KEYWORDS: Control systems design, Mirrors, Control systems, Fuzzy logic, Device simulation, Nonlinear control, Electronics, Quality systems, Signal generators, Seaborgium
The structure parameters of fast-steering mirror (FSM) might change with time goes by. In order to reduce the impact of this change on the output performance of FSM system, an incomplete derivative fuzzy PID control system is proposed. This control system can effectively improve the time domain quality of FSM system by optimizing the PID control parameters online. First, the dynamic model of FSM is established. Second, the initial parameters of the incomplete derivative PID control system are designed according to the frequency domain quality of the closed-loop system. Then, the rules and related factors of the fuzzy controller are designed on the basis of the initial parameters. Finally, simulation experiments are carried out. The results show that the incomplete derivative PID control system has shorter adjustment time, less overshoot and lower dependence on the parameters of FSM when compared with the fixed parameters PID control system.
Thermal blooming effect of gas on laser propagation can seriously degrade performance of far-field beam quality and energy distribution. Numerical simulation is carried out to study the influences of thermal blooming on laser propagation in line pipes. A physical model of thermal blooming effect of gas on laser propagation in an aspirating pipe is established. Axial flow and suction in the outlet are used to attenuate the thermal blooming effect. Based on the computational fluid dynamics (CFD) software, stable calculation of flow field is carried out first, then the optical field and the fluent field is coupling calculated by means of user defined function (UDF). The results show that radial flow is enhanced in the aspirating pipe and the index of refraction gradient caused by thermal blooming effect is decreased. It is indicated that the beam quality of the outlet is improved compared with the pipe model without aspirating. The optical path difference (OPD) distribution of the outlet is analyzed and decomposed by Zernike polynomials. It is shown that the defocus item of 4m aspirating pipe is decreased more than an order of magnitude compared with the 4m pipe without aspirating.
In order to improve the dynamic stiffness of telescope mount, the accuracy of aiming and stability of optical system, a topology optimization method based on the theory of variable density and taking maximum stiffness as objective function is studied. In the topology optimization analysis of elevation ring, one of the most important members of the telescope mount, two kinds of structural are designed: one is a traditional plate welding structure and the other is a combination of plate welding and truss welding. Furthermore, the stiffness and modal performance of the elevation ring in different performances are analyzed and compared. The results show that in meeting the strength and stiffness of the premise, the mass of elevation ring with plate welding and truss welding is 7.00T and the moment of inertia is 11.94 t•m2. What`s more, the total deformation in the horizontal direction and the zenith direction are 6.70μm and 55.86μm, respectively; the stress is within stress range of material's promise; the modal is 105.9Hz.Compared with the traditional structural with plate welding, this new structural design approached to ensure the dynamic stiffness while effectively reducing its own weight with reduction rate 10.7% and moments of inertia with reduction rate 12.3%. This new structural of plate welding and truss welding has obvious advantages in lightweight design. This new design method based on topology optimization will provide efficient help to later components design of the telescope mount.
KEYWORDS: Space mirrors, Mirrors, Space sensors, Remote sensing, Sensors, Finite element methods, Mirror structures, Structural design, Cameras, Space operations
To reduce the surface deformation of a space remote sensor mirror in space environments, a flexible supporting structure of space mirror is designed to improve the surface accuracy of mirror under operating conditions, making the mirror in good thermal dimensional stability and the structure stiffness meet the requirements of mechanics at the same time. Using the finite element method to do simulation analysis about the surface accuracy and structural strength and dynamic stiffness of the mirror assembly under the force-heat coupling state. Simulation results show that the first-order natural frequency of the mirror component is 393.73Hz, and the RMS values of 1g gravity respectively reach 8.920nm, 1.856nm, 4.516nm; under 1g gravity and 4 degrees centigrade rising coupling state in three directions, the RMS values respectively reach 10.02nm, 3.312nm, 5.718nm, the results meet the design specifications requirement that the RMS value less than λ/50 (λ=632.8nm). Finally, the analysis of the random vibration was carried out on the mirror components, results show that the mirror and its supporting structure was designed reasonable which can meet the requirements of space applications.
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