Near space aircraft adjustable head cone and adjusting method thereof

Abstract

The invention relates to a near space aircraft adjustable head cone and an adjusting method thereof, and belongs to the technical field of mechanism science and the technical field of aerospace. The adjustable nose cone comprises a first-stage actuator, a second-stage actuator, a third-stage actuator, an aircraft nose cone shell and an aircraft nose cone skin. The aircraft nose cone shell is covered with the aircraft nose cone skin, and the aircraft nose cone shell is connected with the first-stage actuator, the second-stage actuator, the third-stage actuator and the aircraft nose cone skin in a bearing mode and provides structural support for the aircraft nose cone skin. The first-stage actuator, the second-stage actuator and the third-stage actuator are connected in series, can stretch out and draw back along the central axis of the aircraft nose cone and deflect by a preset angle relative to the central axis of the aircraft nose cone, so that the angle and the stretching length of the aircraft nose cone are adjustable.

Description

Technical Field

[0001] This invention relates to an adjustable nose cone for a near-space vehicle and its adjustment method, applicable to the nose cone attitude adjustment of a spacecraft when it is conducting cross-domain flight missions in the vicinity of near space in a space-to-ground travel scenario. It belongs to the fields of mechanical technology and aerospace technology. Background Technology

[0002] Aerospace vehicles (ASVs) broadly refer to launch platforms capable of traveling between air and space. They are a new type of launch vehicle combining aviation and aerospace technologies. Ideally, they should possess the functions of both aircraft and spacecraft, namely autonomous takeoff and landing and air-to-space flight, while also meeting the complex flight environments and mission requirements of different flight phases to perform air-to-space missions. When aerospace vehicles conduct cross-domain flights near near space, they experience two different flight environments—one inside and one outside the atmosphere. To improve their adaptability, the concept of "variable vehicles" has been proposed. This involves applying actuators and sensors to the vehicle, smoothly and actively altering its aerodynamic shape to change its aerodynamic performance, thereby adapting to different flight conditions, expanding the flight envelope, optimizing handling characteristics, reducing drag, increasing range, and reducing or even eliminating the effects of flutter, eddy current interference, and buffeting, thus achieving flight and launch functions more efficiently. To address different spacecraft missions and design requirements, it is necessary to design an actuation mechanism for near-space spacecraft during cross-domain processes, which can be used to adjust the aerodynamic shape of the spacecraft and improve its cross-domain adaptability and variable-state flight performance.

[0003] Currently, most variator aircraft are designed around the wings, with limited research on nose cone variability. However, during flight, even minor changes in shape can significantly impact the overall aerodynamic performance, crucial for maintaining attitude control and flight stability. The shape and attitude of the nose cone also greatly influence flight characteristics. Therefore, nose cone adjustment mechanisms are essential in variator aircraft. Existing nose cone variator designs primarily employ complex mechanisms with multiple redundant degrees of freedom. While these mechanisms can accommodate changes in nose cone angle and extension length, providing greater flexibility, the redundant degrees of freedom increase control complexity. Furthermore, the nose cone's weight, located at the tip, directly affects overall maneuverability, increases launch costs and fuel consumption, and these complex mechanisms with redundant degrees of freedom do not meet lightweight design requirements, hindering performance optimization for next-generation near-space vehicles. Summary of the Invention

[0004] The technical problem solved by this invention is to overcome the shortcomings of existing technologies and provide an adjustable nose cone for a near-space vehicle and its adjustment method. This allows for adjustments to the vehicle's configuration, enabling it to change its aerodynamic structure in mid-air and addressing the problem that traditional fixed-configuration vehicles struggle to cope with the drastic changes in the flight environment faced by near-space vehicles during cross-domain flights.

[0005] The solution to the technical problem of the present invention is: an adjustable nose cone for a near-space vehicle, the adjustable nose cone comprising a first-stage actuator, a second-stage actuator, a third-stage actuator, a nose cone shell, and a nose cone skin;

[0006] The nose cone skin covers the outside of the nose cone shell, which supports the first-stage actuator, the second-stage actuator, the third-stage actuator, and the nose cone skin, providing structural support for the nose cone skin.

[0007] The first-stage actuator, the second-stage actuator, and the third-stage actuator are connected in series. They can all extend and retract along the central axis of the aircraft's nose cone and deflect at a preset angle relative to the central axis of the aircraft's nose cone, making the nose cone angle and extension length adjustable.

[0008] Preferably, the first-stage actuator, the second-stage actuator, and the third-stage actuator are 3-SPS / SP parallel mechanisms.

[0009] Preferably, the 3-SPS / SP parallel mechanism includes an upper connecting plate, a lower connecting plate, ball joints S1, S2, S3, S4, S5, S6, and S7, and sliding joints P1, P2, P3, and P4.

[0010] Spherical joints S1, S2, and S3 are installed on the lower connecting plate to form a lower triangle; Spherical joints S4, S5, and S6 are installed on the lower connecting plate to form an upper triangle; when the upper connecting plate is parallel to the lower connecting plate, the upper triangle is similar to the lower triangle, and the corresponding three sides are parallel to each other;

[0011] Sliding joint P1 connects ball joint S1 and ball joint S4; sliding joint P2 connects ball joint S2 and ball joint S5; sliding joint P3 connects ball joint S3 and ball joint S6;

[0012] One end of the movable joint P1 is connected to the incenter of the upper triangle via the ball joint S7, and the other end is fixedly connected to the incenter of the lower triangle.

[0013] Preferably, the sliding pairs P1, P2, P3, and P4 have the same structure, including a lower connecting rod, an upper connecting rod, and a driver. Each driver includes a hydraulic cylinder, a push rod, a piston, and a seal. The lower connecting rod connects the ball joint on the lower connecting plate to the hydraulic cylinder, and the upper connecting rod connects the ball joint on the upper connecting plate to the piston. The hydraulic cylinder and the piston are connected in a mating manner. The seal provides a gas-liquid seal between the hydraulic cylinder and the piston. The hydraulic cylinder outputs a linear thrust, which acts on the piston. The linear thrust is on the same axis as the upper and lower connecting rods, and the piston reciprocates linearly along the hydraulic cylinder.

[0014] Preferably, each driver is provided with an encoder to provide length measurement of the moving pair.

[0015] Preferably, the aircraft nose cone shell and the aircraft nose cone skin are made of flexible materials.

[0016] Preferably, the first-stage actuator, the second-stage actuator, and the third-stage actuator simultaneously actuate the head cone, and the elongation and angle provided by each stage actuator are determined by the length ratio of each stage actuator before adjustment.

[0017] Preferably, the adjustment angle of the i-th stage actuator is calculated as follows:

[0018] The adjustment angle of the i-th stage actuator = desired adjustment angle × Li / (L1+L2+L3), i = 1~3;

[0019] Where Li is the length of the i-th stage actuator before adjustment.

[0020] Preferably, the adjustment angle of the i-th stage actuator is calculated as follows:

[0021] The adjustment length of the i-th stage actuator = desired adjustment length × Li / (L1+L2+L3), i = 1~3;

[0022] Where Li is the length of the i-th stage actuator before adjustment.

[0023] Another technical solution of the present invention is: the adjustment method of the adjustable nose cone of the above-mentioned near-space spacecraft, the method comprising the following steps:

[0024] S1. The upper connecting plate of the first-stage actuator, the second-stage actuator, and the third-stage actuator is designated as the end effector, and the lower connecting plate is designated as the base. A moving coordinate system is established on the end effector, and a static coordinate system is established on the base.

[0025] S2. Based on the desired adjustment length and angle of the aircraft nose cone, and the current position and attitude relationship between the end effector and the base, calculate the required length and angle adjustment amounts for each stage of the actuator;

[0026] S3. Based on the length and angle adjustment required by each stage of the actuator, calculate the desired position and attitude relationship between the end effector of each stage of the actuator and the base. The desired position and attitude relationship is described as the mapping transformation matrix between the moving coordinate system and the static coordinate system.

[0027] S4. Based on the mapping transformation matrix between the moving coordinate system and the static coordinate system and the geometric model description matrix, the inverse kinematics solution is performed using the Newton-Raphson method to obtain the extension or retraction of each actuator in each stage of the actuator in order to make the end effector reach the expected position and attitude, and control each actuator to perform the corresponding action.

[0028] S5. Based on the lengths of each moving pair fed back by the encoders on each driver of each actuator, perform forward kinematics calculations to obtain the actual attitude of the end effector of each actuator. Based on the actual attitude of the end effector of each actuator, calculate the actual adjustment length and adjustment angle of the aircraft nose cone.

[0029] S6. Based on the actual adjustment length and angle of the aircraft nose cone and the expected adjustment length and angle of the aircraft nose cone, calculate the difference in length and angle of the aircraft nose cone. If the difference in length and angle of the nose cone are both less than their respective preset thresholds, then the process ends; otherwise, use the difference in length and angle of the nose cone as the expected adjustment length and adjustment angle of the aircraft nose cone, and repeat steps S2 to S6.

[0030] The advantages of this invention compared to the prior art are:

[0031] (1) This invention uses a 3-SPS / SP parallel mechanism as an actuator, which changes the traditional actuator transmission method. Due to the characteristics of its parallel mechanism, it has higher adjustment accuracy and stability, and improves the accuracy and reliability of adjustment.

[0032] (2) By combining the three-stage actuator with the segmented shell of the aircraft nose cone, the present invention can select multiple actuators to simultaneously provide actuation to the nose cone position, which increases the fault tolerance of the mechanism and reduces the identification and execution error of a single system. The multi-stage hierarchical adjustment configuration also improves the flexibility of the aircraft nose cone adjustment.

[0033] (3) By adopting a configuration with fewer degrees of freedom, this invention overcomes the control difficulties caused by traditional redundant degree-of-freedom mechanisms to a certain extent, which is conducive to the rapid control of the nose cone adjustment mechanism. At the same time, by adopting a configuration with fewer degrees of freedom, the weight of the aircraft nose cone and the complexity of the mechanism are reduced while meeting the motion requirements for nose cone adjustment, making the device more widely applicable. Attached Figure Description

[0034] Figure 1 This is a schematic diagram illustrating the head cone deformation principle of an embodiment of the present invention;

[0035] Figure 2 This is a schematic diagram of the overall system composition according to an embodiment of the present invention;

[0036] Figure 3 is a schematic diagram of the operation flow of the head cone adjustment device according to an embodiment of the present invention;

[0037] Figure 4 This is a comparison diagram of the actuation mechanism and the simplified mechanism in an embodiment of the present invention. Detailed Implementation

[0038] The present invention will be further described below with reference to the embodiments.

[0039] This invention provides an adjustable nose cone for a near-space vehicle and its adjustment method. The adjustable nose cone is a parallel structure with fewer than six degrees of freedom. In kinematics, a rigid body typically has six degrees of freedom. However, in practical applications, too many degrees of freedom complicate control and mechanism stiffness design. Parallel structures with fewer degrees of freedom enhance the advantages of partial degree-of-freedom actuation, facilitating kinematic calculations and actuation. This invention adjusts the expected adjustment amount in stages to modify the nose cone attitude of the vehicle, thereby altering its aerodynamic characteristics and flight attitude.

[0040] like Figure 1 The diagram illustrates the windward load on the nose cone of an aircraft and the possible airborne load after modification. The modification includes two scenarios: one where the nose cone's original length L is increased by ΔLx; and another where the nose cone deviates by a certain angle, resulting in a distance ΔLy between the apex of the nose cone and the central axis.

[0041] like Figure 2 As shown, the adjustable nose cone of a near-space vehicle provided by the present invention includes a first-stage actuator, a second-stage actuator, a third-stage actuator, a nose cone shell, a nose cone skin, a power supply, and an integrated controller.

[0042] The nose cone skin covers the outside of the nose cone shell, which provides aerodynamic and thermal support, supports the first-stage actuator, second-stage actuator, third-stage actuator and the nose cone skin, provides structural support for the nose cone skin, and is the direct load-bearing component on the windward side.

[0043] The first-stage actuator, the second-stage actuator, and the third-stage actuator are connected in series. They can all extend and retract along the central axis of the aircraft's nose cone and deflect at a preset angle relative to the central axis of the aircraft's nose cone, making the nose cone angle and extension length adjustable.

[0044] The power supply is used to power the actuators at all levels and the integrated controller, and to provide the actuator drive power.

[0045] The integrated controller receives the nose cone adjustment command sent by the aircraft's central control unit, performs forward and inverse kinematic calculations on the encoder measurement results and the adjustment angle input from the external source, and implements drive control of the actuators based on the central control command. It implements drive control for the first-stage, second-stage, and third-stage actuators. This component is the output unit for drive control commands and also the relay processing unit for feedback information, connecting the actuators to the host computer.

[0046] As shown in Figure 3(a), the first-stage actuator, the second-stage actuator, and the third-stage actuator are 3-SPS / SP parallel mechanisms.

[0047] As shown in Figure 3(b), the 3-SPS / SP parallel mechanism includes an upper connecting plate, a lower connecting plate, ball joints S1, S2, S3, S4, S5, S6, and S7, and sliding joints P1, P2, P3, and P4.

[0048] Spherical joints S1, S2, and S3 are installed on the lower connecting plate to form a lower triangle; Spherical joints S4, S5, and S6 are installed on the lower connecting plate to form an upper triangle; when the upper connecting plate is parallel to the lower connecting plate, the upper triangle is similar to the lower triangle, and the corresponding three sides are parallel to each other;

[0049] Sliding joint P1 connects ball joint S1 and ball joint S4; sliding joint P2 connects ball joint S2 and ball joint S5; sliding joint P3 connects ball joint S3 and ball joint S6;

[0050] One end of the movable joint P1 is connected to the incenter of the upper triangle via the ball joint S7, and the other end is fixedly connected to the incenter of the lower triangle.

[0051] The sliding pairs P1, P2, P3, and P4 have the same structure, including a lower connecting rod, an upper connecting rod, and a driver. Each driver has a hydraulic device as the driving component, including a hydraulic cylinder, a push rod, a piston, and a seal. The lower connecting rod connects the ball joint on the lower connecting plate to the hydraulic cylinder, and the upper connecting rod connects the ball joint on the upper connecting plate to the piston. The hydraulic cylinder and piston are connected to provide power to the piston. The seal provides a gas-liquid seal between the hydraulic cylinder and the piston. The hydraulic cylinder outputs a linear thrust, which acts on the piston. The linear thrust is on the same axis as the upper and lower connecting rods, and the piston reciprocates linearly along the hydraulic cylinder.

[0052] Each driver is equipped with an encoder to provide length measurement of the moving pair and to provide the actuation position.

[0053] The four actuators and seven ball joints are all joints, with the four actuators being the driving elements and the other joints and links being the driven elements, forming a parallel mechanism with a small number of degrees of freedom, having four degrees of freedom in total: three rotations and one extension.

[0054] The aircraft's nose cone shell is divided into three sections, corresponding to three actuators. The base of each actuator is fixedly connected to the end effector of the preceding actuator, and the shell skin is fastened along the connection point between the end effector and the base, forming an envelope structure.

[0055] The aircraft nose cone skin provides an external windward envelope for the mechanism, offering airtightness and forming a streamlined outer surface to reduce flight drag. Its smooth surface covers the nose cone shell, which, along with the nose cone skin, is made of a flexible material.

[0056] The first-stage actuator, the second-stage actuator, and the third-stage actuator simultaneously actuate the head cone. The elongation and angle provided by each stage actuator are determined by the length ratio of each stage actuator before adjustment.

[0057] like Figure 4 As shown, the first-stage actuator is used to adjust the angle of the nose cone's windward surface. If the nose can be deflected and has a controllable relative deflection angle with respect to the central axis, the expected lift, drag, and yaw moment can be generated by utilizing the pressure difference. By controlling the nose deflection angle and adjusting and changing the aerodynamic forces, the flight trajectory can be effectively and controllably changed, and the maneuverability of the aircraft can be improved.

[0058] The second-stage and third-stage actuators are used to further adjust the position and attitude of the first-stage actuators and change the overall length-to-width ratio of the aircraft's nose cone, which is the most significant factor affecting the aircraft's mechanical performance. The mechanism is the same as the first-stage actuator, consisting of a 3-SPS / SP parallel mechanism, with dimensions scaled accordingly based on the nose cone segment dimensions. The sum of the lengths of the three-stage actuators should equal the nose cone length.

[0059] The adjustment angle of the i-th stage actuator is calculated as follows:

[0060] The adjustment angle of the i-th stage actuator = desired adjustment angle × Li / (L1+L2+L3), i = 1~3;

[0061] Where Li is the length of the i-th stage actuator before adjustment.

[0062] The adjustment angle of the i-th stage actuator is calculated as follows:

[0063] The adjustment length of the i-th stage actuator = desired adjustment length × Li / (L1+L2+L3), i = 1~3;

[0064] Where Li is the length of the i-th stage actuator before adjustment.

[0065] For example, the adjustment angle a of the first-stage actuator is equal to the desired adjustment angle A multiplied by the ratio of the initial length l1 of the first-stage actuator to the total length of the actuator, i.e., a = A × L1 / (L1 + L2 + L3).

[0066] For parallel mechanisms, the inverse kinematics solution involves knowing the output (or attitude) of the moving platform and then deducing the input (or driving force) of the driving component. In this mechanism, when the aircraft is in level flight, a coordinate system is established with the center of the entire nose cone base as the origin, extending along the aircraft's flight direction, with the positive direction being X. For example... Figure 1 As shown, the direction from the ground to the head cone is Y, and the direction perpendicular to gravity and the flight direction is Z. The motion attitude of the moving platform (end effector) is the change in rotation and translation in the X, Y, and Z directions based on the original attitude. The four prismatic joints act as driving components, so their translation is the required input. Conversely, the correct solution requires the input. Given the input, the output value can be calculated by considering the individual motions of each series-connected single-chain component and the motion relationship after parallel connection, through an intermediate matrix transformation. Therefore, after detecting the actual driving amount of the four prismatic joints, the output value of the hydraulic piston can be successfully calculated.

[0067] Therefore, the adjustment method for the adjustable nose cone of the aforementioned near-space vehicle includes the following steps:

[0068] S1. The upper connecting plate of the first-stage actuator, the second-stage actuator, and the third-stage actuator is designated as the end effector, and the lower connecting plate is designated as the base. A moving coordinate system is established on the end effector, and a static coordinate system is established on the base.

[0069] S2. Based on the desired adjustment length and angle of the aircraft nose cone, and the current position and attitude relationship between the end effector and the base, calculate the required length and angle adjustment amounts for each stage of the actuator;

[0070] S3. Based on the length and angle adjustment required by each stage of the actuator, calculate the desired position and attitude relationship between the end effector of each stage of the actuator and the base. The desired position and attitude relationship is described as the mapping transformation matrix between the moving coordinate system and the static coordinate system.

[0071] S4. Based on the mapping transformation matrix between the moving coordinate system and the static coordinate system and the geometric model description matrix, the inverse kinematics solution is performed using the Newton-Raphson method to obtain the extension or retraction of each actuator in each stage of the actuator in order to make the end effector reach the expected position and attitude, and control each actuator to perform the corresponding action.

[0072] The geometric model description matrix is ​​a matrix that describes the inherent geometric and physical parameters of the mechanism, such as the connection between each joint and link in the kinematic chain and the length of the link. It is the mathematical expression of the mechanism model.

[0073] S5. Based on the lengths of each moving pair fed back by the encoders on each driver of each actuator, perform forward kinematics calculations to obtain the actual attitude of the end effector of each actuator. Based on the actual attitude of the end effector of each actuator, calculate the actual adjustment length and adjustment angle of the aircraft nose cone.

[0074] S6. Based on the actual adjustment length and angle of the aircraft nose cone and the expected adjustment length and angle of the aircraft nose cone, calculate the difference in length and angle of the aircraft nose cone. If the difference in length and angle of the nose cone are both less than their respective preset thresholds, then the process ends; otherwise, use the difference in length and angle of the nose cone as the expected adjustment length and adjustment angle of the aircraft nose cone, and repeat steps S2 to S6.

[0075] The preset threshold for angle is 0.1 degrees. The preset threshold for length is 0.05 mm to 0.1 mm. Repeatability or absolute positioning accuracy can also be used as iteration conditions.

[0076] The operating steps for the aforementioned parallel, low-degree-of-freedom near-space vehicle nose cone adjustment device are as follows:

[0077] All equipment is powered on and ready to go. The power supply and integrated controller receive the command to adjust the nose cone from the aircraft's central control unit. The hydraulic system begins to supply fluid to provide power to the actuators.

[0078] Initial position measurement: The encoder measures the position of each joint and sends it back to the integrated controller, which performs kinematic calculations to generate the current initial position of the head cone and completes the recording. The control system calculates the required adjustment amount based on the position of the head cone before adjustment and the target position, performs inverse kinematics, and decomposes it into the motion of each joint.

[0079] Once the actuator is activated, the integrated controller issues a command to activate the first-level actuator. The first-level actuator begins to operate, driving the joint based on the joint calculation results from the previous step, and pushing the head cone for initial adjustment.

[0080] Fine position calibration: During the process of adjusting the head cone to the middle position, the encoder sends the change in drive position length to the integrated controller to achieve real-time calibration of the drive position;

[0081] The second and third stage actuators operate according to the central control attitude adjustment requirements. The second and third stage actuators repeat the judgment process of the first stage actuator, and further adjustments are made on the basis of the adjustment of the first stage actuator to ensure that the head cone attitude and position reach the specified scalar.

[0082] Feedback and locking: Once the head cone is adjusted to the final target position, the final position is confirmed through encoder information. The control system issues a locking command to lock the actuator in the final position, ensuring the stability of the adjustment. The system records all data, including the starting position, target position, and deviation, for the next adjustment or correction. The head cone angle adjustment action ends.

[0083] In summary, this invention provides an adjustable nose cone for a near-space vehicle and its adjustment method. During the near-space vehicle's cross-domain flight, the nose cone angle and extension length are adjusted according to different flight environments to meet the "two rotations and one shift" mechanism adjustment requirements of the near-space vehicle. This adjusts the nose cone attitude, changes the aerodynamic characteristics and flight attitude of the near-space vehicle, and further improves the adaptability of the aerospace vehicle to the complex environment near near space.

[0084] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solutions of the present invention by utilizing the methods and techniques disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the protection scope of the technical solutions of the present invention.

Claims

1. An adjustable nose cone for a near-space vehicle, characterized in that, Includes the first-stage actuator, the second-stage actuator, the third-stage actuator, the nose cone shell of the aircraft, and the nose cone skin of the aircraft; The nose cone skin covers the outside of the nose cone shell, which supports the first-stage actuator, the second-stage actuator, the third-stage actuator, and the nose cone skin, providing structural support for the nose cone skin. The first-stage actuator, the second-stage actuator, and the third-stage actuator are connected in series. They can all extend and retract along the central axis of the aircraft's nose cone and deflect at a preset angle relative to the central axis of the aircraft's nose cone, making the nose cone angle and extension length adjustable.

2. The adjustable nose cone of a near-space vehicle according to claim 1, characterized in that, The first-stage actuator, the second-stage actuator, and the third-stage actuator are 3-SPS / SP parallel mechanisms.

3. The adjustable nose cone of a near-space vehicle according to claim 2, characterized in that, The 3-SPS / SP parallel mechanism includes an upper connecting plate, a lower connecting plate, ball joints S1, S2, S3, S4, S5, S6, and S7, and sliding joints P1, P2, P3, and P4. Spherical joints S1, S2, and S3 are installed on the lower connecting plate to form a lower triangle; Spherical joints S4, S5, and S6 are installed on the lower connecting plate to form an upper triangle; when the upper connecting plate is parallel to the lower connecting plate, the upper triangle is similar to the lower triangle, and the corresponding three sides are parallel to each other; Sliding joint P1 connects ball joint S1 and ball joint S4; sliding joint P2 connects ball joint S2 and ball joint S5; sliding joint P3 connects ball joint S3 and ball joint S6; One end of the movable joint P1 is connected to the incenter of the upper triangle via the ball joint S7, and the other end is fixedly connected to the incenter of the lower triangle.

4. The adjustable nose cone of a near-space vehicle according to claim 2, characterized in that, The sliding pairs P1, P2, P3, and P4 have the same structure, including a lower connecting rod, an upper connecting rod, and an actuator. Each actuator includes a hydraulic cylinder, a push rod, a piston, and a seal. The lower connecting rod connects the ball joint on the lower connecting plate to the hydraulic cylinder, and the upper connecting rod connects the ball joint on the upper connecting plate to the piston. The hydraulic cylinder and the piston are connected in a mating manner. The seal provides a gas-liquid seal between the hydraulic cylinder and the piston. The hydraulic cylinder outputs a linear thrust, which acts on the piston. The linear thrust is on the same axis as the upper and lower connecting rods, and the piston reciprocates linearly along the hydraulic cylinder.

5. The adjustable nose cone of a near-space vehicle according to claim 2, characterized in that, Each driver is equipped with an encoder to provide length measurement of the moving pair.

6. The adjustable nose cone of a near-space vehicle according to claim 1, characterized in that, The nose cone shell and nose cone skin of the aircraft are made of flexible materials.

7. The adjustable nose cone of a near-space vehicle according to claim 1, characterized in that, The first-stage actuator, the second-stage actuator, and the third-stage actuator simultaneously actuate the head cone. The elongation and angle provided by each stage actuator are determined by the length ratio of each stage actuator before adjustment.

8. The adjustable nose cone of a near-space vehicle according to claim 1, characterized in that, The adjustment angle of the i-th stage actuator is calculated as follows: The adjustment angle of the i-th stage actuator = desired adjustment angle × Li / (L1+L2+L3), i = 1~3; Where Li is the length of the i-th stage actuator before adjustment.

9. The adjustable nose cone of a near-space vehicle according to claim 1, characterized in that, The adjustment angle of the i-th stage actuator is calculated as follows: The adjustment length of the i-th stage actuator = desired adjustment length × Li / (L1+L2+L3), i = 1~3; Where Li is the length of the i-th stage actuator before adjustment.

10. The method for adjusting the adjustable nose cone of a near-space vehicle as described in claim 1, characterized in that... Includes the following steps: S1. The upper connecting plate of the first-stage actuator, the second-stage actuator, and the third-stage actuator is designated as the end effector, and the lower connecting plate is designated as the base. A moving coordinate system is established on the end effector, and a static coordinate system is established on the base. S2. Based on the desired adjustment length and angle of the aircraft nose cone, and the current position and attitude relationship between the end effector and the base, calculate the required length and angle adjustment amounts for each stage of the actuator; S3. Based on the length and angle adjustment required by each stage of the actuator, calculate the desired position and attitude relationship between the end effector of each stage of the actuator and the base. The desired position and attitude relationship is described as the mapping transformation matrix between the moving coordinate system and the static coordinate system. S4. Based on the mapping transformation matrix between the moving coordinate system and the static coordinate system and the geometric model description matrix, the inverse kinematics solution is performed using the Newton-Raphson method to obtain the extension or retraction of each actuator in each stage of the actuator in order to make the end effector reach the expected position and attitude, and control each actuator to perform the corresponding action. S5. Based on the lengths of each moving pair fed back by the encoders on each driver of each actuator, perform forward kinematics calculations to obtain the actual attitude of the end effector of each actuator. Based on the actual attitude of the end effector of each actuator, calculate the actual adjustment length and adjustment angle of the aircraft nose cone. S6. Based on the actual adjustment length and angle of the aircraft nose cone and the expected adjustment length and angle of the aircraft nose cone, calculate the difference in length and angle of the aircraft nose cone. If the difference in length and angle of the nose cone are both less than their respective preset thresholds, then the process ends; otherwise, use the difference in length and angle of the nose cone as the expected adjustment length and adjustment angle of the aircraft nose cone, and repeat steps S2 to S6.

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