利用脉冲比对方法实现LAMOST光纤定位单元碰撞检测

Collision avoidance device on fiber positioning units in LAMOST based on pulse comparison

针对大天区多目标光纤光谱天文望远镜LAMOST光纤定位系统的定位单元在定位过程中可能发生碰撞的问题,构造了一套基于AT89S51单片机的防碰撞系统。利用单片机的定时器中断给其两个I/O口产生同频率同相位的脉冲,一个I/O端口与偏心零位相连,另一端口的脉冲信号作为比对脉冲,若两个相邻近的光纤定位单元发生碰撞,则与偏心零位相连的I/O端口的脉冲信号的脉宽会变窄,不再与比对脉冲相同。因而可以通过实时监控偏心零位电平的状态与比对脉冲是否一致,来准确判断光纤定位单元在寻星定位过程中的运行状态,并根据监控状态给步进电机相应的指令,能有效防止发生碰撞后电机继续运动损坏定位光纤头。这为LAMOST光纤定位单元稳定可靠运行提供了保障,也提高了定位系统的维护效率。

Aiming at the collision problem of fiber positioning units in LAMOST （large sky area multi-object fiber spectroscopy telescope） fiber positioning system, a collision avoidance device based on AT89S51 single-chip MCU was built. Making use of the timer interrupt in the SCMCU, we can generate pulses with same frequency and phase for two I/O ports. One is connected with the eccentricity zero, the other is used as comparison pulse. When collision happens between two adjacent units, the pulse width for eccentricity zero will become narrow and is no longer identical with the comparison pulse. The SCMCU can accurately verdict the operation state of the fiber units in seeking for stars by monitoring whether the states of the two I/O ports are consistent, and then make corresponding decision to the step motor, which can prevent the motor from damaging fiber positioning units after collision. The collision avoidance device ensures the stability and reliability of LAMOST optical positioning system, and also improves the maintenance efficiency of the fiber positioning system.