April 22, 2009
Program: Robotic Exoskeletons for Gait Assistance and Training
of the Motor Impaired
Speaker: Dr. Sunil Agrawal, ME Department, UD
Before starting the main talk, Dr. Agrawal showed some studies and tests on special needs
infants; Infants who were unable to participate in usual activities due to inability to move around were given a baby sized electric cart. They responded to this very well, and all were amazed at the learning speed of babies in carts.
The main talk addressed the need for about 7.7 million stroke victims, with about 700 thousand new ones every year; and 250 thousand with spinal cord injury (11,000 new cases every year) to be able to recover some mobility. Typically, strokes affect one side only so that the walking problem is to get a normal gait restored by working on the affected side.
The robotics study has been funded for about 5 years, with another 5-year program just starting.
During the program, movies showed a number of chronic (affected for about 3 years or more) victims having their walking gait improved by training with a treadmill that had either
1. A spring loaded appendage (called Gravity Balancing Orthosis, GBO) attached, or
2. A motorized appendage (called Actively driven Leg Exoskeleton) attached to their leg.
A normal gait was encouraged by the spring device by effectively reducing gravity, or programmed into the appendage by use of the motor drives. In the case of ALEX, the leg was “helped” when it ventured outside of the normal gait motion.
Using a training period of about 6 weeks, during which the patient exercised for a few hours during a week, and the “help” was diminished over the program, dramatic improvement was observed. The patient was then allowed to train 4 weeks at home.
The “spring” mechanism had the advantage of affordability and simplicity. The motorized version was more costly, but offered the advantage of direct feedback to the patient. In both cases, the patient was able to have some feedback by viewing a graphics terminal that showed how his motion varied from the ideal.
There was some brief discussion on adjusting the gait of someone with no walking problem, but might wish to change gait for a special purpose, such as golf swing or a sports objective. Tests have shown that temporary changes can be made that last for a few hours using the gait adjusting technology described above. This area is just beginning to be looked into.
Mention was made of the Berkeley exoskeleton system that was advertised as being a way for a soldier to carry heavier loads. Although the soldier was able to carry heavier loads, his oxygen intake requirement went up, so the Army did not see a benefit to that system and the idea has been dropped for the time being.
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