Harshal P. Mahajan

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, birds 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.

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.

Assessment of wheelchair driving performance in a virtual reality-based simulator

Abstract Objective To develop a virtual reality (VR)-based simulator that can assist clinicians in performing standardized wheelchair driving assessments. Design A completely within-subjects repeated measures design. Methods Participants drove their wheelchairs along a virtual driving circuit modeled after the Power Mobility Road Test (PMRT) and in a hallway with decreasing width. The virtual simulator was displayed on computer screen and VR screens and participants interacted with it using a set of instrumented rollers and a wheelchair joystick. Driving performances of participants were estimated and compared using quantitative metrics from the simulator. Qualitative ratings from two experienced clinicians were used to estimate intra- and inter-rater reliability. Results Ten regular wheelchair users (seven men, three women; mean age ± SD, 39.5 ± 15.39 years) participated. The virtual PMRT scores from the two clinicians show high inter-rater reliability (78–90%) and high intra-rater reliability (71–90%) for all test conditions. More research is required to explore user preferences and effectiveness of the two control methods (rollers and mathematical model) and the display screens. Conclusions The virtual driving simulator seems to be a promising tool for wheelchair driving assessment that clinicians can use to supplement their real-world evaluations.

Virtual electric power wheelchair driving performance of individuals with spastic cerebral palsy.

ObjectiveUpper limb spasticity may impair the use of control interfaces such as joysticks for many individuals with disabilities such as cerebral palsy (CP). The aims of this study were to compare the driving performance of those with CP to that of control participants, to identify the impact of lead time on performance, and to compare two joystick designs, a standard movement sensing joystick and a novel isometric joystick. DesignThis study used a repeated-measures design to compare the performance of a group of participants with CP to that of participants without disabilities in a two-dimensional simulated driving task on a computer screen using the two control interfaces. The driving trials used varying “lead times,” or the amount of warning time available to make movement decisions and turns. A total of 34 participants with CP and without disability were matched by age and sex into two groups. ResultsParticipants with CP had lower driving performance in most variables of interest compared with controls. However, surprisingly, reducing lead time also reduced some performance errors, possibly because of more deliberate driving. The isometric joystick outperformed the movement sensing joystick in terms of performance errors but contributed to a prolonged reaction time. ConclusionsThe isometric joystick was preferred by participants over the movement sensing joystick in this study and may be a future alternative for individuals with CP for both power mobility and computer access tasks.

Tuning algorithms for control interfaces for users with upper-limb impairments.

Objective: Approximately 40% of Americans with disabilities cannot operate wheeled mobility devices and computers adequately because of diminished upper-limb motor control, sensory limitations, and cognitive impairments. We developed tuning software that can customize control interfaces for individuals with upper-limb impairments. This study compared the differences in each parameter among different diagnostic groups. Design: The age of the subjects ranged from 18 to 80 yrs. The participants were classified into the following groups: athetoid cerebral palsy, spastic cerebral palsy, multiple sclerosis, upper-limb spasticity, and control. We used a validated tuning software protocol to customize an isometric joystick before a virtual tracing or driving task. Tuning parameters were then compared across groups. Results: Seventy-five subjects were included. Gain, the parameter responsible for force-to-output ratios, in each directional axis (leftward gain: P = 0.018; rightward gain: P = 0.003; reverse gain: P = 0.007; forward gain: P = 0.014) was significantly different across the diagnostic groups. Post hoc analyses showed that the control group required smaller leftward gain than spastic cerebral palsy, multiple sclerosis and upper-limb spasticity groups and smaller gain in all other directions compared with spastic cerebral palsy. Conclusions: Gain may be a useful parameter in tuning by clinicians, and efforts aimed at gain customization may aid the development of commercially available tuning software packages.

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.

Advanced Joystick Algorithms for Computer Access Tasks

To compare 2 correction algorithms and 2 joysticks (a conventional movement‐sensing joystick and a custom‐designed isometric joystick) in computer access tasks.

The feasibility of an automatic prompting system in assisting people with traumatic brain injury in cooking tasks

Abstract Purpose: Individuals with traumatic brain injury (TBI) often experience difficulties in performing kitchen-related sequencing tasks due to cognitive deficits. The primary aim of this study is to examine the feasibility of a context-aware automatic prompting system in assisting individuals with TBI in multi-step cooking tasks. Method: Sixteen individuals with TBI participated in the study. A randomized cross-over design was used to compare the automatic prompting method with a conventional user-controlled method through a tablet device. Participant performance under each prompting method was assessed using the Performance Assessment of Self-Care Skills in terms of independence, safety, and adequacy. Subjective workload and qualitative feedback were also collected. Results: The automatic method, when compared with the user-controlled method, significantly decreased the amount of external assistance required by participants, received higher ratings in user perceived ease-of-use, and was considered less stressful for participants. However, the user-controlled method showed strengths in offering participants more flexibility in terms of controlling on the timing of prompts. Conclusions: The results provided insight into the potential benefits and user perceptions of a context-aware prompting system. The information could contribute to the future development of advanced prompting technology for people with cognitive impairments in completing sequential tasks. Implications for Rehabilitation For people with traumatic brain injury, the context-aware prompting method showed advantages in improving user performance, receiving better ratings on ease-of-use, and decreasing stress levels, compared to the user-controlled prompting method in completing multi-step cooking tasks. Future prompting systems for people with cognitive impairments may allow users to control the pace of prompting and use sensing information as back-up assistance in critical situations. In this way, the system may help users monitor their actions and offer confirmations, especially at steps with safety concerns, thus enhancing the sense of security and reducing the stress from self-monitoring.

Cueing kitchen: A smart cooking assistant

Due to problems with attention, cognition, memory, and executive functions people with Cognitive Impairments face difficulties in independently completing certain instrumental activities of daily living such as meal preparation. The purpose of this research study was to understand specific problems people with cognitive impairments face in their activities around their kitchen, specifically focusing on meal preparation tasks. Ethnographic interviews were conducted with people with Traumatic Brain Injury and specific unmet needs were identified. The Smart Cueing Kitchen, a cognitive orthosis with advanced sensing and prompting tools was designed to satisfy some of these unmet needs. This paper reports the design rationale for deployment of different system technologies in the kitchen and proposed future developments are discussed.

Comparison of Two Prompting Methods in Guiding People with Traumatic Brain Injury in Cooking Tasks

This study aims to examine the effectiveness of two prompting methods (i.e., a paper-based method vs a step-by-step user-controlled method on an iPad mini) in guiding individuals with traumatic brain injury (TBI) through the cooking tasks. Eight individuals with traumatic brain injury participated in this study. They were asked to prepare two meals in their home kitchens following the guidance of the two methods, respectively. Their performance were evaluated using the Performance Assessment of Self-Care Skills (PASS) tool. The perceived ease-of-use, usefulness, and cognitive loads of the two prompting methods were assessed using a custom questionnaire. In addition, problems of participants in completing the cooking tasks with both prompting methods were categorized. Results showed that four participants completed cooking tasks more independently with the user-controlled prompting method and most participants preferred the user-controlled method to paper-based prompting. Recommendations for future development of prompting methods were also discussed.