Research on six degrees of freedom compound control technology for improving photoelectric pod pointing accuracy

High line-of-sight (LOS) pointing precision is a prerequisite for improving the laser confrontation capability of a photoelectric interference pod. In a traditional photoelectric pod, the time delay in TV tracking reduces the system phase margin, system stability and LOS pointing precision. In view of this deficiency, a normalized LMS algorithm is introduced to compensate for the TV camera delay in the inner gimbal position loop of a two-axis and four-gimbal structure, which can allow a pod to avoid system phase margin reduction. Meanwhile, a fast steering mirror (FSM) system is used to improve the LOS pointing precision. First, this paper proposes a normalized LMS algorithm. Second, a compound control structure, with an outer gimbal analog controller and an inner gimbal lag–lead controller, is designed. Finally, the FSM beam control precision is analyzed. The experimental results show that the normalized LMS algorithm yields almost no delay; moreover, the azimuth and pitch beam control accuracies are greater by a factor of 15 and 3, respectively, compared with those of a conventional photoelectric pod.