Guidance command analysis method based on control stiffness analysis

Abstract

The application discloses a guidance instruction analysis method based on control stiffness analysis, relates to the field of aircraft control and comprises the following steps: S1, acquiring a leading head signal, an input signal of a filter, an output signal of the filter and time before and after a unit step of a autopilot; S2, analyzing an equivalent time constant of a missile dynamics system; S3, calculating a normal demand overload n yc and a lateral demand overload n zc of a non-rolling missile system; S4, analyzing a normal overload instruction in a pitching channel in a guidance process; and S5, analyzing a rolling angle instruction of the missile. The control stiffness is a ratio of total guidance time and the equivalent time constant of the missile dynamics system, and necessary control stiffness is a prerequisite for ensuring the hitting precision of the missile. When the guidance time is greater than the equivalent time constant of the missile dynamics system by a set multiple, a trajectory is basically converged, the sign of the lateral demand overload can be used to finely adjust the rolling angle instruction, the effect of reducing the oscillation of the rolling angle instruction is achieved, and the quality of the guidance instruction is improved.

Description

Technical Field

[0001] This invention relates to the field of aircraft control, and more particularly to a guidance command analysis method based on control stiffness analysis. Background Technology

[0002] During missile guidance, lateral position control primarily involves lateral turning maneuvers. Commonly used turning control techniques include sideslip turn (STT) and yaw turn (BTT). BTT guidance utilizes a roll channel to rapidly rotate the missile's maximum lift surface to the maneuver direction required by the guidance law. The pitch channel controls the missile to generate the maneuver overload necessary for the guidance law, while the yaw channel coordinates the coupled motion of the pitch and roll channels, keeping the sideslip angle within a relatively small range. Missiles using BTT guidance significantly outperform those using STT guidance in terms of aerodynamic efficiency, maneuverability, and range. Based on the missile's aerodynamic design, overall shape, seeker, and propulsion system, BTT guidance is classified into three types: BTT-45°, BTT-90°, and BTT-180°. BTT-90° and BTT-180° are generally used for missiles with symmetrical layouts. The main difference between missiles guided by BTT-90° and BTT-180° lies in whether the missile can generate negative lift. In addition, the seeker also has certain limitations on the roll angle of the missile, such as the tracking algorithm of the image seeker and the deflection range of the frame seeker.

[0003] The guidance commands generated by BTT-90° include elevation channel overload commands and roll angle commands within the missile system. The missile's required overload in the normal and lateral directions within the non-rolling missile system is calculated based on the missile-target line-of-sight angular rate. The total overload of these two directions constitutes the missile system's elevation channel overload command. The conventional roll angle command is calculated as the arctangent of the ratio of the lateral to the normal required overload. However, during trajectory convergence, the lateral overload demand is affected by noise, oscillating near zero. When the normal overload demand is smaller than the lateral overload demand, or when the normal overload oscillates near zero, it can easily cause significant oscillations in the roll angle. Limiting the angle or angular rate can prevent the missile's maximum lift surface from accurately pointing towards the target, making accuracy difficult to guarantee. Summary of the Invention

[0004] The purpose of this invention is to design a guidance command analysis method based on control stiffness analysis in order to solve the above problems.

[0005] The present invention achieves the above objectives through the following technical solutions:

[0006] Guidance command analysis methods based on control stiffness analysis include:

[0007] S1. Acquire the guide head signal, the filter input signal, the filter output signal, and the time before and after the unit step of the autopilot;

[0008] S2. Analyze the equivalent time constant of the missile dynamics system based on the seeker signal, the filter input signal, the filter output signal, and the time before and after the unit step jump of the autopilot.

[0009] S3. Based on the guidance information and the current roll angle, calculate the normal overload requirement n of the non-rolling projectile system. yc and lateral demand overload n zc ;

[0010] S4. Let the flight time of the missile after entering guidance be T. Analyze the pitch channel normal overload command during the guidance process based on the flight time T and the equivalent time constant of the missile dynamics system.

[0011] S5. Analyze the missile roll angle command based on the normal demand overload, lateral demand overload, and equivalent time constant of the missile dynamics system for the non-rolling missile system.

[0012] The beneficial effects of this invention are as follows: control stiffness is the ratio of the total guidance time to the equivalent time constant of the missile dynamics system. Ensuring necessary control stiffness is a prerequisite for ensuring missile accuracy. The equivalent time of the missile dynamics system mainly consists of the seeker time constant, the guidance signal filtering time constant, and the autopilot time constant. When the guidance time is greater than a set multiple of the missile dynamics system's equivalent time, the trajectory basically converges. The roll angle command can be fine-tuned by adjusting the sign of the lateral demand overload, thereby reducing roll angle command oscillation and improving the quality of guidance commands. Attached Figure Description

[0013] Figure 1 This is a flowchart of the BTT-90° guidance command calculation process based on control stiffness;

[0014] Figure 2 This is a schematic diagram of the BTT-90° guidance command calculation principle based on control stiffness. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0016] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0017] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0018] In the description of this invention, it should be understood that the terms "upper," "lower," "inner," "outer," "left," "right," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use, or the orientation or positional relationship commonly understood by those skilled in the art. They are only used to facilitate the description of this invention and to simplify the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0019] Furthermore, the terms "first," "second," etc., are used only to distinguish descriptions and should not be interpreted as indicating or implying relative importance.

[0020] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, terms such as "set" and "connection" should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0021] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0022] like Figure 1 As shown, the guidance command analysis method based on control stiffness analysis includes:

[0023] S1. Acquire the guide head signal, the filter input signal, the filter output signal, and the time before and after the unit step of the autopilot.

[0024] S2. Analyze the equivalent time constant of the missile dynamics system based on the seeker signal, the filter input signal, the filter output signal, and the time before and after the unit step jump of the autopilot; specifically including:

[0025] S21. Analyze the seeker time constant based on the mathematical model of the seeker signal output response, analyze the seeker signal filtering time constant based on the input signal and output signal of the filter, and analyze the equivalent time constant of the autopilot based on the time before and after the unit step of the autopilot.

[0026] Seeker time constant: Based on the mathematical model of the seeker signal output response, the time corresponding to 63.2% of the maximum value of the unit step response is taken as the seeker time constant T. s ;

[0027] Guiding signal filtering time constant: Due to significant differences in filter algorithms, a general equivalent method is proposed here. A sinusoidal sweep signal is input to the filter's input, and the output signal at different frequencies is recorded at the output. The sinusoidal angular frequency corresponding to a drop in amplitude to 0.71 times the input amplitude is calculated. Then the time constant T of the guiding signal filtering f Represented as: ;

[0028] Autopilot equivalent time constant: For missiles using BTT-90° guidance, the autopilot consists of a control law and a missile body model, and is divided into an overload autopilot and a roll autopilot. Based on the unit step response of the autopilot, the time corresponding to the rise from zero to 63.2% is recorded, denoted as T. n and Then the equivalent time constant T of the autopilot c Represented as ;

[0029] S22. Analyze the equivalent time constant T of the missile dynamics system based on the seeker time constant, the guidance signal filtering time constant, and the autopilot equivalent time constant. d， Represented as: .

[0030] S3. Based on the guidance information and the current roll angle, calculate the normal overload requirement n of the non-rolling projectile system. yc and lateral demand overload n zc ;

[0031] S4. Let the flight time of the missile after entering guidance be T. Analyze the pitch channel normal overload command during the guidance process based on the flight time T and the equivalent time constant of the missile dynamics system; specifically including:

[0032] S41. Calculate the normal demand overload n of the non-rolling spring system. yc and lateral demand overload n zc Total overload;

[0033] S42. Determine whether the flight time T is less than N times the equivalent time constant T of the missile dynamics system. d ,Right now , if so, enter S43; otherwise, enter S44;

[0034] S43. At this time, the general trajectory has not yet converged, and the normal overload command in the pitch channel during the guidance process is equal to the total overload. Enter S5;

[0035] S44. At this time, the trajectory is basically converged. At this time, the overload command in the pitch channel changes slowly. Therefore, set the filtering time constant to T0, and use a first-order inertia to perform low-pass filtering on the total overload to eliminate high-frequency measurement noise, and obtain the normal overload command in the pitch channel during the guidance process. Enter S5.

[0036] In summary, the normal overload command in the pitch channel can be expressed as:

[0037] ;

[0038] where s is the Laplace complex variable, n c (s) is the Laplace transform of n c . In addition, in order to ensure the continuity of the command, the initial value of the overload in the stage is the final value of the

[0039] S5. Analyze the missile roll angle command according to the normal required overload, lateral required overload of the non-rolling missile system and the equivalent time constant of the missile dynamics system; specifically include:

[0040] S51. Judge whether the flight time T is less than N times the equivalent time constant T d of the missile dynamics system, that is . If so, enter S52; otherwise, enter S53;

[0041] S52. The missile roll angle command is the arctangent of the ratio of the normal required overload n yc and the lateral required overload n zc of the non-rolling missile system;

[0042] S53. At this time, the missile is basically aligned with the target, and the roll angle command only needs to be fine-tuned. Set the guidance period to T g , the maximum allowable roll angle rate of the missile is , calculate the roll angle command increment , expressed as: , where k is a protection coefficient, 0 < k < 1. Suppose the missile roll angle command at the nth moment is , then the roll angle command for the next period is expressed as . <000​​​​

[0045] N is not less than 8.

[0046] k=0.3.

[0047] Control stiffness is the ratio of the total guidance time to the equivalent time constant of the missile's dynamic system. Ensuring sufficient control stiffness is a prerequisite for guaranteeing missile accuracy, and it is generally 5 to 10 times the equivalent time constant of the missile's dynamic system. The equivalent time of the missile's dynamic system mainly consists of the seeker time constant, the guidance signal filtering time constant, and the autopilot time constant. When the guidance time is greater than 5 to 10 times the equivalent time of the missile's dynamic system, the trajectory essentially converges. The roll angle command can be fine-tuned by adjusting the sign of the lateral demand overload, thereby reducing roll angle command oscillation and improving the quality of guidance commands.

[0048] The technical solutions of the present invention are not limited to the specific embodiments described above. Any technical modifications made in accordance with the technical solutions of the present invention fall within the protection scope of the present invention.

Claims

1. A guidance command analysis method based on control stiffness analysis, characterized in that, include: S1. Acquire the guide head signal, the filter input signal, the filter output signal, and the time before and after the unit step of the autopilot; S2. Analyze the equivalent time constant of the missile dynamics system based on the seeker signal, the filter input signal, the filter output signal, and the time before and after the unit step jump of the autopilot. S3. Based on the guidance information and the current roll angle, calculate the normal overload requirement n of the non-rolling projectile system. yc and lateral demand overload n zc ; S4. Let the flight time of the missile after entering guidance be T. Analyze the pitch channel normal overload command during the guidance process based on the flight time T and the equivalent time constant of the missile dynamics system. S5. Analyze the missile roll angle command based on the normal overload requirement, lateral overload requirement, and equivalent time constant of the missile dynamics system for the non-rolling missile system; specifically including: S51. Determine whether the flight time T is less than N times the equivalent time constant T of the missile dynamics system. d If yes, proceed to S52; otherwise, proceed to S53. S52, the missile roll angle command is the normal overload requirement n for non-rolling missile systems. yc and lateral demand overload n zc The arctangent of the ratio; S53. Set the guidance period as T g , the maximum allowable roll angular rate of the missile is , calculate the increment of the roll angle command , expressed as: , where k is the protection coefficient, 0 < k < 1. Assume that the roll angle command of the missile at the nth moment is , then the roll angle command for the next period is expressed as .

2. The guidance command analysis method based on control stiffness analysis according to claim 1, characterized in that, S2 includes: S21. Analyze the seeker time constant based on the mathematical model of the seeker signal output response, analyze the seeker signal filtering time constant based on the input signal and output signal of the filter, and analyze the equivalent time constant of the autopilot based on the time before and after the unit step of the autopilot. S22. Analyze the equivalent time constant of the missile dynamics system based on the seeker time constant, the guidance signal filtering time constant, and the autopilot equivalent time constant.

3. The guidance command analysis method based on control stiffness analysis according to claim 2, characterized in that: Seeker time constant: Based on the mathematical model of the seeker signal output response, the time corresponding to 63.2% of the maximum value of the unit step response is taken as the seeker time constant T. s ; Guide signal filtering time constant: Input a sinusoidal sweep signal at the input of the filter and record the output signal at different frequencies at the output. Calculate the sinusoidal angular frequency corresponding to the amplitude decreasing to 0.71 times the input amplitude. Then the time constant T of the guiding signal filtering f Represented as: ; The equivalent time constant of the autopilot is recorded as T, based on the unit step response of the autopilot, representing the time from zero to 63.2%. n and Then the equivalent time constant T of the autopilot c Represented as ; The equivalent time constant T of the missile dynamics system d Represented as: .

4. The guidance command analysis method based on control stiffness analysis according to claim 1, characterized in that, S4 includes: S41. Calculate the normal demand overload n of the non-rolling spring system. yc and lateral demand overload n zc Total overload; S42. Determine whether the flight time T is less than N times the equivalent time constant T of the missile dynamics system. d If yes, proceed to S43; otherwise, proceed to S44. S43. During the guidance process, the pitch channel normal overload command equals the total overload, and the system enters S5. S44. Set the filtering time constant to T0, use first-order inertia to perform low-pass filtering on the total overload, obtain the pitch channel normal overload command during the guidance process, and proceed to S5.

5. The guidance command analysis method based on control stiffness analysis according to claim 4, characterized in that, N is not less than 5.

6. The guidance command analysis method based on control stiffness analysis according to claim 5, characterized in that, N is not less than 8.

7. The guidance command analysis method based on control stiffness analysis according to claim 4, characterized in that, k=0.3。

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