A wideband signal upconversion and phase shifting scheme based on a frequency tunable optoelectronic oscillator (OEO) are proposed and demonstrated. The OEO performs simultaneously tunable high-quality local oscillator (LO) signal generation, wideband frequency upconversion, and phase shifting within the whole 2π range. With the generated LO tuning from 9.549 to 11.655 GHz, wideband square signals are successfully upconverted to the X band. The phase of the upconverted signal is tuned from 0 to 360 deg. The phase noise of the oscillation signal is about −104 dBc/Hz at 10 kHz offset with or without the injected baseband signal.
KEYWORDS: Field programmable gate arrays, Control systems, Telescopes, Large telescopes, Process control, Reliability, Astronomical telescopes, Interfaces, Human-machine interfaces, Software development
As the increasing size and more and more functions, modern telescopes have widely used the control architecture, i.e.
central control unit plus field controller. FPGA-based field controller has the advantages of field programmable, which
provide a great convenience for modifying software and hardware of control system. It also gives a good platform for
implementation of the new control scheme. Because of multi-controlled nodes and poor working environment in
scattered locations, reliability and stability of the field controller should be fully concerned.
This paper mainly describes how we use the FPGA-based field controller and Ethernet remote to construct monitoring
system with multi-nodes. When failure appearing, the new FPGA chip does self-recovery first in accordance with prerecovery
strategies. In case of accident, remote reconstruction for the field controller can be done through network
intervention if the chip is not being restored. This paper also introduces the network remote reconstruction solutions of
controller, the system structure and transport protocol as well as the implementation methods. The idea of hardware and
software design is given based on the FPGA. After actual operation on the large telescopes, desired results have been
achieved. The improvement increases system reliability and reduces workload of maintenance, showing good application
and popularization.
KEYWORDS: Control systems, Field programmable gate arrays, Astronomy, Control systems design, Telecommunications, Computing systems, Algorithm development, Logic, System on a chip, Large telescopes
As well-known, system on a programmable chip (SOPC) is widely used in a variety of field control systems , due to their
flexible configurations and intelligent stand-alone characteristics. They are also increasingly used in astronomical
instrument control nowadays. For those complex and diverse systems, a number of different control strategies are stored
in FLASH, but the controller of on-chip determines which one to load. At the same time, it can be switched
intelligently and remotely to form a multi-strategy control system, so as to extend the control functions and achieve
system on-line reconfiguration quickly. In this paper we describe a design concept and realization method of a multistrategy
control system on the basis of FPGA-based system on a chip. Its hardware core is Altera's Cyclone series
EP3C25 chip .In SOPC BUILDER development environment ,a control system is constructed, which consists of NIOS
II soft core as CPU ,REMOTE_UPDATE IP core and control algorithms as well. The concept and design has been
verified in the field controllers for various astronomical applications. Satisfactory results have been obtained.
KEYWORDS: Field programmable gate arrays, Control systems, Large telescopes, Computing systems, Telescopes, Telecommunications, Astronomy, Astronomical telescopes, Local area networks, Data communications
Modern telescopes usually have more controlled nodes than classical ones. Those nodes are separately distributed at
various locations of the instrument and not easy to access. While in adjustment, it always requires to modify the control
software, or sometimes to reform the hardware structure and to upgrade the related programs. To solve the problems of
renewing the field controllers, we introduce a FPGA based telescope controller system and a scheme for remoteupgrading
it via Ethernet. This paper mainly describes the structure of the field controller, the requirements for remoteupgrading
and system structure. Also discussed are the protocol applications and extensions, the processing methods as
well as the ideal of software design. The scheme has been in trial run for a large telescope with 16 field controller's subsystem
and excellent results were obtained. It may effectively solve the remote-upgrading problems for multiple field
controllers of large telescopes. Besides the scheme can be used in other multi-nodes industrial control systems too, which
is of high value in applications.
KEYWORDS: Wave plates, Control systems, Optical filters, Control systems design, Databases, Space telescopes, Interfaces, Logic, Solar telescopes, Optical components
Space Solar Telescope is one of the large-scale scientific programs under development in China. In it, an important part
is the filter, a birefringent filter with three-channels. It consists of 17 rotatable wave plates. In coordination with other
mechanical and optical components, complicated and precise adjustments of their attitudes are necessary, which requests
a high-accuracy control system to ensure their concertedness.
The paper describes the design and realization of the control system. It mainly has a hardware plate and a software one.
The former uses an industrial controller, a control card and step motors, while the latter uses the technique construction
of the object oriented. That is modularization design with lengthwise dividing as per functions and breadthwise dividing
as per element layers. Shift arithmetic for whole spectrum in programs is for intelligent spectral scanning. At the same
time, the control information is roundly recorded in the data base of the system.
Tests show that the system is characterized by high precision, good stabilization, high data safety and user-friendly
interface, totally meeting the design requirements.
Also discussed in this paper is some new conceivability to realize the handiness and miniaturization of the filter to fit the
use in space flight in the future.
KEYWORDS: Magnetism, Optical components, Polarizers, Space telescopes, Modulation, Control systems design, Polarization, Crystals, Modulators, Control systems
High precision magnetic analyzer is one of key points in technologies of Chinese space solar telescope, which is under pre-investigation. Magnetic analyzer needs a modulation component to change its polarization state. For ground-based use, usually electroptics crystal KD*P is a good option. However KD*P needs a power supply as high as thousands volts. In space environment, such a high pressure source is hardly available. Therefore we have to use an alternative, an optomechical modulator. In the modulator, the related optical components rotate precisely to realize modulation. This raises a crucial request for position accuracy and positioning times of optical components rotation. This paper describes our developing process of the electric control for the magnetic analyzer. Firstly, hardware facilities, control software design and test results as well are given. Then, some problems in manufacture and adjustment are analyzed and discussed. After overall optical, mechanical and electric tests, it shows that the accuracy of rotation position of the optical components is better than 10"(p-p) (checking with a precise 24 sides' standard); while time for rotating 90 degrees is less than 2 seconds. The results demonstrate that the magnetic analyzer has met the design requirements.
This paper introduces our control software design for a tracing system of precise pointing on a balloon-borne telescope to observe the active details on the solar surface. The telescope is an equatorial one with 80 cm in diameter. Borne by balloon, it works at 30 km above the sea level so as to get rid of the image disturbance due to atmosphere. The system contains three parts: basket control, telescope control and tip-tilt control. For telescope control, the crude sensors for pointing detection are two rotating transformers, while the fine sensors two linear CCDs which produce the error signals of pointing. An inserted-type industry-control computer PC104 completes the position close-loop and then drives the servo amplifiers to carry out pointing, searching and tracing automatically. Due to the fact that the position control loop is closed with an improved digital PID arithmetic, the adjustment of the telescope may respond rapidly, therefore the telescope can precisely follow the Sun on the balloon. Simulation test shows that the tracing accuracy may reach as high as 4" (RMS).
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