| Ankle prosthesis is an alternative tool for patients with knee amputation to recuperate ankle function. With the development of economy and the improvement of people’s living standard, traditional ankle prostheses with the basic walking function could no longer meet the need of amputees. Devising a more comfortable ankle prosthesis with proper gait trajectory has become an urgent need in the field of prosthetic design. In this paper, an ankle prosthesis was designed on the basis of the characteristics of gait phase to help amputees regain the ability to walk. The work has important social significance and academic value. In summary, the main contents of the paper are as follows.(1) Research on the biomechanical properties of human ankle joint. Firstly, the human ankle joint gait characteristics in each phase of walking were elaborated. Then the basic characteristics, biomechanical characteristics and the ankle torque characteristic curve of the ankle joint were obtained by analysis of kinematics and biomechanics on various parameter data curve of the ankle joint. The relationship between the torque and the angle of ankle joint in each phase of a gait cycle was analyzed in detail, which provides a theoretical basis for the structure design and dynamic simulation of active and passive foot-ankle system.(2) The design of foot-ankle system. Based on the torque characteristic curve of the ankle joint, the design of the overall structure for the foot-ankle was put forward and accomplished in the paper. Some of the key mechanisms were analyzed by mathematical modeling and the parameters of the key components were verified by calculation. The basic working principle for the foot-ankle system was explained in a gait cycle. The process of energy storage and release in each phase of gait was analyzed, which verified that the structure model of the integrated foot-ankle system was feasible.(3) Dynamics simulation and optimization of the foot-ankle system. The simulation model of the foot-ankle system was established. A series of optimal parameters, such as the stiffness of the spring and the torsion spring, the position of the spring and the joint driving torque, were obtained by dynamic analysis and parameter optimization in ADAMS. The results of the energy analysis show that designed foot-ankle system has a similar mechanical property with that of human ankle and low energy consumption by recycling energy. The result verified the correctness of the modeling and analysis method.In the end, the experimental system was established to get the actual ankle angle curve in accordance to the experiment plan. The experimental results were compared with the theoretical ankle angle curve. The results show that the simulation method was correct and the designed active and passive foot-ankle system was feasible. |
