Research on the cable-driven mechanism has greatly developed with the booming of the robots in the past 30 years, and a range of corresponding theoretical studies have been published on them. The large-scale robot or manipulator with the complex cable-driven mechanism can be reconfigured. However, more theoretical studies are required on their topological architecture design and optimization to achieve this. Therefore, the applied cable-driven architectures and the corresponding theoretical studies are reviewed and summarized here. The parallel, serial, and differential architecture are illustrated, as well as their theories and methods, such as the workspace analysis based on the Jacobian matrix, particle swarm optimization and genetic algorithm, and kinematic design based on the graph theory are described. The features of the architecture and the theory studies are concluded. It is hoped that this study will help with design of future studies.

https://journals.sagepub.com/doi/pdf/10.1177/1687814018774186

A review on topological architecture and design methods of cable-driven mechanism:

The Five-hundred-meter Aperture Spherical radio Telescope (FAST) was completed with its main structure installed on September 25, 2016, after which it entered the commissioning phase. This paper aims to introduce the commissioning progress of the FAST over the past two years. To improve its operational reliability and ensure effective observation time, FAST has been equipped with a real-time information system for the active reflector system and hierarchical commissioning scheme for the feed support system, which ultimately achieves safe operation of the two systems. For meeting the high-performance indices, a high-precision measurement system was set up based on the effective control methods that were implemented for the active reflector system and feed support system. Since the commissioning of the FAST, a low-frequency ultra-wideband receiver and 19-beam 1.05-1.45 GHz receiver have been mainly used. Telescope efficiency, pointing accuracy, and system noise temperature were completely tested and ultimately achieved the acceptance indices of the telescope. The FAST has been in the process of national acceptance preparations and has begun to search for pulsars. In the future, it will still strive to improve its capabilities and expand its application prospects.

Commissioning progress of the FAST

Theory of pulsars: Polar gaps, sparks, and coherent microwave radiation

Neutral atomic hydrogen (HI) and molecular hydrogen (H2) play a primordial role in the cosmic evolution of galaxies. However, little is known about the co-evolution of these two gas phases. This discrepancy and the design of future telescopes like the SKA and ALMA require theoretical models of the joint evolution of HI and H2 in galaxies. This thesis starts with a phenomenological analysis of the H2/HI-ratios in a sample of 245 local galaxies. This analysis reveals a number of correlations between H2/HI-ratios and other galaxy properties, and we demonstrate that these correlations can be understood in terms of the microscopic relation between the H2/HI-ratio and the external gas pressure. We subsequently use this relation to derive an analytic model for the column densities of HI and H2 in arbitrary regular galaxies. As a second step, we apply the model for the column densities of HI and H2 to post-process approximately 3*10^7 virtual galaxies, whose cosmic evolution was simulated on the evolving dark matter skeleton output by the Millennium Simulation. The post-processing of these galaxies allows us to (i) split their total cold gas masses between HI, H2, and Helium, (ii) to assign realistic sizes to both the HI and H2-disks, and (iii) to evaluate the velocity profiles of HI and H2. The resulting hydrogen simulation successfully reproduces many local observations of HI and H2, such as mass functions (MFs), mass-diameter relations, and mass-velocity relations. A key prediction of this simulation is that the H2/HI-ratio of regular galaxies increases dramatically with redshift z, leading to a scaling of (1+z)^1.6 for the ratio between the cosmic space densities of H2 and HI. This prediction offers a unified explanation for (i) the weak evolution of the cosmic HI-density inferred from Lyman-alpha absorption against quasars, (ii) the large molecular masses detected in regular galaxies at z=1.5, and (iii) the recent cosmic decline in the density of star formation. As a third step, we introduce a heuristic model for the conversion of H2-masses into observable CO-line luminosities for galaxies at all redshifts. We apply this model to our hydrogen simulation in order to predict the luminosity functions of the first 10 rotational transitions of CO in galaxies at redshift z=0 to z=10. As a final step, we transform the simulated catalog of 3*10^7 evolving galaxies into a virtual observing cone, i.e. a catalog that lists the apparent HI and CO-line fluxes and corresponding line widths of millions of galaxies in a sky field with a comoving diameter of 500 Mpc/h. This catalog represents a tangible contribution towards the design and operation of future telescopes, such as the SKA and ALMA.

The Cosmic Evolution of Atomic and Molecular Hydrogen in Galaxies

This paper presents a review of the state of the art in the area of cable-driven parallel mechanisms. The basic kinematic architecture of cable-driven parallel mechanisms is first recalled and the associated kinematic and static model is briefly exposed. Fundamental problems are formulated, including the definition of the wrench matrix, the wrench-closure workspace and the wrench-feasible workspace. Advances that have been made in the determination of such workspaces are reported. The dynamics and control of cable-driven parallel mechanisms are then considered, first for fully constrained cable-driven parallel mechanisms and secondly for cable-suspended parallel mechanisms. Calibration and identification issues are also addressed and various alternative architectures of cable-driven parallel mechanisms are reported. Finally, applications are considered and open issues are mentioned.

/pdf/cable-driven-parallel-mechanisms-state-of-the-art-and-4342afa6ap.pdf

Cable-driven parallel mechanisms: state of the art and perspectives

The Five-hundred-meter Aperture Spherical radio Telescope (FAST) passed national acceptance and is taking pilot cycle of 'Shared-Risk' observations. The 19-beam receiver covering 1.05-1.45 GHz was used for most of these observations. The electronics gain fluctuation of the system is better than 1\% over 3.5 hours, enabling enough stability for observations. Pointing accuracy, aperture efficiency and system temperature are three key parameters of FAST. The measured standard deviation of pointing accuracy is 7.9$''$, which satisfies the initial design of FAST. When zenith angle is less than 26.4$^\circ$, the aperture efficiency and system temperature around 1.4 GHz are $\sim$ 0.63 and less than 24 K for central beam, respectively. The measured value of these two parameters are better than designed value of 0.6 and 25 K, respectively. The sensitivity and stability of the 19-beam backend are confirmed to satisfy expectation by spectral HI observations toward N672 and polarization observations toward 3C286. The performance allows FAST to take sensitive observations in various scientific goals, from studies of pulsar to galaxy evolution.

The fundamental performance of FAST with 19-beam receiver at L band

The Fundamental Performance of FAST with 19-beam Receiver at L Band

This paper addressed the determination of the tension distribution in the slack steel wires of the incompletely constrained cable-driven parallel mechanism of FAST telescope. Slack rope hung with piecewise uniform mass is specially investigated. First, the general formulation based on the wrench matrix was derived. Then the analytical model of slack rope was built to give the quantized relation between direction and amplitude of tension vector. The wrench matrix is not only platform pose dependent but influenced by rope geometry. Finally, a performance index based on minimal tension variance is selected to optimize the tension distribution among steel wires. Levenberg-Marquardt method is applied to solve the quadratic program and a discrete-mesh plan is proposed for the whole focal surface. An example of computation is given to verify the effect of the resolution.

Optimal Force Distribution Based on Slack Rope Model in the Incompletely Constrained Cable-Driven Parallel Mechanism of FAST Telescope

The Five-hundred-meter Aperture Spherical radio Telescope (FAST) was completed with its main structure installed on September 25, 2016, after which it entered the commissioning phase. This paper aims to introduce the commissioning progress of the FAST over the past two years. To improve its operational reliability and ensure effective observation time, FAST has been equipped with a real-time information system for the active reflector system and hierarchical commissioning scheme for the feed support system, which ultimately achieves safe operation of the two systems. For meeting the high-performance indices, a high-precision measurement system was set up based on the effective control methods that were implemented for the active reflector system and feed support system. Since the commissioning of the FAST, a low-frequency ultra-wideband receiver and 19-beam 1.05-1.45 GHz receiver have been mainly used. Telescope efficiency, pointing accuracy, and system noise temperature were completely tested and ultimately achieved the acceptance indices of the telescope. The FAST has been in the process of national acceptance preparations and has begun to search for pulsars. In the future, it will still strive to improve its capabilities and expand its application prospects.

Gaofeng Pan

Papers

Commissioning progress of the FAST

The fundamental performance of FAST with 19-beam receiver at L band

The Fundamental Performance of FAST with 19-beam Receiver at L Band

Optimal Force Distribution Based on Slack Rope Model in the Incompletely Constrained Cable-Driven Parallel Mechanism of FAST Telescope

Commissioning Progress of the FAST