The Assessment of 3D Force Feedback for Closed-Loop Control of Myoelectric Hand Prosthesis

Abstract

The prosthesis grasping force feedback can be conveyed to users via sensory substitution (vibrotactile encoding) or modality-matched stimulation (physical force exertion). To date, the two approaches are rarely compared and, typically, they are designed to convey only the normal grasping force component. This letter developed a lab based closed-loop myoelectric prosthetic control system using a collaborative robotic arm to render high-fidelity 3D grasping force from the prosthetic end-effector on the user. Experiments with 11 subjects (10 able-bodied, 1 amputee) demonstrated that: (1) Tangential force feedback facilitated accurate perception of slippage tendencies under visual deprivation. (2) In stiffness identification, visual + force feedback significantly outperformed both visual-only and visual + vibrotactile feedback in accuracy (87.1% vs. 43.1% and 80.2%) and decision time (9.8 s vs. 11.6 s and 10.7 s). (3) In force tracking, exclusive force feedback (rather than exclusive vibrotactile feedback) significantly minimized tracking errors compared to visual feedback, with visual + force feedback achieving the lowest RMSE (3.70 N) compared to the visual feedback (4.89 N) and no feedback (5.34 N). The results indicate that visual feedback alone is inadequate for force control, and the addition of a haptic channel significantly improves performance. Overall, the proposed 3D force feedback system offers broad applicability, implying that its socket-integrated miniaturization could facilitate dynamic grasping and manipulation.