Strapdown inertial navigation device

Abstract

The invention discloses a strapdown inertial navigation device, and belongs to the technical field of navigation, the strapdown inertial navigation device comprises a shell and a mounting bracket, the shell is composed of a side plate, a bottom plate and a top plate, the bottom plate and the top plate are fixed on the side plate through screws, and the device mounting bracket is fixed on the bottom plate through pins; the mother board, the power supply module, the perimeter current stabilization controller and the jitter controller are fixed on the inner wall surface of the shell, and the DSP signal processor is installed on the mother board. The power supply module provides direct current for the work of the device; the gyroscope, the DSP signal processor, the accelerometer, the perimeter current stabilization controller and the jitter controller are connected with the mother set; the timing module is placed on the DSP signal processing board. In the operation process of the device, the jitter controller is used for eliminating the influence of mechanical jitter on the output of the gyroscope, meanwhile, the interference of some random noise can be inhibited, and the effective bandwidth of the laser gyroscope is expanded; the perimeter steady flow controller is used for enabling the light intensity output of the laser gyroscope to reach the maximum value, so that the aim of stabilizing the frequency is fulfilled.

Description

Technical Field

[0001] The invention relates to the field of navigation technology, in particular to a strapdown inertial navigation device. Background Art

[0002] A strapdown inertial navigation device has high-precision autonomous positioning and orientation navigation. It does not rely on any external information, does not radiate energy to the outside, and does not have optical or electrical contact with the outside world. It has good concealment, and the working environment is not disturbed or affected by the outside world, and is not restricted by meteorological conditions. It has the advantages of autonomy, concealment, real-time and all-weather, and can provide the carrier's accurate position coordinates, azimuth, roll angle, pitch angle, speed and mileage information in real time. It is suitable for navigation, guidance, positioning and orientation, and attitude control of various carriers.

[0003] The device is a completely autonomous positioning and orientation device. Unlike other positioning and orientation equipment such as satellite navigation, it is not susceptible to external interference. It can provide real-time and reliable guarantee for the positioning, orientation and attitude measurement of the carrier, and plays a very important role in improving the rapid response and precision strike capabilities of the troops. It can give the position coordinates of the carrier moving at high speed in real time, and provide azimuth and horizontal attitude references, so that self-propelled artillery and other weapon devices can accurately and stably aim and shoot, which can greatly improve the combat response time. Summary of the invention

[0004] In order to solve the technical problem that the existing positioning and orientation equipment in the above-mentioned prior art is easily disturbed by the outside world, so that self-propelled artillery and other weapon devices cannot aim and shoot quickly and accurately, the present invention provides a strapdown inertial navigation device.

[0005] In order to realize the above technical solution, the present invention provides a strapdown inertial navigation device, including a shell and a mounting bracket, wherein the shell is composed of a side plate and a bottom plate and a top plate fixed to the side plate by screws, and the device mounting bracket is fixed to the bottom plate by pins. It also includes a motherboard fixed on the inner wall of the shell, a power module, a circumference constant current controller, a jitter controller, and a DSP signal processor installed on the motherboard; the power module provides direct current for the device to work, and the gyroscope, the DSP signal processor, the accelerometer, the circumference constant current controller and the jitter controller are connected to the motherboard; the timing module is placed on the DSP signal processing board.

[0006] Furthermore, the DSP signal processor processes the gyro signal, accelerometer signal, and information of the odometer and altimeter transmitted from the motherboard through the FPGA chip to perform navigation solution.

[0007] Furthermore, the device mounting bracket is fixedly mounted on the carrier via a shock absorber.

[0008] Furthermore, the laser gyro bracket inside the device is fixedly mounted on the chassis via a vibration damper.

[0009] Furthermore, the shell is a heat dissipation slot structure.

[0010] In summary, the present invention has the following beneficial effects compared with the prior art:

[0011] The strapdown inertial navigation device provided by the present invention is equipped with a jitter controller and a circumference stabilizing current controller. When the device is in operation, the jitter controller is used to eliminate the influence of mechanical jitter on the gyro output, and at the same time, the interference of some random noises can be suppressed to expand the effective bandwidth of the laser gyro; the circumference stabilizing current controller is used to make the light intensity output of the laser gyro reach a maximum value, thereby achieving the purpose of frequency stabilization.

[0012] In addition, the present invention also combines a navigation method of software introduced into a DSP signal processor, which enables the strapdown inertial navigation device to achieve accurate navigation and positioning during operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0014] Figure 1 A device hardware principle block diagram of a strapdown inertial navigation device provided by the present invention;

[0015] Figure 2 This is the calculation principle block diagram of the device. DETAILED DESCRIPTION

[0016] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0017] See also Figure 1As shown, the present invention provides a strapdown inertial navigation device. Similar to the prior art, the strapdown inertial navigation device includes a housing and a mounting bracket. The housing is composed of side panels and a bottom plate and a top plate fixed to the side panels by screws. The device mounting bracket is fixed to the bottom plate by pins. Different from the prior art, it also includes a motherboard fixed to the inner wall of the housing, a power module, a circumference constant current controller, a jitter controller, and a DSP signal processor installed on the motherboard; the power module provides DC current for the device to work, and the gyroscope, DSP signal processor, accelerometer, circumference constant current controller and jitter controller are connected to the motherboard; the timing module is placed on the DSP signal processing board. The detailed functions of each part are as follows:

[0018] (1) Motherboard

[0019] It provides communication and power supply for each hardware function board.

[0020] (2) (Laser gyro and accelerometer) DSP signal processor

[0021] Preprocess the output signal of the laser gyro, convert the sine signal into a square wave pulse signal, and complete the signal acquisition. At the same time, complete the accelerometer signal acquisition, processor temperature compensation and output data.

[0022] The accelerometer signal acquisition uses TMS320F28335 as the central processor and the 18-bit high-precision four-way synchronous fast sampling AD7608 as the AD conversion chip to provide accurate input information for the navigation device.

[0023] F28335 adopts multi-bus Harvard structure and seven-level logic pipeline, which greatly speeds up the processing speed of the processor and provides fast and accurate control and processing capabilities for the acquisition of laser gyro signals and accelerometer signals. F28335 reads accelerometer data and laser gyro data in real time through FPGA, and outputs three-axis angular velocity, acceleration and temperature to navigation processor C6747 through FPGA, which realizes AD conversion control and data reading.

[0024] The SIN and COS signals output by the laser gyro are designed with FPGA chip A3P250 for phase discrimination, frequency multiplication, counting, and synchronous control. After F28335 processes the data, it transmits the accelerometer and laser gyro data through FPGA and outputs it to the navigation computer for navigation solution.

[0025] (3) Perimeter Flow Controller

[0026] The laser cavity length of the laser gyroscope must remain stable to stabilize the natural frequency of the resonant cavity. Due to the influence of temperature drift and uneven structural stiffness, the laser cavity length will change. The frequency stability of the device is achieved by designing a frequency stabilization controller.

[0027] The design of the frequency stabilization controller uses a single-chip microcomputer to control the D / A converter MAX526 to generate a 0-5V continuous voltage with a certain step size (such as 20mv); the 0-5V input voltage is amplified 40 times by the high-voltage amplifier and becomes a 0-200V continuously adjustable voltage added to the piezoelectric crystal. While the piezoelectric crystal adjusts the continuous change of the laser gyro cavity length, the single-chip microcomputer controls the 12-bit A / D converter to obtain the corresponding laser gyro output light intensity amplitude, and then compares it with the maximum light intensity output obtained by the scanning device, and then drives the control signal through the D / A to adjust the laser gyro cavity length change, so that the laser gyro light intensity output reaches the maximum value, thereby achieving the purpose of frequency stabilization.

[0028] (4) Jitter Controller

[0029] Apply jitter control to the laser gyro to overcome the locking dead zone of the laser gyro.

[0030] Since the laser gyro has a self-locking phenomenon, when the external angular velocity value does not exceed a certain threshold, the output will be zero. Therefore, the jitter offset frequency method is used to eliminate the locking effect, but at the same time, the error caused by the jitter noise will be introduced into the gyro output pulse accordingly, so the jitter demodulation method must be used to deduct the data caused by the jitter. Because the frequency of the laser gyro jitter reference signal is relatively fixed, sampling the laser gyro output at a frequency more than twice higher than it (sampling frequency of 2KHZ), and then performing corresponding digital filtering processing, will effectively eliminate the impact of mechanical jitter on the gyro output, and at the same time, it can also suppress the interference of some random noise and expand the effective bandwidth of the laser gyro.

[0031] (5) Power module

[0032] Provide DC voltage +5V, ±15V, ±65V, +200V, -1500V, +2800V for the device to operate.

[0033] (6) Time system module

[0034] The time synchronization module is installed on the DSP signal processing board. The time synchronization module receives the synchronization signal of the main system and sends it to DSP6747 at the same time. The DSP signal processor receives the synchronization signal and immediately sends the attitude information to the time synchronization module. The time synchronization module processes the information and sends it to the main system.

[0035] 1. Working principle of a strapdown inertial navigation device provided by the present invention

[0036] The strapdown inertial navigation device provided by the present invention is a strapdown navigation device, in which an inertial measurement unit (IMU) composed of a laser gyro gyroscope and an accelerometer is directly installed on a carrier, and they are respectively sensitive to the angular velocity vector of the carrier coordinate system relative to the inertial coordinate system. and the specific force vector in the carrier coordinate system The gyroscope in the device is sensitive to the angular velocity of the carrier's motion. In order to eliminate the influence of the carrier's motion on the accelerometer and gyroscope, the output of the accelerometer and gyroscope must first be compensated according to the error model to obtain a more accurate angular velocity of the carrier relative to the inertial system. Hebi The calculation principle diagram is shown in Figure 2 shown.

[0037] Since the accelerometer and gyroscope are directly connected to the carrier in the strapdown device, the dynamic error of the inertial instrument caused by the carrier movement is more important among all the errors. Figure 2 It is indicated in Figure 1 that the output signals of the gyroscope and accelerometer must be compensated for errors before navigation solution is performed. The navigation solution process is: binding initial coordinates → initial alignment solution → navigation solution.

[0038] (1) About the initial coordinates of binding

[0039] Table 1 Binding initial coordinate parameters

[0040]

[0041] From the device principle frame Figure 2 As we know, the accelerometer in the device obtains the speed and position information through integration operation. The initial position coordinates of the carrier must be bound before the device is initialized and aligned. There are three ways to bind the initial coordinates:

[0042] 1. At a location with a known standard point, select the standard point position coordinates as the initial position coordinates for binding;

[0043] 2. In the location without standard points, reliable position coordinates measured by satellite positioning equipment can be used for binding;

[0044] 3. When the standard point coordinates are not bound, the device defaults to the coordinates saved in the last navigation as the initial coordinates.

[0045] 2. About initial alignment

[0046] There is no mathematical platform after the device is started. Before the device enters the navigation work, it must be initially aligned, that is, to determine the initial conditions of the navigation solution. The main task of the initial alignment is to determine the initial direction cosine matrix C between the carrier coordinate system and the real navigation coordinate system. b nThe horizontal reference of the device's mathematical platform is determined by the navigation computer using a mathematical analytical method based on the horizontal component of the gravity acceleration sensed by the accelerometer. After the horizontal reference is determined, the position of the device's mathematical platform is analyzed based on the information of the earth's rotation angular velocity sensed by the gyroscope to complete the initial alignment of the device, that is, to obtain the initial attitude matrix C b n .

[0047] The requirements for initial alignment are mainly alignment accuracy and alignment time. The alignment accuracy is directly related to the navigation accuracy of the device, and the alignment time is directly related to the reaction time of the device. According to the basic principle of initial alignment, the horizontal alignment accuracy mainly depends on the zero offset of the accelerometer, while the azimuth alignment accuracy mainly depends on the size of the northeast gyro drift.

[0048] The initial alignment of the device is divided into two stages: coarse alignment and fine alignment.

[0049] The first stage is the coarse alignment stage. The coarse alignment stage uses the gravity vector and the earth's angular velocity as information and is performed using analytical methods. After the device has been working for 1 second, the roll and pitch attitude angles are obtained based on the accelerometer information, with an accuracy of 0.5 mil; after working for 10 seconds, the azimuth of the device is obtained based on the gyro-sensitive earth's rotation angular velocity, and the azimuth accuracy reaches 0.5 mil. At this time, the coarse alignment stage of the device is completed.

[0050] The second stage is the fine alignment stage. The fine alignment stage of the device is a continuation of the coarse alignment stage. The main task of this stage is: while making the "mathematical platform" tend to the horizontal state as much as possible, it can automatically detect the drift of the gyroscope and accurately estimate the azimuth angle, provide accurate initial conditions for navigation calculations, and achieve high-precision positioning and directional navigation. In this device, the Kalman filtering technology is added to the fine alignment stage, the error equation and measurement equation of the device are established, the attitude angle error of the device is accurately estimated, and the attitude angle of the coarse alignment stage is corrected to complete the fine alignment stage of the device and the initial alignment of the device.

[0051] The device's normal alignment north-seeking accuracy reaches 0.2 mil, and its attitude static accuracy reaches 0.2 mil. The device finally completes the initial alignment in 1 minute.

[0052] The Kalman filtering technology is added in the initial alignment of this device, which can accurately estimate the attitude error angle of the device and ensure the north-seeking accuracy of the device. At the same time, the environmental resistance of the device is greatly improved. During the initial alignment of the device, the staff can walk slightly on the vehicle and the carrier engine does not need to be turned off, and the north-seeking accuracy can still reach 0.5mil.

[0053] The initial alignment of the device can be selected as normal alignment and emergency fast alignment according to user needs. Emergency fast alignment is actually the coarse alignment stage, which directly generates the attitude matrix and enters the navigation state; normal alignment includes the coarse alignment stage and the fine alignment stage. By adding filtering technology, high-precision azimuth and attitude angles can be obtained. The attitude angle accuracy of emergency fast alignment can reach 0.2mil, and the azimuth accuracy can reach 0.5mil.

[0054] 3. About navigation solution

[0055] The device navigation solution stage mainly updates and calculates the device's attitude matrix, position matrix and speed in real time based on the initial alignment, so that the device's azimuth, attitude angle, speed, position information and other information are calculated in real time during the device update cycle and sent to the integrated management computer. Its working principle is shown in Figure 2 shown.

[0056] 1) Posture matrix update

[0057] The device measures the angular velocity of the Earth's rotation Combined position matrix Projected to the navigation coordinate system Add the displacement angular rate (Δω n (Optional) Get the angular velocity correction value in the navigation system pass Angular velocity correction value converted from matrix to carrier coordinate system Combined with the gyroscope's sensitive angular velocity information The calculation can obtain the real-time attitude update matrix.

[0058] 2) Speed ​​calculation

[0059] The device speed is given by the specific force differential equation Points are obtained. It is the specific force information in the carrier coordinate system measured by the accelerometer pass The comparative information of the navigation system obtained by conversion. It is the Coriolis acceleration, which is composed of the earth's rotation and the carrier's motion. It is a small quantity and can be ignored in the calculation. is the drag acceleration, which is caused by the movement of the carrier on the surface of the earth, g n is the gravitational acceleration vector. It is harmful acceleration and must be deducted from the accelerometer equivalent output to obtain the real-time carrier velocity.

[0060] 3) Position matrix update

[0061] The device receives odometer mileage information Combined with the pose matrix Convert the mileage information to the navigation coordinate system to obtain the mileage component in the navigation coordinate system Dividing by the time period gives the average velocity of the carrier, which is used to correct the velocity integrated by the accelerometer specific force (which spreads over time), and gives Then, by the carrier speed Divide by the radius of the Earth to get the angular velocity of displacement Position Matrix Differential equations of motion The real-time position update matrix is ​​calculated by integrating the time. Since the altitude channel is divergent in pure inertial navigation, the altitude information sensitive to the altimeter is used to update the device altitude in real time.

[0062] 4. About the barometric altimeter

[0063] In the case of little change in air pressure and temperature in a short period of time, the altitude value measured by the barometric altimeter is relatively stable, and its intermediate altitude error is less than 5m. Therefore, the relative altitude error value measured by the barometric altimeter is used to correct the altitude information of the device in real time.

[0064] 5. About odometer

[0065] The device combines the mileage information output by the odometer and uses the dead reckoning algorithm to obtain the speed and position coordinates of the carrier, and corrects the speed and position coordinates in the device in real time.

[0066] As a preferred embodiment, the DSP signal processor processes the gyro signal, accelerometer signal, and information of the odometer and altimeter transmitted from the motherboard through the FPGA chip to perform navigation solution.

[0067] As a preferred embodiment, in order to ensure that the device can work reliably under large vibration and impact, the device adopts a two-stage vibration reduction design. The first-stage vibration reduction design is that the device mounting bracket is fixedly installed on the carrier through a vibration absorber, so that the device installed on the bracket can effectively reduce vibration; the second-stage vibration reduction design is that the laser gyro bracket inside the device is fixedly installed on the chassis through a vibration absorber, which can effectively reduce the impact of vibration and impact of the inertial sensitive unit (laser gyro and accelerometer) on the accuracy of the sampling data, and improve the device's anti-vibration and anti-impact environmental adaptability.

[0068] As a preferred embodiment, the shell has a heat dissipation slot structure to facilitate heat dissipation and installation of the device.

[0069] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A strapdown inertial navigation device, comprising a housing and a mounting bracket, wherein the housing is composed of side panels and a bottom plate and a top plate fixed to the side panels by screws, and the device mounting bracket is fixed to the bottom plate by pins, characterized in that: It also includes a motherboard fixed on the inner wall of the shell, a power module, a circumference constant current controller, a jitter controller, and a DSP signal processor installed on the motherboard; the power module provides DC current for the operation of the device, the gyroscope, the DSP signal processor, the accelerometer, the circumference constant current controller and the jitter controller are connected to the motherboard; the timing module is placed on the DSP signal processing board.

2. The strapdown inertial navigation device according to claim 1, characterized in that: The DSP signal processor processes the gyro signal, accelerometer signal, and information of the odometer and altimeter transmitted from the motherboard through the FPGA chip to perform navigation solution.

3. The strapdown inertial navigation device according to claim 1, characterized in that: The device mounting bracket is fixedly mounted on the carrier via a vibration damper.

4. The strapdown inertial navigation device according to claim 1, characterized in that: The laser gyro bracket inside the device is fixed on the chassis through a vibration damper.

5. The strapdown inertial navigation device according to any one of claims 1 to 4, characterized in that: The shell is a heat dissipation slot structure.

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