FAST索牵引并联机构若干关键问题的研究

The main components of cable-driven parallel robot of FAST telescope are 6 parallel steel cables and its end-effector, the feed cabin. The 6 cables, each hundreds of meters long, drive cooperatively the airborne 30-ton cabin to move within a spatial range of about 200 meters in diameter. The giant cable-driven parallel robot has great flexibility and low natural damping. This performance lets the robot exposed to disturbance-induced vibrations on large scale, which is a great challenge for reaching the final positioning precision of the feed cabin, as desired by the telescope. Therefore three key problems in plan are specially investigated to find effective solutions or improvements capable of precisely controlling both position and pose of the feed cabin..First, dynamic model of cabin-cable suspension system is formulated and analyzed. The characteristics of the system such as the natural frequency, vibration mode, input-output relationship, principally the transfer function, are specially investigated. Based on the dynamics, further attention will be paid on the control stability of the robot. Second, an artificial damping-increasing design concept is studied and developed based on certain small & light style dampers to effectively reduce cabin vibrations. Its feasibility is verified in the model test of the cabin-cable system. Finally, the work on dynamics and vibration control will help the feasibility study of motion planning of the robot under all kinds of working modes. The emphasis is put on the dynamic analysis of the system and acceleration/deceleration time-amplitude curve when the cabin is accelerated or decelerated at the beginning or end of a trajectory. Therefore smooth transition of the cabin position or cabin pose can be possible under different working modes. The study also helps to improve the control algorithm of the robot.

FAST索牵引并联机构主体由6根钢索和终端控制平台-馈源舱并联连接构成。6根钢索均长约数百米，牵引重达30吨的馈源舱在200余米空间范围运动。FAST索牵引并联机构柔性大且自身阻尼小，容易受到各种扰动影响产生大幅震荡，这对于馈源舱位姿控制是一个巨大挑战。我们从FAST索牵引并联机构的三个关键问题出发，研究实现馈源舱位姿控制较为精准的方案及改进措施。.首先，我们建立舱-索柔性悬挂系统的动力学模型，分析其固有频率、振型、输入输出频响函数等动力学特性参数，进而分析FAST索牵引并联机构控制的稳定性。其次，我们开发一种基于小型和轻型化阻尼器的人工增阻方案，可有效抑制馈源舱振荡，并通过模型试验验证该方案的可行性。最后，我们评估各种望远镜工作模式下的运动规划方案的可行性，重点分析馈源舱在启停阶段的系统动力学性能及加/减速时程曲线，以保证不同模式下馈源舱位姿的平稳过渡和舱的定位精度，进而完善控制算法。

500 米口径大型射电望远镜（FAST）是世界上最大单口径射电望远镜，在基础科学研究和国家重大需求方面均具有重要的应用价值。本项目针对FAST柔索牵引并联机器人的若干关键问题进行了研究，包括动力学建模和分析、原型控制精度分析、运动规划问题、3米缩尺模型实验和大跨度钢索的声学检测仿真分析与实验等，解决并联机器人在实际应用中所面临的工程问题。通过对原型动力学建模与仿真分析，获得了舱索柔性悬挂系统固有频率的简化计算公式，论证了系统在恶劣工况下的抗冲击性能。基于不同轨迹下的原型控制精度试验证明了系统在跟踪工况下的位姿定位精度满足望远镜性能要求。专门分析了悬索牵引并联机构的运动学逆解问题，得到了满足索张力可行的馈源舱运动工作空间和姿态角规划最优解。本项目改造完善了原来的3米缩尺实验模型，在此基础上试验了初步可行的系统增阻方案。此外，还对FAST柔索牵引并联机器人中的关键部件—大跨度钢索—的声学检测问题进行了初步探索和试验分析。这些成果将作为下一步深入研究的工作基础。本项目的研究可进一步向国际尖端的索驱动并联机构相关应用技术领域延伸，提高我国在相关重大技术领域的研究实力。