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Title: Shared-control for systems with constraints
Author: Jiang, Jingjing
ISNI:       0000 0004 5918 6188
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2016
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In the thesis we solve the shared-control problem for three classes of systems: a class of linear mechanical systems, mobile robots and rear wheel drive cars, via full state feedback or output feedback while ensuring that all the state constraints on the closed-loop systems are satisfied. To design the feedback controller for a system with state constraints we firstly remove all the constraints by changing the coordinates through a logarithmic function. Then the back-stepping method is used to design the controller and a Lyapunov-like analysis is used to prove stability properties of the closed-loop system. The shared-control algorithm is based on a hysteresis switch which reduces oscillations when changing the control authority from the human operator to the feedback controller or vice-versa. Unlike other shared-control methods, formal properties of the closed-loop systems with the shared-control have been rigorously established. We start the design of the full state-feedback shared-controller with the assumption that the admissible Cartesian configuration set Pa of the system is a time-invariant convex set defined by a group of linear inequalities. Then the results are extended to the design of shared-controllers via output feedback. In the cases in which only output feedback is available, we can solve the problem by either developing an observer or 'remodeling' the system. Through system remodeling we are able to deal with any shape of the admissible configuration set Pa, even time-varying ones. Simulation results help to illustrate how the shared-controller works and show its effectiveness. The state of the closed-loop system with the shared-control never violates the constraints. Experiments done on a mobile robot also demonstrate that the shared-control algorithm works well in practice and meets all safety requirements. In addition, the experimental results match the simulation ones, indicating that the modeling approximations are reasonable and suitable.
Supervisor: Astolfi, Alessandro ; Demiris, Yiannis Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available