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Design and Implementation of a Control Strategy to Sustain Postural Stability for a Lower Limb Exoskeleton

Khezrian, Reza | 2017

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 49314 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Vosoughi, Gholamreza; Moradi, Hamed
  7. Abstract:
  8. Nowadays, the developments in control and robotics provide rehabilitation and power augmentation applications for the exoskeleton robots. In the rehabilitation applications, the goal is to help elderly and persons with paraplegia to do their daily activities and movements. One of this applications is to help these individuals for postural stability and recovering balance after receiving perturbations. In this research, we propose a control strategy for a lower limb exoskeleton to help the wearer to recover balance after a perturbation without using crutches. Here, we concentrate on the stance phase when a push is exerted to the robot and try to make the system quite upright. Therefore, a proper model for human and robot is derived in the mentioned phase using realistic parameters. Then a simple posture controller has been derived based on human experiments and observations to provide stability under the prescribed situation. In the next step, the design parameters of balance controller have been tuned by genetic algorithm for tolerating higher values of perturbation. Afterward, considering the interaction of human and the robot, the interaction force has been taken into account. For this purpose, a supervisor controller has been developed based on the robot situation to adjust the torque of the robot in order to minimize the interaction force while maintaining the balance of system. Finally, an alternative stepping strategy has been developed based on the observations of healthy human experiments while the subjects wear the robot shoes. This supervisor defines the threshold for switching from the primary (hip) strategy to stepping strategy and determines the desired step length to avoid tipping. The results demonstrate proper response of the controller under perturbed situation
  9. Keywords:
  10. Interaction Force Control ; Lower Joint Mechanism ; Active Exoskeleton Robot ; Balancing Strategy ; Stepping Strategy ; Lower Limb Exoskeleton ; Balance Control ; Base of Support ; Bi-articular Muscles

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