electroencephalogram (EEG) recordings during right and left motor imagery can be used to move a cursor to a target on a computer screen. Such an EEG-based brain-computer interface (BCI) can provide a new communication channel to replace an impaired motor function. It can be used by, e.g., patients with amyotrophic lateral sclerosis (ALS) to develop a simple binary response in order to reply to specific questions. Four subjects participated in a series of on-line sessions with an EEG-based cursor control. The EEG was recorded from electrodes overlying sensory-motor areas during left and right motor imagery. The EEG signals were analyzed in subject-specific frequency bands and classified on-line by a neural network. The network output was used as a feedback signal. The on-line error (100%-perfect classification) was between 10.0 and 38.1%. In addition, the single-trial data were also analyzed off-line by using an adaptive autoregressive (AAR) model of order 6. With a linear discriminant analysis the estimated parameters for left and right motor imagery were separated. The error rate, obtained varied between 5.8 and 32.8% and was, on average, better than the on-line results. By using the AAR-model for on-line classification an improvement in the error rate can be expected, however, with a classification delay around 1 s View full abstract»

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Aims & Scope

This Transaction ceased publication in 2000. The current retitled publication is IEEE Transactions on Neural Systems and Rehabiliation Engineering.

Full Aims & Scope