scholarly journals Considerate Regulation of Output Disturbances

Physics ◽  
2021 ◽  
Vol 3 (2) ◽  
pp. 173-187
Author(s):  
Eduard Eitelberg
Keyword(s):  
Feedforward Control ◽  
Low Frequency ◽  
High Gain ◽  
Phase Lag ◽  
Minimum Phase ◽  
Trade Off ◽  
Control Practice ◽  
Feedback Design ◽  
Loop Bandwidth ◽  
And Performance

Recently, I have considered a multi-variable feedforward control practice in a novel way being called “considerate control”. It was shown how the considerate control is related to Bristol gains, which indicate accurately either the required increase in input scope or the reduced output scope as compared to inconsiderate control. Here, considerate control is expanded to regulating control, necessitating some feedback design. Clearly, high-gain feedback leads to considerate control results in low frequency. Considerate pre-compensation decouples loops also at higher frequencies. However, as an analysis of the included examples demonstrates, such considerate design may insert non-minimum phase-lag into loops that did not have it, thus, reducing the loop bandwidth relative to that achievable in a skillful inconsiderate design, sometimes very significantly. As is often the case, there is a trade-off between consideration and performance.

Limits and Trade-Off in the Control of Compressor Surge

2002 ◽  
Author(s):  
Franco Blanchini ◽  
Pietro Giannattasio ◽  
Diego Micheli ◽  
Piero Pinamonti
Keyword(s):  
High Gain ◽  
Phase Lag ◽  
Low Frequencies ◽  
Trade Off ◽  
Numerical Studies ◽  
Compressor Surge ◽  
Negative Effect ◽  
Large Phase ◽  
System Output ◽  
Multistage Centrifugal Compressor

The present paper deals with several problems arising in the stabilisation of surge in compression systems. From a theoretical standpoint the system requires a high gain type controller to be stabilised. On the other hand, the real system is affected by persistent measurement noise whose negative effect on stability is strongly amplified by the high gain. Therefore, a suitable filtering of the system output is necessarily required. The bandwidth of the filter is subject to opposite constraints: if it is too large it affects the attenuation property; if it is too narrow, the large phase-lag introduced at low frequencies may compromise the system stabilisation, which requires a fast actuator reaction. This paper analyses all these aspects concurring in the stabilisation problem and the consequent trade-off in the control design. The results of experimental and numerical studies are provided with reference to the active control of surge in a multistage centrifugal compressor.

scholarly journals GRAM

2021 ◽  
Vol 18 (2) ◽  
pp. 1-24
Author(s):  
Nhut-Minh Ho ◽  
Himeshi De silva ◽  
Weng-Fai Wong
Keyword(s):  
Performance Improvement ◽  
Trade Off ◽  
Accuracy Requirement ◽  
Output Error ◽  
Fine Grain ◽  
Mixed Precision ◽  
And Performance ◽  
Effective Use

This article presents GRAM (<underline>G</underline>PU-based <underline>R</underline>untime <underline>A</underline>daption for <underline>M</underline>ixed-precision) a framework for the effective use of mixed precision arithmetic for CUDA programs. Our method provides a fine-grain tradeoff between output error and performance. It can create many variants that satisfy different accuracy requirements by assigning different groups of threads to different precision levels adaptively at runtime . To widen the range of applications that can benefit from its approximation, GRAM comes with an optional half-precision approximate math library. Using GRAM, we can trade off precision for any performance improvement of up to 540%, depending on the application and accuracy requirement.

Selecting packaging material for dry food products by trade‐off of sustainability and performance: A case study on cookies and milk powder

2021 ◽  
Vol 34 (5) ◽  
pp. 303-318
Author(s):  
Maarten Baele ◽  
An Vermeulen ◽  
Dimitri Adons ◽  
Roos Peeters ◽  
Angelique Vandemoortele ◽  
...  
Keyword(s):  
Milk Powder ◽  
Food Products ◽  
Packaging Material ◽  
Trade Off ◽  
Dry Food ◽  
And Performance

Ocean Response to Wind Variations, Warm Water Volume, and Simple Models of ENSO in the Low-Frequency Approximation

2010 ◽  
Vol 23 (14) ◽  
pp. 3855-3873 ◽  
Author(s):  
Alexey V. Fedorov
Keyword(s):  
Low Frequency ◽  
Equatorial Pacific ◽  
Warm Water ◽  
Water Volume ◽  
Thermocline Depth ◽  
Phase Lag ◽  
Eastern Equatorial Pacific ◽  
The Pacific ◽  
Warm Water Volume ◽  
Frequency Approximation

Abstract Physical processes that control ENSO are relatively fast. For instance, it takes only several months for a Kelvin wave to cross the Pacific basin (Tk ≈ 2 months), while Rossby waves travel the same distance in about half a year. Compared to such short time scales, the typical periodicity of El Niño is much longer (T ≈ 2–7 yr). Thus, ENSO is fundamentally a low-frequency phenomenon in the context of these faster processes. Here, the author takes advantage of this fact and uses the smallness of the ratio ɛk = Tk/T to expand solutions of the ocean shallow-water equations into power series (the actual parameter of expansion also includes the oceanic damping rate). Using such an expansion, referred to here as the low-frequency approximation, the author relates thermocline depth anomalies to temperature variations in the eastern equatorial Pacific via an explicit integral operator. This allows a simplified formulation of ENSO dynamics based on an integro-differential equation. Within this formulation, the author shows how the interplay between wind stress curl and oceanic damping rates affects 1) the amplitude and periodicity of El Niño and 2) the phase lag between variations in the equatorial warm water volume and SST in the eastern Pacific. A simple analytical expression is derived for the phase lag. Further, applying the low-frequency approximation to the observed variations in SST, the author computes thermocline depth anomalies in the western and eastern equatorial Pacific to show a good agreement with the observed variations in warm water volume. Ultimately, this approach provides a rigorous framework for deriving other simple models of ENSO (the delayed and recharge oscillators), highlights the limitations of such models, and can be easily used for decadal climate variability in the Pacific.

scholarly journals LMI Formulation for Static Output Feedback Design of Discrete-Time Switched Systems

2009 ◽  
Vol 2009 ◽  
pp. 1-7 ◽  
Author(s):  
Selma Ben Attia ◽  
Salah Salhi ◽  
Mekki Ksouri
Keyword(s):  
Discrete Time ◽  
Output Feedback ◽  
Small Degree ◽  
Switched System ◽  
Linear Matrix ◽  
Static Output Feedback ◽  
Additional Degree ◽  
Feedback Design ◽  
And Performance ◽  
Static Output

This paper concerns static output feedback design of discrete-time linear switched system using switched Lyapunov functions (SLFs). A new characterization of stability for the switched system under arbitrary switching is first given together with -performance evaluation. The various conditions are given through a family of LMIs (Linear Matrix Inequalities) parameterized by a scalar variable which offers an additional degree of freedom, enabling, at the expense of a relatively small degree of complexity in the numerical treatment (one line search), to provide better results compared to previous one. The control is defined as a switched static output feedback which guarantees stability and -performance for the closed-loop system. A numerical example is presented to illustrate the effectiveness of the proposed conditions.

Age and Performance Under Pressure

2012 ◽  
pp. 134-152 ◽  
Author(s):  
Harold O. Fried ◽  
Loren W. Tauer
Keyword(s):  
Correlation Coefficient ◽  
High Performance ◽  
Age Distribution ◽  
Mental Ability ◽  
Trade Off ◽  
Athletic Ability ◽  
Front End ◽  
Ladies Professional Golf Association ◽  
And Performance ◽  
Performance Under Pressure

This article explores how well an individual manages his or her own talent to achieve high performance in an individual sport. Its setting is the Ladies Professional Golf Association (LPGA). The order-m approach is explained. Additionally, the data and the empirical findings are presented. The inputs measure fundamental golfing athletic ability. The output measures success on the LPGA tour. The correlation coefficient between earnings per event and the ability to perform under pressure is 0.48. The careers of golfers occur on the front end of the age distribution. There is a classic trade-off between the inevitable deterioration in the mental ability to handle the pressure and experience gained with time. The ability to perform under pressure peaks at age 37.

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