Pitch control for running quadrupeds using leg positioning in flight

Pitching is often present as an undesirable motion in quadruped running. In gaits such as pronking, pitching must be completely suppressed for the proper execution of the gait. In this work, a novel control method is presented for controlling the pitching motion of a running quadruped robot in the pronking gait. A model of the quadruped robot is used to analyze the pitching motion dynamics. This analysis shows that setting the difference of the angles with which the back and front legs strike the ground is sufficient for controlling the pitching motion in the pronking gait. An analytical expression is derived which provides the necessary difference of the leg touchdown angles. It is further shown that there exists a particular robot design that is superior when suppressing the robot pitching motion. Implementation of the control scheme is shown through simulations of the robot model.