Cybernetic Interfaces for the Restoration of Human Movement through Functional Electrical Stimulation

Abstract:

Functional electrical stimulation (FES) is a promising technology for activating muscles in spinal cord injured (SCI) patients. The objective of our project was to develop an intuitive user interface and control system that allows high-level tetraplegic patients to regain the use of their own arm. This work has had two primary outcomes: contributions to the development of a technology that benefits those with high-level SCI, and the development of biologically-inspired design principles for cyber-physical systems. The project has had two main components: decoder development for determining how the subjects wish to move their arm, and controller development for getting the arm to the desired location (Fig. 1). We used human and animal models, allowing us to investigate practical issues relevant to our human subjects, and longer term questions dependent on the development of more robust cyber-physical interfaces for FES control. Here we summarize our major accomplishments.

Figure 1: Summary of project components.

We developed a novel architecture for a human-machine interface that could work with multimodal signals from the user and environment. The inherent flexibility of this system allows it to adapt to the specific capabilities of a user. We demonstrated its performance using disparate signals including electromyograms, eye-gaze recordings, direct recordings from the brain, and environmental information regarding probabilistic target locations. We also developed an efficient system identification algorithm incorporating a mixture of parametric and nonparametric models, providing benefits of each approach with respect to efficiency and accuracy. These techniques were coupled with our expanded knowledge of the human neuromotor system to develop controllers for restoring arm function following spinal cord injury. Specifically, we developed hybrid controllers for position, force, and impedance controllers. Finally, we disseminated our findings broadly and used our application area as motivation for a CPS curriculum developed and deployed for students in grades 6-8.