Stable, simultaneous and proportional 4-DoF prosthetic hand control via synergy-inspired linear interpolation: a case series

• DOI: 10.1186/s12984-021-00833-3
• Publication Date: 2021-03-18T21:02:48Z
• Authors: Platon Lukyanenko; Hendrik Adriaan D...; Joris Lambrecht; Robert F. Kirsch; Dustin J. Tyler; Matthew R. Williams
• Keywords: Interpolation; Feed forward

Abstract Background Current commercial prosthetic hand controllers limit patients’ ability to fully engage high Degree-of-Freedom (DoF) hands. Available feedforward rely on large training data sets for controller setup and a need recalibration upon prosthesis donning. Recently, an intuitive, proportional, simultaneous, regression-based 3-DoF remained stable several months without retraining by combining chronically implanted electromyography (ciEMG) electrodes with K-Nearest-Neighbor (KNN) mapping technique. The dataset requirements simultaneous KNN increase exponentially DoF, limiting the realistic development of in more than three DoF. We hypothesize that linear interpolation, muscle synergy framework, sufficient number ciEMG channels (at least two per DoF), can allow stable, high-DoF control. Methods Two trans-radial amputee subjects, S6 S8, were percutaneously interfaced bipolar intramuscular electrodes. At time study, S8 had 6 8 EMG electrodes, respectively. A Virtual Reality (VR) system guided users through single paired movements one four different 4-DoF cases. model user activity was built partitioning feature space into regions bounded vectors steady state movement patterns. evaluated online signals linearly interpolating class labels surrounding trained movements. This yields continuous, proportional controller. Controllers target-matching task which subjects controlled virtual match 80 targets spanning available space. Match Percentage, Time-To-Target, Path Efficiency over 10-month period based subject availability. Results conclusions In 3-DoF, matched most demonstrated control after 10 months, 4-DoF, both initially found usable, matching targets. showed improving trends 7–9 or at-home practice. unstable 7 retraining. These results indicate performance proposed this study may remain even improve, provided initial viability channels. Overall, demonstrates capable continuous up ten nine use minimal times.