A method for accurately recovering a booster with multiple rectangular targets by using a controllable parafoil

Abstract

A method for precisely recovering a booster with multiple rectangular targets by using a controllable parafoil. The landing area is divided into three regions by multiple rectangles. Region 1 is outside the online target rectangles 2 and 3, Region 2 is inside the online target rectangle 2, and Region 3 is inside the online target rectangle 3. When the projection point of the parafoil is in Region 1, the parafoil is maneuvered to fly towards the boundary of the online target rectangle 2 or 3, and the foot intersection point of the parafoil point and the outer frame of the online target or the frame endpoint is selected as the optimal target point. When the projection point is inside Region 2, the parafoil is maneuvered to fly towards the target points 1-4 inside Target 2, and the point closest to the parafoil point among the target points 1-4 is taken as the optimal target point. When the projection point is inside Region 3, the parafoil is maneuvered to fly towards the target points 5-8 inside Target 2, and the point closest to the parafoil point among the target points 5-8 is taken as the optimal target point. The present invention can effectively achieve the landing of the rocket booster in a safe area and avoid crowded areas, thereby achieving an ideal safe and controllable recovery effect of the launch vehicle booster.

Description

Technical Field

[0001] The present invention relates to a method for precisely recovering a booster with multiple rectangular targets by using a controllable parafoil, and belongs to the technical field of spacecraft return and landing. Background Art

[0002] In order to reduce the landing point dispersion of the separation bodies of a launch vehicle (including a fairing, a core stage, and a booster), minimize the safety risks brought by the landing of the separation bodies to the ground, and effectively reduce the evacuation and resettlement costs in the landing area, it is necessary to study the control of the final stage of the separation body during its reentry into the atmosphere. By utilizing the controllable gliding function of a large parafoil, the controllable flight of the separation body can be achieved, effectively reducing the safety risks in the landing area. A method for precisely recovering a booster with multiple rectangular targets by using a controllable parafoil described in this patent is an important part of the recovery system of a launch vehicle booster. By controlling the parafoil, the flight control of the launch vehicle booster during the landing process in a fixed area can be achieved.

[0003] After the launch vehicle booster is separated from the rocket body, it will be in a free-fall state after rising to the highest point. When it reaches below 20 km, the state parameters such as the vertical speed, horizontal speed, and attitude variables during the descent of the rocket booster tend to be stable. At this time, the recovery system starts to deploy parachutes of each stage in sequence to reduce the vertical and horizontal speeds of the booster. The last-stage parachute is a controllable parafoil. The controllable parafoil has the characteristic of being able to control the horizontal speed direction according to the manipulation of the servo mechanism of the homing system. The dispersion range of the launch vehicle booster that freely falls to the ground without control after being separated from the main body reaches more than 2000 km 2 above. By using a parafoil with the ability to control the gliding direction and utilizing its direction controllability, the dispersion range can be effectively reduced. However, since the parafoil is a powerless deceleration device, after its parachute is deployed and stabilized, the vertical and horizontal speed values also enter a relatively stable state, and it is impossible to significantly increase the horizontal speed. Therefore, when its homing ability is not sufficient to cover the entire landing area, using a single fixed target point may cause the launch vehicle booster to be difficult to reach the predetermined target landing area, and it is also difficult to avoid areas where landing is not allowed such as villages and towns. Therefore, there is an urgent need to design a multi-rectangular target homing method according to the dispersion characteristic range of the landing area. Summary of the Invention

[0004] The purpose of the present invention is to overcome the above defects and provide a method for precisely recovering a booster with multiple rectangular targets by using a controllable parafoil, so as to achieve the landing of the rocket booster in a safe area and avoid densely populated areas, thereby achieving an ideal safe and controllable recovery effect of the launch vehicle booster.

[0005] The technical solution adopted by the present invention is as follows:

[0006] A method for precisely recovering a booster with multiple rectangular targets by using a controllable parafoil, comprising:

[0007] (1) The landing area is divided into three regions by the landing area boundary, namely Region 1, Region 2, and Region 3; Region 1 is outside the online target rectangles 2 and 3, Region 2 is inside the online target rectangle 2, and Region 3 is inside the online target rectangle 3;

[0008] (2) Determine whether the parafoil projection point is located in Region 1, Region 2, or Region 3;

[0009] (3) When the parafoil projection point is in Region 1, control the parafoil to fly towards the boundary of the online target rectangle 2 or 3; select the foot of the perpendicular intersection point or the frame endpoint of the outer frame of the online target rectangle 2 or 3 that is closer to the parafoil projection point as the optimal target point;

[0010] (4) When the parafoil projection point is in Region 2, control the parafoil to fly towards the target points 1, 2, 3, and 4 inside the online target rectangle 2; select the point closest to the parafoil projection point among the target points 1, 2, 3, and 4 as the optimal target point;

[0011] (5) When the parafoil projection point is in Region 3, control the parafoil to fly towards the target points 5, 6, 7, and 8 inside the online target rectangle 3; select the point closest to the parafoil projection point among the target points 5, 6, 7, and 8 as the optimal target point.

[0012] Further, the online target rectangle 1 is the dispersion range of the booster uncontrolled landing state with a size of 90 * 30 km; the parachute landing area is the online target rectangles 2 and 3 with a size of 90 * 3 km inside rectangle 1.

[0013] Further, the determination of whether the parafoil projection point is located in Region 1, Region 2, or Region 3 is specifically as follows:

[0014] Determine whether the parafoil projection point is inside or outside the online target rectangle 2, and set the corresponding flag Flag2. If it is inside, set Flag2 = 1; if it is outside, set Flag2 = 0;

[0015] Determine whether the parafoil projection point is inside or outside the online target rectangle 3, and set the corresponding flag Flag3. If it is inside, set Flag3 = 1; if it is outside, set Flag3 = 0;

[0016] If Flag3 = 0 and Flag2 = 0, it is determined that the parafoil projection point is located in Region 1;

[0017] If Flag2 = 1 and Flag3 = 0, it is determined that the parafoil projection point is located in Region 2;

[0018] If Flag3 = 1 and Flag2 = 0, it is determined that the parafoil projection point is located in Region 3.

[0019] Further, the calculation method for determining whether the wing parachute projection point is inside or outside the linear target rectangle is as follows:

[0020] Assume that the wing parachute projection point is P;

[0021] Calculate the coordinates of the midpoints A1, B1, C1, and D1 of the sides of rectangle ABCD respectively, and calculate the coordinates of the center point O of the rectangle;

[0022] Then calculate the coordinates of the perpendicular foot points P1 and P2 of the wing parachute projection point and the two center lines of the rectangular area;

[0023] Then calculate the lengths of PP1, PP2, DD1, and DC1 respectively. If PP1 < DD1 and PP2 < DC1, it is determined that point P is inside rectangle area ABCD, otherwise it is determined that point P is outside rectangle area ABCD;

[0024] Among them, PP1 is the distance from point P to P1; PP2 is the distance from point P to P2; DD1 is the distance from point D to D1; DC1 is the distance from point D to C1.

[0025] Further, when the wing parachute projection point is in area 1, the locking method for the optimal target point is as follows:

[0026] (3.1) Calculate the perpendicular foot points of the wing parachute projection point to the four boundary line segments of linear target rectangle 2, denoted as CuizuPoint_1, CuizuPoint_2, CuizuPoint_3, CuizuPoint_4;

[0027] (3.2) For each line segment corresponding to each side, respectively determine whether Cuizu_Point_1 to 4 are on each line segment or outside the line segment. If they are outside the line segment, discard them. Suppose there are Q points on the line segment, then the value range of Q is: Q >= 0 and Q <= 4; If there are perpendicular foot points located on the line segment, they are denoted as CuizuPointIn_1 to CuizuPointIn_M, where; M >= 1 and M <= 4;

[0028] The two endpoints of the four line segments are respectively denoted as DuandianPoint_A_1, DuandianPoint_B_1, DuandianPoint_A_2, DuandianPoint_B_2, DuandianPoint_A_3, DuandianPoint_B_3, DuandianPoint_A_4, DuandianPoint_B_4;

[0029] (3.3) Calculate the distances between the projected point of the parafoil and the points CuizuPointIn_1 to CuizuPointIn_M, DuandianPoint_A_1 to 4,

[0030] DuandianPoint_B_1 to 4 calculated on the four sides of the linear target rectangle 2, denoted as RecDistance_1 to N, where N >= 4 and N <= 8;

[0031] (3.4) Sort RecDistance_1 to N, and select the nearest target point marked as RecDestinationPoint_J; this target point is the optimal target point from the projected point of the parafoil to the border of the linear target rectangle 2;

[0032] (3.5) Similarly, calculate the optimal target point from the projected point of the parafoil to the border of the linear target rectangle 3, denoted as RecDestinationPoint_K;

[0033] (3.6) Calculate the distances RecDistance_J and RecDistance_K between the projected point of the parafoil and the target points RecDestinationPoint_J and RecDestinationPoint_K respectively;

[0034] (3.7) Sort RecDistance_J and RecDistance_K, and select the nearest target point marked as RecDestinationPoint_L;

[0035] (3.8) RecDestinationPoint_L is the real-time optimal target point of the projected point of the parafoil relative to the border of the linear target rectangle 2 and the border of the linear target rectangle 3.

[0036] Furthermore, the method for determining whether the foot intersection point T of the perpendicular line drawn from the projected point of the parafoil to the line segment is on the line segment AB or outside the line segment is as follows:

[0037] Calculate the distances DistanceTA and DistanceTB between the point T and the two endpoints A and B of the two line segments respectively;

[0038] Then calculate the distance DistanceAB between the two endpoints of the line segment;

[0039] If DistanceTA + DistanceTB = DistanceAB, it means that the point T is on the line segment AB;

[0040] If DistanceTA + DistanceTB > DistanceAB; it means that the point T is outside the line segment AB.

[0041] Further, when the wing parachute projection point is in Region 2 or Region 3, the method for locking the optimal target point is as follows:

[0042] (4.1) Calculate the distances MultDestiDistance_1 to MultDestiDistance_N between the wing parachute projection point and multiple target points MultDestiPoint_1 to MultDestiPoint_N respectively;

[0043] (4.2) Sort MultDestiDistance_1 to MultDestiDistance_N, and select the nearest target point and mark it as MultDestiPoint_M;

[0044] (4.3) MultDestiPoint_M is the real-time optimal target point.

[0045] Further, the present invention also proposes a system for accurately recovering a booster with multiple rectangular targets by using a controllable wing parachute, including:

[0046] Region division module: Divide the landing area into three regions through the landing area boundary, namely Region 1, Region 2, and Region 3; Region 1 is outside the on-line target rectangles 2 and 3, Region 2 is inside the on-line target rectangle 2, and Region 3 is inside the on-line target rectangle 3; The on-line target rectangle 1 is the dispersion range of the landing area in the uncontrolled landing state of the booster with a size of 90*30 km; The parachute landing area is the on-line target rectangles 2 and 3 with a size of 90*3 km inside rectangle 1;

[0047] Region judgment module: Judge whether the wing parachute projection point is located in Region 1, Region 2, or Region 3;

[0048] Optimal target point determination module: When the wing parachute projection point is in Region 1, control the wing parachute to fly towards the boundary of the on-line target rectangle 2 or 3; Select the foot of the perpendicular intersection point or the frame endpoint of the outer frame of the on-line target rectangle 2 or 3 that is closer to the wing parachute projection point as the optimal target point;

[0049] When the wing parachute projection point is in Region 2, control the wing parachute to fly towards the target points 1, 2, 3, 4 inside the on-line target rectangle 2; Select the point closest to the wing parachute projection point among the target points 1, 2, 3, 4 as the optimal target point;

[0050] When the wing parachute projection point is in Region 3, control the wing parachute to fly towards the target points 5, 6, 7, 8 inside the on-line target rectangle 3; Select the point closest to the wing parachute projection point among the target points 5, 6, 7, 8 as the optimal target point.

[0051] The present invention has the following beneficial effects compared with the prior art:

[0052] (1) The present invention innovatively proposes a method for realizing accurate recovery of multiple rectangular targets of boosters by using a controllable parafoil, and realizes accurate homing to multiple rectangular landing areas under the premise of stable and efficient landing;

[0053] (2) The method of the present invention can automatically plan the optimal flight path of the parafoil and booster combination in real time, and optimize the optimal flight path of the parafoil in real time according to the real-time flight state parameters of the combination, thereby achieving effective control over the precise recovery process of the booster based on the parafoil;

[0054] (3) The method of the present invention innovatively proposes a variety of precise homing methods in different regions to meet the needs of precise recovery of the parafoil-boost assembly, which can meet the complex conditions of the precise and controllable recovery process of the parafoil-boost assembly and realize automatic control. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 This is an example diagram of multiple rectangular homing landing areas of the present invention;

[0056] Figure 2 This is an example diagram of homing in the multi-rectangular homing area 1 of the present invention;

[0057] Figure 3 This is a schematic diagram of homing in multiple rectangular homing areas 2 and 3 of the present invention;

[0058] Figure 4 A schematic diagram of a calculation method for determining whether a parafoil projection point is inside or outside a rectangular area according to the present invention;

[0059] Figure 5 The invention provides a calculation method for judging whether a parafoil projection point is on a line segment. DETAILED DESCRIPTION

[0060] The following detailed description of the present invention will make the features and advantages of the present invention more clear and explicit.

[0061] The parafoil is an unpowered deceleration device. After the parachute is opened and stabilized, the vertical and horizontal speed values ​​also enter a relatively stable state, and the horizontal speed cannot be significantly increased. Therefore, when its homing capability is insufficient to cover the entire landing area, the launch vehicle booster recovered by the controllable parafoil may have difficulty in reaching the predetermined target landing area using the homing method of a single fixed target point, and therefore it is also difficult to avoid villages, towns and other areas where landing is not possible.

[0062] The present invention provides a method for realizing accurate recovery of multiple rectangular targets of a booster by using a controllable parachute, so that the rocket booster can land in a safe area and avoid crowded areas, thereby achieving an ideal safe and controllable recovery effect of the launch vehicle booster.

[0063] The present invention provides a method for accurately recovering a booster with multiple rectangular targets by using a controllable parafoil, including:

[0064] (1) Divide the landing area into three regions through the landing area boundary, namely Region 1, Region 2, and Region 3, as shown in Figure 1 the hexagonal identifier. Region 1 is outside the on-line target rectangles 2 and 3, Region 2 is inside the on-line target rectangle 2, and Region 3 is inside the on-line target rectangle 3;

[0065] The on-line target rectangle 1 is the dispersion range of the booster's uncontrolled landing state with a size of 90*30 km; the parachute landing area is the on-line target rectangles 2 and 3 with a size of 90*3 km inside rectangle 1;

[0066] (2) Determine whether the parafoil projection point is in Region 1, Region 2, or Region 3;

[0067] (3) When the parafoil projection point is in Region 1, control the parafoil to fly towards the boundary of the on-line target rectangle 2 or 3; select the foot of the perpendicular intersection point or the frame endpoint of the parafoil projection point and the outer frame of the on-line target rectangle 2 or 3 that is closer to the parafoil projection point as the optimal target point; see Figure 2 .

[0068] (4) When the parafoil projection point is in Region 2, control the parafoil to fly towards the target points 1, 2, 3, 4 inside the on-line target rectangle 2; select the point closest to the parafoil projection point among the target points 1, 2, 3, 4 as the optimal target point;

[0069] (5) When the parafoil projection point is in Region 3, control the parafoil to fly towards the target points 5, 6, 7, 8 inside the on-line target rectangle 3; select the point closest to the parafoil projection point among the target points 5, 6, 7, 8 as the optimal target point.

[0070] Example:

[0071] The dispersion range of the booster's uncontrolled landing state of the launch vehicle is a rectangular area. Two parachute landing areas are selected as target lines (two long rectangles) within the rectangular landing area, and multiple landing points (such as Figure 1 8 in the example) are selected within the target lines, and multiple obstacle avoidance points (such as Figure 1 2 in the example) are selected within the landing area range and input in advance before the rocket takes off. See the example diagram of the landing area in Figure 1Among them, the square signs are the boundary signs of the landing area. Rectangle 1 is the rectangular boundary of the dispersion range of the booster during uncontrolled landing, with a size of 90 km × 30 km. Rectangles 2 and 3 are the rectangular boundaries of the double target lines of the parachute landing area, with a width of 3 km and a length of 90 km. Parallelogram 4 is the boundary of the obstacle avoidance area, with a size of 10 km × 30 km. The 8 triangular signs are the target point signs. The 2 pentagram signs are the obstacle avoidance point signs. The hexagonal signs are the regional division numbers of the parafoil landing area. Among them, outside rectangles 1, 2, and 3 is recorded as area 1, inside rectangle 2 is recorded as area 2, and inside rectangle 3 is recorded as area 3.

[0072] The goal of the parafoil recovery landing point is to ensure that the system must land inside rectangles 2 and 3 (areas 2 and 3), and try to land within the target circular areas centered on target points 1-8 (triangular signs) with the minimum turning radius of the parafoil within rectangles 2 and 3. On this basis, try to avoid landing inside the obstacle avoidance area (rectangle 4). Therefore, the settings of target points 1-8 inside rectangles 2 and 3 should be as far away from the inside of rectangle 4 as possible.

[0073] The landing area is divided into three areas by the boundary of the landing area, as shown in Figure 1 hexagonal identifiers 1-3.

[0074] Area 1 is outside the online target rectangles 2 and 3. When the parafoil projection point is in area 1, control the parafoil to fly towards the boundary of line target 2 or 3. Select the foot of the perpendicular intersection point or the frame end point of the parafoil projection point and the outer frame of the long rectangles 2 and 3 (select the point closest to the parafoil projection point) as the optimal target point, as shown in Figure 2 。

[0075] The specific implementation method is as follows:

[0076] a) Calculate the foot of the perpendicular points of the parafoil projection point to the four boundary line segments of line target rectangle 2, and record them as CuizuPoint_1, CuizuPoint_2, CuizuPoint_3, and CuizuPoint_4 respectively;

[0077] b) For each line segment corresponding to an edge, determine whether Cuizu_Point_1 to 4 are on each line segment or outside the line segment. If they are outside the line segment, discard them. Suppose there are Q points on the line segment, then the value range of Q is: Q >= 0 and Q <= 4. If there are foot points located on the line segment, they are denoted as CuizuPointIn_1 to CuizuPointIn_M, where M >= 1 and M <= 4. Each of the four line segments forming rectangle 2 has two endpoints, which are respectively denoted as DuandianPoint_A_1, DuandianPoint_B_1, DuandianPoint_A_2, DuandianPoint_B_2, DuandianPoint_A_3, DuandianPoint_B_3, DuandianPoint_A_4, DuandianPoint_B_4.

[0078] Calculate the distances from the parafoil projection point to CuizuPointIn_1 to CuizuPointIn_M, DuandianPoint_A_1 to 4, and DuandianPoint_B_1 to 4 calculated for the four edges of the line target rectangle 2, and denote them as RecDistance_1 to N, where N >= 4 and N <= 8;

[0079] c) Sort RecDistance_1 to N and select the nearest target point, denoted as RecDestinationPoint_J; this target point is the optimal target point from the parafoil projection point to the border of the line target rectangle 2.

[0080] d) Calculate the optimal target point from the parafoil projection point to the border of the line target rectangle 3 again using the above method, denoted as RecDestinationPoint_K;

[0081] e) Calculate the distances RecDistance_J and RecDistance_K between the parafoil projection point and the target points RecDestinationPoint_J and RecDestinationPoint_K respectively;

[0082] f) Sort RecDistance_J and RecDistance_K and select the nearest target point, denoted as RecDestinationPoint_L;

[0083] g) RecDestinationPoint_L is the real-time optimal target point of the parafoil projection point relative to the borders of the line target rectangle 2 and the line target rectangle 3.

[0084] Region 2 is inside the online target 2. When the projected point of the parafoil is inside Region 2, control the parafoil to fly towards the target points 1, 2, 3, and 4 within the target 2. Select the target point among points 1, 2, 3, and 4 that is closest to the parafoil point as the optimal target point.

[0085] Region 3 is inside the online target 3. When the projected point of the parafoil is inside Region 3, control the parafoil to fly towards the target points 5, 6, 7, and 8 within the target 2. Select the target point among points 5, 6, 7, and 8 that is closest to the parafoil point as the optimal target point. See the homing example diagrams for Regions 2 and 3 in Figure 3 。

[0086] The specific implementation method is as follows:

[0087] a) Calculate the distances MultDestiDistance_1 to MultDestiDistance_N between the projected point of the parafoil and multiple target points respectively;

[0088] b) Sort MultDestiDistance_1 to MultDestiDistance_N and select the closest target point and mark it as MultDestiPoint_M;

[0089] c) MultDestiPoint_M is the real-time optimal target point.

[0090] The method for determining whether the projected point of the parafoil is located in Region 1 or 2 or 3 can be seen in Figure 4 ,and the specific steps are as follows:

[0091] a) First, determine whether the parafoil point is inside or outside the target rectangles 2 and 3. The calculation method for determining whether the projected point of the parafoil is inside or outside the rectangular area can be seen in Figure 4 : Assume that the projected point of the parafoil is P. Calculate the coordinates of the midpoints A1, B1, C1, and D1 of the sides of the rectangle ABCD respectively, and calculate the coordinates of the center point O of the rectangle. Then calculate the coordinates of the foot points P1 and P2 of the projected point of the parafoil relative to the two center lines A1C1 and B1D1 of the rectangular area. Then calculate the lengths of the line segments PP1, PP2, DD1, and DC1 respectively. If PP1 < DD1 and PP2 < DC1, then it can be determined that point P is inside the rectangular area ABCD, otherwise it can be determined that point P is outside the rectangular area ABCD.

[0092] b) Determine whether the position of the projected point of the parafoil is inside or outside the rectangle 2 ( Figure 3 square label); and set the corresponding flag Flag2; if it is inside, set Flag2 = 1, if it is outside, set Flag2 = 0;

[0093] c) Determine whether the position of the projected point of the parafoil is inside or outside the rectangle 3 ( Figure 3Whether it is inside or outside the square label); and set the corresponding flag Flag3; if it is inside, set Flag3 = 1, if it is outside, set Flag3 = 0;

[0094] d) If Flag3 = 0 and Flag2 = 0, it can be determined that the projected point of the parafoil is in area 1. If Flag2 = 1 and Flag3 = 0, it can be determined that the projected point of the parafoil is in area 2. If Flag2 = 0 and Flag3 = 1, it can be determined that the projected point of the parafoil is in area 3. If Flag2 = 1 and Flag3 = 1, since there is no intersection between the two rectangles in areas 2 and 3, it is determined as a calculation error.

[0095] The method for determining whether the foot intersection point T of the perpendicular line drawn from the projected point of the parafoil to the line segment is on the line segment AB or outside the line segment can be seen in Figure 5 , and the specific steps are as follows:

[0096] a) Calculate the distances DistanceTA and DistanceTB between point T and the two endpoints A and B of the line segment respectively;

[0097] b) Calculate the distance DistanceAB between the two endpoints of the line segment;

[0098] c) If DistanceTA + DistanceTB = DistanceAB; it means that point T is on the line segment AB;

[0099] d) If DistanceTA + DistanceTB > DistanceAB; it means that point T is outside the line segment AB.

[0100] The present invention has been described in detail above in combination with specific embodiments and exemplary examples, but these descriptions should not be construed as limiting the present invention. Those skilled in the art understand that without departing from the spirit and scope of the present invention, various equivalent substitutions, modifications or improvements can be made to the technical solutions and their implementation manners of the present invention, and these all fall within the scope of the present invention. The protection scope of the present invention is subject to the appended claims.

[0101] The content not described in detail in the specification of the present invention belongs to the well-known technology of those skilled in the art.

Claims

1. A method for precisely recovering a booster with multiple rectangular targets by using a controllable parafoil, characterized in that, Including: (1) Divide the landing area into three regions through the landing area boundary, namely Region 1, Region 2, and Region 3; Region 1 is outside the online target rectangles 2 and 3, Region 2 is inside the online target rectangle 2, and Region 3 is inside the online target rectangle 3; (2) Determine whether the parafoil projection point is located in Region 1, Region 2, or Region 3; (3) When the parafoil projection point is in Region 1, control the parafoil to fly towards the boundary of the online target rectangle 2 or 3; select the foot of the perpendicular intersection point or the frame endpoint of the outer frame of the online target rectangle 2 or 3 that is closer to the parafoil projection point as the optimal target point; (4) When the parafoil projection point is in Region 2, control the parafoil to fly towards the target points 1, 2, 3, 4 inside the online target rectangle 2; take the point closest to the parafoil projection point among the target points 1, 2, 3, 4 as the optimal target point; (5) When the parafoil projection point is in Region 3, control the parafoil to fly towards the target points 5, 6, 7, 8 inside the online target rectangle 3; take the point closest to the parafoil projection point among the target points 5, 6, 7, 8 as the optimal target point; The online target rectangle 1 is the dispersion range of the landing area in the uncontrolled landing state of the booster with a size of 90*30 km; the parachute landing area is the online target rectangles 2 and 3 with a size of 90*3 km inside rectangle 1; The determination of whether the parafoil projection point is located in Region 1, Region 2, or Region 3 is specifically as follows: Determine whether the position of the parafoil projection point is inside or outside the online target rectangle 2, and set the corresponding flag Flag2. If it is inside, set Flag2 = 1; if it is outside, set Flag2 = 0; Determine whether the position of the parafoil projection point is inside or outside the online target rectangle 3, and set the corresponding flag Flag3. If it is inside, set Flag3 = 1; if it is outside, set Flag3 = 0; If Flag3 = 0 and Flag2 = 0, it is determined that the parafoil projection point is located in Region 1; If Flag2 = 1 and Flag3 = 0, it is determined that the parafoil projection point is located in Region 2; If Flag3 = 1 and Flag2 = 0, it is determined that the parafoil projection point is located in Region 3; When the parafoil projection point is in Region 1, the method for locking the optimal target point is as follows: (3.1) Calculate the foot of the perpendicular points of the parafoil projection point to the four boundary line segments of the online target rectangle 2, denoted as CuizuPoint_1, CuizuPoint_2, CuizuPoint_3, CuizuPoint_4; (3.2) For each line segment corresponding to each side, respectively determine whether CuizuPoint_1 to 4 are on each line segment or outside the line segment. If they are outside the line segment, discard them. Suppose there are Q points on the line segment, then the value range of Q is: Q >= 0 and Q <= 4; if there are foot of the perpendicular points located on the line segment, denote them as CuizuPointIn_1 to CuizuPointIn_M, where; M >= 1 and M <= 4; The two endpoints of the four line segments are denoted as DuandianPoint_A_1, DuandianPoint_B_1, DuandianPoint_A_2, DuandianPoint_B_2, DuandianPoint_A_3, DuandianPoint_B_3, DuandianPoint_A_4, and DuandianPoint_B_4 respectively; (3.3) Calculate the distances between the parafoil projection point and CuizuPointIn_1 to CuizuPointIn_M, DuandianPoint_A_1 to 4, DuandianPoint_B_1 to 4 calculated on the four sides of the line target rectangle 2, and denote them as RecDistance_1 to N, where N >= 4 and N <= 8; (3.4) Sort RecDistance_1 to N, and select the nearest target point and mark it as RecDestinationPoint_J; this target point is the optimal target point from the parafoil projection point to the border of the line target rectangle 2; (3.5) Similarly, calculate the optimal target point from the parafoil projection point to the border of the line target rectangle 3, and denote it as RecDestinationPoint_K; (3.6) Calculate the distances RecDistance_J and RecDistance_K between the parafoil projection point and the target points RecDestinationPoint_J and RecDestinationPoint_K respectively; (3.7) Sort RecDistance_J and RecDistance_K, and select the nearest target point and mark it as RecDestinationPoint_L; (3.8) RecDestinationPoint_L is the real-time optimal target point of the parafoil projection point relative to the borders of the line target rectangle 2 and the line target rectangle 3; When the parafoil projection point is in area 2 or area 3, the method for locking the optimal target point is as follows: (4.1) Calculate the distances MultDestiDistance_1 to MultDestiDistance_N between the parafoil projection point and multiple target points MultDestiPoint_1 to MultDestiPoint_N respectively; (4.2) Sort MultDestiDistance_1 to MultDestiDistance_N, and select the nearest target point and mark it as MultDestiPoint_M; (4.3) MultDestiPoint_M is the real-time optimal target point.

2. The method for precisely recovering a booster with multiple rectangular targets by using a controllable parafoil according to claim 1, characterized in that: The calculation method for determining whether the parafoil projection point is inside or outside the line target rectangle is as follows: Assume that the parafoil projection point is P; Calculate the coordinates of the midpoints A1, B1, C1, and D1 of the sides of the rectangle ABCD respectively, and calculate the coordinates of the center point O of the rectangle; Then calculate the coordinates of the foot points P1 and P2 of the parafoil projection point on the two center lines of the rectangular area; Calculate the lengths of PP1, PP2, DD1, and DC1 respectively. If PP1 < DD1 and PP2 < DC1, then it is determined that point P is inside the rectangular area ABCD; otherwise, it is determined that point P is outside the rectangular area ABCD. Among them, PP1 is the distance from point P to P1; PP2 is the distance from point P to P2; DD1 is the distance from point D to D1; DC1 is the distance from point D to C1.

3. A method for accurately recovering a booster with multiple rectangular targets by using a controllable parafoil, characterized in that: The method for determining whether the foot intersection point T of the perpendicular line drawn from the parafoil projection point to the line segment is on the line segment AB or outside the line segment is as follows: Calculate the distances DistanceTA and DistanceTB from point T to the two endpoints A and B of the line segment respectively. Then calculate the distance DistanceAB between the two endpoints of the line segment. If DistanceTA + DistanceTB = DistanceAB, it means that point T is on the line segment AB. If DistanceTA + DistanceTB > DistanceAB, it means that point T is outside the line segment AB.

4. A system for accurately recovering a booster with multiple rectangular targets by using a controllable parafoil, characterized in that It includes: Region division module: Divide the landing area into three regions through the landing area boundary, namely Region 1, Region 2, and Region 3; Region 1 is outside the line target rectangles 2 and 3, Region 2 is inside the line target rectangle 2, and Region 3 is inside the line target rectangle 3; The line target rectangle 1 is the landing area dispersion range in the uncontrolled landing state of the booster with a size of 90 * 30 km; The parachute landing area is the line target rectangles 2 and 3 with a size of 90 * 3 km inside rectangle 1. Region judgment module: Judge whether the parafoil projection point is in Region 1, Region 2, or Region 3. Optimal target point determination module: When the parafoil projection point is in Region 1, control the parafoil to fly towards the boundary of the line target rectangle 2 or 3; Select the foot intersection point or the border endpoint of the parafoil projection point and the outer border of the line target rectangle 2 or 3 that is closer to the parafoil projection point as the optimal target point. When the parafoil projection point is in Region 2, control the parafoil to fly towards the target points 1, 2, 3, 4 inside the line target rectangle 2; Select the point closest to the parafoil projection point among the target points 1, 2, 3, 4 as the optimal target point. When the parafoil projection point is in Region 3, control the parafoil to fly towards the target points 5, 6, 7, 8 inside the line target rectangle 3; Select the point closest to the parafoil projection point among the target points 5, 6, 7, 8 as the optimal target point. The determination of whether the parafoil projection point is in Region 1, Region 2, or Region 3 is specifically as follows: Judge whether the position of the parafoil projection point is inside or outside the line target rectangle 2, and set the corresponding flag Flag2. If it is inside, set Flag2 = 1; if it is outside, set Flag2 = 0. Judge whether the position of the parafoil projection point is inside or outside the line target rectangle 3, and set the corresponding flag Flag3. If it is inside, set Flag3 = 1; if it is outside, set Flag3 = 0. If Flag3 = 0 and Flag2 = 0, it is determined that the parafoil projection point is in Region 1. If Flag2 = 1 and Flag3 = 0, it is determined that the parafoil projection point is in Region 2. If Flag3 = 1 and Flag2 = 0, it is determined that the parafoil projection point is in Region 3. The calculation method for determining whether the projected point of the parafoil is inside or outside the linear target rectangle is as follows: Assume that the projected point of the parafoil is P; Calculate the coordinates of the midpoints A1, B1, C1, and D1 of the sides of the rectangle ABCD respectively, and calculate the coordinates of the center point O of the rectangle; Then calculate the coordinates of the foot points P1 and P2 of the projected point of the parafoil on the two center lines of the rectangular area; Then calculate the lengths of PP1, PP2, DD1, and DC1 respectively. If PP1 < DD1 and PP2 < DC1, it is determined that point P is inside the rectangle ABCD, otherwise it is determined that point P is outside the rectangle ABCD; Among them, PP1 is the distance from point P to P1; PP2 is the distance from point P to P2; DD1 is the distance from point D to D1; DC1 is the distance from point D to C1; When the projected point of the parafoil is in area 1, the method for locking the optimal target point is as follows: (3.1) Calculate the foot points of the projected point of the parafoil on the four boundary line segments of the linear target rectangle 2, denoted as CuizuPoint_1, CuizuPoint_2, CuizuPoint_3, and CuizuPoint_4; (3.2) For each line segment corresponding to each side, respectively determine whether CuizuPoint_1 to 4 are on each line segment or outside the line segment. If they are outside the line segment, discard them. Assume that there are Q points on the line segment, then the value range of Q is: Q >= 0 and Q <= 4; If there are foot points located on the line segment, denote them as CuizuPointIn_1 to CuizuPointIn_M, where; M >= 1 and M <= 4; The two endpoints of the four line segments are respectively denoted as DuandianPoint_A_1, DuandianPoint_B_1, DuandianPoint_A_2, DuandianPoint_B_2, DuandianPoint_A_3, DuandianPoint_B_3, DuandianPoint_A_4, DuandianPoint_B_4; (3.3) Calculate the distances between the projected point of the parafoil and CuizuPointIn_1 to CuizuPointIn_M, DuandianPoint_A_1 to 4, DuandianPoint_B_1 to 4 calculated on the four sides of the linear target rectangle 2, denoted as RecDistance_1 to N, where N >= 4 and N <= 8; (3.4) Sort RecDistance_1 to N, and select the nearest target point and mark it as RecDestinationPoint_J; This target point is the optimal target point of the projected point of the parafoil to the border of the linear target rectangle 2; (3.5) Similarly, calculate the optimal target point of the projected point of the parafoil to the border of the linear target rectangle 3, denoted as RecDestinationPoint_K; (3.6) Calculate the distances RecDistance_J and RecDistance_K between the parafoil projection point and the target points RecDestinationPoint_J and RecDestinationPoint_K respectively; (3.7) Sort RecDistance_J and RecDistance_K, and select the nearest target point and mark it as RecDestinationPoint_L; (3.8) RecDestinationPoint_L is the real-time optimal target point of the parafoil projection point relative to the boundaries of the linear target rectangle 2 and the linear target rectangle 3; The method to determine whether the foot intersection point T of the perpendicular line drawn from the parafoil projection point to the line segment is on the line segment AB or outside the line segment is as follows: Calculate the distances DistanceTA and DistanceTB between the point T and the two endpoints A and B of the line segment respectively; Then calculate the distance DistanceAB between the two endpoints of the line segment; If DistanceTA + DistanceTB = DistanceAB, it means that the point T is on the line segment AB; If DistanceTA + DistanceTB > DistanceAB, it means that the point T is outside the line segment AB; When the parafoil projection point is in area 2 or area 3, the method for locking the optimal target point is as follows: (4.1) Calculate the distances MultDestiDistance_1 to MultDestiDistance_N between the parafoil projection point and multiple target points MultDestiPoint_1 to (4.2) Sort MultDestiDistance_1 to MultDestiDistance_N, and select the nearest target point and mark it as MultDestiPoint_M; (4.3) MultDestiPoint_M is the real-time optimal target point.

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