Impedance Control of Human Ankle Joint With Electrically Stimulated Antagonistic Muscle Co-Contraction

Abstract

Functional electrical stimulation (FES) is often used,typically in an open-loop manner, to restore paralyzed motor function for daily living activities. Several feedback control strategies have been developed to improve the performance and usability of FES-evoked movement. However, most of them have been position controllers, while the control strategy for human movement has been known as impedance modulation. Moreover, few studies have attempted to use antagonistic co-contraction for FES feedback control despite its expected benefits, such as enhanced stability and performance and better rehabilitation outcome. In this paper, we propose a robust impedance controller for FES that can adjust the intrinsic joint stiffness using co-contraction. It consists of an impedance control law based on time-delay estimation to compensate for the nonlinear uncertain joint dynamics and an antagonistic muscle cocontraction allocator to address the intrinsic joint stiffness caused by the co-contraction. The proposed controller was implemented on the ankle joints of five healthy subjects to simulate a standing balance situation. The results verified that the proposed controller can achieve desired impedance accurately by adjusting the intrinsic stiffness that stems from the change in the amount of co-contraction (up to 48.4% better impedance achievement with high desired stiffness).

Prevention of muscle atrophy in ICU patients without nerve injury by neuromuscular electrical stimulation: a randomized controlled study

“…Other studies have shown that eccentric contraction may slow the onset of muscle fatigue by increasing muscle torque [ 41 ]. In addition, other studies have also found that the co-contraction of the agonist/antagonist muscle may produce higher loads, and the co-activation of the agonist/antagonist muscle can significantly increase the tension of the Achilles tendon that can further effectively stretch the ankle joint [ 42 , 43 ]. Therefore, the simultaneous stimulation of the agonist/antagonist muscle can improve the joint’s ROM.…”

Synergetic gait prediction and compliant control of SEA-driven knee exoskeleton for gait rehabilitation

“…Compliant control can provide a compromise between control accuracy and safety (Schumacher et al, 2019). Compliant control can control the position and force simultaneously and purposefully, including impedance/admittance control (Kim et al, 2021), hybrid force/ position control (Yang et al, 2020), and parallel force/position control (Wang et al, 2011). Compared to hybrid and parallel force/position control, impedance control focuses more on achieving the target relationship between force and position, but does not necessarily track the expected trajectories (Perez-Ibarra et al, 2019;Chen et al, 2020;Sun et al, 2020).…”