Field Usability Testing of a robotic wheelchair with passive-active suspension for seat stability in uneven terrains

At present, existing Electric Powered Wheelchairs (EPWs) are limited primarily to use indoors
and outdoors with ADA compliant surfaces. EPW users are often exposed to irregular surfaces
that include inclined surface (i.e., slopes and, curb-ramps) and/or surfaces with ground changes
(i. e. sidewalks, curb drops, speed-bumps, cobblestones). Attempting to drive over such surfaces
may cause loss of stability due to wheelchair limitations and user’s limited spatial awareness.
Further, surfaces with architectural barriers such as blocked curb-ramps or in bad condition may
constrain wheelchair user from accessing sidewalks, limiting their participation in the community.
The Mobility Enhancement Robotic (MEBot) EPW was developed to reduce the risk of tips and
falls when facing these challenging terrains through advanced mobility applications. During the
CDA-1, MEBot was re-designed with a passive-active actuation and suspension (MEBot-PAAS)
system to offer a faster and reliable response to maintain stability on inclined surfaces (Grant
#A3076-M) compared to commercial EPWs and its previous iteration. While stability was
successful, it was noted that its seat orientation significantly changed during sudden changes in
the surface. Driving on surfaces with significant ground changes (e.g., sidewalk cracks, curb
drops, potholes) may cause MEBot-PAAS to roll-over. Therefore, this CDA-2 proposes to Aim 1)
implement MEBot-PAAS capabilities to traverse irregular surfaces (not addressed in the CDA-1)
while maintaining stability. Further, Aim 2) will identify its features and clinical limits of use by a
group of stakeholders. Aim 3) will evaluate the usability of MEBot-PAAS with Veterans with
disabilities in real-world environments to achieve technology readiness to bring it to Veterans.
Aim 1 (Year 1-2): Implementation and evaluation of MEBot-PAAS applications (self-leveling and
step negotiation) to navigate on irregular surfaces. Aim will be conducted in three phases:
Phase 1: Perform engineering changes for implementation of MEBot-PAAS applications:
• Develop a dynamic model to reduce Center of Pressure displacement and maintain stability
• Incorporate depth sensors for surface characterization and speed limitation ahead of surfaces.
• Implement legged-wheel motion to navigate surfaces with significant ground changes.
Phase 2: Engineering analysis will evaluate the implemented MEBot-PAAS applications using a
‘rescue dummy’ on controlled irregular surfaces to meet Phase 1 design criteria.
Phase 3: Evaluate the performance of MEBot-PASS compared to MEBot-nPAAS (applications
de-activated) on controlled irregular surfaces. MEBot-nPAAS will simulate conventional EPWs.
We hypothesize that: H1a. MEBot-PAAS will show less center of pressure displacement and H1b.
less seat angle variation than MEBot-nPAAS. H1c. A significant difference in vibration levels will
be observed between MEBots. Also, participants will report H1d. less lean amplitude, H1e. higher
usability and less discomfort scores with MEBot-PAAS compared to MEBot-nPAAS.
Aim 2 (Year 3). Identify MEBot-PAAS benefits and limitations following the Clinical Limits of Use
Tools (CLOUT). These tools include wheelchair standards and stakeholders’ feedback.
Aim 3 (Year 4). Field usability evaluation of MEBot-PAAS in outdoor environments. We
hypothesize that H3a. MEBot-PAAS will show less seat angle variation and vibration levels in
comparison to participants’ own EPWs. H3b. Participants will report significantly less lean
amplitude (safety perception), higher usability, less discomfort, and lower task load demand when
using MEBot-PAAS in comparison to their own EPWs

Grant Number: 5IK2RX003806-04
NIH Institute/Center: VA
Principal Investigator: Jorge Candiotti