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.

Versatile multi-modal robots are advantageous for their wider operational environments. By taking design principles from observation of Pteromyini, commonly known as the flying squirrel, which shows balanced performances in both aerial and terrestrial locomotion, a novel robotic platform with the ability of gliding and walking is designed. The flexible membrane and gliding method of Pteromyini have been applied to the robot design. The legs of the robot were optimized to perform with regulated motor torques in both walking and gliding. The robot glided with an average gliding ratio of 1.88 and controlled its angle-of-attack for slowing down to land safely. The robot was able to walk utilizing different gait patterns. These results demonstrated our robot's balanced multi-modal locomotion of gliding and walking.