RAMIEL: A Parallel-Wire Driven Monopedal Robot for High and Continuous Jumping

Abstract

Legged robots with high locomotive performance have been extensively studied, and various leg structures have been proposed. Especially, a leg structure that can achieve both continuous and high jumps is advantageous for moving around in a three-dimensional environment. In this study, we propose a parallel wire-driven leg structure, which has one DoF of linear motion and two DoFs of rotation and is controlled by six wires, as a structure that can achieve both continuous jumping and high jumping. The proposed structure can simultaneously achieve high controllability on each DoF, long acceleration distance and high power required for jumping. In order to verify the jumping performance of the parallel wire-driven leg structure, we have developed a parallel wire-driven monopedal robot, RAMIEL. RAMIEL is equipped with quasi-direct drive, high power wire winding mechanisms and a lightweight leg, and can achieve a maximum jumping height of 1.6 m and a maximum of seven continuous jumps.

Continuous Jumping of a Parallel Wire-Driven Monopedal Robot RAMIEL Using Reinforcement Learning

“…We describe the body configuration and performance of the parallel wire-driven monopedal robot RAMIEL [6] handled in this study. An overview is shown in Fig.…”

“…In [6], the motion control of the jumping is performed by a controller similar to that used in [8]. The motion during jumping is divided into two phases: the stance phase in which the landing legs are on the ground, and the flight phase.…”

“…However, since the wire has some elasticity and stretches, the wire length often oscillates in tasks that require large force such as jumping, and as a result, the estimated joint angle often oscillates. Therefore, when a general controller [8] is applied to RAMIEL, the jumping motion is unstable, and 10 out of 16 trials resulted in less than two consecutive jumps [6].…”

“…On the other hand, robots such as [1]- [3] can jump continuously, but these robots have a maximum jump height of about 1.1 m [1], which is inferior to robots with a single jump. Therefore, we have developed a parallel wiredriven monopedal robot RAMIEL (paRAllel wire-driven Monopedal agIlE Leg) that is capable of high and continuous jumps [6] (Fig. 1).…”