1 UW-MADISON COLLEGE OF ENGINEERING DEPARTMENT OF BIOMEDICAL ENGINEERING Assistive Device to Augment Strength in the Weak Hand of a Stroke Patient Tom Fleming – Team Leader Mark Reagan – Communicator Brad Rogers – BSAC Tyler Vovos – BWIG Client: Matthew Jensen, M.D. Advisor: Paul Thompson, PhD 3/12/20082 MID-SEMESTER REPORT March 12, 2008 Title: Assistive device to augment strength in the weak hand of a stroke patient Contents Background: .........................................................................................................................................................3 Design Problem: ..................................................................................................................................................4 Client Requirements: ...........................................................................................................................................5 Similar Products: .................................................................................................................................................5 Product Uniqueness:........................................................................................................................................6 Design Alternatives: ............................................................................................................................................6 Hydraulic Systems:..........................................................................................................................................7 Mechanical Systems:.......................................................................................................................................8 Electrical Systems: ..........................................................................................................................................9 Stepper Motor: ...................................................................................................................................................10 Advantages: ...................................................................................................................................................12 Disadvantages:...............................................................................................................................................13 Microcontroller: .................................................................................................................................................13 Sensor: ................................................................................................................................................................15 Advantages: ...................................................................................................................................................16 Disadvantages:...............................................................................................................................................16 Prototype Design: ..............................................................................................................................................16 Future Work: ......................................................................................................................................................17 Appendix ............................................................................................................................................................18 Product Design Specifications......................................................................................................................18 References..........................................................................................................................................................223 Background: More than 700,000 Americans suffer strokes annually. Stroke is the third leading cause of death in the country. And stroke causes more serious long-term disabilities than any other disease (ScienceDaily). A stroke can be very debilitating to its victims. The amount of damage done to the brain varies among stroke victims and consequently the physical debilities do as well. Patients can experience effects ranging from complete inability to move muscles to a mild deficit in mobility of muscles. Commonly, stroke patients incur damage to one hemisphere of their brain. This damage leaves them physically impaired on the opposite side of their body. Figure 1, PET scan of the human brain Studies have found that the brain is capable of many degrees of recovery to trauma. Scans, such as the PET and MRI, have been developed to detect the flow of blood in certain areas of the brain, see above Fig 1.4 Researchers have found that when a person completes a physical task, blood flow increases in the local of the brain responsible for that task. Using this technology it has been found that one ability of the brain is to transfer the responsibility of a function from the trauma hemisphere to the healthy hemisphere. The brain will undergo re-wiring rather than re-growth. This is like the brain using a “spare tire” to make up for the loss of function, as the function is never completely regained. The majority of improvement in function occurs within the first three months after stroke (ScienceDaily). Patient therapy during this post-stroke time could be extremely valuable. The goal of our design project is to augment the movement of the patient’s hand, allowing for a “smooth” process of brain repair to the region of the brain responsible for various hand movements. We would like our design to be capable of assisting a patient up to the average normal human hand grip strength, ~ 279 N (Oh and Radwin). A key characteristic of post-stroke hand mobility is that the majority of patients require more effort extending rather than gripping. Also, studies have shown that grip force and extension force are variable, depending upon the openness of the hand (Oh and Radwin). These trends in hand strength add complexity to hand therapy and will consequently be important components to the development of our device. Design Problem: After stroke some patients regain no movement of the affected body part, but most regain movement but not full strength. There are groups working on robotic devices that sense and augment movement. This helps the movement itself, and is
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