Selective RF excitation designs enabled by time‐varying spatially non‐linear Δ B 0 fields with applications in fetal MRI

2021 ◽  
Author(s):  
Molin Zhang ◽  
Nicolas Arango ◽  
Jason P. Stockmann ◽  
Jacob White ◽  
Elfar Adalsteinsson
Keyword(s):  
Fetal Mri ◽  
Time Varying ◽  
Non Linear ◽  
Rf Excitation

Adaptive control of time-varying non-linear plants by speed-gradient algorithms

2019 ◽  
pp. 37-44 ◽  
Author(s):  
O. P. Tomchina ◽  
D. N. Polyakhov ◽  
O. I. Tokareva ◽  
A. L. Fradkov
Keyword(s):  
Adaptive Control ◽  
Adaptive Systems ◽  
Reference Model ◽  
Maximum Deviation ◽  
Model Parameters ◽  
Time Varying ◽  
System Solution ◽  
Non Linear ◽  
Initial Uncertainty ◽  
Speed Gradient

Introduction: The motion of many real world systems is described by essentially non-linear and non-stationary models. A number of approaches to the control of such plants are based on constructing an internal model of non-stationarity. However, the non-stationarity model parameters can vary widely, leading to more errors. It is only assumed in this paper that the change rate of the object parameters is limited, while the initial uncertainty can be quite large.Purpose: Analysis of adaptive control algorithms for non-linear and time-varying systems with an explicit reference model, synthesized by the speed gradient method.Results: An estimate was obtained for the maximum deviation of a closed-loop system solution from the reference model solution. It is shown that with sufficiently slow changes in the parameters and a small initial uncertainty, the limit error in the system can be made arbitrarily small. Systems designed by the direct approach and systems based on the identification approach are both considered. The procedures for the synthesis of an adaptive regulator and analysis of the synthesized system are illustrated by an example.Practical relevance: The obtained results allow us to build and analyze a broad class of adaptive systems with reference models under non-stationary conditions.

Reduced-Order Modeling Technique for Weakly Non-Linear Time-Varying Circuits with Memory

2003 ◽  
Author(s):  
F. J. Casas ◽  
J. Portilla ◽  
R. Quere ◽  
A. Mallet ◽  
J.F. Villemazet
Keyword(s):  
Linear Time ◽  
Reduced Order Modeling ◽  
Modeling Technique ◽  
Time Varying ◽  
Reduced Order ◽  
Non Linear ◽  
With Memory

Non-linear dynamic analysis of time varying length flexible body

2020 ◽  
Vol 2020 (0) ◽  
pp. 513
Author(s):  
Masato TAKEUCHI ◽  
Kensuke HARA ◽  
Hiroshi YAMAURA
Keyword(s):  
Dynamic Analysis ◽  
Flexible Body ◽  
Time Varying ◽  
Linear Dynamic ◽  
Non Linear ◽  
Varying Length

A Non-linear and Noise-Tolerant ZNN Model and Its Application to Static and Time-Varying Matrix Square Root Finding

2018 ◽  
Vol 50 (2) ◽  
pp. 1687-1703
Author(s):  
Xiaoxiao Li ◽  
Jiguo Yu ◽  
Shuai Li ◽  
Zehui Shao ◽  
Lina Ni
Keyword(s):  
Time Varying ◽  
Square Root ◽  
Root Finding ◽  
Matrix Square Root ◽  
Non Linear ◽  
Noise Tolerant
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