High-level locomotion intent estimation from electromyography and body posture.

Abstract

<i>Objective.</i>Once we learn a reliable gait, we no longer have to consciously contract individual muscles to walk, or think about the fine-grained low-level control of our joints. Instead, we mainly make decisions on where we want to end up, at what pace and through which path. Estimating this high-level (HL) intent may provide the necessary input to wearable robotic devices to adapt to their user's needs. We introduce a continuous representation of locomotion goals and investigate how it may be estimated from muscle signals and body posture.<i>Approach.</i>This study investigated methods to estimate a representation of HL locomotion intent, the horizontal walking path. We collected full-body motion capture and bipolar surface electromyography data from 6 subjects during non-steady-state gait. We trained temporal convolutional networks to causally predict the walking path directly or parametrically with a critically damped trajectory model, using a mixture of muscle and body posture signals.<i>Main results.</i>We achieved a mean trajectory estimation accuracy for a 1-second walking path corresponding tor2=0.89using a multimodal model. We simultaneously provided estimates for current and desired walking velocities as constrained by the walking path model, aiding interpretability of the estimator's output.<i>Significance.</i>Our approach could provide user interfacing in a subject-independent format for wearable robotic devices. Moreover, this HL intent representation is flexible and able to be synthesized in virtual environments, where it can serve as a surrogate for biosignals of simulated intent-driven robotics.