Evaluation of semiautonomous navigation assistance system for power wheelchairs with blindfolded nondisabled individuals

Some individuals with disabilities are denied powered mobility because they lack the visual, motor, and/or cognitive skills required to safely operate a power wheelchair. The Drive-Safe System (DSS) is an add-on, distributed, shared-control navigation assistance system for power wheelchairs intended to provide safe and independent mobility to such individuals. The DSS is a human-machine system in which the user is responsible for high-level control of the wheelchair, such as choosing the destination, path planning, and basic navigation actions, while the DSS overrides unsafe maneuvers through autonomous collision avoidance, wall following, and door crossing. In this project, the DSS was clinically evaluated in a controlled laboratory with blindfolded, nondisabled individuals. Further, these individuals' performance with the DSS was compared with standard cane use for navigation assistance by people with visual impairments. Results indicate that compared with a cane, the DSS significantly reduced the number of collisions. Users rated the DSS favorably even though they took longer to navigate the same obstacle course than they would have using a standard long cane. Participants experienced less physical demand, effort, and frustration when using the DSS as compared with a cane. These findings suggest that the DSS can be a viable powered mobility solution for wheelchair users with visual impairments.     

Evaluation of an ambient noise insensitive hum-based powered wheelchair controller

Purpose: A recently-developed assistive technology nicknamed “the Hummer” was investigated as a potential powered wheelchair controller for individuals with severe and multiple disabilities. System performance in a noisy environment was compared to that obtained with a commercial automatic speech recognition (ASR) system. Method: A bi-hum driving protocol was developed to allow the Hummer to serve as a powered wheelchair controller. Participants performed several virtual wheelchair driving tasks of increasing difficulty using the two systems. Custom-written software recorded task execution time, number of commands issued and wall collisions, speed, and trajectory. Results: The bi-hum protocol was shown to be non-intuitive and required user training. Overall, the Hummer achieved lower performance relative to ASR. Once users became accustomed to the protocol, the difference in performance between the two systems became insignificant, particularly for the higher-difficulty task. Conclusions: The Hummer provides a promising new alternative for powered wheelchair control in everyday environments for individuals with severe and multiple disabilities who are able to hum, particularly for those with severe dysarthria which precludes ASR usage. A more intuitive driving protocol is still needed to reduce user frustration and mitigate user-generated errors; recommendations on how this can be achieved are given herein.

Implications for Rehabilitation

• The “Hummer” allows for noise-insensitive powered wheelchair control in everyday environments

• The “Hummer” accommodates individuals without functional speech or those with severe dysarthria to gain mobility independence, thus improving their quality of life.

     

Differences in participation based on self-esteem in power and manual wheelchair users on a university campus: a pilot study

Objectives: To examine the relationship of self-esteem and wheelchair type with participation of young adult manual and power wheelchair users with diverse physical disabilities. Design: Cross-sectional survey study. Setting: Large University Campus. Participants: A convenience sample of college students (N?=?39) with self-reported physical disabilities who are full time wheelchair users (>40 per week) and are two or more years post illness or injury. Interventions: Not applicable. Main outcome measures: The Rosenberg Self-Esteem Scale was used to measure self-esteem, and the Craig Handicap Assessment and Reporting Technique was used to measure participation. Results: Self-esteem correlated highly with cognitive independence (CI) (r?=?0.58), mobility (r?=?0.67) and social integration (SI) (r?=?0.52). Use of manual wheelchair was significantly related to higher levels of CI and mobility while longer use of any wheelchair (power or manual) was significantly associated with higher levels of mobility and SI. In addition higher self-esteem independently predicted a significant proportion of the variance in CI, mobility and SI, while type of wheelchair predicted a significant proportion of the variance in CI (p?Conclusions: High self-esteem was found to be the strongest predictor of participation in a population of young adults with mobility limitations. Better understanding of the factors influencing participation may help to facilitate new interventions to minimize the disparities between persons with disabilities and their able bodied peers.

• Implication for Rehabilitation

• A total of 46.8% of wheelchair users report the desire for increased community participant but face significant barriers.

• The type of wheelchair has been identified as having a large impact on participation.

• This study found self-esteem to be the strongest predictor of participation, which is notable because self-esteem is a characteristic that is potentially modifiable with treatment.

     

Clinical evaluation of semiautonomous smart wheelchair architecture (Drive-Safe System) with visually impaired individuals

Nonambulatory, visually impaired individuals mostly rely on caregivers for their day-to-day mobility needs. The Drive-Safe System (DSS) is a modular, semiautonomous smart wheelchair system aimed at providing independent mobility to people with visual and mobility impairments. In this project, clinical evaluation of the DSS was performed in a controlled laboratory setting with individuals who have visual impairment but no mobility impairment. Their performance using DSS was compared with their performance using a standard cane for navigation assistance. Participants rated their subjective appraisal of the DSS by using the National Aeronautics and Space Administration-Task Load Index inventory. DSS significantly reduced the number and severity of collisions compared with using a cane alone and without increasing the time required to complete the task. Users rated DSS favorably; they experienced less physical demand when using the DSS, but did not feel any difference in perceived effort, mental demand, and level of frustration when using the DSS alone or along with a cane in comparison with using a cane alone. These findings suggest that the DSS can be a safe, reliable, and easy-to-learn and operate independent mobility solution for visually impaired wheelchair users.     

Comparison between performances of three types of manual wheelchairs often distributed in low-resource settings

Purpose: This study was conducted to compare the performance of three types of chairs in a low-resource setting. The larger goal was to provide information which will enable more effective use of limited funds by wheelchair manufacturers and suppliers in low-resource settings. Methods: The Motivation Rough Terrain and Whirlwind Rough Rider were compared in six skills tests which participants completed in one wheelchair type and then a day later in the other. A hospital-style folding transport wheelchair was also included in one test. For all skills, participants rated the ease or difficulty on a visual analogue scale. For all tracks, distance traveled and the physiological cost index were recorded. Data were analyzed using repeated measures analysis of variance. Results: The Motivation wheelchair outperformed Whirlwind wheelchair on rough and smooth tracks, and in some metrics on the tight spaces track. Motivation and Whirlwind wheelchairs significantly outperformed the hospital transport wheelchair in all metrics on the rough track skills test. Conclusion: This comparative study provides data that are valuable for manufacturers and for those who provide wheelchairs to users. The comparison with the hospital-style transport chair confirms the cost to users of inappropriate wheelchair provision.

• Implications for Rehabilitation

• For those with compromised lower limb function, wheelchairs are essential to enable full participation and improved quality of life. Therefore, provision of wheelchairs which effectively enable mobility in the cultures and environments in which people with disabilities live is crucial. This includes low-resource settings where the need for appropriate seating is especially urgent.

• A repeated measures study to measure wheelchair performances in everyday skills in the setting where wheelchairs are used gives information on the quality of mobility provided by those wheelchairs.

• This study highlights differences in the performance of three types of wheelchairs often distributed in low-resource settings. This information can improve mobility for wheelchair users in those settings by enabling wheelchair manufacturers to optimize wheelchair design and providers to optimize the use of limited funds

     

The Prevalence and Severity of Physical Mobility Limitations in Older Adults with Intellectual Disabilities

Background The population of older adults with intellectual disabilities is growing, creating new challenges for individuals, families and service providers. Although there has been increased research into the ageing process for adults with intellectual disabilities, there is little focused research investigating physical mobility. Materials and Methods A proxy‐response telephone survey was conducted to establish the prevalence and severity of mobility limitations among adults with intellectual disabilities, aged 45 years and over, using validated instruments to quantify mobility in a representative population‐based sample. Results Surveys were completed for 128 people. Mobility limitations were common, but the prevalence varied depending on the definition of mobility limitation. The prevalence of limitations was greater among females than males, but no clear age trend was seen. Conclusions The common nature of mobility limitations among the growing population of older adults with intellectual disabilities has implications for service providers and policy‐makers.     

Participatory design in the development of the wheelchair convoy system

Background  

In long-term care environments, residents who have severe mobility deficits are typically transported by having another person push the individual in a manual wheelchair. This practice is inefficient and encourages staff to hurry to complete the process, thereby setting the stage for unsafe practices. Furthermore, the time involved in assembling multiple individuals with disabilities often deters their participation in group activities.     

A head orientated wheelchair for people with disabilities

PURPOSE: Most electric wheelchairs available on the market are joystick-controlled making people with hand or arm disabilities unable to control the wheelchairs easily. This study proposes a new head-orientated wheelchair design for people with disabilities. METHOD: This study involves a tilt sensor module fitted onto the operator's headgear that will sense head movements used to control the wheelchair's direction and speed. This system includes: the tilt sensor module, the signal processing circuit and a main controller. RESULTS: The average times required for completing experiments by seven volunteers using joystick-controlled and the newly developed wheelchairs were recorded. It was revealed that the difference in average operating time for the two wheelchairs were statistically insignificant (p>0.05). CONCLUSIONS: The wheelchair developed in this study, although not absolutely superior to the joystick-controlled method, should still provide a better alternative for people with disabilities unsuited to traditional input devices.     

Beyond the wheelchair: development of motorised transport for people with severe mobility impairments in developing countries

Purpose.?In developing countries, lack of over-the-road transportation reduces a vast number of disabled people to a life of begging, dependency and social isolation. Although there have been some excellent efforts to provide low-cost wheelchairs and hand-powered tricycles, little has been done to further provide transport for disabled people.

Methods.?To address this problem directly we devised a low-cost motorised wheelchair transporter prototype (the Skeeter) using a combination of bicycle parts, a custom built frame, and an inexpensive small engine for propulsion.

Results.?The Skeeter can provide independent operation and travel by a wheelchair user. It is an economically feasible solution to the lack of over-the-road transportation for people with mobility impairments in developing countries.

Conclusions.?The Skeeter has the potential to provide a major enhancement in the quality of life for people with disabilities in developing countries around the world.     

Performance testing of collision-avoidance system for power wheelchairs

The Drive-Safe System (DSS) is a collision-avoidance system for power wheelchairs designed to support people with mobility impairments who also have visual, upper-limb, or cognitive impairments. The DSS uses a distributed approach to provide an add-on, shared-control, navigation-assistance solution. In this project, the DSS was tested for engineering goals such as sensor coverage, maximum safe speed, maximum detection distance, and power consumption while the wheelchair was stationary or driven by an investigator. Results indicate that the DSS provided uniform, reliable sensor coverage around the wheelchair; detected obstacles as small as 3.2 mm at distances of at least 1.6 m; and attained a maximum safe speed of 4.2 km/h. The DSS can drive reliably as close as 15.2 cm from a wall, traverse doorways as narrow as 81.3 cm without interrupting forward movement, and reduce wheelchair battery life by only 3%. These results have implications for a practical system to support safe, independent mobility for veterans who acquire multiple disabilities during Active Duty or later in life. These tests indicate that a system utilizing relatively low cost ultrasound, infrared, and force sensors can effectively detect obstacles in the vicinity of a wheelchair.     

Measurement Properties of the Late Life Disability Index Among Individuals Who Use Power Wheelchairs as Their Primary Means of Mobility

Objective

To examine the reliability, validity, and factor structure of the Late Life Disability Instrument (LLDI) in individuals who use power wheelchairs as their primary means of mobility.

Design

A 4-week, test-retest study design.

Setting

Five Canadian cities.

Participants

The validity sample included 115 new and experienced power mobility users, and the reliability sample included 85 experienced users (N=115). These volunteer samples included individuals who were aged ≥50 years and independently used power mobility as their primary means of mobility.

Interventions

Not applicable.

Main Outcome Measure

The LLDI measures participation in 2 dimensions of 16 life activities: frequency and perceived limitations. Validity measures included the Wheelchair Skills Test–power version, the Assistive Technology Outcomes Profile for Mobility, the Hospital Anxiety and Depression Scale, the Power Mobility Wheelchair Confidence Measure, and the Life Space Assessment.

Results

For the reliability sample, raw intraclass correlational coefficients for limitation and frequency dimension scores ranged from .855 (95% confidence interval .781–.905) to .883 (95% confidence interval, .822–.924), respectively. For the validity sample, scores on the LLDI were correlated as hypothesized with scores on validity measures. The factor structure that was identified with the original sample was not replicated among power wheelchair users. For LLDI frequency, exploratory factor analysis indicated that 5 of the original 16 items did not perform similarly among power wheelchair users. For LLDI limitations, a 1-factor, rather than a 2-factor, solution was identified.

Conclusions

The study provides evidence in support of the reliability and validity of the measure but suggests that the original subscale scores may not be applicable to power wheelchair users.     

A sports wheelchair for low-income countries

Purpose. Appropriate wheelchairs for basic mobility needs are still not commonly available in low-income countries, although several organizations are working toward this goal. After basic mobility is secured it is important to provide more diverse assistive technology to allow people with disabilities to more completely participate in society and live healthy lives. Our goal was to design an affordable sports wheelchair that would allow individuals in low-income countries to participate in basketball.

Methods. Design requirements established for the sports wheelchair included: removable anti-tippers, adjustable tension backrest, 24″ wheels, adjustable seat dump, variable camber, 4″ casters, fore-aft axle position, removable bumpers, height adjustable footrest, four wheels, single anti-tipper (pivot), cost less than $125 without wheels, 16″ seat width and backrest height, and nylon upholstery. The wheelchair was designed using 3D modeling, standard materials, and standard tools.

Discussion. An affordable wheelchair, versatile enough to be used for a variety of sports and even everyday use, was designed and prototyped successfully. Documentation for the design including step-by-step directions, engineering drawings, and photographs are available at the Human Engineering Research Laboratories website (http://www.herlpitt.org/intw.htm). Future work on the prototype should include design refinement including adaptations for other sports, and standards testing.     

Issues in maintenance and repairs of wheelchairs: A pilot study

In this pilot study, we assessed wheelchair durability and its effect on user satisfaction. Specifically, we examined the characteristics of the participants' wheelchairs, the types of maintenance and repairs completed, and whether the participants' satisfaction was affected by problems with their wheelchairs. A convenience sample of 130 participants who used wheelchairs as their primary means of mobility was recruited. Participants completed a questionnaire about their wheelchairs, the maintenance and repair history, and their satisfaction levels. Results showed that 26% of the participants had completed a wheelchair repair in the past 6 months, 16% had completed general maintenance, and 27% had completed tire repairs. Neither hours of wheelchair use nor wheelchair age affected repair or maintenance frequency. Participants were generally satisfied with their wheelchairs. Better understanding of wheelchair maintenance and repair issues will guide improvements in wheelchair design and enhance the community participation of individuals who use wheelchairs.     

Wheelchair racing efficiency

PURPOSE: For individuals with disabilities exercise, such as wheelchair racing, can be an important modality for community reintegration, as well as health promotion. The purpose of this study was to examine selected parameters during racing wheelchair propulsion among a sample of elite wheelchair racers. It was hypothesized that blood lactate accumulation and wheeling economy (i.e. oxygen consumed per minute) would increase with speed and that gross mechanical efficiency would reach an optimum for each athlete. METHOD: Twelve elite wheelchair racers with paraplegia participated in this study. Nine of the subjects were males and three were females. Each subject used his or her personal wheelchair during the experiments. A computer monitored wheelchair dynamometer was used during all testing. The method used was essentially a discontinuous economy protocol. Mixed model analysis of variance (ANOVA) was used to compare blood lactate concentration, economy (minute oxygen consumption), and gross mechanical efficiency across the stages. RESULTS: The results of this study show that both economy and blood lactate concentration increase linearly with speed if resistance is held constant. The subjects in this study had gross mechanical efficiencies (gme) of about 18%, with the range going from 15.222.7%. The results indicate that at the higher speeds of propulsion, for example near race speeds, analysis of respiratory gases may not give a complete energy profile. CONCLUSION: While there is a good understanding of training methods to improve cardiovascular fitness for wheelchair racers, little is known about improving efficiency (e.g. technique, equipment), therefore methods need to be developed to determine efficiency while training or in race situations.     

Adequacy of power wheelchair control interfaces for persons with severe disabilities: a clinical survey

The extreme difficulty with which persons with severe disabilities have been taught to maneuver a power wheelchair has been described in case studies, and anecdotal evidence suggests the existence of a patient population for whom mobility is severely limited if not impossible given currently available power wheelchair control interfaces. Since our review of the literature provided little evidence either in support or refutation of the adequacy of existing power wheelchair control interfaces, we surveyed 200 practicing clinicians, asking them to provide information about their patients and to give their impressions of the potential usefulness of a new power wheelchair navigation technology. Significant survey results were: Clinicians indicated that 9 to 10 percent of patients who receive power wheelchair training find it extremely difficult or impossible to use the wheelchair for activities of daily living. When asked specifically about steering and maneuvering tasks, the percentage of patients reported to find these difficult or impossible jumped to 40. Eighty-five percent of responding clinicians reported seeing some number of patients each year who cannot use a power wheelchair because they lack the requisite motor skills, strength, or visual acuity. Of these clinicians, 32 percent (27 percent of all respondents) reported seeing at least as many patients who cannot use a power wheelchair as who can. Nearly half of patients unable to control a power wheelchair by conventional methods would benefit from an automated navigation system, according to the clinicians who treat them. We believe these results indicate a need, not for more innovation in steering interfaces, but for entirely new technologies for supervised autonomous navigation.