Spine Controller for a Sprawling Posture Robot

More and more biologically inspired robots present spines with multiples degrees of freedom to resemble their biological counterparts. The function of the spine on both animal and robot can play an important role in locomotion. If it has enough degrees of freedom to allow independent control of both shoulder and pelvic girdle (i.e., the points of attachment of body and limb), it can be used to extend the reach of the legs or to increase turning capabilities. In this letter, we present the spine controller for a sprawling quadrupedal robot. The controller achieves a synchronization between spine and legs and allows a precise control of the girdle positions by solving the inverse kinematics of the spine. The controller is validated in simulation and experiments with the real robot showing an ease in the control of the locomotion and achieving a very good tracking between the girdle trajectories with a very small, noncumulative error (less than 6% of the inter-girdle distance). This controller enables both the human operation and the implementation of autonomous path planning and navigation algorithms for these type of amphibious robots, making them more suitable for scenarios with limited maneuverability such as inside pipes or in collapsed buildings.