Preliminary evaluation of variable compliance joystick for people with multiple sclerosis.

Upper-limb fatigue is a common problem that may restrict people with multiple sclerosis (MS) from using their electric powered wheelchair effectively and for a long period of time. The objective of this research is to evaluate whether participants with MS can drive better using a variable compliance joystick (VCJ) and customizable algorithms than with a conventional wheelchair joystick. Eleven participants were randomly assigned to one of two groups. The groups used either the VCJ in compliant or noncompliant isometric mode and a standard algorithm, personally fitted algorithm, or personally fitted algorithm with fatigue adaptation running in the background in order to complete virtual wheelchair driving tasks. Participants with MS showed better driving performance metrics while using the customized algorithms than while using the standard algorithm with the VCJ. Fatigue adaptation algorithms are especially beneficial in improving overall task performance while using the VCJ in isometric mode. The VCJ, along with the personally fitted algorithms and fatigue adaptation algorithms, has the potential to be an effective input interface for wheelchairs.

Comparison of virtual wheelchair driving performance of people with traumatic brain injury using an isometric and a conventional joystick.

UNLABELLED: Cooper RA. Comparison of virtual wheelchair driving performance of people with traumatic brain injury using an isometric and a conventional joystick. OBJECTIVE: To compare wheelchair driving performance in a driving simulator using a conventional joystick and an isometric joystick. DESIGN: Randomized, cohort study. SETTING: A research facility based in a hospital or in an independent living center. PARTICIPANTS: Participants (N=20; 12 men, 8 women; mean age ± SD, 30.62±10.91 y) who were at least 1 year post-TBI. INTERVENTIONS: Driving performance using an isometric joystick compared with a conventional movement joystick. MAIN OUTCOME MEASURES: Average trial completion time, and trajectory-specific measures measured orthogonal to the center of driving tasks: root mean squared error, movement offset, movement error, and number of significant changes in heading. RESULTS: After statistically controlling for driving speed, participants were able to complete the driving tasks faster with an isometric joystick than while using a conventional movement joystick. Compared with the conventional joystick, an isometric joystick used for driving forward demonstrated fewer driving errors. During reverse driving the conventional joystick performed better. CONCLUSIONS: The customizable isometric joystick seems to be a promising interface for driving a powered wheelchair for individuals with TBI.

Development of a wheelchair virtual driving environment: trials with subjects with traumatic brain injury.

OBJECTIVE: To develop and test a wheelchair virtual driving environment that can provide quantifiable measures of driving ability, offer driver training, and measure the performance of alternative controls. DESIGN: A virtual driving environment was developed. The wheelchair icon is displayed in a 2-dimensional, bird's eye view and has realistic steering and inertial properties. Eight subjects were recruited to test the virtual driving environment. They were clinically evaluated for range of motion, muscle strength, and visual field function. Driving capacity was assessed by a brief trial with an actual wheelchair. During virtual trials, subjects were seated in a stationary wheelchair; a standard motion sensing joystick (MSJ) was compared with an experimental isometric joystick by using a repeated-measures design. SETTING: Subjects made 2 laboratory visits. The first visit included clinical evaluation, tuning the isometric joystick, familiarization with virtual driving environment, and 4 driving tasks. The second visit included 40 trials with each joystick. PARTICIPANTS: Subjects (n=8; 7 men, 1 woman) with a mean age of 22.65+/-2y and traumatic brain injury, both ambulatory and nonambulatory, were recruited. INTERVENTIONS: The MSJ used factory settings. A tuning program customized the isometric joystick transfer functions during visit 1. During the second visit, subjects performed 40 trials with each joystick. MAIN OUTCOME MEASURE: The root mean square error (RMSE) was defined as the average deviation from track centerline (in meters) and speed (in m/s). RESULTS: Data analysis from the first 8 subjects showed no statistically significant differences between joysticks. RMSE averaged .12 to .21m; speed averaged .75m/s. For all tasks and joysticks, driving in reverse resulted in a higher RMSE and more virtual collisions than forward driving. RMSE rates were greater in left and right turns than straight and docking tasks. CONCLUSIONS: Testing with instrumented real wheelchairs can validate the virtual driving environment and assess whether virtual driving skills transfer to actual driving.

Force control strategies while driving electric powered wheelchairs with isometric and movement-sensing joysticks.

Innovations to control interfaces for electric powered wheelchairs (EPWs) could benefit 220000 current users and over 125000 individuals who desire mobility but cannot use a conventional motion sensing joystick (MSJ). We developed a digital isometric joystick (IJ) with sophisticated signal processing and two control functions. In a prior study, subjects' driving accuracy with our IJ was comparable to using an MSJ. However, we observed subjects using excessive force on the IJ possibly because its rigid post provides no positional feedback. Thus, this paper examines the time-series data recorded in the previous study to characterize subjects' force control strategies since weakness is a concern. Eleven EPW users with upper limb impairments drove an EPW using an IJ with two different control functions and an MSJ in a Fitts' law paradigm. Subjects relied upon positional feedback from the MSJ and used appropriate force. In contrast, subjects using the IJ with either control function applied significantly higher force than necessary (p < 0.0001 and p = 0.0058). Using higher average force was correlated with quicker trial times but not associated with accuracy. Lack of positional feedback may result in use of excess isometric force. Modifying control functions, adjusting gain, or providing additional training or feedback might address this problem.

Assessing mobility characteristics and activity levels of manual wheelchair users.

Although engaging in an active lifestyle is beneficial for maintaining quality of life, a majority of wheelchair users are inactive. This study investigated the mobility characteristics and activity levels of manual wheelchair users in the residential setting and at the National Veterans Wheelchair Games (NVWG). Demographic factors that may have influenced activity in the home environment were also identified. Fifty-two manual wheelchair users completed a brief survey, and their activity was monitored with a custom data logger over a period of 13 or 20 days. We found that they traveled a mean +/- standard deviation of 2,457.0 +/- 1,195.7 m/d at a speed of 0.79 +/- 0.19 m/s for 8.3 +/- 3.3 h/d while using their primary wheelchair in the home environment. No significant differences in mobility characteristics or activity levels were found for level of spinal cord injury or disability. We also found that subjects traveled significantly farther and faster and were active for more hours during an average day at the NVWG than in the home environment (p < 0.001). We found that manual wheelchair users who were employed covered more distance, accumulated more minutes, and traveled a greater average maximum distance between consecutive stops than those who were unemployed. Results from this study provide a better understanding of the activity levels achieved by manual wheelchair users and insight into factors that may influence this activity.

Engineering better wheelchairs to enhance community participation.

With about 2.2 million Americans currently using wheeled mobility devices, wheelchairs are frequently provided to people with impaired mobility to provide accessibility to the community. Individuals with spinal cord injuries, arthritis, balance disorders, and other conditions or diseases are typical users of wheelchairs. However, secondary injuries and wheelchair-related accidents are risks introduced by wheelchairs. Research is underway to advance wheelchair design to prevent or accommodate secondary injuries related to propulsion and transfer biomechanics, while improving safe, functional performance and accessibility to the community. This paper summarizes research and development underway aimed at enhancing safety and optimizing wheelchair design.

Advancements in power wheelchair joystick technology: Effects of isometric joysticks and signal conditioning on driving performance.

OBJECTIVE: An estimated 125,000 Americans with movement disorders that preclude independent mobility in a power wheelchair could benefit from improved control devices. We developed variable gain algorithm (VGA) software for our isometric joystick (IJ) that allows it to emulate a commercially available motion-sensing joystick (MSJ) in performance but retain the unique customizable features of an isometric control. Force sensing algorithm (FSA) software allowed the IJ to function as a simple isometric device. DESIGN: Using a Fitts' Law paradigm, we compared driving performance with floor targets using a standard MSJ and an IJ with both FSA and VGA software in 11 electric power wheelchair users with a variety of impairments. Outcome measures were reaction time (RT), movement time (MT), and driving accuracy (DA). RESULTS: The IJ with FSA had a significantly shorter RT than the MSJ (P < 0.0020). The IJ with FSA had a significantly longer MT than the MSJ to far targets (P < 0.0159). No differences were found between the IJ with VGA and the MSJ with respect to RT or MT. No differences in DA were found among any of the joysticks. CONCLUSIONS: VGA software allowed the IJ to function similarly to the MSJ with respect to RT, MT, and DA.

The development and preliminary evaluation of a training device for wheelchair users: the GAME(Wheels) system.

PURPOSE: Training of appropriate wheelchair propulsion methods may be beneficial to the individual who uses a wheelchair by reducing the incidence of pain and improving one's quality of life. This paper discusses the development and initial testing of a training device that was developed to aid in wheelchair propulsion techniques: GAME(Wheels) System. METHODS: Two separate models of GAME(Wheels) have been developed: a GAME(Wheels) Clinical and a GAME(Wheels) Trainer. Details of the development process and the refinement have been included in this manuscript. To verify and compare the practicality and functionality of the two GAME(Wheels) systems, several focus groups were conducted: first to determine whether the systems could be set-up with informational materials and second to determine if the systems could be taught to novice users. RESULTS: Results from the focus group indicate that the overall impressions of the systems were that they were 'fun' to play. Suggestions were raised to improve the design, which have been incorporated into further refinement of the GAME systems. CONCLUSIONS: This paper provides an overview of the development of a wheelchair-training device. Valuable information was gained to improve the design of the GAME(Wheels) systems.

Virtual reality and computer-enhanced training applied to wheeled mobility: an overview of work in Pittsburgh.

Some aspects of assistive technology can be enhanced by the application of virtual reality. Although virtual simulation offers a range of new possibilities, learning to navigate in a virtual environment is not equivalent to learning to navigate in the real world. Therefore, virtual reality simulation is advocated as a useful preparation for assessment and training within the physical environment. We are engaged in several efforts to develop virtual environments and devices for mobility skills assessment and training, exercise training, and environment assessment. Virtual reality offers wheelchair users a training tool in different risk-free environments without any indoor (e.g., walls, furniture, and stairs) and outdoor (e.g., curb cuts, uneven terrain, and street traffic) physical constraints. Virtual reality technology will probably become more common in the field of assistive technology, especially given the rapid expansion of gaming technology and the continued exponential growth of computing power.

A pilot study on community usage of a pushrim-activated, power-assisted wheelchair.

Manual wheelchair propulsion combined with other stresses to the upper extremities may result in secondary injury. Possible solutions would be to devise alternative methods of propulsion, such as a pushrim-activated, power-assist wheelchair (PAPAW). The goals of this study were to examine the usage of the PAPAW in a real world setting and to characterize the driving habits of manual wheelchair users. Feedback was also obtained regarding subjects' opinions with respect to the PAPAW: their likes and dislikes. A PAPAW was provided to subjects for 2 weeks. Usage (average and total distance traveled and velocity) was tracked for both the PAPAW and the subjects' own wheelchairs. Significant differences in usage were not seen between the personal wheelchairs or the PAPAW. As a result, weeks were combined to provide an overall examination of driving characteristics. The average distance traveled over an average day was 1,671.4 +/- 314.8 m with an average velocity of 0.44 +/- 0.09 m/second. This pilot study provides an idea of manual wheelchair usage in a population of individuals with spinal cord injury. The lack of significant findings between the PAPAW and the subjects' own wheelchairs may be a function of study methodology such as sample size and length of follow-up in the new wheelchair. Future studies should expand upon the pilot work completed here, strengthening the design.

Comparison of virtual and real electric powered wheelchair driving using a position sensing joystick and an isometric joystick.

There are limited interface options for electric powered wheelchairs, which results in the inability of some individuals to drive independently. In addition, the development of new interface technologies will necessitate the development of alternative training methods. This study compares a conventional position sensing joystick to a novel isometric joystick during a driving task in a virtual environment and a real environment. The results revealed that there were few differences in task completion time and root-mean-square error (RMSE) between the two types of joysticks. There were significant correlations between the RMSE in the virtual environment and the real environment for both types of joysticks. The data indicate that performance in the virtual environment was representative of driving ability in the real environment, and the isometric joystick performed comparably to the position sensing joystick.