Coiled extension extraterrestrial celestial body landing mechanism and design method thereof

Abstract

The invention discloses a coiling type stretching extraterrestrial celestial body landing mechanism and a design method thereof, and belongs to the technical field of machinery. Compared with a traditional landing mechanism, the landing mechanism not only can be stored in a smaller space before a spacecraft is launched, but also can be unfolded in the one-dimensional direction in the unfolding process, envelope of mechanism stretching movement is effectively reduced, and the space utilization rate is increased. Therefore, the space can be saved for one launching task, other extra load equipment can be installed, and the efficiency of the task is improved; the cross section size and the configuration of the coiled extension arm are improved, so that the weight is effectively reduced while the bearing capacity of the landing mechanism is ensured; the optimization result is obtained through a sequence planning method instead of manual modification of iterative design, and the effectiveness of the result can be ensured. Compared with a traditional coiled extension arm, the bending resistance is improved, it is guaranteed that the landing mechanism can bear landing impact in the landing stage, and safe landing of the detector is achieved.

Description

Technical Field

[0001] The invention relates to a coiled and extended extraterrestrial landing mechanism and a design method thereof, belonging to the field of mechanical technology. Background Art

[0002] The exploration of extraterrestrial objects is of great significance in revealing the origin and evolution of the universe and expanding human understanding of science, technology and life. Landing exploration can realize in-situ detection on the surface of extraterrestrial objects and obtain richer detection data. It is a common form of detection in deep space exploration missions. Currently, landing exploration can be carried out on celestial bodies such as Mercury, Mars, and the Moon in the solar system.

[0003] The soft landing of the probe is an important part to ensure the smooth progress of the extraterrestrial exploration mission. Soft landing usually uses the reverse thrust rocket to ignite and decelerate when the probe approaches the surface of the celestial body. At the same time, the probe's guidance, navigation and control system (GNC) adjusts the attitude and controls the landing speed. When the speed drops low enough, it lands on the surface of the celestial body, and the energy of the probe landing is absorbed by the buffer. At present, the commonly used buffers are mainly divided into three categories: airbag landing mechanism, damping landing mechanism and deformation landing mechanism. These buffers all have their own shortcomings. For example, the airbag is easily scratched by the gravel on the surface of the celestial body, so that the buffering effect cannot be achieved as expected; the damping and deformation landing mechanism is heavy, and it is difficult to compactly store it during the launch phase, the space utilization rate is low, and the mechanical response of the launch phase is large.

[0004] The coiled extension arm is a one-dimensional space extension mechanism with light weight and high expansion and contraction ratio. It can be stored in a short space during the launch phase of the spacecraft by means of longitudinal beam coiling. It has high space utilization rate and is currently usually used as a support mechanism for equipment such as solar wings and gravity gradient rods for satellites. However, the conventional coiled extension arm has poor bending resistance and may be crushed when subjected to landing impact loads. It has not yet been used in the design of landing mechanisms for deep space probes. Summary of the invention

[0005] The technical problem solved by the present invention is: to overcome the shortcomings of the prior art, to provide a coiled and extended extraterrestrial landing mechanism and a design method thereof, to solve the problems that the traditional landing mechanism is heavy and difficult to be compactly stored during the launch phase, and the conventional coiled and extended arm has poor bending resistance.

[0006] The technical solution of the present invention is: a coiled and extended extraterrestrial landing mechanism, comprising:

[0007] The mounting bracket is fixedly mounted on the detector structure platform;

[0008] A coiled extension arm with bending resistance, one end of which is fixedly connected to a mounting support, and the other end of which is connected to a landing pad via a universal joint; the coiled extension arm is provided with a plurality of coiled extension arms, which are evenly arranged, and each coiled extension arm includes a plurality of variable-section longitudinal beams and a plurality of cross bars; the variable-section longitudinal beam is a longitudinal load-bearing member, and its cross-sectional dimensions vary along the axial direction according to design requirements; the combination of a plurality of variable-section longitudinal beams is evenly arranged; the two ends of the cross bar are respectively fixed to adjacent variable-section longitudinal beams via hinged joints, so as to provide lateral support for the coiled extension arm; before the launch of the probe, the coiled extension arm is placed in a coiled and compressed state via a clamping rod and a pin puller; after the probe is launched into orbit and before landing and descending on an extraterrestrial body, the pin puller is ignited to unlock the clamping rod, and the coiled extension arm is unfolded; during the landing stage of the probe, the probe absorbs energy via the landing pad;

[0009] The reinforcing boss has an overall truncated cone structure and provides root support for the coiled extension arm; four threaded blind holes are evenly arranged on the lower bottom surface of the reinforcing boss and fixedly installed on the mounting support; through holes are provided in the centers of the upper and lower bottom surfaces of the reinforcing boss for installing the coiled extension arm; three threaded through holes are evenly arranged on the side surfaces of the reinforcing boss and fix the root of the coiled extension arm; a groove is dug on the upper bottom surface of the reinforcing boss according to the shape of the lower end of the hinge joint, which is used to embed and install the uppermost hinge joint of the coiled extension arm, thereby strengthening the connection between the coiled extension arm and the mounting support, thereby improving the bending resistance of the coiled extension arm.

[0010] Furthermore, the root of the variable-section longitudinal beam is thicker than the bottom.

[0011] Furthermore, the number of the variable-section longitudinal beams is three, which are arranged in the form of an equilateral triangle, and the spacing between each of the variable-section longitudinal beams is determined according to design requirements.

[0012] Furthermore, every three cross bars form a layer of triangular cross frame, and there are several layers in total; the cross bar cross-sectional area of ​​each layer of triangular cross frame is the same and is determined according to design requirements.

[0013] Furthermore, the spacing between adjacent triangular cross frames is determined according to design requirements, and the spacing between all adjacent triangular cross frames is the same.

[0014] Furthermore, the crossbar becomes thicker as it approaches the base of the coiled extension arm.

[0015] Furthermore, the two layers of crossbars closest to the bottom and middle of the coiled extension arm are thicker than the crossbars at other locations.

[0016] Furthermore, it also includes diagonal stiffening cables; the diagonal stiffening cables pass through the cable holes on the hinged joint to provide a certain pre-tightening force for the coiled extension arm after deployment, thereby increasing the rigidity of the coiled extension arm.

[0017] Furthermore, the hinged joint is V-shaped, with a through hole opened in the vertical direction at the lower end and fixedly connected to the variable-section longitudinal beam; blind holes are opened in the horizontal direction at the two upper ends, and each is fixedly connected to a cross bar.

[0018] A design method of the coiled and extended extraterrestrial landing mechanism comprises:

[0019] Step 1), according to the landing conditions of the probe, calculate the force of a single landing mechanism, analyze the moment when the landing mechanism is subjected to the maximum load during this process and record the corresponding static load;

[0020] Step 2), give the initial design of the coiled extension arm, establish the corresponding finite element model, and load the static load recorded in step 1) on the finite element model, record p = 1;

[0021] Step 3), according to the stress state and the requirements of the bending resistance and lightweight design of the landing mechanism, with the lightest structure weight as the goal, the fundamental frequency of the landing mechanism when the coiled extension arm is fully deployed, the maximum displacement of the landing pad under the static load and the maximum buckling factor as constraints, and the cross-sectional dimensions of the variable-section longitudinal beam and crossbar and the spacing between the variable-section longitudinal beam and cross frame as continuous design variables, an optimization problem model is established:

[0022]

[0023] Where X={x1,x2,...,x m} T and Y = {y1,y2,...,y n} T f(X,Y) and g are the cross-sectional size variables of the variable cross-sectional longitudinal beam and crossbar and the spacing variables of the variable cross-sectional longitudinal beam and crossbar, respectively. j (X, Y) are the objective function and the jth constraint function, respectively, j = 1,…, J0, J0 is the number of constraints; and are the upper and lower limits of the cross-sectional size variables, respectively, i = 1,…,m, m is the number of size variables; and are the upper and lower limits of the interval variables, respectively, k = 1,…,n, n is the number of interval variables;

[0024] Step 4), using finite element method to perform structural analysis and sensitivity analysis on the current coiled extension arm design;

[0025] Step 5), using the structural analysis and sensitivity analysis information obtained above, construct a sequential quadratic approximation problem of the original optimization problem model; in the pth stage, the approximation problem is:

[0026]

[0027] In the formula, (X p ,Y p ) is the known point in the pth stage, which is the solution of the approximate problem in the previous stage; d is the change of the known point in the current stage, which is also the design variable of the approximate problem; f(X p ,Y p ) and g j (X p ,Y p ) are the objective and constraint functions at the known points, and are the first-order derivative vectors of the objective and constraint functions at known points respectively; H(X p ,Y p ) is the Hessian matrix of the objective function at the known points;

[0028] Step 6), use the interior point method to solve the above approximate problem and get the optimal solution d opt , and the current known point (X p ,Y p ) According to d opt Make changes and get a new design point (X p+1 ,Y p+1 );

[0029] Step 7), if the new design point (X p+1 ,Y p+1 ) and the current point (X p ,Y p ) satisfies the preset distance range and satisfies the constraints, the approximate problem converges, and the new point is the optimal configuration and size design of the coiled extension arm; otherwise, according to the new point (X p+1 ,Y p+1 ) Modify the finite element model, record p=p+1, and return to step 4) until the approximate problem converges.

[0030] The advantages of the present invention compared with the prior art are:

[0031] 1) Compared with the traditional landing mechanism, the present invention can not only be stored in a smaller space before the launch of the spacecraft, but also be able to unfold in one dimension during the unfolding process, effectively reducing the envelope of the mechanism's extension movement and improving space utilization. This allows the present invention to save space for a launch mission and install other additional payload equipment, thereby improving the effectiveness of the mission;

[0032] 2) Compared with the conventional coiled extension arm, the present invention improves the design in terms of the cross-sectional dimensions and configuration of the coiled extension arm components, so that the weight can be effectively reduced while ensuring the carrying capacity of the landing mechanism; the optimization result is obtained through the sequence planning method rather than manual modification and iterative design, which can ensure the effectiveness of the result. Compared with the traditional coiled extension arm, the bending resistance is improved, and during the landing stage, the landing mechanism is guaranteed to withstand the landing impact, so as to achieve a safe landing of the probe. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Moreover, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0034] Figure 1 This is a state diagram of the probe's coiled and extended extraterrestrial landing mechanism during the launch phase.

[0035] Figure 2 This is a state diagram of the probe's coiled and extended extraterrestrial landing mechanism during the landing phase.

[0036] Figure 3 Design flow chart for the core of the landing mechanism - the coiled extension arm with bending resistance.

[0037] Figure 4 The overall and partial schematic diagrams of the coiled extension arm with bending resistance.

[0038] Figure 5 The schematic diagram of the installation of the reinforcing boss on the mounting support shows that the coiled extension arm supported by the reinforcing boss is hidden for the convenience of display.

[0039] Figure 6 To strengthen the boss structure diagram.

[0040] In the figure: 1. Detector structural platform; 2. Mounting support; 3. Reinforced boss; 4. Coiled extension arm with bending resistance; 5. Universal joint; 6. Landing foot pad; 7. Reverse thrust engine; 41. Variable-section longitudinal beam; 42. Cross bar; 43. Diagonal stiffening cable; 44. Articulated joint. DETAILED DESCRIPTION

[0041] In order to better understand the above technical scheme, the technical scheme of the present invention is described in detail below through the accompanying drawings and specific embodiments. It should be understood that the embodiments of the present invention and the specific features in the embodiments are detailed descriptions of the technical scheme of the present invention, rather than limitations on the technical scheme of the present invention. In the absence of conflict, the embodiments of the present invention and the technical features in the embodiments can be combined with each other.

[0042] The following is a further detailed description of a coiled extension extraterrestrial landing mechanism and a design method thereof provided by an embodiment of the present invention in conjunction with the drawings of the specification. The specific implementation method may include: a coiled extension extraterrestrial landing mechanism, comprising 6 landing mechanisms arranged in an oblique direction to maintain the landing stability of the probe; each landing mechanism is obtained by lightweighting and anti-bending optimization design of a conventional coiled extension arm to ensure that the landing mechanism has load-bearing capacity while effectively reducing weight. The coiled extension arm design with anti-bending ability is the core of the present invention, which further improves the anti-bending ability on the basis of the high expansion and contraction ratio of the conventional coiled extension arm.

[0043] 1) Install the support 2, which is fixedly connected to the detector structure platform 1, and a conventional pin puller and damper are installed inside to control the locking, release and driving of the coiled extension arm;

[0044] 2) A reinforcing boss 3, connected to the mounting support 2, having a truncated cone structure as a whole, for reinforcing the bending resistance of the root of the subsequent coiled extension arm 4;

[0045] 3) The coiled extension arm 4 with bending resistance is fixedly mounted on the mounting support 2 through the reinforcing boss 3; a conventional clamping rod is fixedly mounted on the top of the coiled extension arm 4 and locked by a pin puller in the mounting support 2, so as to compress and gather the coiled extension arm 4 during the detector launch phase; the clamping rod is simultaneously connected to the damper in the mounting support 2 through a nylon rope, so as to control the deployment speed of the coiled extension arm 4 through the damper to prevent the deployment speed of the coiled extension arm 4 from being too fast and unstable;

[0046] 4) A landing foot pad 6 connected to the coiled extension arm 4 via a universal joint 4.

[0047] like Figure 4 , the further coiled extension arm 4 with bending resistance mainly comprises:

[0048] 1) Variable cross-section longitudinal beam 41

[0049] The variable cross-section longitudinal beam 41 is a longitudinal load-bearing member of the coiled extension arm 4. The cross-sectional shape of the variable cross-section longitudinal beam 41 is circular, and the cross-sectional size changes along the axial direction, and is optimized as a variable through the sequence planning method, and the design trend is thick at the upper root and thin at the lower bottom. The coiled extension arm 4 includes three variable cross-section longitudinal beams 41, which are arranged in an equilateral triangle, and the spacing between the variable cross-section longitudinal beams 41 is optimized as a variable through the sequence planning method.

[0050] 2) Crossbar 42

[0051] The cross-section of the cross-bar 42 is circular and is installed between two adjacent variable-section longitudinal beams 41. A triangular cross-frame is formed by three cross-bars 42 and fixed to the variable-section longitudinal beam 41 through a hinge joint 44, thereby providing lateral support for the coiled extension arm 4. The cross-section size of the cross-bars 42 of each layer of triangular cross-frame is the same and is optimized as a variable by the sequence planning method. The design trend is that the cross-bars 42 closer to the root of the coiled extension arm 4 are thicker, but the cross-bars 42 of the two layers near the bottom and the middle are also thicker. The spacing between two adjacent layers of cross-frames is optimized as a variable by the sequence planning method. For the convenience of design, the spacing of all adjacent cross-frames is the same.

[0052] 3) Diagonal stiffener 43

[0053] Passing through the cable hole on the hinged joint 44, a certain pre-tightening force is provided for the coiled extension arm 4 after being deployed, thereby increasing the rigidity of the coiled extension arm 4;

[0054] 4) Articulated joint 44

[0055] The overall shape is "V", wherein the lower end of the "V" has a through hole in the vertical direction and is fixedly connected to the variable-section longitudinal beam 41, and the two upper ends of the "V" have blind holes in the horizontal direction and are each fixedly connected to a crossbar 42.

[0056] By optimizing the cross-sectional dimensions of the variable-section longitudinal beam 41 / cross bar 42 and the spacing between the variable-section longitudinal beam 41 / cross frame, the following objectives can be achieved: 1) reducing the weight of the coiled extension arm 4; 2) enhancing the bending resistance of the coiled extension arm 4, which can effectively resist the bending load during landing and avoid the coiled extension arm 4 from being crushed or failing due to bending.

[0057] In the solution provided in the embodiment of the present invention, Figure 1 As shown, a coiled extension extraterrestrial landing mechanism of the present invention comprises: a mounting support 2, a reinforcing boss 3, a coiled extension arm 4 with bending resistance, a universal joint 5, and a landing pad 6. The landing mechanism is installed on a deep space probe structure platform 1. The entire probe may include several sets of landing mechanisms to maintain the stability of the probe when it lands. The specific number can be designed according to the needs of the landing detection mission. The example in this article is 6 sets.

[0058] Each landing mechanism is composed of the components 2 to 6, and the specific installation process is: first, the mounting support 2 is installed on the detector structure platform 1, the coiled extension arm 4 is installed on the mounting support 2, and its root is strengthened by the reinforcing boss 3, and then it is tightened and fixed by the clamping rod and the pin puller, and the landing foot pad 6 is installed at the bottom of the coiled extension arm 4 through the universal joint 5.

[0059] The main working procedures of the landing mechanism after entering orbit are as follows:

[0060] 1) Before the detector is launched, the coiled extension arm 4 is placed in a coiled and retracted state by means of a clamping rod and a pin puller, thereby reducing the overall envelope size of the detector and improving the utilization of the carrying space. Figure 1 As shown;

[0061] 2) After the probe is launched into orbit and before the extraterrestrial body lands and descends, the pin puller is ignited to unlock and release the clamping rod, and the coiled extension arm 4 is unfolded, as shown in FIG. Figure 2 As shown;

[0062] 3) During the landing phase of the probe, the reverse thrust engine is ignited to decelerate, and the probe's attitude is adjusted and the landing speed is controlled under the control of the GNC. When the probe reaches a certain height above the moon, the reverse thrust engine is shut down, and the probe lands on the surface of the extraterrestrial body through the landing mechanism. During the landing process, the elastic deformation of the landing mechanism and the compression between the foot pad and the soil on the surface of the celestial body are used to cushion and absorb energy.

[0063] In the present invention, the coiled extension arm 4 needs to bear the landing impact load, which puts forward new requirements for its bending resistance. Figure 3 The steps shown are to design a coiled extension arm 4 with anti-bending performance. The design of the coiled extension arm 4 with anti-bending performance is the core of the present invention, which further designs the anti-bending capability on the basis of the high expansion and contraction ratio of the conventional coiled extension arm, which is also the main feature of the present invention that distinguishes it from the traditional landing mechanism and the conventional coiled extension arm.

[0064] The present invention uses a structural optimization technology combining a sequence planning method and a structural analysis when designing the coiled extension arm 4. The specific design steps are as follows:

[0065] 1) According to the landing conditions of the probe, calculate the force of a single landing mechanism, analyze the moment when the landing mechanism is subjected to the maximum load during this process, and record the corresponding static load;

[0066] 2) Give an initial design of the coiled extension arm 4, establish a corresponding finite element model, and load the static load recorded in step 1) on the finite element model, record p=1;

[0067] 3) According to the stress state and the requirements of the bending resistance and lightweight design of the landing mechanism, a corresponding optimization problem model is established. In the present invention, the optimization problem takes the lightest structural weight as the goal, takes the fundamental frequency of the landing mechanism when the coiled extension arm 4 is fully deployed, the maximum displacement of the landing pad 6 under the static load and the maximum buckling factor as constraints, takes the cross-sectional dimensions of the variable cross-sectional longitudinal beam 41 / cross bar 42 and the spacing of the variable cross-sectional longitudinal beam 41 / cross frame as continuous design variables, and the mathematical model of the optimization original problem is shown in formula (1):

[0068]

[0069] Where X={x1,x2,...,x m} T and Y = {y1,y2,...,y n} T f(X, Y) and g are the cross-sectional size variables of the variable cross-sectional longitudinal beam 41 / cross bar 42 and the spacing variables of the variable cross-sectional longitudinal beam 41 / cross bar 42, respectively. j (X, Y) are the objective function and the j-th constraint function (j=1,…,J0), respectively, and J0 is the number of constraints; and are the upper and lower limits of the cross-sectional size variables (i=1,…,m), and m is the number of size variables; and are the upper and lower limits of the interval variables (k=1,…,n), and n is the number of interval variables.

[0070] 4) Perform structural and sensitivity analysis on the current coiled extension arm 4 design using finite element method;

[0071] 5) Using the structural analysis and sensitivity analysis information obtained above, construct a sequential quadratic approximation problem of the original problem (1). In the pth stage, the specific form of the approximation problem is shown in formula (2):

[0072]

[0073] In the formula, (X p ,Y p ) is the known point in the pth stage, which is the solution to the approximate problem in the previous stage; d is the change in the known point in the current stage, which is also the design variable of the approximate problem (2); f(X p ,Y p ) and g j (X p ,Y p ) are the objective and constraint functions at the known points, and are the first-order derivative vectors of the objective and constraint functions at known points, respectively, and can be obtained through mature structural analysis and sensitivity analysis. p ,Y p ) is the Hessian matrix of the objective function at the known points. It is usually very difficult to solve. However, in the original problem (1), the change in the spacing between the variable-section longitudinal beams 41 / cross frames does not actually cause a change in the structural mass (i.e., the objective function). Therefore, when solving the Hessian matrix H(X p ,Y p ) only needs to be differentiated with respect to the cross-sectional dimension variable X; at this time H(X p ,Y p) can be expressed in an explicit form with respect to X and can be directly calculated;

[0074] 6) Use the interior point method to solve the above approximation problem (2) and obtain the optimal solution d opt , and the current known point (X p ,Y p ) According to d opt Make changes and get a new design point (X p+1 ,Y p+1 );

[0075] 7) If the new design point (X p+1 ,Y p+1 ) and the current point (X p ,Y p ) satisfies the preset distance range and satisfies the constraints, the sequence approximation problem converges, and the new point is the optimal configuration / size design of the coiled extension arm 4; otherwise, according to the new point (X p+1 ,Y p+1 ) Modify the finite element model, record p=p+1, and return to step 4) until the sequence approximation problem converges.

[0076] The use of the structural optimization technology enables the design process of the coiled extension arm 4 to be automated, thereby reducing the manual workload and providing a guarantee for the effectiveness of the results.

[0077] Through the above optimization design steps, a coiled extension arm 4 with bending resistance can be obtained. The design trend of the variable cross-section longitudinal beam 41 of the coiled extension arm 4 is thick at the upper root and thin at the lower bottom, thereby reducing the weight while ensuring good bending rigidity; the design trend of the cross bar 42 is that the closer to the root of the coiled extension arm 4, the thicker the cross bar 42 is, but the two layers of cross bars 42 near the bottom and the middle are also thicker, thereby providing better lateral rigidity for the thinner variable cross-section longitudinal beam 41 at the bottom of the coiled extension arm 4, and providing good lateral support in the middle of the coiled extension arm 4.

[0078] In order to further enhance the bending resistance of the coiled extension arm 4, the root of the coiled extension arm 4 is installed in the reinforcing boss 3 fixed to the mounting support 2, and the uppermost hinge 44 of the coiled extension arm 4 is embedded in the upper groove of the reinforcing boss 2, as shown in FIG. Figure 5 shown.

[0079] The structure of the reinforcement boss 3 is as follows Figure 6As shown, the whole is in the form of a truncated cone, so as to ensure that the landing mechanism has good bending resistance at its root against loads in any direction; four threaded blind holes are evenly punched on the lower bottom surface of the reinforcing boss 3, and it is fixed to the mounting bracket 2 by bolts; a through hole is punched in the center of the upper and lower bottom surfaces of the reinforcing boss 3 for installing the coiled extension arm 4; three threaded through holes are evenly punched on the side of the reinforcing boss 3, and the root of the coiled extension arm 4 is fixed by tightening bolts; a groove is dug on the upper bottom surface of the reinforcing boss 3 according to the shape of the lower end of the hinge joint 44, which is used to embed and install the uppermost hinge joint 44 of the coiled extension arm 4, so as to strengthen the connection between the coiled extension arm 4 and the mounting bracket 2, thereby further improving the bending resistance of the coiled extension arm 4.

[0080] Through the finite element analysis of the above-mentioned coiled extension arm 4, it can be known that the newly designed coiled extension arm 4 has good bending resistance, and the overall weight of the landing mechanism can be reduced by more than 25% compared with the traditional landing mechanism, indicating that this design has good advantages.

[0081] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

[0082] The contents not described in detail in the specification of the present invention belong to the common knowledge of those skilled in the art.

Claims

1. A coiled and extended extraterrestrial landing mechanism, characterized in that: include: A mounting support (2) is fixedly mounted on the detector structure platform (1); A coiled extension arm (4) with bending resistance, one end of which is fixedly connected to a mounting support (2), and the other end of which is connected to a landing pad (6) via a universal joint (5); the coiled extension arm (4) is provided with a plurality of coiled extension arms (4) which are evenly arranged, and each coiled extension arm (4) comprises a plurality of variable-section longitudinal beams (41) and a plurality of cross bars (42); the variable-section longitudinal beams (41) are longitudinal load-bearing components, and the cross-sectional dimensions thereof vary along the axial direction according to design requirements; the combination of the plurality of variable-section longitudinal beams (41) is evenly arranged. Arrangement; both ends of the crossbar (42) are respectively fixed to the adjacent variable-section longitudinal beams (41) through hinge joints (44) to provide lateral support for the coiled extension arm (4); before the probe is launched, the coiled extension arm (4) is placed in a coiled and retracted state through a clamping rod and a pin puller; after the probe is launched into orbit and before landing on an extraterrestrial body, the pin puller is ignited to unlock the clamping rod, and the coiled extension arm (4) is unfolded; during the landing stage of the probe, the probe uses a landing foot pad (6) to perform buffering and energy absorption; The reinforcing boss (3) is in the form of a truncated cone structure as a whole, and provides root support for the coiled extension arm (4); four threaded blind holes are evenly arranged on the lower bottom surface of the reinforcing boss (3), and the boss is fixedly mounted on the mounting support (2); through holes are provided in the center of the upper and lower bottom surfaces of the reinforcing boss (3), and are used to mount the coiled extension arm (4); three threaded through holes are evenly arranged on the side surface of the reinforcing boss (3), and are used to fix the root of the coiled extension arm (4); a groove is dug on the upper bottom surface of the reinforcing boss (3) according to the shape of the lower end of the hinge joint (44), and is used to embed and mount the uppermost hinge joint (44) of the coiled extension arm (4), so as to strengthen the connection between the coiled extension arm (4) and the mounting support (2), thereby improving the bending resistance of the coiled extension arm (4).

2. The coiled and extended extraterrestrial landing mechanism according to claim 1, characterized in that: The variable cross-section longitudinal beam (41) is thicker at the root than at the bottom.

3. The coiled and extended extraterrestrial landing mechanism according to claim 1, characterized in that: The number of the variable cross-section longitudinal beams (41) is three and they are arranged in an equilateral triangle. The spacing between two of the variable cross-section longitudinal beams (41) is determined according to design requirements.

4. The coiled and extended extraterrestrial landing mechanism according to claim 1, characterized in that: Every three cross bars (42) form a layer of triangular cross frame, and a total of several layers are provided; the cross bars (42) of each layer of triangular cross frame have the same cross-sectional area, which is determined according to design requirements.

5. The coiled and extended extraterrestrial landing mechanism according to claim 4, characterized in that: The spacing between adjacent triangular cross frames is determined according to design requirements, and the spacing between all adjacent triangular cross frames is the same.

6. The coiled and extended extraterrestrial landing mechanism according to claim 1, characterized in that: The closer the crossbar (42) is to the root of the coiled extension arm (4), the thicker it is.

7. The coiled and extended extraterrestrial landing mechanism according to claim 1, characterized in that: The two layers of cross bars (42) closest to the bottom and middle of the coiled extension arm (4) are thicker than the cross bars (42) at other positions.

8. The coiled and extended extraterrestrial landing mechanism according to claim 1, characterized in that: It also includes diagonal stiffening cables (43); the diagonal stiffening cables (43) pass through cable holes on the hinge joint (44) to provide a certain pre-tightening force for the coiled extension arm (4) after deployment, thereby increasing the rigidity of the coiled extension arm (4).

9. The coiled and extended extraterrestrial landing mechanism according to claim 1, characterized in that: The hinge joint (44) is V-shaped, with a through hole opened in the vertical direction at the lower end and fixedly connected to the variable-section longitudinal beam (41); and blind holes opened in the horizontal direction at the two upper ends and each fixedly connected to a crossbar (42).

10. A design method for a coiled and extended extraterrestrial landing mechanism as claimed in any one of claims 1 to 9, characterized in that: include: Step 1: Calculate the force of a single landing mechanism according to the landing conditions of the probe, analyze the moment when the landing mechanism is subjected to the maximum load during this process, and record the corresponding static load; Step 2, give an initial design of the coiled extension arm (4), establish a corresponding finite element model, and load the static load recorded in step 1 on the finite element model, record p=1; Step 3, according to the stress state and the requirements of the bending resistance and lightweight design of the landing mechanism, with the lightest structure weight as the goal, the fundamental frequency of the landing mechanism when the coiled extension arm (4) is fully deployed, the maximum displacement of the landing pad (6) under the static load and the maximum buckling factor as constraints, and the cross-sectional dimensions of the variable-section longitudinal beam (41) and the cross bar (42) and the spacing between the variable-section longitudinal beam (41) and the cross frame as continuous design variables, an optimization problem model is established: Where X={x1,x2,...,x m } T and Y = {y1,y2,...,y n } T f(X, Y) and g are the cross-sectional size variables of the variable cross-sectional longitudinal beam (41) and the cross bar (42) and the spacing variables of the variable cross-sectional longitudinal beam (41) and the cross bar (42), respectively. j (X, Y) are the objective function and the jth constraint function, respectively, j = 1,…, J0, J0 is the number of constraints; and are the upper and lower limits of the cross-sectional size variables, respectively, i = 1,…,m, m is the number of size variables; and are the upper and lower limits of the interval variables, respectively, k = 1,…,n, n is the number of interval variables; Step 4, using finite element method to perform structural analysis and sensitivity analysis on the current coiled extension arm (4) design; Step 5, using the structural analysis and sensitivity analysis information obtained above, construct a sequential quadratic approximation problem of the original optimization problem model; In the pth stage, the approximate problem is: In the formula, (X p ,Y p ) is the known point in the pth stage, which is the solution of the approximate problem in the previous stage; d is the change of the known point in the current stage, which is also the design variable of the approximate problem; f(X p ,Y p ) and g j (X p ,Y p ) are the objective and constraint functions at the known points, and are the first-order derivative vectors of the objective and constraint functions at known points respectively; H(X p ,Y p ) is the Hessian matrix of the objective function at the known points; Step 6: Use the interior point method to solve the above approximate problem and obtain the optimal solution d opt , and the current known point (X p ,Y p ) According to d opt Make changes and get a new design point (X p+1 ,Y p+1 ); Step 7, if the new design point (X p+1 ,Y p+1 ) and the current point (X p ,Y p ) satisfies the preset distance range and satisfies the constraints, the approximate problem converges, and the new point is the optimal configuration and size design of the coiled extension arm (4); otherwise, according to the new point (X p+1 ,Y p+1 ) Modify the finite element model, record p=p+1, and return to step 4 until the approximate problem converges.

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