Individuals with severe physical disabilities and minimal motor behaviour may benefit from access technologies that harness the volitional activity of muscles. In this thesis, we investigate the use of muscle activity, indicated by the mechanomyogram (MMG), as a binary and multifunction control signal for access devices. A challenge in the design of a binary MMG switch is to reliably recognize the timing of voluntary muscle contractions, and to subsequently translate the MMG signal into a switch-activation signal. A continuous wavelet transform (CWT) algorithm based on a simplified MMG generation model of recurring impulsive morphological patterns was proposed for automatic detection of muscle activity from MMG signals. CWT coefficients of the MMG signal were compared to scale-specific thresholds derived from the baseline signal to estimate the timings of muscle activity. The automatic detection algorithm was implemented as a binary switch controlled by a single muscle site at the forehead, shoulders or forearm. The binary control algorithm was verified on able-bodied participants, and the switch was tested on individuals with neuromuscular and neurological disabilities. The switch showed very high sensitivity and specificity when the muscle and its control were minimally affected by spasticity, involuntary movement, or involuntary muscle activity. We further investigate the potential of improving the functionality of the MMG-controlled switching interface. We demonstrate the practical use of the vibratory artefact measured at the forehead during vocalization to control a second switch. The proposed integrated MMG-vocalization access solution may augment access alternatives for individuals with physical disabilities using a single access site. Further, we show that multi-site MMG signals exhibit distinctive patterns of forearm muscle activity, and 7+/-1 hand movements can be identified with an accuracy of 90+/-4%. This suggests that MMG may have applications in multi-function body-machine interfaces when multiple muscle sites are available. However, MMG signal features vary with sensor location. We show that sensor displacements significantly diminish classification accuracy, emphasizing the importance of consistent sensor placement between MMG classifier training and deployment for accurate control of switching interfaces. Collectively, the findings and developments of this thesis lay the foundation for future research on wearable, MMG-driven access technologies.

Infrared thermal imaging of the periorbital regions of the face shows promise as an input signal modality for an alternative communication system for individuals with conditions that preclude speech or voluntary movement, such as total locked-in syndrome. However, it was unknown if the startle response triggers a change in the skin temperature of these regions; such a change could generate false positives in a thermography-based access system. This study presents an examination of the temperature characteristics of the periorbital regions of 11 able-bodied adult participants before and after an auditory startle stimulus. The results show that the startle response has no substantial effect on the mean temperature of the periorbital regions. This indicates that thermography-based access solutions would be insensitive to startle reactions in their user, an important advantage over other modalities being considered in the context of access solutions for individuals with a severe motor disability.

Infrared thermal imaging of the periorbital regions of the face shows promise as an input signal modality for an alternative communication system for individuals with conditions that preclude speech or voluntary movement, such as total locked-in syndrome. However, it was unknown if the startle response triggers a change in the skin temperature of these regions; such a change could generate false positives in a thermography-based access system. This study presents an examination of the temperature characteristics of the periorbital regions of 11 able-bodied adult participants before and after an auditory startle stimulus. The results show that the startle response has no substantial effect on the mean temperature of the periorbital regions. This indicates that thermography-based access solutions would be insensitive to startle reactions in their user, an important advantage over other modalities being considered in the context of access solutions for individuals with a severe motor disability.

Individuals with severe physical disabilities and minimal motor behaviour may benefit from access technologies that harness the volitional activity of muscles. In this thesis, we investigate the use of muscle activity, indicated by the mechanomyogram (MMG), as a binary and multifunction control signal for access devices. A challenge in the design of a binary MMG switch is to reliably recognize the timing of voluntary muscle contractions, and to subsequently translate the MMG signal into a switch-activation signal. A continuous wavelet transform (CWT) algorithm based on a simplified MMG generation model of recurring impulsive morphological patterns was proposed for automatic detection of muscle activity from MMG signals. CWT coefficients of the MMG signal were compared to scale-specific thresholds derived from the baseline signal to estimate the timings of muscle activity. The automatic detection algorithm was implemented as a binary switch controlled by a single muscle site at the forehead, shoulders or forearm. The binary control algorithm was verified on able-bodied participants, and the switch was tested on individuals with neuromuscular and neurological disabilities. The switch showed very high sensitivity and specificity when the muscle and its control were minimally affected by spasticity, involuntary movement, or involuntary muscle activity. We further investigate the potential of improving the functionality of the MMG-controlled switching interface. We demonstrate the practical use of the vibratory artefact measured at the forehead during vocalization to control a second switch. The proposed integrated MMG-vocalization access solution may augment access alternatives for individuals with physical disabilities using a single access site. Further, we show that multi-site MMG signals exhibit distinctive patterns of forearm muscle activity, and 7+/-1 hand movements can be identified with an accuracy of 90+/-4%. This suggests that MMG may have applications in multi-function body-machine interfaces when multiple muscle sites are available. However, MMG signal features vary with sensor location. We show that sensor displacements significantly diminish classification accuracy, emphasizing the importance of consistent sensor placement between MMG classifier training and deployment for accurate control of switching interfaces. Collectively, the findings and developments of this thesis lay the foundation for future research on wearable, MMG-driven access technologies.

While haptics, tactile displays, and other topics relating to non-visual user interfaces have been the subject of a variety of research initiatives, little has been done specifically related to those for blind driving. Many automation technologies have been developed for the purpose of assisting and improving the safety of sighted drivers, but to enable a true driving experience without any sense of sight has been an essentially overlooked area of study. Since 2005, the Robotics & Mechanisms Laboratory at Virginia Tech has assumed the task of developing non-visual interfaces for driving through the Blind Driver Challenge®, a project funded by the National Federation of the Blind. The objective here is not to develop a vehicle that will autonomously mobilize blind people, but to develop a vehicle that a blind person can actively and independently operate based on information communicated by non-visual interfaces. This thesis proposes some generalized considerations for the development of non-visual interfaces for driving, using the instructional interfaces developed for the Blind Driver Challenge® as a case study. A model is suggested for the function of blind driving as an open-loop control system, wherein the human is an input/output device. Further, a discussion is presented on the relationship between the bandwidth of information communicated to the driver, the amount of human decision-making involved in blind driving, and the cultivation of driver independence. The considerations proposed here are intended to apply generally to the process of non-visual interface development for driving, enabling efficient concept generation and evaluation. / Master of Science

Access technologies facilitate novel and alternative methods for individuals with disabilities to interact with their environment. Finding suitable access solutions for children with severe spastic quadriplegic cerebral palsy can be difficult because of their poor motor control and targeting abilities due to spasticity at the limbs, neck, and head. In this research a multiple camera tongue switch was developed for a 7 year-old case study participant with severe spastic quadriplegia. Remotely via video, this system reacts to tongue protrusions as cues for single-switch access. Having multiple cameras mitigates targeting problems with the head that conventional single camera systems would present. Results of a usability experiment with the participant show that good sensitivity (82%) and specificity (80%) can be achieved with a non-contact tongue protrusion access modality for a user with spastic quadriplegia. Moreover, the experiment verified that the extra cameras improve utility of video-based access technologies for the target population.

Access technologies facilitate novel and alternative methods for individuals with disabilities to interact with their environment. Finding suitable access solutions for children with severe spastic quadriplegic cerebral palsy can be difficult because of their poor motor control and targeting abilities due to spasticity at the limbs, neck, and head. In this research a multiple camera tongue switch was developed for a 7 year-old case study participant with severe spastic quadriplegia. Remotely via video, this system reacts to tongue protrusions as cues for single-switch access. Having multiple cameras mitigates targeting problems with the head that conventional single camera systems would present. Results of a usability experiment with the participant show that good sensitivity (82%) and specificity (80%) can be achieved with a non-contact tongue protrusion access modality for a user with spastic quadriplegia. Moreover, the experiment verified that the extra cameras improve utility of video-based access technologies for the target population.

Evidence suggests that cerebral blood flow patterns accompanying a mental activity are retained in many locked-in patients. Thus, real-time monitoring with functional transcranial Doppler (TCD) together with a specific mental task could control a brain-computer interface (BCI), thereby providing self-initiated interaction. The objective of this study was to create an automatic detection algorithm to differentiate hemodynamic responses coincident with one's performance of verbal fluency (VF) versus counting tasks. We recruited 10 healthy adults who each silently performed up to 30 VF tasks and counted between each. Both middle cerebral arteries were simultaneously imaged using TCD. Linear Discriminant Analyses (LDA) successfully differentiated between VF and both prior and post counting tasks. For every participant, LDA achieved the 70% classification accuracy sufficient for BCIs. Results demonstrate automatic detection of a VF task by TCD and warrant further investigation of TCD as a BCI.

Evidence suggests that cerebral blood flow patterns accompanying a mental activity are retained in many locked-in patients. Thus, real-time monitoring with functional transcranial Doppler (TCD) together with a specific mental task could control a brain-computer interface (BCI), thereby providing self-initiated interaction. The objective of this study was to create an automatic detection algorithm to differentiate hemodynamic responses coincident with one's performance of verbal fluency (VF) versus counting tasks. We recruited 10 healthy adults who each silently performed up to 30 VF tasks and counted between each. Both middle cerebral arteries were simultaneously imaged using TCD. Linear Discriminant Analyses (LDA) successfully differentiated between VF and both prior and post counting tasks. For every participant, LDA achieved the 70% classification accuracy sufficient for BCIs. Results demonstrate automatic detection of a VF task by TCD and warrant further investigation of TCD as a BCI.

Past studies have shown that the effects of selective auditory attention are evident in medial olivocochlear (MOC) activity, manifested as the contralateral suppression (CS) of transient evoked otoacoustic emissions (TEOAEs). This finding suggests the use of TEOAEs in the design of an auditory-based access technology as a potential access solution for children with severe disabilities. Thirteen participants with normal hearing threshold and normal middle ear function completed this study. The participants were instrumented with a TEOAE ear probe and presented with a contralateral acoustic stimulus. They were instructed to alternate auditory attention conditions as visually cued by symbols on an LCD display. Attentive and non-attentive conditions were detected with an overall accuracy of 70.17 +/- 12.54% at 2.44 +/- 0.3 bits per minute in a participant-specific classifier, and 65.92 +/- 13.91% in a participant-independent classifier. Detection of auditory attention exceeded random chance levels for 11 of 13 participants.