CAREER: Nonlinear Control of Human Skeletal Muscle

University Of Florida, Gainesville FL

Investigators

Abstract

Abstract This CAREER award seeks to develop an integrated research and educational foundation in nonlinear control methods for artificial electrical stimulation of human skeletal muscle. Current clinical practices for treating medical disorders through the application of electrical stimulation are based on patient independent protocols for the open-loop adjustment of stimulation parameters (e.g., amplitude, phase, and pulse duration). Research focused on closed-loop electrical stimulation is based on either pure feedback control or feedback control with the addition of a feedforward component composed of soft computing elements (e.g., artificial neural networks, fuzzy logic sets). Unfortunately, these methods do not fully exploit the potential benefits of on-going research focused at more effectively modeling muscle response. Research efforts in this project will focus on the development and experimental validation of nonlinear control methodologies that incorporate muscle models in the design and analysis as a means to achieve a predictable response despite intra- and inter-subject variability and fatigable force production capabilities of the muscle. Outcomes of this research will advance knowledge in artificial electrical stimulation research through the development of new mathematical models that can be used to alter stimulation parameters to reduce fatigue. These models will be incorporated in the first ever use of Lyapunov-based methods as a means to encapsulate muscle response phenomena in a neuromuscular electrical stimulation controller. Lyapunov-based methods will be used to design controllers that exhibit input saturation and are adaptive to time-varying inter- and intra-subject variations, yielding a customizable neuroprosthesis. There are direct outcomes of the research efforts that impact society through the clinical applications and the scientific advancement of modeling and control research, but further outcomes will result by the exposure of students to human-machine interaction technologies and the impacts of science and engineering for the treatment of disease and disability. Neuromuscular electrical stimulation (i.e., the application of an electrical current via internal or external electrodes which results in a muscle contraction) offers an enormous promise to treat or alleviate the debilitating morbidity associated with certain diseases and dysfunctional conditions. Neuromuscular electrical stimulation is currently prescribed to treat a wide range of disorders and has rapidly grown because of the potential improvement in the activities of daily living for individuals with movement disorders such as stroke and spinal cord injuries that affect over one million Americans annually. In addition to serving as a treatment, neuromuscular electrical stimulation can provide an artificial extension to the body (i.e., a neural prosthetic) to restore or supplement function lost due to disease or injury with the goal of reducing the resulting implications on society and improving the quality of life of individuals. An attraction of such a neuroprosthesis is that the bodys own muscles are used to restore movement, leading to significant secondary benefits such as reducing muscle atrophy and the associated changes in metabolism and reduced risk for heart failure, the leading cause of death among individuals with spinal cord injuries. Unfortunately, current commercial electrical stimulation products have yielded limited functional outcomes for patients because ad hoc stimulation strategies are used that are not patient specific and lead to rapid muscle fatigue. The goals of this project are to develop new electrical stimulation controllers that (1) would enable long periods of physical activity that (2) could be customized and adapt to an individuals ever changing musculoskeletal system. To achieve the goals, efforts will focus on bridging the current gap between biological physiology research and control engineering research by incorporating neuromuscular models in novel adaptive control designs that elicit a desired muscle response. Given the potential benefits to the quality of life of an individual and the impacts on society of such emerging research, the worldwide market for neurotechnology products including motor system neuroprostheses, neuromodulation devices, and therapeutic muscle stimulators is predicted to grow from $2.4 billion in 2004 to $7.2 billion by 2008.