Functional Electrical Stimulation to Aid Phonation in the Presence of Unilateral Vocal Fold Paralysis


The objective of the project is to engage and educate undergraduate and graduate students in the multidisciplinary field of bioengineering with particular focus on the understanding and control of muscle behavior using functional electrical stimulation. The proposed plan includes theoretical analysis, experimental investigation, and course development. The proposed research component aims to develop and validate a framework that will help to implement an efficient Functional electrical stimulation (FES) controller for human vocalization purposes. This framework enables control of paralyzed vocal folds improving the ability of patients affected by unilateral vocal fold paralysis to communicate effectively. The plan is to considerably improve the quality of life of patients with unilateral and bilateral vocal fold paralysis. The principle of FES is to use surface or implantable electrodes to generate pulses of current in intact motor neurons, thereby inducing contraction of these muscles and corresponding movement. Several challenges hinder the application of closed-loop FES outside of research labs, such as the highly nonlinear and time-varying characteristics of muscles. Furthermore, a stimulated muscle changes when fatigue occurs and individual muscle models are different. Even more challenging is the fact that there is a significant delay between stimulation and muscle contraction, adding to the processing and transmission delays in the electrical stimulation system. The closed-loop FES problem using an Output-Based Reference Control approach. The development of a robust control strategy in cooperation with voice-driven data acquisition and a novel electrode array for stimulation purposes provide a framework for guiding rehabilitation strategies for specific impairments.
The project extends nonlinear control techniques, such as backstepping, extremum seeking, Kalman filtering, and model reference control, to account for time delays, actuator amplitude and rate saturation limitations, and partial and noisy measurements, thereby substantially increasing the practical applicability of such algorithms. The real-time implementation and the requirements that the FES equipment is easy to setup and simple to use by therapists and patients add additional constraints to the control structure, which needs to be robust yet not overly complicated. The merit of this effort also lies in the opportunity to use these tools to advance understanding of the dynamic behavior of muscles and to investigate the possibility of controlling this behavior using feedback control techniques. The proposed activity explores creative, original, and potentially transformative concepts by considering an active, minimally invasive, closed loop control system for vocalization purposes. Breathing and swallowing have received a lot of attention for patients with vocal fold paralysis, but vocalization is still considered an open problem with unresolved issued due to the complexity of the larynx and the difficulties in stimulating the relevant muscles, without invasive surgeries, given their depth in the neck. The proposed development of a robust control strategy in cooperation with voice-driven data acquisition and a novel electrode array for stimulation purposes provide a solution to these issues.


Alexander Leonessa

Professor, Mechanical Engineering Department

Virginia Tech, Blacksburg, VA 24060