An unmanned vehicle sub-frame structure, an assembling method thereof and an unmanned vehicle

Abstract

The application discloses an unmanned vehicle auxiliary frame structure, an assembling method thereof and an unmanned vehicle, and belongs to the technical field of unmanned vehicle auxiliary frame structures.

Description

Technical Field

[0001] This invention belongs to the field of automotive technology, and more specifically, relates to an unmanned vehicle subframe, its assembly method, and the unmanned vehicle itself. Background Technology

[0002] The subframe is the core load-bearing component of the vehicle chassis. It is mainly used to install components such as the suspension, steering system, and powertrain, and to transfer the chassis load to the vehicle body. The rigidity, strength, weight, and installation precision of its structure directly affect the vehicle's handling stability, NVH performance, and lightweight level.

[0003] Currently, the subframes for mass-produced passenger vehicles and commercial unmanned vehicles are mainly based on integral sheet metal welding structures and aluminum alloy one-piece profile welding structures. Both types of structures have irreconcilable technical shortcomings, with severe stress concentration at welding nodes and low fatigue durability. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing subframe beam-column welded joints, which suffer from severe stress concentration and are prone to fatigue cracks under alternating loads. The invention provides an unmanned vehicle subframe structure, its assembly method, and an unmanned vehicle that can effectively disperse welded joint stress and significantly improve fatigue durability.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The provided unmanned vehicle subframe structure is characterized by: including a base crossbeam assembly and a frame mounting crossbeam assembly connected thereto; the base crossbeam assembly includes an inner base frame, and the inner base frame is provided with a first mounting groove for mounting the frame mounting crossbeam assembly; the inner base frame is a frame structure composed of two longitudinal beams and a crossbeam connecting the two longitudinal beams; the frame mounting crossbeam assembly includes a supporting crossbeam and a frame mounting flange assembly connected to the supporting crossbeam; the supporting crossbeam is embedded in the first mounting groove.

[0006] The inner frame of the base is provided with a swing arm bracket for connecting the double wishbone and a steering tie rod fixing seat for supporting the steering tie rod; a reinforcing member is provided at the corner where the frame mounting beam assembly and the base beam assembly are connected.

[0007] Two longitudinal beams are arranged in parallel and spaced apart. The longitudinal beams are box-shaped rectangular beams, and the crossbeams are circular tube beams. The inner sidewall of the longitudinal beams is provided with mounting holes for installing the crossbeams, and both ends of the crossbeams are inserted into the mounting holes.

[0008] The support beam has a U-shaped structure, and the frame mounting flange assembly is threaded onto the end of the opening of the support beam.

[0009] The frame mounting flange assembly includes a mounting flange, which is a rectangular tube structure; the mounting flange is provided with a reinforcing flange, and both the mounting flange and the reinforcing flange are provided with internal thread mounting holes that are threaded to the support crossbeam, and are also provided with corresponding frame mounting holes and a second positioning hole, the upper end of which is a positioning welding hole.

[0010] The supporting crossbeam is a U-shaped structure made of a round tube, including a horizontal section and a vertical section; an arc transition section is provided between the horizontal section and the vertical section; the first mounting groove is an arc-shaped groove provided at both ends of the longitudinal beam, and the radius of the arc-shaped groove is the same as the outer diameter of the supporting crossbeam.

[0011] The swing arm bracket includes a swing arm bracket body, which is a U-shaped structure. The two side walls of the opening of the swing arm bracket body are provided with fork arm connection holes, which are waist-shaped holes. The two side walls of the swing arm bracket body are provided with reinforcing plates, which are provided with fork arm connection holes corresponding to the fork arm connection holes on the swing arm bracket body.

[0012] The steering tie rod mounting base includes a mounting base body, which has a U-shaped structure with the U-shaped opening facing downwards and is connected to the inner frame of the base. The two side walls of the mounting base body are arranged at an incline, and a support mounting surface is provided on the mounting base body. A tie rod mounting hole and a third positioning hole are provided on the support mounting surface.

[0013] An assembly method for an unmanned vehicle subframe structure employs a two-stage sub-assembly welding process followed by final assembly welding. The two main sub-assemblies are welded: the base crossbeam assembly and the frame mounting crossbeam assembly. The welded base crossbeam assembly is positioned within the final assembly welding fixture, and the frame mounting crossbeam assembly is aligned and fitted along the first mounting groove. The fitting weld is achieved using an intermittent welding process.

[0014] An unmanned vehicle includes the aforementioned unmanned vehicle subframe structure.

[0015] Compared with the prior art, the present invention has the following beneficial effects: the unmanned vehicle subframe structure and its assembly method and the unmanned vehicle of the present invention overcome the defects of severe stress concentration at the welded joints of the existing subframe beams and columns and easy fatigue cracks under alternating loads. It can effectively disperse the stress at the welded joints and greatly improve the fatigue durability life, and has strong practicality and good application prospects. Attached Figure Description

[0016] The following is a brief explanation of the contents depicted in the accompanying drawings and the markings therein:

[0017] Figure 1 This is a schematic diagram of the subframe structure of the unmanned vehicle of the present invention;

[0018] Figure 2 This is a schematic diagram of the base beam assembly structure of the present invention;

[0019] Figure 3 This is a schematic diagram of the inner frame structure of the base in this invention;

[0020] Figure 4 This is a schematic diagram of the frame mounting beam assembly structure in this invention;

[0021] Figure 5 This is a schematic diagram of the swing arm support structure in this invention;

[0022] Figure 6 This is a schematic diagram of the steering tie rod fixing seat structure in this invention;

[0023] Figure 7 This is a schematic diagram of the double fork arm connection in this invention;

[0024] Figure 8 This is a schematic diagram of the frame support connection structure in this invention.

[0025] The diagram is marked as follows:

[0026] 100. Inner frame of the base; 200. Swing arm bracket; 300. Support beam; 400. Frame mounting flange assembly; 500. Steering tie rod fixing seat; 600. Reinforcing member; 700. Double wishbone; 800. Frame;

[0027] 110. Longitudinal beam; 120. Crossbeam; 111. First mounting groove; 112. First positioning hole;

[0028] 210. Swing arm bracket body; 220. Reinforcing plate; 230. Fork arm connecting hole; 211. Upper overlapping surface; 212. Side overlapping surface;

[0029] 410. Mounting flange; 420. Reinforcing flange; 430. Chassis mounting hole; 440. Positioning welding hole; 450. Second positioning hole;

[0030] 510. Fixing base body; 520. Second mounting groove; 530. Pull rod mounting hole; 540. Third positioning hole. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0032] It should be noted that, unless otherwise defined, the technical or scientific terms used in this invention should have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0033] The unmanned vehicle subframe structure of this invention, such as Figure 1 As shown, the system includes a base crossbeam assembly and a frame mounting crossbeam assembly connected thereto. The base crossbeam assembly includes an inner base frame 100. The frame mounting crossbeam assembly includes two support crossbeams 300 spaced apart and connected to the inner base frame 100. A frame mounting flange assembly 400 is provided above the support crossbeams 300. The inner base frame 100 has a first mounting groove 111 for mounting the support crossbeams, and the support crossbeams 300 are snapped into the first mounting groove 111. This frame structure serves as the main load-bearing skeleton of the subframe, enhancing the overall structural strength. The mounting groove 111 for mounting the support crossbeams 300 is provided on the frame foundation. The support crossbeams 300 are embedded into the first mounting groove 111 before welding, rather than simply being directly welded in the traditional way. This structural design ensures the stability of the support connection and reduces stress concentration.

[0034] In this invention, a swing arm bracket for connecting the double wishbone is provided on the side of the inner frame 100 of the base, and a steering tie rod fixing seat for supporting and connecting the steering tie rod is provided on the inner frame 100 of the base. A reinforcing member 600 is provided at the corner where the frame mounting beam assembly and the base beam assembly connect.

[0035] In this invention, such as Figure 2 , 3 As shown, the base beam assembly is located below the subframe and serves as the main load-bearing component. The inner frame 100 of the base includes two parallel longitudinal beams 110 and a crossbeam 120 connecting the two longitudinal beams 110. This rectangular frame structure is the main load-bearing skeleton of the subframe, used to bear various static and dynamic loads from the suspension, steering system, and powertrain.

[0036] In this invention, the longitudinal beam 110 is a rectangular beam, and mounting holes for installing the crossbeam 120 are provided on the inner sidewalls of the rectangular longitudinal beam. The crossbeam 120 is a circular tube. During installation, both ends of the crossbeam 120 are inserted into the circular mounting holes on the rectangular beam to achieve clearance fit and positioning. After positioning, segmented welding is performed. The crossbeam 120 and the longitudinal beam 110 constitute a rectangular frame load-bearing structure. The use of beam structures with different structures for support and connection, followed by segmented welding, ensures structural strength while facilitating stress dispersion and avoiding stress concentration. This structural design offers better stability. The base crossbeam assembly is a modular segmented structure, composed of rectangular beam segments and circular tube beams. The rectangular tube beams and circular tube beams are pre-positioned and connected by a bevel welded through fixed circular tube holes, facilitating separate manufacturing and assembly. The circular tube and rectangular tube are fixed by through-hole welding, which reduces the wall thickness of the rectangular tube while improving torsional and bending strength, achieving lightweighting.

[0037] In this invention, such as Figure 4 As shown, the frame mounting beam assembly includes a support beam 300 and a frame mounting flange assembly 400. The support beam 300 has a U-shaped structure and can be made by bending a round or rectangular tube. A first mounting groove 111 is configured to mate with the support beam 300. During installation, a portion of the tubular structure of the support beam 300 is embedded into the first mounting groove 111, and the outline edge of the first mounting groove 111 is flush with the outer wall surface of the support beam 300.

[0038] Further optimization involves using a round tube for the support beam 300, with an arc-shaped structure corresponding to the first mounting groove. The round tube is a hollow structure, bent into a U-shape using a CNC machine tool. External threads are machined at both ends of the tube, with the threaded sections matching the assembly depth of the chassis mounting flange assembly. Segmented welding at the connection ends ensures proper positioning. Simultaneously, the threaded connection, combined with end-position welding, facilitates the maintenance and replacement of the mounting flange, reducing maintenance costs. The support beam 300 is preferably made of a U-shaped round tube, including horizontal and vertical sections; a circular arc transition section is provided between the horizontal and vertical sections. The first mounting groove 111 is an arc-shaped groove located at both ends of the longitudinal beam, with the radius of the arc-shaped groove being the same as the outer diameter of the support beam. This structure facilitates machining and forming. The support beam is installed within the first mounting groove, facilitating welding operations and providing superior stability and reduced stress concentration.

[0039] In this invention, such as Figure 4As shown, the frame mounting flange assembly 400 includes a mounting flange 410 and a reinforcing flange 420 disposed thereon. The mounting flange 410 is made by cutting a rectangular tube and has an internally threaded mounting hole that mates with the external thread on the supporting crossbeam 300 for welding. A positioning welding hole 440 is provided on the reinforcing flange 420 corresponding to the upper end of the internally threaded mounting hole on the mounting flange 410. Frame mounting holes 430 and a second positioning hole 450 are correspondingly arranged on the upper end faces of the mounting flange 410 and the reinforcing flange 420. Both ends of the mounting flange 410 have inwardly inclined cut surfaces, facilitating the installation and connection of the frame using mounting bolts passing through the frame mounting holes 430. In this invention, the frame mounting flange assembly 400 is provided with a main positioning hole, auxiliary mounting holes, and a reference positioning surface, achieving a precise connection between the subframe and the vehicle body.

[0040] In this invention, such as Figure 3 As shown, the longitudinal beam 110 has first mounting grooves 111 at both ends. The supporting crossbeam 300 is snapped into the first mounting grooves 111. The inner curvature of the first mounting groove 111 matches the outer diameter arc surface of the supporting crossbeam 300. After installation, segmented welding is performed. The longitudinal beam 110 is a rectangular beam. After the mounting grooves are opened, two contact welding edges are formed at the connection position with the circular tube wall of the supporting crossbeam. Double-sided notch welding is used to ensure the stability of the support connection and reduce stress concentration.

[0041] In this invention, positioning holes are provided on both the longitudinal beam 110 and the transverse beam 120, such as... Figure 3 As shown, the first positioning hole on the longitudinal beam 110 is used during assembly by a welding fixture positioned in the positioning hole to control the lateral span distance between the two longitudinal beams and ensure assembly accuracy.

[0042] In this invention, such as Figure 1 As shown, the control arm bracket 200 and steering tie rod mounting base 500 are mounted on the inner frame 100 of the base, manufactured using a stamping one-piece molding process. The bracket has pre-reserved standardized installation interfaces for connecting the vehicle's suspension and steering systems. This structural design offers better versatility and reduces the overall vehicle development and production costs.

[0043] In this invention, such as Figure 5The diagram shows a swing arm support 200, including a swing arm support body 210. The swing arm support body 210 has a U-shaped structure. Reinforcing plates 220 are provided on both side walls of the swing arm support body 210. Fork arm connection holes 230 are provided at corresponding positions on the reinforcing plates 220 and the swing arm support body 210. These fork arm connection holes 230 are oblong holes, with their length direction aligned with the direction of the crossbeam arrangement. The upper end of the swing arm support body 210 has an upper overlapping surface 211 extending towards the longitudinal beam, and the sides of the swing arm support body 210 have side overlapping surfaces 212 that are welded to the side walls of the longitudinal beam. The swing arm bracket body 210 is provided with positioning holes. During installation, it is positioned by welding fixtures. The welding fixtures are provided with positioning pins for positioning the inner frame 100 of the base and the swing arm bracket 200 respectively. The positioning pin of the inner frame 100 of the base is positioned into the first positioning hole 112, and the positioning pin of the swing arm bracket 200 is positioned into the positioning hole on the swing arm bracket 200. Four swing arm brackets 200 are symmetrically arranged on both sides of the longitudinal beam 110, two on each side. During assembly, the opening of the swing arm bracket 200 faces outward. The upper overlapping surface 211 of the swing arm bracket 200 overlaps with the upper end surface of the longitudinal beam, and the side overlapping surfaces 212 on both sides are in contact with the side wall of the longitudinal beam. The positioning pins are inserted into the positioning holes to achieve zero offset positioning of the swing arm bracket. The bottom of the flange is fully welded to the rectangular tube of the longitudinal beam, and the sides and top are simultaneously welded for reinforcement.

[0044] In this invention, such as Figure 6 The diagram shows a steering tie rod mounting base 500, which includes a mounting base body 510. The mounting base body 510 has a U-shaped structure with the U-shaped opening facing downwards and is connected to the inner frame 100 of the base. The two side walls of the mounting base body 510 are inclined to obtain stable support. The outer side of the lower end of the mounting base body 510 is connected to the longitudinal beam 110, and the inner side is connected to the crossbeam 120. A second mounting groove 520 is provided on the side connected to the crossbeam 120. This groove is engaged with the outer diameter of the crossbeam 120 and is welded in sections. A support mounting surface is provided on the mounting base body 510, and tie rod mounting holes 530 and third positioning holes 540 are provided on the support mounting surface. During installation, a side-mounted clamp is used to symmetrically weld the steering tie rod mounting base 500 to the outer wall of the central circular tube crossbeam to ensure symmetrical installation references for the left and right tie rods and avoid steering misalignment of the unmanned vehicle.

[0045] In this invention, such as Figure 1 As shown, a reinforcing member 600 is provided at the corner where the supporting crossbeam 300 connects to the longitudinal beam 110. One end of the reinforcing member is connected to the longitudinal beam 110, and the other end is connected to the supporting crossbeam 300. Reinforcing members 600 are provided at all four corners. A triangular support structure is formed between the supporting crossbeam 300, the longitudinal beam 110, and the reinforcing member 600. In conjunction with the position and connection relationship of the frame and the U-shaped supporting crossbeam, this reinforcing member is provided to further enhance the overall structural strength of the subframe.

[0046] The subframe structure assembly of this invention adopts a modular, prefabricated, and welded assembly production approach. All components are independently cut and formed, which greatly reduces welding deformation of large parts and is suitable for mass production on assembly lines.

[0047] The tubular main body profile is formed by cutting and shaping. The supporting crossbeam 300 is made of 4mm thick high-strength alloy steel seamless hollow round tube, which is bent into a U-shaped profile in one go using a CNC tube bending machine. External threads are machined at both ends of the tube body, and the length of the thread section matches the assembly depth of the frame mounting flange assembly 400. The longitudinal beam 110 of the inner frame 100 of the base uses 3mm high-strength box-type rectangular tube. After being cut by CNC plasma cutting, positioning holes and elliptical weight-reducing holes are punched into the side wall of the rectangular tube. The weight-reducing holes are evenly distributed along the length of the rectangular tube, and a 2mm reinforcing flange is reserved at the edge of the hole to avoid local strength reduction at the opening position. The round tube crossbeam is made of 3mm alloy steel round tube of the same grade, and the outer circles at both ends are chamfered to facilitate insertion into the round hole of the rectangular tube to achieve clearance fit and pre-positioning.

[0048] The mounting flange 410, reinforcing flange 420, and swing arm bracket 200 are made of 6mm thick high-strength steel plate by stamping, avoiding the strength defects caused by separate welded flanges. The mounting flange has multiple sets of frame mounting holes 430 and a center positioning welding hole 440. The mounting flange hole wall is tapped with internal threads, and the second positioning hole 450 is used to install the positioning pin 2. The swing arm bracket 200 is stamped and formed simultaneously on both sides. The fork arm connection hole 230 is opened on both side walls. The fork arm connection hole is a waist-shaped adjustment hole, which can slightly compensate for the size error of the suspension hard point during assembly. To further enhance the structural strength of the swing arm bracket connection, a reinforcing plate 220 is added at the connection on both sides. The reinforcing plate has a bent flange on both sides to limit the installation position of the fork arm. The steering tie rod fixing seat 500 adopts a U-shaped stamping structure, with a pre-reserved welding surface at the bottom and a mounting hole at the top for installing and connecting the steering tie rod.

[0049] The reinforcing member 600 is a right-angled triangular stiffening plate with a plate thickness of 5mm. The two right-angled sides are reserved for welding bevels, which are specifically used to reinforce the right-angle connection between the crossbeam 300 and the longitudinal beam 110 of the inner frame 100 of the base.

[0050] The locating pin on the frame mounting flange assembly 400 is made of heat-treated alloy steel bar. One end has an external thread that matches the flange's internal thread, and the other end has a tapered guide head. During vehicle assembly, it is quickly inserted into the body's reference hole to complete the positioning. After the locating pin is positioned, it is then bolted to the frame.

[0051] After all parts are processed, they are deburred, straightened and leveled, and stored according to their components to avoid damage to the assembly surfaces caused by bumps.

[0052] This invention employs a two-stage sub-assembly welding process before final assembly welding, breaking down the welding steps. This results in a smaller concentration of heat sources in each welding process, effectively controlling welding stress and deformation. The process mainly involves welding two major sub-assemblies: the base crossbeam assembly and the frame mounting crossbeam assembly.

[0053] Welding preparation of the frame mounting beam assembly: The bent U-shaped support beam is precisely positioned within a dedicated welding fixture. The fixture ensures the U-shaped opening size, and the coaxiality tolerance at both ends is controlled within ±0.2mm. First, the mounting flange 410 and reinforcing flange 420 are threaded onto both ends of the U-shaped tube. Angle limiting blocks in the fixture are used to lock the flange plane angle, preventing flange misalignment after thread pre-tightening. After pre-fixation, a composite welding process of continuous and intermittent welds is used. The main weld between the flange and the support beam tube is a continuous full weld to ensure connection strength. Intermittent welding is used around the auxiliary positioning holes on the flange side to reduce thermal deformation and residual welding stress caused by large-area continuous welding. The frame mounting flange assembly includes two types: one with a second positioning hole 450 and one without. A positioning pin is installed in the threaded hole of the second positioning hole 450, with the tapered guide head of the positioning pin facing outwards, serving as the assembly reference for the entire vehicle; the other type does not have a positioning pin and only serves as a structural load-bearing beam. After welding, a coordinate measuring machine is used to check the coaxiality and flatness of the flange positioning holes. Defective parts are sent to a calibration fixture for cold calibration. One embodiment of the invention is as follows... Figure 1 As shown, two of the four sets of frame mounting flange assemblies are equipped with locating pins.

[0054] Base beam assembly welding preparation: Two longitudinal beams 110 rectangular tubes are symmetrically placed on a welding positioning fixture, which limits the parallel spacing and end face flatness of the rectangular tubes; the two round tube beams are inserted laterally into the pre-reserved round holes on the side wall of the rectangular tubes, and the round holes and round tube beams are pre-positioned by clearance fit. After insertion, they are welded in sections around the circumference of the round holes to form a closed rectangular inner frame. Three-quarters arc notches, i.e., the first mounting grooves 111, are milled at both ends of the rectangular tubes. The arc contour is completely fitted with the outer circle of the U-shaped round tube, increasing the contact area for subsequent splicing and welding, and dispersing the weld stress. Four sets of first positioning holes 112 are reserved on the upper plane of the rectangular inner frame. Using the positioning holes as reference points, the swing arm brackets 200 are positioned and welded on them; after the swing arm brackets are welded, the steering tie rod fixing seats 500 are symmetrically welded to the outer wall of the base inner frame 100 using side hanging clamps to ensure that the installation reference of the left and right tie rods is symmetrical and to avoid the steering offset of the unmanned vehicle.

[0055] The welded base beam assembly is positioned within the final assembly welding fixture. Multiple reference positioning bosses are installed at the bottom of the fixture to constrain the length, width, and diagonal dimensions of the rectangular inner frame. The two frame mounting beam assemblies are aligned and fitted along the first mounting grooves 111 at both ends of the rectangular tube. The outer circle of the supporting beam 300 is fully fitted with the first mounting groove 111. The fitting weld still uses an intermittent welding process to reduce stress concentration in long welds. The U-shaped beam and the rectangular inner frame form four right-angle overlap areas. A reinforcing member 600 is welded to each right-angle location. The two right-angled sides of the triangular stiffener of the reinforcing member 600 are respectively fitted to the outer wall of the U-shaped tube and the upper surface of the rectangular tube. The bevels on both sides of the stiffener are fully fused, forming a high-strength, low-stress joint, solving the defects of stress concentration and fatigue cracking at the right-angle connections of traditional subframe beams and columns. After all welding processes are completed, the assembly is allowed to cool naturally; rapid water cooling is prohibited to prevent cold cracking in the welded area.

[0056] A coordinate measuring machine (CMM) is used to perform full-dimensional inspection of the subframe assembly, focusing on verifying the flange mounting hole positions, the coordinates of the hard points of the control arm flange, the mounting datum of the steering tie rod fixing seat, and the coaxiality of the vehicle assembly locating pins. All dimensional tolerances are controlled within ±0.3mm to ensure the assembly matching accuracy of the suspension, steering, and powertrain. Simultaneously, the appearance of welds is inspected to identify and eliminate welding defects such as porosity, cracks, and lack of fusion. Defective areas are repaired by welding and then re-inspected. Qualified subframes are then sent to shot peening equipment, where high-strength steel shot is used to uniformly peen both the inner and outer surfaces, eliminating residual welding tensile stress and forming a compressive stress layer on the component surface, significantly improving fatigue life under alternating loads and adapting to the complex road conditions and long-term bumpy operation of unmanned vehicles. After shot peening, a phosphate base is applied, followed by an epoxy anti-rust primer, and finally a wear-resistant and impact-resistant topcoat. Flange threaded holes and locating pin assembly surfaces are covered with protective plugs to prevent paint from clogging the threaded holes. After coating, the subframe is allowed to air dry naturally, resulting in the finished modular subframe.

[0057] In this invention, Figure 7 , Figure 8 This diagram illustrates the connection between the double wishbone 700 and the chassis 800. The prefabricated subframe is quickly connected to the autonomous vehicle's main beam via flanges and locating pins at both ends. The tapered guide head of the locating pin automatically compensates for manufacturing errors in the vehicle body, eliminating the need for repeated manual calibration. The suspension arms, stabilizer bars, steering gear, and cooling pipes are quickly bolted together using standardized flanges and bracket interfaces. When local brackets or flanges show wear or damage, the entire subframe does not need to be replaced; only the corresponding damaged modular components are disassembled and replaced individually, significantly reducing the later maintenance costs of the autonomous vehicle. Furthermore, the segmented modular structure allows for the replacement of crossbeams of different lengths and flange specifications according to different load capacities and sizes of autonomous vehicles. Vehicle adaptation can be achieved by adjusting only a few subassemblies, eliminating the need to redevelop the entire subframe and effectively shortening the vehicle iteration development cycle.

[0058] Compared with the traditional integral sheet metal subframe with the same load-bearing capacity, the subframe prepared in this embodiment has an overall weight reduction of about 21% and an increase in torsional stiffness of 18%, perfectly meeting the needs of unmanned logistics delivery vehicle chassis.

[0059] This invention relates to an unmanned vehicle subframe structure, its assembly method, and the unmanned vehicle itself. It employs a composite spatial configuration of tubular columns and crossbeams, combined with a crossbeam weight-reduction groove design. Compared to traditional all-sheet metal subframes, this achieves a 15%-25% weight reduction, resulting in significant lightweighting and effectively lowering overall vehicle energy consumption. The combination of a frame-type main structure and reinforced connecting brackets significantly improves the subframe's torsional stiffness and load-bearing capacity, better meeting the heavy-duty operating requirements of the unmanned vehicle. The structure features uniform stress distribution, effectively dispersing stress at each connection node, reducing the risk of fatigue cracking, and extending the structure's service life. The elliptical mounting hole design on the swing arm bracket compensates for manufacturing and assembly errors, ensuring the matching accuracy of suspension hard points and improving overall vehicle handling stability. Its structural design better matches segmented welding, which reduces the risk of welding deformation and facilitates modular production and maintenance, lowering manufacturing costs.

[0060] In this invention, the supporting beam 300 is provided with an arc-shaped transition section, which is formed by bending a round tube in one step using a CNC tube bending machine. The bending part of the U-shaped round tube naturally forms an arc-shaped transition section. The radius of curvature of the arc-shaped transition section is not less than 1.5 times the outer diameter of the U-shaped round tube to ensure that the stress is evenly distributed in the transition area and to eliminate the stress concentration at sharp corners caused by right-angle connections.

[0061] In this invention, the longitudinal beam 110 has 3 / 4 arc notches milled at both ends. The outline of these arc notches completely fits the outer circle of the supporting crossbeam 300, and the circumferential extension angle of the arc notches is 270°. The connection between the supporting crossbeam 300 and the longitudinal beam 110 also adopts a double-sided notch welding structure. The double-sided notches are symmetrically opened at the circumferential end of the U-shaped tube. The depth of the notches is 2-3 times the wall thickness of the U-shaped tube, and the width of the notches extends 60° to 120° along the circumferential angle of the U-shaped tube.

[0062] In this invention, the four right-angle overlapping areas formed by the supporting beam 300 and the rectangular inner frame are each fitted with a reinforcing member 600. The reinforcing member is a right-angled triangular stiffener plate with a thickness of 4mm-6mm. The two right-angled sides are respectively fitted between the supporting beam 300 and the longitudinal beam 110, and the bevels on both sides are fully fused and welded, and are symmetrically arranged circumferentially along the connection node.

[0063] The aforementioned arc-shaped transition section, circular arc notch, double-sided notch welding structure, and reinforcing components work together to form a complete low-stress connection node. The arc-shaped transition section eliminates sharp corner areas of stress concentration; the circular arc notch increases the contact area between the U-shaped tube and the rectangular tube; the double-sided notch increases the fusion area between the weld metal and the base material and disperses the welding heat input; and the triangular reinforcing rib disperses and transfers concentrated stress at the node to the surrounding base material. This four-fold synergy reduces the stress concentration factor of the connection node by more than 50% compared to traditional right-angle lap weld structures. Furthermore, the corresponding structural design and segmented welding further disperse stress.

[0064] In this invention, the structural arrangement employs a segmented, vertically arranged crossbeam structure, including a lower crossbeam 120 and a supporting crossbeam 300 connected to the longitudinal beam 110. The supporting crossbeam 300 is slightly higher than the crossbeam 120 by a certain distance. The supporting crossbeam 300 is arranged on both sides of the crossbeam 120. This is a combination design of a U-shaped crossbeam and a frame structure, which provides better structural stability. The segmented structure allows each crossbeam segment to be manufactured independently, facilitating the replacement of intermediate crossbeam segments of different lengths according to the wheelbase requirements of different vehicle models.

[0065] In this invention, the frame mounting flange assembly 400 is disposed at both ends of the supporting crossbeam 300, and is a stamped flange seat structure, specifically including a mounting flange 410 and a reinforcing flange 420. Both are provided with a main positioning hole, an auxiliary mounting hole, and a reference positioning surface to achieve a precise connection between the subframe and the body beam.

[0066] The frame mounting flange assembly 400 and the support crossbeam 300 are detachably and fixedly connected via threaded connectors. Specifically, the support crossbeam 300 has external threads machined at both ends. The mounting flange and reinforcing flange are fixed by screwing their internal threads onto the external threads at the ends of the U-shaped round tube. Simultaneously, the main weld between the flange and the round tube is a continuous full weld to ensure connection strength, while the area around the auxiliary positioning holes on the flange side uses intermittent welding to reduce thermal deformation. The detachable threaded connection method allows the end mounting base to be replaced individually if damaged, without needing to replace the entire assembly.

[0067] Currently, the subframes for mass-produced passenger vehicles and commercial unmanned vehicles mainly consist of integral sheet metal welding structures and aluminum alloy one-piece profile welding structures. Both types of structures have irreconcilable technical shortcomings.

[0068] The welded joints exhibit severe stress concentration, resulting in a low fatigue life. Traditional subframe crossbeams and longitudinal beams are directly lapped at right angles, with a single, continuous, full-welded structure. There are no transition arcs or reinforcing ribs to distribute stress at beam-column intersections. When vehicles are subjected to alternating impact loads during long-term operation, stress peaks concentrate at the weld joints, making them highly susceptible to micro-fatigue cracks. These cracks extend and expand with mileage, eventually leading to weld cracking, frame deformation, and failure, significantly shortening the chassis's service life. Furthermore, the large-area continuous full-welded structure generates substantial residual tensile stress, further increasing the probability of structural cracking.

[0069] Lightweight design and structural strength cannot be simultaneously achieved. To ensure the heavy-duty load-bearing capacity of the subframe, traditional structures must thicken the sheet metal and use solid rods, directly increasing the chassis weight. Conversely, reducing sheet metal thickness to lower weight results in a significant decrease in the subframe's bending and torsional stiffness, leading to large chassis deformation during driving, suspension hard point misalignment, and problems such as steering drift, vibration, and deterioration of NVH noise. While aluminum alloy profiles offer better weight reduction, their low load-bearing capacity cannot meet the requirements of heavy-duty logistics autonomous vehicles, limiting their applicability.

[0070] The integrated structure has extremely low modularity, resulting in high maintenance costs. Traditional subframes are integral welded structures, with suspension brackets, steering mounts, and body connecting flanges welded to the main frame as an inseparable whole. During use, if a single bracket or flange wears, deforms, or breaks, the damaged component cannot be replaced individually; the entire subframe must be disassembled and replaced, significantly increasing the maintenance costs of autonomous vehicles. Furthermore, the integrated structure prevents individual adjustments to local mounting interfaces, requiring the entire subframe to be remodeled, molded, and welded for trial production during new model development, leading to long development cycles and high R&D investment.

[0071] The poor universality of installation interfaces makes vehicle model iteration and adaptation difficult. Traditional subframe body connecting flanges and suspension mounting brackets are integrally welded structures with fixed mounting hole positions and hardpoint coordinates, which can only match chassis layout schemes of vehicles with a single wheelbase and single load capacity. When enterprises develop autonomous vehicles of different sizes and load capacities, the entire subframe structure needs to be redesigned and remolded, making it impossible to achieve the commonality and reuse of components such as brackets, crossbeams, and flanges. This lengthens the vehicle iteration development cycle, reduces the component commonality rate to less than 30%, and significantly increases the overall vehicle R&D and production costs.

[0072] This invention reduces the stress concentration factor of traditional right-angle lap weld joints by more than 50% through the design of the arc-shaped transition section supporting the crossbeam, the welded structure with notches at the ends of the supporting crossbeam and longitudinal beam, and the multiple synergies of the triangular reinforcing ribs. Simultaneously, the double-sided notch structure increases the contact area between the weld and the base material, resulting in a more uniform distribution of welding stress. Finite element simulation analysis and bench fatigue tests have verified that the fatigue life of the subframe structure of this invention is 2 to 3 times longer than that of traditional integral sheet metal subframes, effectively solving the industry-wide common problems of subframe weld cracking and frame deformation failure.

[0073] This invention employs a tubular-beam composite spatial configuration, with longitudinal beams featuring box-section rectangular tubes and crossbeams made of hollow circular tubes. Combined with a cross-shaped reinforcing partition design within the box-section of the longitudinal beams, it maintains sufficient bending and torsional stiffness even with a wall thickness reduced to 2.5mm to 3.5mm. Compared to traditional all-sheet metal subframes, it achieves a 15% to 25% weight reduction while increasing torsional stiffness by 18%, breaking the inherent conflict between lightweight design and high strength.

[0074] This invention achieves a high degree of modularity for the subframe through a segmented crossbeam structure, detachable end mounting bases, and independently configured mounting brackets. When local brackets or flanges show wear and damage, there is no need to replace the entire subframe; only the corresponding damaged modular components are disassembled and replaced individually, significantly reducing the later maintenance costs of the autonomous vehicle. Simultaneously, each mounting bracket is equipped with standardized installation interfaces, allowing for adaptation to different wheelbases and load capacity models by replacing intermediate crossbeam sections of different lengths and adjusting the mounting bracket positions. This increases the parts commonality rate to over 70%, effectively shortening the vehicle iteration development cycle.

[0075] The present invention will now be described in full and detail. This embodiment uses a subframe for a small to medium-sized unmanned vehicle as an example, and is only used to illustrate the core structure, assembly process, and manufacturing flow of the present invention, and does not constitute a limitation on the scope of protection of the present invention.

[0076] This invention adopts a modular, prefabricated, and assembled production approach, with all components cut and formed independently, making it suitable for mass production on assembly lines.

[0077] like Figure 1 , 4 As shown, the supporting beam 300 is made of 4mm thick high-strength alloy steel seamless hollow round tube, which is bent into a U-shape using a CNC tube bending machine. The bent part naturally forms an arc transition section, which smoothly transitions from the vertical section to the horizontal section of the U-shaped round tube. The radius of curvature of the arc transition section is 60mm (in this embodiment, the outer diameter of the U-shaped round tube is 40mm, and the radius of curvature is 1.5 times the outer diameter), ensuring that the stress is evenly distributed in the transition area. External threads are machined at both ends of the tube body, and the length of the thread section matches the flange assembly depth.

[0078] The rectangular tubes used for the inner frame 100 and longitudinal beam 110 of the base are 3mm high-strength box-type rectangular tubes. After CNC plasma cutting, elliptical weight reduction holes and first positioning holes 112 are punched on the side wall of the rectangular tube. The weight reduction holes are evenly distributed along the length of the rectangular tube, and a 2mm reinforcing flange is reserved at the edge of the hole.

[0079] The first mounting groove 111 is milled at both ends of the longitudinal beam 110. The first mounting groove 111 is an arc notch. The radius of the arc notch is consistent with the outer diameter (20mm) of the supporting crossbeam 300. The circumferential extension angle of the arc notch is 270° to ensure that the arc contour is completely fitted with the outer circle of the U-shaped tube during subsequent welding, thereby increasing the contact area.

[0080] The crossbeam 120 is made of 3mm alloy steel round tube with chamfered outer circles at both ends to facilitate insertion into the round holes on the side of the longitudinal beam to achieve clearance fit and pre-positioning, with a clearance of 0.1mm to 0.2mm.

[0081] The mounting flange 410, reinforcing flange 420, and swing arm bracket 200 are made of 6mm thick high-strength steel plate by stamping, avoiding the strength defects caused by separate welded flanges. The mounting flange has multiple sets of frame mounting holes 430 and a center positioning welding hole 440. The mounting flange hole wall is tapped with internal threads, and the second positioning hole 450 is used to install the positioning pin 2. The swing arm bracket 200 is stamped and formed simultaneously on both sides. The fork arm connection hole 230 is opened on both side walls. The fork arm connection hole is a waist-shaped adjustment hole, which can slightly compensate for the size error of the suspension hard point during assembly. To further enhance the structural strength of the swing arm bracket connection, a reinforcing plate 220 is added at the connection on both sides. The reinforcing plate has a bent flange on both sides to limit the installation position of the fork arm. The steering tie rod fixing seat 500 adopts a U-shaped stamping structure, with a pre-reserved welding surface at the bottom and a mounting hole at the top for installing and connecting the steering tie rod.

[0082] The reinforcing member 600 is a right-angled triangular stiffening plate with a plate thickness of 5mm. The lengths of the two right-angled sides are 40mm and 50mm respectively. The two right-angled sides are reserved for welding bevels, which are specifically used to reinforce the right-angle connection between the crossbeam 300 and the longitudinal beam 110 of the inner frame 100 of the base.

[0083] The locating pin on the frame mounting flange assembly 400 is made of heat-treated alloy steel bar. One end has an external thread that matches the flange's internal thread, and the other end has a tapered guide head. During vehicle assembly, it is quickly inserted into the body's reference hole to complete the positioning. After the locating pin is positioned, it is then bolted to the frame.

[0084] After all parts are processed, they are deburred, straightened and leveled, and stored according to their components to avoid damage to the assembly surfaces caused by bumps.

[0085] This invention employs a two-stage sub-assembly welding process followed by final assembly welding. By separating the welding steps, the heat source concentration area in each welding process is small, effectively controlling welding stress and deformation. The assembly is mainly divided into two major sub-assemblies: the base crossbeam assembly and the frame mounting crossbeam assembly.

[0086] Welding preparation of the frame mounting beam assembly: The bent U-shaped support beam is precisely positioned within a dedicated welding fixture. The fixture ensures the U-shaped opening size, and the coaxiality tolerance at both ends is controlled within ±0.2mm. First, the mounting flange 410 and reinforcing flange 420 are threaded onto both ends of the U-shaped tube. Angle limiting blocks in the fixture are used to lock the flange plane angle, preventing flange misalignment after thread pre-tightening. After pre-fixation, a composite welding process of continuous and intermittent welds is used. The main weld between the flange and the support beam tube is a continuous full weld to ensure connection strength. Intermittent welding is used around the auxiliary positioning holes on the flange side to reduce thermal deformation and residual welding stress caused by large-area continuous welding. The frame mounting flange assembly includes two types: one with a second positioning hole 450 and one without. A positioning pin is installed in the threaded hole of the second positioning hole 450, with the tapered guide head of the positioning pin facing outwards, serving as the assembly reference for the entire vehicle; the other type does not have a positioning pin and only serves as a structural load-bearing beam. After welding, a coordinate measuring machine is used to check the coaxiality and flatness of the flange positioning holes. Defective parts are sent to a calibration fixture for cold calibration. One embodiment of the invention is as follows... Figure 1 As shown, two of the four sets of frame mounting flange assemblies are equipped with locating pins.

[0087] Base beam assembly welding preparation: Two longitudinal beams 110 rectangular tubes are symmetrically placed on a welding positioning fixture, which limits the parallel spacing and end face flatness of the rectangular tubes; the two round tube beams are inserted laterally into the pre-reserved round holes on the side wall of the rectangular tubes, and the round holes and round tube beams are pre-positioned by clearance fit. After insertion, they are welded in sections around the circumference of the round holes to form a closed rectangular inner frame. Three-quarters arc notches, i.e., the first mounting grooves 111, are milled at both ends of the rectangular tubes. The arc contour is completely fitted with the outer circle of the U-shaped round tube, increasing the contact area for subsequent splicing and welding, and dispersing the weld stress. Four sets of first positioning holes 112 are reserved on the upper plane of the rectangular inner frame. Using the positioning holes as reference points, the swing arm brackets 200 are positioned and welded on them; after the swing arm brackets are welded, the steering tie rod fixing seats 500 are symmetrically welded to the outer wall of the base inner frame 100 using side hanging clamps to ensure that the installation reference of the left and right tie rods is symmetrical and to avoid the steering offset of the unmanned vehicle.

[0088] The welded base beam assembly is positioned within the final assembly welding fixture. Multiple reference positioning bosses are installed at the bottom of the fixture to constrain the length, width, and diagonal dimensions of the rectangular inner frame. The two frame mounting beam assemblies are aligned and fitted along the first mounting grooves 111 at both ends of the rectangular tube. The outer circle of the supporting beam 300 is fully fitted with the first mounting groove 111. The fitting weld still uses an intermittent welding process to reduce stress concentration in long welds. The U-shaped beam and the rectangular inner frame form four right-angle overlap areas. A reinforcing member 600 is welded to each right-angle location. The two right-angled sides of the triangular stiffener of the reinforcing member 600 are respectively fitted to the outer wall of the U-shaped tube and the upper surface of the rectangular tube. The bevels on both sides of the stiffener are fully fused, forming a high-strength, low-stress joint, solving the defects of stress concentration and fatigue cracking at the right-angle connections of traditional subframe beams and columns. After all welding processes are completed, the assembly is allowed to cool naturally; rapid water cooling is prohibited to prevent cold cracking in the welded area.

[0089] After installation, inspection is conducted. A full-dimensional accuracy inspection is performed, using a coordinate measuring machine to inspect the subframe assembly from all dimensions. Key areas of verification include flange mounting hole positions, control arm bracket hardpoint coordinates, steering tie rod mounting base mounting references, and the coaxiality of the vehicle assembly locating pins. All dimensional tolerances are controlled within ±0.3mm to ensure the assembly and matching accuracy of the suspension, steering, and powertrain. Simultaneously, the appearance of welds is inspected, checking for welding defects such as porosity, cracks, and lack of fusion. Defective areas are repaired by welding and then re-inspected.

[0090] The qualified subframe is fed into shot peening equipment, where high-strength steel shot with a diameter of 0.6mm-0.8mm is used to uniformly peen the entire inner and outer surfaces. The shot peening pressure is 0.5MPa-0.7MPa, and the coverage rate reaches 100%. After shot peening, a compressive stress layer of 400MPa-600MPa is formed on the surface of the component, effectively eliminating residual tensile stress from welding, significantly improving fatigue life under alternating loads, and adapting to the long-term bumpy working conditions of unmanned vehicles on complex road surfaces.

[0091] After shot peening, a phosphate primer is applied (phosphate film thickness 5μm-10μm), followed by an epoxy anti-rust primer (dry film thickness 40μm-60μm), and finally a wear-resistant and impact-resistant topcoat (dry film thickness 30μm-50μm). Flange threaded holes and locating pin assembly surfaces are covered with protective plugs to prevent paint from clogging the threaded holes. After coating, the surface is allowed to air dry naturally, resulting in the final modular subframe.

[0092] The finished subframe is quickly connected to the autonomous vehicle's main frame via flanges at both ends and locating pins. The tapered guide heads of the locating pins automatically compensate for manufacturing errors in the vehicle body, eliminating the need for repeated manual calibration. The suspension arms are fixed with arm bracket bolts, and the steering tie rods are fixed with steering tie rod mounting bolts. The stabilizer bar and cooling pipes are quickly connected via standardized mounting interfaces.

[0093] When local brackets or flanges show wear and damage, there is no need to replace the entire subframe; only the corresponding damaged modular components can be disassembled and replaced individually, significantly reducing the later maintenance costs of the autonomous vehicle. At the same time, the segmented modular structure allows for the replacement of crossbeam sections of different lengths and flanges of different specifications according to different loads and sizes of autonomous vehicles. Vehicle adaptation can be achieved by adjusting only a few sub-assemblies, without the need to redevelop the entire subframe.

[0094] The subframe prepared in this embodiment has been verified by bench testing. Under ±0.8g acceleration alternating load conditions, its fatigue life reaches more than 800,000 cycles (compared to about 250,000 cycles for traditional integral sheet metal subframes). The overall weight is reduced by about 21%, and the torsional stiffness is increased by 18%, perfectly meeting the needs of unmanned logistics delivery vehicle chassis.

[0095] The lightweight, high-strength modular unmanned vehicle subframe structure provided by this invention can be mass-produced using conventional metal processing equipment and welding processes. The raw materials are widely available, and the manufacturing process is mature and reliable. It is suitable for chassis systems of various unmanned delivery vehicles, unmanned patrol vehicles, unmanned shuttle vehicles, and other small and medium-sized unmanned vehicles, and has good industrial applicability.

[0096] The present invention relates to an unmanned vehicle subframe structure, its assembly method, and the unmanned vehicle itself. It overcomes the shortcomings of existing subframe beam-column welded joints, which suffer from severe stress concentration and are prone to fatigue cracks under alternating loads. It can effectively disperse the stress at welded joints and significantly improve fatigue durability, thus possessing strong practicality and good application prospects.

[0097] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention (including the claims) is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in the details for the sake of brevity.

[0098] This invention is intended to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this invention should be included within the scope of protection of this invention.

[0099] The present invention has been described above by way of example with reference to the accompanying drawings. However, the present invention is not limited to the above-described manner. Any non-substantial improvements made using the inventive concept and technical solution of the present invention or any direct application to other situations shall fall within the protection scope of the present invention.

Claims

1. A subframe structure for an unmanned vehicle, characterized in that: The device includes a base crossbeam assembly and a frame mounting crossbeam assembly connected thereto; the base crossbeam assembly includes an inner base frame, on which a first mounting groove is provided for mounting the frame mounting crossbeam assembly; the inner base frame is a frame structure composed of two longitudinal beams and a crossbeam connecting the two longitudinal beams; the frame mounting crossbeam assembly includes a support crossbeam and a frame mounting flange assembly connected to the support crossbeam; the support crossbeam is embedded in the first mounting groove.

2. The unmanned vehicle subframe structure according to claim 1, characterized in that: The inner frame of the base is provided with a swing arm bracket that connects to the double wishbone and a steering tie rod fixing seat that supports the steering tie rod; a reinforcing member is provided at the corner where the frame mounting beam assembly and the base beam assembly are connected.

3. The unmanned vehicle subframe structure according to claim 1, characterized in that: Two longitudinal beams are arranged in parallel and spaced apart. The longitudinal beams are box-shaped rectangular beams, and the crossbeams are circular tube beams. The inner sidewall of the longitudinal beams is provided with mounting holes for installing the crossbeams, and both ends of the crossbeams are inserted into the mounting holes.

4. The unmanned vehicle subframe structure according to claim 1, characterized in that: The support beam has a U-shaped structure, and the frame mounting flange assembly is threaded onto the end of the opening of the support beam.

5. The unmanned vehicle subframe structure according to claim 4, characterized in that: The frame mounting flange assembly includes a mounting flange, which is a rectangular tube structure; the mounting flange is provided with a reinforcing flange, and both the mounting flange and the reinforcing flange are provided with internal thread mounting holes that are threaded to the support crossbeam, and are also provided with corresponding frame mounting holes and a second positioning hole, the upper end of which is a positioning welding hole.

6. The unmanned vehicle subframe structure according to claim 4, characterized in that: The supporting crossbeam is a U-shaped structure made of a round tube, including a horizontal section and a vertical section; an arc transition section is provided between the horizontal section and the vertical section; the first mounting groove is an arc-shaped groove provided at both ends of the longitudinal beam, and the radius of the arc-shaped groove is the same as the outer diameter of the supporting crossbeam.

7. The unmanned vehicle subframe structure according to claim 2, characterized in that: The swing arm bracket includes a swing arm bracket body, which is a U-shaped structure. The two side walls of the opening of the swing arm bracket body are provided with fork arm connection holes, which are waist-shaped holes. The two side walls of the swing arm bracket body are provided with reinforcing plates, which are provided with fork arm connection holes corresponding to the fork arm connection holes on the swing arm bracket body.

8. The unmanned vehicle subframe structure according to claim 2, characterized in that: The steering tie rod mounting base includes a mounting base body, which has a U-shaped structure with the U-shaped opening facing downwards and is connected to the inner frame of the base. The two side walls of the mounting base body are arranged at an incline, and a support mounting surface is provided on the mounting base body. A tie rod mounting hole and a third positioning hole are provided on the support mounting surface.

9. A method for assembling the subframe structure of an unmanned vehicle as described in claim 1, characterized in that: The process involves welding two sub-assemblies before final assembly welding. The welding of the two sub-assemblies includes welding of the base crossbeam assembly and welding of the frame mounting crossbeam assembly. The welded base crossbeam assembly is positioned in the final assembly welding fixture, and the frame mounting crossbeam assembly is aligned and fitted along the first mounting groove. The fitting weld is made using an intermittent welding process.

10. An unmanned vehicle, comprising the unmanned vehicle subframe structure as described in any one of claims 1 to 8.

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