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Distributed Optimal Control via Central Pattern Generator with Application to Biped Locomotion

Yazdani Jahromi, Masoud | 2018

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 55980 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Salarieh, Hassan; Saadat Foumani, Mahmood
  7. Abstract:
  8. Human walking is widely recognized as one of the most adaptable and robust forms of locomotion in nature, with intricate neural and biomechanical systems interacting to support this complex behavior. It is proposed that these systems are organized in a hierarchical structure, with the lower level comprising a complex distributed system consisting of muscles and the spinal cord, and the higher level being the brain cortex. The higher level is responsible for training and monitoring the output of the lower level, and intervening when the lower system fails to stabilize the system. To control the lower level, one popular model that has emerged is the central pattern generator (CPG). It is suggested that a CPG is a neural circuit that is capable of producing rhythmic patterns of activity without requiring input from sensory receptors. These circuits are found in the nervous systems of many animals, from simple invertebrates to complex mammals like humans. Thus, the brain will not be in charge for controlling and producing movements during rhytmic activities. Inspired by this theory, this thesis proposes a two-layer control framework for fully actuated and underactuated systems with high degrees of freedom and rhythmic behavior. The lower control layer consists of a network of simple controllers, with each controller corresponding to a degree of freedom in the system. To ensure stability, the network is fed by a general state of the system. In the upper layer, a central controller is considered, responsible for training this network and monitoring the stability of the system. The proposed hierarchy controller has been shown to stabilize unstable systems with minimal feedback signal. The proposed architecture has been validated by simulating various types of fully actuated robots and two-legged underactuated robots. This control framework benefits from the stability of a central controller and the expandability, computational optimality, and robustness of a distributed system in failure conditions. Overall, the proposed two-layer control framework provides a promising approach to stabilize complex systems with rhythmic behavior, which has potential applications in fields
    such as robotics and biomechanics
  9. Keywords:
  10. Distributed Control ; Locomotion Control ; Central Pattern Generator ; Hierarchical Control ; Musculoskeletal System ; Fully Actuated Biped Robot ; Underactuated Biped Robot

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