Control ofaRegenerative Braking PoweredAnkleFootOrthosis

Wearable robotic systems canbeusedtoassist people suffering paralysis fromstroke. Thispaperpresents the mechanical design, electronics andcontrol structure ofa Powered AnkleFootOrthosis forstroke survivors walking ona treadmill. Themechanical structure consists ofa powered orthosis using arobotic tendon thatusesamotortocorrectly position atunedspring inthegaitpattern. Duringthegait cycle, therobotic tendonregenerates spring energy anduses thatenergy inordertoassist thesubject inpushoffandfollow through into theswing phaseofgait. Rather thanusing amotor andgearbox having several times theweight ofthefoot, which cansupply therequired peakpower, areduced energy robotic device isbuilt witha0.95kgactuator thatusesonethird ofthe powerandonehalfoftheenergyrequired bya standard motor/gearbox solution. Thisdevice controls theequilibrium position ofthespring using aclosed loopposition controller. A realtimeembeddedsystemwasdeveloped intheMatlab Simulinkenvironment to formhardwarein theloop simulations andallowrapidcontrol prototyping. Notonly direct-control isdemonstrated using apredefined gait pattern butalsoState Logicisdeveloped inordertodetermine the user's desired gait pattern. Experimental data, gathered from ablebodysubjects walking onatreadmill provethatthesystem canassist gaitbydecreasing thepeakpowerthata subject should supply by50%.Itisalsodemonstrated thatsprings can applyregenerative braking andthattheconcept isfeasible and applicable indeveloping lightweight, functional wearable robots.