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Title: Modelling and control of lower limb exoskeletons and walking aid for fundamental mobility tasks
Author: Linares, Daniela Miranda
ISNI:       0000 0004 6350 1777
Awarding Body: University of Sheffield
Current Institution: University of Sheffield
Date of Award: 2016
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In the last five decades, exoskeletons have emerged as a solution to assist paraplegic and elderly patients perform fundamental mobility tasks. The main challenge nowadays, is to develop a device that is safe, power sufficient, seamlessly integrates with the user, while being affordable. Several solutions have been proposed, and controllers have been identified as the only component which can enhance integration with the user without adding weight to the system, or increasing energy consumption. Moreover, a software platform where the mechanical design and control techniques can be assessed, prior to experimental trials, could save resources and decrease costs. In this thesis, the development of humanoid and exoskeleton models, within the SimWise virtual environment, to perform an initial validation of controllers proposed without the need of a physical prototype, is performed. Furthermore, the selected platform is evaluated regarding its fitness for this application. The methodology used to generate CAD models of a humanoid, exoskeletons and a wheel walker within the SimWise virtual environment is described, along with its integration with MATLAB Simulink. Two exoskeleton models with their corresponding controllers were developed, firstly, a hybrid exoskeleton with a wheel walker for restoration of walking in paraplegic patients. And secondly, an actuated exoskeleton for assistance in standing-up and sitting-down motions in both the elderly and paraplegic patients. The hybrid exoskeleton uses functional electrical stimulation as actuation for knee joints and a frame with brakes mounted at hip, knee and ankle joints to generate the walking cycle. The wheel walker is used for support and equilibrium. A fuzzy controller for the low level and a finite state controller for the middle level is developed. Validation of the system over repeated walking cycles, including external disturbances, and simulation of use by humanoids of different dimensions, is performed within the virtual environment and results discussed. PID low level control of hip and knee joints is used to analyse standing-up and sittingdown motions, and incorporated with an actuated exoskeleton for assisting elderly people on performing the aforementioned tasks. A finite state middle level control is developed to generate reference trajectories at variable velocities for the restoration of these motions for paraplegic patients. An optimisation algorithm is used to identify low level controller parameters for ankle joints. Finally, offline and online calculation and incorporation of zero moment point in the control loop is performed to assess equilibrium of the system.
Supervisor: M. Osman, Tokhi ; George, Panoutsos Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available