A method of trajectory design for a program turn

Abstract

The application relates to a high-efficiency program turning trajectory design method, which comprises the following steps: arranging two turning engines on a carrier rocket to sequentially provide lateral thrust; designing a program angle mode in a program turning section and setting a handover point; before the handover point, the program angle mode is a pitch angle mode; after the handover point, the program angle mode is converted from the pitch angle mode to an attack angle mode. The application provides a high-efficiency program turning trajectory design method, two turning engines are arranged on a carrier rocket to provide a control impulse moment, the two turning engines work in relay, sequentially provide lateral thrust for a program turning section, and assist in completing program turning; a program angle mode with a handover point is designed, the working mode of the turning engine is accurately matched, various constraints such as rocket turning overload, turning angular velocity, attack angle change rate and the like are met, the turning is smooth throughout, and the control quality is effectively improved. The method reduces the design pressure of a control system and guarantees the attitude control precision of the carrier rocket.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of launch vehicle trajectory design, in particular to a trajectory design method for efficient program turn. BACKGROUND

[0002] In addition to the sounding task, the launch vehicle needs to complete the program turn in the first flight segment to achieve the purpose of rapid turn, so that the launch vehicle reaches the required motion state of the aircraft when it is shut down.

[0003] The first flight segment generally includes a vertical ascent segment and a first program turn segment. In the vertical ascent segment, the attack angle is zero, and the launch vehicle ascends vertically. If the time of the vertical ascent segment is too long, the gravitational loss of speed will be increased, and a larger normal force will be required due to the excessive speed during the turn. If the time of the vertical ascent segment is too short, the engine may not reach the rated operating state, or the speed may be too small to cause the control torque to be too small, thereby affecting the control performance. In the first program turn segment, the dynamic pressure is relatively large, and the interference torque is strong, making it difficult to overcome.

[0004] Therefore, when designing the program turn in the first flight segment, the strong interference torque and small control torque of the launch vehicle cause a large design pressure of the control system and low control accuracy. SUMMARY

[0005] Embodiments of the present application provide a trajectory design method for efficient program turn to solve the technical problems of related art, such as strong interference torque of the launch vehicle, small control torque, large design pressure of the control system, and low control accuracy.

[0006] Embodiments of the present application provide a trajectory design method for efficient program turn, which includes the following steps:

[0007] Two turn engines are arranged on the launch vehicle to provide lateral thrust in sequence;

[0008] A program angle mode is designed for the program turn segment, and a handover point is set;

[0009] Before the handover point, the program angle mode is a pitch angle mode;

[0010] After the handover point, the program angle mode is converted from the pitch angle mode to the attack angle mode.

[0011] In some embodiments, the program turn segment includes a vertical ascent segment, a uniform acceleration segment, a uniform deceleration segment, and an attack angle return-to-zero segment arranged in sequence; the uniform acceleration segment is a working period of the first turn engine, the uniform deceleration segment is a working period of the second turn engine, and the handover point is set at a handover time of the uniform deceleration segment and the attack angle return-to-zero segment.

[0012] In some embodiments, the program angle mode includes:

[0013] constructing a piecewise function according to the end time of each stage in the procedure turn segment;

[0014] The piecewise function is:

[0015]

[0016] wherein, is the pitch angle; t 1 is the end time of the vertical ascent segment; t 2 is the end time of the work of the first turn engine; t 3 is the end time of the work of the second turn engine; t 4 is the end time of the procedure turn / attack angle back to zero; is the ballistic inclination angle; is the flight attack angle; k is the angular acceleration of the procedure turn segment; a max , the turn coefficient a , t 0 is a constant term;

[0017] determining the end time of each stage in the procedure turn segment and the handover point parameters.

[0018] In some embodiments, determining the end time of the vertical ascent segment in the procedure turn segment t 1 includes:

[0019] obtaining the end time of the vertical ascent segment t 1 according to the take-off thrust-weight ratio of the launch vehicle;

[0020] The calculation formula is:

[0021]

[0022] wherein, F is the take-off thrust of the launch vehicle, G is the gravity received by the launch vehicle at take-off.

[0023] In some embodiments, determining the end time of the work of the first turn engine in the procedure turn segment t 2 includes:

[0024] setting the work period of the turn engine t ;

[0025] obtaining the angular acceleration of the procedure turn segment k ;

[0026] calculating the total impulse of the turn engine I 1;

[0027] The calculation formula is: ;

[0028] Wherein, M 气 is the engine working period in the turn t the inner pitch aerodynamic moment; L is the distance between the engine in the turn and the first-order mass center; J is the first-order mass center moment of inertia around the pitch direction;

[0029] based on the total impulse of the engine in the turn I 1. Obtain the parameters of the engine in the turn;

[0030] If the parameters of the engine in the turn do not meet the set requirements, modify the working period of the engine in the turn t ;

[0031] Repeat the above steps until the parameters of the engine in the turn meet the set requirements;

[0032] According to the working period of the engine in the turn t, calculate the end time t2 of the first engine in the turn;

[0033] The calculation formula is: .

[0034] In some embodiments, determining the end time t3 of the second engine in the turn in the program turn section comprises: t 3. comprising:

[0035] According to the working period of the engine in the turn t, calculate the end time t3 of the second engine in the turn;

[0036] The calculation formula is: .

[0037] In some embodiments, determining the handover point parameters comprises:

[0038] Based on the trajectory of the launch vehicle, obtain the handover time t 3 corresponding attack angle ;

[0039] Based on the handover time t 3 corresponding attack angle Obtain the attack angle change rate ;

[0040] The calculation formula of the attack angle change rate is:

[0041]

[0042] in, h This is the step size for calculating the ballistic integral.

[0043] In some embodiments, determining the time t4 at the end of the program turn / return to zero angle of attack in the program turning segment includes:

[0044] Set turning coefficient a The initial value is greater than 0;

[0045] According to the turning coefficient a Determine the constant term a max , t 0;

[0046] The calculation formula is:

[0047] ;

[0048] ;

[0049] ;

[0050] According to the constant term a max , a , t 0. Determine the time t4 when the program ends turning / angle of attack returns to zero;

[0051] The calculation formula is:

[0052] ;

[0053] Where δ is the absolute value of the angle of attack;

[0054] Determine if t4 is in the transonic range;

[0055] If t4 is in the transonic range, adjust the turning coefficient. a Repeat the above steps until t4 is no longer in the transonic band.

[0056] In some embodiments, the turning engine is two identical side-injection turning engines.

[0057] In some embodiments, the turning engines are arranged symmetrically on the launch vehicle.

[0058] The beneficial effects of the technical solution provided in this application include:

[0059] This application provides a ballistic design method for efficient programmed turns. Two turning engines are configured on the launch vehicle to provide control impulse torque. These two engines work in relay, sequentially providing lateral thrust to assist in completing the programmed turn. By designing a programmed angle mode with a handover point, the operating mode of the turning engines is precisely matched to meet various constraints such as rocket turning overload, turning rate, and rate of change of angle of attack. The turn is smooth throughout, effectively improving control quality. This method reduces the design burden on the control system, ensures the accuracy of launch vehicle attitude control, is practical, simple, and easy to implement in engineering, and improves the adaptability of solid-propellant launch vehicles to launch missions. Attached Figure Description

[0060] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0061] , This is a flowchart of a ballistic design method for efficient programmed turning in one embodiment of the present invention.

[0062] Figure 1 This is a schematic diagram of the pitch angle during a high-efficiency turn in one embodiment of the present invention.

[0063] Figure 2 This is a schematic diagram of the angle of attack during a high-efficiency turn in one embodiment of the present invention. Detailed Implementation

[0064] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0065] like Figure 3 As shown, Figure 1 This is a flowchart of a ballistic design method for efficient programmed turning in one embodiment of the present invention.

[0066] This application provides a ballistic trajectory design method for efficient programmed turning, which includes the following steps:

[0067] Step S1: Install two turning engines on the launch vehicle to provide lateral thrust in sequence;

[0068] Step S2, design a program angle mode for the program turn segment, and set a handover point;

[0069] Before the handover point, the program angle mode is a pitch angle mode;

[0070] After the handover point, the program angle mode is converted from the pitch angle mode to an attack angle mode.

[0071] The embodiment of the application provides a high-efficiency program turn trajectory design method, two turn engines are arranged on a carrier rocket to provide a control impulse moment, the two turn engines work in relay, and provide lateral thrust for a program turn segment in sequence to assist in completing the program turn; a program angle mode with a handover point is designed, the working mode of the turn engine is accurately matched, various constraints such as rocket turn overload, turn angular velocity, and attack angle change rate are met, the turn is smooth throughout, and the control quality is effectively improved. The method reduces the design pressure of a control system, guarantees the attitude control precision of the carrier rocket, is practical and simple, is easy to implement in engineering, and improves the adaptability of the solid carrier rocket to a launch task.

[0072] The following will be described in detail.

[0073] Step S1, two turn engines are arranged on the carrier rocket to provide lateral thrust in sequence.

[0074] In some embodiments, the turn engines are two identical side-jet turn engines,

[0075] In some embodiments, the turn engines are symmetrically arranged on the carrier rocket.

[0076] Through the above scheme, the installation and calculation of the turn engines are facilitated.

[0077] The two turn engines are arranged on the carrier rocket, and work to output forces of the same size and opposite directions in sequence, provide lateral thrust through short-time work, one provides program turn power, and the other slows down and brakes, and finally assists in realizing the program turn.

[0078] As shown in Figure 1 and Figure 2 , wherein, Figure 3 is a schematic diagram of a pitch angle in a high-efficiency program turn process in an embodiment of the application. Figure 2 is a schematic diagram of an attack angle in a high-efficiency program turn process in an embodiment of the application.

[0079] Step S2, design a program angle mode for the program turn segment, and set a handover point. Before the handover point, the program angle mode is a pitch angle mode; after the handover point, the program angle mode is converted from the pitch angle mode to an attack angle mode.

[0080] In some embodiments, the program turn section comprises, in sequence, a vertical ascent section, a uniform acceleration section, a uniform deceleration section, and an angle-of-attack return-to-zero section; wherein the uniform acceleration section is a first turn engine working period, the uniform deceleration section is a second turn engine working period, and the handover point is set at a handover time of the uniform deceleration section and the angle-of-attack return-to-zero section.

[0081] In some embodiments, the program angle mode comprises:

[0082] A piecewise function is constructed according to the end time of each stage in the program turn section;

[0083] The piecewise function is:

[0084]

[0085] In the formula, is a pitch angle, in °; t 1 is the end time of the vertical ascent section, in s; t 2 is the end time of the work of the first turn engine, in s; t 3 is the end time of the work of the second turn engine, in s; t 4 is the end time of the program turn / angle-of-attack return-to-zero, in s; is a ballistic angle, in °; is an angle of attack, in °; k is an angle acceleration of the program turn section, in ° / s 2 ; Figure 3 max , a turn coefficient a , t 0 is a constant term;

[0086] The end time of each stage in the program turn section and the handover point parameters are determined.

[0087] Through the above scheme, reasonable pitch angle mode and angle-of-attack mode are set in the program turn section. When designing the pitch angle mode, a piecewise function design idea is provided, so that the pitch angle change is as close as possible to the angle acceleration generated by the control moment provided by the turn engine working time, the turn engine parameters are accurately matched, the smooth turn is ensured, the full-range continuous smooth connection of the pitch angle in the turn process is realized, a better control initial value condition is provided for the subsequent flight stage, and the control precision is improved.

[0088] In some embodiments, the end time of the vertical ascent section in the program turn section t 1 is determined by:

[0089] The end time of the vertical ascent section t 1 is obtained according to the take-off thrust-weight ratio of the launch vehicle;

[0090] The calculation formula is:

[0091]

[0092] In the formula, F For the liftoff thrust of the launch vehicle, G This refers to the gravitational force experienced by the launch vehicle during takeoff.

[0093] Using the above method, the end time of the vertical ascent segment is established. t The relationship between 1 and the launch vehicle's thrust-to-weight ratio at takeoff is determined empirically in this embodiment. t The calculation formula for 1 is provided. Of course, in other embodiments, the end time of the vertical ascent segment in the turning segment of the program can also be calculated based on other calculation formulas. t 1.

[0094] In some embodiments, the time when the first turning engine finishes operating during the program turning segment is determined. t 2 includes:

[0095] Set the engine operating period during cornering t ;

[0096] Obtain the angular acceleration of the turning segment of the program. k ;

[0097] Calculate the total engine thrust during cornering I 1;

[0098] The calculation formula is: ;

[0099] Among them, M 气 For the turning engine operating period t Pitching aerodynamic moment; L This refers to the distance between the engine and the first-order center of gravity during cornering. J The moment of inertia of the first-order center of mass about the pitch direction;

[0100] Based on the total stroke of the turning engine I 1. Obtain engine parameters for cornering;

[0101] If the turning engine parameters do not meet the set requirements, modify its operating period. t ;

[0102] Repeat the above steps until the turning engine parameters meet the set requirements;

[0103] According to the working hours of the turning engine Calculate the time t2 when the first turning engine finishes working;

[0104] The calculation formula is: .

[0105] The main factors of the program turn of the launch vehicle are the turn moment provided by the turn engine and the pitch aerodynamic moment in flight. The aerodynamic moment hinders the program turn due to the aerodynamic static stability, and the total impulse of the turn engine is determined according to the momentum theorem I 1 and the moment when the first turn engine stops working t 2, angular acceleration of the program turn section k .

[0106] The specific process is as follows:

[0107] The momentum theorem formula is ;

[0108] In the formula, w is the angular velocity of the whole rocket after the turn engine stops working;

[0109] And ;

[0110] Therefore, the formula is obtained .

[0111] In the above formula, the distance between the installation position of the turn engine and the mass center of the first stage is L , the moment of inertia of the mass center of the first stage around the pitch direction is J、 , and the working period of the turn engine is t The pitch aerodynamic moment M 气 is related to the scheme of the launch vehicle, that is, a known quantity.

[0112] k is the angular acceleration of the program turn section, and different k values affect the speed of the program turn of the launch vehicle, and further affect the height of the shutdown point of the rocket. Specifically, k the greater the absolute value of k , the faster the turn, and the lower the shutdown point height. Through traversal analysis of the applicable launch mission orbit height of the launch vehicle, a reasonable interval of the angular acceleration of the program turn section is obtained, and the angular acceleration value of the program turn section is determined.

[0113] The working period of the turn engine t can be set according to experience, and should not be too long, such as 3s.

[0114] Based on the total impulse of the turn engine I 1, the parameters of the turn engine are obtained, such as the thrust, charge amount, diameter and other parameters of the turn engine.

[0115] In some embodiments, the moment when the second turn engine stops working in the program turn section is determinedt 3 includes:

[0116] According to the working period of the turn engine t Calculate the second turn engine working end time t3;

[0117] The calculation formula is: .

[0118] Since the working time of the two same turn engines is the same, the working end time t3 of the second turn engine can be determined accordingly t 3.

[0119] In some embodiments, determining the handover point parameter includes:

[0120] Based on the trajectory of the launch vehicle, the handover time t 3 corresponding attack angle ;

[0121] Based on the handover time t 3 corresponding attack angle Get the attack angle change rate ;

[0122] The calculation formula of the attack angle change rate :

[0123]

[0124] Where, h The step length when the trajectory is integrated is not greater than 0.01s.

[0125] The handover time is defined as the end of the uniform deceleration segment and the start of the attack angle return to zero segment. At this time, the program angle mode is switched from the pitch angle mode to the attack angle mode. In order to ensure the smooth and continuous change of the attack angle before and after the handover, the determined handover point parameters include the attack angle t 3 corresponding to the handover time And the attack angle change rate The attack angle Can be directly obtained by trajectory calculation, and the attack angle change rate Is approximately obtained by differential method.

[0126] Through the above scheme, the attack angle change rate is smoothed at the end of the turn engine working, so that the first order derivative of the attack angle before and after the handover is continuous, and the control quality is significantly improved.

[0127] In some embodiments, determining the program turn end / attack angle return to zero time t4 in the program turn segment includes:

[0128] Set the turn coefficient a As an initial value greater than 0;

[0129] According to the turn coefficienta determine the constant term a max , t 0;

[0130] The calculation formula is:

[0131] ;

[0132] ;

[0133] ;

[0134] According to the constant term a max , a , t 0 determine the program turn end / attack angle zero return moment t4;

[0135] The calculation formula is: ;

[0136] Wherein, δ is the absolute value of the attack angle;

[0137] Determine whether t4 is in the transonic speed section;

[0138] If t4 is in the transonic speed section, adjust the turn coefficient a Repeat the above steps until t4 is not in the transonic speed section.

[0139] Complete the program turn before the transonic speed section to prevent the normal overload from being too large.

[0140] Set the turn coefficient a When the initial value is greater than 0, , Determine the turn rate, adjust the turn coefficient a Control the end time of the turn of the launch vehicle, a > 0 The greater, the earlier the end time of the turn. When the absolute value of the attack angle δ returns to a sufficient time (such as δ takes 0.001°), the program turn ends.

[0141] Through the scheme provided by the embodiment of the application, the pitch angle mode and the attack angle mode are designed by comprehensively considering factors such as the power configuration of the launch vehicle, the thrust-to-weight ratio, the control system scheme, and the whole rocket stability, to adapt to the requirements of omnidirectional rapid turning.

[0142] It should be noted that, a In the attack angle zero return section, the pitch angle is calculated from the first three stages; a Figure 2 Figure 3 In the vertical ascent section, the uniform acceleration section, and the uniform deceleration section, the attack angle is calculated from the attack angle zero return section.

[0143] In the description of the present application, it should be noted that the terms "upper", "lower", and the like are used to indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the methods or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application. Unless otherwise expressly specified and limited, the terms "mounting", "connecting", "connecting" should be interpreted broadly, for example, "connecting" can be fixed connection, can also be detachable connection, or integral connection; can be mechanical connection, can also be electrical connection; can be directly connected, can also be indirectly connected through an intermediate medium, can be internal communication of two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0144] It should be noted that in the present application, relational terms such as "first" and "second" and the like are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. Moreover, the terms "include", "contain" or any other variant thereof are intended to cover non-exclusive inclusion, so that the process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or device. Without more limitations, the element defined by the sentence "including a..." does not exclude the presence of other identical elements in the process, method, article or device including the element.

[0145] The above is only a specific embodiment of the present application, which enables those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features applied herein.

Claims

1. A method of designing a trajectory for a program turn, the method comprising: It comprises the following steps: Two turning engines are arranged on the carrier rocket to provide lateral thrust in turn; A program turning section is designed to provide a program angle mode, and a handover point is set; Before the handover point, the program angle mode is a pitch angle mode; After the handover point, the program angle mode is converted from the pitch angle mode to an attack angle mode; The program turning section comprises a vertical ascending section, a uniform acceleration section, a uniform deceleration section, and an attack angle returning-to-zero section in turn; the uniform acceleration section is a working time section of the first turning engine, the uniform deceleration section is a working time section of the second turning engine, and the handover point is set at a handover time of the uniform deceleration section and the attack angle returning-to-zero section; The program angle mode comprises: A piecewise function is constructed according to end time points of each stage in the program turning section; The piecewise function is: wherein is the pitch angle; t 1 is the time when the vertical climb segment ends; t 2 is the time when the first engine of the turn works; t 3 is the time when the second engine of the turn works; t 4 is the time when the programmed turn ends / angle of attack returns to zero; is the ballistic angle; is the angle of attack; k is the angular acceleration of the programmed turn segment; , the turn coefficient 、 are constant terms; Parameters of end time points of each stage in the program turning section and the handover point are determined; wherein the time point at which the vertical ascending section in the program turn section ends is determined t 1 comprises: acquiring the moment when the vertical ascending stage ends according to the take-off thrust-weight ratio of the carrier rocket t 1; The calculation formula is: wherein F the launch thrust of the launch vehicle, G the gravitational force experienced by the launch vehicle at launch. wherein the first turning engine working end time point in the program turning section is determined t 2 comprises: Setting the turn engine operating period t ; acquiring angular acceleration of the program cornering section k ; calculating the total impulse of the turn engine I 1; The calculation formula is: ; where M 气 is the engine on period for the turn t is the internal pitch aerodynamic moment; L is the distance of the engine from the first mass center for the turn J is the moment of inertia of the first mass center about the pitch direction; based on the turn engine total impulse I 1 obtain the turn engine parameters; if the turning engine parameter does not meet a set requirement, modifying its working period t ; The above steps are repeated until the turning engine parameters meet the set requirements; According to the working period of the turning engine t2 calculates the first said turning engine working end time t2; The calculation formula is: ; wherein the second engine operation end time point in the program turn section is determined t 3 comprises: According to the working period of the turning engine t calculates the second station said turning engine working end time t3; The calculation formula is: ; The determination of the handover point parameters comprises: acquiring a second turning engine operation end time based on a trajectory of the launch vehicle t 3 corresponding angle of attack ; based on the second turning engine operation end time t 3 corresponding angle of attack acquiring a rate of change of angle of attack ; The rate of change of the angle of attack The formula for calculating the rate of change of the angle of attack is: wherein, h is the step size for the ballistic integration calculation; The determination of the end time point t4 of the program turning / attack angle returning-to-zero in the program turning section comprises: Setting a cornering coefficient is an initial value greater than 0; According to the cornering coefficient Determining constant terms , ; The calculation formula is: ； ； ； According to the constant term , , Determine the program turn end / angle of attack zero moment t4; The calculation formula is: ; Wherein, δ is the absolute value of the attack angle; It is judged whether the end time point t4 of the program turning / attack angle returning-to-zero is in the transonic section; If t4 is in the transonic region, adjust the turn coefficient ， Repeat the above steps until t4 is not in the transonic region.

2. A method of designing a trajectory for a program turn as recited in claim 1, wherein, The turning engine is two identical side-jet turning engines.

3. A method of designing a trajectory for a program turn as claimed in any one of claims 1 to 2, wherein, The turning engines are symmetrically arranged on the carrier rocket.

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