Elastic-Actuation Mechanism for Repetitive Hopping Based on Power Modulation and Cyclic Trajectory Generation

Abstract

Animal locomotion results from a combination of power modulation and cyclic appendage trajectories, but combining these two properties in small-sized robots is difficult. Here, we introduce and characterize a new elastic actuation system based on an inverted cam that is capable of generating cyclic locomotion with controlled elastic energy charge and release for small-sized robots. We designed a leg linkage and attached to the inverted cam to develop a single legged hopping platform with one actuated degree of freedom. The hopping platform was able to continuously hop forward at 1.82 Hz. The average horizontal hopping distance was 18.7 cm, and the average forward speed was 0.34 m/s. This speed was corresponding to a Froude number of 0.14. The energy consumed for one hop was 2.09 J, and the corresponding energetic cost of transport was 6.43. The combination of inverted cam and cyclic trajectory generation has the potential to be used in other robotic applications, such as flapping wings in the air and tail fin waving in water.

Dipo: a miniaturized hopping robot via lightweight and compact actuator design for power amplification

“…Based on the Dipo's hopping height, the Dipo has kinetic energy of 0.24 J and therefore, the energy conversion ratio is given as 10%. This seems to be a fair number in that the Salto-1P and the EPFL hopper show 8% (Haldane et al 2017) and 9% (Shin et al 2022), respectively.…”

“…For meaningful intermittent jumping, the process of storing and releasing a large amount of energy needs to be required. To this end, a parallel-elastic linkage has been mostly employed to amplify the electric motor's limited power (Lambrecht et al 2005, Kovac ˇet al 2009, Li et al 2012, Nguyen and Park 2012, Zhao et al 2013, Woodward and SITTI 2014, Zaitsev et al 2015, Jung et al 2016, Bai et al 2018, Li and Rus 2019, Hong et al 2020, Chae et al 2022, Hawkes et al 2022, Shin et al 2022.…”

Modeling, analysis and control of robot–object nonsmooth underactuated Lagrangian systems: A tutorial overview and perspectives

“…Hoppers and jugglers relationships are pointed out in [186,15]. Hoppers can be inertially actuated using springs which store potential energy and release it quickly [187,188] and thus recast in section 3.5. Various types of internal mechanisms for creating hopping motions have been designed [188,Table I].…”

“…They have received some attention in the literature [191,192,193,184,194,195,196,197,198,199,187,200] [200, Table I], and it is recognized that they also can be used in biped locomotion during flight phases to improve the stability [201]. The fact that they belong to robot-object systems was already noticed in [2, section 8.…”

“…5.4]). Hopping machines have most of the time been modeled with compliant spring-dashpot models [62,176,210,187] (named spring-loaded inverted pendulum SLIP). Encapsulating it into a complementarity framework is doable.…”