月球车轮腿机构模糊优化设计

Fuzzy Optimization Design of a Lunar Rover Wheel-legged Mechanism

以基于二级半转机构步行运动原理的轮腿式月球车的轮腿机构为研究对象,以轮腿机构体积最小、质量最轻为总目标,建立其优化目标函数。在考虑月球车的车身起伏度、垂直越障能力、抗干涉能力和转向能力等性能要求,分别建立相应的优化设计约束函数。考虑了月球车轮腿机构行星轮系的齿轮齿面接触疲劳强度、齿根弯曲疲劳强度、机构几何边界约束条件及越障性能的前提下,对轮腿机构参数进行综合模糊优化设计。具有模糊性的齿轮许用应力采用降半梯形分布隶属函数,其他变量或约束的模糊分布采用分布隶属函数。采用二级模糊综合评判法莱确定其最优水平截集,将模糊优化问题转化为常规优化问题。在满足优化数学模型函数值最小的前提下,利用Matlab优化工具箱获得了轮腿机构参数的综合优化结果,其总体积及总质量分别减少了约36.4%及25%。

For the wheel-legged mechanism of a lunar rover based on a double-half-revolution mechanism, the total optimal objective function was set up, which takes the minimum volume of the lunar rover as the total optimal goal. Considering rover body fluctuation, vertical obstacle-climbing capability, anti-interference ability and steering capa- bility performance requirements, their corresponding optimization design constraints were obtained respectively. In order to meet the surface load capacity of gears, the bending load capacity of gears, the geometrical boundary con- straints and the obstacle performance, the wheel-legged mechanism parameters were designed by using fuzzy optimi- zation method. Gear allowable stress fuzzy constraints are described by the drop half trapezoid membership func- tion, and other fuzzy constraint variables are described by the trapezoid membership function. The optimal level set was determined by adopting two-level fuzzy comprehensive evaluation method, thus a fuzzy optimization problem is turned into a conventional optimization problem. The objective function values were achieved by Matlab optimization toolbox. The optimization results show that its total volume is reduced by about 36. 4%, and its total mass is reduced by about 25 %.