Closed-loop control system and method for optical floating gyroscope rotor speed based on optical power modulation

Abstract

The present invention provides a closed-loop control system and method for the rotor speed of an optical floating gyroscope based on optical power modulation. Laser power is modulated at high frequency using an acousto-optic modulator (AOM) to precisely control the torque applied to the rotor particles by circularly polarized light. When the spatial attitude of the optical axis changes due to precession, the polarization component of the scattered light changes, and the photon angular momentum transfer value changes, causing the speed to fluctuate. The speed signal is directly measured by a photodetector and transmitted to a controller. Through a control algorithm, an AOM modulation signal is generated to change the laser power, ensuring that the particle speed remains within a predetermined range. The present invention can effectively solve the problems of reduced accuracy, increased noise, and accumulated errors in the prior art, thereby improving the operating accuracy and stability of the optical floating measurement system.

Description

Technical Field

[0001] The present invention belongs to the field of gyroscope technology and optical measurement, and particularly relates to a closed-loop control system and method for an optically floating gyroscope rotor speed based on optical power modulation. Background Art

[0002] The optical floating gyroscope is a high-precision instrument that uses the radiation pressure generated by lasers to capture and suspend microparticles. The angular momentum transfer of light drives the microparticles to spin at high speed, thereby reflecting the external angular velocity input. It has the advantages of contactless measurement, high precision, low cost and miniaturization, and is widely used in aerospace, navigation systems, precision engineering measurement and other fields. The working principle of the optical floating gyroscope is based on the conservation of angular momentum. That is, when the external angular velocity acts on the suspended rotor particles, the particles will produce a precession angle, the spatial position of the optical axis will change, the angular momentum transfer amount of the circularly polarized laser to the particles will change, and the particle rotation speed will fluctuate accordingly. These fluctuations can reflect the size of the precession angle, and then resolve the external angular velocity input. For example, Chinese patent application CN116448086A discloses an optically suspended microsphere rotor gyroscope based on optical axis attitude angle detection. The invention works according to the above principle and reflects the external angular velocity input by measuring the particle rotation speed.

[0003] However, due to this operating mode and measurement method, existing optical floating gyroscopes suffer from reduced measurement accuracy, increased noise, and accumulated deviations. Furthermore, the vacuum chamber may experience pressure fluctuations, making it inaccurate to measure the external angular velocity input using rotational speed. Summary of the Invention

[0004] In order to solve the problems of decreased accuracy, increased noise and error accumulation in the prior art, the present invention provides a closed-loop control method for the rotor speed of an optical floating gyroscope based on optical power modulation, so as to improve the working accuracy and stability of the optical floating measurement system.

[0005] This invention uses optical power modulation technology to precisely control the rotational speed of the working particles in an optically floating gyroscope, improving its operating accuracy and stability. This technology uses an acousto-optic modulator (AOM) to modulate laser power at high frequency, thereby controlling the torque exerted by the circularly polarized light on the rotor particles, achieving closed-loop control of the particle's rotational speed. This invention can be applied to the research of prototypes and experimental devices for optically floating gyroscopes and is therefore widely applicable to applications requiring high-precision gyroscopes, such as aerospace, navigation, and precision measurement.

[0006] An acousto-optic modulator (AOM) is an optical modulator that uses the acousto-optic effect to control diffracted light. It can control the power of a laser beam using an electronic drive signal. It primarily consists of an acoustic wave transducer and a crystal that serves as an optical medium. The AOM driver drives the piezoelectric material that acts as the acoustic wave transducer to generate high-frequency sound waves. When the high-frequency sound waves pass through the crystal, a dynamic grating is formed in the medium. As the laser beam passes through this area, it interacts with the sound waves, causing diffraction and frequency shift. By adjusting the frequency and intensity of the sound waves, parameters such as the frequency, intensity, and direction of light can be controlled, achieving optical modulation.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] The optical floating gyroscope rotor speed closed-loop control system based on optical power modulation includes a 532nm laser, an AOM, a first plano-convex lens, a second plano-convex lens, a first linear polarizer, an AOM driver, a CCD camera, a 532nm filter, a dichroic mirror, a λ / 4 glass, a 100x flat-field objective lens, a gyroscope vacuum chamber, a 0.68NA aspheric mirror, a first beam splitter prism, a coaxial light source, a second beam splitter prism, a linear polarizer, a focusing plano-convex lens, a photodetector, a polarization analyzer, and a controller module; the high-performance Gaussian beam generated by the 532nm laser passes through the AOM. After power modulation, the beam is expanded by the beam expander group composed of the first plano-convex lens and the second plano-convex lens, and the linearly polarized light is converted into standard circularly polarized light through the first linear polarizer, the dichroic mirror and the λ / 4 glass. Optical focusing is performed by a 100x flat-field objective lens, and the particles are captured in the gyro vacuum chamber. The scattered light is converged by a 0.68NA aspheric mirror and changed into a parallel beam to be sent to the subsequent detection system. The first beam splitter prism is used to change the direction of the laser, and the scattered light is divided into two beams in the subsequent second beam splitter prism. One beam is converged into the photodetector through the second linear polarizer and the focusing plano-convex lens. The photodetector measures the rotation speed data and inputs it into the controller module. The other beam goes to the polarization analyzer to directly measure the polarization degree of the scattered light, which is used as a gyro signal to calculate the external input angular velocity. The optical path system composed of a coaxial light source, a 532nm filter and a CCD camera is used to intuitively observe the dynamic performance of the captured particles in the vacuum chamber.

[0009] Furthermore, the miniaturized gyro vacuum chamber suppresses the influence of air fluctuations on the dynamic performance of the rotor.

[0010] Furthermore, the polarization analyzer calculates the spatial posture change of the particle optical axis in real time, and then calculates the size and change of the gyro precession angle, and solves the external angular velocity input according to the optical floating gyro precession equation.

[0011] The present invention also provides a closed-loop control method for the rotor speed of an optical floating gyroscope based on optical power modulation, comprising the following steps:

[0012] Step S1: Turn on the 532nm laser, set the initial speed setting value and control parameters of the controller module, and the AOM driver receives the control signal from the controller module to generate a high-frequency modulation signal to put the AOM into the initial working state and stabilize the laser power. The laser beam captures the particles in the gyro vacuum chamber and drives their spin. The optical floating gyroscope system is allowed to operate stably until the frequency of the light intensity signal collected by the photodetector stabilizes, that is, the speed signal reaches the set value and remains stable. The Stokes parameter of the scattered light output by the polarization analyzer remains constant.

[0013] Step S2: Record the light intensity signal output by the photodetector and the polarization degree information output by the polarization analyzer in step S1, calculate the rotation speed of the particle and the angle between the optical axis of the particle and the propagation direction of the laser, and obtain the initial spatial orientation of the optical axis of the particle;

[0014] Step S3: Input the external angular velocity. The photodetector measures the light signal that passes through the second linear polarizer and is focused by the focusing plano-convex lens. The electrical signal converted by the photodetector is subjected to an FFT operation after the controller module to obtain the particle rotation speed signal. This signal serves as the feedback value of the controller module for closed-loop control. The control signal drives the AOM to change the optical power to ensure that the particle rotation speed remains constant under the angular velocity input working state.

[0015] Step S4: Read the changes in the Stokes parameters of the scattered light output by the polarization analyzer under the angular velocity input state, and calculate the angle between the optical axis of the particle and the propagation direction of the laser light at high speed in the controller module to obtain the spatial orientation and changes of the optical axis of the particle under the angular velocity input working state in real time;

[0016] Step S5: Compare the initial spatial orientation of the optical axis obtained in step S2 to calculate the precession angle of the particle, and calculate the external angular velocity input according to the gyro precession equation.

[0017] Furthermore, in step S1, the frequency and amplitude of the high-frequency modulation signal driving the AOM are pre-set according to the characteristics of the rotor particles and the set rotation speed; under the action of the AOM, the optical floating gyroscope adjusts the driving light power within the range of 10mW-200mW, thereby freely controlling the rotation speed of the particle rotor.

[0018] Furthermore, in step S2, the frequency of the particle rotation signal obtained by the photodetector is half of the frequency of the periodic change of the light intensity after the scattered light passes through the second linear polarizer. The frequency of the particle rotation signal obtained by the photodetector is used as a feedback value for closed-loop control and is involved in the calculation.

[0019] Furthermore, in step S3, the torque exerted on the rotor particles by the circularly polarized light is precisely controlled by modulating the laser power at high frequency of the AOM, thereby achieving closed-loop control of the gyro rotor speed of the optical floating gyroscope.

[0020] Beneficial effects:

[0021] In order to solve the problems of excessive vacuum chamber volume and air pressure fluctuation, the present invention uses a miniaturized vacuum chamber to load micro-particles, further reducing the volume of the experimental instrument and simplifying the system design. The sealed chamber structure can also eliminate the problem of air pressure fluctuation and avoid speed fluctuation caused by external noise; optimize the gyroscope signal acquisition method, use a polarization analyzer to directly read the Stokes parameters of the scattered light, quantify the ellipticity of the scattered light, calculate the angular momentum transfer of the photon, and thus obtain the spatial position of the optical axis and the external angular velocity input. Compared with the speed reflection method, it is more direct and clear, and the parameter calculation is more accurate; the present invention proposes a closed-loop method for the speed of an optical floating gyroscope for the first time. This innovation has significant advantages and characteristics.

[0022] In summary, the present invention can effectively suppress the rotational speed fluctuations caused by external angular velocity through optical power modulation and closed-loop control, thereby improving the measurement accuracy of the optical floating gyroscope for external angular velocity and further improving the measurement range. The closed-loop control system can monitor and adjust the rotational speed of the rotor particles in real time to ensure that it remains within a predetermined range, thereby enhancing the stability of the system. Due to the use of high-frequency modulation and fast feedback control, the present invention can quickly respond to changes in external angular velocity and improve the dynamic response performance of the system. The present invention significantly improves the performance of the optical floating gyroscope through innovative optical power modulation and closed-loop control methods, and has important technical value and broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of the optical floating gyroscope rotor speed closed-loop control system based on optical power modulation of the present invention;

[0024] Figure 2 The figure is a flow chart of the closed-loop control method of the optical floating gyroscope rotor speed based on optical power modulation of the present invention.

[0025] Among them, the figure markings are: 1-532nm laser; 2-AOM; 3-first plano-convex lens; 4-second plano-convex lens; 5-first linear polarizer; 6-AOM driver; 7-CCD camera; 8-532nm filter; 9-dichroic mirror; 10-λ / 4 glass slide; 11-100x flat-field objective lens; 12-gyro vacuum chamber; 13-0.68NA aspheric mirror; 14-first beam splitter prism; 15-coaxial light source; 16-second beam splitter prism; 17-second linear polarizer; 18-focusing plano-convex lens; 19-photodetector; 20-polarization analyzer; 21-controller module. DETAILED DESCRIPTION

[0026] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only intended to illustrate the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0027] like Figure 1 As shown, the optical floating gyroscope rotor speed closed-loop control system based on optical power modulation of the present invention includes a 532nm laser 1, an AOM 2, a first plano-convex lens 3, a second plano-convex lens 4, a first linear polarizer 5, an AOM driver 6, a CCD camera 7, a 532nm filter 8, a dichroic mirror 9, a λ / 4 glass slide 10, a 100x flat-field objective lens 11, a gyroscope vacuum chamber 12, a 0.68NA aspheric mirror 13, a first beam splitter prism 14, a coaxial light source 15, a second beam splitter prism 16, a second linear polarizer 17, a focusing plano-convex lens 18, a photodetector 19, a polarization analyzer 20, and a controller module 21. The high-performance Gaussian beam generated by the 532nm laser 1 passes through the AOM. After power modulation at 2, the beam is expanded by a beam expander consisting of a first plano-convex lens 3 (focal length f = 30 mm) and a second plano-convex lens 4 (focal length f = 100 mm). The linearly polarized light is converted to standard circularly polarized light by a first linear polarizer 5, a dichroic mirror 9, and a λ / 4 glass slide 10. Optically focused by a 100x plan-field objective 11, the particles are captured in a gyroscopic vacuum chamber 12. The scattered light is converged by a 0.68NA aspheric mirror 13, converted into a parallel beam and fed into the subsequent detection system. A first beamsplitter prism 14 primarily redirects the laser beam. The subsequent second beamsplitter prism 16 splits the beam into two beams. One beam passes through a second linear polarizer 17 and a focusing plano-convex lens 18 and converges onto a photodetector 19, which measures the rotational velocity and inputs it into a controller module 21. The other beam passes to a polarization analyzer 20, which directly measures the ellipticity of the scattered light and uses it as a gyroscopic signal to calculate the external input angular velocity. The optical system composed of the coaxial light source 15, the 532 nm filter 8 and the CCD camera 7 is used to visually observe the dynamic performance of the captured particles in the vacuum chamber.

[0028] Preferably, the miniaturized gyro vacuum chamber 12 suppresses the influence of air fluctuations on the dynamic performance of the rotor, further simplifying the system structure design.

[0029] Preferably, the polarization analyzer directly reads the polarization degree of the scattered light, calculates the spatial posture change of the particle optical axis in real time, and then calculates the size and change of the gyro precession angle, and solves the external angular velocity input according to the optical floating gyro precession equation.

[0030] The present invention uses a controller module to assign initial parameters to AOM 2, which then modulates the laser power output by a 532nm laser 1 at high frequency to generate a modulated beam with a specific intensity. This modulated beam is focused onto the rotor particles in the gyro vacuum chamber 12 via a 100x flat-field objective lens 11. The radiation pressure of the light captures the suspended particles and drives their rotation. After a period of time, the particle's motion stabilizes, the rotational speed reaches the set value, and the angle between the optical axis and the beam propagation direction remains constant. AOM 2 is an acousto-optic modulator. When an external angular velocity acts on the rapidly spinning particles, the particle's spin axis precesses in a direction orthogonal to the input angular velocity. This ultimately manifests as a constant precession angle, causing the angle between the optical axis and the beam propagation direction to change. A photodetector 19 collects the differential photoelectric signal of the scattered light and transmits it to controller module 21. Controller module 21 performs an FFT (Fourier transform) on the received signal to determine the particle's rotational speed. A PID algorithm is then used to generate the corresponding AOM modulation signal to adjust the optical power. This modulation signal maintains the particle rotational speed at a set value. Based on the AOM modulation signal generated by the controller module, the AOM driver 6 adjusts the operating state of the AOM 2, thereby varying the laser power to precisely control the torque applied to the rotor particle. Closed-loop control ensures that the rotor particle's rotational speed remains within a predetermined range. A polarization analyzer 20 is used to obtain gyroscopic signals. Using this polarization analyzer 20, the Stokes parameters of the emitted ellipsoidal light can be directly calculated, enabling the angle between the optical axis and the direction of light propagation to be calculated.

[0031] like Figure 2 As shown, the optical floating gyroscope rotor speed closed-loop control method based on optical power modulation of the present invention includes the following steps:

[0032] Step S1: Turn on the 532nm laser 1. Initial speed settings and control parameters are given to the controller module 21. The AOM driver 6 receives control signals from the controller module 21 and generates a high-frequency modulation signal with a specific frequency and amplitude, initializing the AOM 2 and stabilizing the laser power. This laser beam captures particles in the gyro vacuum chamber 12 and drives their spin. The optical floating gyroscope system then waits for stable operation until the frequency of the light intensity signal collected by the photodetector 19 stabilizes, meaning the speed signal reaches and remains stable at the set value. The Stokes parameters of the scattered light output by the polarization analyzer 20 remain constant.

[0033] Step S2: Record the light intensity signal output by the photodetector 19 and the polarization degree information output by the polarization analyzer 20 in step S1, calculate the rotation speed of the particle and the angle between the optical axis of the particle and the propagation direction of the laser, and obtain the initial spatial orientation of the optical axis of the particle;

[0034] Step S3: Input the external angular velocity. The photodetector 19 measures the light signal that passes through the second linear polarizer 17 and is focused by the focusing plano-convex lens 18. The electrical signal converted by the photodetector 19 is subjected to an FFT operation after the controller module 21 to obtain the particle rotation speed signal. This signal is used as the feedback value of the controller module 21 for closed-loop control. The control signal drives the AOM 2 to change the optical power to ensure that the particle rotation speed remains constant under the angular velocity input working state.

[0035] Step S4: Reading the change in the Stokes parameter of the scattered light output by the polarization analyzer 20 under the angular velocity input state, and calculating the angle between the optical axis of the particle and the propagation direction of the laser light in the controller module at high speed, thereby obtaining the spatial orientation and change of the optical axis of the particle under the angular velocity input working state in real time;

[0036] Step S5: Compare the initial spatial orientation of the optical axis in step S2 to calculate the precession angle of the particle, and calculate the external angular velocity input according to the gyro precession equation.

[0037] Specifically, in step S1, the frequency and amplitude of the high-frequency modulation signal driving the AOM are pre-set based on the characteristics of the rotor particles and the desired rotational speed. Under the influence of AOM 2, the optical floating gyroscope can adjust the driving light power within a range of 10mW-200mW, thereby freely controlling the rotational speed of the particle rotor.

[0038] Specifically, in step S2, the frequency of the particle rotation signal obtained by the photodetector is half of the frequency of the periodic variation of the light intensity after the scattered light passes through the linear polarizer 17. This frequency signal is used as a feedback value for the closed-loop control operation.

[0039] Specifically, in step S3, the torque exerted on the rotor particles by the circularly polarized light is precisely controlled by the high-frequency modulated laser power of the AOM 2, thereby achieving closed-loop control of the gyro rotor speed of the optical floating gyroscope.

Claims

1. A closed-loop control system for the rotor speed of an optical floating gyroscope based on optical power modulation, characterized in that: It includes 532nm laser, AOM, first plano-convex lens, second plano-convex lens, first linear polarizer, AOM driver, CCD camera, 532nm filter, dichroic mirror, λ / 4 glass, 100x flat field objective lens, gyro vacuum chamber, 0.68NA aspheric mirror, first beam splitter prism, coaxial light source, second beam splitter prism, linear polarizer, focusing plano-convex lens, photodetector, polarization analyzer, and controller module; the high-performance Gaussian beam generated by the 532nm laser passes through the AOM. After power modulation, the beam is expanded by the beam expander group composed of the first plano-convex lens and the second plano-convex lens, and the linearly polarized light is converted into standard circularly polarized light through the first linear polarizer, the dichroic mirror and the λ / 4 glass. Optically focused by a 100x flat-field objective lens, the particles are captured in the gyro vacuum chamber, and the scattered light is converged by a 0.68NA aspheric mirror, changed into a parallel beam and sent to the subsequent detection system. The first beam splitter prism is used to change the direction of the laser, and the scattered light is divided into two beams in the subsequent second beam splitter prism. One beam is converged by the second linear polarizer and the focusing plano-convex lens to the photodetector, which measures the rotation speed data and inputs it into the controller module. The other beam of light is sent to the polarization analyzer to directly measure the polarization degree of the scattered light, which is used as a gyro signal to calculate the external input angular velocity. The optical path system composed of a coaxial light source, a 532nm filter and a CCD camera is used to intuitively observe the dynamic performance of the captured particles in the vacuum chamber. The electrical signal converted by the photodetector is subjected to FFT calculation after the controller module to obtain the particle speed signal, which is used as the feedback value of the controller module for closed-loop control. The control signal drives the AOM to change the optical power to ensure that the particle speed remains constant under the angular velocity input working state; Read the changes in the Stokes parameters of the scattered light output by the polarization analyzer under the angular velocity input state, and quickly calculate the angle between the optical axis of the particle and the laser propagation direction in the controller module to obtain the spatial orientation and changes of the particle optical axis under the angular velocity input working state in real time; The particle's precession angle is calculated by comparing it with the initial spatial orientation of the optical axis, and the external angular velocity input is calculated based on the gyro precession equation.

2. The optical floating gyroscope rotor speed closed-loop control system based on optical power modulation according to claim 1 is characterized in that: The miniaturized gyro vacuum chamber suppresses the influence of air fluctuations on the dynamic performance of the rotor.

3. The optical floating gyroscope rotor speed closed-loop control system based on optical power modulation according to claim 1 is characterized in that: The polarization analyzer calculates the spatial posture change of the particle optical axis in real time, and then calculates the size and change of the gyro precession angle, and solves the external angular velocity input according to the optical floating gyro precession equation.

4. The optical floating gyroscope rotor speed closed-loop control system based on optical power modulation according to claim 1 is characterized in that: The steps include: Step S1: Turn on the 532nm laser, set the initial speed setting value and control parameters of the controller module, and the AOM driver receives the control signal from the controller module to generate a high-frequency modulation signal to put the AOM into the initial working state and stabilize the laser power. The laser beam captures the particles in the gyro vacuum chamber and drives their spin. The optical floating gyroscope system is allowed to operate stably until the frequency of the light intensity signal collected by the photodetector stabilizes, that is, the speed signal reaches the set value and remains stable. The Stokes parameter of the scattered light output by the polarization analyzer remains constant. Step S2: Record the light intensity signal output by the photodetector and the polarization degree information output by the polarization analyzer in step S1, calculate the rotation speed of the particle and the angle between the optical axis of the particle and the propagation direction of the laser, and obtain the initial spatial orientation of the optical axis of the particle; Step S3: Input the external angular velocity. The photodetector measures the light signal that passes through the second linear polarizer and is focused by the focusing plano-convex lens. The electrical signal converted by the photodetector is subjected to an FFT operation after the controller module to obtain the particle rotation speed signal. This signal serves as the feedback value of the controller module for closed-loop control. The control signal drives the AOM to change the optical power to ensure that the particle rotation speed remains constant under the angular velocity input working state. Step S4: Read the changes in the Stokes parameters of the scattered light output by the polarization analyzer under the angular velocity input state, and calculate the angle between the optical axis of the particle and the propagation direction of the laser light at high speed in the controller module to obtain the spatial orientation and changes of the optical axis of the particle under the angular velocity input working state in real time; Step S5: Compare the initial spatial orientation of the optical axis obtained in step S2 to calculate the precession angle of the particle, and calculate the external angular velocity input according to the gyro precession equation.

5. The closed-loop control method for the rotor speed of an optical floating gyroscope based on optical power modulation according to claim 4 is characterized in that: In step S1, the frequency and amplitude of the high-frequency modulation signal driving the AOM are pre-set according to the characteristics of the rotor particles and the set rotation speed; under the action of the AOM, the optical floating gyroscope adjusts the driving light power within the range of 10mW-200mW, thereby freely controlling the rotation speed of the particle rotor.

6. The closed-loop control method for the rotor speed of an optical floating gyroscope based on optical power modulation according to claim 4, characterized in that: In step S2, the frequency of the particle rotation signal obtained by the photodetector is half of the frequency of the periodic change of the light intensity after the scattered light passes through the second linear polarizer. The frequency of the particle rotation signal obtained by the photodetector is used as a feedback value for closed-loop control.

7. The closed-loop control method for the rotor speed of an optical floating gyroscope based on optical power modulation according to claim 4, characterized in that: In step S3, the torque exerted by the circularly polarized light on the rotor particles is precisely controlled by modulating the laser power at high frequency of the AOM, thereby achieving closed-loop control of the gyro rotor speed of the optical floating gyroscope.

Images