A Bio-inspired Knee Joint for Biped Robots

Imitating human joint structure in robotic joints can not only enable biped robots to realize more human-like locomotion, but also help humans to better understand the human body. This paper presents a bio-inspired knee joint for biped robots. The knee joint has the desirable characteristics similar to human knee joint including compliance, changeable instantaneous center of rotation, as well as the ability to achieve both active and semi-passive motion. Actuated by a pair of antagonistic pneumatic artificial muscles, the knee joint has a certain level of compliance. Springs that participate in the leg extension are equipped in parallel with the joint actuators, enabling the joint to work in semi-passive mode. Changeable instantaneous center of rotation is realized by adopting planetary gear transmission in the design. Simulation results demonstrate that the novel bio-inspired knee joint has superior performance to a conventional hinge knee joint in terms of motion range and power consumption, indicating that it can be potentially used in biped robots in order to realize efficient locomotion.