Nuclear magnetic resonance (NMR) oscillator is an optical atomic sensor which is developed to measure inertial angular velocity with navigation grade accuracy. It utilizes semiconductor laser, miniaturized magnetic shield and atom vapor cell to realize nuclear magnetic resonance, optical pump and detection in a very small volume (about 10cc to 100cc). NMR oscillator is much more compact than other classic gyros such as fiber optic gyro (FOG), so it is a potential substitution of FOG in the next generation compact navigation grade IMU. To achieve this goal, it is essential to analyse the short-term noise and long-term drift performance of the NMR oscillator. It is also necessary to decompose and track the random error source for further improvements of the device. We propose using the Allan Variance (AVAR) method to both analyse the drift performance and characterize the short-term noise. We also built an NMR oscillator prototype to test and verify the method’s accuracy. Theory analysis and experimental results are compared with the classic FOG for deeper comprehension of the differences between these two inertial sensors. We hope this is helpful for those who design the IMU system.
Measuring the transverse relaxation time of noble gas nuclei with the Free-induction-decay (FID) signal is one of the key technical challenges and prerequisites for the nuclear magnetic resonance gyroscope (NMRG), which is a quantum sensor to form an inertial navigation system. In this paper, a novel method to estimate the parameter of the freeinduction-decay signal based on the adaptive internal model (AIM) controller is proposed and it is verified by the free induction decay data collected from the gyro prototype. In the proposed methods, the AIM con troller can provide estimates of the FID signal, such as the amplitude, the frequency, and the relaxation time. The feasibility of the scheme is proven by theoretical analysis and the reliability of the method is verified by the test results.
Navigation technology is crucial to the national defense and military, which can realize the measurement of orientation, positioning, attitude and speed for moving object. Inertial navigation is not only autonomous, real-time, continuous, hidden, undisturbed but also no time-limited and environment-limited. The gyroscope is the core component of the inertial navigation system, whose precision and size are the bottleneck of the performance. However, nuclear magnetic resonance gyroscope is characteristic of the advantage of high precision and small size. Nuclear magnetic resonance gyroscope can meet the urgent needs of high-tech weapons and equipment development of new generation. This paper mainly designs a set of photoelectric signal processing system for nuclear magnetic resonance gyroscope based on FPGA, which process and control the information of detecting laser .The photoelectric signal with high frequency carrier is demodulated by in-phase and quadrature demodulation method. Finally, the processing system of photoelectric signal can compensate the residual magnetism of the shielding barrel and provide the information of nuclear magnetic resonance gyroscope angular velocity.
The nuclear magnetic resonance gyroscope serves as a new generation of strong support for the development of high-tech weapons, it solves the core problem that limits the development of the long-playing seamless navigation and positioning. In the NMR gyroscope, the output signal with atomic precession frequency is detected by the probe light, the final crucial photoelectric signal of the probe light directly decides the quality of the gyro signal. But the output signal has high sensitivity, resolution and measurement accuracy for the photoelectric detection system. In order to detect the measured signal better, this paper proposed a weak photoelectric signal rapid acquisition system, which has high SNR and the frequency of responded signal is up to 100 KHz to let the weak output signal with high frequency of the NMR gyroscope can be detected better.
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