A method for identifying roll angle of guided shell based on three-axis gyroscope

Abstract

The application discloses a guiding shell roll angle identification method based on a three-axis gyroscope, taking the gyroscope measurement data of a shell body y-axis or z-axis as an input signal of a costa phase-locked loop, taking the gyroscope measurement data of the shell body x-axis direction as an input signal of a phase-locked loop, taking the phase of the output shell body roll angle after locking as an input signal of a phase-locked loop, and finally taking the inverse trigonometric function of the sine signal output by the phase-locked loop to obtain the roll angle x The center frequency ω c of the phase-locked loop VCO is improved according to the actual use of the guiding shell. The real-time data of the shell body longitudinal axis gyroscope is taken as the value of ω c , the center sensitivity of the VCO is adjusted, and the influence caused by the unstable roll angle speed is avoided.

Description

Technical Field

[0001] This invention relates to the field of guided projectile aerial alignment, and specifically to a method for identifying the roll angle of guided projectiles based on a three-axis gyroscope. Background Technology

[0002] As typical precision-guided weapons, guided projectiles are launched at high speeds from platforms such as artillery and electromagnetic railguns, and must withstand harsh conditions such as high overload and high rotational speed. Guided projectiles typically employ a high-speed rotation scheme during launch, followed by a controlled phase where the projectile is de-spinned and stabilized or rotates at a low speed. The inertial navigation system must then re-align the projectile in the air after launch. During in-air alignment, initial values ​​such as position, velocity, elevation angle, and yaw angle can be directly obtained from pre-set ballistic data or satellite receiver measurements. However, due to the randomness of the projectile's rotation during launch, the initial roll angle cannot be obtained. Therefore, identifying the initial roll angle of the projectile is a key technical challenge in the research of in-air alignment of rotating guided projectiles. Summary of the Invention

[0003] To address the aforementioned shortcomings in the existing technology, this invention provides a method for identifying the roll angle of guided projectiles based on a three-axis gyroscope.

[0004] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows:

[0005] A method for identifying the roll angle of guided projectiles based on a three-axis gyroscope includes the following steps:

[0006] S1. After the guided projectile is launched, the projectile body maintains a stable roll angle. The y-axis or z-axis measurement data of the projectile gyroscope is low-pass filtered to obtain a constant drift. The constant drift is then filtered out to obtain a sinusoidal signal of the gyroscope measurement data.

[0007] S2. The sinusoidal signal of the gyroscope measurement data is phase-shifted to obtain two outputs, I and Q, and then filtered by a low-pass filter to obtain the phase difference signal of the phase-shifted I and Q.

[0008] S3. Design a Costa phase-locked loop (PLL). Use the measurement data of the x-axis of the projectile gyroscope as the center frequency of the Costa PLL. Input the phase difference signal from the I and Q outputs as the input signal to the Costa PLL and output the phase signal.

[0009] S4. The roll angle of the projectile is calculated by using the inverse trigonometric function on the output phase signal.

[0010] Furthermore, the sinusoidal signal of the gyroscope measurement data in S1 is represented as follows:

[0011]

[0012] Wherein, ω(t) is the sinusoidal signal of the y-axis or z-axis measurement data of the projectile gyroscope at time t. B represents the measurement data at time t of the projectile gyroscope's y-axis or z-axis, and B represents the constant drift obtained by filtering the projectile gyroscope's y-axis or z-axis measurement data. Let ω be the pitch angular velocity of the projectile at time t. c γ is the center frequency of the voltage-controlled oscillator, and γ0 is the initial roll angle of the projectile.

[0013] Furthermore, in S2, the sinusoidal signal of the gyroscope measurement data is phase-shifted to obtain the I-channel and Q-channel outputs, which are respectively expressed as follows:

[0014]

[0015] Among them, Z I (t) represents the phase-shifted I-channel output, s I (t) represents the frequency multiplication term of the I-path, z Q (t) represents the phase-shifted Q-channel output, s Q (t) represents the Q-channel frequency multiplication term. Let ω be the pitch angular velocity of the projectile at time t. c γ is the center frequency of the voltage-controlled oscillator, and γ0 is the initial roll angle of the projectile. This is the initial roll angle phase.

[0016] Furthermore, the Costa phase-locked loop in S3 includes a phase detector, a loop filter, and a voltage-controlled oscillator. The two input terminals of the phase detector are connected to the output terminals of the I and Q channels, respectively. The phase detector is connected to the loop filter and the voltage-controlled oscillator in sequence. The output of the voltage-controlled oscillator serves as the output terminal of the phase signal and is also connected to the phase detector to form a closed loop.

[0017] Furthermore, the output of the phase detector in S3 is expressed as follows:

[0018]

[0019] Where e(t) is the output of the phase detector at time t, and γ0 is the initial roll angle of the projectile. This is the initial roll angle phase.

[0020] Furthermore, the mathematical model of the voltage-controlled oscillator in S3 is expressed as follows:

[0021]

[0022] in, Let u be the roll angle phase at time t. c (t) represents the phase difference signal at time t, u VCO (t) represents the phase difference signal output by the phase-locked loop at time t, ω cHere, is the center frequency of the voltage-controlled oscillator, and K is the sensitivity of the voltage-controlled oscillator.

[0023] Furthermore, the projectile roll angle output in S4 is expressed as:

[0024]

[0025] in, For roll angle phase, Let ω be the initial roll angle phase. c t is the center frequency of the voltage-controlled oscillator, and t is time.

[0026] The present invention has the following beneficial effects:

[0027] Based on the concept of the Costas phase-locked loop, improvements were made to the VCO to better suit the actual use of guided projectiles. Real-time data from the projectile's longitudinal axis gyroscope was used as ω. c The value of is used to adjust the center sensitivity of the VCO, effectively avoiding the adverse effects of factors such as gyroscope drift on the phase-locked loop's roll angle identification. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the process for identifying the roll angle of guided projectiles based on a three-axis gyroscope, according to the present invention.

[0029] Figure 2 This is a schematic diagram of the phase-locked loop structure according to an embodiment of the present invention.

[0030] Figure 3 This is a block diagram of a roll angle alignment scheme based on a Costas phase-locked loop according to an embodiment of the present invention. Detailed Implementation

[0031] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0032] A method for identifying the roll angle of guided projectiles based on a three-axis gyroscope, such as Figure 1 As shown, it includes the following steps:

[0033] S1. After the guided projectile is launched, the projectile body maintains a stable roll angle. The y-axis or z-axis measurement data of the projectile gyroscope is low-pass filtered to obtain a constant drift. The constant drift is then filtered out to obtain a sinusoidal signal of the gyroscope measurement data.

[0034] During the flight of a spinning guided projectile, the projectile's pitch angle continuously changes due to the influence of gravity, thus the projectile possesses a certain pitch velocity. Meanwhile, considering that the change in yaw angle is extremely small during the period after the projectile leaves the barrel, it can be approximated as not changing the course, i.e., the yaw rate is... It is approximately 0. Due to the high-speed rotation of the projectile about its longitudinal axis, y... b axis or z b Pitch rate sensed on the axis gyroscope It also exhibits a sinusoidal trend, and the relationship is as follows:

[0035]

[0036] Therefore, it is only necessary to identify y b axis or z b The roll angle alignment can be achieved by using the phase of the axis gyroscope data.

[0037] In practice, gyroscope data is affected by factors such as gyroscope drift, installation errors, and the flight stability of the projectile, leading to variations in actual gyroscope data. and There exists a DC component B x B y and B z Its form is as follows:

[0038]

[0039] To extract the AC component from the gyroscope data without disrupting its waveform, a low-pass filter is used to filter the gyroscope data. and Filtering is performed to obtain the DC component B. y and B z Subtracting the filtered DC component from the gyroscope data yields the sine and cosine form of ω. y and ω z .

[0040]

[0041] S2. The sinusoidal signal of the gyroscope measurement data is phase-shifted to obtain two outputs, I and Q, and then filtered by a low-pass filter to obtain the phase difference signal of the phase-shifted I and Q.

[0042] In this embodiment, the low-pass filter is designed in the following way:

[0043] 1. Determine the minimum frequency f of the clutter signal by plotting the spectrum curve. min ;

[0044] 2. Calculate the maximum normalized cutoff frequency f of the low-pass filter. n As shown in the following formula:

[0045]

[0046] In the formula f s The sampling frequency.

[0047] 3. The normalized cutoff frequency of the designed low-pass filter is less than f. n This will satisfy the filtering requirements.

[0048] Input signal After processing with a low-pass filter, an approximate DC component B can be obtained, and thus:

[0049]

[0050] in The pitch angular velocity can be approximated as a non-zero constant.

[0051] Multiplying the signal ω(t) by the mutually orthogonal sine waves output by the VCO, we get:

[0052]

[0053] Among them, z I ( / ) represents the phase-shifted I-channel output, s I (t) represents the frequency multiplication term of the I-path, V Q (t) represents the phase-shifted Q-channel output, s Q (t) represents the Q-channel frequency multiplication term. Let ω be the pitch angular velocity of the projectile at time t. c γ is the center frequency of the voltage-controlled oscillator, and γ0 is the initial roll angle of the projectile. This is the initial roll angle phase.

[0054] S3. Design a Costa phase-locked loop (PLL). Use the measurement data of the x-axis of the projectile gyroscope as the center frequency of the Costa PLL. Input the phase difference signal from the I and Q outputs as the input signal to the Costa PLL and output the phase signal.

[0055] A phase-locked loop (PLL) is a phase feedback tracking system for periodic signals. A PLL consists of a phase detector, a loop filter, and a voltage-controlled oscillator (VCO), such as... Figure 2As shown. A phase detector is typically implemented using a multiplier. The phase error signal output by the phase detector is filtered by a loop filter and used as the control signal for the voltage-controlled oscillator (VCO). The output of the VCO is then fed back to the phase detector, where it is compared with the input signal. The PLL is a phase negative feedback system. When the PLL is locked, the phase of the VCO's output signal tracks the phase change of the input signal. At this point, the frequency of the VCO's output signal is equal to the frequency of the input signal, while the phase maintains a small error.

[0056] Specifically, the mathematical model of a voltage-controlled oscillator (VCO) is as follows:

[0057]

[0058] In the formula, K represents the VCO sensitivity.

[0059] The function of low-pass filter 1 and low-pass filter 2 is to filter out the harmonic terms s of the I and Q branches. I (t) and s Q (t), retaining the constant component and

[0060] The design schemes for low-pass filter 1 and low-pass filter 2 are as follows:

[0061] (a) Determine the harmonic term s I (t) and s Q The frequency f of (t) I,Q =2ω c ;

[0062] (b) Calculate the maximum normalized cutoff frequency f of the low-pass filter. n(I,Q) As shown in the following formula:

[0063]

[0064] The normalized cutoff frequency of the designed low-pass filter is less than f. n(I,Q) This will satisfy the filtering requirements.

[0065] The loop filter design is as follows:

[0066] (a) Determine the minimum frequency f of the clutter signal by plotting the spectrum curve. e ;

[0067] (b) Calculate the maximum normalized cutoff frequency f of the low-pass filter. n(I,Q) As shown in the following formula:

[0068]

[0069] (c) The normalized cutoff frequency of the designed low-pass filter is less than f. n(e)This will satisfy the filtering requirements;

[0070] The phase detector uses a four-quadrant reverse-cut phase detector, and its mathematical model is as follows:

[0071]

[0072] In summary, as Figure 3 As shown, after filtering by low-pass filter 1 and low-pass filter 2 respectively, the frequency multiplication term is filtered out. Therefore, the output of the phase detector is:

[0073]

[0074] The error signal, after being filtered by the loop filter, is used as the control signal u of the VCO. c (t), after the phase-locked loop is locked, the phase difference will remain at a small value.

[0075] S4. The roll angle of the projectile is calculated by using the inverse trigonometric function on the output phase signal.

[0076] The processed y-axis or z-axis gyroscope measurement data ω is input into the Costas loop, and the VCO outputs a signal.

[0077] The phase of the gyroscope data signal can be determined using inverse trigonometric functions. This refers to the projectile roll angle;

[0078] in, For roll angle phase, Let ω be the initial roll angle phase. c t is the center frequency of the voltage-controlled oscillator, and t is time.

[0079] Because it is difficult to achieve stable control of the roll velocity of a projectile while it is in flight, therefore, if ω c Setting a predetermined projectile roll velocity can lead to the phase-locked loop (PLL) failing to lock onto the phase during actual flight, affecting alignment time and accuracy. This invention, based on the concept of the Costas PLL, makes improvements to the VCO to better suit the actual use of guided projectiles. It uses real-time data from the projectile's longitudinal axis gyroscope as ω... c The value is adjusted to control the center sensitivity of the VCO, thus avoiding the effects of unstable roll angular velocity.

[0080] Specific embodiments have been used to illustrate the principles and implementation methods of this invention. The descriptions of the embodiments above are only for the purpose of helping to understand the method and core ideas of this invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this invention. Therefore, the content of this specification should not be construed as a limitation of this invention.

[0081] Those skilled in the art will recognize that the embodiments described herein are intended to help the reader understand the principles of the invention, and should be understood that the scope of protection of the invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific modifications and combinations based on the technical teachings disclosed in this invention without departing from the spirit of the invention, and these modifications and combinations are still within the scope of protection of this invention.

Claims

1. A method for identifying the roll angle of guided projectiles based on a three-axis gyroscope, characterized in that, Includes the following steps: S1. After the guided projectile is launched, the projectile body maintains a stable roll angle. The y-axis or z-axis measurement data of the projectile gyroscope is low-pass filtered to obtain a constant drift. The constant drift is then filtered out to obtain a sinusoidal signal of the gyroscope measurement data. S2. The sinusoidal signal of the gyroscope measurement data is phase-shifted to obtain two outputs, I and Q, and then filtered by a low-pass filter to obtain the phase difference signal of the phase-shifted I and Q. S3. Design a Costa phase-locked loop (PLL). Use the measurement data of the x-axis of the projectile gyroscope as the center frequency of the Costa PLL. Input the phase difference signal from the I and Q outputs as the input signal to the Costa PLL and output the phase signal. S4. The roll angle of the projectile is calculated by using the inverse trigonometric function on the output phase signal.

2. The method for identifying the roll angle of guided projectiles based on a three-axis gyroscope according to claim 1, characterized in that, The sinusoidal signal of the gyroscope measurement data in S1 is represented as follows: Wherein, ω(t) is the sinusoidal signal of the y-axis or z-axis measurement data of the projectile gyroscope at time t. B represents the measurement data at time t of the projectile gyroscope's y-axis or z-axis, and B represents the constant drift obtained by filtering the projectile gyroscope's y-axis or z-axis measurement data. Let ω be the pitch angular velocity of the projectile at time t. c γ is the center frequency of the voltage-controlled oscillator, and γ0 is the initial roll angle of the projectile.

3. The method for identifying the roll angle of guided projectiles based on a three-axis gyroscope according to claim 1, characterized in that, In S2, the sinusoidal signal of the gyroscope measurement data is phase-shifted to obtain the I-channel and Q-channel outputs, which are respectively represented as follows: Among them, z I (t) represents the phase-shifted I-channel output, s I (t) represents the frequency multiplication term of the I-path, z Q (t) represents the phase-shifted Q-channel output, s Q (t) represents the Q-channel frequency multiplication term. Let ω be the pitch angular velocity of the projectile at time t. c γ is the center frequency of the voltage-controlled oscillator, and γ0 is the initial roll angle of the projectile. This is the initial roll angle phase.

4. The method for identifying the roll angle of guided projectiles based on a three-axis gyroscope according to claim 1, characterized in that, The Costa phase-locked loop in S3 includes a phase detector, a loop filter, and a voltage-controlled oscillator. The two input terminals of the phase detector are connected to the output terminals of the I and Q channels, respectively. The phase detector is connected to the loop filter and the voltage-controlled oscillator in sequence. The output of the voltage-controlled oscillator serves as the output terminal of the phase signal and is simultaneously fed back to the phase detector for comparison with the input signal.

5. The method for identifying the roll angle of guided projectiles based on a three-axis gyroscope according to claim 4, characterized in that, The output of the phase detector in S3 is expressed as follows: Where e(t) is the output of the phase detector at time t, and γ0 is the initial roll angle of the projectile. The initial roll angle phase, Let t be the pitch angular velocity of the projectile at time t.

6. The method for identifying the roll angle of guided projectiles based on a three-axis gyroscope according to claim 5, characterized in that, The mathematical model of the voltage-controlled oscillator in S3 is expressed as follows: in, Let u be the roll angle phase at time t. c (t) represents the phase difference signal at time t, u VCO (t) represents the phase difference signal output by the phase-locked loop at time t, ω c Here, is the center frequency of the voltage-controlled oscillator, and K is the sensitivity of the voltage-controlled oscillator.

7. The method for identifying the roll angle of guided projectiles based on a three-axis gyroscope according to claim 1, characterized in that, The projectile roll angle output in S4 is expressed as: in, For roll angle phase, Let ω be the initial roll angle phase. c t is the center frequency of the voltage-controlled oscillator, and t is time.

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