KEYWORDS: Sensors, Telescopes, Active optics, Astronomical telescopes, James Webb Space Telescope, Mirrors, Segmented mirrors, Space telescopes, Inductance, Large telescopes
Edge sensor is one of the most important technologies for the extremely large segmented primary telescopes like Keck, Thirty Meter Telescope (TMT), European Extremely Large Telescope (E-ELT) and Chinese Future Giant Telescope (CFGT) for control of out-of-plane degrees of freedom. Different from the capacity edge sensor from Keck and TMT, one kind of an inductance edge sensor is proposed and applied with the similar principle and configuration, fine aligned and tested in this paper to try to realize the same co-focusing or co-phasing maintenance purpose and high accuracy of relative piston and tip/tilt degrees of freedom of the segments. The sensor is also considered and modified to much more sensitive to dihedral angle between the neighboring segments. Finally some preliminary conclusions are reached.
KEYWORDS: Sensors, Active optics, James Webb Space Telescope, Telescopes, Space telescopes, Mirrors, Actuators, Segmented mirrors, Image segmentation, Astronomical telescopes
Extremely large telescopes with more and more large apertures are pursued, proposed and constructed by astronomers and technicians all over the world in the coming next years to satisfy the great demand of scientific progress. Segmented mirror active optics is the most important technology to co-phase the large primary for optically perfect segmentation. Based the experimental platform and test work in Nanjing Institute of Astronomical Optics and Technology in China, we introduce the latest co-phasing progress on fine segment support, edge sensor and close-loop co-phasing correction in China in this paper. Finally some conclusions are given based on the test results.
The real-time maintenance sensor for the active reflector is one of the key technologies for the active reflector upgradation plan of 13.7m millimeter radio telescope from Purple Mountain Observatory, China. A new type of maintenance integration sensor based on PSD and laser module based on normal angle and distance detection is proposed in this paper. After the brief introduction of the maintenance theory of the radio telescope segmented primary reflector, the method is simulated and tested on the real backup panel from the telescope in the active reflector lab in Nanjing Institute of Astronomical Optics and Technology, China. The method is proved to be a high accurate, engineering feasible for that real-time maintenance of the whole primary. Finally some conclusions are reached.
An active reflector is one of the key technologies for constructing large telescopes, especially for the
millimeter/sub-millimeter radio telescopes. This report presents a new and substantial progress on the efficient laser
angle metrology system for the active reflector antenna of the large radio telescopes, with a plenty of experiments based
on a four-panel prototype system constructed by Nanjing Institute of Astronomical Optics and Technology (NIAOT).
The test results prove that this technology is workable for sub-millimeter radio telescopes both in accuracy and
time-response. Thus it can be applied to the reconstruction of the active reflector antenna in China and play a central role
in promoting the new area of sub-mm radio astronomy.
The reflector deformation caused by gravity, temperature, humidity, wind loading and so on can reduce the global
performance of a large radio telescope. In this paper, considering the characteristics of the primary reflector of a 13.7 m
millimeter-wave telescope a novel reflector adjustment method based on active optics has therefore been proposed to
control the active surface of the reflector through the communication between the active surface computer and embedded
intelligent controller with a large quantity of displacement actuators, in which the active surface computer estimates and
controls the real time active surface figure at any elevation angle, reduces or eliminates the adverse effects of the
reflector deformation to increase the resolution and sensitivity of the radio telescope due to the more radio signals
collected. A Controller Area Network /Ethernet protocol converter is designed for the communication between the active
surface control computer as a host computer in Ethernet and the displacement actuator controller in Controller Area
Network. The displacement actuator is driven by a stepper motor and controlled by an intelligent controller with the data
from the active surface computer. The closed-loop control of the stepper motor improves the control accuracy greatly
through the feedback link based on the optical encoder.
A telescope with a larger primary mirror can collect much more light and resolve objects much better than one with a
smaller mirror, and so the larger version is always pursued by astronomers and astronomical technicians. Instead of using
a monolithic primary mirror, more and more large telescopes, which are currently being planned or in construction, have
adopted a segmented primary mirror design. Therefore, how to sense and phase such a primary mirror is a key issue for
the future of extremely large optical/infrared telescopes. The Dispersed Fringe Sensor is a non-contact method using
broadband point light sources and it can estimate the piston by the two-directional spectrum formed by the transmissive
grating's dispersion and lenslet array. In this paper we introduce you the current research progress of the successful
design, construction and alignment of our dispersed Hartmann sensors together with its design principles and simulations
for indoor segmented mirror experiment system and outdoor segmented mirror experiment system. We also conduct
many successful real phasing tests and phasing corrections in the visible waveband using our existing indoor and outdoor
segmented mirror optics platform. Finally, some conclusions are reached based on the test and correction of experimental
results.
The Delingha 13.7-m radio telescope is to be upgraded with an active surface for multi-beam observation at 3 mm
wavelength. Its primary reflector is paved with 72 aluminum panels which are originally supported by 480 fixtures. One
of the critical tasks associated with the upgrade program is development of precision linear displacement actuators to
replace the panel fixtures hence to Listed first in the upgrade program is actively drive and position the panels. The linear
actuator is required to fit the existing positions, dimensions and connections of the panels and the backup structure, also
implicitly required to be as compact and lightweighted as possible. This paper is to report in detail the development and
experiment of the compact, folded, precision linear actuator according to given technique requirements and constraints,
including the description of the flexible adaption of the fixture of the actuators and the special design of the connecting
mechanism with the panels. The experiment system is established with one of the spare panels of the telescope, and six
sets of actuator and control electronics are included for driving the panel. This paper will present the test results
measured on a single actuator prototype as well as the actuators working together in the spare panel experiment. The test
results prove that the actuator manifests positioning accuracy of microns and load capacity of 12 kg. The related
connection and electronics design of the actuator also meets the requirements of the update program of the telescope.
An upgrade program is proposed for the Delingha 13.7-m radio telescope to implement active surface for multi-beam
observation at 3 mm wavelength. The upgrade involves three critical development aspects. One is the displacement
actuator, which must fit the existing position, space and connections of the panels and backup structure, meanwhile, must be as compact and lightweighted as possible. The second is that a new sub-reflector is necessitated by the multi-beam observation, where a new hyperbolic surface figure is optimized. The third, more crucial and difficult, is to realize active control of the actuators and real-time closed-loop of the full active surface. This paper is to present the progress of the development work, test and experiments associated with the three areas. With one of the spare panels of the telescope, an experiment system is carried out with six sets of actuator and control electronics. Another experiment system of a novel laser-based closed-loop measurement concept is also conducted with four smaller dummy panels. Both experiment setups have output expected results and further experiments are going on with them. In this paper, based on the two experiments, we will describe the special design and test of the actuator, including the design of its special mounting and connecting mechanisms. The design and manufacture and measurement of the new hyperbolic sub-reflector will be detailed as well as the principle, simulation and realization of the laser-based measurement system. Besides, the control strategy of the large scale use of the hundreds of actuators and EMI suppression are also covered.
A fast chopping secondary mirror is the critical functioning assembly in an astronomical telescope for infrared
observation. Normally, a chopping mirror is driven by precision high-load and high-stiffness linear actuators which are
expected to be lightweight, compact and further cost-effective. The stroke of the actuator is typically required to up to
several hundred microns with typical load capacity up to several hundred Newtons. We developed a novel piezo-based
prototype linear actuator with a two-stage rhombic flexure amplifier. In this paper, first we present the detail design
scheme of the actuator by analytical calculations with comprehensive Finite Element Analysis (FEA) verification.
Afterwards, we also present the procedures and results of tests of linearity, load capacity, eigenfrequency, stability and
repeatability. The selected piezoelectric drive unit is a block of 35x10x10 mm3 with output force up to 4000 N. The
two-stage displacement amplifier is simply integrated by two identical singular rhombic flexures orthogonally mounted
together. Each stage, one rhombic flexure with a longer axis of 76 mm long, is designed with an ideal amplification ratio
of 3, which leads to a final theoretical compound amplification ration of 9. In order to realize the basic
triangular-amplification principle in a rhombic flexure, we introduced flexure joints at all the eight ends of its four edge
bars. The singular rhombic flexures can be efficiently manufactured by electrical discharge wire-cutting process at a time
in batch by being overlapped in layers. Afterwards we carried out related measurements to test its performance.
Direct drive technology is the key to solute future 30-m and larger telescope motion system to guarantee a very high
tracking accuracy, in spite of unbalanced and sudden loads such as wind gusts and in spite of a structure that, because of
its size, can not be infinitely stiff. However, this requires the design and realization of unusually large torque motor that
the torque slew rate must be extremely steep too. A conventional torque motor design appears inadequate. This paper
explores one redundant unit permanent magnet synchronous motor and its simulation bed for 30-m class telescope.
Because its drive system is one high integrated electromechanical system, one complexly electromechanical design
method is adopted to improve the efficiency, reliability and quality of the system during the design and manufacture
circle. This paper discusses the design and control of the precise tracking simulation bed in detail.
KEYWORDS: Control systems, Telescopes, Space telescopes, Wireless communications, Control systems design, Prototyping, Telecommunications, Astronomical telescopes, Photogrammetry, Astronomy
Giant telescopes with extremely large aperture widely adopt segmented mirror active optics technology, so active
adjustment mechanism of displacement is one of the critical techniques. A novel 6-DOF mechanism featuring structural
compactness in size and partial decoupling in degrees has been proposed as a potential supporting mechanism for
sub-mirrors. It is of important significance to carry out profound study on the control strategy for large scale use of the
6-DOF adjustment mechanism in a highly segmented giant telescope. This paper presents first the control system design
for a prototype of the 6-DOF mechanism and further the control strategy modeling for the future large-scale application
of the mechanism in giant telescopes. The control system implemented for the prototype mechanism has been
successfully tested by photogrammetry at lab. It provides closed-loop control and real-time measurement of all motors of
one 6-DOF mechanism and is proved to be a system of high precision and efficiency. Afterwards, we explore and extend
the control design of the novel 6-DOF mechanism to large-scale use in all sub-mirrors in a giant telescope. The principle,
constitution, control algorithm and realization are covered and commented. The study and experiment carried out in this
paper are also informative for the control of parallel manipulators in other industries.
Radio telescopes with much more larger aperture collect much more signals and therefore sought after by astronomers.
The primary reflecting antenna is traditionally segmented and perfectly optically aligned at the central altitude among the
whole observation sky area for minimizing the gravitational deformation during operation and passively open-loop
maintained at any other altitude. A new laser segmentation sensing and maintaining method based on normal deflection
angle measurement is proposed in this paper. After the introduction of the theory, the method is simulated and tested on a
special prototype of radio panel segmentation system. It provides real-time monitoring and measurement of the global
segmentation status of all panels and is proved to be a high accurate, high efficient and low cost method. Finally several
conclusions are reached.
KEYWORDS: Control systems, Interferometers, Switches, Mirrors, Segmented mirrors, Control systems design, Optical isolators, Active optics, Optical calibration, Actuators
This paper mainly introduces hardware design and control method of the system which is used for detecting
the MA segmented mirrors in the LAMOST. According to the demand of sub-aperture stitching interferometer,
the system adopts a control card to control the stepping motor to drive the worktable moving on the X-Y. The
MA sub-mirror surface will be changed through active optical correction and add-subtract power of force
actuators. The detection result of the MA segmented mirror of 14 shows that root mean square (RMS) of
surface accuracy error is 21.387nm less than 0.035
λ(λ=632.8nm). It is demonstrated that the control system
can work very well and shorten the time of detection.
This paper presents an implementation of control system of position actuators in LAMOST. Performance of actuators
has been tested in laboratory. The resolution of actuators is less than 5nm. The whole control system has been
successfully realized in LAMOST MB pre-segmented experiment. The control system of position actuator adopts
distributed-and-centralized mode. Displacement RMS error of the control system (including actuator and electrical
control) is less than 50 nm.
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