Model-based Design on the Move at Cleveland FES Center

October 2, 2009

3 Min Read
Model-based Design on the Move at Cleveland FES Center

Model-based design software is playing a behind-the-scenesrole in helping researchers and doctors restore some movement and mobility topatients suffering from neuromuscular disabilities typically resulting from astroke or paralysis.

The Cleveland FES Centerat Case Western Reserve University is aconsortium of the university, the Louis Stokes Cleveland VAMC and MetroHealthMedical Center, which are working in partnership to advance the clinicaldeployment of technologies and treatments dedicated to restoring function inpeople that suffer with neuromuscular disorders. The primary focus of thecenter's research is functional electrical stimulation (FES), the concept ofapplying electrical currents to generate or suppress activity in the nervoussystem, which in turn, helps patients produce and control movement of otherwiseparalyzed limbs for such functions as standing or grasping with hands.

At the heart of the center's effort is a physical FESdevice, akin to a pacemaker, which is surgically implanted inside a patientalong with lead wires that go to the individual muscles. Both are controlledthrough a separate, external device, which consists of a microcontroller alongwith a power supply and user interface for administering the unit. While thephysical hardware remains the same with each patient, the software thatcontrols how and where the electrical stimulation is delivered to produce themovement varies according to the individual's specific impairment. Once programmedwith a course of action, the external FES control unit sends electricalimpulses to electrodes, which are implanted in the body or worn on the skin.The electrical impulses restore some mobility to patients allowing them tostand, in some cases, or to regain some use of their hands for grasping motion,according to Robert Kirsch, PhD, professor, Biomedial Engineering, at CaseWestern Reserve University and associate director of technology for theCleveland FES Center.

Traditionally, the research team at the center relied onelectrical engineers to individually program each device to meet the patient'srequirements - a process that could take weeks. Now, using software from The MathWorks, the center's own researchengineers are now able to customize and test prototype FESdevices for a specific patient's course of treatment immediately usingmodel-based design techniques like graphical block diagramming.

"There's no such thing as a standard spinal cord injury or standardstroke-people have a variety of impediments and we often have to customize theapplication for the particular use," says Kirsch. "It was a very slow process,from identifying the change to utilizing the change. We were looking forsomething to turn it around much faster."

To address the latency issue, the FES Center researchengineers developed the Universal External Control Unit (UECU), a modularsoftware and hardware architecture so engineers in the clinic can modify FEScontroller applications and immediately test the results. Using the Simulink modeling andsimulation software for multidomain systems and the MATLAB technical computingand programming environment, among other tools, research teams can now developalgorithms that suit individual patient scenarios, reducing the developmentcycle for FES functions to as little as a day.

"The Simulink approach and real-time tools allowed us tomodify our control algorithms and instantaneously try them in a participant,"Kirsch explains. "All we have to do is adjust the block diagram, build themodel and download it into the external control unit to test in theparticipant. Instead of taking three weeks, it now takes a half hour or 20minutes."

Ultimately, the approach means the FES Center can be moreresponsive to its patient's needs - currently close to 50 individuals arebenefiting from the FES technology as part of their research. From adevelopment perspective, the model-based tools have changed the game in termsof how the FES Center develops application software. "Software has always beenthe 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.

Model-based Design on the Move at Cleveland FES Center A

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