Role of compliant leg in the flea-inspired jumping mechanism

Jumping locomotion has been widely employed in milliscale mobile robots to help overcome their size limitations by extending their range and enabling them to overcome obstacles. During jumping, the robot's legs experience acceleration that is up to an order of magnitude greater than the gravitational acceleration. This large force results in bending of the jumping legs. In this paper, we study how the bending of the leg affects the jumping performance of a flea-inspired jumping robot. To judge the effect of the leg compliance, the amount of energy lost during jumping is determined by examining the ratio of kinetic energy to input energy, which we define as the mechanical efficiency. The bending leg is dynamically modeled using a pseudo-rigid-body model in order to precisely analyze the energy transfer. Jumping experiments are performed for five different legs, each with a different stiffness. Shape memory polymer rivets, which are lightweight and compact, were used to easily switch out the legs. The mechanical efficiency of the robot with appropriately chosen leg compliance was 41.27% compared with 36.93% for the rigid case and 21.51% for the much more compliant case. The results show that optimizing the compliance of a jumping leg can improve the performance of a jumping robot.