Nonlinear gust loads analysis - Monte Carlo vs. describing function analysis

1979 ◽  
Author(s):  
R. STAPLEFORD ◽  
R. DIMARCO
Keyword(s):  
Monte Carlo ◽  
Function Analysis ◽  
Describing Function ◽  
Loads Analysis ◽  
Gust Loads

Derivation of Forcing Functions for Monte Carlo Atmospheric Gust Loads Analysis

1999 ◽  
Author(s):  
B. H. Sako ◽  
M. C. Kim ◽  
A. M. Kabe ◽  
W. K. Yeung
Keyword(s):  
Monte Carlo ◽  
Forcing Functions ◽  
Loads Analysis ◽  
Gust Loads

Evaluation of a Describing Function Approach to Nonlinear Gust Loads Analysis

1980 ◽  
Vol 17 (2) ◽  
pp. 87-94 ◽  
Author(s):  
Robert L. Stapleford ◽  
Richard J. DiMarco
Keyword(s):  
Function Approach ◽  
Describing Function ◽  
Loads Analysis ◽  
Gust Loads

scholarly journals An optical observational cluster mass function at z ∼ 1 with the ORELSE survey

2021 ◽  
Vol 502 (3) ◽  
pp. 3942-3954
Author(s):  
D Hung ◽  
B C Lemaux ◽  
R R Gal ◽  
A R Tomczak ◽  
L M Lubin ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Large Scale ◽  
Near Infrared ◽  
Function Analysis ◽  
Voronoi Tessellation ◽  
Cosmological Parameters ◽  
Mass Range ◽  
Mass Function ◽  
Cluster Mass ◽  
Theoretical Mass

ABSTRACT We present a new mass function of galaxy clusters and groups using optical/near-infrared (NIR) wavelength spectroscopic and photometric data from the Observations of Redshift Evolution in Large-Scale Environments (ORELSE) survey. At z ∼ 1, cluster mass function studies are rare regardless of wavelength and have never been attempted from an optical/NIR perspective. This work serves as a proof of concept that z ∼ 1 cluster mass functions are achievable without supplemental X-ray or Sunyaev-Zel’dovich data. Measurements of the cluster mass function provide important contraints on cosmological parameters and are complementary to other probes. With ORELSE, a new cluster finding technique based on Voronoi tessellation Monte Carlo (VMC) mapping, and rigorous purity and completeness testing, we have obtained ∼240 galaxy overdensity candidates in the redshift range 0.55 < z < 1.37 at a mass range of 13.6 < log (M/M⊙) < 14.8. This mass range is comparable to existing optical cluster mass function studies for the local universe. Our candidate numbers vary based on the choice of multiple input parameters related to detection and characterization in our cluster finding algorithm, which we incorporated into the mass function analysis through a Monte Carlo scheme. We find cosmological constraints on the matter density, Ωm, and the amplitude of fluctuations, σ8, of $\Omega _{m} = 0.250^{+0.104}_{-0.099}$ and $\sigma _{8} = 1.150^{+0.260}_{-0.163}$. While our Ωm value is close to concordance, our σ8 value is ∼2σ higher because of the inflated observed number densities compared to theoretical mass function models owing to how our survey targeted overdense regions. With Euclid and several other large, unbiased optical surveys on the horizon, VMC mapping will enable optical/NIR cluster cosmology at redshifts much higher than what has been possible before.

Characterization and Attenuation of Sandwiched Deadband Problem Using Describing Function Analysis and Its Application to Electro-Hydraulic Systems Controlled by Closed-Center Valves

2004 ◽  
Author(s):  
Song Liu ◽  
Bin Yao
Keyword(s):  
Closed Loop ◽  
Controller Design ◽  
Function Analysis ◽  
Nonlinear Behavior ◽  
Hydraulic Systems ◽  
Describing Function ◽  
Widespread Application ◽  
Actuator Dynamics ◽  
Loop Bandwidth ◽  
Highly Nonlinear

Sandwiched deadbands can be seen in a wide variety of systems, such as electro-hydraulic systems controlled by closed-center valves. In such a system, the deadband is between the plant and actuator dynamics and therefore can not be compensated directly like an input deadband. Though this sandwiched deadband problem may be attenuated to certain degree through sophisticated advanced control techniques, the increased cost and the necessity of actuator state feedback prohibit their widespread application in the industry. An economical and popular method is to add an inverse deadband function in the controller to cancel or compensate the highly nonlinear behavior of the deadband. However, such a solution requires that the dynamics before the deadband (eg. the valve dynamics) is fast enough to be neglected — a requirement that can not be met in reality unless the closed loop bandwidth of the overall system is limited very low. To raise the achievable closed loop bandwidth for a much improved control performance, it is essential to be able to precisely characterize the effect of this sandwiched deadband on the stability and performance of the overall closed-loop system, which is the main focus of the paper. Specifically, a describing function based nonlinear analysis will be conducted to predict when the instability will occur and how the resulting limit cycle depends on the actuator dynamics and the targeted closed-loop bandwidth. Based on the analysis, the optimal closed-loop bandwidth can be determined to maximize the achievable overall system performance. The technique is applied to an electro-hydraulic system controlled by closed-center valves to optimize the controller design.

Modelling and performance of a pneumatic brake actuator

2011 ◽  
Vol 226 (8) ◽  
pp. 2077-2092 ◽  
Author(s):  
Jonathan I Miller ◽  
David Cebon
Keyword(s):  
Time Delays ◽  
Function Analysis ◽  
The Novel ◽  
Performance Limits ◽  
Heavy Vehicles ◽  
Describing Function ◽  
One Dimensional ◽  
High Bandwidth ◽  
And Performance ◽  
Actuator Design

Heavy vehicles have sluggish pneumatic brake actuators that limit the control bandwidth of their anti-lock braking systems. In order to implement more effective braking controllers, it is proposed that high-bandwidth, binary-actuated valves are directly placed on the brake chambers. This article details investigations made into modelling and controlling heavy-vehicle pneumatic brake actuators with a view towards implementing the novel brake actuator design. One-dimensional flow theory is combined with simple thermodynamic arguments for polytropic systems to describe the charging and discharging of a brake chamber. Particular attention is paid to the simulation of perceptible vibrations caused by the piston’s motion at relatively low charging pressures, using a hysteresis model. The resulting equations are linearized and used to design a closed-loop pressure controller for the actuator. Finally, the non-linear performance limits of the valves, caused by dead-zones and time delays, are investigated using a describing function analysis.

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