ANALYSIS AND SELF-TUNING CONTROL OF A ROTATING COMPLIANT LINK
Abstract
Self-tuning techniques represent a class of stochastic adaptive controls. They assume an input-output type of system model, identify the model parameters, and then devise a control action based upon identification results. The research presented in this thesis has four main thrusts: (1) the design of one-step-ahead self-tuning controllers satisfying a minimax criterion; (2) development of a finite-element based computer program for the simulation of a rotating compliant link; (3) the development of the pseudolink concept for representing nonrigid behavior in a link; and (4) the application of self-tuning to the control of a rotating compliant link. Proofs for the asymptotic convergence of the parameters in a self-tuner to some desirable parameter set are well known. However, there is no guarantee that the process under control will be well behaved during the transient phase. By using the parameter estimate uncertainty (a byproduct of the identification stage in most self-tuners) the optimal regulator gains for a class of self-tuning regulators are proven to be either zero or the certainty equivalence gain. A finite element based computer program for simulating a rotating compliant link is developed and documented. Three case studies are made to investigate the performance of the simulation program. In all three studies the results are found to be reasonable and in good agreement with theoretical responses. The final phase of this research involves the self-tuning control of a rotating compliant link. By using strain gages mounted along the link, modes characterizing the link shapes may be determined at each time sample. The angle of a hub to tip projection is modeled as a time series with the parameters of the model being estimated online. Using this information, a self-tuning control is then devised by treating the link as an equivalent fictitious pseudolink connecting the hub and tip of the compliant link. The advantage to this approach is that conventional trajectory planning based upon a rigid link assumption can be used. Experiments on a laboratory model confirm the validity of the approach.
Degree
Ph.D.
Subject Area
Electrical engineering
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