On quadruped attitude dynamics and control using reaction wheels and tails

This paper studies the attitude dynamics and the control of quadruped robots using tail-like appendages during the flight phases of high speed locomotion. Inspiration and data are first obtained from cheetah´s fast galloping techniques. A two-body template is then used to simply describe the dynamics of a large body whose attitude is controlled by a rotating appendage. The equations of motion for a tail and a reaction wheel are given, while by employing cyclic coordinates, all possible reductions are performed to finally lead to the design of model-based controllers. A main contribution lies on the thorough discussion on the holonomy of the system, which only depends on the system´s geometry and the initial angular momentum. A comparison between a reaction wheel and a tail is also carried out, while basic steps and formulas are proposed for selecting the key parameters concerning the design of such systems. Finally, simulation results are presented in order to validate the methods proposed herein.