Closed-Loop Neural Network-Based NMES Control for Human Limb Tracking

• Published in: IEEE transactions on control systems technology 2012-05, Vol.20 (3), p.712-725
• Main Authors: Sharma, N., Gregory, C. M., Johnson, M., Dixon, W. E.
• Format: Article
• Language: English
• Subjects: Artificial neural networks; Asymptotic properties; Asymptotic stability; Biological and medical sciences; closed-loop control of functional electrical stimulation (FES); Control systems; Control theory; Electrical stimulation; Feedback; Feedforward; Feedforward neural networks; Fundamental and applied biological sciences. Psychology; Knee; Muscles; Muscular system; Neural networks; neural networks (NNs); neuromuscular electrical stimulation (NMES); non-isometric contractions; nonlinear control; Peripheral nervous system. Autonomic nervous system. Neuromuscular transmission. Ganglionic transmission. Electric organ; robust integral of the sign of the error (RISE)-based feedback; Stability analysis; Striated muscle. Tendons; Studies; Tracking; Trajectory; Vertebrates: nervous system and sense organs; Vertebrates: osteoarticular system, musculoskeletal system
• ISSN: 1063-6536; 1558-0865
• DOI: 10.1109/TCST.2011.2125792

Closed-loop control of skeletal muscle is complicated by the nonlinear muscle force to length and velocity relationships and the inherent unstructured and time-varying uncertainties in available models. Some pure feedback methods have been developed with some success, but the most promising and popular control methods for neuromuscular electrical stimulation (NMES) are neural network (NN)-based methods. Efforts in this paper focus on the use of a NN feedforward controller that is augmented with a continuous robust feedback term to yield an asymptotic result (in lieu of typical uniformly ultimately bounded stability). Specifically, an NN-based controller and Lyapunov-based stability analysis are provided to enable semi-global asymptotic tracking of a desired limb time-varying trajectory (i.e., non-isometric contractions). The developed controller is applied as an amplitude modulated voltage to external electrodes attached to the distal-medial and proximal-lateral portion of the quadriceps femoris muscle group in non-impaired volunteers. The added value of incorporating a NN feedforward term is illustrated through experiments that compare the developed controller with and without the NN feedforward component.