空间相机直线调焦机构的设计

Design of straight-line focusing mechanism for space camera

针对空间相机在使用时受空间环境中重力、温度及压力等因素的影响,引起各光学镜面位置相对变化,从而导致像平面与焦平面不重合的问题,在分析空间相机的3种调焦方式及调焦机构设计基本原则的基础上,针对某空间相机的要求设计了一种直线调焦机构。利用滚珠丝杠将旋转运动转化为直线运动,并结合直线导轨约束运动形式,采用绝对式编码器检测位移。该机构具有低摩擦、传动简单等优点,可有效地减少过多的传动环节所带来的传动误差。采取开环控制和闭环控制两种方式检验了该机构的精度,并讨论了误差产生的原因。实验数据的统计分析及残差分析表明,直线调焦机构的开环调焦精度为0.0025mm,闭环调焦的精度可达到0.0015mm,满足0.01mm使用要求。

When a space camera is effected by the changes of gravity, temperature, pressure in space en vironment,the image detector can not be matched with the focal plane for roirror position change. In order to improve the imaging quality,a straight-line focusing machanism driven by step motor and glided on liner guide is designed based on analysis of several kind of focusing methods and discussion on focusing mechanism. This mechanism uses ball screws to translate the rotation to the line movement, and select an absolute encoder to detect the displacement. It has the advantages of light friction and simple transmission chain and can reduce the transmission error effectively. The precision of this mechanism is checked by open-loop control and closed-loop control. Moreover, the mean value and standard deviation are calculated by statistics analysis, and the residual error curve is plotted based on the test data. The measuring results show that the focusing machanism has a high precision, the error of closed-loop control is 0. 002 5 mm, and the error of open-loop control is 0. 001 5 mm, which are less than the precision of permission.