Unpowered missile dive-pull combined guidance method for opening umbrella accuracy
Patent Information
- Application Number
- CN202611004588.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-07-07
- Publication Date
- 2026-09-25
AI Technical Summary
当弹体在较大俯冲角、较大滚转角或存在显著角速度情况下开伞时，易产生伞绳缠绕、开伞冲击过大或伞衣展开不对称等问题，从而导致开伞失败或落点散布显著增加
[0132]本发明提供的面向开伞精度的无动力弹俯冲-拉起联合制导方法具有以下优点：本发明通过在制导过程中引入开伞点预测与姿态约束，实现弹体在目标点上方预定高度窗口内以受控姿态稳定开伞，从而提高开伞可靠性并减小落点散布。
Smart Images
Figure CN122816233A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of aircraft guidance and control technology, specifically to a combined dive-pull guidance method for unpowered missiles aimed at parachute deployment accuracy. Background Technology
[0002] Existing unpowered airdrop guidance methods typically prioritize minimizing impact point error, employing proportional guidance, trajectory shaping, or path planning-based control strategies. These methods generally simplify terminal state constraints to "reaching the vicinity of the target point," without designing constraints for the attitude state at the moment of parachute deployment.
[0003] In practical applications, the parachute deployment process is highly sensitive to the projectile's attitude. When the parachute deploys at a large dive angle, a large roll angle, or with a significant angular velocity, problems such as parachute line entanglement, excessive deployment impact, or asymmetrical canopy deployment can easily occur, leading to deployment failure or a significant increase in the dispersion of the landing point.
[0004] Furthermore, existing methods for triggering parachute deployment typically rely on a single altitude threshold, failing to consider whether the projectile's attitude meets safe deployment conditions or the impact of the current flight status on the future deployment location. Therefore, in the presence of wind disturbances or uncertain aerodynamic parameters, it is difficult to simultaneously guarantee deployment reliability and landing accuracy.
[0005] In summary, existing technologies lack a unified guidance method that can simultaneously constrain the parachute deployment position and attitude. Summary of the Invention
[0006] To address the shortcomings of existing technologies, this invention provides a combined dive-pull guidance method for unpowered projectiles with high parachute deployment accuracy, which can effectively solve the aforementioned problems.
[0007] The technical solution adopted in this invention is as follows:
[0008] This invention provides a combined dive-pull guidance method for unpowered projectiles with improved parachute deployment accuracy, comprising the following steps:
[0009] Step S1: Preset the target position of the projectile; determine the target position for parachute deployment based on the target position of the projectile; the target position for parachute deployment includes the horizontal position and the height of the target position for parachute deployment.
[0010] Step S2: During the entire descent phase from missile launch to parachute deployment, based on the missile's current state data and environmental data, a horizontal range prediction model is used to obtain the predicted horizontal range when the missile maintains its current glide ratio and speed as it descends to the parachute deployment target altitude. The predicted horizontal range is compared with the target horizontal range value to obtain the horizontal range prediction error in real time. The target horizontal range value is the horizontal range between the missile's current position and the parachute deployment target position.
[0011] Step S3: After the projectile is released from the launch point, it first enters the mid-course dive guidance phase. In the mid-course dive guidance phase, the mid-course dive guidance law is used in real time to calculate the acceleration requirement command that makes the projectile approach the parachute target position, and the acceleration requirement command is converted into the projectile attitude adjustment command, thereby realizing the real-time adjustment of the projectile attitude.
[0012] Step S4: During the mid-course dive guidance phase, it is determined in real time whether the pull-up switching judgment condition is met; if not, step S3 is continued; if it is met, the projectile enters the pull-up phase and step S5 is executed.
[0013] In step S5, during the pull-up phase, an attitude leveling control law is used to adjust the projectile's attitude in real time, so that the projectile smoothly transitions from a dive state to a near-horizontal state and continues to maintain a near-horizontal state until the preset parachute opening judgment is met, triggering parachute opening.
[0014] Furthermore, step S1 includes:
[0015] Step S11: Preset the target position of the projectile in the inertial coordinate system. , These represent the northward, eastward, and altitude positions of the missile target.
[0016] Step S12, based on the target position of the projectile Determine the target location for parachute deployment by setting an altitude position directly above it. , The target altitude for parachute deployment.
[0017] Furthermore, step S2 includes:
[0018] Step S21: During the entire descent phase from projectile deployment to parachute opening, acquire the projectile's current state data and environmental data; the projectile's current state data includes the projectile's current position. Current trajectory inclination of the missile body Current velocity scalar of the projectile and the projectile's current velocity direction; the environmental data includes wind speed vector. ; These represent the missile's current northward position, eastward position, and current altitude;
[0019] Step S22: Introduce the influence of wind speed and construct a comprehensive horizontal range prediction model:
[0020] (1)
[0021] in: This is the predicted horizontal range. For equivalent glide ratio, , For lift, As resistance; The remaining height ; This is the unit vector in the direction of the projectile's current velocity. To allow the missile to fall to the target altitude where the parachute opens The predicted fall time. ;
[0022] Step S23: Using the aforementioned horizontal range prediction model, the projectile's descent to the parachute deployment target altitude while maintaining its current glide ratio and speed under wind speed influence is obtained in real time. Horizontal range prediction value at time ;
[0023] Step S24: Calculate the horizontal range target value :
[0024] (2)
[0025] Step S25: Calculate the horizontal range prediction error. :
[0026] (3)
[0027] This step is now complete.
[0028] Furthermore, step S3 includes:
[0029] Step S31, the mid-course dive guidance law includes a horizontal channel guidance law and a vertical channel guidance law;
[0030] Step S32: Using the horizontal channel guidance law, eliminate the horizontal line-of-sight rotation deviation of the projectile's current position relative to the parachute-deployed target position, and calculate the lateral acceleration requirement command. ;
[0031] Step S33: Using the vertical channel guidance law, eliminate the rotational deviation of the projectile's current position relative to the parachute-opening target position in the vertical line of sight, and simultaneously correct the predicted parachute opening height error to calculate the normal acceleration requirement command. ;
[0032] Step S34, respectively send the lateral acceleration demand commands and normal acceleration demand command Converted to roll channel rudder deflection command and pitch channel rudder deflection commands This allows for real-time adjustment of the projectile's roll and pitch attitudes, enabling the projectile to approach the parachute deployment target position.
[0033] Furthermore, step S32 includes:
[0034] Step S321, define the current position of the projectile. Relative to the target position of parachute opening line-of-sight vector :
[0035] (4)
[0036] Step S322: To achieve horizontal guidance, a horizontal line-of-sight angle is introduced. :
[0037] (5)
[0038] Define the rate of change of the horizontal line of sight angle Reflects the angular velocity of rotation of the horizontal line of sight:
[0039] (6)
[0040] in: , which is the horizontal distance from the current position of the projectile to the parachute deployment target position; and These represent the northward and eastward components of the projectile's velocity, respectively.
[0041] Step S323: Construct the horizontal channel guidance law and calculate the lateral acceleration demand command. ;
[0042] (7)
[0043] in: The command is for lateral acceleration, and its direction is perpendicular to the projection of the projectile's velocity vector onto the horizontal plane. The horizontal navigation ratio is a dimensionless constant.
[0044] Step S33 includes:
[0045] Step S331: To achieve vertical guidance, a vertical line-of-sight angle is introduced. :
[0046] (8)
[0047] Define the rate of change of the vertical line of sight angle Reflects the angular velocity of rotation perpendicular to the line of sight:
[0048] (9)
[0049] in: The derivative of the horizontal distance from the current position of the projectile to the target position after parachute deployment; The derivative of the projectile's current height;
[0050] (10)
[0051] Step S332: Construct the vertical channel guidance law to eliminate the rotation of the projectile's current position relative to the parachute-opening target position in the vertical line of sight, while correcting the predicted parachute opening height error, and then calculate the normal acceleration requirement command. ;
[0052] (11)
[0053] in: This is a command for normal acceleration, with the direction perpendicular to the projectile's velocity vector and pointing upwards; The vertical navigation ratio is dimensionless. This is the height error correction factor, a positive constant. To predict the parachute opening height error, it is defined as:
[0054] (12)
[0055] in: For the missile body to reach the horizontal position of the parachute-deployed target at the current glide ratio The predicted height of the projectile, i.e., the predicted parachute deployment height, is expressed as:
[0056] (13)
[0057] when When the energy is greater than 0, the projectile has excess energy and needs to increase its dive; when When the energy level is less than 0, the projectile's energy is insufficient, requiring a reduction in dive or even a nose-up.
[0058] Furthermore, step S34 includes:
[0059] Step S341, according to the lateral acceleration demand command Generate the desired roll angle :
[0060] By rolling, the projectile's main lifting surface is aligned with the direction of the required lateral acceleration, and then the lateral force is generated by the normal acceleration. Therefore:
[0061] (14)
[0062] in: It is the acceleration due to gravity; This is the current pitch angle of the missile body, due to the mid-course dive guidance phase. The changes are minor and approximate. Therefore, we obtain formula (15):
[0063] (15)
[0064] Step S342, according to the normal acceleration requirement command Generate desired pitch angle :
[0065] Since normal acceleration is mainly generated by lift, therefore:
[0066] (16)
[0067] in: For the mass of the projectile; The inclination angle of the missile's current trajectory; due to lift Lift coefficient within a small angle of attack range The required angle of attack is obtained by inverse solving. :
[0068] (17)
[0069] in: air density; For the projectile's velocity scalar; This is the aerodynamic reference area; The lift coefficient at zero angle of attack is a constant. The slope of the lift line; For the current angle of attack, ;
[0070] Then the expected pitch angle for:
[0071] (18)
[0072] Step S343: Calculate the aileron deflection angle of the roll path respectively. Elevator deflection in the pitch channel :
[0073] (19)
[0074] (20)
[0075] in: This is the current roll angle of the projectile; The desired roll rate is usually set to zero to avoid overshoot; This represents the projectile's current roll angular velocity. These are the roll channel ratio and the differential gain, respectively. This is the current pitch angle of the projectile; The current pitch velocity of the projectile; To achieve the desired pitch rate, it is usually set to zero to avoid overshoot; and These are the pitch channel ratio and differential gain, respectively. This is a feedforward term used to counteract the gravitational tilting torque. The expression is:
[0076] (twenty one)
[0077] This step is now complete.
[0078] Furthermore, in step S4, the condition for determining the pull-up switching is:
[0079] Step S41: Determine if the remaining height requirement is met. Judgment conditions:
[0080] (twenty two)
[0081] in: The height reserved for pull-up is a normal number, representing the maximum allowable remaining height for triggering the switch from the mid-course dive guidance phase to the pull-up phase;
[0082] If the condition is not met, the conclusion that the switchover condition is not met is directly drawn; if the condition is met, step S42 is executed.
[0083] Step S42, Comprehensive performance index determination mechanism:
[0084] Define the cost function :
[0085] (twenty three)
[0086] in: The weighting coefficients for the horizontal range prediction error term; This refers to the horizontal range prediction error. This is the weighting factor for the remaining height term; The weighting coefficient for the track inclination term; The inclination angle of the missile's current trajectory;
[0087] Judgment cost function Does it satisfy formula (24)?
[0088] (twenty four)
[0089] in: The switching cost threshold is a normal number that represents the maximum combined cost allowed to switch from the mid-course dive guidance phase to the pull-up phase.
[0090] If formula (24) is satisfied, it is considered that the projectile has simultaneously met the requirements of horizontal accuracy, remaining height and attitude smoothness, and the conclusion is that the pull-up switching judgment condition is met; if not, the conclusion is that the pull-up switching judgment condition is not met.
[0091] Furthermore, in step S5, during the pull-up phase, an attitude leveling control law is employed to adjust the projectile's attitude in real time, allowing the projectile to smoothly transition from a dive to a near-horizontal state, ensuring that attitude and angular velocity constraints are met at the moment of parachute deployment. The attitude leveling control law includes a pitch channel control law and a roll channel control law; specifically, it includes:
[0092] Step S51, set the attitude leveling control target:
[0093] (25)
[0094] Specifically, the current trajectory inclination angle of the missile body Approaching 0, and the projectile's current pitch angle Approaching the desired pitch angle This ensures that the projectile tilts slightly during parachute deployment, which facilitates smooth parachute deployment and reduces impact. Furthermore, the projectile's current roll angle... Approaching 0; simultaneously requiring the projectile's current pitch angular velocity. and the projectile's current roll angular velocity Converging to near zero prevents the parachute lines from becoming tangled due to excessive angular velocity at the moment of opening;
[0095] Step S52, initiate trajectory planning:
[0096] To ensure a smooth pull-up process and continuous control input, an ideal trajectory for varying the inclination angle is pre-designed to guarantee smooth changes in aerodynamic loads during the pull-up and avoid stall or oscillation caused by sudden pull-ups.
[0097] (26)
[0098] in: The inclination angle of the missile's current trajectory; The desired rate of change of track inclination; The convergence rate coefficient of the trajectory inclination angle determines the current trajectory inclination angle of the missile. The rate of convergence to zero is determined by the coefficient. The larger the coefficient, the faster the pull-up process and the higher the rate of exponential decay of the track inclination angle; the smaller the coefficient, the smoother the pull-up process.
[0099] Step S53: Employ the pitch channel control law to adjust the rate of change of the missile's actual trajectory tilt angle. Tracking the desired rate of change of track inclination From this, the desired lift, desired angle of attack, and desired pitch angle are deduced, and finally the elevator deflection angle is calculated using the pitch angle tracking control law.
[0100] Step S54: Using the roll channel control law, calculate the aileron deflection angle required to keep the missile body from rolling during the pull-up process;
[0101] In step S55, the elevator deflection angle and aileron deflection angle are used to adjust the missile attitude in real time, so that the missile pitch angle and roll angle continuously approach zero throughout the pull-up phase.
[0102] Furthermore, step S53 includes:
[0103] Step S531: Calculate the rate of change of the actual trajectory angle of the missile body. :
[0104] (27)
[0105] in: For lift; For the mass of the projectile; It is the acceleration due to gravity; For the projectile's velocity scalar; The inclination angle of the missile's current trajectory;
[0106] Step S532, let = Calculate the expected lift. :
[0107] (28)
[0108] Step S533, based on the lift model, from the desired lift... Inverse solution to obtain the expected angle of attack :
[0109] The lift model is as follows:
[0110] (29)
[0111] in: air density; This is the aerodynamic reference area; The current velocity of the projectile is a scalar; the lift coefficient is... Linearization within the small to medium angle of attack range ; The lift coefficient at zero angle of attack is a constant. The slope of the lift line; Define the current angle of attack. Therefore, the expected angle of attack can be derived from this. :
[0112] (30)
[0113] Step S534, according to the desired angle of attack The desired pitch angle is calculated. :
[0114] (31)
[0115] Step S535: Obtain the elevator deflection angle according to the pitch angle tracking control law. :
[0116] (32)
[0117] in: This is the current pitch angle of the projectile; The current pitch velocity of the projectile; To achieve the desired pitch rate, it is usually set to zero to avoid overshoot; , These are the pitch channel ratio and differential gain, respectively. The feedforward term is used to counteract the gravitational pitching torque, and its expression is:
[0118] (33)
[0119] In step S54, the roll channel control law is:
[0120] (34)
[0121] in: For aileron deflection; This is the current roll angle of the projectile; This represents the projectile's current roll angular velocity. , These are the roll-off channel ratio and the differential gain, respectively.
[0122] Furthermore, the parachute deployment determination is a multi-condition fusion parachute deployment determination, including:
[0123] Condition 1: Height condition: ;
[0124] Condition 2: Attitude Conditions: ;
[0125] Condition 3: Dynamic Constraints ;
[0126] Condition 4: Redundancy triggering mechanism: , ;
[0127] in: This is the current height of the projectile; Target altitude for parachute deployment; This is the current pitch angle of the projectile; This is the current roll angle of the projectile; The current pitch velocity of the projectile; This represents the projectile's current roll angular velocity. , , and These are the maximum values of the projectile's pitch angle, roll angle, pitch velocity, and roll velocity, respectively. The axial acceleration of the projectile. This is a preset positive constant, representing the threshold for acceleration abrupt changes.
[0128] When conditions 1, 2, and 3 are met simultaneously, the parachute is deployed; when condition 4 is met, the parachute is forcibly deployed.
[0129] The parachute opening determination is expressed as a comprehensive logic:
[0130] (35)
[0131] in: This indicates that the parachute has been deployed; Represents logical AND; Represents logical OR.
[0132] The unpowered projectile dive-pull combined guidance method for parachute deployment accuracy provided by this invention has the following advantages: By introducing parachute deployment point prediction and attitude constraints during the guidance process, this invention enables the projectile to deploy its parachute stably in a controlled attitude within a predetermined height window above the target point, thereby improving the reliability of parachute deployment and reducing the dispersion of the impact point. Attached Figure Description
[0133] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0134] Figure 1 A schematic diagram of the structure of the unpowered projectile provided by the present invention;
[0135] Figure 2 A system hardware connection diagram for an unpowered projectile provided by the present invention;
[0136] Figure 3 A flowchart of the unpowered projectile's dive-pull-up combined guidance method for parachute deployment accuracy provided by the present invention;
[0137] Figure 4 A schematic diagram of the dive-pull-pull combined guidance principle provided by the present invention.
[0138] Wherein: 1-Head of missile body; 2-Main section of missile body; 3-Short wing glide surface; 4-X-type tail rudder; 5-Flight control computer; 6-Inertial measurement unit; 7-Barometric altimeter; 8-Parachute opening mechanism; 9-Parachute compartment; 10-Deployment point; 11-Dive trajectory; 12-Pull-up switching point; 13-Pull-up trajectory; 14-Parachute opening point; 15-Target point. Detailed Implementation
[0139] To make the technical problems solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the invention.
[0140] To address the issue that traditional guidance systems only focus on terminal hit error while neglecting parachute opening attitude constraints, this invention expands the control target from "hitting the target point" to "opening the parachute within a predetermined altitude window above the target point in a state that satisfies attitude and motion constraints." The unpowered missile dive-pull combined guidance method provided by this invention, which focuses on parachute opening accuracy, is a terminal guidance method for unpowered air-dropped missiles or air-dropped payloads. It is particularly suitable for application scenarios where there are constraints on attitude and position accuracy at the moment of parachute opening under medium-to-high altitude delivery conditions (such as a delivery altitude of 500–1000 meters).
[0141] To achieve the above objectives, this invention constructs a hierarchical guidance system consisting of real-time prediction of the horizontal range and error when falling to the parachute deployment target altitude, trajectory convergence control, phase switching decision-making, and attitude stabilization control. This system presents a continuous closed-loop control process in time and forms a complete logical chain of "prediction—correction—switching—stabilization—triggering" in function.
[0142] It should be noted that this invention does not limit the structure of the air-dropped unpowered munition, as long as its attitude can be actively adjusted after deployment. As a specific implementation structure, such as... Figure 1 The diagram shown is a structural schematic of a type of unpowered missile, including: 1. missile head section; 2. main missile section; 3. stub wing glide surface; 4. X-shaped tail rudder; 5. flight control computer; 6. inertial measurement unit; 7. barometric altimeter; 8. parachute deployment mechanism; and 9. parachute compartment. Figure 2The diagram shows the hardware connection of a type of unpowered projectile. After the projectile is deployed, its current status data, including its current position, trajectory angle, and velocity, can be measured in real time via GPS and an inertial measurement unit. The wind speed vector at the projectile's location is measured in real time via a barometer. Its X-shaped tail rudder 4 has four servo motors; by controlling these four motors, the projectile's real-time attitude, including roll and pitch, can be actively controlled.
[0143] like Figure 3 The diagram shows a flowchart of a combined dive-pull guidance method for unpowered projectiles, focusing on parachute deployment accuracy, provided by the present invention. Figure 4 The diagram shown is a schematic of a combined dive-pull guidance method for unpowered projectiles with improved parachute deployment accuracy, provided by the present invention, including the following steps S1 to S5:
[0144] Step S1: Preset the target position of the projectile; determine the target position for parachute deployment based on the target position of the projectile; the target position for parachute deployment includes the horizontal position and the height of the target position for parachute deployment.
[0145] This step is specifically as follows:
[0146] Step S11: Preset the target position of the projectile in the inertial coordinate system. , These represent the northward, eastward, and altitude positions of the missile target.
[0147] Step S12, based on the target position of the projectile Determine the target location for parachute deployment by setting an altitude position directly above it. , The target altitude for parachute deployment.
[0148] Step S2, real-time prediction of horizontal flight path and error construction when falling to the target altitude of parachute deployment:
[0149] Throughout the descent phase from missile launch to parachute deployment, a horizontal range prediction model is used in real time based on the missile's current state data and environmental data to obtain the predicted horizontal range when the missile maintains its current glide ratio and speed and descends to the parachute deployment target altitude. The predicted horizontal range is compared with the target horizontal range value to obtain the horizontal range prediction error in real time. The target horizontal range value is the horizontal range between the missile's current position and the parachute deployment target position.
[0150] This step is specifically as follows:
[0151] Step S21: During the entire descent phase from projectile deployment to parachute opening, acquire the projectile's current state data and environmental data; the projectile's current state data includes the projectile's current position. Current trajectory inclination of the missile body Current velocity scalar of the projectile and the projectile's current velocity direction; the environmental data includes wind speed vectors. ; These represent the missile's current northward position, eastward position, and current altitude;
[0152] Step S22: Introduce the influence of wind speed and construct a comprehensive prediction model for horizontal flight range;
[0153] Based on energy conservation and the gliding approximation, the predicted horizontal range can be obtained: ;
[0154] in: This refers to the current moment, corresponding to the missile's current flight time. In this patent, the predicted end time specifically refers to the projectile's descent to the target parachute deployment altitude. At that moment.
[0155] In engineering implementation, to reduce computational complexity, it is approximated as: ; The equivalent glide ratio can be obtained from calibration data or real-time estimation.
[0156] To improve forecast accuracy, the influence of wind speed is introduced: ; ; Given the wind-induced drift vector, a comprehensive horizontal range prediction model based on formula (1) is established:
[0157] (1)
[0158] in: This is the predicted horizontal range. For equivalent glide ratio, , For lift, As resistance; The remaining height ; This is the unit vector in the direction of the projectile's current velocity. To allow the missile to fall to the target altitude where the parachute opens The predicted fall time. To ensure the parachute deployment action can be performed, the following must be met: conditions.
[0159] Step S23: Using the aforementioned horizontal range prediction model, the projectile's descent to the parachute deployment target altitude while maintaining its current glide ratio and speed under wind speed influence is obtained in real time. Horizontal range prediction value at time ;
[0160] Step S24, calculate the horizontal range target value. :
[0161] (2)
[0162] Step S25: Calculate the horizontal range prediction error. :
[0163] (3)
[0164] This step is now complete.
[0165] This horizontal range prediction error It is the core input for subsequent guidance laws and switching criteria.
[0166] Step S3, Mid-course Dive Guidance Phase:
[0167] After being released from the launch point, the projectile first enters the mid-course dive guidance phase. The control objective of this phase is to guide the projectile toward the parachute-opening target position while maintaining sufficient potential energy, and to guide the projectile into the pull-up zone. During the mid-course dive guidance phase, the acceleration requirement command for guiding the projectile toward the parachute-opening target position is calculated in real time using the mid-course dive guidance law, and this acceleration requirement command is converted into a projectile attitude adjustment command, thereby achieving real-time adjustment of the projectile's attitude.
[0168] Step S31, the mid-course dive guidance law includes a horizontal channel guidance law and a vertical channel guidance law;
[0169] Step S32: Using the horizontal channel guidance law, eliminate the horizontal line-of-sight rotation deviation of the projectile's current position relative to the parachute-deployed target position, and calculate the lateral acceleration requirement command. ;
[0170] Step S321, Definition and decomposition of the line of sight angle:
[0171] Define the current position of the projectile. Relative to the target position of parachute opening line-of-sight vector :
[0172] (4)
[0173] Step S322: To achieve horizontal guidance, a horizontal line-of-sight angle is introduced. (Azimuth):
[0174] (5)
[0175] Define the rate of change of the horizontal line of sight angle Reflects the angular velocity of rotation of the horizontal line of sight:
[0176] (6)
[0177] in: , which is the horizontal distance from the current position of the projectile to the parachute deployment target position; and These represent the northward and eastward components of the projectile's velocity, respectively.
[0178] This indicates the speed of rotation of the line of sight on the horizontal plane, followed by... The proportional guidance algorithm indicates the speed of rotation of the line of sight in the vertical plane. It generates appropriate acceleration requirements, also known as overload requirements, to make the two line-of-sight angular velocities approach zero, thereby ensuring that the projectile meets the parachute-deployed target position.
[0179] Step S323, Guidance Law Design: Decompose into horizontal and vertical channels; construct the horizontal channel guidance law and calculate the lateral acceleration requirement command. ;
[0180] (7)
[0181] in: The command is for lateral acceleration, and its direction is perpendicular to the projection of the projectile's velocity vector onto the horizontal plane. The horizontal navigation ratio is a dimensionless constant, typically taken as 3 to 5. The horizontal velocity component;
[0182] Step S33: Using the vertical channel guidance law, eliminate the rotational deviation of the projectile's current position relative to the parachute-opening target position in the vertical line of sight, and simultaneously correct the predicted parachute opening height error to calculate the normal acceleration requirement command. ;
[0183] Step S331: To achieve vertical guidance, a vertical line-of-sight angle is introduced. (Elevation angle):
[0184] (8)
[0185] Define the rate of change of the vertical line of sight angle Reflects the angular velocity of rotation perpendicular to the line of sight:
[0186] (9)
[0187] in: The derivative of the horizontal distance from the current position of the projectile to the target position after parachute deployment; The derivative of the projectile's current height;
[0188] (10)
[0189] Step S332: Construct the vertical channel guidance law to eliminate the rotation of the projectile's current position relative to the parachute-opening target position in the vertical line of sight, and correct the predicted parachute opening height error. That is, it is necessary to control the altitude and energy, and then calculate the normal acceleration requirement command. ;
[0190] (11)
[0191] in: This is a command for normal acceleration, with the direction perpendicular to the projectile's velocity vector and pointing upwards; The vertical navigation ratio is dimensionless and is typically taken as 3 to 5. This is the height error correction factor, a positive constant. To predict the parachute opening height error, it is defined as:
[0192] (12)
[0193] in: For the missile body to reach the horizontal position of the parachute-deployed target at the current glide ratio The predicted height of the projectile, i.e., the predicted parachute deployment height, is expressed as:
[0194] (13)
[0195] when When the energy is greater than 0, the projectile has excess energy and needs to increase its dive; when When the energy level is less than 0, the projectile's energy is insufficient, requiring a reduction in dive or even a nose-up.
[0196] Step S34, lateral acceleration demand command output by the guidance law. and normal acceleration demand command
[0197] The servo motor cannot be driven directly; the lateral acceleration requirement command needs to be sent separately. and normal acceleration demand command Converted to roll channel rudder deflection command and pitch channel rudder deflection commands This allows for real-time adjustment of the projectile's roll and pitch attitudes, enabling the projectile to approach the parachute deployment target position.
[0198] Step S341, according to the lateral acceleration demand command Generate the desired roll angle :
[0199] By rolling, the main lifting surface of the projectile is aligned with the direction of the required lateral acceleration, and then the lateral force is generated by the normal acceleration. Therefore:
[0200] (14)
[0201] in: It is the acceleration due to gravity; This is the current pitch angle of the missile body, due to the mid-course dive guidance phase. The changes are minor and can be approximated. Therefore, we obtain formula (15):
[0202] (15)
[0203] Step S342, according to the normal acceleration requirement command Generate desired pitch angle :
[0204] Since normal acceleration is mainly generated by lift, therefore:
[0205] (16)
[0206] in: For the mass of the projectile; The inclination angle of the missile's current trajectory; due to lift Lift coefficient within a small angle of attack range The required angle of attack is obtained by inverse solving. :
[0207] (17)
[0208] in: air density; For the projectile's velocity scalar; This is the aerodynamic reference area; The lift coefficient at zero angle of attack is a constant. The slope of the lift line; For the current angle of attack, ; , , These are all aerodynamic parameters, which can be obtained by looking up tables.
[0209] Then the expected pitch angle for:
[0210] (18)
[0211] Step S343: Calculate the aileron deflection angle of the roll path respectively. Elevator deflection in the pitch channel :
[0212] (19)
[0213] (20)
[0214] in: This is the current roll angle of the projectile; The desired roll rate is usually set to zero to avoid overshoot; This represents the projectile's current roll angular velocity. These are the roll channel ratio and the differential gain, respectively. This is the current pitch angle of the projectile; The current pitch velocity of the projectile; To achieve the desired pitch rate, it is usually set to zero to avoid overshoot; and These are the pitch channel ratio and differential gain, respectively. This is a feedforward term used to counteract the gravitational tilting torque. The expression is:
[0215] (twenty one)
[0216] This step is now complete.
[0217] Step S4: During the mid-course dive guidance phase, it is determined in real time whether the pull-up switching judgment condition is met; if not, step S3 is continued; if it is met, the projectile enters the pull-up phase and step S5 is executed.
[0218] To ensure the smooth completion of the pull-up phase, mode switching must be performed at an appropriate time. The pull-up switching determination condition is as follows:
[0219] Step S41: Determine if the remaining height requirement is met. Judgment conditions:
[0220] (twenty two)
[0221] in: The pull-up reserve height, a normal value, represents the maximum permissible remaining height for triggering the switch from the mid-dive guidance phase to the pull-up phase. The purpose of setting this parameter is to ensure that the attitude leveling maneuver can be completed within the remaining height, avoiding insufficient pull-up due to a late switch. In this embodiment, the value is 70 m.
[0222] If the condition is not met, the conclusion that the switchover condition is not met is directly drawn; if the condition is met, step S42 is executed.
[0223] Step S42, Comprehensive performance index determination mechanism:
[0224] Define the cost function :
[0225] (twenty three)
[0226] in: These are the weighting factors for the horizontal range prediction error term, used to adjust the horizontal range prediction error.
[0227] In the cost function The weights in The larger the value, the more stringent the system's requirements for horizontal accuracy. The weighting factor for the remaining height item is used to adjust the remaining height. In the cost function The weights in The larger the value, the more sensitive the system is to the remaining height. The weighting coefficients for the trajectory inclination term are used to adjust the current trajectory inclination of the missile. In the cost function The weights in The larger the size, the more stringent the system's requirements for attitude smoothness.
[0228] Judgment cost function Does it satisfy formula (24)?
[0229] (twenty four)
[0230] in: The switching cost threshold is a normal number that represents the maximum combined cost allowed to switch from the mid-course dive guidance phase to the pull-up phase.
[0231] If formula (24) is satisfied, it is considered that the projectile has simultaneously met the requirements of horizontal accuracy, remaining height and attitude smoothness, and the conclusion is that the pull-up switching judgment condition is met; if not, the conclusion is that the pull-up switching judgment condition is not met.
[0232] In step S5, during the pull-up phase, an attitude leveling control law is used to adjust the projectile's attitude in real time, so that the projectile smoothly transitions from a dive state to a near-horizontal state and continues to maintain a near-horizontal state until the preset parachute opening judgment is met, triggering parachute opening.
[0233] In step S5, attitude leveling control:
[0234] During the pull-up phase, an attitude balancing control law is employed to adjust the projectile's attitude in real time, ensuring a smooth transition from a dive to a near-horizontal state and meeting attitude and angular velocity constraints at the moment of parachute deployment. This attitude balancing control law includes a pitch channel control law and a roll channel control law; specifically:
[0235] Step S51, set the attitude leveling control target:
[0236] (25)
[0237] Specifically, the current trajectory inclination angle of the missile body Approaching 0, and the projectile's current pitch angle Approaching the desired pitch angle This ensures that the projectile tilts slightly during parachute deployment, which facilitates smooth parachute deployment and reduces impact. Furthermore, the projectile's current roll angle... Approaching 0; simultaneously requiring the projectile's current pitch angular velocity. and the projectile's current roll angular velocity Converging to near zero prevents the parachute lines from becoming tangled due to excessive angular velocity at the moment of opening;
[0238] Step S52, initiate trajectory planning:
[0239] To ensure a smooth pull-up process and continuous control input, an ideal trajectory for varying the inclination angle is pre-designed to guarantee smooth changes in aerodynamic loads during the pull-up and avoid stall or oscillation caused by sudden pull-ups.
[0240] (26)
[0241] in: The inclination angle of the missile's current trajectory; The desired rate of change of track inclination; The convergence rate coefficient of the trajectory inclination angle determines the current trajectory inclination angle of the missile. The rate of convergence to zero is determined by the coefficient. The larger the coefficient, the faster the pull-up process and the higher the rate of exponential decay of the track inclination angle; the smaller the coefficient, the smoother the pull-up process.
[0242] Step S53: Employ the pitch channel control law to adjust the rate of change of the missile's actual trajectory tilt angle. Tracking the desired rate of change of track inclination From this, the desired lift, desired angle of attack, and desired pitch angle are deduced, and finally the elevator deflection angle is calculated using the pitch angle tracking control law.
[0243] Step S531: Calculate the rate of change of the actual trajectory angle of the missile body. :
[0244] (27)
[0245] in: For lift; For the mass of the projectile; It is the acceleration due to gravity; For the projectile's velocity scalar; The inclination angle of the missile's current trajectory;
[0246] Step S532, let = Calculate the expected lift. :
[0247] (28)
[0248] Step S533, based on the lift model, from the desired lift... Inverse solution to obtain the expected angle of attack :
[0249] The lift model is as follows:
[0250] (29)
[0251] in: air density; This is the aerodynamic reference area; The current velocity of the projectile is a scalar; the lift coefficient is... Linearization within the small to medium angle of attack range ; The lift coefficient at zero angle of attack is a constant. The slope of the lift line; Define the current angle of attack. Therefore, the expected angle of attack can be derived from this. :
[0252] (30)
[0253] Step S534, according to the desired angle of attack The desired pitch angle is calculated. :
[0254] (31)
[0255] Step S535: Obtain the elevator deflection angle according to the pitch angle tracking control law. :
[0256] (32)
[0257] in: This is the current pitch angle of the projectile; The current pitch velocity of the projectile; To achieve the desired pitch rate, it is usually set to zero to avoid overshoot; , These are the pitch channel ratio and differential gain, respectively. The feedforward term is used to counteract the gravitational pitching torque, and its expression is:
[0258] (33)
[0259] Step S54: Using the roll channel control law, calculate the aileron deflection angle required to keep the missile body from rolling during the pull-up process;
[0260] As one implementation method, during the pull-up process, the projectile must remain stationary to prevent the parachute lines from tangling during deployment. The roll channel control law is as follows:
[0261] (34)
[0262] in: For aileron deflection; This is the current roll angle of the projectile; This represents the projectile's current roll angular velocity. , These are the roll-off channel ratio and the differential gain, respectively.
[0263] In step S55, the elevator and aileron deflection angles are used to adjust the missile's attitude in real time, so that the missile's pitch and roll angles continue to approach zero throughout the pull-up phase until the parachute is deployed.
[0264] In step S5, the parachute opening determination is a multi-condition fusion parachute opening determination, including:
[0265] Condition 1: Height condition: ;
[0266] Condition 2: Attitude Conditions: ;
[0267] Condition 3: Dynamic Constraints ;
[0268] Condition 4: Redundancy triggering mechanism: , ;
[0269] in: This is the current height of the projectile; Target altitude for parachute deployment; This is the current pitch angle of the projectile; This is the current roll angle of the projectile; The current pitch velocity of the projectile; This represents the projectile's current roll angular velocity. , , and These are the maximum values of the projectile's pitch angle, roll angle, pitch velocity, and roll velocity, respectively. The axial acceleration of the projectile is used in this embodiment as an auxiliary criterion for determining whether the parachute deployment action triggers a parachute impact or whether the projectile enters a specific dynamic state. The threshold for acceleration mutation is a preset positive constant. If the threshold is exceeded, the system is considered to be in a high-risk state, and the parachute will be forcibly deployed.
[0270] When conditions 1, 2, and 3 are met simultaneously, the parachute is deployed; when condition 4 is met, the parachute is forcibly deployed.
[0271] The parachute opening determination is expressed as a comprehensive logic:
[0272] (35)
[0273] in: This indicates that the parachute has been deployed; Represents logical AND; Represents logical OR.
[0274] The unpowered projectile dive-pull combined guidance method for parachute deployment accuracy provided by this invention achieves its objective through the following coupling relationship:
[0275] 1. Utilize a comprehensive horizontal range prediction model to predict the horizontal range of the missile body when it falls to the target altitude for parachute deployment, which can also be referred to as the predicted parachute deployment point position; 2. Simultaneously adjust horizontal and altitude errors through guidance laws; 3. Ensure entry into the controllable pull-up range through a switching mechanism; 4. Ensure parachute deployment stability through attitude control; 5. Improve system reliability through multi-condition judgment.
[0276] Final Implementation:
[0277]
[0278] : Safe parachute pitch angle, the preset absolute value of the maximum pitch angle that allows the parachute to deploy safely. In this example, it is preset to 5°.
[0279] Parachute deployment is completed at the parachute deployment target position directly above the projectile target position, while satisfying attitude constraints.
[0280] Compared with the prior art, the present invention has the following beneficial effects:
[0281] (1) The pitch angle of the projectile can be controlled within ±5 degrees horizontally at the moment of parachute opening, and the roll rate is less than 10° / s, which greatly reduces the failure rate of parachute opening.
[0282] (2) The horizontal position error converges to within a radius of 15 meters at the parachute opening height, and the final landing point dispersion can be reduced by more than 30% compared with the traditional method;
[0283] (3) By predicting the switching logic, the pull-up process is smooth, avoiding stalling or oscillation caused by sudden pull-up at the end;
[0284] (4) The algorithm is implemented entirely in software, without increasing the additional hardware cost, and can be directly embedded into the existing flight control computer.
[0285] The method of the present invention will be further described in detail below with reference to a specific configuration of a small, unpowered guided missile. This embodiment is used to illustrate the specific application of the present invention in small-sized, high-speed, short-wingspan unpowered missiles, but does not constitute a limitation on the scope of protection of the present invention.
[0286] The projectile in this embodiment is a typical low aspect ratio gliding aerodynamic layout, characterized by small size, low drag, strong dive capability, and fast terminal response, making it particularly suitable for high-altitude rapid deployment scenarios by UAVs.
[0287] 1. Projectile structure and overall parameters:
[0288] The unpowered guided missile in this embodiment mainly consists of a missile body section, an X-shaped tail rudder, a short-wing glide surface, an onboard flight control system, and a parachute deployment mechanism.
[0289] (1) Projectile dimensions
[0290] The overall parameters of the projectile are as follows:
[0291] Table 1: Overall Parameters of the Projectile
[0292]
[0293] Due to the large aspect ratio of the projectile:
[0294]
[0295] : Projectile diameter.
[0296] Therefore, it has low drag and strong diving stability.
[0297] (2) Aerodynamic layout
[0298] The tail section adopts an X-shaped tail rudder structure, with four tail rudders evenly distributed at 90°.
[0299] This layout features strong pitch / yaw coupling capability, high roll damping, high control efficiency under small size conditions, and compact structure.
[0300] The stub wing is installed in the middle and rear section, and its main functions are to provide limited gliding capability, provide lift during the pull-up phase, and maintain a certain range.
[0301] 2. Estimation of aerodynamic parameters
[0302] Within the typical flight angle of attack range of 4° to 8°, wind tunnel calibration and simulation yielded the following results:
[0303] Table 2: Aerodynamic Parameters
[0304]
[0305] therefore:
[0306] Compared to large glide missiles, this configuration has a lower lift-to-drag ratio, but a faster dive response, making it more suitable for rapid parachute deployment.
[0307] 3. Placement conditions
[0308] The drone uses a fixed-wing platform, and the deployment conditions are as follows:
[0309] Table 3: Delivery Parameters
[0310]
[0311] Table 4: Environmental Parameters
[0312]
[0313] 4. Post-deployment status analysis
[0314] After the missile detaches from the pylon, due to its small wing area, high initial velocity, and slender body, it quickly enters a stable dive state.
[0315] Initial state: Initial velocity scalar of the projectile Initial trajectory inclination of the missile body ;
[0316] Remaining height: ;
[0317] (1) Initial range prediction
[0318] Based on the rise-to-drag ratio: ;get ;
[0319] This indicates that the current energy is sufficient to fly past the target location where the parachute has deployed. Therefore, the system enters an active dive-and-energy-consumption mode.
[0320] (2) Wind drift estimation
[0321] Under dive control, the actual average descent rate of this missile is approximately 45 m / s.
[0322] Initial stage: ;
[0323] Estimated fall time: ;
[0324] Wind drift: ;
[0325] Therefore, the dive angle must be increased to reduce flight time and wind drift.
[0326] 5. Mid-course dive guidance process
[0327] The system employs a height-corrected proportional guidance law as the mid-course dive guidance law. According to principle formula (11), the normal acceleration command for the vertical channel... It consists of two parts: eliminating the line-of-sight rotation term and correcting the predicted height error term. =3.8 is the vertical navigation ratio. =0.028 is the height error correction coefficient.
[0328] (1) First stage: rapid energy-consuming dive
[0329] 0-3 seconds after deployment: The system actively lowers the trajectory of the projectile.
[0330] Track angle changes:
[0331] Speed increases:
[0332] Altitude descent:
[0333] During this stage: drag increases rapidly, flight time is significantly shortened, and wind drift decreases rapidly.
[0334] Recalculate:
[0335] but:
[0336] We are now close to the target distance.
[0337] (2) Second stage: Error convergence
[0338] Approximately 7 seconds into flight, the missile's parameters are shown in Table 5:
[0339] Table 5: Projectile Parameters
[0340]
[0341] Remaining height:
[0342] Predicted range:
[0343] Target distance:
[0344] therefore:
[0345] This indicates that the current energy level is slightly low, and the system will automatically reduce the dive angle.
[0346] (3) Third stage: Enter the pull-up window
[0347] After approximately 10 seconds of flight, the missile's parameters are shown in Table 6:
[0348] Table 6: Projectile Parameters
[0349]
[0350] at this time:
[0351] Predicted range:
[0352] Target distance:
[0353] therefore:
[0354] satisfy:
[0355] at the same time:
[0356] The system triggered a switchover.
[0357] 6. Pull-up control process
[0358] After entering the pull-up phase, the control target becomes: ;
[0359] (1) Pitch control
[0360] Control Law:
[0361] parameter: ; ;
[0362] (2) Feedforward compensation
[0363] Because of its high aspect ratio and strong static stability, the projectile requires significant feedforward compensation when pulled up.
[0364] calculate: ;
[0365] Substitute: ; ; ; ;get .
[0366] Note: A significant rudder deflection is required to pull up.
[0367] (3) Pulling up the dynamic process
[0368] 0 to 0.4 seconds:
[0369] 0.4 to 1.2 seconds:
[0370] The track angle gradually approaches:
[0371] Maximum pitch angular velocity:
[0372] Throughout the process, there was no obvious oscillation or stall, and the roll angle remained less than:
[0373] 7. Parachute Opening Detection and Triggering
[0374] When the projectile's altitude drops to approximately 101.5m, the system makes the final parachute deployment decision based on the multi-condition fusion judgment logic (Formula 35) in the principle. At this time, the state variables are detected as follows:
[0375] Height requirement: h = 99m ≤ = 100m;
[0376] Attitude conditions: = 5°, = 5°;
[0377] Dynamic constraints: = , =
[0378] Redundant triggering conditions: The projectile does not oscillate violently, and the axial acceleration does not exceed the threshold, so it is not triggered.
[0379] Since conditions 1 (altitude), 2 (attitude), and 3 (dynamic constraints) are satisfied simultaneously, the system determines that the parachute opening condition is met and triggers the parachute opening based on the comprehensive logic of the principle formula (35).
[0380] 8. Final Result
[0381] The final test results are as follows:
[0382] Table 7: Test Results
[0383]
[0384] Compared to traditional single-altitude triggering methods, the landing point dispersion is reduced by approximately 60%, parachute deployment stability is significantly improved, and the impact of wind disturbance is significantly reduced. This demonstrates that the present invention can effectively achieve reliable parachute deployment at a specified altitude above the target point with a stable attitude.
[0385] This invention provides a combined dive-pull guidance method for unpowered munitions with improved parachute deployment accuracy. The steps can be summarized as follows:
[0386] Step 1: Obtain the target parachute deployment position and environmental wind estimation. Based on the target parachute deployment altitude constraint, execute mid-course energy dive guidance to converge the horizontal range prediction error. The mid-course energy dive guidance employs a proportional guidance law with terminal altitude correction, predicting the horizontal position at parachute deployment altitude through online aerodynamic parameter identification. Step 2: Real-time determination of whether the pull-up switching criteria are met. Step 3: After the switching criteria are met, control the missile body to transition from dive to attitude leveling. Through combined control of the pitch and roll channels, the missile body reaches a set near-horizontal attitude before the target parachute deployment altitude. The attitude leveling phase employs a feedforward + PD pitch angle control law. The feedforward amount is calculated based on the airspeed and gravity components at the start of leveling to counteract the gravitational pitching moment. Step 4: Trigger parachute deployment based on the multi-source information fusion judgment logic, lock the servos, and release the parachute.
[0387] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A combined dive-pull guidance method for unpowered munitions with high parachute deployment accuracy, characterized in that: Includes the following steps: Step S1: Preset the target position of the projectile; determine the target position for parachute deployment based on the target position of the projectile; the target position for parachute deployment includes the horizontal position and the height of the target for parachute deployment. Step S2: During the entire descent phase from missile launch to parachute deployment, based on the missile's current state data and environmental data, a horizontal range prediction model is used to obtain the predicted horizontal range when the missile maintains its current glide ratio and speed as it descends to the parachute deployment target altitude. The predicted horizontal range is compared with the target horizontal range value to obtain the horizontal range prediction error in real time. The target horizontal range value is the horizontal range between the missile's current position and the parachute deployment target position. Step S3: After the projectile is released from the launch point, it first enters the mid-course dive guidance phase. In the mid-course dive guidance phase, the mid-course dive guidance law is used in real time to calculate the acceleration requirement command that makes the projectile approach the parachute target position, and the acceleration requirement command is converted into the projectile attitude adjustment command, thereby realizing the real-time adjustment of the projectile attitude. Step S4: During the mid-course dive guidance phase, it is determined in real time whether the pull-up switching judgment condition is met; if not, step S3 is continued; if it is met, the projectile enters the pull-up phase and step S5 is executed. In step S5, during the pull-up phase, an attitude leveling control law is used to adjust the projectile's attitude in real time, so that the projectile smoothly transitions from a dive state to a near-horizontal state and continues to maintain a near-horizontal state until the preset parachute opening judgment is met, triggering parachute opening.
2. The unpowered missile dive-pull combined guidance method for parachute deployment accuracy as described in claim 1, characterized in that, Step S1 includes: Step S11: Preset the target position of the projectile in the inertial coordinate system. , These represent the northward, eastward, and altitude positions of the missile target. Step S12, based on the target position of the projectile Determine the target location for parachute deployment by setting an altitude position directly above it. , The target altitude for parachute deployment.
3. The unpowered missile dive-pull combined guidance method for parachute deployment accuracy as described in claim 2, characterized in that, Step S2 includes: Step S21: During the entire descent phase from projectile deployment to parachute opening, acquire the projectile's current state data and environmental data; the projectile's current state data includes the projectile's current position. Current trajectory inclination of the missile body Current velocity scalar of the projectile and the projectile's current velocity direction; the environmental data includes wind speed vectors. ; These represent the missile's current northward position, eastward position, and current altitude; Step S22: Introduce the influence of wind speed and construct a comprehensive horizontal range prediction model: （1） in: This is the predicted horizontal range. For equivalent glide ratio, , For lift, As resistance; The remaining height ; This is the unit vector in the direction of the projectile's current velocity. For the missile to fall to the target altitude where the parachute opens The predicted fall time ; Step S23: Using the aforementioned horizontal range prediction model, the projectile's descent to the parachute deployment target altitude while maintaining its current glide ratio and speed under wind speed influence is obtained in real time. Horizontal range prediction value at time ; Step S24, calculate the horizontal range target value. : （2） Step S25: Calculate the horizontal range prediction error. : （3） This step is now complete.
4. The unpowered missile dive-pull combined guidance method for parachute deployment accuracy as described in claim 3, characterized in that, Step S3 includes: Step S31, the mid-course dive guidance law includes a horizontal channel guidance law and a vertical channel guidance law; Step S32: Using the horizontal channel guidance law, eliminate the horizontal line-of-sight rotation deviation of the projectile's current position relative to the parachute-deployed target position, and calculate the lateral acceleration requirement command. ; Step S33: Using the vertical channel guidance law, the rotational deviation of the projectile's current position relative to the parachute-opening target position in the vertical line of sight is eliminated, and the predicted parachute opening height error is corrected, thus obtaining the normal acceleration requirement command. ; Step S34, respectively send the lateral acceleration demand commands and normal acceleration demand command Converted to roll channel rudder deflection command and pitch channel rudder deflection commands This allows for real-time adjustment of the projectile's roll and pitch attitudes, enabling the projectile to approach the parachute deployment target position.
5. The unpowered missile dive-pull combined guidance method for parachute deployment accuracy as described in claim 4, characterized in that, Step S32 includes: Step S321, define the current position of the projectile. Relative to the target position of parachute opening line-of-sight vector : （4） Step S322: To achieve horizontal guidance, a horizontal line-of-sight angle is introduced. : （5） Define the rate of change of the horizontal line of sight angle Reflects the angular velocity of rotation of the horizontal line of sight: （6） in: , is the horizontal distance from the current position of the projectile to the target position where the parachute opens; and These represent the northward and eastward components of the projectile's velocity, respectively. Step S323: Construct the horizontal channel guidance law and calculate the lateral acceleration demand command. ; （7） in: The command is for lateral acceleration, and its direction is perpendicular to the projection of the projectile's velocity vector onto the horizontal plane. The horizontal navigation ratio is a dimensionless constant. Step S33 includes: Step S331: To achieve vertical guidance, a vertical line-of-sight angle is introduced. : （8） Define the rate of change of the vertical line of sight angle Reflects the angular velocity of rotation perpendicular to the line of sight: （9） in: The derivative of the horizontal distance from the current position of the projectile to the target position after parachute deployment; The derivative of the projectile's current height; （10） Step S332: Construct the vertical channel guidance law to eliminate the rotation of the projectile's current position relative to the parachute-opening target position in the vertical line of sight, while correcting the predicted parachute opening height error, and then calculate the normal acceleration requirement command. ; （11） in: This is a command for normal acceleration, with the direction perpendicular to the projectile's velocity vector and pointing upwards; The vertical navigation ratio is dimensionless. This is the height error correction factor, a positive constant. To predict the parachute opening height error, it is defined as: （12） in: For the missile body to reach the horizontal position of the parachute-deployed target at the current glide ratio The predicted height of the projectile, i.e., the predicted parachute deployment height, is expressed as: （13） when When the energy is greater than 0, the projectile has excess energy and needs to increase its dive; when When the energy level is less than 0, the projectile's energy is insufficient, requiring a reduction in dive or even a nose-up.
6. The unpowered missile dive-pull combined guidance method for parachute deployment accuracy as described in claim 4, characterized in that, Step S34 includes: Step S341, according to the lateral acceleration demand command Generate the desired roll angle : By rolling, the projectile's main lifting surface is aligned with the direction of the required lateral acceleration, and then the lateral force is generated by the normal acceleration. Therefore: （14） in: It is the acceleration due to gravity; This is the current pitch angle of the missile body, due to the mid-course dive guidance phase. The changes are minor and approximate. Therefore, we obtain formula (15): （15） Step S342, according to the normal acceleration requirement command Generate desired pitch angle : Since normal acceleration is mainly generated by lift, therefore: （16） in: For the mass of the projectile; This is the inclination angle of the missile's current trajectory; due to lift... Lift coefficient within a small angle of attack range The required angle of attack can be determined by reverse engineering. : （17） in: air density; For the projectile's velocity scalar; This is the aerodynamic reference area; The lift coefficient at zero angle of attack is a constant. The slope of the lift line; For the current angle of attack, ; Then the expected pitch angle for: （18） Step S343: Calculate the aileron deflection angle of the roll path respectively. Elevator deflection in the pitch channel : （19） （20） in: This is the current roll angle of the projectile; The desired roll rate is usually set to zero to avoid overshoot; This represents the projectile's current roll angular velocity. These are the roll channel ratio and the differential gain, respectively. This is the current pitch angle of the projectile; The current pitch velocity of the projectile; To achieve the desired pitch rate, it is usually set to zero to avoid overshoot; and These are the pitch channel ratio and differential gain, respectively. This is a feedforward term used to counteract the gravitational pitching torque. The expression is: （21） This step is now complete.
7. The unpowered missile dive-pull combined guidance method for parachute deployment accuracy as described in claim 1, characterized in that, In step S4, the condition for determining the pull-up switching is: Step S41: Determine if the remaining height requirement is met. Judgment conditions: （22） in: The height reserved for pull-up is a normal number, representing the maximum allowable remaining height for triggering the switch from the mid-course dive guidance phase to the pull-up phase; If the condition is not met, the conclusion that the switchover condition is not met is directly drawn; if the condition is met, step S42 is executed. Step S42, Comprehensive performance index determination mechanism: Define the cost function : （23） in: The weighting coefficients for the horizontal range prediction error term; This refers to the horizontal range prediction error. This is the weighting factor for the remaining height term; The weighting coefficient for the track inclination term; The inclination angle of the missile's current trajectory; Judgment cost function Does it satisfy formula (24)? （24） in: The switching cost threshold is a normal number that represents the maximum combined cost allowed to switch from the mid-course dive guidance phase to the pull-up phase. If formula (24) is satisfied, it is considered that the projectile has simultaneously met the requirements of horizontal accuracy, remaining height and attitude smoothness, and the conclusion is that the pull-up switching judgment condition is met; if not, the conclusion is that the pull-up switching judgment condition is not met.
8. The unpowered missile dive-pull combined guidance method for parachute deployment accuracy as described in claim 1, characterized in that, In step S5, during the pull-up phase, an attitude leveling control law is used to adjust the projectile's attitude in real time, allowing the projectile to smoothly transition from a dive to a near-horizontal state, ensuring that the attitude and angular velocity constraints are met at the moment of parachute deployment. The attitude leveling control law includes a pitch channel control law and a roll channel control law; specifically: Step S51, set the attitude leveling control target: （25） Specifically, the current trajectory inclination angle of the missile body Approaching 0, and the projectile's current pitch angle Approaching the desired pitch angle This ensures that the projectile tilts slightly during parachute deployment, which facilitates smooth parachute deployment and reduces impact. Furthermore, the projectile's current roll angle... Approaching 0; simultaneously requiring the projectile's current pitch angular velocity. and the projectile's current roll angular velocity Converging to near zero prevents the parachute lines from becoming tangled due to excessive angular velocity at the moment of opening; Step S52, initiate trajectory planning: To ensure a smooth pull-up process and continuous control input, an ideal trajectory for varying the inclination angle is pre-designed to guarantee smooth changes in aerodynamic loads during the pull-up and avoid stall or oscillation caused by sudden pull-ups. （26） in: The inclination angle of the missile's current trajectory; The desired rate of change of track inclination; The convergence rate coefficient of the trajectory inclination angle determines the current trajectory inclination angle of the missile. The rate at which the trajectory converges to zero is determined by the coefficient. A larger coefficient indicates a faster pull-up process and a higher rate of exponential decay of the trajectory inclination angle; a smaller coefficient indicates a smoother pull-up process. Step S53: Employ the pitch channel control law to adjust the rate of change of the missile's actual trajectory tilt angle. Tracking the desired rate of change of track inclination From this, the desired lift, desired angle of attack, and desired pitch angle are deduced, and finally the elevator deflection angle is calculated using the pitch angle tracking control law. Step S54: Using the roll channel control law, calculate the aileron deflection angle required to keep the missile body from rolling during the pull-up process; In step S55, the elevator deflection angle and aileron deflection angle are used to adjust the missile attitude in real time, so that the missile pitch angle and roll angle continuously approach zero throughout the pull-up phase.
9. The unpowered missile dive-pull combined guidance method for parachute deployment accuracy as described in claim 8, characterized in that, Step S53 includes: Step S531: Calculate the rate of change of the actual trajectory angle of the missile body. : （27） in: For lift; For the mass of the projectile; It is the acceleration due to gravity; For the projectile's velocity scalar; The inclination angle of the missile's current trajectory; Step S532, let = Calculate the expected lift. : （28） Step S533, based on the lift model, from the desired lift... Inverse solution to obtain the expected angle of attack : The lift model is as follows: （29） in: air density; This is the aerodynamic reference area; The current velocity of the projectile is a scalar; the lift coefficient is... Linearization within the small to medium angle of attack range ; The lift coefficient at zero angle of attack is a constant. The slope of the lift line; Define the current angle of attack. Therefore, the expected angle of attack can be derived from this. : （30） Step S534, based on the desired angle of attack The desired pitch angle is calculated. : （31） Step S535: Obtain the elevator deflection angle according to the pitch angle tracking control law. : （32） in: This is the current pitch angle of the projectile; The current pitch velocity of the projectile; To achieve the desired pitch rate, it is usually set to zero to avoid overshoot; , These are the pitch channel ratio and differential gain, respectively. The feedforward term is used to counteract the gravitational pitching torque, and its expression is: （33） In step S54, the roll channel control law is: （34） in: For aileron deflection angle; This is the current roll angle of the projectile; This represents the projectile's current roll angular velocity. , These are the roll-off channel ratio and the differential gain, respectively.
10. The unpowered missile dive-pull combined guidance method for parachute deployment accuracy as described in claim 1, characterized in that, The parachute deployment determination is a multi-condition fusion parachute deployment determination, including: Condition 1: Height condition: ; Condition 2: Attitude Conditions: ; Condition 3: Dynamic Constraints ; Condition 4: Redundancy triggering mechanism: , ; in: This is the current height of the projectile; Target altitude for parachute deployment; This is the current pitch angle of the projectile; This is the current roll angle of the projectile; The current pitch velocity of the projectile; This represents the projectile's current roll angular velocity. , , and These are the maximum values of the projectile's pitch angle, roll angle, pitch velocity, and roll velocity, respectively. The axial acceleration of the projectile. This is a preset positive constant, representing the threshold for acceleration abrupt changes. When conditions 1, 2, and 3 are met simultaneously, the parachute is deployed; when condition 4 is met, the parachute is forcibly deployed. The umbrella opening determination is expressed as a comprehensive logic: （35） in: This indicates that the parachute has been deployed; Represents logical AND; Represents logical OR.