Design and Analysis of a Rotational Leg-type Miniature Robot with an Actuated Middle Joint and a Tail (RoMiRAMT-II)

In this paper, a rotational leg-type miniature robot with a bioinspired actuated middle joint and a tail is proposed for stable locomotion and improved climbing ability. The robot has four independently actuated rotational legs, giving it advantages of both wheel-type and leg-type locomotion. The design parameters of the rotational legs were determined by 3D simulation within the seven candidates that selected by a newly proposed metric. It also has unique characteristics inspired by biological structures: a middle joint and a tail. An actuated middle joint allows the frontal body to be lifted or lowered, which was inspired by a flexible body joint of animals, to climb higher obstacles. Effectiveness of the middle joint was analytically verified by the geometric analysis of the robot. Additionally, a multi-functional one Degree Of Freedom (1-DOF) tail was added; the tail prevented the body being easily flipped, while allowed the robot to climb higher obstacles. A bristle-inspired micro structure was attached to the tail to enhance straightness of locomotion. Body size of the robot was 158 mm x 80 mm x 85 mm and weighed 581 g including a 7.4 V Li-Polymer battery. The average velocity of the robot was 2.74 m.s(-1) (17.67 body lengths per second) and the maximum height of an obstacle that the robot could climb was 106 mm (2.5 times of leg length), which all were verified by experiments