Control layout design optimization for an upper-limb exoskeleton

Upper-limb exoskeletons (ULEs) can enable individuals with upper-limb disabilities move their paralyzed or weak arms and perform some daily activities independently. However, a challenge in using ULEs is providing an efficient and intuitive interface for severely disabled individuals. We developed a tongue interface for a ULE with five degree of freedom that provided full, continuous, and direct control of all degrees of freedom for individuals with complete paralysis in the arms. To be able to optimize the interface design, the aim of this study was to investigate the frequency and duration with which the different tongue control commands were issued while performing daily tasks. Ten able-bodied participants tongue controlled the ULE in one experimental session and performed six repetitions of a drinking task using two control layouts (three repetitions each). One control layout received input commands through tongue gestures and another layout through virtual joysticks. We recorded the number and duration that each command was used. The results showed that the commands for controlling the ULE end effector (participant’s hand) in a horizontal plane were used the most (median of three times per trial for forward, left, and right commands), followed by controlling the ULE in the vertical axis (median of two times per trial for up and down commands). Commands for opening and closing the hand and moving backward were used only once per trial. Future control layouts will be designed such that more frequently used commands will have a higher accessibility.