Two-axis Fast Steering Mirror Research Articles

Decoupling modeling design and high-precision position control of fast steering mirror

For a two-axis fast steering mirror (FSM) based on the flexible chain structure support and voice coil motor drive, the two axes are strongly coupled. This strong coupling may decrease the system positioning accuracy. In this study, the electric kinematics model associated with the voice coil motor and the motion and frequency equations associated with the flexible chain structure were analysed. A comprehensive system model was established considering shaft coupling, a digital controller with compensation coupling was designed, and the method of active compensation was used for decoupling. The experimental results showed that compared with the traditional non-decoupling control algorithm, the decoupling control method decreased the coupling degree from 7% to 0.8% and reduced the positioning accuracy error from 1.5% to 0.3%.

178-W picosecond green laser with active beam-pointing stabilization

Picosecond lasers with high average power and high beam quality have been widely used for precision processing and space exploration. In this study, we report a high-power picosecond green laser using a multistage Yb-doped rod-shaped photonic crystal fiber as an amplifier combined with a beam combination. The single amplification module achieves a 1,030 nm laser output of 146.8 W, and the maximum second harmonic generation (SHG) power is 92 W with a frequency conversion efficiency of 63.5%. The combined beam of the two SHGs resulted in a final output of 178 W with a repetition frequency of 24.07 MHz, pulse width of 50.1 ps, and beam quality factor of M2 = 1.16. Furthermore, an adaptive filter control method of a two-axis fast-steering mirror was applied to suppress the beam jitter to up to 45 Hz.

Structure design of two-axis fast steering mirror for aviation optoelectronic platform

Structure design of two-axis fast steering mirror for aviation optoelectronic platform

Conceptual Design and Image Motion Compensation Rate Analysis of Two-Axis Fast Steering Mirror for Dynamic Scan and Stare Imaging System.

In order to enable the aerial photoelectric equipment to realize wide-area reconnaissance and target surveillance at the same time, a dual-band dynamic scan and stare imaging system is proposed in this paper. The imaging system performs scanning and pointing through a two-axis gimbal, compensating the image motion caused by the aircraft and gimbal angular velocity and the aircraft liner velocity using two two-axis fast steering mirrors (FSMs). The composition and working principle of the dynamic scan and stare imaging system, the detailed scheme of the two-axis FSM and the image motion compensation (IMC) algorithm are introduced. Both the structure and the mirror of the FSM adopt aluminum alloys, and the flexible support structure is designed based on four cross-axis flexural hinges. The Root-Mean-Square (RMS) error of the mirror reaches 15.8 nm and the total weight of the FSM assembly is 510 g. The IMC rate equations of the two-axis FSM are established based on the coordinate transformation method. The effectiveness of the FSM and IMC algorithm is verified by the dynamic imaging test in the laboratory and flight test.

Characterization of laser thermal loading on microelectromechanical systems-based fast steering mirror in vacuum

Microelectromechanical systems (MEMS) have produced high-quality, high-bandwidth, small form factor, and inexpensive fast steering mirror (FSM) devices potentially suitable for a large variety of applications, such as image stabilization and beam pointing in satellite-based and ground-based, free-space optical communication systems. However, one outstanding question for this application is power handling. The absorption of the mirror substrate is low, but non-negligible, so the question remains of whether thermal loading from laser radiation on a MEMS mirror will deform its surface and, if so, to what extent. We show experimental results of optical performance changes due to thermal loading for MEMS two-axis FSM devices from Mirrorcle Technologies, Inc. Results and reproducible behavior are reported and compared in ambient versus vacuum conditions, where the benefits of convective cooling are absent. Finite element analyses corroborate the experimental results and show that the mirror substrate can deform due to thermal expansion imbalances. The deformation changes the focusing characteristics of the mirror, with a peak to valley defocus (second-order Zernike mode) of up to 50 nm when the mirrors are tested in ambient and up to approximately 450 nm when under vacuum. Such defocusing negatively impacts the link budget for laser-based satellite communications.

Multivariable Dynamic Input Shaping for Two-Axis Fast Steering Mirror

A two-axis Fast Steering Mirror (FSM) is a commonly used mechanical component used in optical imaging and laser beam steering. This paper shows how inverse kinematic analysis and dynamic input shaping can be used to compute the two-axis input signals for the actuation of a FSM to be able to track a desired output trajectory. The approach is based on quasi-static kinematic analysis and dynamic modeling of a two-axis FSM multivariable motion from experimental step response data. It is shown how open-loop tracking can be improved by properly designed dynamic input shaping signals that take into account the inverse kinematics and dynamic response of the FSM.

两轴柔性支承快速反射镜结构控制一体化设计

两轴柔性支承快速反射镜结构控制一体化设计

两轴柔性支承快速反射镜结构控制一体化设计

两轴柔性支承快速反射镜结构控制一体化设计

Line-of-sight kinematics modeling and correction for precision pointing systems based on a two-axis fast steering mirror

To improve the control accuracy of optoelectronic imaging equipment, the factors that affect the accuracy of the optoelectronic axis pointing are analyzed. Following Snell’s law, the kinematic coupling equation of the line-of-sight (LOS) angle based on the fast steering mirror (FSM) is established. The calibration method of the FSM system is designed according to the obtained motion characteristics, and a nonlinear correction method is designed to decouple the LOS equation. For a two-axis fast mirror with a stroke of ±20 mrad, the LOS pointing error is

Design and performance test of a two-axis fast steering mirror driven by piezoelectric actuators

A novel design of a two-axis fast steering mirror (FSM) with piezoelectric actuators is proposed for incoherent laser beam combination. The mechanical performance of the FSM is tested. The results show that the tilting range of the mirror is about 4 mrad, and the 1st-order resonance frequency is about 250 Hz. A self-designed grating encoder is taken as the sensor, which ensures the optimal precision of 10 μrad. The novel mechanical design can meet the requirement of engineering in incoherent laser beam combination.

Modeling and control of a two-axis fast steering mirror with piezoelectric stack actuators for laser beam tracking

This paper outlines an optical beam steering system built using a two-axis fast steering mirror (FSM) with piezoelectric stack actuators to maintain precise pointing control. A novel mathematical model of the FSM is put forward by using a transfer matrix method of a multibody system to describe the dynamics characteristics and a hysteresis model to represent the hysteresis. Based on the proposed model, a model-based hybrid control is applied to force the output angle of the FSM to track the laser beam accurately thereafter. The experimental results are in accordance with the theoretical analysis. The results highlight significantly improved accuracy in the beam tracking control of the FSM.

Sensor Fault Tolerant Control of a Fast Steering Mirror System Using Adaptive PI-Based Sliding Mode Observer and Hardware Redundancy

The aim of this paper is to present a sensor fault-tolerant control (FTC) scheme for a two-axis fast steering mirror (FSM) system with minimum power consumption and without changing the controller structure. In this paper, an adaptive PI-based sliding mode observer (APISMO) is adopted firstly to estimate the fault signal, which does not require any prior knowledge of the fault. The estimation is then used by the fault isolation logic to identify the fault. The redundant sensor would be powered up to replace the faulty one when faults occur. During the backup sensor booting up, for maintaining the normal performance of the closed-loop system approximately, a fault-free estimation of the position provided by the APISMO is used as feedback signal. Experimental studies on a prototype system show that the proposed APISMO can effectively reconstruct the fault signals even when the two primary position sensors are faulty simultaneously. Meanwhile, the effectiveness and performance of the proposed scheme have been verified.

Theoretical and experimental determination of bandwidth for a two-axis fast steering mirror

Fast steering mirror (FSM) system is a precise beam steering mechanism which modulates the beam between a light source and a receiver using its reflecting surface. High bandwidth is an important property of FSM, which is associated with the response speed and stable precision. It is difficult to design the closed-loop bandwidth for FSM, which relies on the open-loop frequency response of the system and the design of the controller. A theoretical analysis, simulation, and testing method to determine an appropriate bandwidth designation for a two-axis FSM are developed in this paper. An ideal open-loop plant frequency response is compared to a final closed-loop bandwidth requirement, and then, stiffness of elastic support in each direction is researched and idea of stiffness design of elastic support is put forward. An integrated mechanical control simulation (IMCS) method is introduced to simulate the structural response and controller design synchronously to predict the final closed-loop control performance of the two-axis FSM system. Finally, the open-loop plant frequency response and closed-loop bandwidth of the assembled two-axis FSM system are tested with the results confirming the general validity of the analysis and simulation method presented in this paper.

57130 Mechanical-Control Co-simulation Method for two-axis Fast Steering Mirror system(Flexible Multibody Dynamics)

57130 Mechanical-Control Co-simulation Method for two-axis Fast Steering Mirror system(Flexible Multibody Dynamics)