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Pedram Afshar — 2003-04 Fellow

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Human hand control mechanisms are extremely complex and currently there is no solution to restore full function to a paralyzed hand. Currently, partial restoration is achieved by using a normal part of the body to control prosthetic hardware. The optimal solution would be to use either cortical signals or desired joint angles/torques to stimulate existing muscles, thereby obviating the need for a prosthetic device and affording natural control to the patient. The limiting factor in achieving this goal is a poor understanding of the relationship between neural signals to the muscles and joint movements. There is no generally accepted model that relates the neural signal to a physical quantity. In addition, there are infinitely many sets of muscle forces that generate any given set of joint torques due to muscle redundancy and the ability to co-contract antagonist muscles.

This research describes a methodology to estimate and compare biological and mathematical solutions for the muscle forces for a given set of dynamic joint movements. Our preliminary results indicate that the mathematical solution obtained by finding the minimum forces resembles the biological solution. This methodology may allow us to identify the neuromuscular control strategies used during dynamic finger movements.