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Dynamic Analysis and Control System Design for a Lower Extremity Exoskeleton

Ataei, Mohammad Mahdi | 2012

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 43875 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Salarieh, Hassan; Alasty, Aria
  7. Abstract:
  8. The present research has dealt with developing theoretic basis for technology of a modern and beneficial robot. There has been an old aspiration to attain some machine which can enclose body and move exactly in concert with it so as to maximize human might and endurance via powerful actuators. Exoskeleton robot is a recent successful invention regarding this aspiration, the lower-limbs type of which being sufficient for enhancing gait and load carrying capabilities.
    Modeling the dynamics of this robot is very fundamental and was done thoroughly for the first time in this research. In the available articles, at most, simplified models are investigated. Mechanical structure was selected inspiring from good studies in the BLEEX project and was changed a little considering other researchers' viewpoints. Next, dynamic equations were derived with both Newtonian and Lagrangian methods which proved several advantages for Newtonian approach. Through a test kinematic data of the gait cycle was measured using Xsens system. Dynamic model was verified via SimMechanics software by simulating inverse dynamics.
    Studying different control methods showed that impedance control (IC) is suitable for this application. Considering essential diversities between this robot and the current industrial robots, a formulation for IC was presented which is more versatile than methods available in references. Ideal tracking and low torques exerted on user's body in simulations clarified efficiency of the proposed method. After that for the first time control system of the exoskeleton was equipped with an adaptive algorithm causing tracking error and interaction forces to be reduced even from previous immaterial magnitudes. Finally a new method for adaptive impedance control was generated and its stability was proved. Advantage of the proposed method is being needless to calculate inverse of inertial matrix. Accordingly conditions making that matrix singular, which are common in many cases, won't ruin stability of this system
  9. Keywords:
  10. Dynamic Modeling ; Impedance Control ; Adaptive Control ; Exoskeleton

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