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Winck, Ryder


Supernumerary robotic limbs (SRLs) can be used to provide a person with extra arms to help with difficult tasks. For example, a task that normally requires three hands to complete could be accomplished by just one person with an SRL. One way to control an SRL and still leave both hands available is to use the foot. This paper describes two parts of developing this foot interface: characterizing the range of forces that the foot can apply, and prototyping systems for different control methods. First, a small sample of data was collected to learn how much force the foot can apply in different degrees of freedom including rotations about the ankle and translations of the foot. Typically, the most force could be exerted in plantarflexion. These forces were then used with a kinematic model of the leg to calculate the torques applied by each joint. It showed that, in most cases, the joints at the hip and ankle see the greatest torque. Two foot devices are currently being developed: a Foot Pedal and a Foot Plate. The former uses rotations of the foot in different directions to control the robotic arm while the latter uses force inputs from a stationary foot. For the Foot Pedal, each degree of freedom was outfitted with a spring return mechanism so that it could be used as a rate control device. Now, when the user relaxes their foot the pedal will snap back to its resting position. For the Foot Plate, software was developed to read and scale the inputs using a six-axis force-torque sensor. Additionally, adjustable scaling was implemented to accommodate users of different abilities. In the future, an experiment will compare the effectiveness of these two devices for both rate and position control methods.