mathias wellner

At last! 1.5 years after star­ting to write, the arti­cle Eva­lua­tion of Visual and Auditory Feed­back in Vir­tual Obst­a­cle Wal­king has been publis­hed by Pre­sence. This is the final step, now it’s really over. I hope that my next publi­ca­ti­ons will go a little bit smoo­ther, but you never know what review­ers you get.

Aut­hors: Mathias Well­ner, ­Audrey Schau­fel­ber­ger,­ Joa­chim v. Zit­ze­witz, Robert Riener

Title: Eva­lua­tion of Visual and Auditory Feed­back in Vir­tual Obst­a­cle Walking

Jour­nal: Pre­sence: Tele­ope­ra­tors and Vir­tual Environments

Abstract: This paper descri­bes eva­lua­tion expe­ri­ments for visual and auditory feed­back in a vir­tual obst­a­cle wal­king sce­na­rio. Two stu­dies with healthy sub­jects were car­ried out using the actua­ted gait ortho­sis Loko­mat. Con­trol­led fac­tors for the visual feed­back expe­ri­ment were three dif­fe­rent per­spec­tives and 2D/​3D vision. In the auditory feed­back expe­ri­ment, con­trol­led fac­tors were rhyth­mic dis­tance feed­back and gra­dual foot cle­arance feed­back. For the visual and auditory feed­back expe­ri­ments, out­come was asses­sed with task-​​specific per­for­mance para­me­ters and ques­ti­onn­ai­res. Results for visual feed­back indi­cate that the cho­sen side per­spec­tive is supe­rior to behind and ego per­spec­tives. It is also shown that 3D vision does not reduce the num­ber of obst­a­cle hits com­pa­red to 2D vision. Fur­ther­more, it is demons­tra­ted that adding con­ti­nuous auditory feed­back made sub­jects walk fas­ter com­pa­red to the exclu­sive use of visual feed­back. Sub­jects rated auditory dis­tance feed­back as more hel­pful than auditory foot cle­arance feed­back. The­re­fore, we sug­gest using side per­spec­tive and auditory feed­back on obst­a­cle distance.

The next publi­ca­tion is alre­ady in the queue and will tar­get one study with the M3 rowing simu­la­tor.

Im Januar star­tete das auf drei Jahre ange­legte EU-​​MIMICS-​​Projekt. Unsere Gruppe über­nimmt dabei die Koor­di­na­tion. Ich selbst bin nicht direkt daran betei­ligt, jedoch über­lap­pen sich die The­men mei­ner For­schung mit denen des Pro­jekts beträchtlich.

In bei­den Pro­jek­ten geht es um die Erfas­sung des psy­cho­lo­gi­schen Zustan­des mit phy­sio­lo­gi­schen und kine­ma­ti­schen Mess­da­ten. Zum Glück ist mein Ziel etwas weni­ger ambi­tio­niert, ich hoffe auf eine emo­tio­nale Reak­tion der Rude­rer auf das vir­tu­elle Publi­kum. Im EU-​​Projekt muss sich dann das Sze­na­rio auch noch gemäß dem Pati­en­ten­zu­stand anpas­sen. Außer­dem sind die dafür vor­ge­se­he­nen Schlag­an­fall­pa­ti­en­ten nicht ganz unpro­ble­ma­tisch, weil sie doch viel grö­ßere Schwan­kun­gen auf­wei­sen als gesunde Probanden.

Im ETH-​​Hausblatt ETH Life erschien heute zum Thema der Arti­kel Wenn der Robo­ter den Pati­en­ten moti­viert. Wei­ter unten gibt es noch ein lus­ti­ges Video, wel­ches im Zuge einer von mir mit betreu­ten Semes­ter­ar­beit ent­stand. Es zeigt eine erste Fas­sung des Hin­der­nis­sze­na­rios für den Lokomat.

Die grosse Rele­vanz von Neu­roreha­bi­li­ta­tion zeigte sich in der Orga­ni­sa­tion der Brain­fair 2007 in Zürich. Die Erf­öff­nungs­rede von Jürg Kes­sel­ring han­delte dem­ent­spre­chend von den immen­sen Fähig­kei­ten unse­res Gehirns zu ler­nen. Inter­es­san­ter­weise ver­wen­de­ten die Redak­teure ein Lokomat-​​Bild, auf dem auch ich teil­weise zu sehen bin. Es ent­stand bei einem frü­he­ren Bei­trag zum Thema Loko­lift.

Today the second Loko­mat Sym­po­sium fea­tured the main talks regar­ding the Loko­mat actua­ted gait ortho­sis. Actually the main sci­en­tists were all joi­ned to pre­sent their latest rese­arch. To give you a short impres­sion I will list the talks.

I did not have a talk but was invol­ved in some lab demos of the vir­tual environ­ment exten­sion of the Loko­mat and the addi­tio­nal degrees of free­dom (Gait3D). The audi­ence was really impres­sed and espe­cially for child­ren the vir­tual rea­lity enhan­ce­ment trig­ge­red wild interest.

One of the first steps I had to take was under­stan­ding human gait. The arti­cle (biblio­gra­phic infor­ma­tion) descri­bes very ela­bo­rate model­ling tech­ni­ques in order to make a mecha­ni­cal gait ortho­sis walk. I would like to empha­size that th Loko­mat is not inten­ded to make pati­ents walk around, so it’s a dif­fe­rence to the device men­tio­ned in the arti­cle. But the gene­ral mecha­nisms are com­pa­ra­ble, espe­cially using tor­ques to make the pati­ent take a step.

Abstract — The pur­pose of this study was to examine a hybrid ortho­sis sys­tem (HOS) for wal­king after spinal-​​cord injury (SCI) that coor­di­na­tes the mecha­ni­cal locking and unlo­cking of knee and ankle joints of a recipro­ca­ting gait ortho­sis (RGO), while pro­pul­sive forces are injec­ted and unlo­cked joints con­trol­led with func­tio­nal neu­ro­mus­cu­lar sti­mu­la­tion (FNS). The likely effec­tiv­en­ess of the HOS in terms of for­ward pro­gres­sion, sta­bi­lity, and pos­ture of para­ple­gic gait was deter­mined in this simu­la­tion study. A three-​​dimensional com­pu­ter model of a HOS com­bi­ning FNS with an RGO incor­po­ra­ting feed­back con­trol of mus­cle activa­tion and joint locking was deve­l­o­ped. An anthro­po­mor­phic human model inclu­ded pas­sive joint moments and a foot-​​ground con­tact model adap­ted from other stu­dies. A model of the RGO recipro­cally cou­pled the hips and locked and unlo­cked the knee and ankle joints during stance and swing respec­tively. The actions of mus­cles under FNS activa­tion were mode­led via closed-​​loop con­trol of joint tor­que inputs. A wal­king aid that mimi­cked canes and volun­tary upper extre­mity actions main­tai­ned late­ral sta­bi­lity by pro­vi­ding the necessary shoul­der forces and moments. The simu­la­ted HOS achie­ved gait speeds of 0.51/spl plusmn/0.03 m/​s, stride lengths of 0.85/spl plusmn/0.04 m, and caden­ces of 72/​spl plusmn/​4 steps/​min, excee­ding the repor­ted per­for­mance of other assis­tive gait sys­tems. Alt­hough mini­mal for­ward trunk tilt was found to be necessary during spe­ci­fic pha­ses of gait, pos­ture, and sta­bi­lity were signi­fi­cantly impro­ved over FNS-​​only systems.