Design and analysis of a rotational leg-type miniature robot with an actuated middle joint and a tail (RoMiRAMT)

In this paper, a rotational leg-type miniature robot with an actuated middle joint and tail, called RoMiRAMT, 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 properly selected candidates. It also has unique characteristics inspired by biological structures: a spine and a tail. An actuated middle joint allows the frontal body to be lifted or lowered, which was inspired by a spine, to climb higher obstacles. Additionally, a multi-functional two degrees of freedom (2-DOF) tail was added; the tail provides instant deceleration, and minimized the likelihood of flipping, while allowing the robot to climb higher obstacles. A microcontroller was embedded in the robot, along with a micro-camera and an inertia measurement unit (IMU) sensor. By controlling the robot using the yaw angle signal measured by the IMU sensor, straight movement was enhanced. The body size of the RoMiRAMT is 155 × 80 mm without the rotational legs, and the weight is 593 g including batteries. The maximum velocity of the robot was 2.58 m/s (16.65 body lengths per second) and the maximum height of an obstacle that the robot can climb was 95 mm, which all were verified by experiments.