Loading...

Mehravar, Mohammad | 2011

522 Viewed
  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 41936 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Parnianpour, Mohammad; Narimani, Roya
  7. Abstract:
  8. Injuries of neuro-musculoskeletal system impose large costs to the modem societies. Studying the strategies of CNS in planning and control of movements can be helpful in developing diagnoSiS, prognosis and treatment procedures in clinical view and also in designing rehabilitation system and humanoid robots. Tow important features of human movements are redundancy problem and structured variability. Previous studies solved the redundancy problem mainly with optimization methods. Also optimal feedback control theory is the only method that successfully modeled structured variability in voluntary movements. Despite the appropriate outputs this methods are not based on physiological facts and also have many limitations. Synergy is a new concept in motor control that extracted from biological movements observations and can be used to describe redundancy and structured variability simultaneously. Mainly synergy has been considered as a descriptive concept rather than an analytic tool. In this study synergetic behavior in kinematic level for a functional task (sit to stand), has been studying, analyzing the features of synergy and constructing a simulation of task based on the results of these analyses. The kinematic data of STS for 3 task difficulty level and two groups (healthy and LBP), had been gathered using a motion analysis system. Sharing and error compensation features of synergy had been studying using PCA and UCM methods. With the results of UCM analysis we determined the priority of control in STS in different conditions. The results showed that there are strong synergies for control of horizontal and vertical positions of COM through the STS. The strength of these synergies increases with increasing difficulty level. Also increasing difficulty level increases the within trials variability in a structured manner. We constructed a 4 link inverted pendulum model of body in sagittal plane and simulated the STS task based on UCM concept. For planning the movement and solving the redundancy problem we used an open loop optimization method. For executing the planned movement we used the internal models concept together with ,. ---' feedback linearization control and the concept of uncontrolled manifolds. In each moment of time the controller compensates deviations from planned movements with different gains in different subspaces based on observed synergies. So in presented model the source of structured variability is the synergetic behavior of CNS for controlling the movement. The outputs of model subjected to the motor and sensory noise showed the structured variability very well.
  9. Keywords:
  10. Control ; Feedback Linearization ; Synergy ; Structured Variability ; Uncontrolled Manifolds

 Digital Object List

 Bookmark

No TOC