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

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.The authors would like to thank the technical guidance and funding support of Isik University, Center for Optomechatronics Research and Application (OPAM),and Ataturk University Center for Astrophysical Application and Research (ATASAM). The author(s) received no financial support for the research, authorship, and/or publication of this article.Publisher's Versio

Wind disturbance cancellation for smaller alt-azimuth telescopes

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.Este estudio tiene como objetivo eliminar amplitudes desconocidas producidas como consecuencia de la perturbación del viento que afecta a las monturas altazimutales en pequeños telescopios. Se ha diseñado un controlador adaptativo para minimizar este efecto. El modelo matemático se basa en la configuración altazimutal con 2 grados de libertad, modelándose la perturbación inducida por el viento como una sinusoide con amplitud, frecuencia y fase desconocidas utilizando un modelo de viento más ráfaga. El controlador tiene como objetivo cancelar el efecto de la perturbación en los ángulos de altitud y azimut del telescopio mientras éste se posiciona o permanece estático en una configuración determinada. La estabilidad asintótica se demuestra con el enfoque de Lyapunov. El estudio numérico se muestra en relación al éxito del controlador propuesto.Publisher's Versio

Advances for the 4m DAG Telescope in Flange derotator

The purpose of this study is expressing advances in design stages for in flange optical field derotator system for 4 meters DAG Telescope. In-Flange Derotator KORAY (K-mirror OpticalRelAY) is designed, analysed and manufactured to meet the specifications of DAG telescope. DAG telescope, situated at Erzurum/Karakaya summit at 3150m altitude, is the first Turkish optical telescope with VIS(Visible) and IR (Infrared) observation capability. DAG, designed by Turkish engineers at FMV Isik University, is also the largest telescope (4m diameter) in Turkey and in European continent. Being one of the 2023 vision projects; the first light of DAG is expected to take place in 2021. This purpose brings some real-life challenges such as design limitations, material selection and electronic integration.Authors would like to thank Işik University, Ataturk University, ATASAM, OPAM, and the Ministry of Development for the funding and support (2011K120230).Publisher's VersionScopusAffiliation ID: 6001047

Adaptive backstepping approach for 2-DOF telescopes despite unknown wind disturbance

Small ground telescopes on the marked are widely used in many space observatories and scientific researches. There are three main problems in such telescopes; positioning of the focal point and the need of tuning for both different seasonal wind speeds and mass changes of the telescope arm. This study focuses on eliminating those problems for 2-DOF altazimuth configuration small telescopes. An adaptive controller is designed to create a set and forget system. The mathematical model of the telescope is derived based on RR type joint configuration. For a realistic approach, motor dynamics is considered in the mathematical model. The wind disturbance is modeled according to the Wind-Gust model which is a sum of sinusoidal with unknown amplitude, frequency and phase. The controller aims to cancel the effect of the disturbance on focal point of the telescope while positioning. The asymptotic stability is proven with the Lyapunov approach. The numerical study is illustrated to success of the proposed controller.ACKNOWLEDGMENT The authors would like to thank the technical and funding support of Isik University, Center for Optomechatronics Research and Application (OPAM), Ataturk University Center for Astrophysical Application and Research (ATASAM)Publisher's Versio

In Flange Derotator Design for the 4m DAG telescope

The field rotation effect can be described as observing the gyration of an object with the pupil of the Eastern Anatolian Observatory (DAG) telescope around the optical axis under the influence of the latitude of the observatory while the telescope is following that astronomical object. This is possible as a result of the alt-azimuthal mount of the telescope. (the orientation of the astronomical observed object, the parallactic angle, is defined as "q") Since the CCD has a low signal on noise ratio, it necessitates long integration time that can vary from a few minutes to hours. It is essential to correct and compensate the rotation of the optical field caused by the earth's rotation during the monitoring of the astronomical object. A (field) derotator is a class of devices that is used to correct the optical field rotation. In a telescope of a Ritchey-Chretien, Nasmyth configuration, the device must be integrated between the scientific instruments and the M3 mirror. The anastigmatic and the anachromatic features of this type of derotator is the main reason that it is chosen. These characteristics are provided by the K-Mirror design. The aim of this study is to evaluate the possibility to integrate the derotator in the central hole of the telescope fork and to evaluate the mechanical/optical features of the model.Authors would like to thank Isik University, ATASAM, Ataturk University, and the Ministry of Development for the funding and supportPublisher's Versio

Structural properties of cadmium selenide nanowires prepared by chemical bath deposition for the electrical and photosensitive characteristics of the p-Si/CdSe heterojunction

WOS:000590138400017Cadmium selenide (n-CdSe) thin films were grown on a silicon substrate with a polished surface and applied to the Schottky type device structure. The n-CdSe thin films produced depended on various deposition times at 70 degrees C by the use of the chemical bath deposition technique. XRD results show that the fabricated thin films consist of both cubic and hexagonal crystal systems. The morphology of CdSe was formed in nanograins and nanowire structures with respect to deposition times of 6 and 10 h, respectively. In addition to structural analysis of CdSe thin films, CdSe nanowires were used as an interfacial layer in a metal-semiconductor device to investigate its effects on the electrical and photosensitive characteristics of the device. As well as under forward bias current-voltage (I - V) conditions, the space charge limited current conduction behaviors were identified at low voltages. The results showed that the film produced at 10 h has a better performance compared to that produced at 6 h in terms of increased electric current.This study was supported by the Research Fund of Mersin University in Turkey with Project No. 2017-2-TP3-2593 and Toros University with Project No. 2020-MUH-AKH-01