Vacuum optical trap is a technology that captures and manipulates particles in a near-vacuum environment by means of laser mechanical effects. It is an ideal platform for precision measurement with high quality factor. Due to its low environmental damping, vacuum optical traps require feedback cooling to reduce the equivalent temperature of particle centroid motion to prevent particle escape. Parametric feedback cooling is a mainstream solution to achieve stable trapping of particles in optical traps. Monte Carlo method and finite difference method were used to simulate the displacement fluctuation of the microsphere without feedback, and the FPGA circuit was used to output control signals with different waveforms to test the feedback cooling effect. Under the premise of reaching mK cooling level, square wave control signals have advantages in fast feedback cooling, and sine wave control signals have advantages in maintaining phase matching.
The calibration accuracy of inertial measurement unit (IMU) is one of the important factors affecting the positioning accuracy of strapdown inertial navigation system (SINS). A 24-sequence calibration rotation scheme is proposed in this paper, which improves the observability and observability degree compared with the traditional 18-sequence scheme, and makes the calibration results more accurate. Simulation results show that the calibration results of 24-sequence scheme are closer to the actual value than those of 18-sequence scheme.
Aiming at the problem that the error modulation effects are affected by the angular motions of the vehicle in the dual-axis rotational laser gyro inertial navigation system (INS), a vehicle angular motion isolation method based on attitude feedback is proposed. Based on the error equations of INS, the principles of error modulation in rotation process are analyzed. Then the relationships between the navigation results and the controlled angular velocity imposed on the rotating mechanism are established. Finally, simulation models of angular motions with various forms are established. Simulation results show that this method can effectively isolate the angular motions of the vehicle and reduce the influences of the angular motions on the rotation modulation. The navigation accuracy is significantly improved.
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