Single-leg hopping robot with coupled oblique inertial rotors for simultaneous midair attitude and foot placement control

Abstract

In this paper, we propose a single-leg hopping robot that can continuously hop to specified target locations on a planar surface while regulating its body attitude in three directions. The robot is driven by only four actuators, including a linear leg actuator that compresses a spring to generate hopping motion, a hip joint that rotates about the pitch axis to adjust the touchdown position, and two obliquely mounted inertial rotors. The coupling of the torques generated by the two rotors in this work is not only used for midair attitude regulation, but also exploited to adjust the leg touchdown location, thereby enabling control of the robot’s translational velocity and displacement. Owing to the oblique configuration, the two rotors can generate torques in both the roll and yaw directions. The coupling of the roll-direction torques is used to change the robot’s roll attitude in midair and indirectly modulate the lateral touchdown location, while the coupling of the yaw-direction torques is used to regulate the body orientation, allowing the robot to hop along a desired trajectory and heading. Consequently, the proposed robot can move in arbitrary directions on a planar surface while simultaneously controlling its body orientation. Experimental results demonstrate that the robot can continuously hop to specified target locations on the XY plane while maintaining a prescribed yaw attitude.