| The human foot-ankle system was studied with the goal of exploring actuation methods for a robotic prosthesis. The human ankle skeletal and musculotendon structure is explained and related to the mechanical system of a robotic ankle. A new methodology for control of a foot-ankle prosthetic device was developed. It was shown that monitoring the angular movement of the shank in a phase place is a reliable method for calculating how the ankle should move. A well tuned system was shown to effectively enable a transtibial amputee to walk not only on flat ground, but also on slopes and stairs. Two algorithms for relating ankle movement to shank movement were developed and tested with an amputee subject. The advantages and disadvantages of each are discussed. Both control algorithms are of a continuous nature, meaning that the behavior of the ankle is a continuous function of the movement of the shank. Thorough testing of the control algorithm has shown it to be very robust, largely because of the continuous nature of the algorithm. It was important that the algorithm contain no if-then logic, decision making, or gait event estimation. All of this is accomplished with the use of one sensor. The algorithm is very simple and easily implemented. The performance was tested on the aforementioned activities and it was found that the robot is an improvement over a passive device and can lend the user confidence while negotiating slopes and stairs. Test in showed that a user can walk over level ground, walk forwards and backwards, ascend and descend stairs, and walk up and down slopes all at any desired speed. |
