Optical fiber inertial navigation system based on triaxial vibrating beam accelerometer

Abstract

The invention provides an optical fiber inertial navigation system based on a three-axis vibrating beam accelerometer, which comprises a three-axis vibrating beam accelerometer, an SOC processor or MCU processor, a satellite navigation module, a power supply module and an optical fiber gyroscope assembly, the three-axis vibrating beam accelerometer is composed of three orthogonally installed vibrating beam accelerometers, a peripheral circuit and the like, and is an integral assembly; a frequency pulse is directly output or acceleration data is output to the SOC processor or the MCU processor through an RS422 serial port; the SOC processor or the MCU processor exchanges data with the fiber-optic gyroscope assembly and the satellite navigation module through a UART serial port, and the power supply module converts an externally input 9V-36V power supply into a positive / negative 5V power supply and a positive / negative 3.3 V power supply required by the SOC processor or the MCU processor and the fiber-optic gyroscope assembly, and provides voltage for the triaxial vibrating beam accelerometer.

Description

Technical Field

[0001] The invention belongs to the technical field of high-precision inertial navigation, and specifically relates to a fiber optic inertial navigation system based on a three-axis vibrating beam accelerometer. Background Art

[0002] The quartz vibrating beam accelerometer is a new type of acceleration sensor. Its basic principle is that the change in acceleration acts on the piezoelectric vibrating beam through the lever amplification structure to cause the natural frequency of the beam to change, thereby outputting a frequency pulse proportional to the acceleration. Based on the excellent frequency selection ability and long-term stability of the quartz crystal oscillator, while also having the advantages of large range, wide bandwidth, low power consumption, and quasi-digital output, the quartz vibrating beam accelerometer has always been recognized by the industry as the preferred acceleration measurement instrument for the new generation of medium and high precision navigation systems, and even has the potential to enter high-precision navigation systems.

[0003] The use of high-precision three-axis vibrating beam accelerometers as the accelerometer sensing unit in the inertial navigation system is an important development direction of the current inertial navigation system. Compared with the fiber-optic inertial navigation system using traditional quartz flexible accelerometers, it does not require ±15V power supply, IF conversion circuit, etc. The three-axis vibrating beam accelerometer directly outputs digital signals, which can greatly reduce the size and weight of the inertial navigation, reduce power consumption and cost. Summary of the invention

[0004] The purpose of the present application is to provide an inertial navigation system based on a combination of a three-axis vibrating beam accelerometer and a fiber optic gyroscope. The three-axis vibrating beam accelerometer is an integral component that directly outputs frequency pulses or outputs acceleration data through an RS422 serial port. A SOC processor or an MCU processor, an interface circuit, a satellite navigation module, and a power supply module are combined on a circuit board, which solves the problems of large size and high power consumption of traditional fiber optic inertial navigation.

[0005] To achieve the above purpose, the technical solution adopted in the embodiment of the present application is as follows:

[0006] Provided is a fiber optic inertial navigation system based on a three-axis vibrating beam accelerometer, comprising: a three-axis vibrating beam accelerometer, a SOC processor or an MCU processor, a satellite navigation module, a power module, and a fiber optic gyroscope assembly, characterized in that:

[0007] The three-axis vibrating beam accelerometer consists of three orthogonally mounted vibrating beam accelerometers and peripheral circuits. It is an integral component that directly outputs frequency pulses or outputs acceleration data to the SOC processor or MCU processor through the RS422 serial port;

[0008] The SOC processor or MCU processor exchanges data with the fiber optic gyro component through the UART serial port;

[0009] The SOC processor or MCU processor exchanges data with the satellite navigation module through the UART serial port. The satellite navigation module is connected to the external satellite navigation antenna to provide GNSS positioning information for the inertial navigation to achieve integrated navigation.

[0010] The power module converts the external input 9V~36V power supply into the positive and negative 5V and positive and negative 3.3V power supplies required by the SOC processor or MCU processor and the fiber optic gyroscope component, and provides voltage for the three-axis vibration beam accelerometer.

[0011] Furthermore, the fiber optic gyro assembly sends the gyro angular velocity and temperature information to the SOC processor or the MCU processor via the TTL or RS422 serial port.

[0012] Furthermore, each axis of the vibrating beam accelerometer has two frequency outputs, namely FA and FB. The vibrating beam accelerometer X-axis outputs FAX and FBX signals, the vibrating beam accelerometer Y-axis outputs FAY and FBY signals, and the vibrating beam accelerometer Z-axis outputs FAZ and FBZ signals. The frequency of each axis of the vibrating beam accelerometer is output to the SOC processor.

[0013] Furthermore, the SOC processor is composed of FPGA programmable logic and ARM processor. The FPGA programmable logic end collects 6 frequency signals of the vibration beam accelerometer, and uses a high-precision clock source such as a temperature compensated crystal oscillator or a constant temperature crystal oscillator as a reference clock to perform high-precision frequency measurement on the 6 frequency signals respectively, and sends them to the ARM processor end through the AXI bus, converts the frequency into acceleration data, and performs navigation solution together with the gyroscope data.

[0014] Furthermore, the three-axis vibration beam accelerometer assembly is composed of three orthogonally mounted vibration beam accelerometers, an FPGA or SOC and peripheral circuits, and uses a high-precision clock source such as a temperature compensated crystal oscillator or a constant temperature crystal oscillator as a reference clock to perform high-precision frequency measurement on six frequency signals respectively. The three-axis vibration beam accelerometer assembly uses an FPGA or SOC to measure the frequency internally and outputs it to the SOC processor or MCU processor through the RS422 serial port for calculation.

[0015] Furthermore, it also includes a vibration processing module for processing abnormal vibration of the three-axis vibration beam accelerometer. The vibration processing module captures the abnormal vibration signal and transmits the abnormal vibration signal to the SOC processor or the MCU processor. After the SOC processor or the MCU processor reversely compensates or eliminates the abnormal vibration signal, the 6-channel frequency signal is respectively measured with high precision, and the acceleration value of each channel of the three-axis vibration beam accelerometer at the real frequency is calculated based on this.

[0016] Furthermore, the vibration processing module includes a sensing device, which may be a dynamically adjustable gyroscope or other types of high-precision sensors including a DNG sensitive element with an elastic suspension having a monolithic embedded torsion bar, to collect energy characteristic data information extracted from the acceleration and vibration spectrum in three directions of XYZ, and determine whether abnormal vibration occurs.

[0017] Furthermore, the principle of the high-precision frequency measurement algorithm takes the A channel of the X-axis accelerometer as an example. There is a high-precision timer inside the FPGA programmable logic end, which generates a pulse signal with a period of T = 1μs. Whenever a 1μs pulse arrives, the number N of rising edge pulses output by the vibrating beam accelerometer within 1μs is calculated, and the time intervals t2 and t4 from the beginning of the 1μs pulse to the time of the most recent rising edge pulse output by the vibrating beam accelerometer, as well as the periods t1 and t3 of the frequency signals output by the vibrating beam accelerometer are calculated. Then, the subdivided pulse count within this 1μs is M = N + t3 / t4-t2 / t1, and the frequency is f = M / T.

[0018] The beneficial effects of this application include:

[0019] The beneficial effect of the present invention application is that a combination of a three-axis vibrating beam accelerometer and a fiber optic gyroscope is adopted, and an interface circuit, a satellite navigation module, and a power supply module are combined on a circuit board, which can greatly reduce the volume and weight of the inertial navigation system, and solve the problems of large volume and high power consumption of traditional fiber optic inertial navigation systems.

[0020] Before high-precision frequency measurement is performed on the 6 frequency signals of the three-axis vibration beam accelerometer, abnormal vibration processing is performed. The vibration processing module captures the abnormal vibration signal and transmits the abnormal vibration signal to the SOC processor or the MCU processor. After the SOC processor or the MCU processor reversely compensates or eliminates the abnormal vibration signal, the 6 frequency signals are respectively measured with high precision. The vibration processing module processes the distortion of the acceleration count value caused by the abnormal vibration and feeds it back to the SOC processor or the MCU processor before high-precision frequency measurement is performed, and the acceleration value of each channel of the three-axis vibration beam accelerometer at the real frequency is calculated based on this. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0022] Attached Figure 1 A block diagram of a fiber optic inertial navigation system based on a three-axis vibrating beam accelerometer is applied for the present invention;

[0023] Attached Figure 2It is a principle block diagram of the output frequency pulse of the three-axis vibration beam accelerometer in the present invention application;

[0024] Attached Figure 3 The schematic diagram of the principle of the three-axis vibration beam accelerometer outputting RS422 serial port signals applied for by the present invention;

[0025] Attached Figure 4 This is a schematic diagram of the high-precision frequency measurement algorithm in the present invention. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. It should be noted that, in the absence of conflict, the various features in the embodiments of the present application can be combined with each other, and the combined embodiments are still within the scope of protection of the present application.

[0027] A fiber optic inertial navigation system based on a three-axis vibrating beam accelerometer according to the present invention is described below in conjunction with the accompanying drawings and embodiments.

[0028] The present invention provides an inertial navigation system based on a combination of a three-axis vibrating beam accelerometer and a fiber optic gyroscope, which is composed of an integrated navigation board, a fiber optic gyroscope assembly, a three-axis vibrating beam accelerometer, and structural parts. Figure 1 The present invention applies to a block diagram of a fiber optic inertial navigation system based on a three-axis vibrating beam accelerometer. The inertial navigation system of the combination of a three-axis vibrating beam accelerometer and a fiber optic gyroscope comprises: a three-axis vibrating beam accelerometer, a SOC processor or an MCU processor, a satellite navigation module, a power module, and a fiber optic gyroscope component;

[0029] The three-axis vibrating beam accelerometer consists of three orthogonally mounted vibrating beam accelerometers and peripheral circuits. It is an integral component that directly outputs frequency pulses or outputs acceleration data to the SOC processor or MCU processor through the RS422 serial port;

[0030] The SOC processor or MCU processor exchanges data with the fiber optic gyro component through the UART serial port;

[0031] The SOC processor or MCU processor exchanges data with the satellite navigation module through the UART serial port. The satellite navigation module is connected to the external satellite navigation antenna to provide GNSS positioning information for the inertial navigation to achieve integrated navigation.

[0032] The power module converts the external input 9V~36V power supply into the positive and negative 5V and positive and negative 3.3V power supplies required by the SOC processor or MCU processor and the fiber optic gyroscope component, and provides voltage for the three-axis vibration beam accelerometer.

[0033] Specifically, the fiber optic gyroscope assembly sends the gyroscope angular velocity and temperature information to the SOC processor or the MCU processor through the TTL or RS422 serial port.

[0034] The power module is an optional component, which is used to convert the external input 9V~36V power supply into the positive and negative 5V and positive and negative 3.3V power supplies required by the integrated navigation board and fiber optic gyroscope components. It can also be directly powered by an external independent power module. The satellite navigation module is also an optional component, which is used to connect the external satellite navigation antenna to provide GNSS positioning information for the inertial navigation, realize integrated navigation, or perform pure inertial navigation, or use the position information provided by external devices for integrated navigation.

[0035] In this embodiment, the processor, interface circuit, satellite navigation module, and power module are combined on a circuit board to form an integrated navigation board, which solves the problems of large size and high power consumption of traditional fiber-optic inertial navigation.

[0036] As attached Figure 2 The schematic diagram of the principle of the three-axis vibration beam accelerometer output frequency pulse is shown. Each axis of the vibration beam accelerometer has two frequency outputs, namely FA and FB. The vibration beam accelerometer X-axis outputs FAX and FBX signals, the vibration beam accelerometer Y-axis outputs FAY and FBY signals, and the vibration beam accelerometer Z-axis outputs FAZ and FBZ signals. The frequency of each axis of the vibration beam accelerometer is output to the SOC processor. The SOC processor is composed of FPGA programmable logic and ARM processor. The FPGA programmable logic end collects 6 frequency signals of the vibration beam accelerometer, and uses a high-precision clock source (such as a temperature compensated crystal oscillator or a constant temperature crystal oscillator) as a reference clock to perform high-precision frequency measurement on the 6 frequency signals respectively, and sends them to the ARM processor end through the AXI bus to convert the frequency into acceleration data, and perform navigation solution together with the gyroscope data.

[0037] In this embodiment, the integrated navigation board includes a SOC processor, an interface circuit and peripheral circuits, a satellite navigation module (not shown in the figure), a power supply module (not shown in the figure), etc., wherein the SOC processor performs high-precision frequency measurement on the frequency signal and converts it into acceleration data and performs navigation solution together with the gyroscope data.

[0038] In some embodiments, the three-axis vibration beam accelerometer assembly is composed of three orthogonally mounted vibration beam accelerometers, an FPGA or SOC, and peripheral circuits. A high-precision clock source (such as a temperature compensated crystal oscillator or a constant temperature crystal oscillator) is used as a reference clock to perform high-precision frequency measurement on six frequency signals. The three-axis vibration beam accelerometer assembly uses an FPGA or SOC to measure the frequency and outputs it to a SOC processor or an MCU processor through an RS422 serial port for calculation, as shown in the attached figure. Figure 3 The principle block diagram of the three-axis vibration beam accelerometer outputting RS422 serial port signals is shown in the figure.

[0039] In this embodiment, the acceleration data of the three-axis vibration beam accelerometer assembly is output through the RS422 serial port. The integrated navigation board is composed of a SOC processor or an MCU processor, an interface circuit, a peripheral circuit, a satellite navigation module (not shown in the figure), a power supply module (not shown in the figure), etc., which receives the acceleration data and performs navigation solution together with the gyroscope data.

[0040] The inertial navigation system based on the combination of a three-axis vibrating beam accelerometer and a fiber optic gyroscope provided in the present invention application also includes a vibration processing module (not shown) for performing abnormal vibration processing on the three-axis vibrating beam accelerometer. The vibration processing module captures the abnormal vibration signal and transmits the abnormal vibration signal to the SOC processor or the MCU processor. After the SOC processor or the MCU processor reversely compensates or eliminates the abnormal vibration signal, high-precision frequency measurement is performed on the six frequency signals respectively. That is to say, the vibration processing module processes the distortion of the acceleration count value caused by the abnormal vibration and feeds it back to the SOC processor or the MCU processor before performing high-precision frequency measurement, and uses this to calculate the acceleration value of each channel of the three-axis vibrating beam accelerometer at the true frequency.

[0041] When the vibration processing module determines that the abnormal vibration amplitude or other characteristic values ​​exceed the preset threshold, it confirms that vibration has occurred and performs abnormal vibration signal elimination processing. The vibration processing module includes a sensing device, which can be a dynamically adjustable gyroscope or other types of high-precision sensors with DNG sensitive elements of elastic suspensions with monolithic embedded torsion bars, and is connected to the drive shaft through a chain "external elastic torsion bar-intermediate ring-inner elastic torsion bar".

[0042] Collect acceleration in the three directions of XYZ and energy information extracted from the vibration spectrum, and determine whether abnormal vibration occurs.

[0043] The data acquisition device in the three directions of XYZ processes the vibration data in each direction to obtain characteristic vibration spectrum data. According to an embodiment of the present invention, the data acquisition device acquires characteristic data including vibration energy. For example, when subjected to linear acceleration, the silicon pendulum of the sensor element deviates from the equilibrium position on the elastic suspension. The capacitance between the silicon pendulum and the metallization of the glass plate changes, and the imbalance of the capacitance is converted, amplified and normalized by an electronic converter. The accuracy of measuring motion parameters during vibration under acceleration conditions is ensured, especially the effective processing of abnormal vibration or abnormal acceleration in the range of 20-2000Hz.

[0044] Frequency measurement usually adopts a vibrating beam accelerometer. During the frequency measurement process, the vibration beam accelerometer represents the acceleration input by the frequency difference of two frequency pulse signals. In order to truly reflect the input acceleration, the frequency measurement of the two frequency pulse signals must be performed synchronously and continuously. In addition, synchronous measurement by multiple vibration beam accelerometers is conducive to improving the resolution accuracy of the inertial navigation system. For this reason, the present invention applies to synchronously, high-speed and accurately measure the signal output by the vibration beam accelerometer using a high-precision clock source, so as to continuously measure the input acceleration of multiple vibration beam accelerometers in the same time interval, thereby ensuring the measurement accuracy of a single vibration beam accelerometer and the resolution accuracy of the inertial navigation system.

[0045] Details are as attached Figure 4 The figure is a schematic diagram of a high-precision frequency measurement algorithm, which is only one embodiment of the present invention. Taking the A channel of the X-axis accelerometer as an example, the principle is as follows: there is a high-precision timer inside the FPGA programmable logic end (or the FPGA programmable logic end of the SOC chip), which generates a pulse signal with a period of T=1μs. Whenever a 1μs pulse arrives, the number N of rising edge pulses output by the vibration beam accelerometer within 1μs is calculated, and at the same time, the time interval from the beginning of the 1μs pulse to the time of the most recent rising edge pulse output by the vibration beam accelerometer is calculated, as shown in t2 and t4 in the figure, and the period of the frequency signal output by the vibration beam accelerometer, as shown in t1 and t3 in the figure, then the subdivided pulse count within this 1μs is M=N+t3 / t4-t2 / t1, and the frequency is f=M / T.

[0046] The parts not involved in the present application are the same as the prior art or can be implemented by using the prior art.

[0047] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A fiber optic inertial navigation system based on a three-axis vibrating beam accelerometer, comprising: a three-axis vibrating beam accelerometer, a SOC processor or an MCU processor, a satellite navigation module, a power module, and a fiber optic gyroscope assembly, characterized in that: The three-axis vibrating beam accelerometer consists of three orthogonally mounted vibrating beam accelerometers and peripheral circuits. It is an integral component that directly outputs frequency pulses or outputs acceleration data to the SOC processor or MCU processor through the RS422 serial port; The SOC processor or MCU processor exchanges data with the fiber optic gyro component through the UART serial port; The SOC processor or MCU processor exchanges data with the satellite navigation module through the UART serial port. The satellite navigation module is connected to the external satellite navigation antenna to provide GNSS positioning information for the inertial navigation to achieve integrated navigation. The power module converts the external input 9V~36V power supply into the positive and negative 5V and positive and negative 3.3V power supplies required by the SOC processor or MCU processor and the fiber optic gyroscope component, and provides voltage for the three-axis vibration beam accelerometer.

2. The system according to claim 1, characterized in that: The fiber optic gyro assembly sends the gyro angular velocity and temperature information to the SOC processor or MCU processor through the TTL or RS422 serial port.

3. The system according to claim 1, characterized in that: Each axis of the vibrating beam accelerometer has two frequency outputs, namely FA and FB. The X-axis of the vibrating beam accelerometer outputs FAX and FBX signals, the Y-axis of the vibrating beam accelerometer outputs FAY and FBY signals, and the Z-axis of the vibrating beam accelerometer outputs FAZ and FBZ signals. The frequency of each axis of the vibrating beam accelerometer is output to the SOC processor.

4. The system according to claim 3, characterized in that: The SOC processor consists of FPGA programmable logic and ARM processor. The FPGA programmable logic collects the 6-channel frequency signals of the vibration beam accelerometer, and uses a high-precision clock source such as a temperature compensated crystal oscillator or a constant temperature crystal oscillator as a reference clock to perform high-precision frequency measurement on the 6-channel frequency signals, and sends them to the ARM processor through the AXI bus, converts the frequency into acceleration data, and performs navigation solution together with the gyroscope data.

5. The system according to claim 1, characterized in that: The three-axis vibration beam accelerometer assembly consists of three orthogonally mounted vibration beam accelerometers, FPGA or SOC and peripheral circuits, and uses a high-precision clock source such as a temperature compensated crystal oscillator or a constant temperature crystal oscillator as a reference clock to perform high-precision frequency measurement on six frequency signals. The three-axis vibration beam accelerometer assembly uses FPGA or SOC for frequency measurement and outputs it to the SOC processor or MCU processor through the RS422 serial port for calculation.

6. The system according to claim 2, characterized in that: It also includes a vibration processing module for processing abnormal vibrations of the three-axis vibration beam accelerometer. The vibration processing module captures abnormal vibration signals and transmits the abnormal vibration signals to the SOC processor or the MCU processor. After the SOC processor or the MCU processor reversely compensates or eliminates the abnormal vibration signals, high-precision frequency measurement is performed on the six frequency signals respectively, and the acceleration value of each channel of the three-axis vibration beam accelerometer at the true frequency is calculated based on this.

7. The system according to claim 6, characterized in that: The vibration processing module includes a sensing device, which may be a dynamically adjustable gyroscope or other types of high-precision sensors containing a DNG sensitive element with a monolithic embedded torsion bar elastic suspension, to collect energy characteristic data information extracted from the acceleration and vibration spectrum in three directions of XYZ, and determine whether abnormal vibration occurs.

8. The system according to any one of claims 4 to 6, characterized in that: The principle of the high-precision frequency measurement algorithm is to take the A channel of the X-axis accelerometer as an example. There is a high-precision timer inside the FPGA programmable logic end, which generates a pulse signal with a period of T = 1μs. Whenever a 1μs pulse arrives, the number N of rising edge pulses output by the vibrating beam accelerometer within 1μs is calculated, and the time intervals t2 and t4 from the beginning of the 1μs pulse to the time of the most recent rising edge pulse output by the vibrating beam accelerometer, as well as the periods t1 and t3 of the frequency signal output by the vibrating beam accelerometer are calculated. Then, the subdivided pulse count within this 1μs is M = N + t3 / t4-t2 / t1, and the frequency is f = M / T.

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