Roll oscillation modulated turning in dynamic millirobots

Abstract

As we seek to develop more maneuverable legged robots, we need to understand the dynamics of legged turning in an approachable fashion. In this work, we analyze the dynamic turning motion of a dynamic hexapedal millirobot. We explore a family of phase locked turning gaits where all legs of the robot move at the same speed. These gaits are highly periodic, allowing the vertical height and roll angle of the robot to be approximated by single harmonic sinusoidal functions. We demonstrate that oscillations in height and roll angle determine the robot's turning behavior. The phase between these oscillations (and therefore the turning behavior) was modulated by the phase between the left and right sets of legs. A simple model using compliant leg forces was shown to match turning behavior for a range of 5Hz turning gaits. Based on the finding that roll oscillations are major determinants of turning behavior, we modified the robot to create a new high speed turning gait (forward velocity: 0.4 m/s, turn rate 206°/s).