TASK: PM-6 NEW CONCEPTS IN POWERED INDOOR MOBILITY

Transcription

1 TASK: PM-6 NEW CONCEPTS IN POWERED INDOOR MOBILITY Investigators: Douglas Hobson, Linda van Roosmalen Collaborators: Jules Legal, Steve Stadelmeier Rationale Very few powered wheelchairs have been optimized for activities conducted in tight indoor environments. Reaching up and down, transferring and maneuvering in confined spaces are examples of these activities. Many older persons with disabilities have need for such mobility products, but will often reject the notion if it makes a statement about their disability. Aesthetics is an important component to acceptance and, therefore, it was given high priority in this task. Goals 1. To provide increased indoor powered mobility options for consumers of all ages and disabilities with emphasis on environments of older persons. 2. Refine commercially promising designs and facilitate transfer to the marketplace. Methods Summary The PM2 Advanced Mechanisms task addressed the wheelchair steering problem by using a mathematically designed cam and linkage steering arrangement. This task addressed the need for increased indoor maneuverability by using two software-controlled servo-steering motors to control the position of the two front drive motors. A prototype, termed the PM6-MKI was developed which also featured a novel tiller-type joystick control. The software algorithm compensates for the difference in turning radius of the two front driving wheels and thereby minimizes any wheel scrubbing effect. (Figure 11). The front wheel drive motors used in the prototype were Fracmo, Model: M453-W30, previously developed by Legal and Hobson. First stage comparative maneuverability testing was done using existing powered wheelchairs typically used indoors as the benchmark. A second design, the MKII, which grew out of our relationship with the students and faculty in the Design Department at Carnegie Mellon University, is shown in Figure 12. The Quality Function Deployment (QFD) [Jacques et al., 1994; Logan & Radcliffe, 1997] tool was used to establish the design criteria. This prototype addresses the need for improved esthetics and self-adjustability of seat height and angulation. Re-cycled motor drives combined with a standard controller were used to power the prototype. Two linear actuators control the height and inclination of the seat. The task plan called for the combining of the best features of each prototype into a final demonstration product. The full implementation of this plan was dependent on the availability of a new motor drive system, which was the focus of MK I prototype and task PM-1d. In spite of several efforts at working directly with motor drive manufacturers, we were unsuccessful in convincing a company to invest resources in a newly configured motor drive system. Illustrations of the MK I and MK II designs follow. Figure 11 PM6-MK I Evaluation Prototype TILLER-TYPE CONTROL STEERING MOTOR POWEREDSTEERING 18 RERC ON WHEELCHAIR TECHNOLOGY

2 Concept illustration based on QFD criteria Working Prototype Figure 12 - MK II Prototype Figure 13 - Corridor Figure 14 - Bathroom FINAL REPORT:

3 TEST WHEELCHAIR DATA Wheelchair Powered by Front wheel type Footprint MK I Powered front wheels Steered powered wheels 80 x56 cm Quickie P190 Powered rear wheels Swivel caster 107 x 61 cm E&J Tempest Powered rear wheels Swivel caster 94 x 65 cm Outcomes Summary a) Laboratory Feasibility Testing of the PM-6 (MK I) Prototype The purpose of the feasibility test was to compare the maneuverability of the MK I prototype to that of production wheelchairs designed for similar usage. Two production wheelchairs, Quickie P190 and the E&J Tempest, were selected for the tests. The tests consisted of running the three wheelchairs through three typical environmental spaces setup as a laboratory test course. Each space was laid out according to the dimensions of the Uniform Federal Accessibility Standards. The course setup consisted of the following three spaces as shown in figures below. The dimensions of the test spaces are as follows: Corridor: w=91.7 cm; Bathroom: w x d=152.3 x 142 cm; Elevator: w x d= x cm Walls for each space were fabricated from replaceable 3/4 thick polystyrene foam sheets, which showed damage marks each time they were contacted by a wheelchair. Figure 15 - Elevator Test Method The MK I, Quickie P190 and the Tempest wheelchairs were randomly assigned to 4 test subjects, all non-experienced wheelchair users. The subjects were all given the same time to become familiar with the standardized test course. They were then asked to maneuver through the test course, twice with each wheelchair. Time was measured for each wheelchair to maneuver through each space. The time started when the front feet of the test wheelchair passed the space Figure 16 - Overview of the complete course layout. The lines indicate the required maneuvers. threshold line. The time was stopped when the wheelchair exited past the space threshold line. Also, within each space the number of hits with the course wall was recorded. The first space, the corridor, was entered in a forward direction. The subject had to first steer the 20 RERC ON WHEELCHAIR TECHNOLOGY

4 wheelchair into the right corridor and proceed until they could touch a designated point on the wall with their hands. They then backed down the corridor until they could turn right and exit through the entrance corridor. The bathroom space had to be entered in a forward direction. An object on the simulated vanity was touched. The subject then backed out of the bathroom. The elevator space was approached in a forward direction. The subject then turned 180 degrees and touched the simulated control buttons for the elevator. The subject then exited the elevator forward facing. Results The test results were analyzed in such a way that the maximum speed of each wheelchair did not influence the outcome of the test. The sample results of the tests are shown in the following graphs. The first two graphs are for a single subject; the last two are the averages for all subjects. The graphs indicate that in most cases the PM6 - MK I wheelchair resulted in the shortest test time and the least number of inadvertent walls impacts. Little difference was seen in the time needed for the washroom test. The reason for this may be that the overall maneuvering requirements of the space were not extensive. Whereas, in the corridor test, most subjects took substantially longer to maneuver with the Tempest and the Quickie wheelchairs than with the MK I wheelchair. Finally, the elevator test was a time consuming task for all three wheelchairs. In terms of wall impacts, the graphs indicate that the PM6-MKI wheelchair clearly performed better then the other two test wheelchairs Average Test Time 1 PM-6: 4.48m2 Tempest: 6.11m2 Quickie P190: 6.53m2 Average time (sec) Corridor Elevator Washroom Figure 17 - Average test time of subject #1 per space for the three test wheelchairs FINAL REPORT:

5 9 8 7 Amount of Hits per W/C 1 PM-6: 4.48m2 Tempest: 6.11m2 Quickie P190: 6.53m2 Average amount of hits (n) Figure 18 - Average number of wall impacts by subject #1 for each test wheelchair 14 Average Number of Hits Number of hits (n) Corridor Elevator PM-6: 4.48m Tempest: 6.11m Quickie P190: 6.53m Figure 19 - Average number of wall impacts for all subjects for the three wheelchairs/spaces 22 RERC ON WHEELCHAIR TECHNOLOGY

6 45.0 Average Test Time Time (sec) Corridor Elevator Washroom PM-6: 4.48m Tempest: 6.11m Quickie P190: 6.53m Figure 20 - Average test time for all subjects for the three wheelchairs/spaces Discussion All wheelchairs used in the tests had different footprints, the MK I being the smallest. Therefore, direct comparisons and any conclusions from the results must be done with caution. For example, reduction in the footprint size of the production wheelchairs to that equal to the MK I wheelchair would most likely improve their wall impact performance. Also, the difference in maneuverability times could be effected by the larger footprint size of the production wheelchairs and not be totally due to the enhanced maneuverability of the MK I prototype. The Tempest and Quickie wheelchairs have front swivel casters, which makes it impossible to maneuver backwards from a forward maneuver without first causing a lateral shift of the front end of the wheelchair. This was, in some cases, the reason for higher number of wall impacts of the production wheelchairs. Whereas, the MK I wheelchair, having powered steering of the front wheels, does not exhibit lateral shifting when reversing course. Finally, because of the small size of the test sample, no statistical analysis was attempted. Therefore, it is only an observational conclusion that can be drawn from this simplified feasibility test. FINAL REPORT: As mentioned, the MK I design also features a uniquely designed tiller-type joystick. The idea is that most elderly people will intuitively relate better to tiller control (side to side movement to steer up and down for reverse and forward, respectively). Also, the direction of the tiller could be coupled electronically to the direction of the steered wheels, so at start-up there would be no directional surprises. Although this joystick design worked well during the tests, no comparative tests with the conventional joystick were possible. b) Development of the MK II Design In brief, the purpose of the MK II design was to explore the following criteria for an indoor wheelchair that would provide: an alternative to the scooter for indoor/home use, an economic way to give elderly people mobility in institutional settings, an alternative for the indoor/outdoor for home to office use, an alternative for ADA accessibility into tight workspaces, offices,

7 Figure 21 - Seat raises and tilts to aid in standing. Foot rests drops to floor. a better way to vary the sitting height of a person in a W/C, and a more esthetic and less stigmatizing way of providing powered mobility. Focus groups, user surveys and the Quality Function Deployment (QFD) tools and the MK I experience were used to explore questions and solicit concepts leading to a list of weighted design criteria. A sample questionnaire containing comments from wheelchair users can be reviewed in Appendix A. The summary results of the QFD analysis are also contained in Appendix A. The MK II prototype shown in figures resulted from these intensive planning efforts. The working prototype embodies the following key features: a nontraditional frame and elevating/tilting seat system, a ergonomically designed seat with swing up armrests for ease of transfer, powered front wheels, castered rear wheels allowing increased maneuverability in tight indoor spaces. (Steered front wheels were planned but suitable units were not possible to obtain for the prototype construction), miniature integrated joystick control, interchangeable between left and right armrests, and a non wheelchair-like appearance intended to minimize the stigma of disability. The Mark II design was featured at the 1998 RESNA Conference exhibit. Interest was demonstrated by clinicians, wheelchair users and two prospective wheelchair manufacturers. Below are several photos showing some of the features of the MK II design. Recommended Future Development Figure 22 - Arm rests flip back to aid in transfer and work place access. Given that both demonstration outcomes were basically positive, this development now requires significant resources to integrate the best of the demonstrated MK I & II features, complete with a newly developed motor drive system. It will require the formation of a partnership between the developers, and, at least, a committed wheelchair 24 RERC ON WHEELCHAIR TECHNOLOGY

8 manufacturer and motor/drive developer-supplier to transition the development towards commercial availability. The investigators have made plans for the formation of such a partnership and an SBIR submission is under preparation to help finance the venture. Assuming success with the SBIR submission, the plan calls for the development of an integrated MK III design. The MK III will then be subjected to more rigorous laboratory and user testing as part of its Phase I feasible evaluation. Publications (in preparation) References Jacques GE, Ryan S, Naumann S, Milner M, Cleghorn WL Application of Quality Function Deployment in Rehabilitation Engineering, IEEE Transactions on Rehabilitation Engineering, Vol. 2, No. 3, September Logan GD, Radcliffe DF Potential for use of quality matrix technique in rehabilitation engineering. IEEE Transactions on Rehabilitation Engineering, Vol. 5, No. 1, March Brown PG, QFD: Echoing the voice of the customer, AT&T Technical Journal, March/April, 1991, pp Hauser JR, Clausing D The house of quality, The Product Development Challenge, Harvard Business Review Book, eds. Kim B. Clark and Steven C. Wheelwright, pp , FINAL REPORT: