Design of Positioning Mechanism Fit Clearances Based on On-Orbit Re-Orientation Accuracy

The factors affecting the re-orientation accuracy of the on-orbit replaceable optical unit were studied, and the mathematical models of the relationships between fit clearances of positioning mechanisms and the limits of rotation angles were deduced. When the relative position relationship of positioning mechanisms was determined, fit clearances were designed according to the requirement of the rotation angle limits, and the rotation angle limits were determined to ensure that the angles were within the index range. Theodolites were used to measure the re-orientation angles of the optical unit, and the errors between the measurement angles and the real angles were deduced. Then, the numerical simulation proved that the errors were within limits. The microgravity test environment was established, and the weight of the optical unit was unloaded by a suspension method to simulate the state of the optical unit when it was replaced on orbit. The test results confirmed the correctness of the design method.