Macro-Aerodynamics: – A Phenomenological Model of Highly Non-linear Aerodynamics

2002 ◽  
Author(s):  
David Nixon
2017 ◽  
Vol 40 (7) ◽  
pp. 2151-2166 ◽  
Author(s):  
Yong Li ◽  
Qingfeng Wang

Proportional pressure-reducing valves (PPRVs) are typical proportional valves widely used in the hydraulic industry because they are inexpensive, not prone to malfunction, easy to handle and service. However, they suffer from performance degradations due to the existence of dead zone and hysteresis. An effective control method should be developed to improve the performance of PPRVs, as their characteristics significantly affect the entire hydraulic system. This article focuses on high-performance pressure-tracking control of a PPRV with dead zone and hysteresis. A non-linear phenomenological model is put forward to describe the characteristics of dead zone and hysteresis, as well as dynamic behaviour of the PPRV. The proposed phenomenological model is described using an ideal third-order linear model preceded by a dead zone term and a hysteresis term. To handle parameter uncertainties and uncertain non-linearities in the phenomenological model, an adaptive robust controller is synthesized without constructing a dead zone inverse or hysteresis inverse. The developed controller guarantees bounded pressure-tracking error and precise steady-state tracking accuracy. Comparative simulations and experiments with different pressure trajectories are carried out to verify the effectiveness of the proposed method. Both simulation and experimental results show that with the proposed adaptive robust control (ARC) approach, the non-linear dead zone and hysteresis may be well compensated and improved pressure-tracking performance achieved.


Author(s):  
Mojtaba Farahi ◽  
Saeed Erfani

This paper is a summary of an attempt to provide a phenomenological model in order to capture the nonlinear behavior of bracing members. The result obtained from modeling of a bracing system with the aid of the phenomenological model is compared with the result of a test to investigate the accuracy of the investigated model. Furthermore, static non-linear analyses are performed on an inverted V-braced subassembly using the phenomenological model as well as a convenient physical theory model. According to this study, the proposed phenomenological model is capable to favorably capture the behavior of a brace member under a cyclic loading. Hence, it can be used in analytical models of structural lateral bracing systems to assess accurately the nonlinear behavior of these systems.


1967 ◽  
Vol 28 ◽  
pp. 105-176
Author(s):  
Robert F. Christy

(Ed. note: The custom in these Symposia has been to have a summary-introductory presentation which lasts about 1 to 1.5 hours, during which discussion from the floor is minor and usually directed at technical clarification. The remainder of the session is then devoted to discussion of the whole subject, oriented around the summary-introduction. The preceding session, I-A, at Nice, followed this pattern. Christy suggested that we might experiment in his presentation with a much more informal approach, allowing considerable discussion of the points raised in the summary-introduction during its presentation, with perhaps the entire morning spent in this way, reserving the afternoon session for discussion only. At Varenna, in the Fourth Symposium, several of the summaryintroductory papers presented from the astronomical viewpoint had been so full of concepts unfamiliar to a number of the aerodynamicists-physicists present, that a major part of the following discussion session had been devoted to simply clarifying concepts and then repeating a considerable amount of what had been summarized. So, always looking for alternatives which help to increase the understanding between the different disciplines by introducing clarification of concept as expeditiously as possible, we tried Christy's suggestion. Thus you will find the pattern of the following different from that in session I-A. I am much indebted to Christy for extensive collaboration in editing the resulting combined presentation and discussion. As always, however, I have taken upon myself the responsibility for the final editing, and so all shortcomings are on my head.)


Optimization ◽  
1975 ◽  
Vol 6 (4) ◽  
pp. 549-559
Author(s):  
L. Gerencsér

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