This paper presents a part of an initial study on a collaborative control strategy for multiple active mirrors in a large telescope. The study examines the structural dynamics from individual substructures to the overall telescope, providing a detailed mathematical formulation for assembling subunits within a comprehensive model. Additionally, a hierarchical control system is envisioned, integrating various sensor and actuator sources to correct the mirror shape across different temporal and spatial bandwidths.
This short invited paper reviews part of recent developments in designing and fabricating actively morphed thin-shell reflectors with unimorph actuators, which hold potential for use in space, particularly for large-aperture applications in space observation and communication. The discussion covers several technological updates and iterations and highlights complementary aspects relative to the existing literature on their applications.
This conference paper presents an initial investigation on implementing an AO system on small satellites in VLEO, focusing on the complex orbital environmental factors that affect the satellite’s structure. Particular attention is given to the uncertainties of these excitation factors, which can cause unexpected motions and attitude changes. A novel control strategy is proposed, incorporating additional sensors into the system, with several self-sensing architectures implemented. The control scheme outlined in this study is intended for potential iterations of the technology in future applications.
This paper proposes the implementation of a self-deformation estimation strategy for an active mirror within a framework of mechanoelectrical sensing. This architecture can collaborate with conventional optical wavefront sensors in a complementary manner, integrating information from various working bands and noise levels. The aim is to enhance the shape maintenance of the Active Optics mirror and improve its capability to reject disturbances from external sources. The paper firstly discusses the theoretical background of relative shape detection, providing examples such as voice coil Deformable Mirrors with an out-of-plane actuator/sensing architecture. Then, it illustrates the transverse sensing of the mirror surface in modal coordinates, with applications on stacked piezoelectric mirrors and unimorph Deformable Mirrors. Finally, a design of the active mirror for space Active Optics with internal actuator/sensor units is proposed.
This paper presents a study on the excitation method for a thin-shell active reflector with an electric actuation source. The actuators are considered with very small dimensions. We discuss two main topics: the distinguishable mechanical behavior of the quasi-static response of unimorph composite charging by a distributed field, focusing on reduced morphing amplitudes and limited influencing areas. Then, we investigate the method of computing the distributed electric field for adjusting the shape using an equivalent mechanical model with various load sets of self-equilibrium forces and moments. The correction process can be iterative, and the potential update to change the shape is linearly related to the distribution of the mean curvature. Finally, we discuss downsampling issues and present some initial numerical results. Additionally, we propose a framework of hierarchically iterative charging strategy.
This paper explores a hierarchical shape control method for large, lightweight polymer mirrors with unimorph actuation. Two methods of generating strain-driven forces are discussed. The initial focus is on the study of linear interaction matrices for various actuation configurations. Subsequently, control algorithms are designed for a large active optics aperture. The controlled degrees of freedom for the injection spots of electron flux are estimated, and criteria for examining iteration convergence are proposed.
This paper delves into the investigation of morphing capabilities in a unimorph deformable mirror within the context of Active Optics applications, specifically when exposed to environmental factors in space. The study encompasses an array of factors that contribute to disturbances, encompassing intricate thermal and mechanical conditions that impact the ferroelectric properties of strain actuation. The study also focuses on the effects of stress-induced geometric stiffness on the mirror's structural rigidity. In addition, the paper envisions the potential utilization of these mirrors in lightweight satellite systems.
This paper proposes an ultra-lightweight design of space reflectors made of polymer thin layers, to increase the aperture size of space observation platform with higher imaging resolution. The morphing capabilities are evaluated with both petal-like segmented and monolithic configured reflectors as the primary mirror of space telescopes, by forming a set of Zernike modes. Finally, a compound control strategy using a deformable relay mirror to compensate the residual surface error corrected partially by the active unimorph primary mirror.
This paper discusses a new concept of the active spherical shell reflector made of polymer materials, which exhibits excellent areal density and stowability and paves the way to future lightweight large-aperture space telescopes for potential observation of various wavelengths. The shape control of a small-scale technology demonstrator is performed, and the design criteria of patterned electrodes is proposed. The stress-stiffening effect on the piezoelectric strain actuation is investigated and the influence of manufacturing errors on the structural dynamics is also considered to give a preliminary study on evaluating the morphing capability under complex environment in space.
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