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Significant numbers of people in our society are affected by sensory or physical disabilities, each of which is unique in the problems it poses for the individual. As such, each device employed to help the disabled person cope with his/her particular problems must interact with the individual in a very specialized and intimate fashion. By employing microprocessors for the control of these helping devices a wide variety of specialized functions can be offered and reasonably adapted to the specific needs of the individual users. When the disability is an amputation above the knee, many individuals look to a prosthetic limb in the hopes of restoring lost functions. Such a limb is typically comprised of an articulated knee joint and a specially designed prosthetic ankle-foot complex, that partially simulates ankle and foot motion. Being an articulated joint, the knee of the limb allows for a more natural gait and provides a cosmetic appearance in many non-walking situations. To allow for a safe, natural, and effective gait a microcomputer controller for a prosthetic knee joint, offering variable damping during locomotion, has been designed and implemented. A simple model of the gait cycle has been incorporated into the control system. The control system monitors the angle of the knee joint together with the load placed on the foot, uses these data to determine the current phase of the gait cycle, and generates a control signal to alter the damping of the knee appropriately. One subject has used the prosthesis in a laboratory environment. A nice gait resulted for walking on level ground, up an incline, and down an incline, at a variety of walking speeds and gradients. The subject's attitude toward using the device was very positive. Presented in this thesis are the ways in which computers can be used to help the disabled, an anatomical and biomechanical basis for lower limb prostheses, previous solutions that have been offered for the control of an artificial knee joint, a model of the gait cycle used as a basis for controlling this joint, the implementation of a solution based on the model, the results of the work and a discussion of its value, and finally conclusions of the work and possible extensions to the system.
Computer Science