Modelling of an active cognitive artificial leg

This modelling activity is conducted within the framework of the CYBERLEGs project. The scientific and technological global goal of the CYBERLEGs project is the development of an artificial cognitive system for dysvascular trans-femoral amputees’ lower-limb functional replacement and assistance in activities of daily living. CYBERLEGs will be a robotic system constituted of an active cognitive artificial leg for the functional replacement of the amputated limb and a wearable active orthosis for assisting the contralateral sound limb. CYBERLEGs will allow the amputee to walk back and forward, go up and down stairs, and move from sit-to-stand and stand-to-sit with a minimum cognitive and energetic effort. The control system of CYBERLEGs will be based on motor primitives as fundamental buildings block, thus endowing CYBERLEGs with semiautonomous behaviour for planning the motion of the prosthesis joints and the assistive action of the orthosis module. CYBERLEGs will be capable of high-level cognitive skills, interfaced to the amputee through a bi-directional interaction.

CYBERLEGs will be able ‘to understand’ user-motor intentions smoothly and effectively and to prevent the risk of fall for the amputee, by means of a multi-sensory fusion algorithm based on:

  •     The observation of the motion of the amputee body;
  •     The interaction force between CYBERLEGs and the amputee;
  •     Their force interaction with ground.

Finally, CYBERLEGs will be capable of closing the loop with the amputee: the amputee will receive an efferent feedback from CYBERLEGs which will enhance the perception of CYBERLEGs as a part of his/her own body.

The Robotran software is used for simulating a healthy walking biped within the Matlab/Simulink environment. The underlying dynamic model does not only include the multibody model (9 bodies and 11 joints) but also the muscle dynamics (14 muscles) as well as a reflex-based control layer. This walker actually mimicks the model from Hartmut Geyer and Hugh Herr (IEEE TRANSACTIONS ON NEURAL SYSTEMS AND REHABILITATION ENGINEERING, VOL. 18, NO. 3, P. 263, 2010). In the near future, this model will be modified to simulate the effects of the pelvis and prosthesis devices. The orthosis model will considered in a second step.


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