Qiming Wang

THE FIVE-HUNDRED-METER APERTURE SPHERICAL RADIO TELESCOPE (FAST) PROJECT

The Five-hundred-meter Aperture Spherical radio Telescope (FAST) is a Chinese mega-science project funded by the National Development and Reform Commission (NDRC). The National Astronomical Observatories of China (NAOC) is in charge of its construction and the subsequent operation. Upon its expected completion in September of 2016, FAST will surpass the 300-meter Arecibo and the 100-meter GBT in terms of absolute sensitivity in the 70 MHz to 3 GHz bands. In this paper, we report the current status, the key science goals, and the aspiration of its early sciences. A special emphasis is paid to its innovative fatigue-resistant fibers, which are critical for the control and data acquisition under the unique FAST design.

Kinematics, dynamics and dimensional synthesis of a novel 2-DoF translational manipulator

In the past few years, parallel manipulators have become increasingly popular in industry, especially, in the field of machine tools. In this paper, a novel 2-degree-of-freedom (DoF) parallel manipulator, which has two translational DoFs, is proposed. It is characterized by the fact that the output of the manipulator is two planar DoFs of a rigid body, while its orientation remains constant. The inverse and forward kinematics can be described in closed form. The velocity equation, singularity, and workspace of the manipulator are presented. In addition the inverse dynamics problem of the device is investigated employing the Lagrange multipliers approach. The dimensional synthesis based on the workspace and conditioning indices is presented. The proposed manipulator can be applied to the field of machine tools or used as the mobile base for a spatial manipulator. The results of the paper are very useful for the design and application of the new manipulator.

Pulsar Observations with Radio Telescope FAST

FAST, Five hundred meter Aperture Spherical Telescope, is the Chinese effort for the international project SKA, Square Kilometer Array. An innovative engineering concept and design pave a new road to realizing huge single dish in the most effective way. Three outstanding features of the telescope are the unique karst depressions as the sites, 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. Besides a general coverage of those critical technologies involved in FAST concept, the progresses in demonstrating model being constructed at the Miyun Radio Observatory of the NAOC is introduced. Being the most sensitive radio telescope, FAST will enable astronomers to jumpstart many of science goals, for example, the natural hydrogen line surveying in distant galaxies, looking for the first generation of shining objects, hearing the possible signal from other civilizations, etc. Among these subjects, the most striking one could be pulsar study. Large scale survey by FAST will not only improve the statistics of the pulsar population, but also may offer us a good fortune to pick up more of the most exotic, even unknown types like a sub-millisecond pulsar or a neutron star – black hole binary as the telescope is put into operation.

Preparatory Study for Constructing FAST, the World's Largest Single Dish

A 500-m aperture spherical telescope (FAST) was funded by the National Development and Reform Commission of China (NDRC) in July 2007 and will be located in the unique Karst region, a sinkhole-like landform, in Guizhou province. FAST can be seen as a modified ldquoArecibordquo type radio telescope using many innovative techniques, with as much as twice the collecting area and a wider sky coverage. FAST has, first, an active reflector, conforming to a paraboloid of revolution from a sphere in real time through actuated control, which enables the realization of wide bandwidth and full polarization capability by using standard feed design. Secondly, it has a light focus cabin suspension system, integrating optical, mechanical, and electronic technologies, reducing effectively the cost of the support structure and control system. With such a huge collecting area of more than 30 football fields, FAST will become the largest single dish ever built. Here we will summarize the FAST concept and the milestones achieved in experiments on its key technologies, i.e., site exploration, active reflector prototyping, focus cabin driving mechanism, measurement and control techniques, and the receiver layout. The Miyun FAST demonstrator also will be presented.

The Five-hundred-meter Aperture Spherical radio Telescope (FAST) project

The Five-hundred-meter Aperture Spherical radio Telescope (FAST) is a Chinese mega-science project funded by the National Development and Reform Commission (NDRC). The National Astronomical Observatories of China (NAOC) is in charge of its construction and the subsequent operation. Upon its expected completion in September of 2016, FAST will surpass the 300-meter Arecibo and the 100-meter GBT in terms of absolute sensitivity in the 70 MHz to 3 GHz bands. In this paper, we report the current status, the key science goals, and the aspiration of its early sciences. A special emphasis is paid to its innovative fatigue-resistant fibers, which are critical for the control and data acquisition under the unique FAST design.

A Study of the Fitting Accuracy of the Active Reflector for a Large Spherical Radio Telescope

We propose a spatial three-degree-of-freedom (DOF) parallel mechanism combining two degrees of rotations and one degree of translation to support the active reflector units of a large spherical radio telescope. The kinematics, workspace and accuracy of the mechanism are analyzed. One-dimensional and two-dimensional fitting errors to the working region of active reflector are investigated. Dimensional parameters of the mechanism and active reflector unit are examined with respect to the requirement of fitting accuracy. The result of accuracy analysis shows the eectiveness and feasibility of the proposed mechanism, and gives a design rule to about 200m. The feed system is movable at a height of about 100m when tracking the object to be observed. The enormous receiving area of the telescope will enable it to make many important astronomical discoveries inaccessible to lesser instruments, despite its limited sky coverage (20 zenith scan angle) due to geometrical configuration, and its narrow frequency bandwidth, originated from spherical aberration. An upgrade project has been carried out for

Simulation for the Active Reflector of FAST 30m Model

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.

Development of active reflector of the 30-meter FAST model

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.

The study on the scheme of measurement and control for FAST

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.

Workspace and rotational capability analysis of a spatial 3-DoF parallel manipulator

Abstract The analysis on the workspace and rotational capability of HANA, a spatial 3-DoF parallel manipulator, is concerned. The parallel manipulator consists of a base plate, a movable platform, and three connecting legs. The moving platform has three degrees of freedom (DoFs) which are two translations and one rotation, with respect to the base plate. The new parallel manipulator is very interesting for the reason of no singularity in the workspace, the single-DoF joint architecture and high rotational capability of the moving platform. The inverse kinematics problem is described in a closed-form, which is very useful to present the workspace geometrically. The constant-orientation and reachable workspaces for the manipulator are analyzed firstly. The index that is used to evaluate the rotational capability of the manipulator is defined and discussed in detail. Finally, the distribution of rotational capability index on the workspace is presented, which helps us know how much the index is at different ...