摘要
三十米望远镜(TMT)的观测设备位于望远镜两侧的奈氏平台上,使得TMT拥有独特的三镜系统。为保证成像的稳定,三镜系统应具有跟踪瞄准的功能,必须设计相应的机构使三镜系统具有二维调整的能力。三镜系统由两个轴系组成,分别为Rotator轴和Tilt轴。由于Tilt轴调整量为16°,所以,拟使用一个大型的Stewart平台来替代实际的Tilt轴系,以实现三镜在空间中的Tilt调整。以前期工作得到的Stewart结构参数为前提,采用逆运动学控制策略,在Simulink中建立了相应的数学模型。另外,在动力学仿真软件ADAMS建立了相应的Stewart平台的三维结构,并通过与Simulink的联合仿真,得到了系统在六个方向上的跟随情况,并通过引入误差的方法研究了该结构在工作空间中支腿误差到动平台位姿误差的传递情况。分析结果表明,上述结构在工作空间中支腿精度到动平台U方向的最大映射系数为1.4,需选择精度优于0.69μm的支腿才能满足TMT三镜系统跟踪要求。为现有的设计在逆运动学的控制策略下能够满足TMT三镜系统Tilt调整的需要。
The unique design that settles the instruments on both of the Nysmyth platforms makes the thirty-meter telescope （TMT） has a unique tertiary mirror system （M3S）. The M3S should handle tracking and pointing capabilities to ensure the stability of imaging, which can be achieved by two orthogonal axes rotating respectively. One is called Rotator and the other one is named as Tilt. Due to a small adjustable range of the Tilt, about 16 degrees, a Stewart platform was put forward to settle this design. In this paper, structure parameters were obtained from the pre- liminary work on the stiffness analysis. Furthermore, a mathematical model was established in simulink based on inverse kinematics control strategy, while a 3D model was established in ADAMS. The following eases were simulated using the hybrid method between simulink and ADAMS. In addition, some errors were introduced to the leg inputs in the control system to simulate the error transfer process. Then we found that the control strategies based on the inverse kinematics can be employed in controlling the platform. Besides all, the maximum mapping coefficient is up to 1.4, which leads a 0.69 μm accuracy requirement of the leg.
出处
《计算机仿真》
CSCD
北大核心
2015年第11期234-237,共4页
Computer Simulation
