Abstract
Elaborating an efficient and usable mapping between input commands and output movements is still a key challenge for the design of robotic arm prostheses. In order to address this issue, we present and compare three different control modes, by assessing them in terms of performance as well as general usability. Using an isometric force transducer as the command device, these modes convert the force input signal into either a position or a velocity vector, whose magnitude is linearly or quadratically related to force input magnitude. With the robotic arm from the open source 3D-printed Poppy Humanoid platform simulating a mobile prosthesis, an experiment was carried out with eighteen able-bodied subjects performing a 3-D target-reaching task using each of the three modes. The subjects were given questionnaires to evaluate the quality of their experience with each mode, providing an assessment of their global usability in the context of the task. According to performance metrics and questionnaire results, velocity control modes were found to perform better than position control mode in terms of accuracy and quality of control as well as user satisfaction and comfort. Subjects also seemed to favor quadratic velocity control over linear (proportional) velocity control, even if these two modes did not clearly distinguish from one another when it comes to performance and usability assessment. These results highlight the need to take into account user experience as one of the key criteria for the design of control modes intended to operate limb prostheses.
Highlights
In the field of robotic prostheses, development in neuroscience, bioimagery, and physiological monitoring led to the introduction of multiple techniques aiming at providing a disabled subject with the control of the actuators of a prosthesis
Our study investigated a key aspect of robotic prosthesis control: the choice of the method converting physiological input command into prosthesis motion
In addition to performance metrics, widely used in the literature on mobile device control, we introduced usability metrics among the evaluation criteria employed to assess the different control modes
Summary
In the field of robotic prostheses, development in neuroscience, bioimagery, and physiological monitoring led to the introduction of multiple techniques aiming at providing a disabled subject with the control of the actuators of a prosthesis. From recent works on sensorimotor systems, several techniques employ brain–computer interfaces (BCI) recording neuronal activity, such as intracortical electrode matrices located in motor areas (Kim et al, 2008; Gilja et al, 2012; Sussillo et al, 2012; Golub et al, 2014), or surface electroencephalography (EEG) devices (Li et al, 2010). Due to their invasiveness and/or low acceptability, most of these techniques are currently limited to small-scale clinical use or experimental applications and have yet to be implemented on commercial systems
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