假肢膝关节机构的多目标优化设计

摘要

BACKGROUND: Nowadays, how to achieve the comfortableness and flexibility is the focus of the studies on artificial knee joint. OBJECTIVE: To analyze the law of the instantaneous center of the knee during exercise and to construct a suitable evaluation function to make it better meet the requirements of the wearer comfort and natural, then get the prosthetic knee joint structural parameters.METHODS: This paper focused on the four-bar linkage mechanism of artificial knee joint, the kinematics of mechanism model was constructed and the centrode of connecting rod was deduced on the basis of three centrosomes theorem. Regarding the comfortableness, the marking system model was established as the evaluation function; further regarding the flexibility, the multi-objective optimization model was established based on the dual optimization objective gained from the minimum total departure of actual and ideal instantaneous center in the process of bending knee and on the maximum value of evaluation function, as well as on the restriction of artificial knee joint mechanism bionics and the restriction of the double rocker linkage size. RESULTS AND CONCLUSION: Utilizing primary target method and MATLAB program, the parameter of optimal artificial knee joint mechanism was gained. The designed four-bar mechanism can well realize the coordination of the comfortableness and flexibility.%背景:如何实现穿戴者的舒适性、运动的灵活性一直是假肢膝关节研究的焦点.目的:分析膝关节运动过程的瞬心规律,构造合适的评价函数,使其更好地满足穿戴者舒适与自然的要求,进而得到假肢膝关节结构参数.方法:选取假肢膝关节四连杆机构作为研究对象,建立机构运动学模型,并利用三心定理,推导出连杆瞬心轨迹.考虑穿戴者运动的舒适性,建立了打分系统模型作为评价函数.进一步考虑假肢运动的自然性,以膝盖弯曲过程中实际瞬心与理想瞬心总偏差最小,以及上述的评价函数最大值作为双重优化目标,以假肢膝关节机构仿生学约束、双摇杆机构尺寸约束作为约束条件,建立多目标优化模型.结果与结论:运用主要目标法,并通过MATLAB编程得到了优化后的假肢膝关节机构的参数.所设计的四杆机构较好地协调了假肢穿戴者的舒适性与运动的自然性.