CLINICAL EVALUATION OF A WHEELCHAIR MOUNTED ROBOTIC ARM

E. Chaves, B.S., A.M. Koontz, Ph.D., S. Garber, MA, OTR., R.A. Cooper, Ph.D., A.L. Williams, M.S,
Departments of Rehabilitation Science & Technology, University of Pittsburgh,
Human Engineering Research Laboratories, VA Pittsburgh Healthcare System
Houston VA Medical Center

ABSTRACT

The purpose of this study was to determine if functional independence and ability to perform basic tasks could be improved with the use of a wheelchair mounted robotic arm. Level of independence with and without the device was recorded on 16 basic activities for eleven participants with tetraplegia. Participants were timed in their ability to complete the tasks with the robotic arm prior to and after several comprehensive training and practice sessions. Significant improvement in task independence as well as time it took to complete tasks was discovered in 7 activities. Current research on robotic technology is essential to encourage further advancement and the development of useful and practical robotic devices.

BACKGROUND

Being able to independently perform all activities of daily living (ADL) is desired by a large number of individuals with a cervical spinal cord injury (SCI). The use of robotic technology in the rehabilitation of individuals with disabilities is in its initial stage and has demonstrated some promise in assisting individuals with SCI achieve independence [1][2]. Although the application of robotic technology for aiding with ADLs is not widespread, it has the potential to augment a person's manipulation skills. As such, these devices can lead to improved independence (reduced need of attendant care), enhanced self-esteem, increased mental stimulation, and improved interaction and control over the physical environment [1][2]. Currently, a robotic arm can be installed on a fixed workstation [3], mounted on a mobile platform [4] or attached to a wheelchair. The latter, known as wheelchair mounted robotic arm (WMRA), offers the possibility for individuals with severe disabilities to manage tasks in different environments [4]. Current research on robotic technology is essential to encourage further advancement and the development of useful and practical robotic devices. The overall aim of this study was to evaluate a WMRA in improving the functional independence of persons with cervical SCI. The first specific aim of this study was to determine the changes in independence level during ADLs with WMRA usage. It was hypothesized that independence level would improve with WMRA usage during all tested activities. The second specific aim was to determine the impact of WMRA training and practice on the time taken to perform the ADLs. It was hypothesized that after training and practice, participant's time to perform all proposed activities with the WMRA would decrease.

METHODS

Wheelchair Mounted Robotic Arm (WMRA): The WMRA used in the study was developed by Rehabilitation Technologies Division of the Applied Resources Corp. [fig.1]. The WMRA has four degrees of freedom. The shoulder facilitates forward/backward and rotational movement. The elbow provides flexion and extension motion and allows the user to extend the arm forward a maximum of 48 inches. The wrist enables the user to rotate the unit's integral grippers into the correct position to pick up objects. The two-fingered gripper can be opened or closed. The WMRA can be mounted on either side of most power wheelchairs. While the WMRA can be operated using a standard switch-based input device, such as a joystick, keypad or sip-n-puff, only the joystick device was available for this study. Subjects: Eleven men with cervical SCI provided informed consent. The subject sample included the following levels of injury: one had 3-4, five had 4-5, four had 5-6 and one had 6-7. The average age of the participants was 42 (± 12) years. All subjects used a power wheelchair for mobility controlled via a joystick. Protocol: Subjects were asked to complete 20 hours of evaluation and training over 10 visits. At the beginning of the study, subjects were asked to complete 16 tasks without the WMRA. The 16 activities are listed in Table 1 and represent basic ADLs. For each task, the subject was classified as dependent (0), needs assistance (1), or independent (2). Next, the WMRA was installed on the subject's wheelchair. After a brief orientation to the WMRA, subjects were asked to complete the 16 marker tasks using the WMRA while the time to complete each task was recorded with a stopwatch in seconds. Also subjects were again evaluated for each task as either dependent, needs assistance, or independent with the WMRA. The last phase of data collection involved recording the time to complete the same tasks using the WMRA after receiving approximately 13 hours of training and practice. Statistical Analysis: Statistical analysis was completed using SPSS software (SPSS, Inc.). The difference in the independence level with and without the use of the WMRA was examined for each task using a Wilcoxon matched-pairs test. Difference in time to complete the ADL task before and after training was analyzed using the Wilcoxon test and paired t-test. A Wilcoxon test was used for data that did not meet the normality assumption, whereas a paired t-test was used for normally distributed data. The significance level was set at 0.05.

RESULTS

The data revealed significant differences in the subjects' ability to improve independence with the WMRA in 7 of the 16 activities (Table 1; p<0.05). Time to complete the ADL activities before and after training and practice is shown in Table 2. Subject's time to complete tasks improved for 7 activities.

TABLE 1: List of 16 basic activities. Number of subjects with a particular level of independence for each task is shown along with significance level.

Activities	Dependent (Number subject)		Needs assistance (Number subject)		Independent (Number subject)		Sig
	w/o	WMRA	w/o	WMRA	w/o	WMRA	P
1. Poor liquids from pitcher into a cup.	5	0	0	1	6	10	.034
2. Drink from a cup.	4	0	1	1	6	10	.038
3. Pick up straw from floor.	8	0	0	1	3	10	.007
4. Pick up keys from the floor.	6	0	0	1	5	10	.020
5. Access refrigerator (open door, take pitcher, place it on table and close door).	3	0	7	6	1	5	.003
6. Retrieve towel and take to lap tray.	0	0	1	0	10	11	.317
7.Remove objects cabinet (open door, remove objects, close door)	4	1	4	6	3	4	.234
8.Open/close drawer.	1	0	0	0	10	11	.317
9. Operate wall switch.	0	0	0	0	11	11	1.000
10. Bring can from low surface to lap tray.	5	0	1	2	5	9	.024
11. Bring plate with a cookie from low surface to lap tray.	5	1	1	4	5	6	.059
12. Retrieve book (remove book from shelf and place it on table).	2	0	0	1	9	10	.180
13. *Access telephone (pick up receiver, put it next to ear and hang up receiver).	2	0	0	1	9	9	.005
14. Eat cookie (pick up cookie from a plate, bring cookie closer mouth and put cookie back on plate).	2	0	1	1	8	10	.157
15. Take utensils (retrieve utensils from a box and put on lap tray).	1	1	1	1	9	9	1.000
16. * Operate toaster (pick up bread slice from plate, insert in toaster, depress bottom, remove toast and place on plate) .	4	1	1	4	4	4	.317
* Note: Data were missing or not recorded for one subject in task 13 and two subjects in task 16.

Table 2: Subject’s time performance before and after training and practice with WMRA. Significant differences are denoted with a star. Numbered activities correspond to those in table 1.

Figure 1

DISCUSSION

The data shows significant improvement in task independence in 7 of the 16 activities (table 1). Tasks involving picking an item up from the floor, reaching for items (in a refrigerator and on a low surface), and object manipulation (drinking, pouring liquids, phone) showed the greatest increases in level of independence when the WMRA was used. In most of the tasks where no improvement was achieved, the subjects were independent with and without the WMRA (e.g., operate wall switch, open/close drawer). Thus, these ADL tasks were already manageable given their ability level. It is also important to point out that small improvements in task independence were seen in activities that required advanced motor planning skills and several steps to complete (e.g., remove object from a cabinet and operate the toaster). Subjects became more proficient in WMRA use with 13 hours of training/practice for over half of the ADL activities. While we expected to find significant time differences for all activities, it is possible that the amount of WMRA training and practice was insufficient for several of the subjects in the sample. Time to complete a task will decrease with more training, as the user becomes accustomed to the input device and the robotic arm [5]. The second possibility may be that the WMRA switch-based joystick did not match the subject's motor skills. Several users' had difficulty using the joystick and sometimes had to focus more on how to control the robot rather than on the task at hand. For future studies, the use of a WMRA with proportional and position dependent speed control (allows for fast coarse movements and slow fine movements) and a variety of input devices (e.g., head control, sip-n-puff, etc.) might make its operation more intuitive and may have a better effect on the subjects' performance time as well as task independence. Further study investigating the number of hours of training and practice needed to master each task (given the individual's motor planning skills) would be helpful. Studying a larger number of individuals with a greater degree of physical impairment may provide greater insight into the benefit of the WMRA.

REFERENCES

ACKNOWLEDGEMENTS

This study was supported by VA Rehabilitation R&D Services, Project # B2311-T.

Eliana Chaves
7180 Highland Drive building 4
2nd floor, East Wing, 151R-1
Pittsburgh, PA, 15206.
Ph: (412) 365-4850
e-mail: esc14@pitt.edu