Fast Steering Mirror Research Articles

Modelling of fast steering mirror assembly: A review of the various methodologies

The interest towards using Fast Steering Mirror (FSM) assembly in optical communication is mainly fueled by the fact that this device has the capability of precise pointing and stabilization of the beam in optical systems. Scientists across the world are working on modelling and control of FSM that will not only perform efficiently but also guarantee stability. Computationally efficient model of the FSM is one basic demand from scientists, for developing a control strategy of the FSM. Attention is focused on works which involves building a feedback control design to model a FSM. The survey results are not only used to identify the differences and similarities of the approaches, but also used to identify the modelling methodology suitable for a specific application.

Effect of reciprocity-breaking on fine-track tip/tilt systems.

We analyze here a candidate system for correcting the wander of a self-channeled laser pulse using a fast-steering mirror along with a cooperative beacon imaged with a telescope. For our model system, the imaging telescope is coaxial with the propagation of the outgoing pulse. In the ideal case, any incoming light gathered from the beacon would be collimated, such that taking a centroid beacon image would yield the precise tip and tilt required for the self-channeled pulse to propagate back to the beacon on the reciprocal path. The degree to which reality differs from this ideal case determines the effectiveness of the wander correction. We simulate our system for a range of propagation and imaging conditions. We also show that in the absence of image noise (i.e., when the beacon power is arbitrarily high, and the signal-to-noise ratio is not an important consideration), the system exhibits its best performance when the receiving aperture diameter of the imaging system is close to the transverse size of the outgoing pulse, maximizing reciprocity. When realistic noise and finite beacon power are included in the simulation, however, we find that this reciprocity advantage may not be sufficient to compensate for the reduced photon count and resolving power of a small receiving aperture. In this case, the optimal aperture diameter will be the smallest possible, which allows for an acceptable signal-to-noise ratio.

Model-Rebuilt Disturbance Observer of a Tracking System Based on Acceleration Fusion for Laser Power Transmission

When using laser energy to power long-distance and fast-moving targets, it requires a fast-response and high-precision acquisition, pointing and tracking (APT) system. A fast-steering mirror (FSM) system was used in this paper to track the solar cell array as laser power receiver. The disturbance suppression performance is a key indicator for the FSM stabilization. Generally, a fiber-optic gyroscope (FOG) is employed in the high-sampling-rate velocity loop to enhance the anti-interference ability. However, with the expansion of miniaturized applications, a relatively large, heavy, and high-power FOG is hard to be installed on the small mirror. With this case, this paper used a small-size and high-bandwidth MEMS linear accelerometer in the acceleration loop, substituting the gyroscope. However, the drift and high-frequency noise of the MEMS accelerometer in low frequency will cause APT disturbance. Therefore, an acceleration fusion method with a modified complementary filter was proposed to blend signals of the charge-coupled device and the accelerometers. The fused virtual acceleration can eliminate drift and reduce noise in low frequency and was eventually used in the model-rebuilt disturbance observer loop. At last, the measured results show that the disturbance suppression performance is improved using the presented method, and low-price and small-size MEMS accelerometer can be applied in the APT system.

Laser Beam Jitter Control Based on a LabVIEW FPGA Control System

The thermal blooming effect, platform jitter, and other effects of laser beam propagation cause serious deviation, which will have a negative impact on laser tracking systems. It is important to ensure that the laser beam does not deviate. Based on a fast steering mirror, a CMOS camera, and a Flex RIO system, a laser beam jitter control system is designed and implemented. The error is detected by camera and compensated for by the fast steering mirror (FSM), which is controlled by the Flex RIO device. By using LabVIEW and MATLAB, a closed loop model is realized. The results show that the system response is highly stabilized and has a short rise time, providing a reference for engineering applications.

Probabilistic model to spatially acquire optical links in space under the influence of band-limited beam jitter.

An analytical model is derived for the probability of failure (P-fail) to spatially acquire an optical link with a jittering search beam. The analytical model accounts for an arbitrary jitter spectrum and considers the associated correlations between jitter excursions on adjacent tracks of the search spiral. An expression of P-fail in terms of basic transcendental functions is found by linearizing the exact analytical model with respect to the correlation strength. Predictions from the models indicate a strong decrease of P-fail with increasing correlation strength, which is found to be in excellent agreement with results from Monte Carlo simulations. The dependency of P-fail on the track width and scan speed is investigated, confirming previous assumptions about the impact of correlations. Expressions and applicable constraints are derived for the limits of full and no correlations, and the optimal track width to minimize the acquisition time is computed for a range of scan speeds. The model is applicable to optical terminals equipped with a fast beam steering mirror, as often found for optical communications missions in space.

High-precision dynamic pointing method for improving the acquisition performance of laser communication between high-altitude platform stations

Fast and stable acquisition is the prerequisite for establishing a space laser communication links. In this paper, the acquisition technology of establishing a space laser communication link between high-altitude platform stations (HAPS) is studied, a dynamic pointing and scanning model is established, and the acquisition performance of the laser communication system under line of sight (LOS) disturbance is analyzed based on this model. To improve the acquisition performance, we propose a high-precision composite pointing method to reduce the pointing error of the line of sight. A composite pointing controller with a fast steering mirror (FSM) is designed to reduce pointing errors, and the aiming accuracy of line of sight is improved by predicting the target with improved unscented Kalman filter (IUKF). A dynamic laser communication experiment based on HAPS is built to verify the method. The results show that the proposed method reduces the initial pointing error by 45%, and the stability of the line of sight is increased by a factor of 5. By conducting several acquisition tests, the average acquisition time is 1.57 s with 100% acquisition probability. The acquisition performance is significantly improved compared with that before the improvement, in which the acquisition probability is increased by 8% and the acquisition time is reduced by 44.3%, which verifies the effectiveness of the proposed method and lays the foundation for the establishment of a fast communication link for laser communication between HAPS.

Prototype development of multi-target tracking system for space multi-node laser communication network

Laser communication network is the future trend, but the disadvantage of a traditional laser communication system is that it can only transmit with a single node. To solve this problem, we propose a multi-target tracking technology to simultaneously establish multiple laser communication links. This study also develops a multi-target detection method based on beacon modulation and code division multiple access, proposes an optical antenna central stabilization method, and enhances the controller of the fast steering mirror (FSM) to improve the tracking performance. To verify the feasibility of our proposed method, we build a prototype system for multi-target laser communication and conduct the corresponding experiment. The experiment simulates the multi-target tracking situation by three beam emitting subsystems, and the dynamic tracking performance of the prototype system is verified by applying perturbations through a shaking table. Results show that the proposed method can effectively extract the position of the target in the mixed beam, with an average detection deviation of 2.95 μrad compared with when only a single beam is incident. The introduction of central stabilization enhances the dynamic tracking performance of the optical antenna. Tracking accuracy of the optical antenna is 24.63 μrad when attitude disturbance is applied. The improved controller enhances the performance of FSM, composite tracking accuracy is 5.69 μrad, and tracking error is reduced by 22.16% compared with the traditional PI controller. Performance also improved by 45.42% compared with when there was no improvement. Experimental results verify the effectiveness of the multi-target tracking system. On the basis of the proposed method, we achieve simultaneous tracking of multiple targets in different directions and significantly improve the dynamic tracking performance.

Motion profile and control design of fast steering mirror for backscanning step and stare imaging.

Fast steering mirrors (FSMs) have been used for decades to improve the performance of electro-optical imaging systems, such as airborne imaging systems and space-based optical surveillance systems. With the advantage of increasing the accuracy of image motion compensation and the efficiency of scanning imaging, backscanning step-and-stare imaging has become the main approach to realizing wide-area surveillance for airborne imaging systems. According to the operating mode and motion profile of the FSM in the imaging system, a combined optimized profile (COP) is designed to avoid abrupt changes in the velocity and acceleration of the FSM. The angular position sensor based on a four-quadrant detector is used in FSMs to expand the measuring range and cut the cost at the expense of larger measurement noise. Combining a Kalman filter with a disturbance observer and zero-phase error tracking control, a control method is proposed to improve the control precision and bandwidth while suppressing measurement noise. Simulation and experimental results show that the profile designed by COP is smooth enough to meet the special requirements of FSM's backscanning image motion compensation and that the Kalman filter-based FSM control method can significantly improve the control accuracy.

Modeling-free Learning Control of Cross-coupled Fast Steering Mirror for 2-D Trajectory

This paper proposes modeling-free inversion-based iterative control (MF-IIC) for a fast steering mirror, which is a dual-input dual-output system to generate 2-D optical scanning trajectories. To explicitly compensate for the cross-coupling motions, the MF-IIC iteratively updates the control inputs by learning from the previous trials based on a 2 × 2 Jacobian matrix. To operate the MF-IIC without system identification in advance, it estimates the Jacobian matrix including the non-diagonal elements for the cross-coupling dynamics simultaneously during learning. For experiments, 19 Hz and 20 Hz sine waves with an amplitude of 0.65° are used for a Lissajous pattern as a reference trajectory. Experimental results show that a tracking error of 320 × 10−3 degrees when feedback control is used for stability. By additionally combing the proposed MF-IIC, the error is decreased by a factor of 68 to 4.64 × 10−3 degrees. It is smaller than MF-IIC without considering the cross coupling explicitly, which achieves a tracking error of 12.1 × 10-3 deg. These two MF-IIC algorithms are also compared by the resulting sampled trajectories in the spatial domain. For that purpose, maximum dead zone diameter is defined as a diameter of the largest circle without sampled points in a scanning area in this paper. While the MF-IIC without considering the cross coupling explicitly for comparison creates a Lissajous pattern with a maximum dead zone diameter of 74.8 × 10−3 degrees, the proposed MF-IIC achieves a Lissajous pattern with a smaller maximum dead zone diameter of 72.9 × 10−3 degrees, demonstrating its effectiveness for high-quality scanning trajectories.

Control of a MEMS Fast Steering Mirror With Improved Quasi-Static Performance

Control of a MEMS Fast Steering Mirror With Improved Quasi-Static Performance

Theoretical modeling and simulation analysis for fast steering mirror

为有效指导快速反射镜设计，开展了快速反射镜理论建模与仿真分析研究。相比以往单自由度运动模型，该文基于动力学分析，建立了两轴快速反射镜的多自由度运动微分方程，推导出被控对象传递函数和对基座扰动的隔离传递函数；仿真分析了结构谐振频率对被控对象特性的影响，指出转动固有频率较大时，被控对象为欠阻尼系统，传递函数曲线存在谐振峰；建立了包含结构特性的快速反射镜控制系统仿真模型，分析了负载质心偏离柔性铰链支承中心、结构谐振频率等对其扰动隔离性能的影响，指出非工作轴固有频率越大，对扰动隔离性能越好，一般选择在伺服系统增益交界频率2倍以上，工作轴固有频率需权衡扰动隔离性能和电机力矩约束等进行选择。最后结合实物振动试验，验证了仿真模型的正确性。

Application of Nonlinear PID Active Disturbance Rejection Control in the Temperature Control System of Fast Steering Mirror

Application of Nonlinear PID Active Disturbance Rejection Control in the Temperature Control System of Fast Steering Mirror

Research progress of reliability of MEMS fast steering mirror for satellite laser communication

Research progress of reliability of MEMS fast steering mirror for satellite laser communication

Improved Active Disturbance Rejection Control Algorithm Based on Fast Steering Mirror for Optical Communication

Improved Active Disturbance Rejection Control Algorithm Based on Fast Steering Mirror for Optical Communication

System modeling and sliding mode control of dual-axis voice coil actuator fast steering mirror

System modeling and sliding mode control of dual-axis voice coil actuator fast steering mirror

Improving laser cutting quality of carbon fiber-reinforced plastics by improving laser beam pointing stability

A heat-affected zone significantly reduces the mechanical properties of carbon fiber-reinforced plastics (CFRP). However, the beam quality, especially the stability of the beam pointing, limits the heat-affected zone (HAZ) minimization studies. In this study, the HAZ is reduced by improving the pointing stability of the laser beam. A beam pointing stabilization system (BPSS) based on position-sensitive devices and fast steering mirrors (FSMs) was developed. The research focuses on building a control model from the position-sensitive devices’ position deviation signals to the FSMs’ corrected control angles. The control model can detect and predict the beam pointing deviations and correct the attitudes of the FSMs to correct the beam pointing deviations, improving the beam pointing stability. The performance of the proposed BPSS and the corresponding control model were experimentally verified. The results indicate that the pointing deviations of the corrected beam in the X and Y directions are reduced by 78.08% and 70.28%, respectively. Additionally, the HAZ of CFRP processed with the corrected laser is reduced by 30.8%. The quality of the laser cutting of CFRP is significantly improved.

압전효과를 고려한 고속조종거울의 유한요소 해석 모델 구축

A laser weapon is a directed-energy weapon system that uses a high-energy laser to target and destroy the enemy. To precisely control laser to the target, the FSM (fast steering mirror) is an essential component in the precise control strategy. FSMs are optical devices that accurately aim a laser beam using the mirror

Modeling and analysis of fast steering mirror disturbance effects on the line of sight jitter for precision pointing and tracking system

Fast steering mirrors (FSMs) are typically applied for beam stabilization for precision pointing and tracking systems (PPTSs) owing to their high-bandwidth, high-resolution, and high accuracy. In addition to the advantages, the presence of the residual momentum which caused by FSMs’ operation usually has noticeable effects on the stabilization of the line of sight (LOS) for PPTSs. Hence, it is necessary and momentous to estimate the effects of these disturbances to give insight into the FSM specification and the PPTS structural performance. However, the characteristic of multidisciplinary coupling makes it a challenge to measure the LOS jitter caused by FSMs. We approach this problem by establishing an integrated model for estimating the LOS jitter. A dynamic model of an FSM is firstly built to value the unbalanced momentum generated from its motion. Then a finite element model for the structure of the tracking system is established to predict the dynamic response excited by the disturbances from the FSM. In addition, with a linear optical model, the system optical performance under the FSM’s disturbances is determined. Finally, a test is conducted to verify the validity of the model and the analysis. This paper focuses on estimating the disturbances effects of the FSM on the LOS jitter for a PPTS, and providing potential approaches for reducing these effects.

Development of piezoelectric fast steering mirror with tilt error compensation for portable spectroscopic sensor

Fast steering mirror, a key component that can compensate for the distortion of the optical axis, plays an essential role in portable spectroscopic sensors. Because the performance of the fast steering mirror has a great influence on the accuracy of the interferometer in the spectroscopic sensor, it is important to verify whether it can satisfy the design requirements by evaluating the performance. In this study, a piezoelectric fast steering mirror with high-resolution and high-speed tilting capability for a portable spectroscopic sensor was fabricated and tested. Design requirements such as steering angle, resolution, and frequency range were set for portable spectroscopic sensors and elastic guide structures actuated by piezoelectric actuators were proposed. Before fabrication, the performances of the proposed fast steering mirror were examined by the finite element method. To verify the proposed fast steering mirror, a prototype was manufactured with a size of 24.5 mm × 24.5 mm × 37.4, including a mirror with a diameter of 20 mm and thickness of 3 mm. This prototype can provide the sufficient convenience for mounting on a spectroscopic sensor for gas monitoring at a distance. Its performance was tested, confirming a steering range of 0.56°, resolution of 1.27 µrad seconds and natural frequency of 282 Hz. In addition, through a performance evaluation test using a visible light laser on an optical test bed, the ability to compensate the tilt error within a few seconds was confirmed for its applicability to actual spectroscopic interferometer products in the future.

Robust finite-time adaptive control for high performance voice coil motor-actuated fast steering mirror.

Fast steering mirror (FSM) is an efficient and reliable mechanical device in aerial optical image systems for controlling the beam direction with high precision. With the advantages of compact size, high speed, simple structure, and long linear stroke, voice coil motors are ideal actuators for FSM systems. However, model uncertainty can lead to poor performance or even system divergence, especially in environments with temperature variations, electromagnetic environment changes, etc. This paper proposes a novel finite-time adaptive control (FAC) algorithm for an FSM system to obtain high performance, i.e., positioning accuracy, dynamic performance, and robustness. In addition, the finite-time convergence of the controller is analyzed. In the experiments, the controller is implemented in a DSP-based microprocessor. The step response results show that the proposed algorithm has a shorter setting time, smaller overshoot, and smaller steady-state error compared to classical sliding mode control (SMC). The sinusoidal signal tracking accuracy of FAC + SMC has been improved by 19.8%. In addition, as the model uncertainty increases 10%, the root mean square errors (RMSEs) are 1.73″ and 1.18″ for SMC and FAC + SMC, respectively. With 20% model uncertainty, the RMSEs increase to 2.56″ and 1.85″, respectively. Extensive experiments demonstrate the general effectiveness of the proposed algorithm.