Unmanned vehicle-mounted stretcher and tray fixing device and design method

Abstract

The invention relates to an unmanned vehicle-mounted stretcher and tray fixing device and a design method. The unmanned vehicle-mounted stretcher and tray fixing device is characterized in that a front support, a middle support and two rear supports are fixed to an unmanned vehicle platform; the left sliding rail is fixedly arranged at the upper parts of the left ends of the front support, the middle support and the left rear support; a right sliding rail is fixedly arranged at the upper part of the right end of the front support, the upper part of the right end of the middle support and the upper part of the right rear support; left and right ends of the front cross rod are respectively connected with the left and right slide rails through slide blocks; the left and right ends of the rear cross rod are respectively connected with the left and right slide rails through slide blocks; the stretcher left front fixing seat and the stretcher right front fixing seat are fixed to the upper end of the front cross rod, and the stretcher left rear fixing seat and the stretcher right rear fixing seat are connected to stretcher sliding rails on the rear cross rod through sliding blocks respectively. The left and right front ejector rod groups are respectively connected with the left and right end sides of the front support; the left and right rear ejector rod groups are respectively connected with the left and right end sides of the middle support; ejector blocks are respectively arranged on the rear side of the front support close to the left and right ends; the tail left ejector rod set and the tail right ejector rod set are connected to the positions, close to the left end and the right end, of the middle support. The medical trolley can be used for transporting wounded personnel and medical supplies.

Description

Technical Field

[0001] The present invention relates to the field of medical transportation, and particularly to a fixing device and a design method for a stretcher and a tray on an unmanned vehicle. Technical Background

[0002] With the gradual maturity of technologies related to unmanned vehicles, unmanned medical transport vehicles have been applied at multiple medical test sites. Unmanned medical transport vehicles are mainly used for point-to-point transportation of the wounded, blood transportation, and medical supply distribution. Compared with traditional medical rescue methods, unmanned medical transport vehicles have great advantages in transportation capabilities and transportation efficiency in complex environments such as deep mountains and forests, rugged mountain roads, and high-altitude and cold regions, and can significantly improve the efficiency and success rate of medical first aid.

[0003] Currently, most unmanned medical transport vehicles use bundling methods to transport the wounded and medical supplies. This fixing method has the following problems: First, fixing the wounded in a bundling manner is likely to cause secondary injuries to the wounded; Second, there is direct contact between the wounded and the unmanned vehicle platform without shock-absorbing devices, which is likely to cause discomfort to the wounded on bumpy roads; Third, fixing rescue supplies and trays in a bundling manner takes a long time and is not firm.

[0004] In view of the above problems, it is intended to design a fixing device design method for a stretcher and a tray on an unmanned vehicle, which can meet the requirements of most scenarios of the work of unmanned medical transport vehicles and take into account reliability, efficiency, safety, and light weight. Summary of the Invention

[0005] In view of the deficiencies of the prior art, the present invention provides a fixing device and a design method for a stretcher and a tray on an unmanned vehicle.

[0006] One of the above objects of the present invention is achieved by the following technical solutions:

[0007] A fixing device for a stretcher and a tray on an unmanned vehicle, characterized in that it includes a front support, an intermediate support, two rear supports, a left slide rail, a right slide rail, a front cross bar, a rear cross bar, a right front fixing seat for the stretcher, a left front fixing seat for the stretcher, a right rear fixing seat for the stretcher, a left rear fixing seat for the stretcher, a right front top rod group, a right rear top rod group, a left front top rod group, a left rear top rod group, a tail right top rod group, and a tail left top rod group;

[0008] The front support and the middle support are arranged parallel to each other in the front-back direction transversely, and the two rear supports are respectively arranged at the rear alignment positions at the left and right ends of the middle support; the front support, the middle support and the two rear supports are all fixed to the upper end of the unmanned vehicle platform; the left slide rail is fixedly installed in the upper part of the left end of the front support, the upper part of the left end of the middle support and the upper part of the rear fixed support on the left side in the front-back direction; the right slide rail is fixedly installed in the upper part of the right end of the front support, the upper part of the right end of the middle support and the upper part of the rear fixed support on the right side in the front-back direction; the left end of the front cross bar is slidably connected to the left slide rail through a lockable left front slider, and the right end of the front cross bar is slidably connected to the right slide rail through a lockable right front slider; the left end of the rear cross bar is slidably connected to the left slide rail through a lockable left rear slider, and the right end of the rear cross bar is slidably connected to the right slide rail through a lockable right rear slider; the right front fixing seat of the stretcher and the left front fixing seat of the stretcher are fixedly installed on the upper end of the front cross bar in the left-right direction; a stretcher slide rail is fixedly installed on the upper end of the rear cross bar in the left-right direction, and the right rear fixing seat of the stretcher and the left rear fixing seat of the stretcher are respectively connected to the stretcher slide rail through a lockable stretcher right slider and a lockable stretcher left slider;

[0009] The left front ejector rod group and the right front ejector rod group are respectively connected to the side parts at the left and right ends of the front support in a left-right opposite manner, so as to clamp the front positions on the left and right sides of the tray; the left rear ejector rod group and the right rear ejector rod group are respectively connected to the side parts at the left and right ends of the middle support in a left-right opposite manner, so as to clamp the rear positions on the left and right sides of the tray; a top block is respectively arranged at the positions near the left and right ends at the rear side of the front support, and the front side of the tray is limited through the rear side surface of the top block. The tail right ejector rod group and the tail left ejector rod group are arranged in the front-back direction and are respectively connected to the positions near the left end and the right end on the middle support to press the rear side of the tray.

[0010] Moreover, the front support is composed of a front cross beam, two front vertical blocks vertically connected to the left and right ends of the front cross beam, and two front top blocks connected to the rear side of the front cross beam and the inner sides of the two front vertical blocks; the front cross beam adopts a cross beam with an L-shaped cross section, and two countersunk holes are made on the front transverse edge of the front cross beam and are fixed to the front end of the unmanned vehicle platform through screws; the front top block adopts a square top block with a hollow interior, and trapezoidal threaded holes are vertically arranged on the two front vertical blocks; the middle support is composed of a middle cross beam, two middle vertical blocks vertically connected to the left and right ends of the middle cross beam, and two vertical plates vertically connected to the inner sides of the two middle vertical blocks and the front side of the middle cross beam. Two countersunk holes are made on the middle cross beam and are fixed to the unmanned vehicle platform through screws; trapezoidal threads are vertically arranged on the two middle vertical plates on both sides of the middle support; the right front ejector rod group, the right rear ejector rod group, the left front ejector rod group, the left rear ejector rod group, the tail right ejector rod group and the tail left ejector rod group all adopt the structural form of an ejector rod and a top head fixed to the inner end of the ejector rod. Trapezoidal threads are arranged on the ejector rod and are threadedly connected to the corresponding trapezoidal threaded holes through the trapezoidal threads.

[0011] The second above-mentioned object of the present invention is achieved by the following technical solutions:

[0012] A design method for the front and rear crossbars in a fixing device for an unmanned vehicle-mounted stretcher and a tray, comprising the following steps:

[0013] S1: According to the size of the stretcher, determine the main stress points, the magnitudes of the forces on the stress points and the stress model of the front and rear crossbars, and calculate the degree of static indeterminacy of the stress model;

[0014] S2: Judge whether the degree of static indeterminacy meets the requirements for model simplification; if the structure and stress points are symmetric and the degree of static indeterminacy is greater than 0, then proceed to step S3, otherwise, there is no need to simplify the stress model and directly proceed to step S4;

[0015] S3: Simplify the stress model of the front and rear crossbars;

[0016] S4: According to the stress model and cross-sectional dimensions of the front and rear crossbars, construct a two-dimensional topological optimization grid model of the front and rear crossbars using PSHELL elements;

[0017] S5: According to the vibration frequency requirements, construct a mathematical model for the topological optimization of the front and rear crossbars;

[0018] S6: Through the topological optimization results of the front and rear crossbars, find the force transmission path, add support bars on the force transmission path, and parameterize the thickness of the support bars to complete the construction of the two-dimensional grid model for the size optimization of the front and rear crossbars;

[0019] S7: Construct a mathematical model for the size optimization of the front and rear crossbars and solve it using an improved slime mold algorithm;

[0020] S8: Obtain the optimized three-dimensional structural dimensions of the front and rear crossbars.

[0021] Moreover, in step S1, the stretcher transmits the force to the front and rear crossbars through four fixing seats, which can be equivalently regarded as applying a concentrated force at each of the four fixing seat installation points. The magnitude of the force is determined by the following formula:

[0022]

[0023] In the formula, G is the weight of the stretcher and the wounded; F is the equivalent concentrated force applied at the four fixing seat installation points:

[0024] The degree of static indeterminacy of the stress model is calculated by the following formula:

[0025] N = m - 3n

[0026] In the formula, N is the degree of static indeterminacy of the stress model; m is the number of unknowns in the stress model; n is the number of components in the stress model.

[0027] Moreover, in step S3, if the structure is symmetric and the load is also symmetric, the simplification method is as follows: cut at the axis of symmetry, take half for analysis, and replace the original rigid connection with a sliding fixed support that can provide a binding couple at the cut; if the structure is symmetric and the load is antisymmetric, the simplification method is: cut at the axis of symmetry, take half for analysis, and replace the original rigid connection with a movable hinge support at the cut.

[0028] Moreover, in step S4, the two-dimensional mesh model of the topological optimization of the front and rear crossbars is completed in the software Hypermesh, and the mesh element size is determined by the following formula:

[0029]

[0030] where s is the mesh element size of the two-dimensional mesh model of the topological optimization of the front and rear crossbars; L is the length of the front and rear crossbars.

[0031] Moreover, in step S5, the mathematical model of the topological optimization of the front and rear crossbars is:

[0032]

[0033] where volume is the volume fraction within the design domain of the two-dimensional mesh model of the topological optimization of the front and rear crossbars; d is the maximum displacement of the structure; d u is the maximum value of the maximum displacement of the structure; y is the mesh element density within the design domain of the two-dimensional mesh model of the topological optimization of the front and rear crossbars; during the topological optimization process, the maximum displacement d and the volume fraction volume of the two-dimensional mesh model of the topological optimization of the front and rear crossbars at each iteration step are calculated from the mesh element density y within the design domain of the two-dimensional mesh model of the topological optimization of the front and rear crossbars;

[0034] The maximum value d u of the maximum displacement of the two-dimensional mesh model of the topological optimization of the front and rear crossbars is determined by the following formula:

[0035] d u = 1.3 × d′

[0036] where d u is the maximum value of the maximum displacement of the two-dimensional mesh model of the topological optimization of the front and rear crossbars; d′ is the maximum displacement of the structure when the density of each element within the design domain of the two-dimensional mesh model of the topological optimization of the front and rear crossbars is 1.

[0037] Moreover, in step S6, the two-dimensional mesh model of the size optimization of the front and rear crossbars is completed in the software Hypermesh, and the mesh element size is the same as that of the two-dimensional mesh model of the topological optimization of the front and rear crossbars.

[0038] Moreover, in step S7, the mathematical model of the size optimization of the front and rear crossbars is:

[0039]

[0040] In the formula, w1 is the weight factor of the first-order bending mode frequency of the two-dimensional grid model for optimizing the dimensions of the front and rear crossbars; w2 is the weight factor of the first-order torsional mode frequency of the two-dimensional grid model for optimizing the dimensions of the front and rear crossbars; f1 is the first-order bending mode frequency of the two-dimensional grid model for optimizing the dimensions of the front and rear crossbars; f2 is the first-order torsional mode frequency of the two-dimensional grid model for optimizing the dimensions of the front and rear crossbars; mass is the weight of the two-dimensional grid model for optimizing the dimensions of the front and rear crossbars; T = [t1, t2, t3,..., t k is the design variable, that is, the thickness dimensions of each support bar; t l is the lower limit of the thickness dimension of the support bar; t u is the upper limit of the thickness dimension of the support bar; during the dimension optimization process, the first-order bending mode frequency f1 of the two-dimensional grid model for optimizing the dimensions of the front and rear crossbars, the first-order torsional mode frequency f2 of the two-dimensional grid model for optimizing the dimensions of the front and rear crossbars, and the weight mass of the two-dimensional grid model for optimizing the dimensions of the front and rear crossbars in each iteration step are calculated through the design variable T = [t1, t2, t3,..., t k .

[0041] The weight factor w1 of the first-order bending mode frequency of the two-dimensional grid model for optimizing the dimensions of the front and rear crossbars and the weight factor w2 of the first-order torsional mode frequency of the two-dimensional grid model for optimizing the dimensions of the front and rear crossbars are determined by the following formula:

[0042] w1 = 5f obj1

[0043]

[0044] In the formula, w1 is the weight factor of the first-order bending mode frequency of the two-dimensional grid model for optimizing the dimensions of the front and rear crossbars; w2 is the weight factor of the first-order torsional mode frequency of the two-dimensional grid model for optimizing the dimensions of the front and rear crossbars; f obj1 is the target value of the first-order bending mode frequency of the two-dimensional grid model for optimizing the dimensions of the front and rear crossbars, and this value is determined according to the vibration frequency requirements of the use environment; f obj2 is the target value of the first-order torsional mode frequency of the two-dimensional grid model for optimizing the dimensions of the front and rear crossbars, and this value is determined according to the vibration frequency requirements of the use environment.

[0045] Moreover, in step S7, the improved slime mold algorithm introduces a dynamic factor p1 and Gaussian-Cauchy mutation on the basis of the original algorithm; in each iteration, the update formula of the design variable T = [t1, t2, t3,..., t k is as follows:

[0046]

[0047] In the formula, T(i + 1) is the design variable in the (i + 1)-th iteration; T b(i) is the design variable with the best fitness in the i-th iteration; T A (i) and T B (i) are two groups of design variables randomly selected from the i-th iteration process; itermax is the maximum number of iterations; T(i) is the design variable in the i-th iteration; rand is a system random number, that is, a random number generated between 0 and 1; U is the upper limit of the design variable; L is the lower limit of the design variable; e1 is the first random number, e2 is the second random number, and a random number between 0 and 1 is generated randomly each time; v b is the first weight factor; W is the second weight factor; p1 is the first decision number; p2 is the second decision number;

[0048] Among them, the first decision number p1 and the second decision number p2 are determined by the following formula:

[0049]

[0050] p2 = tanh|S(i) - BF|

[0051] In the formula, itermax is the maximum number of iterations; S(i) is the fitness value corresponding to T(i) in the i-th iteration; BF is the best fitness value in the overall iteration process;

[0052] The first weight factor v b and the second weight factor W are determined by the following formula:

[0053]

[0054] SmallIndex = sort(S)

[0055] In the formula, itermax is the maximum number of iterations; r1 is a normal distribution random number, a random number generated between [0,1] and obeying the normal distribution; F w is the worst fitness value in the i-th iteration; F b is the best fitness value in the i-th iteration; SmallIndex = sort(S) represents the sorted fitness sequence value; condition represents the design variables with fitness ranking in the top 50%; else represents the design variables with fitness ranking in the bottom 50%;

[0056] After each iteration ends, the design variable corresponding to the optimal fitness needs to be subjected to Gaussian-Cauchy mutation. If the fitness corresponding to the design variable generated by Gaussian-Cauchy mutation is better, then the design variable generated by Gaussian-Cauchy mutation is used to replace the original design variable; the formula for Gaussian-Cauchy mutation is as follows:

[0057]

[0058] In the formula, is the design variable generated by the Gaussian-Cauchy mutation perturbation in the i-th iteration process; itermax is the maximum number of iterations; is the design variable corresponding to the optimal fitness in the i-th iteration process; Gauss(0,1) represents generating a number that follows the standard Gaussian distribution; Cauchy(0,1) represents generating a number that follows the standard Cauchy distribution.

[0059] Advantages and positive effects of the present invention:

[0060] 1. The fixing device for the unmanned vehicle-mounted stretcher and tray proposed in this invention patent can meet the transportation of the wounded and the transportation of medical supplies, can quickly switch the usage mode according to the transportation task, and can help the medical team save transportation time and improve the success rate of rescue in emergency rescue. When fixing medical supplies, the trapezoidal thread pressing method is adopted, which is more reliable and faster than the bundling fixing method.

[0061] 2. The fixing device and design method for the unmanned vehicle-mounted stretcher and tray proposed in this invention patent optimize the design of the relatively heavy front and rear crossbars in the whole fixing device, and focus on considering the vibration frequency of the front and rear crossbars in the optimization design, taking into account the comfort of the wounded during transportation and the lightweight of the whole fixing device.

[0062] 3. The fixing device and design method for the unmanned vehicle-mounted stretcher and tray proposed in this invention patent use a simplified force model to replace the original force model for analysis during the topology optimization process, effectively avoiding the checkerboard phenomenon in the optimization result and greatly reducing the convergence time of the topology optimization; the algorithm adopted in the size optimization process adds a dynamic adjustment factor and Gaussian-Cauchy mutation on the basis of the original slime mold algorithm, which can expand the search range at the initial stage of iteration to avoid falling into local solutions, and can accelerate the convergence to the global optimal solution at the end of iteration, improving the overall optimization efficiency. Description of the Drawings

[0063] Figure 1 is the fixing device for the unmanned vehicle-mounted stretcher and tray;

[0064] In the figure, 1: right front ejector rod; 2: right front ejector head; 3: right rear ejector rod; 4: right rear ejector head; 5: left front ejector head; 6: left front ejector rod; 7: left rear ejector head; 8: left rear ejector rod; 9: right tail ejector head; 10: right tail ejector rod; 11: left tail ejector head; 12: left tail ejector rod; 13: front support; 14: right slide rail; 15: left slide rail; 16: front cross bar; 17: shim block; 18: rear cross bar; 19: right rear slider; 20: right front slider; 21: left front slider; 22: left rear slider; 23: right stretcher slider; 24: left stretcher slider; 25: right front fixed seat of stretcher; 26: left front fixed seat of stretcher; 27: right rear fixed seat of stretcher; 28: left rear fixed seat of stretcher; 29: middle support; 30: right rear support; 31: left rear support; 32: stretcher slide rail.

[0065] Figure 2 is the front support in the fixing device of the unmanned vehicle-mounted stretcher and the tray;

[0066] In the figure, 13-1: counterbore of front support; 13-2: right threaded hole of front support; 13-3: left threaded hole of front support; 13-4: ejector block of front support; 13-5: left trapezoidal threaded hole of front support; 13-6: right trapezoidal threaded hole of front support.

[0067] Figure 3 is the middle support in the fixing device of the unmanned vehicle-mounted stretcher and the tray;

[0068] In the figure, 29-1: counterbore of middle support; 29-2: right threaded hole of middle support; 29-3: left threaded hole of middle support; 29-4: right trapezoidal threaded hole of middle support; 29-5: left trapezoidal threaded hole of middle support; 29-6: left rear trapezoidal threaded hole of middle support; 29-7: right rear trapezoidal threaded hole of middle support.

[0069] Figure 4 is the right rear support in the fixing device of the unmanned vehicle-mounted stretcher and the tray;

[0070] In the figure, 30-1: threaded hole of right rear support; 30-2: counterbore of right rear support.

[0071] Figure 5 is the left rear support in the fixing device of the unmanned vehicle-mounted stretcher and the tray;

[0072] In the figure, 31-1: threaded hole of left rear support; 31-2: counterbore of left rear support.

[0073] Figure 6 is the isometric view of the fixing device of the unmanned vehicle-mounted stretcher and the tray when loading the stretcher;

[0074] Figure 7 is the isometric view of the fixing device of the unmanned vehicle-mounted stretcher and the tray when loading the tray;

[0075] Figure 8 It is a top view when loading a tray with a fixing device for an unmanned vehicle-mounted stretcher and a tray;

[0076] Figure 9 It is a flowchart of the design method for a fixing device of an unmanned vehicle-mounted stretcher and a tray;

[0077] Figure 10 It is a force-bearing model of the front and rear crossbars;

[0078] Figure 11 It is a simplified force-bearing model of the front and rear crossbars;

[0079] Figure 12 It is a two-dimensional grid model of the topology optimization of the front and rear crossbars;

[0080] Figure 13 It is the load application situation of the topology optimization of the front and rear crossbars;

[0081] Figure 14 It is the result of the topology optimization of the front and rear crossbars;

[0082] Figure 15 It is a two-dimensional grid model of the size optimization of the front and rear crossbars;

[0083] Figure 16 It is the size represented by each design variable in the mathematical model of the size optimization of the front and rear crossbars;

[0084] Figure 17 It is an iterative convergence graph of the size optimization of the front and rear crossbars. Specific implementation manners

[0085] The technical solution of the present invention will be described in more detail below with reference to the accompanying drawings. The present invention includes but is not limited to the following embodiments.

[0086] A fixing device for an unmanned vehicle-mounted stretcher and a tray, as Figures 1 - 8As shown in the figure, the invention point is as follows: It mainly consists of a right front ejector rod 1, a right front ejector head 2, a right rear ejector rod 3, a right rear ejector head 4, a left front ejector head 5, a left front ejector rod 6, a left rear ejector head 7, a left rear ejector rod 8, a tail right ejector head 9, a tail right ejector rod 10, a tail left ejector head 11, a tail left ejector rod 12, a front support 13, a right slide rail 14, a left slide rail 15, a front cross bar 16, a heightening block 17, a rear cross bar 18, a right rear slider 19, a right front slider 20, a left front slider 21, a left rear slider 22, a stretcher right slider 23, a stretcher left slider 24, a stretcher right front fixing seat 25, a stretcher left front fixing seat 26, a stretcher right rear fixing seat 27, a stretcher left rear fixing seat 28, an intermediate support 29, a right rear support 30, a left rear support 31 and a stretcher slide rail 32. Among them, the right front ejector rod group, the right rear ejector rod group, the left front ejector rod group, the left rear ejector rod group, the tail right ejector rod group and the tail left ejector rod group are respectively formed by connecting the right front ejector rod and the right front ejector head, the right rear ejector rod and the right rear ejector head, the left front ejector head and the left front ejector rod, the left rear ejector head and the left rear ejector rod, the tail right ejector head and the tail right ejector rod, and the tail left ejector head and the tail left ejector rod.

[0087] The front support 13 is composed of a front cross beam, two front vertical blocks vertically connected to the left and right ends of the front cross beam, and two front top blocks connected to the rear sides of the front cross beam and the inner sides of the two front vertical blocks. The front cross beam adopts a cross beam with an L-shaped cross section. Two countersunk holes 13-1 are made on the front transverse edge of the front cross beam, and can be fixed to the front end of the unmanned vehicle platform through screws. The front top block adopts a square top block with a hollow interior. The intermediate support is composed of a middle cross beam, two middle vertical blocks vertically connected to the left and right ends of the middle cross beam, and two vertical plates vertically connected to the inner sides of the two middle vertical blocks and the front side of the middle cross beam. Two countersunk holes 29-1 are made on the middle cross beam, and can be fixed to the unmanned vehicle platform through screws. The right rear support 30 and the left rear support 31 are both provided with countersunk holes 30-2 and 31-2, and can be fixed to the rear end of the unmanned vehicle platform through screws.

[0088] Countersunk holes are evenly distributed on the right slide rail 14 and are fixed to the threaded hole 13-2 at the upper end of the right front vertical block of the front support, the threaded hole 29-2 at the upper end of the right middle vertical block of the intermediate support and the threaded hole 30-1 of the right rear support; Countersunk holes are evenly distributed on the left slide rail 15 and are fixed to the threaded hole 13-3 at the upper end of the left front vertical block of the front support, the threaded hole 29-3 at the upper end of the left middle vertical block of the intermediate support and the threaded hole 31-1 of the left rear support.

[0089] Through holes are provided at both ends of the front cross bar 16. Threaded holes are provided on both the right front slider 20 and the left front slider 21. Screws pass through the through holes on the front cross bar 16 and are fixed to the right front slider 20 and the left front slider 21. Through holes are provided at both ends of the rear cross bar 18. Threaded holes are provided on both the right rear slider 19 and the left rear slider 22. Screws pass through the through holes on the rear cross bar 18 and are fixed to the right rear slider 19 and the left rear slider 22. Locking knobs are provided on the sides of the right front slider 20, the left front slider 21, the right rear slider 19 and the left rear slider 22, and can be locked at any position on the slide rail. The heightening block 17 is fixed to the front cross bar 16 by welding. The right front stretcher fixing seat 25 and the left front stretcher fixing seat 26 are fixed to the heightening block 17 by screws. Countersunk holes are evenly distributed on the stretcher slide rail 32, and the stretcher slide rail 32 can be fixed to the rear cross bar 18 by screws. The stretcher right slider 23 and the stretcher left slider 24 are placed on the stretcher slide rail. The right rear stretcher fixing seat 27 is fixed to the stretcher right slider 23 by screws, and the left rear stretcher fixing seat 28 is fixed to the stretcher left slider 24 by screws. Locking knobs are provided on the sides of the stretcher right slider 23 and the stretcher left slider 24, and can be locked at any position on the slide rail. Trapezoidal threaded holes 13-5 and 13-6 are vertically provided on the front vertical blocks on both sides of the front support 13. The right front ejector rod 1 and the right rear ejector rod 3 pass through the trapezoidal threaded holes 13-5 and 13-6 respectively. The end faces of the right front ejector rod 1 and the right rear ejector rod 3 are fixed to the right front ejector head 2 and the left front ejector head 5 by threads respectively. Trapezoidal threaded holes 29-5 and 29-4 are provided on the middle vertical plates on both sides of the middle support 29. The right rear ejector rod 3 and the left rear ejector rod 8 pass through the trapezoidal threaded holes 29-5 and 29-4 respectively. The end faces of the right rear ejector rod 3 and the left rear ejector rod 8 are fixed to the right rear ejector head 4 and the left rear ejector head 7 by threads respectively. Trapezoidal threads 29-6 and 29-7 are vertically provided on the two side vertical plates of the middle support 29. The tail left ejector rod 12 and the tail right ejector rod 10 pass through the trapezoidal threaded holes 29-6 and 29-7 respectively. The end faces of the tail left ejector rod 12 and the tail right ejector rod 10 are fixed to the tail left ejector head 11 and the tail right ejector head 9 by threads respectively. By rotating each ejector rod, the moving displacement of the ejector rod can be controlled.

[0090] As attached Figure 6As shown in the figure, when it is necessary to fix the stretcher, loosen the locking knobs on the sides of the right front slider 20, left front slider 21, right rear slider 19 and left rear slider 22. Push the front crossbar 16 and rear crossbar 18 backward to the outermost ends of the right slide rail 14 and left slide rail 15. Slide the right stretcher slider 23 and left stretcher slider 24 on the stretcher slide rail 32 outward. After fixing the two lifting rods at the front end of the stretcher to the right front stretcher fixing seat 25 and left front stretcher fixing seat 26 respectively, hold the two lifting rods at the rear end of the stretcher and push forward until the front crossbar 16 reaches the outermost front ends of the right slide rail 14 and left slide rail 15. Subsequently, slide the right stretcher slider 23 and left stretcher slider 24 inward, and fix the two lifting rods at the rear end of the stretcher to the right rear stretcher fixing seat 27 and left rear stretcher fixing seat 28 respectively. Finally, tighten the locking knobs on the sides of the right front slider 20, left front slider 21, right rear slider 19, left rear slider 22, right stretcher slider 23 and left stretcher slider 24 to achieve locking.

[0091] As shown in the attachment Figures 7 - 8 As shown in the figure, when it is necessary to fix the tray, loosen the locking knobs on the sides of the right front slider 20, left front slider 21, right rear slider 19 and left rear slider 22. After pushing the front crossbar 16 and rear crossbar 18 backward to the outermost front ends of the right slide rail 14 and left slide rail 15, tighten the locking knobs on the sides of the right front slider 20, left front slider 21, right rear slider 19 and left rear slider 22. Place the tray and materials on the unmanned platform by a forklift, and push the tray to the position where it contacts the front support top block 13-4. Then, turn the right front ejector rod 1, right rear ejector rod 3, left front ejector rod 6, left rear ejector rod 8, tail right ejector rod 10 and tail left ejector rod 12 respectively, and make them move toward the tray until the top heads fix the tray.

[0092] In a fixing device for an unmanned vehicle-mounted stretcher and tray, in the usage condition of installing the stretcher, the front and rear crossbars are the main load-bearing members. For the design method of the front and rear crossbars, see Figures 9 - 17 , including the following steps:

[0093] S1: According to the size of the stretcher, determine the main stress points, the stress magnitudes at the stress points and the stress model of the front and rear crossbars, and calculate the degree of static indeterminacy of the stress model;

[0094] S2: Judge whether the degree of static indeterminacy meets the model simplification requirements. If the structure and stress points are symmetric and the degree of static indeterminacy is greater than 0, then enter step S3. Otherwise, it is not necessary to simplify the stress model, and directly enter step S4;

[0095] S3: Simplify the stress model of the front and rear crossbars;

[0096] S4: According to the stress model and cross-sectional dimensions of the front and rear crossbars, construct a two-dimensional topological optimization grid model of the front and rear crossbars using PSHELL elements;

[0097] S5: Construct a topological optimization mathematical model for the front and rear crossbars according to the vibration frequency requirements;

[0098] S6: Through the topological optimization results of the front and rear crossbars, find the force transmission path, add support bars on the force transmission path, and parameterize the thickness of the support bars to complete the construction of the two-dimensional grid model for the size optimization of the front and rear crossbars;

[0099] S7: Construct a mathematical model for the size optimization of the front and rear crossbars and solve it using an improved slime mold algorithm;

[0100] S8: Obtain the three-dimensional structural sizes of the optimized front and rear crossbars.

[0101] In step S1, since the stretcher transfers the force to the front and rear crossbars through four fixed seats, it can be equivalent to applying a concentrated force at each of the four fixed seat installation points. The magnitude of the force is determined by the following formula:

[0102]

[0103] In the formula, G is the weight of the stretcher and the wounded; F is the equivalent concentrated force applied at the four fixed seat installation points.

[0104] The degree of static indeterminacy of the force model is calculated by the following formula:

[0105] N = m - 3n

[0106] In the formula, N is the degree of static indeterminacy of the force model; m is the number of unknowns in the force model; n is the number of components in the force model.

[0107] In step S3, if the structure is symmetric and the load is also symmetric, the simplification method is: cut at the axis of symmetry, take half for analysis, and replace the original rigid connection with a sliding fixed support that can provide a constraint couple at the cut; if the structure is symmetric and the load is antisymmetric, the simplification method is: cut at the axis of symmetry, take half for analysis, and replace the original rigid connection with a movable hinge support at the cut.

[0108] In step S4, the two-dimensional grid model for the topological optimization of the front and rear crossbars is completed in the software Hypermesh. The mesh element size is determined by the following formula:

[0109]

[0110] In the formula, s is the mesh element size of the two-dimensional grid model for the topological optimization of the front and rear crossbars; L is the length of the front and rear crossbars.

[0111] In step S5, the topological optimization mathematical model for the front and rear crossbars is:

[0112]

[0113] In the formula, volume is the volume fraction within the design domain of the two-dimensional grid model for the topological optimization of the front and rear crossbars; d is the maximum displacement of the structure; d u is the maximum value of the maximum displacement of the structure; y is the grid cell density within the design domain of the two-dimensional grid model for the topological optimization of the front and rear crossbars. During the topological optimization process, the maximum displacement d and volume fraction volume of the two-dimensional grid model for the topological optimization of the front and rear crossbars at each iteration step are calculated from the grid cell density y within the design domain of the two-dimensional grid model for the topological optimization of the front and rear crossbars.

[0114] The maximum value d of the maximum displacement of the two-dimensional grid model for the topological optimization of the front and rear crossbars u is determined by the following formula:

[0115] d u = 1.3 × d'

[0116] In the formula, d u is the maximum value of the maximum displacement of the two-dimensional grid model for the topological optimization of the front and rear crossbars; d' is the maximum displacement of the structure when the density of each unit within the design domain of the two-dimensional grid model for the topological optimization of the front and rear crossbars is 1.

[0117] In step S6, the two-dimensional grid model for the size optimization of the front and rear crossbars is completed in the software Hypermesh, and the grid cell size is the same as that of the two-dimensional grid model for the topological optimization of the front and rear crossbars.

[0118] In step S7, the mathematical model for the size optimization of the front and rear crossbars is:

[0119]

[0120] In the formula, w1 is the weight factor of the first-order bending mode frequency of the two-dimensional grid model for the size optimization of the front and rear crossbars; w2 is the weight factor of the first-order torsional mode frequency of the two-dimensional grid model for the size optimization of the front and rear crossbars; f1 is the first-order bending mode frequency of the two-dimensional grid model for the size optimization of the front and rear crossbars; f2 is the first-order torsional mode frequency of the two-dimensional grid model for the size optimization of the front and rear crossbars; mass is the weight of the two-dimensional grid model for the size optimization of the front and rear crossbars; T = [t1, t2, t3,..., t k is the design variable, i.e., the thickness dimensions of each support bar; t l is the lower limit of the thickness dimension of the support bar; t u is the upper limit of the thickness dimension of the support bar. During the size optimization process, the first-order bending mode frequency f1 of the two-dimensional grid model for the size optimization of the front and rear crossbars, the first-order torsional mode frequency f2 of the two-dimensional grid model for the size optimization of the front and rear crossbars, and the weight mass of the two-dimensional grid model for the size optimization of the front and rear crossbars at each iteration step are calculated from the design variable T = [t1, t2, t3,..., t k .

[0121] The first-order bending mode frequency weight factor w1 of the two-dimensional grid model with optimized front and rear crossbar dimensions and the first-order torsional mode frequency weight factor w2 of the two-dimensional grid model with optimized front and rear crossbar dimensions are determined by the following formulas:

[0122] w1 = 5f obj1

[0123]

[0124] In the formula, w1 is the first-order bending mode frequency weight factor of the two-dimensional grid model with optimized front and rear crossbar dimensions; w2 is the first-order torsional mode frequency weight factor of the two-dimensional grid model with optimized front and rear crossbar dimensions; f obj1 is the target value of the first-order bending mode frequency of the two-dimensional grid model with optimized front and rear crossbar dimensions, and this value is determined according to the vibration frequency requirements of the use environment; f obj2 is the target value of the first-order torsional mode frequency of the two-dimensional grid model with optimized front and rear crossbar dimensions, and this value is determined according to the vibration frequency requirements of the use environment.

[0125] In step S7, the improved slime mold algorithm introduces a dynamic factor p1 and Gaussian-Cauchy mutation on the basis of the original algorithm. In each iteration, the update formula for the design variable T = [t1, t2, t3,..., t k is as follows:

[0126]

[0127] In the formula, T(i + 1) is the design variable in the (i + 1)-th iteration; T b (i) is the design variable with the best fitness in the i-th iteration; T A (i) and T B (i) are two groups of design variables randomly selected from the i-th iteration process; itermax is the maximum number of iterations; T(i) is the design variable in the i-th iteration; rand is a system random number, that is, a random number generated between 0 and 1; U is the upper limit of the design variable; L is the lower limit of the design variable; e1 is the first random number, e2 is the second random number, and a random number between 0 and 1 is generated randomly in each iteration; v b is the first weight factor; W is the second weight factor; p1 is the first decision number; p2 is the second decision number.

[0128] Among them, the first decision number p1 and the second decision number p2 are determined by the following formulas:

[0129]

[0130] p2 = tanh|S(i) - BF|

[0131] Wherein, itermax is the maximum number of iterations; S(i) is the fitness value corresponding to T(i) in the i-th iteration; BF is the best fitness value in the overall iteration process.

[0132] The first weight factor v b and the second weight factor W are determined by the following formula:

[0133]

[0134] SmallIndex = sort(S)

[0135] Wherein, itermax is the maximum number of iterations; r1 is a random number of normal distribution, and a random number obeying normal distribution is generated between [0,1]; F w is the worst fitness value in the i-th iteration; F b is the best fitness value in the i-th iteration; SmallIndex = sort(S) represents the sorted fitness sequence value; condition represents the design variables with the top 50% of fitness; else represents the design variables with the bottom 50% of fitness.

[0136] After each iteration ends, the design variables corresponding to the optimal fitness need to be subjected to Gaussian-Cauchy mutation. If the fitness corresponding to the design variables generated by Gaussian-Cauchy mutation is better, then the design variables generated by Gaussian-Cauchy mutation will replace the original design variables. The formula for Gaussian-Cauchy mutation is as follows:

[0137]

[0138] Wherein, is the design variable generated by the Gaussian-Cauchy mutation perturbation in the i-th iteration process; itermax is the maximum number of iterations; is the design variable corresponding to the optimal fitness in the i-th iteration process; Gauss(0,1) represents generating a number obeying the standard Gaussian distribution; Cauchy(0,1) represents generating a number obeying the standard Cauchy distribution.

[0139] Specifically, the present invention is illustrated by a specific implementation example of a design method for a fixing device of an unmanned vehicle-mounted stretcher and a tray.

[0140] The dummy is placed in the middle of the front and rear crossbars. The weight of the dummy and the stretcher is 80 kg. The lengths of the front and rear crossbars are both 900 mm. The first-order bending mode frequency of the front and rear crossbars needs to be above 102 Hz, and the first-order torsional mode frequency needs to be above 340 Hz. The force models of the front crossbar and the rear crossbar are the same, that is, it is sufficient to analyze the front crossbar. The front crossbar is fixed to the right front slider and the left front slider of the slider by screws, so the six degrees of freedom at both ends of the front crossbar are completely constrained, and the force model is as shown in the appendix Figure 10As shown. The equivalent concentrated force F applied at the four fixed seat mounting points:

[0141]

[0142] The degree of static indeterminacy N of the force-bearing model:

[0143] N = m - 3n = 6 - 3×1 = 3

[0144] Since the degree of static indeterminacy of the force-bearing model is greater than 0, the force-bearing model can be simplified. According to the position of the dummy placement, both the structure and the load of the force-bearing model are symmetric about the axis of symmetry at point J. The method for simplifying the force-bearing model is: cut at point J, and replace the original rigid connection with a sliding fixed connection support that can provide a binding couple at the cut. The simplification result is as shown in the appendix Figure 11 As shown.

[0145] As shown in the appendix Figure 12 As shown, during the modeling process of the two-dimensional mesh model for topology optimization of the front and rear crossbars in the software Hypermesh, the dark part is the non-design domain, and the light part is the design domain. The mesh element size is:

[0146]

[0147] As shown in the appendix Figure 13 As shown, the constraint conditions in the topology optimization of the two-dimensional mesh model for the front and rear crossbars are: constrain the six degrees of freedom of the left-end cells of the mesh boundary, constrain the displacement and rotation in the x direction, the displacement in the y direction, and the displacement and rotation in the z direction of the intermediate section J, and apply a concentrated force F = 196 N at each fixed seat mounting point.

[0148] According to the finite element calculation, when the density of each cell in the design domain of the two-dimensional mesh model for topology optimization of the front and rear crossbars is 1, the maximum displacement d′ of the structure is 0.405 mm.

[0149] The maximum value of the maximum displacement of the two-dimensional mesh model for topology optimization of the front and rear crossbars is:

[0150] d u = 1.3×d′ = 1.3×0.405 = 0.5265 mm

[0151] The mathematical model for topology optimization of the front and rear crossbars is:

[0152]

[0153] In the formula, volume is the volume fraction in the design domain of the two-dimensional mesh model for topology optimization of the front and rear crossbars; d is the maximum displacement of the structure, unit: mm; d u is the maximum value of the maximum displacement of the structure, unit: mm; y is the density of the mesh cells in the design domain of the two-dimensional mesh model for topology optimization of the front and rear crossbars.

[0154] The topology optimization results are as shown in the appendix Figure 14 As shown, it can be clearly seen that under this working condition, the force transmission paths on the front and rear crossbars. Within the design domain, the light-colored part is the main force transmission path, and support bars need to be set here to strengthen the structure strength. Taking the thickness dimension of the support bars as the design variable, dimensional optimization design is carried out. The two-dimensional mesh model for the dimensional optimization of the front and rear crossbars is completed in the software Hypermesh. The mesh element size is the same as that of the two-dimensional mesh model for the topology optimization of the front and rear crossbars, which is 1, as shown in the appendix Figure 15 as shown

[0155] According to the body vibration frequency requirements, the target value of the first-order bending mode frequency f obj1 of the two-dimensional mesh model for the dimensional optimization of the front and rear crossbars is 102 Hz; the target value of the first-order torsional mode frequency f obj2 of the two-dimensional mesh model for the dimensional optimization of the front and rear crossbars is 340 Hz. According to the actual manufacturing constraints, the lower limit t l of the thickness dimension of the support bars is 2 mm, and the upper limit t u of the thickness dimension of the support bars is 5 mm

[0156] The weight factor of the first-order bending mode frequency of the two-dimensional mesh model for the dimensional optimization of the rear crossbar is

[0157] w1 = 5f obj1 = 5×102 = 510

[0158] The weight factor of the first-order torsional mode frequency of the two-dimensional mesh model for the dimensional optimization of the front and rear crossbars is

[0159]

[0160] The mathematical model for the dimensional optimization of the front and rear crossbars is

[0161]

[0162] In the formula, f1 is the first-order bending mode frequency of the two-dimensional mesh model for the dimensional optimization of the front and rear crossbars, unit: Hz; f2 is the first-order torsional mode frequency of the two-dimensional mesh model for the dimensional optimization of the front and rear crossbars, unit: Hz; mass is the weight of the two-dimensional mesh model for the dimensional optimization of the front and rear crossbars, unit: kg; T = [t1, t2, t3,..., t 11 is the design variable, unit: mm, that is, the thickness dimensions of each support bar. The dimensions represented by the design variables are as shown in the appendix Figure 16 as shown

[0163] In the dimensional optimization of the front and rear crossbars, the maximum number of iterations itermax = 20. The convergence diagram for the dimensional optimization of the front and rear crossbars is as shown in the appendix Figure 17As shown, the optimal solution has been found at the 11th iteration, proving that the improved slime mold algorithm has good convergence in the optimization of the front and rear crossbar sizes. The optimization results of the front and rear crossbar sizes are shown in Table 1.

[0164] Table 1

[0165]

[0166]

[0167] The performance comparison between the front and rear crossbars after size optimization and the target values is shown in Table 2. The first-order bending mode frequency and the first-order torsional mode frequency of the front and rear crossbars after size optimization are both greater than the target values, proving the feasibility of the optimization results.

[0168] Table 2

[0169] Performance of front and rear crossbars After size optimization Target value First-order bending mode frequency 104.3Hz 102Hz First-order torsional mode frequency 342Hz 340Hz

[0170] The present invention is not limited to the above specific embodiments. Those of ordinary skill in the art can implement the present invention in many other specific embodiments according to the embodiments and the disclosed content of the drawings. Therefore, any design that adopts the design structure and concept of the present invention and makes some simple transformations or changes falls within the protection scope of the present invention.

Claims

1. A fixing device for an unmanned vehicle-mounted stretcher and a pallet, characterized in that: It includes a front support, a middle support, two rear supports, a left slide rail, a right slide rail, a front cross bar, a rear cross bar, a right front fixing seat of a stretcher, a left front fixing seat of a stretcher, a right rear fixing seat of a stretcher, a left rear fixing seat of a stretcher, a right front push rod group, a right rear push rod group, a left front push rod group, a left rear push rod group, a tail right push rod group and a tail left push rod group; The front support and the middle support are arranged in parallel in the transverse direction, and the two rear supports are respectively arranged at the rear aligned positions of the left and right ends of the middle support; the front support, the middle support and the two rear supports are all fixed to the upper end of the unmanned vehicle platform; the left slide rail is fixedly installed on the upper left end of the front support, the upper left end of the middle support and the upper part of the rear fixed support on the left side in the front-to-back direction; the right slide rail is fixedly installed on the upper right end of the front support, the upper right end of the middle support and the upper part of the rear fixed support on the right side in the front-to-back direction; the left end of the front cross bar is connected to the left slide by a lockable left front slider The rails are slidably connected, the right end of the front cross bar is slidably connected to the right slide rail through a lockable right front slider; the left end of the rear cross bar is slidably connected to the left slide rail through a lockable left rear slider, and the right end of the rear cross bar is slidably connected to the right slide rail through a lockable right rear slider; the right front fixing seat of the stretcher and the left front fixing seat of the stretcher are fixedly installed on the upper end of the front cross bar along the left and right directions; a stretcher slide rail is fixed on the upper end of the rear cross bar along the left and right directions, and the right rear fixing seat of the stretcher and the left rear fixing seat of the stretcher are respectively connected to the stretcher slide rail through a lockable stretcher right slider and a lockable stretcher left slider; The left front push rod group and the right front push rod group are respectively connected to the left and right sides of the front support in a left-right relative manner, so as to clamp the left and right front positions of the pallet; the left rear push rod group and the right rear push rod group are respectively connected to the left and right sides of the middle support in a left-right relative manner, so as to clamp the left and right rear positions of the pallet; a push block is respectively arranged on the rear side of the front support near the left and right ends, and the front side of the pallet is limited by the rear side of the push block, and the tail right push rod group and the tail left push rod group are arranged along the front-to-back direction and are respectively connected to the positions near the left and right ends of the middle support to press the rear side of the pallet.

2. The fixing device for the unmanned vehicle-mounted stretcher and the pallet according to claim 1, characterized in that: The front support is composed of a front crossbeam, two front upright blocks vertically connected to the left and right ends of the front crossbeam, and two front top blocks connected to the rear side of the front crossbeam and the inner side of the two front upright blocks; the front crossbeam adopts a crossbeam with an L-shaped cross section, and two countersunk holes are made on the horizontal side of the front end of the front crossbeam, which are fixed to the front end of the unmanned vehicle platform by screws; the front top block adopts a square top block with a hollow interior, and trapezoidal threaded holes are vertically arranged on the two front upright blocks; the intermediate support is composed of a middle crossbeam, two middle blocks vertically connected to the left and right ends of the middle crossbeam, and a vertical It is composed of two vertical plates directly connected to the inner sides of the two neutral blocks and the front side of the middle cross beam, and two countersunk holes are made on the middle cross beam, which are fixed to the unmanned vehicle platform by screws; trapezoidal threads are vertically arranged on the neutral plates on both sides of the middle support; the right front push rod group, the right rear push rod group, the left front push rod group, the left rear push rod group, the tail right push rod group and the tail left push rod group all adopt the structural form of a push rod and a push head fixed to the inner end of the push rod, and a trapezoidal thread is arranged on the push rod, which is threadedly connected with the corresponding trapezoidal thread hole through the trapezoidal thread.

3. A method for designing the front and rear cross bars in the fixing device of the unmanned vehicle-mounted stretcher and tray as claimed in claim 1 or 2, comprising the following steps: S1: According to the size of the stretcher, determine the main stress points of the front and rear cross bars, the magnitude of the stress points and the stress model, and calculate the static indeterminate times of the stress model; S2: Determine whether the static indeterminacy number meets the model simplification requirements; if the structure and the force point are symmetrical and the static indeterminacy number is greater than 0, proceed to step S3; otherwise, there is no need to simplify the force model and directly proceed to step S4; S3: simplified force model of front and rear crossbars; S4: Based on the force model and cross-sectional dimensions of the front and rear cross bars, a topologically optimized two-dimensional mesh model of the front and rear cross bars is constructed using PSHELL elements; S5: According to the vibration frequency requirements, the mathematical model of the front and rear crossbar topology optimization is constructed; S6: Find the force transmission path through the topology optimization results of the front and rear crossbars, add support bars on the force transmission path, parameterize the thickness of the support bars, and complete the construction of the two-dimensional mesh model for the optimization of the front and rear crossbar sizes; S7: Construct a mathematical model for optimizing the size of the front and rear crossbars and solve it using the improved slime mold algorithm; S8: Obtain the optimized three-dimensional structural dimensions of the front and rear cross bars.

4. The design method of the front and rear cross bars in the fixing device of the unmanned vehicle-mounted stretcher and tray according to claim 3 is characterized by: In step S1, the stretcher transmits force to the front and rear cross bars through four fixing seats, which is equivalent to applying a concentrated force at each of the four fixing seat installation points. The magnitude of the force is determined by the following formula: Where G is the weight of the stretcher and the injured; F is the equivalent concentrated force applied at the four fixing points: The static indeterminate degree of the load model is calculated by the following formula: N=m-3n Where N is the static indeterminate degree of the force model; m is the number of unknowns in the force model; and n is the number of components in the force model.

5. The design method of the front and rear cross bars in the fixing device of the unmanned vehicle-mounted stretcher and tray according to claim 3 is characterized by: In step S3, if the structure is symmetrical and the load is also symmetrical, the simplified method is: cut at the axis of symmetry, take half for analysis, and replace the original rigid connection with a sliding fixed support that can provide a constraint force couple at the cut; if the structure is symmetrical and the load is antisymmetric, the simplified method is: cut at the axis of symmetry, take half for analysis, and replace the original rigid connection with a movable hinge support at the cut.

6. The design method of the front and rear cross bars in the fixing device of the unmanned vehicle-mounted stretcher and tray according to claim 3 is characterized in that: In step S4, the topology optimization 2D mesh model of the front and rear crossbars is completed in the software Hypermesh, and the mesh unit size is determined by the following formula: Where s is the grid unit size of the two-dimensional grid model for topological optimization of the front and rear crossbars; L is the length of the front and rear crossbars.

7. The design method of the front and rear cross bars in the fixing device of the unmanned vehicle-mounted stretcher and tray according to claim 3 is characterized by: In step S5, the mathematical model of front and rear crossbar topology optimization is: Where volume is the volume fraction in the design domain of the two-dimensional mesh model for topology optimization of the front and rear crossbars; d is the maximum displacement of the structure; d u is the maximum value of the maximum displacement of the structure; y is the mesh unit density in the design domain of the front and rear crossbar topology optimization two-dimensional mesh model; in the topology optimization process, the maximum displacement d and volume fraction volume of the front and rear crossbar topology optimization two-dimensional mesh model of each iteration step are calculated by the mesh unit density y in the design domain of the front and rear crossbar topology optimization two-dimensional mesh model; The maximum value d of the maximum displacement of the two-dimensional mesh model of the front and rear crossbar topology optimization u Determined by the following formula: d u =1.3×d′ Where, d u is the maximum value of the maximum displacement of the front and rear cross bar topology optimization two-dimensional grid model; d′ is the maximum displacement of the structure when the density of each unit in the design domain of the front and rear cross bar topology optimization two-dimensional grid model is 1.

8. The design method of the front and rear cross bars in the fixing device of the unmanned vehicle-mounted stretcher and tray according to claim 3 is characterized in that: In step S6, the two-dimensional mesh model for optimizing the size of the front and rear cross bars is completed in the software Hypermesh, and the mesh unit size is consistent with the mesh unit size of the two-dimensional mesh model for optimizing the topology of the front and rear cross bars.

9. The design method of the front and rear cross bars in the fixing device of the unmanned vehicle-mounted stretcher and tray according to claim 3 is characterized by: In step S7, the mathematical model for optimizing the size of the front and rear crossbars is: Wherein, w1 is the weight factor of the first-order bending modal frequency of the two-dimensional mesh model of the front and rear crossbar size optimization; w2 is the weight factor of the first-order torsional modal frequency of the two-dimensional mesh model of the front and rear crossbar size optimization; f1 is the first-order bending modal frequency of the two-dimensional mesh model of the front and rear crossbar size optimization; f2 is the first-order torsional modal frequency of the two-dimensional mesh model of the front and rear crossbar size optimization; mass is the weight of the two-dimensional mesh model of the front and rear crossbar size optimization; T = [t1, t2, t3, ..., t k ] is the design variable, i.e. the thickness of each support bar; t l is the lower limit of the thickness of the support bar; t u is the upper limit of the thickness of the support bar; in the size optimization process, the first-order bending modal frequency f1 of the two-dimensional mesh model of the front and rear cross bar size optimization, the first-order torsional modal frequency f2 of the two-dimensional mesh model of the front and rear cross bar size optimization and the weight mass of the two-dimensional mesh model of the front and rear cross bar size optimization are calculated by design variables T = [t1, t2, t3, ..., t k ] calculated; The first-order bending modal frequency weight factor w1 of the two-dimensional mesh model for optimizing the size of the front and rear crossbars and the first-order torsional modal frequency weight factor w2 of the two-dimensional mesh model for optimizing the size of the front and rear crossbars are determined by the following formula: w1=5f obj1 Wherein, w1 is the weight factor of the first-order bending modal frequency of the two-dimensional mesh model with optimized front and rear crossbar sizes; w2 is the weight factor of the first-order torsional modal frequency of the two-dimensional mesh model with optimized front and rear crossbar sizes; f obj1 The target value of the first-order bending mode frequency of the two-dimensional mesh model is optimized for the size of the front and rear crossbars. This value is determined according to the vibration frequency requirements of the use environment; f obj2 The target value of the first-order torsional modal frequency of the two-dimensional mesh model is optimized for the front and rear crossbar sizes. This value is determined according to the vibration frequency requirements of the use environment.

10. The design method of the front and rear cross bars in the fixing device of the unmanned vehicle-mounted stretcher and tray according to claim 3 is characterized in that: In step S7, the improved slime mold algorithm introduces a dynamic factor p1 and Gauss-Cauchy mutation on the basis of the original algorithm; in each iteration, the design variable T = [t1, t2, t3, ..., t k The update formula of ] is as follows: Where T(i+1) is the design variable in the i+1th iteration; T b (i) is the design variable with the best fitness in the i-th iteration; T A (i) and T B (i) are two sets of design variables randomly selected from the i-th iteration process; itermax is the maximum number of iterations; T(i) is the design variable in the i-th iteration; rand is the system random number, that is, a random number generated between 0 and 1; U is the upper limit of the design variable; L is the lower limit of the design variable; e1 is the first random number, e2 is the second random number, and each iteration randomly generates a number between 0 and 1; v b is the first weight factor; W is the second weight factor; p1 is the first determination number; p2 is the second determination number; The first determination number p1 and the second determination number p2 are determined by the following formula: p2=tanh|S(i)-BF| In the formula, itermax is the maximum number of iterations; S(i) is the fitness value corresponding to T(i) in the i-th iteration; BF is the best fitness value in the overall iteration process; The first weight factor v b The second weight factor W is determined by the following formula: SmallIndex=sort(S) In the formula, itermax is the maximum number of iterations; r1 is a random number with normal distribution, which generates random numbers obeying normal distribution between [0,1]; F w is the worst fitness value in the i-th iteration; F b is the best fitness value in the i-th iteration; SmallIndex = sort (S) represents the fitness sequence value after sorting; condition represents the design variables with the top 50% fitness; else represents the design variables with the bottom 50% fitness; After each iteration, the design variable corresponding to the best fitness needs to undergo Gauss-Cauchy mutation. If the fitness corresponding to the design variable generated by Gauss-Cauchy mutation is better, the design variable generated by Gauss-Cauchy mutation will replace the original design variable. The formula of Gauss-Cauchy mutation is as follows: In the formula, is the design variable generated by the Gauss-Cauchy variation disturbance in the i-th iteration process; itermax is the maximum number of iterations; is the design variable corresponding to the optimal fitness in the i-th iteration process; Gauss(0,1) represents the number generated by the standard Gaussian distribution; Cauchy(0,1) represents the number generated by the standard Cauchy distribution.

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