Modeling and Control of an Articulated Tail for Maneuvering a Reduced Degree of Freedom Legged Robot

This paper presents dynamic modeling and control of an articulated robotic tail to maneuver and stabilize a reduced degree-of-freedom (DOF) quadruped robot. Conventional legged robotic systems consist of leg mechanisms that provide simultaneous propulsion, maneuvering and stabilization. However, in nature animals have been observed to utilize their tails to assist the legs in multiple tasks. Similarly, by incorporating an articulated tail onboard a quadruped robot, dynamic tail motions can be used to aid maneuvering. Therefore, tail implementation can potentially lead to simplifications in design and control of the legged robot since the legs will be responsible for only propulsion tasks. In this paper, a robotic system design consisting of an articulated tail and quadruped robot system is presented. Dynamic models are derived to analyze an optimal tail mass and length ratio to enhance inertial adjustment applications and develop an outer loop controller to plan tail trajectories for desired maneuvering applications. Results of analytical optimization are corroborated with measured data from biological animals. To decouple the dynamics of the articulated tail mechanism an inner loop controller using feedback linearization maps the desired behavior to the actuator inputs. This approach is validated using hardware-in-the-loop experiments with tail prototype in conjunction with simulated quadruped platform. Results demonstrate the capabilities of the articulated tail in enabling precise left and right turning (maneuvering).