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Gini - 2009 - New joint design to create a more natural and efficient biped


Gini G, Scarfogliero U, Folgheraiter M. New joint design to create a more natural and efficient biped. Applied Bionics and Biomechanics. 2009 Mar;6(1):27-42. DOI

10 Word Summary

Biomimemtic joints improve bipedal robot efficiency.


This paper presents a human-oriented approach to design the mechanical architecture and the joint controller for a biped robot. Starting from the analysis of the human lower limbs, we figured out which features of the human legs are fundamental for a correct walking motion, and can be adopted in the mechanical design of a humanoid robot. We focus here on the knee, designed as a compliant human-like knee instead of a classical pin-joint, and on the foot, characterised by the mobility and lightness of the human foot. We implemented an elastic actuator, with a simple position control paradigm that sets the joint stiffness in real time, and developed the basic controller. Results in simulation are discussed. In our approach the robot gains in adaptability and energetic efficiency, which are the most challenging issues for a biped robot.


  • Knee of robot is actuated by changing the set-point of agonist-antagonist spring pairs.
    • Uses the equilibrium point hypothesis as a source of inspiration.
  • A knee biologically means increased efficiency: longer step length and reduced energetic cost by only having to lift foot for clearance instead of lifting entire leg/torso.
  • Knee joint is made as two contacting cylinders instead of a pin joint.  This allows for the equilibrium point to be achieved with less knee torque for the same rise in foot clearance.
  • Equilibrium point controller has constant offset in error.
  • Acceleration feedback controller only works for unlimited torque actuators.