基于旋转双棱镜的光束复合跟踪控制技术

Beam Compound Tracking Control Technology Based on Rotating Double Prism

提出一种基于旋转双棱镜的光束复合跟踪技术,用于取代传统伺服转台实现精密的光学跟踪。首先,建立双棱镜的光束偏转模型,详细推导光束偏转矢量与双棱镜转角间的转换关系,并对跟踪过程中的棱镜旋转非线性问题进行了分析。提出基于快速反射镜进行光轴修正的双棱镜光束复合跟踪方法,通过建立偏转光轴与光学基台间的扰动耦合关系,实现了对双棱镜转速的实时补偿,并改进棱镜控制器以提高光束控制性能。搭建实验系统,对旋转双棱镜复合跟踪技术进行验证。在动态跟踪实验中,采用改进控制器的双棱镜的控制精度明显提高,相较于比例-积分-微分控制器和线性自抗扰控制器,所提出的改进控制器使棱镜的控制精度分别提高58.33%和32.81%,并使跟踪误差由改进前的49.03μrad和38.88μrad降低为31.15μrad。开启视轴补偿后跟踪性能进一步提高,总跟踪误差降至7.49μrad,跟踪精度提高4.16倍。实验结果表明,光束复合控制能有效提高双棱镜的跟踪精度,验证了所提方法的有效性。

In recent years,photoelectric tracking technology has developed rapidly and has been widely used in space laser communication,laser weapons and other fields.Traditional optoelectronic tracking systems mostly use servo turntables or optical mirrors to achieve beam adjustment to ensure accurate tracking of the target.However,they usually have a large size and weight,and excessive sensitivity to vibration also affects their dynamic tracking performance.A typical representative of a small-inertia beam servo system is the rotating double prism,which consists of a pair of circular optical prisms with specific wedge angles.Both prisms rotate with the same central axis to achieve fast beam deflection,which has the advantages of high accuracy,low rotational inertia,fast beam pointing,and low vibration sensitivity,which makes the double prism system of important practical value in laser communication,interferometry,photoelectric detection,and other fields.The key to achieving target tracking using double prisms is to reveal the nonlinear variation mechanism of beam delivery and to develop an effective prism control strategy.In this paper,a beam compound tracking technology based on a rotating double prism is proposed to replace the traditional servo turntable to achieve precise optical tracking.Firstly,the beam deflection model of the double prism is established,the relationship between the beam deflection vector and the prism angle is deduced in detail,and the nonlinear problem of the prism rotation in the tracking process is analyzed.A double-prism composite tracking system is designed to change the direction of the beam by using two independently rotating prisms,each of which is rotated under the drive of a motor.In the doubleprism tracking system,an improved controller is designed to improve the tracking performance,and an FSM is added behind the double prisms,and the beam passing through the prisms will be deflected by the FSM for the final error complement.Among them,the rotating double prism is responsible for a wide range of beam adjustment,and a large field-of-view target viewing camera is added to the system for searching the target position and initial alignment of the optical axis.The FSM is used to compensate for the beam control error of the double prism,and the tracking camera is used as the target detection element in the system to obtain the aiming error of the optical axis in real time.The inertial measurement unit is mounted on an optical abutment.Unlike traditional two-dimensional servo turntable,the rotating dual prism system has a special structure and beam deflection mechanism,which cannot achieve optical axis stabilization through on-axis gyroscopic feedback as in traditional two-dimensional servo turntable,so the dynamic compensation of the optical axis is achieved through attitude decoupling.An experimental system is built to verify the compound tracking technology of the rotating double prism.A collimator is used in the direction along the center axis of the rotating double prism to generate near-parallel light to simulate a long-range target,and the rotating double prism system is fixed to a six-degree-of-freedom swing table for simulating attitude perturbations of a moving pedestal platform.In the dynamic tracking experiment,the control accuracy of the biprism using the improved controller is obviously improved.Compared with the PID controller and the linear active disturbance rejection controller,the control accuracy of the prism is increased by 58.33%and 32.81%respectively,and the corresponding tracking errors are reduced from 49.03μrad and 38.88μrad to 31.15μrad.After turning on boresight compensation,the tracking performance is further improved,with the total tracking error reduced to 7.49μrad and the tracking accuracy increased by 4.16 times.The experimental results show that the beam compound control can effectively improve the tracking accuracy of the rotating double prism,which verifies the effectiveness of the proposed method.