Jung Gwang-Pil, Choi Hong-Cheol, Cho Kyu-Jin
School of Mechanical and Aerospace Engineering/Institute of Advanced Machines and Design, Seoul National University, Seoul 151-742, Republic of Korea.
Bioinspir Biomim. 2017 Feb 10;12(2):026006. doi: 10.1088/1748-3190/aa575a.
Inspired by the relationship between leg compliance and jumping performance in the false stick insect, this paper describes how variations in leg compliance and jumping direction affect the performance of a flea-inspired jumping mechanism. The amount of energy lost during jumping was determined by examining the ratio of kinetic energy to input energy (also called conversion efficiency). Leg compliance is modeled based on the compliant mechanics to determine energy transfer during jumping and determined the optimum degree of leg compliance for maximizing performance. Jumping experiments are then performed using six different legs with progressively greater degrees of stiffness and three different jumping directions. The experiments show that conversion efficiency decreases by approximately 3-5% as leg stiffness increases, compared to the optimal case. In the most compliant legs (i.e. stiffness of 0.0338 Nm rad or less), conversion efficiency rapidly drops to near 0% because the leg bends so much that it cannot support the thrusting force. The optimal conversion efficiency tends to increase when the mechanism jumps vertically owing to reduced slippage and increased ground reaction force. These investigations show that optimizing leg compliance can improve the performance of a jumping robot by up to 5% by enabling more of the initially stored energy in the leg to be used. This finding will likely prove helpful for choosing the leg stiffness for a small-scale jumping robot.
受伪竹节虫腿部柔顺性与跳跃性能之间关系的启发，本文描述了腿部柔顺性和跳跃方向的变化如何影响一种受跳蚤启发的跳跃机构的性能。通过检查动能与输入能量的比率（也称为转换效率）来确定跳跃过程中损失的能量量。基于柔顺力学对腿部柔顺性进行建模，以确定跳跃过程中的能量传递，并确定使性能最大化的最佳腿部柔顺程度。然后使用六种不同刚度且刚度逐渐增大的腿部以及三种不同的跳跃方向进行跳跃实验。实验表明，与最佳情况相比，随着腿部刚度增加，转换效率大约降低3 - 5%。在最柔顺的腿部（即刚度为0.0338 Nm/rad或更低）中，转换效率迅速降至接近0%，因为腿部弯曲过度以至于无法支撑推力。当机构垂直跳跃时，由于滑动减少和地面反作用力增加，最佳转换效率往往会提高。这些研究表明，通过使腿部中更多最初存储的能量得以利用，优化腿部柔顺性可将跳跃机器人的性能提高多达5%。这一发现可能有助于为小型跳跃机器人选择腿部刚度。
