Roll angle acquisition method for roll projectile in uncontrolled flight phase based on angular rate information

Abstract

The application discloses a method for obtaining the roll angle of a rolling projectile in a non-controlled section based on angular rate information, which processes the pitch angular rate data measured by a radial gyroscope to obtain an initial projectile roll angle, and then obtains the roll angle of the projectile at other time according to the roll angular rate measured by the radial gyroscope. The method for obtaining the roll angle of the rolling projectile in the non-controlled section based on the angular rate information does not need to install elements such as a geomagnetic sensor, solves the high dynamic roll angle alignment problem by using less information, is adaptable to the high dynamic of the roll channel, and can provide a good initial condition for the combined navigation of the rolling projectile.

Description

TECHNICAL FIELD

[0001] The application relates to a method for controlling the beam of a phased array radar seeker of a rolling aircraft, and belongs to the field of aircraft control. BACKGROUND

[0002] A rolling projectile is a kind of special projectile, which periodically rolls around its own longitudinal axis during flight. The rolling projectile can reduce the influence of external interference, aerodynamic structure asymmetry and mass eccentricity, plays a gyroscopic stabilizing effect on a static unstable projectile, and has many advantages and is widely used.

[0003] A laser terminal guided projectile is a kind of most widely used precision strike weapon. The terminal guided weapon has a significantly increased point spread with the increase of the range, which brings difficulties to the terminal guided handover. Therefore, high-precision navigation must be realized to correct the trajectory in the middle flight.

[0004] The trajectory correction requires initial attitude alignment. The terminal guided projectile usually bears a large load before being launched, and the interior ballistic rolling channel presents a high dynamic motion with a rotation speed of thousands of revolutions per second. The inertial navigation system cannot work in advance, and the initial attitude cannot be obtained by using initial alignment at the time of launching. It is necessary to use inertial gyroscopes, accelerometers, satellite navigation data or geomagnetic information on the projectile for alignment after launching. The rolling projectile has a high rotation speed, a slow alignment speed of the rolling angle in the air, and is difficult to accurately align, which leads to a slow speed of obtaining the initial attitude and reduces the hitting accuracy.

[0005] Therefore, it is necessary to study a rolling angle initial value obtaining method for a rolling projectile, which can solve the above technical problems. SUMMARY

[0006] In order to overcome the above problems, the present application has been designed based on the in-depth research of the present application, and a rolling angle obtaining method for a rolling projectile in a non-controlled section based on angular rate information is designed. The pitch angular rate data measured by a radial gyroscope is processed to obtain the initial rolling angle of the projectile body, and then the rolling angles of the projectile body at different times are obtained according to the rolling angular rate measured by an axial gyroscope.

[0007] In a preferred embodiment, the method comprises the following steps:

[0008] S1, preprocessing original inertial gyroscope data to obtain accurate radial angular rate gyroscope data;

[0009] S3, obtaining a rolling angle initial value according to the accurate radial angular rate gyroscope data;

[0010] S4, obtaining the rolling angles at different times according to the rolling angle initial value and the rolling angular rate.

[0011] In a preferred embodiment, in S3, the rolling angle initial value is obtained by the following formula:

[0012]

[0013]

[0014]

[0015] wherein ω by , ω bz represent the pre-processed accurate radial gyro data, Δγ represents the roll angle that the projectile has passed after a period of time relative to the initial projectile body, which can be directly detected by the radial gyro; θ y represents the projection of the trajectory inclination angle change amount in a period of time on the Y-axis of the initial projectile body, θ z represents the projection of the trajectory inclination angle change amount in a period of time on the Z-axis of the initial projectile body, γ0 represents the roll angle at the initial time of the integral interval, and t represents a period of time.

[0016] In a preferred embodiment, in S1, the inertial gyro in a period of time is sampled to obtain the original radial gyro data, and the original radial gyro data is band-pass filtered to eliminate the components caused by the characteristic frequency ω c of the projectile body and the low-frequency components caused by the installation error.

[0017] In a preferred embodiment, the band-pass filtering is realized by a fast Fourier transform method.

[0018] In a preferred embodiment, in S4, the roll angular rate is obtained by integrating the axial gyro data in a period of time.

[0019] In a preferred embodiment, the period of time is divided into multiple intervals, and the roll angle Δγ(kT) passed from the initial time to the kth integral interval is represented as:

[0020]

[0021] k represents the kth integral interval, i ∈ [1, k], T is the gyro sampling period, ω x represents the measured roll angular rate.

[0022] In a preferred embodiment,

[0023] γ 主 represents the roll angle value obtained by the arctangent function.

[0024] In a preferred embodiment, before S3, there is also a step S2, radial gyro data validity confirmation, to determine whether the inertial gyro measurement value is abnormal.

[0025] According to the application, only the data of the inertial gyroscope is used without the data of the geomagnetic sensor.

[0026] The application has the following beneficial effects:

[0027] (1) Without installing elements such as geomagnetic sensors, the high dynamic roll angle alignment problem is solved by using less information;

[0028] (2) The high dynamic of the roll channel can be adapted, and the uncertainty caused by the high dynamic is reduced through the integration process;

[0029] (3) Good initial conditions can be provided for the roll missile combined navigation. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 A flowchart of a roll angle acquisition method for a roll missile in a free flight stage based on angular rate information according to a preferred embodiment of the application is shown;

[0031] Figure 2 A diagram showing the data spectrum of a radial gyroscope for a roll missile in a free flight stage is shown;

[0032] Figure 3 A diagram showing the definition of the coordinate system according to the application is shown;

[0033] Figure 4 Data measured by a gyroscope during flight in Example 1 of the application is shown;

[0034] Figure 5 The comparison between the roll angle obtained in Example 1 of the application and the theoretical value is shown. DETAILED DESCRIPTION

[0035] The application will be further described in detail below with reference to the accompanying drawings and examples. The features and advantages of the application will become more apparent through these descriptions.

[0036] The term "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any implementation described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other implementations. Unless specifically stated otherwise, the drawings are not drawn to scale and are merely intended to show the relative positions of the various elements.

[0037] It should be noted that in the application, for the convenience of description, the body coordinate system is defined as follows: the body coordinate system has its origin at the body center of mass, the X-axis is along the body axis, the forward direction is positive; the Y-axis is in the body longitudinal symmetry plane, perpendicular to the X-axis, and the upward direction is positive; and the Z-axis forms a right-handed coordinate system with the X and Y axes.

[0038] The application provides a roll angle acquisition method for a rolling projectile in a free flight stage based on angular velocity information.

[0039] The inertial gyroscope is a three-axis gyroscope, including a radial gyroscope and an axial gyroscope.

[0040] The inventor finds that, in the free flight stage, under the action of the static stability moment of the projectile body, the attack angle and the sideslip angle of the rolling projectile are both kept as zero, that is, the lateral motion of the rolling projectile can be ignored, and the pitch angle rate is only related to the trajectory inclination angle and the flight speed, and in a short time, the trajectory inclination angle and the speed change are both small, so the roll angle can be acquired by using the information of the inertial gyroscope.

[0041]

[0042] ω z 、ω y The projection of the rotation angle rate of the projectile body coordinate system on the z and y axes of the projectile body represents the rotation angle rate of the projectile body, and gamma represents the roll angle, The pitch angle rate of the projectile body represents the pitch angle rate of the projectile body.

[0043] According to the principle of the vertical plane trajectory bending caused by the gravity vector in the free flight stage, the pitch angle rate data measured by the radial gyroscope are processed to obtain the initial roll angle of the projectile body, and then the roll angles of the projectile body at other time points are obtained according to the roll angle rate measured by the axial gyroscope.

[0044] According to the application, as shown in Figure 1 、 2 The method comprises the following steps:

[0045] S1, preprocessing the original inertial gyroscope data to obtain accurate radial angular velocity gyroscope data;

[0046] S3, obtaining the initial roll angle according to the accurate radial angular rate gyroscope data;

[0047] S4, obtaining the roll angles at different time points according to the initial roll angle and the roll angle rate.

[0048] Since the inertial gyroscope has various errors in a high dynamic environment, including installation error angle, zero offset error, etc., the radial gyroscope will have a certain degree of axial gyroscope information; and the gyroscope can be affected by the environment to have random noise, so the angular rate information directly acquired by the inertial gyroscope is not accurate.

[0049] In the present application, the core is how to process the information detected by the original inertial gyro, so as to obtain accurate information reflecting the trajectory bending angular rate. In S1, the accurate radial angular rate gyro data is obtained by preprocessing the inertial gyro data, that is, more accurate angular rate information than the angular rate information directly detected by the inertial gyro is obtained.

[0050] The inventor found that the angular velocity information has a periodic change during the rolling of the rolling projectile, and the rolling projectile has a unique frequency spectrum characteristic which can reflect the angular rate gyro information. In the present application, the frequency spectrum characteristic is referred to as the projectile characteristic frequency ω c .

[0051] According to the present application, the inertial gyro is sampled for a period of time to obtain original radial gyro data. The original radial gyro data is band-pass filtered to obtain filtered radial gyro data, so as to eliminate the component brought by the projectile characteristic frequency ω c and the low-frequency component brought by the installation error.

[0052] In a preferred embodiment, the band-pass filtering is realized by a fast Fourier transform method.

[0053] The fast Fourier transform method is a general term for efficient and fast calculation methods for calculating discrete Fourier transform (DFT) by computer, which is abbreviated as FFT. The fast Fourier transform was proposed by J. W. Cooley and T. W. Tukey in 1965. The multiplication number required for the computer to calculate the discrete Fourier transform is greatly reduced by using this algorithm. Especially, the more the number of sampling points N is, the more significant the saving of the calculation amount of the FFT algorithm is. In the present application, the specific calculation method of FFT is not described in detail.

[0054] According to the preferred embodiment of the present application, the inertial gyro is sampled for a period of time to obtain original radial gyro data. The values obtained by sampling are processed by a fast Fourier transform to obtain the frequency spectrum characteristic of the original radial gyro data. Figure 2 A frequency spectrum diagram of a certain type of rolling projectile during the uncontrolled flight is shown.

[0055] The radial angular rate gyro data contains two components in addition to the rolling frequency component, which are the components brought by the projectile characteristic frequency, denoted as ω c1 and ω c2 The components have the following relationship with the projectile rolling frequency:

[0056]

[0057] In the formula, ω represents the projectile rolling frequency, ω c represents the projectile characteristic frequency, and ω c1 , ω c2This represents the component reflected in the radial angular rate gyroscope data; it is a useless component and needs to be eliminated later.

[0058] According to the present invention, by filtering and eliminating the above two components, the filtered gyroscope data contains only the component related to the roll frequency.

[0059] Furthermore, the projectile roll frequency ω is obtained by sampling the axial gyroscope measurement value.

[0060] In S3, such as Figure 3 As shown, YOZ represents the quasi-load system, y b0 oz b0 Represents the initial coordinate system of the projectile, y b oz b The initial roll angle, representing the current coordinate system of the carrier, is obtained using the following formula:

[0061]

[0062] Where, ω by ω bz The Y-axis and Z-axis components represent the pre-processed, precise radial gyroscope data; Δγ represents the roll angle of the projectile relative to the initial projectile after a certain period of time, which can be directly detected by the axial gyroscope; θ y θ represents the projection of the change in trajectory angle over a period of time onto the initial Y-axis of the projectile system. z The projection of the change in trajectory tilt angle over a period of time onto the Z-axis of the initial projectile system, γ0 represents the roll angle at the initial moment of the integration interval, and t represents a period of time; the period of time refers to the time between the initial moment and the moment when the radial gyroscope value is acquired.

[0063] In S4, the roll rate is obtained by integrating the axial gyroscope measurement.

[0064] Because rolling projectiles have high dynamic characteristics, it is difficult to obtain accurate values ​​for radial gyroscope measurements at every moment when the projectile is rolling rapidly. The inventors discovered that by integrating radial gyroscope data over a period of time and combining it with the initial value of the roll angle, the roll angle at each subsequent moment can be calculated. Furthermore, since the radial gyroscope signal is a periodic signal, the above process can also reduce the influence of gyroscope zero bias.

[0065] Furthermore, during the integration process, a time interval can be expressed as:

[0066] t = N*T (IV)

[0067] Where T is the gyroscope sampling period and the total number of sampling points is N.

[0068] According to projectile kinematics, the roll rate may be expressed as:

[0069]

[0070] wherein ω x represents the projection of the rotation rate of the body coordinate system on the X-axis of the body system, ω y represents the projection of the rotation rate of the body coordinate system on the Y-axis of the body system, ω z represents the projection of the rotation rate of the body coordinate system on the Z-axis of the body system, and θ represents the pitch angle of the body.

[0071] The inventor found that due to the characteristics of the rolling projectile, the roll rate of the body is large, and the pitch angle and the radial rate can be ignored relative to the axial rate, and the roll rate can be expressed as:

[0072]

[0073] Therefore, the roll angle from the initial time to the kth integration interval can be expressed as:

[0074]

[0075] wherein k represents the kth integration interval, and i∈[1, k].

[0076] According to equation (seven) and equation (three), the projection of the trajectory inclination change amount in a period of time on the initial body Y-axis θ y may be expressed as:

[0077]

[0078] wherein ω by (kT) represents the radial gyro sampling value at kT, N represents the total number of integration intervals, and NT represents the total time from the initial time to the last sampling time.

[0079] According to equation (seven) and equation (three), the projection of the trajectory inclination change amount in a period of time on the initial body Z-axis θ z may be expressed as:

[0080]

[0081] wherein ω by (kT) represents the radial gyro sampling value at kT, N represents the total number of integration intervals, and NT represents the total time from the initial time to the last sampling time.

[0082] According to θ y , θ z , the roll angle value at NT can be obtained:

[0083]

[0084] γ 主 The roll angle value obtained by the inverse tangent function.

[0085] Further, since the value range of the roll angle is γ∈[-180°,180°], the quadrant judgment of the roll angle γ needs to be made through the signs of θ y , θ z , and the final value of the roll angle γ is determined.

[0086] Specifically, when θ y >0 and θ z >0, γ=γ 主 -pi;

[0087] When θ y <0 and θ z <0, γ=γ 主 ;

[0088] When θ y <0 and θ z >0, γ=γ 主 +pi;

[0089] When θ y >0 and θ z <0, γ=γ 主 ;

[0090] Wherein, pi represents π, i.e. 180°.

[0091] In a preferred embodiment, after S1 and before S3, there is also a step S2, radial gyro data validity confirmation.

[0092] The inventor found that the roll angle rate expectation of the roll projectile is proportional to the projectile flight speed, and the projectile rotation speed is subject to a normal distribution with the roll angle rate expectation as the standard deviation:

[0093]

[0094] Wherein, ω represents the roll angle rate, μ represents the roll angle rate expectation, and σ represents the standard deviation.

[0095] The roll angle detected by the inertial gyro is obtained by the following formula:

[0096]

[0097] The spectrum characteristics of the radial gyro data obtained in step S1 can be used to obtain the corresponding roll angle γ spectrum, and then the roll angle is derived to obtain the roll angle rate frequency measured by the inertial gyro. If the actually measured roll angle rate belongs to the range of 95% confidence interval, it is considered that the roll angle rate is effective, and the initial value of the roll angle can be obtained according to the method in S3, otherwise it is considered that the inertial gyro is abnormal, the measurement result is inaccurate, and the roll angle cannot be obtained by the detection value of the inertial gyro.

[0098] Further preferably, the inventors have also found that the ballistic inclination angle rate Subject to the theoretical value As expected, σ θ is a normal distribution with a standard deviation:

[0099]

[0100] ω y is the ballistic inclination angle rate measured by the inertial gyro According to the spectrum characteristics of the radial gyro data obtained in S1, when the amplitude of ω y belongs to the range of 95% confidence interval, it is considered that the radial gyro measurement value is accurate, and the initial value of the roll angle can be obtained according to the method in S3, otherwise it is considered that the inertial gyro is abnormal, the measurement result is inaccurate, and the roll angle cannot be obtained by the detection value of the inertial gyro.

[0101] Embodiment

[0102] Embodiment 1

[0103] The black box data of a certain flight test is used to obtain the roll angle, and the data measured by the gyro during the flight is stored in the black box, as shown in FIG. Figure 4 Due to the large measurement error of the gyro, the accuracy of the roll angle obtained directly from the gyro measurement value is very low and cannot be used.

[0104] The inertial gyro is unlocked at the highest point of the trajectory, and the angle between the gyro axis and the body axis before unlocking is 0°. When the body pitch angle is less than -5°, the outer frame potentiometric sensor of the space orientation gyro will output a 5° piece signal, representing the time when the roll angle is 0°. Since the time when the roll angle is 0° is easy to obtain under this condition, by comparing the theoretical time when the roll angle is 0° with the 0° roll angle time obtained by the acquisition method, the effect of the acquisition method can be verified. In this embodiment, the theoretical data of the time of 28-34s satisfying the above condition is compared with the obtained roll angle data.

[0105] Specifically, the data measured by the gyro is processed in the following way:

[0106] S1, pre-process the original inertial gyro data to obtain accurate radial angular velocity gyro data;

[0107] S3, obtaining a roll angle initial value according to the accurate radial angular rate gyroscope data;

[0108] S4, obtaining the roll angle at different times according to the roll angle initial value and the roll angle rate.

[0109] In S1, the original radial gyroscope data is band-pass filtered by a fast Fourier transform method to obtain accurate radial gyroscope data, and the result is shown in Figure 5

[0110] In S3, for the accurate radial angular rate gyroscope data, the roll angle initial value is obtained according to the following formula:

[0111]

[0112]

[0113]

[0114] In S4, after obtaining the roll angle initial value, the roll angle at each subsequent time is calculated using the radial gyroscope measurement value.

[0115] Specifically, the change amount of the trajectory inclination angle in a period of time in the projection θ y on the initial projectile system Y axis can be represented as:

[0116]

[0117] The change amount of the trajectory inclination angle in the projection θ z on the initial projectile system Z axis can be represented as:

[0118]

[0119]

[0120] When θ y > 0 and θ z > 0, γ0= γ 主 -pi;

[0121] When θ y < 0 and θ z < 0, γ0= γ 主 ;

[0122] When θ y < 0 and θ z > 0, γ0= γ 主 +pi;

[0123] When θ y > 0 and θ z < 0, γ0= γ​主 ;

[0124] The obtained roll angle at 0° time is compared with the theoretical data roll angle at 0° time, and the results are shown in Table 1. Further, in order to clearly define the specific angle error, the roll angle rate is used to convert the time error into the angle error, as shown in Table 1.

[0125] Table 1

[0126] Time error s Angle error ° 0.000225 0.426375 -2.5E-05 -0.04737 -0.00156 -2.96567 -0.00036 -0.69167 0.000265 0.502175 -0.00037 -0.70115 -3.5E-05 -0.06632 0.000605 1.146475 0.000655 1.241225 0.0014 2.653

[0127] As can be seen from Table 1, the method can obtain relatively accurate roll angle, and the roll angle deviation is within 3°.

[0128] Figure 5 The comparison between the obtained roll angle and the theoretical value is shown, the horizontal coordinate represents the time period of processing the flight test data, the vertical coordinate represents the roll angle, the solid line represents the roll angle calculated by the roll angle recognition algorithm, and the dotted line represents the roll angle theoretical value. As can be seen from the figure, the roll angle obtained by the embodiment has small error and high accuracy compared with the theoretical value.

[0129] In the description of the present application, it should be noted that the terms "upper", "lower", "inner", "outer", "front", "back" and the like indicate the orientation or positional relationship based on the working state of the present application, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second", "third", "fourth" are only for the purpose of description, and cannot be understood as indicating or implying relative importance.

[0130] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connecting" should be understood in a broad sense, for example, it can be fixed connection, or detachable connection, or integral connection; it can be mechanical connection, or electrical connection; it can be direct connection, or indirect connection through intermediate medium; it can be the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0131] The above describes the present application in combination with the preferred embodiments, but these embodiments are only exemplary and serve only to illustrate. On this basis, various substitutions and improvements can be made to the present application, which all fall within the scope of protection of the present application.

Claims

1. A method for obtaining the uncontrolled roll angle of a rolling spring based on angular rate information, characterized in that, Using only data from inertial gyroscopes, without the need for geomagnetic sensor data, The method includes the following steps: S1. Preprocess the raw inertial gyroscope data to obtain accurate radial angular velocity gyroscope data; S3. Obtain the initial value of the roll angle based on the precise radial angular rate gyroscope data; S4. Obtain the roll angle at different times based on the initial roll angle value and roll angle rate; In S1, the inertial gyroscope is sampled over a period of time to obtain raw radial gyroscope data. The raw radial gyroscope data is then bandpass filtered to eliminate the projectile's characteristic frequency ω. c The components introduced and the low-frequency components caused by installation errors; In S3, the initial roll angle is obtained using the following formula: Where, ω by ω bz This represents the pre-processed, precise radial gyroscope data; Δγ represents the roll angle that the projectile has undergone relative to the initial projectile after a certain period of time, which can be directly detected by the radial gyroscope; θ y θ represents the projection of the change in trajectory angle over a period of time onto the initial Y-axis of the projectile system. z The projection of the change in trajectory tilt angle over a period of time onto the Z-axis of the initial projectile system, γ0 represents the roll angle at the initial moment of the integration interval, and t represents a period of time; the period of time refers to the time between the initial moment and the moment when the radial gyroscope value is acquired.

2. The method for obtaining the uncontrolled roll angle of a rolling spring based on angular rate information according to claim 1, characterized in that, The bandpass filtering is implemented using the Fast Fourier Transform method.

3. The method for obtaining the uncontrolled roll angle of a rolling spring based on angular rate information according to claim 1, characterized in that, In S4, the roll rate is obtained by integrating the axial gyroscope data over a period of time.

4. The method for obtaining the uncontrolled roll angle of a rolling spring based on angular rate information according to claim 3, characterized in that, Dividing a time period into multiple intervals, the roll angle Δγ(kT) from the initial time to the kth integration interval is expressed as: k represents the k-th integration interval, i∈[1,k], T is the gyroscope sampling period, ω x This represents the measured roll rate.

5. The method for obtaining the uncontrolled roll angle of a rolling spring based on angular rate information according to claim 4, characterized in that, γ 主 This represents the roll angle value obtained through the arctangent function.

6. The method for obtaining the uncontrolled roll angle of a rolling spring based on angular rate information according to claim 1, characterized in that, Before S3, there is also step S2, which verifies the validity of radial gyroscope data and determines whether the inertial gyroscope measurement value is abnormal.

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