Survey of Semi-Passive Locomotion Methodologies for Humanoid Robots

Wheel-based locomotion is the most commonly used by mobile robots, due to its simplicity and robustness. However, when facing uneven terrain, such as steps or rocky terrain, its mobility is greatly reduced. Biped robots, in contrast, have a greater adaptation potential to these challenges due to the suitability of its structure. In spite of this, the traditional biped locomotion methods used by these platforms cause high energy consumption and display low adaptability to uneven terrain. The semi-passive or hybrid approach for biped locomotion allows for the (1) maximization of energy efficiency and (2) significant improvement of adaptability to uneven terrain. On one hand, this approach explores the dynamics of passive elements, like springs or rubber bands, in order to develop structures and walking gaits that minimize energy consumption. On the other hand, using passive elements grants complacency to the movement which increases the gait’s stability, specially on irregular terrains. This paper presents a survey of methodologies for hybrid locomotion, ranging from the addition of basic passive elements to incorporating complex compliant actuators and implementing control algorithms.