Energy efficient walking: combining height variation of the center of mass and curved feet

We use characteristics inspired by the human gait to reduce the energy expenditure of walking in low-cost humanoid robots. Our contribution is to implement the height variation of the center of mass during gait with foot motion around the ankle during gait phase changes. The robot’s foot is curved with a geometric shape that favors rolling motion on the ground. For the control, we extend the Preview Control of Zero-Moment Point technique for the planning of the center of mass, and we will adapt the 3D Linear Inverted Pendulum Model (3D-LIPM) so that our system is linear time-varying. Finally, the inverse kinematics gives us the position of the joints. To measure the energy, we will use a realistic simulator. In the simulator, the fully actuated robot stays in balance in a three-dimensional environment with gravity while walking. The results proved satisfactory, reducing energy expenditure by almost 25% when we combine height-varying and curved feet.