Coactivation Method Based on Common and Differential Modes for Joint Angle Control for Functional Electrical Stimulation Control

摘要

Precise joint angle control for functional electrical stimulation (FES), which is used in a wide range of neurore-habilitation systems, has been a topic of interest for several decades. Many control methods focus on how to cope with highly nonlinear and time-varying properties of the musculoskeletal system. However, to achieve accurate joint control, redundancy of the musculoskeletal system must be taken into account. This paper proposes a coactivation method using the common and differential modes, which is defined by the sum and difference of the extensor and flexor activities. This method is based on the notion that the common mode is closely related to the apparent joint stiffness, while the differential mode is closely related to the joint angle. The differential mode proves to have a relatively linear relationship to the joint angle, which validates our method to control the differential mode. Experimental results show that the proposed coactivation method enables relatively high tracking performance even with a basic proportional-integral-derivative (PID) controller, suggesting that the proposed method implements natural coactivation similar to human motor control strateaies.