Fast steering mirrors (FSMs) are crucial components for high-precision beam pointing control, offering advantages such as high positioning accuracy, wide control bandwidth, and rapid response times. These features are vital for applications including target tracking, laser communication, and optoelectronic detection. However, the performance of traditional fast steering mirrors is limited by two main factors: first, the deflection range typically does not exceed ±1.5°, which fails to meet modern optoelectronic systems' requirements for large-angle scanning and tracking of ≥±5°; second, conventional supporting structures often employ flexible hinges or rigid axis designs. The former suffers from complex manufacturing processes, bulky structures, and high costs, while the latter is characterized by large volume, high power consumption, and inadequate precision. Therefore, developing a flexible supporting structure that combines large-angle deflection, lightweight design, ease of fabrication, and reasonable cost has become a significant technical challenge for enhancing the synergy between broad-range searching and high-precision tracking in optoelectronic systems.
A novel fast steering mirror structure based on an arc-shaped flexible supporting design is proposed, which includes four sets of composite curved beam units arranged in a rotationally symmetric manner. These units consist of a small curvature primary arc segment and a large curvature secondary arc segment, providing flexible constraints for a 40 mm diameter mirror. Utilizing Castigliano’s theorem, a theoretical model of the stiffness of the supporting structure has been developed, resulting in analytical expressions for both deflection stiffness and translational stiffness. This model elucidates the mechanisms through which geometric and material parameters affect stiffness characteristics. Finite element simulations have been conducted to systematically analyze the effects of the primary arc segment's deflection angle, as well as the thickness and width of the spring, on the three-dimensional stiffness (z-direction deflection stiffness and x, y-direction translational stiffness). The results from these simulations are compared with those derived from the theoretical model for validation. An indirect measurement system has been established. By calibrating the output coefficient of the voice coil motor, the input current is converted into the driving force exerted on the mirror frame. This driving force, in conjunction with the deflection angle measured by the auto-collimator, allows for the calculation of the equivalent deflection stiffness. Multiple repeated measurements of typical parameter samples have been performed to ensure data reliability.
The proposed arc-shaped flexible supporting design achieves a deflection angle of ±9° while overcoming the practical challenges faced by traditional flexible hinge structures concerning deflection range, weight, and cost. The stiffness analytical model based on Castigliano’s theorem aligns well with finite element simulation results. When the primary arc segment’s deflection angle (θ) is controlled within the range of 63° to 72°, with thickness (h) between 0.15 mm and 0.3 mm and width (a) from 1.3 mm to 1.9 mm, the relative error remains within 7%. Furthermore, the equivalent deflection stiffness measured from experimental samples shows a relative deviation from the theoretical values of no more than 3%, further validating the effectiveness and reliability of the model.
Through the integration of theoretical modeling, finite element simulation, and experimental validation, a flexible supporting structure suitable for large-angle fast steering mirrors has been analyzed, providing valuable insights for the design and performance optimization of similar precision adjustment mechanisms.
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