Powered wheelchair bucking

-Usin a d u n ~ m y test driverwit11 ;i sirn~rlatecl Naccid fi>rear.rn c;rp;rble of representing either a large or zem frictiioi~ colldition, S I X powered wheelchairs were examined fc>i,r buckir~g tendencies. In the zero friction conclition, brrcking was easily inducecl in 5 of 6 testcd wheelchairs. Addillg ltiction to the simulatccl fc>rear-m prevented bucking in ;ill lestecl wheelchairs but one. Bucking is not simply related lo wheelcl-r;rir perlormance meirsures such as speed or. acceleration. Sustained bucking corresponds to neutral stability in ti speed regulated machine. Cl-rlinges in natural frequency ar-rcl d;imping characteristics are preclicled as useful in reducirrg powered whcelch;airbucking. function can find rt drficulr and even rr~lpo\slble lo ma\ter the appr-cbprrate \kill\. lit wor~ld appear desar able lo deilign power wheelchairs so a\ lo preclude barcking. A uaeful first step an \uch a process r \ to e\labl~\la the rcdot cause of bucking. In thi.; work the plrry\ical charactern\tics of a known hck ing whee lck i r are compared lo tlro\e CPC five power wheelchair'i; selected at rancbona. AT rsilue is the pertrnence of such mechanical de\ign fiictors a, acceler;rtion, jerk, top \peed, etc., 10 bucking. METHOIOS AND MA'KERIALS The bt~cltirrg of power wheelc&~air\ define\ a Ipecr'fic control problem rn which the vel~icle jerk\ back and forth despite Ihe eh'Cort\ of the u\er to produce a ~lrr~ooth rnotlor~. While Ihi\ pr.oblem i\ rare, clinical observations indicate that the combination of certain wheelcl-rair users, dr-rvrr-ry certain nlodels of wheelG\I$\Ts, 1s Iikely to \edd to "ouckiing. In nrany wiig~s wlzeelchair buckir~g is similar to the process ob\erved when unskilled drivers attempt to accelerate automobiles eqt~ipped with mechanical In ei"cker cace, the vehicle executes a vjole1r.l: oscillation super-impo\ed rrpo1-a a basic Irajeclory. With experience, the typical arlton~obile driver develop5 \kill.nece\\ary to darnpen the unwanted o\cjlkation. However, in the caw of wheelcharr uler\, tho\e with impaired LIpper extremity A group of six power wheelchair\ were examined fcx buckln-rg tendencies and the: results compared with physical mea\urei? of acceleratiorl, jerk, anci lop speed. The one wheelchr-lir found to po\ses\ rrnacceptably poor bucking chiu-aeteristics, imd never put into productiol~, will be termed the "Xu wheelchair. Olherte\ted nlachirres include the E&J-3P, E&J-3N, Ves\a Sld, Ins&-Gaiter, and an in-house developnrent termed ""Pancake." The physical characteristics tests employed in thir work are those described in the 1979 Vcterttn,., ad mini^ tva ritrn StuncilruO,~ ,for Electric.( rlly Powtered ~ h r r / ~ ~ h ~ ~ i r s . To measure acceleration arrd jerk, 2) driver clasped a commercial servo accelerometer to his breastbone, rising both hal~ds to assure firm ancl level po\itionitlg of the sensor. From it standil~g start., ;HI assistant standine lo one 5k.k of