The benefits of actively using a tail for climbing a vertical surface are explored. Especially the energy efficiency of climbing with aid of a tail is of interest. In nature, woodpeckers, woodcreepers and treecreepers climb vertical tree trunks suspended by their feet and supported by their tail. Videos of these climbing birds are analysed. In general, the stride is initiated by the body pitching forward while simultaneously moving towards the trunk and accelerating up before lifting off.
A rigid body 2D planar model is presented. The trajectory for the minimal cost of transport for the robotic climber is found by solving a constrained nonlinear problem. The limiting factors and driving parameters of this legged locomotion gait are investigated. It is found that the locomotion economy reduces when the jump height and jump time approach the ballistic limit. Most energy is lost due to the damping modelled in the system, therefore is the energy efficiency mainly determined by the damping coefficient. The jump height is limited by the maximum power the actuators are able to supply. Furthermore, the contact forces constrained by a claw model, result in different paths.
One of the benefits of actively using the tail for climbing are that no actuator at the ankles is needed to climb.