Outline

Introduction Methods

Experimental Setup Subjects Data Collection Statistical Analysis

Results Conclusion

Introduction

Introduction

Approximately 220,000 Americans use electric powered wheelchairs (EPWs) for independent mobility.

An additional 125,000 Americans with disabilities desire power mobility but cannot functionally drive an EPW.

Introduction

Isometric joysticks (IJs) rigid post : theoretically reduces the

amount of dexterity required for control Movement sensing joysticks (MSJs)

Isometric joysticks source : http://www.wheelchairnet.org/

Introduction

Compared Human Engineering Research Laboratories (HERL) IJ with two control functions to a conventional MSJ (PML Flightlink, Ltd). Subjects : experienced EPW users

with upper limb impairments from a variety of etiologies

Introduction

Sophisticated signal processing statistically indistinguishable from the

MSJ basic control function

lower performance than using the MSJ Regardless of the control software

installed, users tended to exert more force than necessary on the IJ

Methods

Experimental Setup

Fitts’ Law The model is based on time and distance

nine circular, black vinyl targets 155 cm in diameter to the floor in a double semicircular array

Experimental Setup

Distance of targets from the starting position near targets : 305 cm far targets : 538.5 cm

Mounted one of two test joysticks to a Quickie P300 EPW (Sunrise Medical, 1994)

Experimental Setup

Force sensing algorithm (FSA) program the IJ to operate as a simple IJ

Variable gain algorithm (VGA) program the IJ to emulate an MSJ more

closely dead zone : low amplitude inputs ( 0.9

N) occurring from unintentional/resting movements produces no output

Experimental Setup

Subjects

Used an EPW with hand operated MSJ as the primary means of mobility at least 20 h per week

Ages between 18 and 80 years

Tolerate testing for 2.5 h Drive to each of nine targets three

times with each of three joystick

Subjects

Subject numbers in each diagnostic category : 4 (36.4%) with Cerebral Palsy (CP) 2 (18.2%) with traumatic brain injury (TBI) 2 (18.2%) with spinal cord injury (SCI) 1 (9.1%) with Muscular Dystrophy 1 (9.1%) with Spina Bifida (SB) 1 (9.1%) with PolioCerebral Palsy (CP) : 腦性麻痺Traumatic brain injury(TBI) :創傷性腦損傷spinal cord injury (SCI)脊髓損傷 Muscular Dystrophy :肌肉萎縮症Spina Bifida (SB) :脊柱分裂 Polio :小兒麻痺疫

Data Collection

Accuracy successful trial

halted the EPW within the target for at least 2 s

with a total trial time of no more than 40 s Driving accuracy (DA)

the percentage of successful trials completed with each joystick

Data Collection

Transducers forward and reverse

“speed” axis left and right

“direction” axis

Subjects

Data Collection

Average applied force each trial by dividing the area under the

force time curve by the total trial time Excess force

Each trial as the average of the differences between the actual applied force

control efficiency (CE) the Newton ‧ seconds (N‧s ) expended

within the operational range divided by the total N‧s of each trial

Statistical Analysis

Alpha at values equal to 0.05 a priori Used SPSS for univariate analyses and

nonparametric analyses nonparametric statistics(Friedman test)

Average applied force and trial time were not normally distributed

learning effect for average applied force subsequent trials

nonparametric statistics(Mann–Whitney tests) Determine if average applied force for each

trial was related to DA

Statistical Analysis

Spearman Rho correlations evaluate the relationship between

average applied force and trial time for successfully acquired targets

Results

Results

Average age 37.8 ± 10.9 years

Gender male : 6 (54.6%) female : 5 (45.5%)

Race Caucasian : 6 (54.6%) African-American : 4 (36.4%) Asian-American : 1(9.1%).

Results

Results

No learning effect seen for average applied forc any joystick FSA p = 0.184, VGA p = 0.117, MSJ p = 0.804

Average applied force negatively correlated with trial time for all three joysticks for successfully acquired near and far targets

Average applied force was not related to DA for any of the joysticks FSA p = 0.306, VGA p = 0.126, MSJ p = 0.304

Results

Conclusion

Conclusion

The HERL IJ is a potential alternative control interface for mobility for many individuals with disabilities.

The IJ required more force to operate than the MSJ, but subjects’ driving performance was not affected.

Thank You for Your Attention!