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CN-121995511-A - Vibration real-time compensation device and method for cold atom gravity meter

CN121995511ACN 121995511 ACN121995511 ACN 121995511ACN-121995511-A

Abstract

The invention relates to a vibration real-time compensation device and a method for a cold atom gravity meter, the device comprises Raman laser, rubidium atomic groups, a reflecting mirror, an accelerometer, an optical phase-locked loop module, an analog-digital converter, a reference clock source, a heteronuclear FPGA, a direct frequency generation module and an upper computer. The two pairs of Raman lasers act on rubidium atomic groups oppositely in the vertical direction, the accelerometer is rigidly connected with the reflecting mirror, analog differential signals of the accelerometer enter an analog-digital converter, converted digital signals enter a heteronuclear FPGA to carry out digital calculation, and a reference clock source is used as a clock signal of a digital circuit. The signals calculated by the heteronuclear FPGA enter a direct frequency generation module and are output to an optical phase-locked loop to control the phase of the Raman laser, and the heteronuclear FPGA is communicated with an upper computer through TCP connection. The invention relates to a full-digital vibration real-time compensation device for a cold atom gravity meter, which has the advantages of large dynamic range, low noise and high-precision phase synchronization compensation capability.

Inventors

  • ZHOU JUNJIE
  • GUO BIN
  • HUANG JUNXIAO

Assignees

  • 杭州微伽量子科技有限公司

Dates

Publication Date
20260508
Application Date
20260410

Claims (10)

  1. 1. A vibration real-time compensation device for a cold atom gravity meter is characterized by comprising an interference sequence excitation mechanism, a reflecting mirror (204), an accelerometer (205), an optical phase-locked loop (206), an analog-digital converter (207), a reference clock source (208), a heteronuclear FPGA (209) and a direct digital generation module (210), The interference sequence excitation mechanism comprises Raman light A (201), raman light B (203) and rubidium atomic groups (202), wherein two beams of opposite Raman light interact with the rubidium atomic groups (202) which freely fall in vacuum, and a three-pulse sequence based on light pulses is applied to enable the rubidium atomic groups (202) to generate population interference; the accelerometer (205) is rigidly connected with a reflection mirror (204) of one of the Raman optical common paths, and after the analog differential signals output by the accelerometer (205) are subjected to digital processing by an analog-digital converter (207), digital signal streams are sent to a heteronuclear FPGA (209) for real-time processing; The speed integral signal processing chain in the heteronuclear FPGA (209) integrates and filters signals of the accelerometer (205) to obtain the instantaneous speed of the reflecting mirror (204), the heteronuclear FPGA (209) calculates Raman laser frequency correction required for compensating the instantaneous speed in real time, and generates corresponding frequency words, and the frequency words are sent to the direct digital generation module (210); The direct digital generation module (210) generates a microwave signal with the frequency accurately adjusted under the drive of the reference clock source (208), drives the optical phase-locked loop (206), and controls the frequencies of the Raman light A (201) and the Raman light B (203) in real time, so that the phase error introduced by the vibration of the reflecting mirror (204) is counteracted in the optical domain, and closed loop compensation is formed.
  2. 2. The vibration real-time compensation device for the cold atom gravity meter according to claim 1, further comprising an upper computer (211), wherein the upper computer (211) is connected with the heteronuclear FPGA (209) through a TCP network interface and is used for system state monitoring, parameter configuration and data acquisition.
  3. 3. A vibration real-time compensation device for a cold atom gravity meter is characterized in that the heteronuclear FPGA (209) comprises an analog-digital conversion driving module (102), an AXI-FIFO1 register (103), a speed integration calculating module (104), a timer module (107), a frequency word calculating module (108) and a direct frequency generation driving module (109), wherein the analog-digital conversion driving module (102) is used for receiving a data stream of the analog-digital converter (207), the data stream is connected with the AXI-FIFO1 register (103) through an AXI bus, a real-time speed value calculated by the speed integration calculating module (104) is connected to the frequency word calculating module (108), the timer module (107) is realized through high-level synthesis, a key pulse sequence time sequence signal for precisely controlling cold atom interferometry is connected to the frequency word calculating module (108), the frequency word calculating module (108) is realized through high-level synthesis, frequency words are dynamically calculated and output according to atom speed and interference sequence time sequence, the frequency word data stream is transmitted to the direct frequency generation driving module (109), and the frequency word calculating module receives external binary data through a binary parallel interface.
  4. 4. The vibration real-time compensation device for the cold atom gravity meter is characterized in that the speed integral calculation module (104) is realized through high-level synthesis, and through ADC data normalization and dimension conversion, 31-order FIR digital filtering, 10-multiplying-power CIC down sampling and first-order IIR approximate integral operation, a speed value is finally output, and all processing units can complete multi-stage signal processing through parallel calculation in a single clock period through pipeline transmission.
  5. 5. The vibration real-time compensation device for cold atom gravity meter of claim 1, wherein the device is a three-state finite state machine, and responds to external pulse sequence control to continuously output frequency word data Stream through an AXI-Stream interface.
  6. 6. A vibration real-time compensation device for a cold atom gravity meter according to claim 1, wherein the device latches an initial speed reference v 0 at the time of completion of loading of a magneto-optical trap, and then calculates a Raman laser frequency in real time according to a Doppler frequency shift formula f=f 0 + (v - v 0 ) & k_eff under the triggering of speed change in an interference process, wherein f is a Raman light frequency resonating with an atom, f 0 is a reference Raman light frequency, v is a current speed, v 0 is an initial speed, and k_eff is an effective wave vector of Raman light, and converts the effective wave vector into a frequency word output of a direct frequency generation driving module (109) through a scaling factor.
  7. 7. The real-time vibration compensation device for a cold atom gravity meter according to claim 1, further comprising a phase-locked loop (101), wherein the phase-locked loop (101) generates a system clock signal of 40 MHz by dividing and phase-locking a reference 280 MHz clock provided by a reference clock source (208), and distributes the system clock signal to an analog-digital conversion driving module (102), a speed integration calculating module (104), a timer module (107), a frequency word calculating module (108) and a direct frequency generating driving module (109).
  8. 8. A vibration real-time compensation device for a cold atom gravity meter according to claim 1, further comprising an AXI-FIFO2 register (105) and a system on chip (106), wherein key parameters of the speed integral calculation module are configured on line through an AXI-Lite interface and are provided with data stream transmission of intermediate calculation variables, and the data stream is connected to the AXI-FIFO2 register (105), read in real time through the system on chip (106) and communicated through a TCP network.
  9. 9. A vibration real-time compensation method for a cold atom gravity meter is characterized in that the device of any one of the above claims 2 to 8 is adopted, and the core workflow of the device is as follows: 1. the interference sequence excitation, wherein two beams of opposite Raman light interact with rubidium atomic groups (202) which freely fall in vacuum, and a three-pulse sequence based on light pulses is applied to cause atoms to generate population interference; 2. Vibration signal pickup, namely, the vibration of a reflecting mirror (204) of one beam of Raman light common path is equivalent to the phase noise of Raman laser, and a high-sensitivity accelerometer (205) which is closely attached to the reflecting mirror (204) measures vibration acceleration signals of the reflecting mirror in real time; 3. The signal chain processing, namely, an analog differential signal output by an accelerometer (205) is digitized by a high-precision analog-digital converter (207), and a digital signal stream is sent into a heteronuclear FPGA (209) for real-time processing; 4. Integrating and filtering acceleration signals by a speed integral signal processing chain in the heteronuclear FPGA (209) to obtain the instantaneous speed of the reflecting mirror (204), and combining with an accurate interference sequence time sequence, the heteronuclear FPGA (209) calculates Raman laser frequency correction required for compensating the speed in real time and generates corresponding frequency words; 5. The closed loop execution is that the frequency words are sent to a direct digital generation module (210), the direct digital generation module (210) generates microwave signals with the frequency accurately adjusted under the drive of a reference clock source (208), an optical phase-locked loop (206) is driven, and finally the frequencies of the Raman light A (201) and the Raman light B (203) are controlled in real time, so that phase errors caused by mirror vibration are offset in an optical domain, and closed loop compensation is formed.
  10. 10. The method for real-time vibration compensation of a cold atom gravity meter according to claim 9, further comprising the step of 6, monitoring and configuring, wherein the upper computer (211) is connected with the heteronuclear FPGA (209) through a TCP network interface and is used for system state monitoring, parameter configuration and data acquisition.

Description

Vibration real-time compensation device and method for cold atom gravity meter Technical Field The invention relates to a vibration real-time compensation device and a vibration real-time compensation method for a cold atom gravity meter, which are mainly used for eliminating the influence of carrier vibration on the Raman light frequency and the phase of the atom interferometer in real time when a mobile platform (such as a ship and a vehicle) runs, so that the precision and the stability of quantum gravity measurement in a dynamic environment are ensured. Background Cold atom gravimeters, particularly atomic interferometers, have become a leading edge technique for achieving the highest accuracy absolute gravimetric measurements. The principle is that the laser cooled atoms are used as nearly ideal gravity test quality, the laser pulse sequences (Raman light or Bragg light) are interfered with the atoms, and finally the gravity acceleration value is inverted by detecting the interference fringe phase corresponding to the atomic population distribution. The phase is extremely sensitive to the frequency and phase of the laser light acting on the atoms. In a dynamic measurement environment, such as deployment of an instrument on a moving vessel, vehicle or aircraft, vibration of the carrier itself can cause complex relative movements between the reference mirror carrying the instrument and the free-falling atoms. This relative motion introduces additional doppler shift, directly causing the frequency of the raman light to be detuned and accumulate as a non-negligible interference phase error, which in severe cases will degrade or even disappear the fringe contrast, rendering the measurement ineffective. Therefore, real-time and accurate compensation of the Raman optical frequency and phase caused by carrier vibration is a core technical bottleneck for realizing high-precision dynamic atomic gravity measurement. The existing mainstream scheme generally adopts a post-processing data processing compensation method, namely acceleration and angular velocity data recorded by a high-precision Inertial Measurement Unit (IMU) carried by the same machine are utilized after measurement is finished, a carrier motion track is reconstructed through a post-processing algorithm, compensation quantity required by theory is inverted, and then a gravity measurement result is corrected. However, the scheme does not have real-time performance, and highly depends on the accuracy of a motion model, so that the dynamic range, the noise level, the long-term stability, the phase compensation precision and other key performances of a compensation system are limited, and meanwhile, the flexible algorithm reconstruction capability is lacked. This directly limits the applicability of dynamic cold atom gravimeters in complex, strongly vibrating environments and the ultimate measurement sensitivity. The closest application patent name to the application is vibration compensation method for atomic absolute gravimeter, and the application publication number is CN 116449446A. The vibration compensation method for the atomic absolute gravimeter comprises the steps of determining an optimization target and constraint conditions for vibration compensation of the atomic absolute gravimeter, and solving an optimal gain coefficient and an optimal delay coefficient through a traversal method. And calculating the vibration condition of the Raman mirror falling every time by adopting the optimal gain coefficient and the optimal delay coefficient to obtain the change of atomic interference phases caused by vibration, further correcting the scanning speed of the Raman optical frequency, and obtaining atomic interference fringe signals for removing the influence of the vibration, namely realizing the vibration compensation of the atomic absolute gravimeter. However, the real-time performance of the method is still limited, the calculated amount of the traversal optimization process is large, high-frequency real-time compensation is difficult to realize, and the optimization process can be slowly converged or disabled under the condition of low signal-to-noise ratio or strong non-stable vibration depending on fitting quality of atomic interference fringes, so that trade-off exists between dynamic response speed and precision. Currently, the industrialization of cold atom gravimeters is gradually entering the dynamic measurement phase. Therefore, a vibration compensation device and a method with high integration level and high real-time performance, which are suitable for a high dynamic vibration environment, are needed, and can realize low-delay and high-precision vibration phase real-time feedforward compensation in the atomic interference process so as to support the reliable application of the cold atomic gravimeter in mobile platforms such as vehicles, ships, airborne vehicles and the like. Disclosure of Invention In order to solve the above-mentioned