Control of a 3D Quadruped Trot

Legged vehicles offer several advantages over wheeled vehicles, particularly over broken terrain, but are presently too slow to be advantageous for many tasks. Trotting, the precursor to galloping for many quadrupeds, employs high-speed actuation to coordinate the intermittent ground contacts for each leg. Compliant elements and high-power actuators combine to perform a complex interchange of potential and kinetic energy during these short thrust intervals. These complexities, the frictional and contact losses that occur during normal running, plus the high number of degrees of freedom make three-dimensional (3D) dynamic quadruped motion very difficult to model accurately for control. For this reason, most of the research effort has been focused on simplified planar systems, only allowing motion in the sagittal plane. Many of these controllers only perform well around a fixed operating point and cannot regulate heading for desired changes in running direction. A 3D trotting controller which overcomes the above problems is presented here. Simulation results show the system responding appropriately to changes in the desired speed up to 3 m/s and heading up to 20 deg/s.