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Model-based Design on the Move at Cleveland FES Center
Leveraging MathWorks' suite of design tools, researchers can more quickly customize and test FES devices to help restore mobility to patients with neuromuscular disabilities.
Beth Stackpole, Contributing Editor -- Design News, October 2, 2009
Model-based design software is playing a behind-the-scenes role in helping researchers and doctors restore some movement and mobility to patients suffering from neuromuscular disabilities typically resulting from a stroke or paralysis.
The Cleveland FES Center at Case Western Reserve University is a consortium of the university, the Louis Stokes Cleveland VAMC and MetroHealth Medical Center, which are working in partnership to advance the clinical deployment of technologies and treatments dedicated to restoring function in people that suffer with neuromuscular disorders. The primary focus of the center's research is functional electrical stimulation (FES), the concept of applying electrical currents to generate or suppress activity in the nervous system, which in turn, helps patients produce and control movement of otherwise paralyzed limbs for such functions as standing or grasping with hands.
At the heart of the center's effort is a physical FES device, akin to a pacemaker, which is surgically implanted inside a patient along with lead wires that go to the individual muscles. Both are controlled through a separate, external device, which consists of a microcontroller along with a power supply and user interface for administering the unit. While the physical hardware remains the same with each patient, the software that controls how and where the electrical stimulation is delivered to produce the movement varies according to the individual's specific impairment. Once programmed with a course of action, the external FES control unit sends electrical impulses to electrodes, which are implanted in the body or worn on the skin. The electrical impulses restore some mobility to patients allowing them to stand, in some cases, or to regain some use of their hands for grasping motion, according to Robert Kirsch, PhD, professor, Biomedial Engineering, at Case Western Reserve University and associate director of technology for the Cleveland FES Center.
Traditionally, the research team at the center relied on electrical engineers to individually program each device to meet the patient's requirements - a process that could take weeks. Now, using software from The MathWorks, the center's own research engineers are now able to customize and test prototype FES devices for a specific patient's course of treatment immediately using model-based design techniques like graphical block diagramming.
"There's no such thing as a standard spinal cord injury or standard stroke-people have a variety of impediments and we often have to customize the application for the particular use," says Kirsch. "It was a very slow process, from identifying the change to utilizing the change. We were looking for something to turn it around much faster."
To address the latency issue, the FES Center research engineers developed the Universal External Control Unit (UECU), a modular software and hardware architecture so engineers in the clinic can modify FES controller applications and immediately test the results. Using the Simulink modeling and simulation software for multidomain systems and the MATLAB technical computing and programming environment, among other tools, research teams can now develop algorithms that suit individual patient scenarios, reducing the development cycle for FES functions to as little as a day.
"The Simulink approach and real-time tools allowed us to modify our control algorithms and instantaneously try them in a participant," Kirsch explains. "All we have to do is adjust the block diagram, build the model and download it into the external control unit to test in the participant. Instead of taking three weeks, it now takes a half hour or 20 minutes."
Ultimately, the approach means the FES Center can be more responsive to its patient's needs - currently close to 50 individuals are benefiting from the FES technology as part of their research. From a development perspective, the model-based tools have changed the game in terms of how the FES Center develops application software. "Software has always been the bottleneck and that's no longer the case," Kirsch says.
Application developed by an FES Center clinician to provide arm and hand control using an implanted stimulator.
