FAST is an Arecibo type large radio telescope with 500 meters aperture reflector, which is composed of about 4600
triangle panels. The panels and back structures are installed on the spring cable meshes. FAST adopts the active
reflection structure to change the spherical difference, which will form a simultaneous parabola with aperture of 300
meters. To test the feasibility of this new type reflector structure, a FAST model of 30 meters aperture was constructed in
2005. In this paper, the structure of the model is introduced, which includes a circle supporting girder of 30 meters in
diameter, 252 panel back structures, 472 main cables, and 145 sets of control cables, nodes, actuators and anchors. The
structural design and analysis are processed for these compositions, and the test results of the model reflector are given.
The work of the paper will provide a significant reference for the primary design of FAST reflector.
Operation of the Five-Hundred-Meter Aperture Spherical Telescope (FAST) requires accurate positioning and movement
of the receiver platform on a spherical workspace with a radius of 160 m. Supported above the 500 m diameter main
reflector it has to be positioned with an accuracy of several millimeters. To achieve this, the receiver is located in the
receiver cabin that is suspended on six cables. The cables are attached to six towers located on the circumference of the
main reflector and can be actuated via six capstans. In this paper a control concept for the cable-system is presented.
Using a detailed mathematical model of the system the performance of the control and the sensitivity to wind and other
disturbances is evaluated via simulation. The mechanics are modeled via FEM, the capstan-drives as lumped-mass
elements including nonlinear effects like friction and backlash. The control scheme presented consists of position control
loops for the capstans and numerically optimized PID-controllers for the positioning of the cabin platform.
The reflector of FAST (Five-hundred-meter Aperture Sphere Telescope) is a net mesh structure and can be considered as
a flexible parallel motion mechanism array which can form the varying paraboloid surface by controlling the motion of
the net mesh nodes. As a parallel mechanism, the motion of the nodes are coupled together. In order to release the
coupling, or to estimate the surface error of the reflector, the motion of FAST 30m Model was simulated combined with
ADAMS and SIMULINK. The net mesh mechanism was modeled as springs and spheres with mass in ADAMS software.
To control the large amount of actuators, and to analyze the motion of the net mesh motion mechanism, a control model
in SIMULINK has been built, which includes astronomical plan, actuator controlling and surface analysis. The model
can be used as the test tool of the actuator control strategy and optimization for the net mesh structure. With the
combined simulation, the amount of the couple phenomenon is estimated precisely. The paraboloid shape forming and
moving in the observing course is simulated, and the variation of the surface error of the reflector and the forces of each
cable are given. By the simulation, it can be concluded that the couple effect is small in the FAST 30m Model, and such a
method can be applied to the FAST prototype.
The National Astronomical Observatories of China (NAOC) plan to build a 500m radio telescope in southern China .
The telescope has a fixed but active main reflector, and large sky coverage is achieved by moving the receivers on a
focus surface 160m above the main reflector. The paper describes recommended design concepts for the cable system,
the drives and the cabin mechanisms, which position and point the receiver platform. The simulation study, which is
basis of the presented results, was executed by engineers of the Technical University Darmstadt under a contract of
NAOC in cooperation with two visiting engineers of NAOC and lead by the author . The analysis results and end-toend
simulations itself are described in more detail in two other contributions to this conference , .
This paper devotes to the working space analysis of the main positioning system of FAST cabin suspension, a
flexible-cable-driven parallel manipulator. The problem formulation is deduced through equilibrium analysis of the cabin
platform and suspension cables, which changes subsequently into a nonlinear constrained optimization intending a
uniform allocation of the six cable tension force. The analysis verifies the accessibility of focus cabin to the whole focus
surface. The optimization investigates the orientation of the focus cabin under equilibrium and the optimal cable forces,
as well as elaborates their importance in the finite element modeling of the cable-cabin system and the respective layout
designs of the rotator, Stewart stabilizer and capstan motors. In the end, the influences of the tower height and the
position of mass center of the focus cabin on the optimization results are discussed.
FAST is an Arecibo-type antenna with 3 outstanding aspects: the unique karst depression as the site; the active main
reflector which corrects spherical aberration on the ground to achieve full polarization and wide band without involving
complex feed system; and the light focus cabin driven by cables and servomechanism plus a parallel robot as secondary
adjustable system to carry the most precise parts of the receivers. These design features will enable FAST to jumpstart
many of science goals, such as HI neutral hydrogen line survey, pulsar survey, largest station in VLBI network, spectral
line observations and Search for alien's technologies. The feasibility studies for FAST have been carried out for 14 years,
being supported by Chinese and world astronomical communities. Funding for Project FAST has been approved by the
National Development and Reform commission NDRC in July of 2007 with a capital budget ~ 600 millions RMB and a
project time of 5.5 years from the foundation.
FAST (Five-hundred-meter Aperture Spherical radio Telescope) focus cabin is driven by 6 cables, moving on a
spherical cap of ~ 206 meters in diameter. In order to achieve the required pointing accuracy of the telescope by
positioning and orienting the receiver properly, X/Y positioner and Stewart manipulator are employed. In addition,
reaction mass dampers (RMD) are investigated to depress the cabin's vibrations at high frequencies.
In this paper, a simulation model of FAST focus cabin is created. Control simulation is carried out to evaluate
control performance of the focus cabin. As a result of this simulation work, X/Y positioner, Stewart manipulator and
reaction mass dampers show satisfied performance in compensating the residual position and orientation errors and
depressing vibrations. The simulation work approves the feasibility of this engineering concept, and also paves an
efficient approach for optimization in the future design work.
The metrology system to measure position and orientation of the cabin for FAST model consists of three Leica laser total stations. An innovative way was involved to test the performance of the metrology system. Large numbers of experiment data were obtained, including 116 groups of dynamic data and 62 groups of static data. There are many problems to be solved from experiment. 240ms delay time was found and characteristic frequency was detected. The dynamic capability of this metrology system was tested. The metrology system will work in the quasi static in FAST and FAST down scale model.The static position RMS error is less than 0.4mm and orientation RMS error less than 0.08°. Results of the total station examination indicate that this system can meet the requirement of the model. In spite of some dissatisfactory aspects, e.g. sampling rate, the total station will play an important role in the FAST.
As part of a major enhancement, designated e-MERLIN, to its MERLIN array of radio telescopes there is a need for new feed designs to cover 4GHz to 8GHz band, for large paraboloid dishes (up to 76 m etres diameter) operating in both prime-focus and cassegrain configurations. The requirement, in each case, for good return loss and constant beam width across an octave band, presents a set of difficult challenges. The feed designs for e-MERLIN are introduced here. The prototypes of the prime-focus feeds and the e-system corrugated horn feed have been designed, manufactured and tested, both in the laboratory and on the respective telescope. The complete corrugated horn for the Cambridge telescope will shortly be manufactured and measured.
Newly developed method and technology for determining the spatial position of the feeds of the FAST are introduced in this paper. Base on the measurements of the position and orientation of cabin in which the feeds are mounted, a loop feedback control enables accurately driving the feeds along desired tracks. The key technique of this implementation is the precise measurement of 6-freedom coordinates of the cabin in air with high sampling rate. An innovated way for this purpose is put forward and tested, combining data by different type of sensors. The errors of measurements and their influences on the control accuracy are analyzed theoretically, and checked by model tested. The experiment shows the feasibility and effectivity of the scheme of measurement and control for the telescope.
The collecting area of a radio telescope is a figure of merit of that instruments's capability. A Five hundred meter Aperture Spherical Telescope (FAST) is proposed to be built in the unique karst area of southwest China, and will act, in a sense, as a prototype for the Square Kilometer Array (SKA). It will be over twice as large as Arecibo coupled with much wider sky coverage. Some results from site surveys for such a SKA concept are briefly reported. Technically, FAST is not simply a copy of the existing Arecibo telescope but has rather a number of innovations. Firstly, the proposed main spherical reflector, by conforming to a paraboloid of revolution in real time through actuated active control, enables the realization of both wide bandwidth and full polarization capability while using standard feed design. Secondly, a feed support system which integrates optical, mechanical and electronic technologies will effectively reduce the cost of the support structure and control system. With an overall diameter of 500 m and radius of its spherical surface of 300 m, FAST will be the world's largest single dish.