Increasing the stability margin of multilegged vehicles through body sway

An essential consideration in the development of any control algorithm for a multilegged vehicle is to maintain stability. If at any point during locomotion the vehicle becomes unstable, there is a possibility that the vehicle will overturn. In this research, we propose to include body sway motion into the motion planning of a quadruped's wave gait, such that its stability margin can be substantially increased. Two sway motions are proposed: Y-Sway and E-Sway. The Y-Sway motion is simple. It drives the center of gravity (CG) of the vehicle to approach the y-component of the geometric center of the contact points of the supporting legs. The E-Sway motion drives the CG to approach the desired CG locus for equal Energy Stability Levels. Both sway motions may be implemented in real time. Of them, the E-Sway motion can achieve a better stability margin. When sloped terrains are encountered, body-tilt compensation is also considered in the initialization phase to improve the stability margin. Simulation results show that body sway motions and tilt compensation are not mutually exclusive. Therefore, we may combine both actions to further increase the stability margin.