Development of a New Hydraulic Ankle for HYDROïD Humanoid Robot

For humanoid robots, design of the ankle mechanism is still open research problem since high torque is required while compact structures have to be maintained. This paper investigates an enhanced design of 3 degree-of-freedom hydraulic hybrid ankle mechanism. The design is based on (US9327785) Alfayad et al. (2011). Using a hybrid kinematic structure with hydraulic actuation, allows us to reach a slender humanoid ankle shape while enabling the high torque performances required for stable walking. Performances analysis of the first version ankle mechanism designed for HYDROïD humanoid robot showed some limits mainly induced by seal friction and pistons misalignment. In this paper, the influence of the friction parameters is explored. A virtual model is developed to evaluate the performances of a new flexion/extension and adduction/abduction pistons arrangement. Then, a control algorithm is simulated and implemented, as an example, to the flexion/extension motion of the new ankle mechanism. Finally, an experimental validation for the performances of the new proposed hydraulic ankle is conducted using the built hardware prototype, the results show significant improvement.