Frequency correction self-adaption method for different environment temperature transfer characteristics of strapdown inertial measurement unit

Abstract

A frequency correction self-adaption method for different environment temperature transfer characteristics of a strapdown inertial measurement unit comprises the steps that the inertial measurement unit sets a filter coefficient for a first path of frequency correction filter according to the temperature of a gyroscope; the first path of frequency correction filter is used for filtering a pulse signal output by the inertial measurement unit; setting a filter coefficient for a second frequency correction filter according to the coefficient of the first frequency correction filter and the current gyroscope temperature; the second path of frequency correction filter is used for filtering a pulse signal output by the inertial measurement unit; the inertial measurement unit receives a flight instruction of the control system, judges whether coefficients of the two paths of frequency correction filters are the same after receiving the instruction, and outputs first path of filtering data and sets a flight sign of the inertial measurement unit if the coefficients are the same; and if not, outputting the second path of filtering data and setting a flight sign of the inertial measurement unit. The problem of frequency correction filtering difference of the inertial measurement unit facing different working conditions is solved, the self-adaption function is achieved, and the requirement of the inertial measurement unit for the transfer characteristic under the wide temperature range can be met.

Description

Technical Field

[0001] The present invention belongs to the field of inertial assembly design, and relates to a method for frequency correction and self - adaptation of the transfer characteristics of a strap - down inertial assembly at different ambient temperatures. Background Technique

[0002] A strap - down inertial assembly is a precision instrument used to measure the attitude, velocity, and position of a carrier. The strap - down inertial assembly consists of an inertial sensitive component, a indexing and locking mechanism, a power circuit, an information processing and control circuit, etc. The inertial sensitive component is mainly composed of a gyroscope, an accelerometer, and related circuits, and realizes the function of measuring the apparent velocity increment and angle increment in three directions of the carrier in real time.

[0003] In order to improve the mechanical environment adaptability of the strap - down inertial assembly, damping and vibration reduction measures are usually taken between the inertial assembly and the installation base. While the shock absorber plays the role of vibration isolation and damping, it also makes the motion parameters sensed by the sensitive elements change. By conducting an angular vibration test on the inertial assembly shock absorber system, the angular vibration transfer characteristics of the inertial assembly obtained are important parameters to ensure the design stability of the attitude control system.

[0004] The inertial assembly transfer characteristic test examines the angular vibration transfer characteristics in three directions of the inertial assembly small system (including mechanical links such as the inertial assembly girder, inertial assembly housing, and shock absorber, as well as the filter circuit link) in angular vibration and linear vibration environments, providing a design basis for the attitude control specialty.

[0005] The strap - down inertial assembly is connected to the body and the box or frame through a shock absorber. The peak - to - peak points excited during linear and angular vibration of the inertial assembly are mainly the peak frequency points of the body shock absorber and the frame. The working conditions of most models are good, and the ambient temperature is around normal temperature. Therefore, most inertial assembly frequency correction filters have only one. Currently, the requirements for the environmental adaptability of inertial assemblies are getting higher and higher, and there is a clear demand for cold start of inertial assemblies at ultra - low temperature (-40°C). At different ambient temperatures, the shock absorber and the frame structure will expand and contract thermally, making the linear and angular vibration transfer characteristics in each direction under angular vibration and linear vibration environments different. A single frequency correction filter is difficult to meet the frequency characteristics of the inertial assembly from low temperature to high temperature. Currently, there is little attention and research on the transfer characteristics of inertial assemblies at ultra - low temperature (-40°C) in China. However, through experimental comparison, it is found that due to the differences between each inertial assembly, it is difficult for one filter to cover the transfer characteristics of different inertial assemblies from low temperature to high temperature. If a single filter is forced to be used, it will cause an increase in the phase delay of the inertial assembly and an increase in the frequency amplification factor, resulting in a loss of accuracy and making it difficult for the attitude control system to control. Summary of the Invention

[0006] The technical problem solved by the present invention is: overcoming the deficiencies of the prior art, proposing a method for frequency correction and self - adaptation of the transfer characteristics of a strap - down inertial unit at different ambient temperatures, solving the problem of frequency correction filtering differences of the inertial unit under different working conditions, and realizing the self - adaptation function, which can meet the requirements of the inertial unit for transfer characteristics under wide temperature conditions.

[0007] The technical solution adopted by the present invention is:

[0008] A method for frequency correction and self - adaptation of the transfer characteristics of a strap - down inertial unit at different ambient temperatures, including:

[0009] The inertial unit sets filter coefficients for the first - path frequency correction filter according to the current temperature of the gyroscope; the first - path frequency correction filter coefficients include three types: filter coefficients applicable to (-40 °C, -15 °C), filter coefficients applicable to [-15 °C, 25 °C], and filter coefficients applicable to (25 °C, 50 °C);

[0010] The first - path frequency correction filter filters the pulse signal output by the inertial unit and outputs the first - path filtered data;

[0011] The inertial unit sets filter coefficients for the second - path frequency correction filter in real - time according to the current temperature of the gyroscope; the second - path frequency correction filter coefficients include three types: filter coefficients applicable to (-40.5 °C, -14.5 °C), filter coefficients applicable to [-14.5 °C, 25.5 °C], and filter coefficients applicable to (25.5 °C, 50.5 °C);

[0012] The second - path frequency correction filter filters the pulse signal output by the inertial unit and outputs the second - path filtered data;

[0013] The inertial unit receives the flight instruction of the control system. After receiving the instruction, it judges whether the coefficients of the first - path frequency correction filter are the same as those of the second - path frequency correction filter. If they are the same, it outputs the first - path filtered data and sets the inertial unit's flight flag; if they are different, it outputs the second - path filtered data and sets the inertial unit's flight flag.

[0014] Preferably, within 3 s after the inertial unit is powered on, it is in a state without a filter. After 3 s, it sets filter coefficients for the first - path frequency correction filter according to the current temperature of the gyroscope.

[0015] Preferably, the inertial unit identifies the temperature of the gyroscope through a temperature sensor installed on the gyroscope.

[0016] Preferably, the temperatures of the three gyroscopes on the inertial unit are mutually redundant.

[0017] Preferably, the second path frequency correction filter coefficients are the same set of coefficients as the first path frequency correction filter coefficients, that is, the second path frequency correction filter coefficients applicable to (-40.5°C, -14.5°C) are the same as the first path frequency correction filter coefficients applicable to (-40°C, -15°C), the second path frequency correction filter coefficients applicable to [-14.5°C, 25.5°C] are the same as the first path frequency correction filter coefficients applicable to [-15°C, 25°C], and the second path frequency correction filter coefficients applicable to (25.5°C, 50.5°C) are the same as the first path frequency correction filter coefficients applicable to (25°C, 50°C).

[0018] Preferably, the first path frequency correction filter coefficients are obtained by the following method:

[0019] For the inertial measurement unit (IMU) within the temperature range of -40°C to 50°C, angular vibration frequency characteristic tests are carried out at each temperature point with an interval of 10°C. The frequency characteristics from the installation location of the IMU body to the output of the IMU are obtained at each temperature point, and then the transfer characteristics of the full temperature range from low temperature to high temperature of the IMU are obtained. Based on this, the frequency correction filter coefficients for three temperature segments (-40°C, -15°C), [-15°C, 25°C], and (25°C, 50°C) are generated.

[0020] Preferably, the frequency correction filter coefficients are all stored in the flash sector of the computer board, and the IMU calls them by accessing their storage locations.

[0021] The beneficial effects of the present invention compared with the prior art are as follows:

[0022] (1) The present invention adopts a multi-point redundant temperature setting to avoid functional failure caused by damage to the temperature measurement sensor; through a large amount of experimental data accumulation, analysis of laws, and reasonable segmentation, the calculation amount is reduced while ensuring effectiveness.

[0023] (2) The present invention automatically selects the frequency correction filter according to the temperature to ensure the normal operation of the IMU within the full temperature range, and solves the problems of increased phase delay, increased frequency magnification factor, and loss of accuracy of the IMU caused by a traditional single frequency correction filter.

[0024] (3) The present invention adopts a two-wire parallel method to send the status word in real time to monitor the filter status, avoiding jumps and abnormalities during the switching process, which may affect the attitude control system. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a flowchart of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0026] The present invention will be further described below with reference to the drawings.

[0027] A method for frequency correction and adaptation of the transfer characteristics of a strapdown inertial unit under different ambient temperatures, which mainly identifies the temperature when the inertial unit is powered on through the internal temperature sensor of the inertial unit, automatically selects a suitable filter, and adopts a two-line parallel method to complete the connection of the switch, so as to meet the working conditions of the inertial unit under different ambient temperatures.

[0028] The inertial unit uses the temperature output by the temperature sensor on the gyroscope as the standard for selecting the frequency correction filter, and the temperatures of the three gyroscopes are redundant with each other.

[0029] As Figure 1 shown, the implementation steps of the present invention are as follows:

[0030] 1. Within 3 s after the inertial unit is powered on, it is in a state without a filter. After 3 s, the first-path frequency correction filter coefficient at the current temperature is selected according to the gyroscope temperature; the first-path frequency correction filter coefficient includes three types: filter coefficients applicable to (-40°C, -15°C), filter coefficients applicable to [-15°C, 25°C], and filter coefficients applicable to above (25°C, 50°C).

[0031] 2. After selecting the filter coefficient, the first-path frequency correction filter filters the pulse signal output by the inertial unit and outputs the first-path filtered data.

[0032] 3. The inertial unit sets the filter coefficient for the second-path frequency correction filter in real time according to the current gyroscope temperature; the second-path frequency correction filter coefficient is the same as that used by the first-path frequency correction filter, and the temperature value range is changed to (-40.5°C, -14.5°C), [-14.5°C, 25.5°C], (25.5°C, 50.5°C);.

[0033] 4. The second-path frequency correction filter filters the pulse signal output by the inertial unit and outputs the second-path filtered data.

[0034] 5. The inertial unit receives the flight instruction of the control system. After receiving the instruction, it judges whether the coefficients of the first-path frequency correction filter are the same as those of the second-path frequency correction filter. If they are the same, it outputs the first-path filtered data and sets the inertial unit's flight flag; if they are different, it outputs the second-path filtered data and sets the inertial unit's flight flag.

[0035] The first-path frequency correction filter coefficient is obtained through the following method:

[0036] The inertial measurement unit (IMU) is subjected to an angular vibration frequency characteristic test at each temperature point of every 10°C within the temperature range of -40°C to 50°C to obtain the frequency characteristics from the installation location of the IMU body to the IMU output at each temperature point, and then the full-temperature transfer characteristics of the IMU from low temperature to high temperature are obtained. Based on this, the frequency correction filter coefficients for three temperature segments of (-40°C, -15°C), [-15°C, 25°C], and (25°C, 50°C) are generated.

[0037] The coefficients selected for the second frequency correction filter are the same set of coefficients as those selected for the first frequency correction filter, only the temperature value ranges are different. The difference is that the temperature value ranges of the three segments of coefficients of the first frequency correction filter, which are (-40°C, -15°C), [-15°C, 25°C], and (25°C, 50°C), are changed to (-40.5°C, -14.5°C), [-14.5°C, 25.5°C], and (25.5°C, 50.5°C).

[0038] The three segments of coefficients are simultaneously stored in the flash sector of the computer board and are called accordingly based on their different storage locations.

[0039] When the IMU is powered on, the appropriate filter coefficients are automatically selected according to the temperature measured by the internal temperature sensor, and the switching connection is completed in a dual-line parallel manner to meet the working conditions of the IMU at different ambient temperatures.

[0040] The parts not detailed in the present invention belong to the common general knowledge of those skilled in the art.

Claims

1. A method for self-adapting frequency correction of strapdown inertial system transfer characteristics under different ambient temperatures, characterized in that: include: The inertial group sets a filter coefficient for the first frequency correction filter according to the current gyroscope temperature; the first frequency correction filter coefficient includes three types: a filter coefficient applicable to (-40°C, -15°C), a filter coefficient applicable to [-15°C, 25°C], and a filter coefficient applicable to (25°C, 50°C); The first frequency correction filter filters the pulse signal output by the inertial group and outputs the first filtering data; The inertial group sets the filter coefficient for the second frequency correction filter in real time according to the current gyroscope temperature; the second frequency correction filter coefficient includes three types: filter coefficient applicable to (-40.5℃, -14.5℃), filter coefficient applicable to [-14.5℃, 25.5℃], and filter coefficient applicable to (25.5℃, 50.5℃); The second frequency correction filter filters the pulse signal output by the inertial group and outputs the second filtering data; The inertial group receives the flight command from the control system. After receiving the command, it determines whether the coefficients of the first frequency correction filter are the same as the coefficients of the second frequency correction filter. If they are the same, the first filter data is output and the inertial group has flown flag is set; if they are not the same, the second filter data is output and the inertial group has flown flag is set.

2. The method for frequency correction and self-adaptation of the transfer characteristics of a strapdown inertial system under different ambient temperatures according to claim 1, characterized in that: The inertial group is in the no-filter state within 3 seconds after power-on. After 3 seconds, the filter coefficient is set for the first frequency correction filter according to the current gyroscope temperature.

3. The method for frequency correction and self-adaptation of the transfer characteristics of a strapdown inertial system under different ambient temperatures according to claim 1, characterized in that: The IMU identifies the gyro temperature through the temperature sensor installed on the gyro.

4. The method for frequency correction and self-adaptation of the transfer characteristics of a strapdown inertial system under different ambient temperatures according to claim 1, characterized in that: The temperatures of the three gyroscopes on the inertial group are redundant.

5. The method for frequency correction and self-adaptation of the transfer characteristics of a strapdown inertial system under different ambient temperatures according to claim 1, characterized in that: The second frequency correction filter coefficients are the same set of coefficients as the first frequency correction filter coefficients, that is, the second frequency correction filter coefficients applicable to (-40.5℃, -14.5℃) are the same as the first frequency correction filter coefficients applicable to (-40℃, -15℃), the second frequency correction filter coefficients applicable to [-14.5℃, 25.5℃] are the same as the first frequency correction filter coefficients applicable to [-15℃, 25℃], and the second frequency correction filter coefficients applicable to (25.5℃, 50.5℃) are the same as the first frequency correction filter coefficients applicable to (25℃, 50℃).

6. The method for frequency correction and self-adaptation of the transfer characteristics of a strapdown inertial system under different ambient temperatures according to claim 1, characterized in that: The first frequency correction filter coefficients are obtained by the following method: The angular vibration frequency characteristic test of the inertial group was carried out at a temperature point of 10°C within the temperature range of -40°C to 50°C, and the frequency characteristics between the inertial group body installation point and the inertial group output at each temperature point were obtained, and then the full-temperature transfer characteristics of the inertial group from low temperature to high temperature were obtained, and the frequency correction filter coefficients of the three temperature sections of (-40°C, -15°C), [-15°C, 25°C], and (25°C, 50°C) were generated accordingly.

7. The method for frequency correction and self-adaptation of the transfer characteristics of a strapdown inertial unit under different ambient temperatures according to claim 1, characterized in that: The frequency correction filter coefficients are stored in the flash sector of the computer board and are called by the inertial group by accessing their storage locations.

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