Design and Analysis of the Leg Configuration for Biped Robots' Spring-like Walking

Spring loaded inverted pendulum (SLIP) model has proven to be successfully applied to implement the biped robots spring-like walking behavior. This work presents a compliant leg configuration which is characterized by the majority of mass being concentrated on the hip and the thigh and the shank being lightweight and spring-like, thus satisfying the configuration for SLIP model-based control. A numerical model was introduced to analyze the kinematics and the stiffness characteristic of the designed leg. Using the proposed model, analysis on kinematics showed that the leg configuration allowed an easy control of the leg swinging and the leg length. Additionally, analysis on stiffness showed that the leg could be taken as a variable stiffness spring regarding the length of the leg, the longer the leg, the greater the stiffness. After that, experiments of the legs stiffness were conducted on the leg prototype, validating the feasibility of the presented leg configuration and the numerical model.