Shipboard optical measurement equipment is affected by ship swaying, and a fixed order, such as “yaw, pitch and roll”, is always adopted to realize the mutual conversion between the earth reference frame and the deck reference frame. This paper simulates the solving model on six different coordinate transformation orders, finds that its error is great and it will affect the shipboard optical measurement equipment’s pointing precision of LOS (line of sight), so we put forward a LOS stabilization model based on subdivision iterative algorithm. Through the simulation and analysis, the new model can let all coordinate calculation value of different switching sequence converge to the true value, and it will improve the accuracy of existing solution model. The method is significant to improve the tracking control accuracy and data processing precision of angular measurement.
The laser beam, which is eradiated by the active detecting system in the detecting process, will come in for scattering in multi-directions by atmospheric molecules and aerosol particles. The back-scattering transmits in the reverse direction and gets in the receiving system, which will bring severe interference to the target detecting, sometimes may even make the detector get into saturation. This paper built a physical model of the atmosphere back-scattering in the active detecting system, and analyzed the impact of several factors such as geometrically configure of the system ,LOS angle deflection, the detecting distance, the intensity of the noisy light, and analyzed the interfering ability of the back-scattering light to the target echo light and then validated the illation of the interfering ability by a short distance experiment indoor . The experiment get an appropriate result with the illation, which can use for reference for the design of system involving the transmitting of the laser light in the atmosphere such as laser active detecting, range measurement with laser and so on.
In the control system of a CCD-based tracking loop for a fast steering mirror (FSM), the most effective method often employed to improve pointing performance is to increase high gain of the control system for a high bandwidth, which, however, usually suffers a great deal from a low CCD sampling rate and the mechanics of the FSM. Moreover, the amount of time delay engendered by sampling and data processing can significantly reduce the performance of a closed-loop system. Therefore, a tentative approach to the implementation of a CCD-based tracking control system with acceleration feedback is proposed. In theory, the position open loop is made of double integrators with a high bandwidth of the acceleration feedback loop; in fact, however, the acceleration open loop of the FSM response includes a quadratic differential, and it is very difficult to compensate a quadratic differential with an integral algorithm. To solve this problem, a novel acceleration closed system such as a bandpass filter is proposed. The position is reconstructed into a simple first-order filter instead of a third-order control system. In addition experimental results show that the acceleration feedback proposed here can effectively enhance the bandwidth of the closed-loop system and its trajectory tracking and pointing performance.
It's considered a hard problem in adaptive control for the nonreversible nonlinear dynamic system with SISO to be controlled using the method of neural network (NN). After analysis about the causes why this type of systems is hard to be controlled this paper presents a fuzzy neural network (FNN) based hyper-cylinder cluster and its algorithm. A theorem shows that if it is used in the control of the system mentioned above, the static error may be small arbitrarily as long as the parameter (delta) in hyper-cylinder is small enough. The feasibility and the control effectiveness of the method are examined through simulation example of nonlinear dynamic system.
This paper presents the numerical analysis about the thermal effects, produced by the high-energy laser in a beam control system, on the laser beam propagation. The propagation of laser is described by the paraxial wave equations, solved by the phase-screen technique and the FFT method. The thermal turbulence motion and the air density variation are governed by the complete Navier-Stokes equations, so that the variety factors could be in consideration. The Navier-Stokes equations are solved by using the LU-SGS factorization technique. The methods could be used for other kinds of aero-optical problems. The numerical results show that, with the additional initial thermal-phase, the energy concentration and the quality of the laser beam at far field would be prominently degraded for the typical situations.
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