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One of the challenges in using either ground- or space--based high power lasers is keeping the beam on target in spite of various disturbances. Active control is one of the methods for maintaining laser beam direction. It requires (1) a Sensor which monitors the beam path and sends an error signal to the Controller when the beam is misaligned; (2) the Controller, after processing the error signal, sends a correction signal to (3) Actuators which control the position of (4) a Beam Steering Mirror (BSM), also in the optical path of
the laser beam. The correction signal is designed to change the position of the BSM to that the laser beam is brought back on target.
Since it is not obvious how a system of this sort will respond to various disturbances, it is helpful to be able to simulate such a system, during the design stages, so that one might have confidence that the system will work if it gets to the hardware stage. Before applying MSC/NASTRAN to the real systern,it seemed advisable to check out the implementation of MSC/NASTRAN on a small structures-optics-controls system that had the flavor of the real system but far less complexity. In that way it was hoped that procedural errors would be minimized when MSC/NASTRAN was used to analyze the real system. This paper explains the implementation of MSC/NASTRAN as applied to the analysis of a Small Structures-Optics-Controls System (SSOCS), a sketch of which is shown in Figure 1. The SSOCS comprises a Beam Steering Mirror (BSM) supported by two Voice-Coil Actuators (VCA's) (on structural support springs "8" and "9") which change the position of the BSM, a Disturbed Mirror (DM) (on structural support springs "6","7", and "57"), a Sensor which monitors translational and angular misalignrnents in the beam path, and a Controller which receives the error signals from the Sensor and sends correction signals to the VCA's. The response of the SSOCS to a step function disturbance applied to the structure of the DM via p7(t) through M7 (between springs "7" and "57") was calculated by MSC/NASTRAN; and, the results were compared against those computed for the SSOCS by a general purpose dynamics analysis program called TIMRSP. (See Block Diagram of SSOCS equations used in TIMRSP program.) The agreement between the results of MSC/NASTRAN and TIMRSP was considered excellent and increased confidence that there should be rio procedural errors.
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