基于NSGA-Ⅱ算法的爬楼轮椅座椅调节机构多目标优化

Multi-objective optimization for seat-adjusting mechanism of stairs wheelchair based on the NSGA-Ⅱ algorithm

爬楼轮椅的座椅调节机构为一新型两自由度交叉四连杆机构,为了降低其动作过程中座椅所需驱动力矩即力矩性能,提高使用者的舒适性即舒适性能,增大座椅的工作空间即工作性能,需要对机构进行优化.由于机构杆件尺寸对上述性能会产生影响,为了得到最优的尺寸参数,对其进行运动学和动态静力学分析,建立了各性能与机构尺寸之间的函数关系,从而构建了机构尺寸参数的多目标优化数学模型,并采用NSGA-Ⅱ遗传算法得到了Pareto最优解,从中选取5组可行方案进行比较分析,最后利用Matlab将优化前后仿真结果进行比较发现,优化后的座椅调节机构具有更好的动态性能.

Seat-adjusting mechanism of the stairs-climbing wheelchair is an innovative mechanism which consists of crossed four bars with double degrees of freedom. In order to reduce the driving torque which is needed by the seat in action, i.e. torque performance, increase users＇ comfortableness, i.e. comfort capacity and enlarge the work-space of the seat,i.e. working performance, it is necessary to optimize the mechanism. The linkage dimension of mechanism could exert an influence on above-mentioned performance. In order to get optimal dimension parameter, kinematics and kinetostatics analyses were conducted to establish the function relationship between performances and dimensional mechanism, thereby the multi-targets optimal model of mechanism dimension was constructed. NSGA-Ⅱ genetic algorithm was employed to get the optimal solution of Pareto. Five groups of feasible programs were selected to make comparison and analysis. We adopted Matlab to compare simulation results before and after optimizing. Results suggested that seat adjusting mechanism after optimizing possessed better dynamic property.