串并混联仿生机械腿静力学性能分析

Analysis of Static Performance of Serial-parallel Hybrid Bionic Mechanical Leg

仿生机器人的腿部结构由一个两自由度平面并联机构和RPR机构串联组成,具有承载能力大、能够实现快速行走的特点。阐述了机械腿的布局形式,建立了两自由度平面机构的运动学模型。采用虚功原理,根据运动学模型建立了两自由度并联机构的静力学传递模型;利用矢量极值法建立了静力学承载能力性能评价指标和力矩输入均衡性能指标,得到了两项性能指标在工作空间内的分布情况,并对其在工作空间内的分布规律进行了分析。结果表明,两自由度平面并联机构的静力学承载能力性能指标和力均衡性能指标总体呈对称分布,静力学承载能力性能指标在工作空间的底部承载能力最大,向上逐渐减小,到达顶部最小;力均衡性能指标在工作空间中间部位较优,越趋近于边界,性能指标越差,对机构越不利。通过实例与仿真验证了静力学性能分析的正确性,为该串并混联机械腿承载时的轨迹规划提供了参考。

The static performance of a new type of serial-parallel hybrid bionic leg mechanism was analyzed. The bionic mechanical leg structure was composed of a 2-DOF planar parallel mechanism and an RPR mechanism in series,which had the characteristics of large carrying capacity and fast walking. Firstly, the leg structure layout of the bionic robot was introduced, and the kinematics model of 2-DOF planar mechanism was established. According to the kinematic model, the static transfer model of 2-DOF parallel mechanism was established by using the virtual work principle. Secondly, the static bearing capacity performance evaluation index performance evaluation index and the force input equilibrium performance index were established by the vector extremum method, the distribution diagram of these two indexes in the working space was plotted, and the distribution law of these two indexes in the working space was analyzed. The analysis results showed that the static bearing capacity and moment equilibrium performance of 2-DOF parallel plane parallel mechanism were distributed symmetrically. The performance index of mechanical bearing capacity was maximum at the bottom of working space, and was decreased gradually upward, and then it was minimum at the top. The torque balance performance index was better in the middle part of the working space. The worse the performance index was closing to the boundary, the worse it was for the mechanism. Finally, the correctness of the static analysis of performance was verified by some examples and simulations, which provided a reference for the trajectory planning of the serial-parallel hybrid mechanical leg.