scholarly journals Modelling and simulation studies on adaptive controller for alt-azimuth telescopes despite unknown wind disturbance and mass

2020 ◽  
Vol 12 (9) ◽  
pp. 168781402095476
Author(s):  
Onur Keskin ◽  
Ali Cem Unal ◽  
Gokhan Kararsiz ◽  
Tugrul Yilmaz ◽  
Cahit Yesilyaprak
Keyword(s):  
Adaptive Controller ◽  
Wind Gust ◽  
Simulation Studies ◽  
Wind Disturbance ◽  
Wind Model ◽  
Lyapunov Approach ◽  
Wind Speeds ◽  
Unknown Phase ◽  
Different Seasons ◽  
Phase Amplitude

Numerous ground-based observatories are using small sized ground telescopes for scientific research purposes. The telescopes that are available on the market have three main problems. These issues can be listed as: positioning repeatability, tuning requirement according to different wind speeds for different seasons, and the mass changing via different scientific equipments added to the telescope. This study is aimed at resolving these issues for ground based small alt-azimuth telescopes. Establishing of a set and forget system is performed by designing an adaptive controller. Motor dynamics are taken into consideration for a realistic mathematical model. The Wind-Gust model that consists of a sum of sinusoidal disturbances with unknown phase, amplitude and frequency is used for the wind model. The purposed controller cancels the disturbance effects on the plant while operational positioning and also the makes the plant insensitive to mass changes. The Lyapunov approach is utilised when proving the asymptotic stability. The proposed controller’s success is illustrated with thorough numerical evaluation.

scholarly journals WIND DISTURBANCE CANCELLATION FOR SMALLER ALT-AZIMUTH TELESCOPES

2021 ◽  
Vol 53 ◽  
pp. 29-34
Author(s):  
A. C. Unal ◽  
G. Kararsiz ◽  
C. T. Yilmaz ◽  
O. Keskin ◽  
C. Yesilyaprak
Keyword(s):  
Mathematical Model ◽  
Asymptotic Stability ◽  
Numerical Study ◽  
Adaptive Controller ◽  
Wind Gust ◽  
Wind Disturbance ◽  
Lyapunov Approach ◽  
Unknown Amplitude ◽  
Disturbance Cancellation ◽  
The Mathematical Model

This study focuses on eliminating unknown amplitude wind disturbance for 2-DOF alt-azimuth configuration small telescopes. An adaptive controller is designed to overcome wind disturbance as a set and forget system. The mathematical model is derived based on 2-DOF alt-azimuth configuration. The wind disturbance is modeled as a sum of sinusoidal with unknown amplitude, frequency and phase by using Wind-Gust model. The controller aims to cancel the effect of the disturbance on the altitude and azimuth angles of the telescope while positioning or staying static on a dedicated configuration. The asymptotic stability is proven with the Lyapunov approach. The numerical study is illustrated to success of the proposed controller.

Simulation Studies on Model Reference Adaptive Controller for Permanent Magnet Synchronous Motor Drive

2011 ◽  
Vol 268-270 ◽  
pp. 509-512 ◽  
Author(s):  
Zhi Yong Qu ◽  
Zheng Mao Ye
Keyword(s):  
Permanent Magnet ◽  
Permanent Magnet Synchronous Motor ◽  
Adaptive Controller ◽  
Fast Response ◽  
Synchronous Motor ◽  
System Stability ◽  
Motor Drive ◽  
Simulation Studies ◽  
The Stability ◽  
Model Reference Adaptive

Permanent magnet synchronous motor systems are usually used in industry. This kind of systems is nonlinear in nature and generally difficult to control. The ordinary linear constant gain controller will cause overshoot or even loss of system stability. Application of adaptive controller to a permanent magnet synchronous motor system is investigated in this paper. The dynamic model of the system is given and the stability is also analyzed using Popov's criterion. The steady state error can be eliminated using adaptive controller combined with an integration term. Simulation results show the performance of adaptive controller with fast response and less overshoot.

scholarly journals An overview of various kinds of wind effects on unmanned aerial vehicle

2019 ◽  
Vol 52 (7-8) ◽  
pp. 731-739 ◽  
Author(s):  
Bo Hang Wang ◽  
Dao Bo Wang ◽  
Zain Anwar Ali ◽  
Bai Ting Ting ◽  
Hao Wang
Keyword(s):  
Unmanned Aerial Vehicle ◽  
Great Influence ◽  
Wind Disturbance ◽  
Wind Fields ◽  
Wind Model ◽  
Aerial Vehicle ◽  
Low Altitude ◽  
The Stability ◽  
The Mathematical Model ◽  
Vehicle Movement

Attitude, speed, and position of unmanned aerial vehicles are susceptible to wind disturbance. The types, characteristics, and mathematical models of the wind, which have great influence on unmanned aerial vehicle in the low-altitude environment, are summarized, including the constant wind, turbulent flow, many kinds of wind shear, and the propeller vortex. Combined with the mathematical model of the unmanned aerial vehicle, the mechanism of unmanned aerial vehicle movement in the wind field is illustrated from three different kinds of viewpoints including velocity viewpoint, force viewpoint, and energy viewpoint. Some simulation tests have been implemented to show the effects of different kinds of wind on unmanned aerial vehicle’s path and flight states. Finally, some proposals are presented to tell reader in which condition, which wind model should be added to simulation, and how to enhance the stability of unmanned aerial vehicle for different kinds of wind fields.

Modelling and Adaptive Control of Tendon-Driven Micromanipulators in the Presence of Van-der-Waals Forces

2004 ◽  
Author(s):  
Athanasios Tsoukalas ◽  
Anthony Tzes
Keyword(s):  
Adaptive Control ◽  
Design Problem ◽  
Van Der Waals ◽  
Adaptive Controller ◽  
Simulation Studies ◽  
Unknown Parameters ◽  
Actuation Mechanism ◽  
Control Scheme ◽  
Driven System ◽  
Adaptive Control Scheme

In this article, the design problem of an adaptive controller for a robotic micromanipulator, including the effects of the applied Van der Waals (VdW) forces is considered. The micro-manipulator’s dynamic model is appropriately modified in order to include the interaction of the attractive VdW-forces. Inhere, every link is decomposed into a series of elementary particles (e.g. spheres), each one interacting with the robot’s neighboring objects during its motion. This interaction induces nonlinear additive terms in the model, attributed to the overall effect of the VdW-forces. The actuation is achieved by a tendon-driven system. At each joint, a pair of tendons is attached and act in an almost passive antagonistic manner. The kinematic and dynamic analysis of the tendon-driven actuation mechanism is offered. Consequently, the microrobot’s model is shown to be linearly parameterizable. Subject to this observation, a globally stabilizable adaptive control scheme is derived, estimating the unknown parameters (masses, generalized VdW-forces) and compensating any variations of those. Simulation studies on a 2-DOF micro-manipulator are offered to highlight the effectiveness of the proposed scheme.

Dynamic Response Analysis of a Spar Platform Subjected to Wind and Wave Forces

2008 ◽  
Author(s):  
Bernt J. Leira ◽  
Dag Myrhaug ◽  
Jarle Voll
Keyword(s):  
Dynamic Response ◽  
Roughness Parameter ◽  
Response Analysis ◽  
Wave Forces ◽  
Wind Gust ◽  
Wave Age ◽  
Spar Platform ◽  
Dynamic Response Analysis ◽  
Wind Speeds ◽  
Wind Response

Results from a study on dynamic response analysis of a floating production unit (FPSO) excited by wave and wind forces are presented. The FPSO is examplified by a Spar platform considering the motion in surge and pitch. The wind gust is modelled with the Harris [4] and Ochi and Shin [7] wind gust spectra. The effect of the wave age on the wind gust spectrum is included by adopting the Volkov wave age dependent sea surface roughness parameter [10]; the wave age independent Charnock roughness parameter [2] is also used as a reference. Examples of results demonstrate clear effects of wave age on the dynamic response. Moreover, for high mean wind speeds the total wind response is much smaller than the wave response, but for low mean wind speeds the wind appears to be more important.

Dynamic Response of Articulated Tower Platforms to Random Sea Environment

2009 ◽  
Author(s):  
Mohd Moonis Zaheer ◽  
Nazrul Islam
Keyword(s):  
Dynamic Response ◽  
Excitation Frequency ◽  
Response Analysis ◽  
Wave Forces ◽  
Wind Gust ◽  
Wave Age ◽  
Wind Speeds ◽  
Positive Side ◽  
The Mean ◽  
Low Wind Speeds

Articulated tower motions have been characterized by rigid body mode of vibrations falling in the wind excitation frequency range due to its compliant nature. Dynamic response analysis of a multi hinged articulated tower platform to random wind and wave forces are presented in this paper. The wave forces on the submerged elements of the tower are calculated by using Morison’s Equation. The fluctuating wind is modeled with Ochi and Shin wind gust spectrum. The effect of wave age (young, intermediate and fully developed waves) on the wind gust spectrum is incorporated by adopting the wave age dependent Volkov, and wave age independent Charnock sea surface roughness models. The response of the tower is determined by a time domain iterative method. An example of results demonstrates the clear effect of wave age on the nonlinear dynamic response on the system. The mean wind modifies the mean position of the surge response to the positive side, causing an offset. Moreover, for high mean wind speeds the total wind response is much smaller than the wave response, but for low wind speeds the wind appears to be more important.

scholarly journals Observational Analysis of a Wind Gust Event during the Merging of a Bow Echo and Mini-Supercell in Southeastern China

Atmosphere ◽  
2021 ◽  
Vol 12 (11) ◽  
pp. 1511
Author(s):  
Hui Zheng ◽  
Yuchun Zhao ◽  
Yipeng Huang ◽  
Wei Zhang ◽  
Changrong Luo ◽  
...  
Keyword(s):  
Convective Cell ◽  
Cyclonic Circulation ◽  
Wind Gust ◽  
Southeastern China ◽  
Wind Speeds ◽  
Significant Damage ◽  
Bow Echo ◽  
Layer 4 ◽  
Surface Station ◽  
Differential Reflectivity

The merging of a fast-moving bow echo with a convective cell of a hook-echo signature was studied by using polarimetric radar detections. Gusts with wind speeds near 35 m s–1 were recorded by the surface station, which caused significant damage. A convective cell with a mesovortex signature, which is hereafter referred to as a mini-supercell, was observed over the northeast of the bow echo before the convective merging. It was found that the mesovortex possessed cyclonic circulation and resembled a supercell-like feature. The merging of the bow echo and the mini-supercell strengthened the updraft near the apex of the bow echo. The enhanced updraft was also demonstrated by the appearance of a differential reflectivity (ZDR) column with a topmost height of 4 km above the melting layer (~4 km). The bow was separated into northern and southern sectors after merging with the mini-supercell, leading to the gusty wind over the surface of the south sector.

scholarly journals Modelling winter storm impacts on insured claim ratios of residential buildings in German administrative districts

2021 ◽  
Author(s):  
Andreas Trojand ◽  
Nico Becker ◽  
Henning Rust
Keyword(s):  
Urban Areas ◽  
Linear Models ◽  
Mean Squared Error ◽  
Residential Buildings ◽  
Daily Maximum ◽  
Wind Gust ◽  
Loss Ratio ◽  
Winter Storms ◽  
Wind Speeds ◽  
Link Functions

<p>Severe winter storms are one of the most damaging natural hazards for European residential buildings. Previous studies mainly focused on the loss ratio (loss value / total insured sum) as a monetary value for damages. In this study the focus is on the claim ratio (number of claims / number of contracts), which is derived from a storm loss dataset provided by the German Insurance Association. Due to its magnitude, the claim ratio might be a more intuitive parameter for the use in impact-based warnings than the loss ratio.</p><p>In a first step, loss ratios and claim ratios in German administrative districts are compared to investigate differences and similarities between the two variables. While there is no significant change in the ratio between claim ratio and loss ratio with increasing wind speeds, a tendency for lower loss ratios in urban areas can be confirmed.</p><p>In a second step, a generalized linear model for daily claim ratios is developed using daily maximum wind gust (ERA5) and different non-meteorological indicators for vulnerability and exposure as predictor variables. The non-meteorological predictors are derived from the Census 2011. They include information about the district-average construction years, the number of apartments per buildings and others to get a better understanding of these factors concerning the number of buildings affected by windstorms. The modelling procedure is divided into two steps. First, a logistic regression model is used to model the probabilty claim ratios larger than zero. Second, generalized linear models with different link functions are compared regarding their ability to predict claim ratios larger than zero. In a cross-validation setting a criteria for model selection is implemented and the models of both steps are verified. Both steps show an improvement over the climatological forecast and in both cases the addition of data for vulnerability and exposure leads to in decrease of the mean squared error. </p>

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