Robust low-order control of flexible joint manipulators
Astorga, Joaquin
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Permalink
https://hdl.handle.net/2142/23435
Description
Title
Robust low-order control of flexible joint manipulators
Author(s)
Astorga, Joaquin
Issue Date
1990
Doctoral Committee Chair(s)
Medanic, Juraj V.
Department of Study
Electrical Engineering
Discipline
Electrical Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Electronics and Electrical
Language
eng
Abstract
This thesis presents the application of novel linear time invariant techniques to the design of low-order controllers for flexible joint manipulators. The nonlinear manipulator model is linearized via the perturbation method about an unstable operating point. Some nonlinear terms are treated as an external disturbance, and parametric uncertainty is represented as the structured uncertainty of the nominal plant. The $H\sb{\infty}$-norm approach is then utilized to design a robust state feedback controller to stabilize the linear system and to give a specified bound on the disturbance rejection of the closed-loop system with enough robustness margin as to stabilize the actual nonlinear model.
The nominal linear system with the state feedback controller determines the reference dynamics to be retained by the low-order controller based on the projective controls approach. The residual dynamics of the closed-loop system are selected under a suitable criterion to enhance disturbance rejection.
The nonlinear model of the manipulator is also treated as a nonlinear system with structured uncertainty and sufficient conditions are determined for stability and disturbance rejection using linear state feedback and full-order controllers. Examples are given in the case of the one-link and two-link manipulators.
The decentralized control option is also studied. The design of the controllers is based on a linear decoupled model obtained from the linearized model. The methodology here follows the same two phases of design used in the centralized case. Adaptive mechanisms are illustrated to improve the robust performance of the low-order decentralized control.
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