Continuity-Aware CPG Locomotion Control for a Jointless Hexapod Robot

Abstract

Minimal-DOF legged robots rely heavily on their mechanical compliance, which makes the actuator command profile an important part of the locomotion design. In particular, a piecewise-linear (C0) mapping from oscillator state to actuator position introduces velocity jumps at phase transitions. We present a CPG controller for a jointless hexapod robot that combines a duty-factor-modulated Hopf oscillator with a cyclic C1 trigonometric mapping. The mapping removes the velocity jumps and keeps the commanded acceleration bounded. In fixed-duration Webots trials, it changes forward travel by only 0.21% relative to a cubic Hermite C1 baseline while reducing lateral drift by 51.6%. Physical demonstrations on slopes, gravel, grass, obstacles, and stairs show that the same controller can be used across several terrain conditions. Project page: https://lequn-f.github.io/Hexapod