An energy efficient gait for a Nao robot

The gait of humans is often assumed to be the most energy efficient way of walking. Srinivasan and Ruina [18] confirm this hypothesis using a simple model in which the human is a point mass with straight legs that can change in length during a step. Their results show that the inverted pendulum walk is the most energy efficient gait. The question is whether this result also holds for humanoid robots. This paper investigate what is the most energy efficient gait for a humanoid robot such as the Nao, and what the corresponding control policy is that needs to be implemented. To answer these questions, first, the model of Srinivasan and Ruina is adapted for humanoid robots, and is used to study the energy consumption of different gaits. The model assumes a gait with dynamic stability and assumes that the torque on the knee joint provides the main contribution to the energy consumption of a gait. The former assumption implies that no energy is needed to remain stable. The latter assumption is confirmed by an experiment with a humanoid robot, namely Nao. Based on experiments with this idealize model, a gait that minimizes the energy consumption is identified. A controller for the new gait is implemented and is evaluated on a Nao robot. In the future, this controller will be the basis of an intelligent controller that can adapt to varying circumstances.