Performance evaluation on land of an amphibious spherical mother robot in different terrains

In recent years, a variety of underwater microrobots were applied widely to underwater operations in limited spaces. The robots had some limitations of locomotion velocity and enduring time because of their compact structures. For solving these problems, we proposed a mother-son robot cooperation system and designed a novel amphibious spherical robot as the mother robot to carry the microrobots as son robots for collaboration. The spherical mother robot consisted of a sealed hemispheroid, two openable quarter spherical shells, a plastic circular plate, a plastic shelf for carrying microrobots and four actuating units. Each unit was composed of a water jet propeller and two servo motors, each of which could rotate 90° in horizontal or vertical direction respectively. The robot could implement on-land locomotion, as well as underwater locomotion. In this paper, a prototype spherical mother robot was developed and three walking gaits, decided by the duty factory, were designed for the on-land motion of the robot. Then the walking experiments were carried out in different terrains for evaluating the performance of the robot. From the results, the robot has a higher walking performance on tile floor. Under a control frequency of 3.33 Hz in Gait 3, we got a maximal walking velocity of 22.5 cm/s. For climbing performance, Gait 2 has the best performance on a steep slope with the inclination angle of 8°.