A CATIA tool aided design method suitable for four-bar linkage automobile front hood

Abstract

This application discloses a CATIA-aided design method for a four-link automotive hood, belonging to the technical field of automotive body opening and closing components. The method includes: acquiring a design parameter set; constructing a closed-state four-link model; receiving primary and secondary control parameter sets for the hood; inputting these sets into the closed-state four-link model; constructing an arbitrary-state four-link model; acquiring gas spring parameters and the surface where the gas spring hinges to the vehicle body; setting surface constraint rules; calculating the coordinates of the hinge points on the surface; constructing an arbitrary-state gas spring model line by combining the arbitrary-state four-link model; receiving process parameters within the arbitrary-state four-link model and the gas spring model line; performing torque balancing, temperature correction, and clearance calculation on the process parameters to obtain output parameters; setting specific inspection rules to perform compliance verification of the output parameters; and recording the execution data during the compliance verification process.

Description

Technical Field

[0001] This application belongs to the technical field of automotive body opening and closing components, and specifically relates to a CATIA tool-aided design method suitable for a four-link automotive front hood. Background Technology

[0002] In the field of automotive body opening and closing technology, the four-link hood has become one of the mainstream design solutions because it can adapt to complex movement spaces, optimize the operating experience and improve structural reliability. As the core power assist component of the hood, the rationality of the hinge point arrangement, the suitability of the selection and the accuracy of the opening and closing force calculation will directly determine the safety, structural stability and human-machine interaction experience of the hood.

[0003] However, in the current automotive R&D industry, the software used for hoods with four-link hinges to arrange and verify the position and stroke of gas springs and calculate opening and closing forces are mostly professional mechanical analysis tools or spreadsheet software (such as Excel), which are completely independent of CATIA, the mainstream opening and closing component design software used by car manufacturers.

[0004] This makes it impossible for R&D personnel who use CATIA to perform geometric modeling of the front hood to directly perform stroke compliance verification and opening and closing force calculations on the initially selected gas spring layout based on the CATIA model. They need to manually extract geometric parameters such as hinge point coordinates and opening angles from CATIA and then import them into other tools for secondary calculations. This not only increases the cost of manual operation, but also makes it easy for the calculation results to be distorted due to parameter transmission errors.

[0005] Furthermore, since the four-bar linkage is different from the single-axis hinge, the movement of the four-bar hood depends on the dynamic instantaneous center rather than a fixed rotation axis. Moreover, the dynamic instantaneous center is not a solid structure and its position is constantly changing during the opening and closing of the hood. This makes it difficult to obtain the lever arm of the gas spring force through measurement and cannot be accurately expressed by a function. Traditional designs can only rely on simplified assumptions for estimation, resulting in large calculation deviations. Meanwhile, due to the multi-hinged structure, the frictional resistance of the four-bar hinge is significantly greater than that of the single-axis hinge. However, traditional calculations often ignore this key parameter, resulting in a large discrepancy between the calculated opening and closing force under normal temperature, high and low temperature conditions and the actual vehicle feel. This can easily lead to problems such as excessive opening force at low temperatures and insufficient closing force at high temperatures, and may even cause safety hazards such as the hood opening and closing unexpectedly. In addition, since the four-bar model design often uses engineering control parameters such as the opening step position of the second-force member as input, while users are more concerned with parameters that can be intuitively perceived, such as the instantaneous working rod and the frame rod angle, the two lack a direct mapping relationship, making it difficult for the tool to output the dynamic curve corresponding to the opening angle and force value, and thus failing to provide intuitive data support for the selection and optimization of gas springs. Meanwhile, the complex planar motion of the hood requires the hinge points at both ends of the gas spring to be adjusted in real time according to the posture. Traditional methods cannot automatically generate instantaneous gas spring model lines based on the dynamic parameters of the four-bar linkage. Manual drawing is not only inefficient, but also prone to causing motion interference between the gas spring and components such as the inner panel of the hood and the windshield, or problems such as the gas spring stroke exceeding the limit.

[0006] Therefore, the present invention provides a CATIA tool-aided design method suitable for four-link automotive hoods. Summary of the Invention

[0007] To address the aforementioned problems, this application provides a CATIA-aided design method for a four-link automotive hood, specifically as follows: Obtain the design parameter set and construct a closed-state four-bar linkage model; Receive the first and second level control parameter sets of the front hood, input the first and second level control parameter sets of the front hood into the closed state four-bar model, and construct the arbitrary state four-bar model; Obtain the parameters of the gas spring and the surface where the hinge point between the gas spring and the vehicle body is located, set the surface constraint rules, calculate the coordinates of the hinge point of the gas spring on the surface, and combine the four-connected model of arbitrary state to construct the model line of the gas spring in arbitrary state. Receive process parameters within the line of a four-bar linkage model and a gas spring model in any state, perform torque balancing, temperature correction, and clearance calculation on the process parameters, and obtain the output parameters; Set specific inspection rules to perform compliance verification output parameters, and record the execution data during the compliance verification output parameter process; Define the output parameters after compliance verification as compliance parameters, and match the compliance parameters to the record class parameters of the corresponding working conditions.

[0008] Preferably, the design parameter set includes the coordinates of the four-bar linkage points and the friction torque parameter set, the gas spring parameter set, the primary control parameter set, and the secondary control parameter set; Based on the coordinates of the four-bar hinge points and the friction torque parameter set, component connection constraint rules are set to determine the fixed points of the four-bar model in the closed state, and static constraint rules for the hinge pairs are set to limit the motion form and static force characteristics of the hinge points. The lengths of each component of the four-bar linkage are calculated based on the coordinates of the four-bar hinge points. A closed-state four-bar model is constructed based on the component connection constraint rules, the hinge pair static constraint rules, and the lengths of each component.

[0009] Preferably, the length of the component is specifically: The coordinates of the four-bar hinge points include the coordinates of the frame rod hinge points, which include hinge point A and hinge point B; the distance between hinge point A and hinge point B is the length of the component. The square root of the difference between the x-coordinate of hinge point B and the x-coordinate of hinge point A is defined as the first value, and the square root of the difference between the y-coordinate of hinge point B and the y-coordinate of hinge point A is defined as the second value. The length of each component is obtained by calculating the arithmetic square root of the first value and the second value.

[0010] Preferably, the arbitrary state four-bar model includes an open state four-bar model for simulating the process of the hood from closing to fully raising, and an instantaneous state four-bar model for capturing the position and force characteristics of the hood at a certain angle during its movement. The set of primary control parameters for the front hood includes, but is not limited to, the opening angle of the front hood in the open state, and the set of secondary control parameters for the front hood includes, but is not limited to, the opening positions of the front and rear levers. The four-bar linkage model in the open state is as follows: Based on the length of each component, the coordinates of the hinge point of the frame rod, the opening position of the front two force rods, the instantaneous center coordinates of the rotation of the cover rod, and combined with the opening angle of the front cover in the opening state and the instantaneous center coordinates of the rotation of the cover rod, the coordinates of the hinge point of each component in the four-bar linkage model in the opening state are calculated by rotation transformation. Based on the coordinates of the hinge point of each component in the four-bar linkage model in the opening state and the opening angle of the front cover in the opening state, the four-bar linkage model in the opening state is constructed.

[0011] Preferably, the instantaneous state four-bar linkage model is as follows: Based on the opening step position of the rear two-force bar, a mapping relationship between the rotation angle of the rear two-force bar and the opening angle of the front hood in the open state is established, and the number of opening step positions of the rear two-force bar is divided. The dynamic opening angle corresponding to the opening step position of the rear two-force bar is calculated based on the number of opening step positions of the rear two-force bar. By combining the hinge point coordinates of the frame rod, the hinge point coordinates of the front two force rods and the cover rod, and the hinge point coordinates of the rear two force rods and the cover rod in the closed state four-bar model, the instantaneous state four-bar model is constructed after repeated calculations, and the instantaneous center line of the working rod velocity in any angle state is accurately generated through the instantaneous state four-bar model.

[0012] Preferably, the gas spring parameters include, but are not limited to, the natural length of the gas spring, the minimum force F1 in the elongation direction of the gas spring under normal operating conditions, the maximum force F2 in the elongation direction of the gas spring under normal operating conditions, the minimum force F3 in the compression direction of the gas spring under normal operating conditions, the maximum force F4 in the compression direction of the gas spring under normal operating conditions, the positions of the gas spring force measuring points XF1 and XF3, the positions of the gas spring force measuring points XF2 and XF4, the force difference at the same point of the gas spring under normal and low temperatures, the force difference at the same point of the gas spring under high and normal temperatures, and the standard stroke of the gas spring. The surface constraint rules include position constraint rules for restricting the air spring hinge point to be within the preset installation surface range of the vehicle body, and posture constraint rules for ensuring that the air spring maintains a safe clearance with surrounding components. The position constraint rule is as follows: the hinge point between the gas spring and the vehicle body must fall within the effective area of ​​the preset installation curved surface of the vehicle body, and the minimum gap between the gas spring and the edge of the curved surface shall not be less than 5mm. The hinge point between the gas spring and the cover must fall within the reinforcing rib area of ​​the inner panel of the front hood, and the horizontal distance between it and the front hood hinge must be no less than 30mm. The posture constraint rule is as follows: when the front hood is closed, the angle between the gas spring installation angle and the normal direction of the inner panel of the front hood is controlled between 15° and 30°. With the hood fully open, the angle between the gas spring and the inner hood panel and the windshield is ≥10°.

[0013] Preferably, the arbitrary state gas spring model line is as follows: Based on the natural length of the gas spring, the preset curved surface of the vehicle body, and the initial coordinates of the hinge point of the cover, the coordinates of the hinge point of the gas spring on the curved surface of the vehicle body are calculated using the initial coordinates of the hinge point of the cover as a reference. It also obtains the geometric boundaries between the surrounding components and the gas spring, and calculates the minimum distance between the vehicle body hinge point and the geometric boundaries; Again, based on the normal vector of the initial coordinates of the hood hinge point, calculate the gas spring direction vector, and the normal vector and the gas spring direction vector must satisfy the angle constraint: the angle formed between the normal direction of the inner panel of the hood at the initial position of the hood hinge point and the thrust direction of the gas spring itself needs to be controlled within the range of the hood opening angle 15° to 30°. And obtain the hinge coordinates of the hood again, and calculate the horizontal distance between the hinge coordinates of the hood and the hinge point coordinates of the vehicle body; Based on the natural length of the gas spring, the preset curved surface of the vehicle body, the coordinates of the hinge point of the gas spring on the curved surface of the vehicle body, the minimum distance between the hinge point of the vehicle body and the geometric boundary, the angle constraint between the normal vector and the direction vector of the gas spring, and the horizontal distance between the hinge coordinates of the hood and the hinge point of the vehicle body, an arbitrary state gas spring model line is constructed.

[0014] Preferably, the process parameters include parameters for calculating the coordinates of the gas spring hinge point, parameters for verifying the gaps between surrounding components, parameters for constraining the direction vector of the gas spring, and parameters for matching the horizontal distance between the front hood and the hinge point of the vehicle body. By setting force and stroke constraint rules, process parameters are obtained by torque balancing, temperature correction, and clearance calculation. The force constraint rule is specifically as follows: Normal temperature operating conditions: manual door opening force ≤30N, manual door closing force ≥-150N; Extreme temperature conditions: opening force at -30℃ ≤ 35N, closing force at 50℃ ≥ -160N, with a deviation from the force value at normal temperature not exceeding 15%; The travel constraint rules are as follows: The maximum compression stroke of a gas spring must not exceed its standard stroke; With the hood in any open position, the length of the gas spring is controlled within the tolerance range of the natural extension and contraction length of the gas spring; The minimum clearance between the gas spring and surrounding components is ≥5mm. Operating conditions after force decay: When the gas spring force decays to 92% of the rated value, the manual door closing force at low temperature is ≥-165N.

[0015] Preferably, the torque balance specifically refers to: Obtain the weight of the hood, the total frictional torque at the hinge point, the instantaneous center coordinates in the four-bar linkage model under any state, and the center coordinates of the hood. Calculate the center arm of the hood and substitute it into the torque balance formula to calculate the actual supporting force of the gas spring under the current posture. The temperature correction specifically refers to: Based on the actual supporting force of the gas spring in the current posture, calculate the actual force values ​​of the gas spring at low and high temperatures; The gap calculation is specifically as follows: Obtain the hinge point coordinates of the gas spring model line in any state, as well as the surface geometry parameters of the surrounding components, and calculate the minimum clearance between the gas spring rod and the surrounding components.

[0016] Preferably, the torque balance value, the actual force value of the gas spring under low temperature and high temperature are compared with the force constraint rules. If the torque balance value, the actual force value of the gas spring under low temperature and high temperature are all within the force constraint rules, then it is determined to be a compliant parameter, and the compliant parameter is matched to the record type parameter of the corresponding working condition. Compare the minimum clearance with the travel constraint rules. If the minimum clearance meets the travel constraint rules, it is determined to be a compliant parameter, and the compliant parameter is matched to the record-type parameter of the corresponding working condition.

[0017] Compared with the prior art, this application has the following advantages: 1. There is no need to manually extract parameters such as hinge point coordinates and opening angles from CATIA and import them into other tools for secondary calculations. The four-bar linkage modeling, gas spring layout verification, stroke verification and opening and closing force calculation are completed directly based on the CATIA model. This reduces manual operation costs and parameter transmission errors, and enables real-time iterative verification after design adjustments, which greatly improves R&D efficiency.

[0018] 2. By tracking the dynamic instantaneous center trajectory and quantifying the gas spring lever arm, and combining the friction torque distribution rules, the total friction resistance torque is decomposed to a single hinge point. This avoids the calculation deviation caused by neglecting friction resistance or simplifying the instantaneous center assumption in traditional designs, and significantly reduces the deviation between the opening and closing force calculation results under various working conditions such as normal temperature, high and low temperature and the actual vehicle feel, thereby improving the accuracy of force calculation.

[0019] 3. Establish a mapping relationship between the opening position of the second-force bar and the instantaneous angle of the working rod, and automatically output the opening angle-force value correspondence table and dynamic curve to meet the user's need for intuitive perception parameters. At the same time, the instantaneous state four-bar model covers the entire stroke motion process from closed to fully open, accurately captures the position and force characteristics at each angle, and avoids missing abnormal motion at intermediate angles.

[0020] 4. By locking the precise coordinates of the gas spring hinge point through multi-dimensional curved surface constraint rules, the gas spring model line in any state is automatically generated to ensure that the gas spring maintains a safe clearance with the inner panel of the hood, the windshield and other surrounding components, and avoids motion interference. At the same time, through force value and stroke constraint verification, temperature correction and static self-locking verification, problems such as excessive opening force at low temperatures, insufficient closing force at high temperatures and gas spring overtravel are avoided, preventing the hood from opening and closing unexpectedly and improving the safety and structural stability of use.

[0021] Other features and advantages of this application will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the application. The objectives and other advantages of this application may be realized and obtained by means of the structures pointed out in the description, claims and drawings. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 The diagram shows the parameters of the four-bar linkage control. Figure 2 The control parameters of the gas spring are shown in the diagram. Figure 3 The diagram of the first-level control parameters is shown; Figure 4 The diagram of the secondary control parameters is shown; Figure 5 The process parameter diagram is shown; Figure 6 The output parameter graph is shown; Figure 7Recording parameters are shown. Figure 1 ; Figure 8 Recording parameters are shown. Figure 2 ; Figure 9 Recording parameters are shown. Figure 3 ; Figure 10 Recording parameters are shown. Figure 4 ; Figure 11 Recording parameters are shown. Figure 5 ; Figure 12 Recording parameters are shown. Figure 6 ; Figure 13 Recording parameters are shown. Figure 7 ; Figure 14 Recording parameters are shown. Figure 8 ; Figure 15 A schematic diagram of a four-bar linkage model in a closed state is shown; Figure 16 A schematic diagram of the instantaneous center of velocity of the working rod is shown; Figure 17 The overall flowchart of the present invention is shown. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0025] In current technologies, to meet the core requirements of car hoods such as movement space, user experience, and structural reliability, a four-bar linkage mechanism is usually used in the design of car hoods to achieve the goals of adapting to movement space constraints, optimizing user experience, improving structural reliability, and meeting styling design requirements. However, since the rotation of the four-bar linkage depends on the dynamic instantaneous center rather than the fixed axis (determined by the planar motion characteristics of the four-bar linkage), the existing technology cannot accurately track the trajectory of the instantaneous center when the four-bar linkage rotates. This not only makes it difficult to quantify the geometric relationship of the gas spring lever arm, resulting in low efficiency of manual calculation, but also leads to the omission of the frictional resistance of the multiple articulation pairs of the four-bar linkage due to simplified assumptions, which significantly increases the deviation between the force value result and the actual vehicle feel. Meanwhile, when the opening angle, gas spring stroke, opening and closing force, and other data of the four-bar linkage are scattered in different tools (such as CAD and Excel), for example, when CAD is used as a geometric modeling tool, the CAD tool can only draw the static model of the four-bar linkage in a specific state. It cannot automatically associate dynamic data of different opening angles, nor does it have the algorithm logic for force calculation and multi-condition analysis. Although Excel can perform force calculation, it requires manual input of the opening angle, gas spring stroke, and other data extracted from CAD. It cannot link with the geometric model of CAD in real time, it is difficult to process multi-state data of the entire stroke in batches, and it cannot automatically adapt to the parameter differences of different working conditions such as normal temperature and high and low temperature. Therefore, to solve the above problems, such as Figures 1 to 17 This invention provides a CATIA tool-aided design method for a four-link automotive hood, specifically: Obtain the design parameter set and construct a closed-state four-bar linkage model; like Figures 1 to 14 As shown, to address the issue that when a car hood uses a four-bar linkage mechanism, which relies heavily on the dynamic instantaneous center of gravity, existing technologies struggle to accurately track the instantaneous center of gravity trajectory during rotation and quantify the lever arm of the gas spring. This results in low efficiency for manual calculations and significant deviations in force value calculations. Furthermore, it fails to correlate the full-stroke angle (the angle change of the hood from fully closed to fully open) with the force value and makes it difficult to verify performance under multiple operating conditions. Therefore, based on the structural design requirements of the car hood, the vehicle body model, component specifications, and experimental data, a design parameter set is obtained. This design parameter set includes input parameters, process parameters, output parameters, and record parameters. Specifically: Input parameters include the coordinates of the four-bar linkage points and the friction torque parameter set, the gas spring parameter set, the first-level control parameter set, and the second-level control parameter set; The set of four-bar linkage coordinates and friction torque parameters includes, but is not limited to: X and Z coordinates of the front hinge point of the frame rod in the closed state, X and Z coordinates of the rear hinge point of the frame rod in the closed state, X and Z coordinates of the upper hinge point of the front two-force member in the closed state, X and Z coordinates of the upper hinge point of the rear two-force member in the closed state, and the set of four-bar friction torque parameters. Since the total frictional torque of a four-bar linkage is a comprehensive reflection of the frictional effects at each hinge point, it cannot be directly matched to the parametric modeling requirements of a single hinge point. Therefore, the frictional torque of the four-bar linkage is decomposed through frictional torque distribution rules, thereby accurately mapping the total frictional torque to the specific location of each hinge point. This lays the foundation for subsequent support parametric attribute binding. The specific frictional torque distribution rules are as follows: Based on the structural form (such as the type of rotating joint) and stress level (such as the load-bearing ratio) of each hinge point, the total frictional resistance torque of the four-bar linkage is distributed proportionally (the proportion is determined by combining the structural form, stress level and engineering experience of the hinge points) to individual hinge points such as the front hinge point, rear hinge point, front two-force member hinge point, and rear two-force member hinge point of the frame rod, so as to obtain the independent frictional torque value of each hinge point, and the multiple independent frictional torque values ​​are combined to form a frictional torque parameter set; The gas spring parameter set includes, but is not limited to: gas spring natural length, minimum force F1 in the extension direction of the gas spring under normal operating conditions, maximum force F2 in the extension direction of the gas spring under normal operating conditions, minimum force F3 in the compression direction of the gas spring under normal operating conditions, maximum force F4 in the compression direction of the gas spring under normal operating conditions, positions of gas spring force measuring points XF1 and XF3, positions of gas spring force measuring points XF2 and XF4, force difference at the same point of the gas spring under normal and low temperatures, force difference at the same point of the gas spring under high and normal temperatures, and standard stroke of the gas spring. The primary control parameter set for the hood includes, but is not limited to: hood opening angle; The front hood secondary control parameter set includes, but is not limited to: the opening position of the rear two levers and parameter record clearing.

[0026] Process parameters include length parameters, angle parameters, integer parameters, torque parameters, force value parameters, etc.

[0027] By acquiring input parameters from the design parameter set and combining them with process parameters generated by the calculation tool, it is possible to accurately track the instantaneous center trajectory of the four-link linkage and quantify the gas spring lever arm, solving problems such as difficulty in tracking the instantaneous center and difficulty in calculating the lever arm in traditional designs, thereby eliminating the deviation between the force value and the actual vehicle feel.

[0028] Since the four-bar linkage is composed of four components connected by hinge points, its closed state must simultaneously meet the geometric constraints of fixed component lengths and compliant hinge point rotation relationships (for example, the hinge point distance between the frame rod and the front and rear two-force rods must match the design length of the components). If it is drawn manually, it is not only difficult to accurately control the relative positions of multiple hinge points, but it is also easy to have problems such as component length mismatch and hinge relationship conflict. Moreover, it is also impossible to quickly adapt to requirements such as the front hood fitting snugly against the vehicle body space when closed. Therefore, in order to precisely control the relative positions between the hinge points of each component and achieve a quick fit between the hood and the vehicle body space when the hood is closed, such as Figure 15 As shown, based on the coordinates of the four-bar hinge points and the friction torque parameter set, component connection constraint rules and hinge pair static constraint rules are set, and the length of each component is calculated through the coordinates of the four-bar hinge points. Taking CATIA as an example, a four-bar closed model that conforms to geometric constraints is generated in CATIA. The specific component connection constraint rules are as follows: The component rigidly connected to the vehicle body is defined as the frame rod, which serves as the motion reference. The two movable components hinged to the frame are defined as front and rear two-force members, which serve as motion transmission components; The component rigidly connected to the front hood is defined as the hood rod, which serves as a motion actuator. The static constraint rules for articulated joints include articulated topology constraints, spatial pose constraints, and length-invariant constraints, specifically: Hinged topology constraint: requires that each component be connected by a revolute joint through a single hinge point, constructing the kinematic chains from the frame rod to the front and rear two-force members, and from the frame rod to the cover rod, and prohibiting over-constraints or kinematic pair interference; Spatial position constraints: In the closed state, the upper surface of the hood rod must meet the surface difference and clearance requirements with the curved surface of the front hood. At the same time, all components must maintain a safe distance from the powertrain, pipelines and other components in the front compartment to avoid static interference. Constant length constraint: The length of each component is determined by the coordinates of its hinge point through a planar geometric algorithm and remains constant throughout the entire motion cycle. The relative angle between the components is changed only by the rotation of the hinge point, so as to ensure the determinism and traceability of the mechanism's motion. The specific principles of the planar geometry algorithm are as follows: Based on the coordinates of the frame hinge point Coordinates of the hinge points between the front two force members and the hood rod The coordinates of the hinge point between the rear two force members and the cover rod ( Calculate the distance between the coordinates of each hinge point in sequence. Since each component in the four-bar linkage is a rigid member (with a fixed length), and each component is connected to other components at both ends through hinge points, the distance between the coordinates of the hinge points is equal to the length of each component itself. ; Using the coordinates of the hinge points of the frame links in a four-bar linkage For example, at this time The distances between them are as follows: ; By calculating the distance between each hinge point using a planar geometry algorithm, the length of each component can be determined, ensuring that the length of each component of the four-bar linkage remains constant throughout the entire motion cycle. By adjusting the relative angles through hinge point rotation, the deterministic motion trajectory of the mechanism can be guaranteed, component deformation or interference can be avoided during the motion, and the motion state of the mechanism can be accurately traced and reproduced. Meanwhile, if the frictional torque of the hood is insufficient (too small) when the hood is closed, it may open on its own due to gravity or the preload of the gas spring, posing a safety risk. Therefore, based on the frictional torque parameter set of the four-bar linkage, a static self-locking constraint rule is set to verify the static force balance of each component in the closed state. Specifically: The friction torque parameter set of the four-bar linkage is bound to each hinge point (frame rod - front two-force rod, frame rod - rear two-force rod, two-force rod - hood rod), and the friction torque value of each hinge point is allocated based on the friction torque distribution rule. The static force balance of each component in the closed state is verified so that the gravity of the hood rod, the preload of the gas spring and the friction force of the hinge point meet the static self-locking condition (i.e., the friction torque value ≥ the external torque value), so as to prevent the front hood from opening on its own due to insufficient friction in the closed state. The specific method for verifying the static force equilibrium of each component under closed-loop conditions is as follows: using the static self-locking constraint rule judgment formula: (in, The total frictional torque at the hinge point, For the moment of gravity of the cover rod, (Gaseous spring preload torque). Calculate the actual values ​​of the total frictional torque at the hinge point, the hood rod gravity torque, and the gas spring preload torque in the current closed state. If the total frictional torque at the hinge point in the closed state is less than the external torque value, then adjust the frictional torque parameter set (e.g., select a hinge pair material with a higher coefficient of friction) or optimize the four-bar hinge point coordinates (e.g., adjust the hood rod center of gravity position to reduce the hood rod gravity torque). (until the static self-locking constraint rule is satisfied); Furthermore, after constructing a closed-state four-bar linkage model in CATIA, the physical characteristics of the hinge points (such as friction torque values) cannot be directly represented by geometric coordinates alone, which may directly affect the static self-locking and dynamic motion performance of the four-bar linkage. Therefore, it is necessary to select the features of each hinge point (such as revolute joints) and use the attribute-parameter function (one of the core tools of CATIA parametric modeling, which can bind the geometric features and physical properties (such as friction torque) in the model with numerical parameters, so that they can be effectively called and dynamically updated by subsequent modules (such as knowledge engineering and simulation modules); Simultaneously, the attribute-parameter input function is entered into the CATIA tool, and based on CATIA's knowledge engineering module, a formula relating friction torque to the hinge point structure is established. ; at this time This can be automatically obtained through force analysis of the component in a closed state, enabling dynamic correlation of frictional torque (e.g., when adjusting the component coordinates subsequently). The change can be updated synchronously with the total frictional torque at the hinge point. ); The value obtained by calculating the distance between each hinge point is the actual length of the corresponding component. Then, the length parameters are integrated into a component length system. Since the motion of the four-bar linkage needs to meet the planar geometric rules of fixed component length and hinge point hinge constraint, the component length is used as the core geometric constraint for generating the closed state four-bar linkage model. This limits the initial pose and connection relationship of each component, thereby constructing a closed state four-bar linkage model that conforms to the actual assembly state.

[0029] In summary, by acquiring a set of design parameters (first obtaining input parameters such as hinge point coordinates and gas spring parameters, then, based on the force analysis of the hood, disassembling the total frictional resistance torque according to the load ratio to obtain the independent frictional torque values ​​of each hinge point), and combining geometric constraint implementation and parametric model construction (using planar geometry algorithms to calculate component length, setting static constraints such as hinge topology and spatial pose, binding the disassembled frictional resistance torque parameters to CATIA hinge point features, establishing dynamic correlation formulas, and finally verifying the static self-locking conditions), a closed-state four-bar model with clear geometric constraints and integrated performance parameter binding is generated. This not only solves the problems of difficulty in tracking the instantaneous center of gravity and parameter disconnection in traditional design, but also provides accurate and reliable initial configuration and parameter basis for subsequent dynamic models and force value calculations, effectively improving the design efficiency and reliability of the hood four-bar and gas spring system.

[0030] Furthermore, when a user inputs or modifies the four-bar control parameters, the CATIA tool will automatically generate a closed-state four-bar model corresponding to the four-bar control parameters, or update the closed-state four-bar model to correspond to the four-bar control, making it convenient for the user to make a visual reference.

[0031] Receive the primary and secondary control parameter sets of the front hood, input the primary and secondary control parameter sets of the front hood into the closed state four-bar linkage model, and construct an arbitrary state four-bar linkage model. The arbitrary state four-bar linkage model includes an open state four-bar linkage model for simulating the process of the front hood from closed to fully raised, and an instantaneous state four-bar linkage model for capturing the position and force characteristics of the front hood at a certain angle during movement. Specifically: Since the hood rod is rigidly set, it will make planar motion during the opening of the hood. Therefore, the motion trajectory and instantaneous rotation center of each point will change dynamically with the opening angle. It is impossible to directly use the fixed geometric relationship in the closed state four-bar model to express its motion state. Therefore, it is necessary to construct an open state four-bar model to accurately reflect the positional relationship and motion characteristics of each component at different angles. Therefore, to accurately reflect the positional relationships of each component at different angles (e.g., the spatial relative state between the components of a four-bar linkage (frame rod, front two-force rod, rear two-force rod, and cover rod), mainly reflected in the three dimensions of hinge point coordinates, component length, and relative angle) and motion characteristics (e.g., the dynamic performance of the four-bar linkage in terms of displacement law, velocity change, and force relationship during angle changes), the length of each component is received. ( Front two-force bar Rear two-force member and hood rod ), and the coordinates of the hinge points of the frame rods in the closed-state four-bar model. Coordinates of the hinge points between the front two force members and the hood rod And the coordinates of the hinge point between the rear two-force member and the hood rod ( Set as a fixed point, the instantaneous center coordinates of the computer cover rod's rotation. The calculation expression is as follows: ; Since the hood lever's motion trajectory is a rotation around the instantaneous center P, rather than a parallel movement trajectory, it receives input primary control parameters. Based on the hood opening angle from these primary control parameters and the hinge point coordinates in the four-bar linkage model for closing, it... Instantaneous center coordinates of rotation of the hood rod The new coordinates of the four-bar linkage model in the open state are calculated through rotational transformation. The specific expression is as follows: , ; in: Front hood opening angle (primary control parameter); Hood opening angle The cosine value; Hood opening angle The sine value; Simultaneously, combined with the known coordinates of the frame pole hinge point New coordinates of the four-bar linkage model in the active state The construction of a four-bar linkage model in the open state can effectively solve the problems of the dynamic changes in the motion trajectory and instantaneous rotation center of the hood rod with the opening angle during planar motion. It can accurately restore the positional relationship and motion characteristics of each component under different opening angles. This not only avoids the description error caused by directly using the fixed geometric relationship in the closed state, but also provides a precise geometric and kinematic basis for subsequent engineering processes such as motion interference verification, gas spring force calculation, and drive mechanism selection.

[0032] Furthermore, this invention considers that when the primary control parameters are input into the closed state model to construct the open state four-bar linkage model, the primary control parameters only serve as fixed basic inputs, resulting in a fixed form for the constructed open state four-bar linkage model. This cannot cover the entire stroke motion process from closed to fully open, nor can it adapt to dynamic analysis requirements such as position verification and interference checks at different opening angles. It also struggles to support subsequent calculations of parameters such as gas spring force and operating torque that vary with angle, lacking dynamic adaptability to the entire opening process. Therefore, secondary control parameters are input into the open state four-bar linkage model. Based on the adjustability of the secondary control parameters, the open state four-bar linkage model is driven to automatically update the instantaneous center coordinates and hinge point positions, obtaining the instantaneous state four-bar linkage model corresponding to the current two-force bar opening step position. This achieves dynamic coverage of different opening stages. Specifically: Receive the rear two-force bar opening step position from the secondary control parameters, establish the mapping relationship between the rear two-force bar rotation angle and the front hood opening angle, obtain the minimum and maximum opening angles of the front hood, and divide the rear two-force bar opening step position into steps. ( ≥50), and the number of steps in the opening position of the second lever. The dynamic opening angle corresponding to the opening step position of the two-force member is calculated, and the expression is as follows: ; in: The dynamic opening angle corresponding to the opening step position of the rear two-force bar; This indicates the current and subsequent two-force member opening position; The dynamic opening angle is obtained by calculating the opening step position mapping of the rear two-force bar. Combined with the length of each component Coordinates of the hinge points of the frame rods in the closed-state four-bar linkage model Coordinates of the hinge points between the front two force members and the hood rod And the hinge coordinates of the rear two-force member and the hood rod The parameters used in the calculation and the dynamic opening angle will be included. By re-inputting the data into the open state four-bar model and repeating the process of calculating the instantaneous center coordinates to the rotational transformation hinge point position, an instantaneous state four-bar model can be constructed. This effectively solves the limitation that the open state four-bar model can only reflect a single angle. It dynamically generates four-bar models for all stages from closed to open, completely restoring the full stroke trajectory of the opening process and avoiding missing motion anomalies at intermediate angles. At the same time, the opening position of the rear two levers is determined according to the number of steps. The division allows for the rapid mapping of the dynamic opening angle corresponding to the opening step position of the second-force member. It can perform position verification and interference checks in real time for asynchronous positions, providing a geometric basis for subsequent calculation of gas spring force and operating torque analysis as it changes with angle. Furthermore, it can quickly obtain the instantaneous model of the corresponding angle by only the opening position of the last two force bars, without having to repeatedly manually input fixed angles and rebuild the model. This can effectively improve the efficiency of motion analysis and parameter calculation, making the instantaneous four-bar model more suitable for the full-process verification needs in actual engineering.

[0033] Furthermore, this invention fully considers that, since traditional fixed-open state models can only output isolated instantaneous center information at a single angle, they cannot cover the dynamic change trajectory of the instantaneous center of velocity of the working rod during the entire stroke motion, nor can they support core engineering requirements such as full-stroke motion velocity analysis, operating force calculation, and mechanism interference verification. Therefore, as Figure 16 As shown, the instantaneous center line of the working rod velocity at any angle is accurately generated using a four-bar linkage model in an instantaneous state. Specifically: The dynamic opening angle corresponding to the opening step position of the received two-force member and dynamically opening angle The new coordinates generated after inputting the instantaneous state of the four-link model ( 、( and frame hinge point coordinates Calculate the opening angle in the instantaneous state Instantaneous velocity instantaneous center coordinates The expression is as follows: ; Then, based on the instantaneous state, the opening angle is... The corresponding instantaneous velocity instantaneous center coordinates ), and dynamically open the angle The new coordinates generated after inputting the instantaneous state of the four-link model ( The instantaneous center line is generated by using the principle of removing the top lines at both ends. Its expression is as follows: ; After the calculation is completed, the above expression is rearranged into a slope-intercept form for easier subsequent motion trajectory analysis, specifically: ; After the user inputs the opening step position parameters of the two-force member into the instantaneous state four-bar model, the CATIA tool will automatically generate a linear curve representing the instantaneous center of velocity of the working member, or update the elements of this curve to correspond to the input parameters. Simultaneously, based on the dynamic opening angle, the instantaneous state four-bar model will be used to... New coordinates of the instantaneous hinge point ( 、( and coordinates of the frame fixed hinge point Accurately calculate the instantaneous velocity and instantaneous center coordinates This allows for the generation of instantaneous center lines of the working lever velocity at any angle. This not only enables complete coverage of the dynamic change trajectory of the instantaneous center from closing to full opening, providing continuous and accurate kinematic basis for full-stroke motion velocity analysis and mechanism interference verification, but also supports core engineering needs such as gas spring lever arm quantification and multi-condition (normal temperature, high and low temperature) opening and closing force calculation. It effectively solves the limitation of traditional fixed models that can only provide isolated instantaneous center information at a single angle, greatly improving the accuracy, efficiency and reliability of the front hood four-bar linkage and gas spring system design, and laying a solid foundation for subsequent parameter optimization and selection adjustment.

[0034] Receive the gas spring parameters and the surface where the gas spring and the vehicle body hinge point are located, set the surface constraint rules, calculate the coordinates of the hinge point of the gas spring on the surface, and combine the arbitrary state four-connection model to construct the arbitrary state gas spring model line. If the hinge point of the gas spring is detached from the pre-set mounting surface area of ​​the vehicle body, or if there is insufficient clearance with surrounding components (such as the inner panel of the hood or the windshield), the gas spring will be unable to complete assembly during actual production, and may even come into hard contact with the vehicle body structure. This will not only cause its movement trajectory to interfere with the movement of components such as the four-bar linkage, the inner panel of the hood, or the windshield, but will also cause the thrust or pull force of the gas spring to be unable to be transmitted in the correct direction, resulting in performance failures such as excessive opening force and unsmooth closing. Therefore, surface constraint rules are set. These surface constraint rules include positional constraint rules to limit the gas spring hinge point to be within the pre-set mounting surface area of ​​the vehicle body, and posture constraint rules to ensure that the gas spring maintains a safe clearance with surrounding components (such as the inner panel of the hood and the windshield). The specific rules are as follows: Position constraint rules: The hinge point between the gas spring and the vehicle body must fall within the effective area of ​​the pre-set mounting surface of the vehicle body, and the minimum gap between the gas spring and the edge of the surface must be no less than 5mm. The hinge point between the gas spring and the cover must fall within the reinforcing rib area of ​​the inner panel of the front hood, and the horizontal distance between it and the front hood hinge must be no less than 30mm. Position constraint rules: With the hood closed, the angle between the gas spring mounting angle and the normal direction of the inner hood panel is controlled between 15° and 30°. With the hood fully open, the angle between the gas spring and the inner hood panel and the windshield is ≥10°. By setting surface constraint rules, the position constraint rules in the surface constraint rules can be used to clarify the reasonable installation range of the air spring hinge point, so as to avoid it from deviating from the preset area or having insufficient clearance with the surrounding components, thereby ensuring that the air spring can be actually assembled and avoiding hard contact with the vehicle body structure. At the same time, by using position constraint rules, the installation angle of the gas spring can be standardized throughout its entire stroke, thereby avoiding interference between its movement trajectory and components such as the four-bar linkage and the inner panel of the front hood. This ensures that the gas spring's thrust or pull force can be transmitted in a reasonable direction, preventing performance failures such as excessive opening force or unsmooth closing. Furthermore, since surface constraint rules can only determine the legal range of hinge points and cannot obtain precise coordinates, while the actual assembly and motion coordination of gas springs require clear hinge point position data, it is impossible to construct the model lines of arbitrary-shaped gas springs. This would lead to ambiguity in the geometric relationships of the arbitrary-shaped gas spring model lines, making subsequent kinematic and mechanical analyses difficult to conduct smoothly. Therefore, by obtaining the gas spring parameters and combining them with the reasonable range of surface constraint rules, a surface point-finding algorithm is used to calculate the specific hinge point coordinates of the gas spring on the surface. Specifically: Obtain the natural length of the gas spring Preset curved surfaces of the vehicle body and the hinge point of the cover The coordinates are based on the hinge point coordinates in the closed-state four-bar linkage model (the hinge point coordinates between the hood rod and the front two force members and the rear two force members). Its two-dimensional coordinates are compared with the hinge point of the cover. By combining the axis coordinates, the initial coordinates of the hinge point of the cover are output. ; Initial coordinates of the hinge point of the cover Using this as a reference, calculate the coordinates of the hinge point of the gas spring on the curved surface of the vehicle body. The expression is as follows: ; Meanwhile, because gas springs need to be reliably assembled with the vehicle body structure and match the vehicle's appearance and spatial layout requirements, the coordinates of the gas spring's hinge point on the vehicle body are... Also required: Located on the pre-defined curved surface of the vehicle body This ensures that the installation position of the gas spring at the vehicle body end conforms to the structural design specifications of the vehicle body, avoids spatial interference with other parts of the vehicle body, and ensures that the movement trajectory of the gas spring during the opening and closing of the hood is compatible with the vehicle body layout.

[0035] Furthermore, since the gas spring moves synchronously with the hood during opening and closing, if it is too close to surrounding components (such as the inner hood panel and windshield), problems such as motion interference and component scratches can easily occur. Therefore, it is essential to obtain the geometric boundaries between the surrounding components (such as the inner hood panel or windshield) and the gas spring. Calculate the hinge points of the vehicle body With geometric boundary The minimum distance is expressed as follows: ; in:( For any point on the boundary of the surrounding components; By constraining the minimum distance between the vehicle body hinge point and the boundary of surrounding components, the gas spring can maintain a safe clearance with the surrounding components throughout its full stroke, avoiding interference, scratches and other malfunctions, thus ensuring the smoothness of the hood opening and closing process and the reliability of the components. Secondly, since the direction of the gas spring's thrust directly affects the rationality of the force applied when the hood opens and closes (if the angle between the direction of the gas spring and the normal to the inner hood panel is too large, it can easily lead to localized stress concentration or abnormal opening and closing resistance), it is necessary to obtain the initial coordinates of the inner hood panel at the hinge point of the hood. Normal vector at point Calculate the direction vector of the gas spring. Then the normal vector Direction vector of the gas spring Angle constraints must be met. ; By using the included angle constraint, it can be ensured that the thrust direction of the gas spring matches the force direction of the inner panel of the hood, avoiding problems such as deformation and abnormal noise at the hinge of the hood due to unreasonable force, and optimizing the operating force and feel during the opening and closing process. Since the hood hinge is the core rotating support component of the front hood, the spatial position of the gas spring and the hinge directly affects the torque distribution of the hood's opening and closing (if the two are too close, it can easily lead to excessive local loads, while if the distance is too far, it will reduce the installation space). Therefore, obtaining the hood hinge coordinates is crucial. Calculate the hinge coordinates of the front hood. Coordinates of the hinge point with the vehicle body Horizontal distance between Thus, the coordinates of the air spring car body hinge point are obtained. ; By introducing the natural length of the gas spring, the preset surface equation of the vehicle body, and the output of the initial coordinates of the hinge point of the cover, combined with multi-dimensional verification of length tolerance constraints, safety constraints on the gaps of surrounding components, normal vector angle constraints, and horizontal distance matching constraints, it is possible to lock the precise three-dimensional coordinates of the hinge point of the vehicle body that meet all design requirements on the preset surface of the vehicle body. This achieves the effect of clarifying the spatial geometric relationship between the gas spring and the vehicle body and cover, avoiding the ambiguity of geometric relationships in the gas spring model, and ensuring that subsequent kinematic simulation and mechanical performance analysis can be carried out effectively. This lays the foundation for the subsequent construction of arbitrary state gas spring model lines by combining arbitrary state four-bar models.

[0036] Since the gas spring is a moving component that supports and drives the hood of a car, the spatial position of the hinge points at both ends of the gas spring will dynamically change synchronously with the hood's posture (such as the opening angle) when the hood changes. Therefore, by combining a four-bar linkage model in any state, and using surface constraint rules and surface point-finding algorithms, the specific coordinates of the gas spring hinge points under different postures are accurately located. This constructs a gas spring model line covering all motion states, completing the motion adaptation and geometric association between the gas spring and the four-bar linkage mechanism. Specifically: Receive parameters from the four-bar linkage model in any state (dynamic opening angle corresponding to the opening step position of the second link). Length between components and the coordinates of the frame hinge point ( ), the hinge point coordinates of the front two force members and the hood rod ( ) and the coordinates of the hinge point between the rear two force members and the hood rod ( ), and combined with the set surface constraint rules and calculation methods (surface point finding algorithm), based on the instantaneous center of gravity of the four-bar linkage under any state. (Determined by the intersection of the perpendicular lines from the hinge point of the frame rod and the two-force member), combined with the dynamic opening angle corresponding to the opening step position of the latter two-force member. Calculate the dynamic coordinates of the hinge point of the cover under the current four-link attitude. The specific expression is as follows: ; By using this rotating coordinate calculation method, the dynamic coordinates of the hood hinge point can be synchronously associated with the opening angle of the front hood, which can achieve the effect of real-time adaptation of the gas spring hinge point to the posture of the four-bar linkage, thereby ensuring that the gas spring always maintains geometric matching with the four-bar linkage during the full stroke, avoiding motion jamming or interference problems. Since the hinge point of the gas spring at the vehicle body end needs to be fixed to the vehicle body structure (and does not move with changes in the attitude of the hood), the length and direction of the gas spring are determined only by the dynamic position of the hood hinge point. Therefore, the fixed coordinates of the already determined vehicle body hinge point are reused. Determine the fixed coordinates of the vehicle body hinge point and the dynamic coordinates of the cover hinge point of the gas spring in the current four-link posture, and calculate the length of the gas spring in the current posture. and direction vector ; By receiving the dynamic parameters of the four-bar linkage model in any state, and combining the instantaneous center of rotation formula to calculate the dynamic coordinates of the hinge point of the cover, and reusing the fixed coordinates of the hinge point of the vehicle body, the length and direction vectors of the gas spring in the current posture are finally generated, and the gas spring model line in any state is constructed. This enables the motion adaptation of the gas spring and the four-bar linkage, solves the geometric conflict of asynchronous motion between the two, and provides a basis for subsequent interference verification and force value calculation. This achieves the effect of full-stroke geometric matching of the gas spring and the four-bar linkage, verifiable design, and closed-loop process.

[0037] The system receives process parameters within the lines of a four-bar linkage model and a gas spring model in any state, sets force values ​​and stroke constraint rules, and performs torque balancing, temperature correction, and clearance calculation on the process parameters based on the design parameter set to obtain process parameters. The output parameters include, but are not limited to: instantaneous angle of the working rod, instantaneous compression stroke of the gas spring, maximum instantaneous compression stroke of the gas spring, instantaneous force for opening the door under low temperature conditions, instantaneous force for closing the door under low temperature conditions, instantaneous force for opening the door under normal temperature conditions, instantaneous force for closing the door under normal temperature conditions, instantaneous force for opening the door under high temperature conditions, instantaneous force for closing the door under high temperature conditions, and instantaneous force for closing the door under low temperature conditions after the gas spring has decayed. Because the movement trajectory of the four-link front hood is dynamically changing, if the gas spring travel is not limited, the gas spring may exceed its travel range during hood movement, which could lead to damage and interference with surrounding components. Furthermore, without force constraints, the hood may feel too heavy or too light to open and close at room temperature, while causing inconvenience for users in extreme temperatures and potentially posing a safety risk of accidental opening and closing of the hood. Therefore, force and travel constraint rules are set, specifically as follows: Trip constraint rules: The maximum compression stroke of a gas spring must not exceed its standard stroke (e.g., 215mm). With the hood in any open position, the length of the gas spring must be controlled within the tolerance range of ±2mm of its natural length; The minimum clearance between the gas spring and surrounding components (inner hood panel, windshield) shall not be less than 5mm.

[0038] Force constraint rules: Operating conditions at room temperature (20℃): manual door opening force ≤30N, manual door closing force ≥-150N; Extreme temperature conditions: opening force at -30℃ ≤ 35N, closing force at 50℃ ≥ -160N, with a deviation from the force value at normal temperature not exceeding 15%; Operating conditions after force decay: When the gas spring force decays to 92% of the rated value, the manual door closing force at low temperature is ≥-165N; By setting force and stroke constraint rules, a set of quantifiable engineering and safety standards can be established for the front hood gas spring system, thereby avoiding potential gas spring damage, component interference, poor operating feel, and safety hazards under extreme conditions that may occur during dynamic movement. This ensures that the compression stroke of the gas spring is always within a safe range, preventing collisions with surrounding components. Furthermore, since the set force and stroke constraint rules are only static standard requirements, it is impossible to verify whether the gas spring actually meets the force and stroke constraint rules during the dynamic movement of the four-bar linkage. This may lead to problems such as the force and stroke constraint rules being out of sync with actual working conditions and the inability to detect potential interference in advance, resulting in safety hazards or user experience defects in the front hood during actual use. Therefore, process parameters are obtained through torque balancing, temperature correction, and clearance calculation to quantitatively verify the implementation effect of the constraint rules. Specifically: Force calculation: Obtain the weight of the hood Total frictional torque at the hinge point Instantaneous center coordinates in an arbitrary state four-bar linkage model and the coordinates of the center of gravity of the front hood Calculate the center of gravity arm of the front hood The specific expression is as follows: ; By calculating the center of gravity arm of the front hood under different postures Furthermore, by combining the principle of torque balance, the required thrust value of the gas spring is further derived, so that the force value requirement of the gas spring can be accurately matched with the actual force demand in the dynamic motion process of the four-bar linkage. This can achieve the purpose of quantitatively verifying the implementation effect of the force value and stroke constraint rules under dynamic working conditions, and discover potential interference or insufficient force value in advance, so as to avoid safety hazards or experience defects in the front hood during actual use. Furthermore, since the thrust of the gas spring is the core power driving the movement of the hood, its lever arm length (the torque arm of the thrust about the instantaneous center) directly affects the torque balance, causing the actual effective thrust of the gas spring to change dynamically with the attitude. Therefore, obtaining the dynamic coordinates of the hood hinge point of the gas spring model line in any state is crucial. Calculate the lever arm of the gas spring The specific expression is as follows: ; Finally, adjust the center of gravity arm of the front hood. Gas spring lever arm Substituting into the torque balance formula: ; Calculating the actual supporting force of the gas spring in the current posture can accurately quantify the supporting capacity of the gas spring in dynamic motion and verify whether the supporting force meets the preset force value constraint rules. Temperature correction calculation: Obtain the actual support force of the gas spring in the current attitude. Based on the temperature characteristic coefficient of the gas spring (the force of the gas spring changes with temperature; at low temperatures, the gas contraction pressure increases, and the force increases; at high temperatures, the gas expansion pressure decreases, and the force decreases), the actual force of the gas spring under extreme temperatures (low temperature, high temperature) is calculated. The specific expression is as follows: ; ; Finally, the corrected extreme temperature force values ​​are compared with the preset force value constraint rules (such as -30℃ low temperature door opening force ≤35N, 50℃ high temperature door closing force ≥-160N) to verify whether the force values ​​under all working conditions meet the design requirements, and to ensure that the front hood still has safe and reliable opening and closing performance and stable human-machine experience under extreme temperature environment. Gap calculation: Obtain the coordinates of the hinge point of the gas spring model line in any state ( ) and the curved surface geometry parameters of surrounding components (inner hood panel, windshield), calculate the minimum clearance between the gas spring rod and surrounding components. The specific expression is as follows: ; in: Let be any point on the gas spring rod; For any point on the surface of the surrounding components; Then the calculated minimum gap The gas spring is compared with the preset stroke constraint rules (such as the minimum clearance is not less than 5mm) to verify whether it will interfere with the surrounding components during dynamic movement, so as to ensure the movement safety and structural reliability of the front hood. Force calculations can prevent excessive opening force at low temperatures from causing operational difficulties for users, and insufficient closing force at high temperatures from causing the hood to slip off unexpectedly, thus posing safety hazards. Combined with gap calculations, it is possible to detect motion interference between the gas spring and the inner panel of the hood and the windshield in advance, avoiding component collision damage after actual vehicle assembly and ensuring the safety and reliability of the hood. At the same time, by calculating the force value throughout the entire stroke, it is ensured that the opening and closing force is within the comfortable range of the hand feel at every stage from closing to opening (for example, the opening force is 15-30N), avoiding the problem of the hand feel being too heavy at a certain angle and too light at a certain angle, and ensuring the stability of the human-machine experience.

[0039] Receive process parameters, set specific inspection rules to verify their compliance, and simultaneously perform data recording operations; obtain record parameters, set specific assignment rules, and match compliant parameter values ​​to the record parameters of the corresponding working conditions; if the parameter does not conform to the constraint rules, trigger an alarm prompt, thereby completing the validity verification, standardized assignment, and result traceability of process parameters; The recorded parameters include, but are not limited to: the set of opening angle values ​​corresponding to the front hood, the set of manual closing force values ​​under normal temperature conditions, the set of manual opening force values ​​under normal temperature conditions, the set of manual closing force values ​​under low temperature conditions, the set of manual opening force values ​​under low temperature conditions, the set of manual closing force values ​​under high temperature conditions, and the set of instantaneous compression parameter values ​​of the gas spring; Since process parameters (operating lever angle, compression stroke, multi-condition opening and closing force, etc.) are directly related to the safety performance, structural reliability, and human-machine experience of the hood, if these parameters exceed the preset force and stroke constraints, it can lead to risks such as excessive opening force in low-temperature conditions causing user operation difficulties, insufficient closing force in high-temperature conditions causing the hood to slip unexpectedly, and insufficient clearance causing interference between the gas spring and surrounding components. These risks can ultimately affect the safety and stability of the user experience after assembly on the actual vehicle. Therefore, specific inspection rules are set. These specific inspection rules include those related to force constraint parameters, those related to stroke and clearance constraint parameters, and those related to the operating lever angle, specifically: The working principle of the inspection rules associated with force constraint parameters is as follows: Obtain constraint thresholds for the following conditions: room temperature door opening force ≤ 30N, -30℃ low temperature door opening force ≤ 35N, 50℃ high temperature door closing force ≥ -160N, and low temperature door closing force after force decay ≥ -165N. Compare the calculated support force, low temperature correction force value, and high temperature correction force value with these thresholds. If the actual force value is within the threshold range, it is determined that the force value is compliant; if it exceeds the threshold, it is marked as an abnormal force value. The working principle of the inspection rules associated with stroke and clearance constraint parameters is as follows: The maximum compression stroke of the gas spring is ≤215mm and the minimum clearance between the gas spring and surrounding components is ≥5mm. The calculated maximum compression stroke and minimum clearance values ​​of the gas spring are compared: if the maximum compression stroke of the gas spring is ≤215mm and the minimum clearance is ≥5mm, it is determined that the stroke and clearance are compliant; if they exceed the threshold, they are marked as abnormal. The working principle of the inspection rules related to the working rod angle is as follows: The maximum opening angle (e.g., 60°) constraint threshold of the working rod in the four-bar linkage model is called, and the instantaneous angle of the working rod calculated in the output is compared: if the instantaneous angle of the working rod is less than or equal to the maximum opening angle, it is determined that the angle is compliant; if it exceeds, it is marked as an abnormal angle. By setting specific inspection rules, it is possible to achieve full-dimensional compliance control over process parameters. This not only allows for the early identification of potential risks such as excessive force, insufficient clearance, and excessive angle, thus avoiding problems such as operational difficulties, component interference, and safety hazards after actual vehicle assembly, but also ensures that process parameters meet the safety performance, structural reliability, and human-machine experience requirements of the hood. This enables the tool to accurately verify the design scheme of the four-link and gas spring, improving design efficiency and the feasibility of the final solution.

[0040] Furthermore, since compliant process parameters need to be matched to different operating conditions (such as low temperature, normal temperature, and high temperature) and application scenarios of the four-bar linkage opening step position, the lack of a unified parameter assignment logic will lead to chaotic parameter storage and inaccurate matching of corresponding operating conditions during subsequent calls, affecting the tool's efficiency in tracing and iterating design solutions. Therefore, specific assignment rules are set, specifically: The system acquires the working condition classifications of low temperature, normal temperature, high temperature, and low temperature after force value decay, and automatically assigns the corresponding working condition force values ​​(such as low temperature correction force value and normal temperature support force) to the parameter sets of the corresponding working conditions, such as the instantaneous force for manual door opening under low temperature conditions and the instantaneous force for manual door opening under normal temperature conditions. Simultaneously, the position parameters of the opening step of the second force bar are received, and the instantaneous angle and compression stroke of the working rod corresponding to different opening steps are matched to the classification parameter group of opening step + angle or stroke. Finally, the compliant force, stroke, and angle parameters are standardized and stored according to the hierarchical structure of parameter type - working condition - starting position, to ensure that the parameter values ​​of the corresponding scenarios can be accurately located when called in the future. By setting specific assignment rules, standardized management of compliant process parameters can be achieved. This not only allows for precise classification and matching of parameters under different working conditions and at different start-up positions, avoiding problems such as chaotic parameter storage and mis-calling, but also enables the orderly retention of parameters according to the hierarchical structure of parameter type - working condition - start-up position. This supports the tool in efficiently tracing and rapidly iterating design solutions, and improves the convenience of subsequent parameter reuse and solution optimization. Furthermore, to facilitate subsequent design iterations and provide a traceable data source for problem tracing, the verified and assigned process parameters are directly linked to the safety and feasibility of the hood design scheme, and the data is recorded and stored. In addition, to prevent abnormal process parameters (such as excessive force or insufficient clearance) from flowing into the actual vehicle assembly process and causing safety hazards, and to ensure the reliability of tool output results and the efficiency of the design process, alarm prompts can be triggered in a timely manner when abnormal process parameters occur. In summary, by acquiring output and record parameters, and through quantitative results such as the instantaneous angle of the output working lever, the opening and closing force under multiple working conditions (normal temperature, high and low temperatures), and the compression stroke of the gas spring, it is possible to directly determine whether the indicators meet the design requirements for the hood's operating feel, spatial constraints, and structural reliability. This can replace traditional experience-based estimations and ensure the compliance of the design results. Furthermore, based on the angle, force, and stroke data of the four-bar linkage at different opening positions, it can generate a full-stroke correlation curve from angle to force, intuitively presenting the force change trend during the opening and closing process of the car's hood. This also provides data support for subsequent gas spring selection and adjustment, and four-bar linkage parameter optimization, improving the efficiency of design iteration.

[0041] Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A CATIA tool-aided design method for a four-link automotive hood, characterized in that, Including the following: Obtain the design parameter set and construct a closed-state four-bar linkage model; Receive the first and second level control parameter sets of the front hood, input the first and second level control parameter sets of the front hood into the closed state four-bar model, and construct the arbitrary state four-bar model; Obtain the parameters of the gas spring and the surface where the hinge point between the gas spring and the vehicle body is located, set the surface constraint rules, calculate the coordinates of the hinge point of the gas spring on the surface, and combine the four-connected model of arbitrary state to construct the model line of the gas spring in arbitrary state. It receives process parameters within the line of a four-bar linkage model and a gas spring model in any state, and performs torque balancing, temperature correction, and clearance calculation on the process parameters to obtain output parameters; Set specific inspection rules to perform compliance verification output parameters, and record the execution data during the compliance verification output parameter process; Define the output parameters after compliance verification as compliance parameters, and match the compliance parameters to the record class parameters of the corresponding working conditions.

2. The CATIA tool-aided design method for a four-link automotive hood according to claim 1, characterized in that: The design parameter set includes the coordinates of the four-bar hinge point and the friction torque parameter set, the gas spring parameter set, the first-level control parameter set, and the second-level control parameter set; Based on the coordinates of the four-bar hinge points and the friction torque parameter set, component connection constraint rules are set to determine the fixed points of the four-bar model in the closed state, and static constraint rules for the hinge pairs are set to limit the motion form and static force characteristics of the hinge points. The lengths of each component of the four-bar linkage are calculated based on the coordinates of the four-bar hinge points. A closed-state four-bar model is constructed based on the component connection constraint rules, the hinge pair static constraint rules, and the lengths of each component.

3. The CATIA tool-aided design method for a four-link automotive hood according to claim 2, characterized in that: The length of the component is specifically: The coordinates of the four-bar hinge points include the coordinates of the frame rod hinge points, which include hinge point A and hinge point B; the distance between hinge point A and hinge point B is the length of the component. The square root of the difference between the x-coordinate of hinge point B and the x-coordinate of hinge point A is defined as the first value, and the square root of the difference between the y-coordinate of hinge point B and the y-coordinate of hinge point A is defined as the second value. The length of each component is obtained by calculating the arithmetic square root of the first value and the second value.

4. The CATIA tool-aided design method for a four-link automotive hood according to claim 1, characterized in that: The arbitrary state four-bar model includes an open state four-bar model for simulating the process of the hood from closing to fully raising, and an instantaneous state four-bar model for capturing the position and force characteristics of the hood at a certain angle during its movement. The set of primary control parameters for the front hood includes, but is not limited to, the opening angle of the front hood in the open state, and the set of secondary control parameters for the front hood includes, but is not limited to, the opening positions of the front and rear levers. The four-bar linkage model in the open state is as follows: Based on the length of each component, the coordinates of the hinge point of the frame rod, the opening position of the front two force rods, the instantaneous center coordinates of the rotation of the cover rod, and combined with the opening angle of the front cover in the opening state and the instantaneous center coordinates of the rotation of the cover rod, the coordinates of the hinge point of each component in the four-bar linkage model in the opening state are calculated by rotation transformation. Based on the coordinates of the hinge point of each component in the four-bar linkage model in the opening state and the opening angle of the front cover in the opening state, the four-bar linkage model in the opening state is constructed.

5. The CATIA tool-aided design method for a four-link automotive hood according to claim 4, characterized in that: The instantaneous state four-bar linkage model is as follows: Based on the opening step position of the rear two-force bar, a mapping relationship between the rotation angle of the rear two-force bar and the opening angle of the front hood in the open state is established, and the number of opening step positions of the rear two-force bar is divided. The dynamic opening angle corresponding to the opening step position of the rear two-force bar is calculated based on the number of opening step positions of the rear two-force bar. By combining the hinge point coordinates of the frame rod, the hinge point coordinates of the front two force rods and the cover rod, and the hinge point coordinates of the rear two force rods and the cover rod in the closed state four-bar model, the instantaneous state four-bar model is constructed after repeated calculations, and the instantaneous center line of the working rod velocity in any angle state is accurately generated through the instantaneous state four-bar model.

6. The CATIA tool-aided design method for a four-link automotive hood according to claim 1, characterized in that: The gas spring parameters include, but are not limited to, the natural length of the gas spring, the minimum force F1 in the elongation direction of the gas spring under normal operating conditions, the maximum force F2 in the elongation direction of the gas spring under normal operating conditions, the minimum force F3 in the compression direction of the gas spring under normal operating conditions, the maximum force F4 in the compression direction of the gas spring under normal operating conditions, the positions of the gas spring force measuring points XF1 and XF3, the positions of the gas spring force measuring points XF2 and XF4, the force difference at the same point of the gas spring under normal and low temperatures, the force difference at the same point of the gas spring under high and normal temperatures, and the standard stroke of the gas spring. The surface constraint rules include position constraint rules for restricting the air spring hinge point to be within the preset installation surface range of the vehicle body, and posture constraint rules for ensuring that the air spring maintains a safe clearance with surrounding components. The position constraint rule is as follows: the hinge point between the gas spring and the vehicle body must fall within the effective area of ​​the preset installation curved surface of the vehicle body, and the minimum gap between the gas spring and the edge of the curved surface shall not be less than 5mm. The hinge point between the gas spring and the cover must fall within the reinforcing rib area of ​​the inner panel of the front hood, and the horizontal distance between it and the front hood hinge must be no less than 30mm. The posture constraint rule is as follows: when the front hood is closed, the angle between the gas spring installation angle and the normal direction of the inner panel of the front hood is controlled between 15° and 30°. With the hood fully open, the angle between the gas spring and the inner hood panel and the windshield is ≥10°.

7. The CATIA tool-aided design method for a four-link automotive hood according to claim 6, characterized in that: The arbitrary state gas spring model line is as follows: Based on the natural length of the gas spring, the preset curved surface of the vehicle body, and the initial coordinates of the hinge point of the cover, the coordinates of the hinge point of the gas spring on the curved surface of the vehicle body are calculated using the initial coordinates of the hinge point of the cover as a reference. Obtain the geometric boundary between the surrounding components and the gas spring, and calculate the minimum distance between the vehicle body hinge point and the geometric boundary; Based on the normal vector of the initial coordinates of the hood hinge point, calculate the direction vector of the gas spring. The normal vector and the direction vector of the gas spring must satisfy the angle constraint: the angle formed between the normal direction of the inner panel of the hood at the initial position of the hood hinge point and the thrust direction of the gas spring itself needs to be controlled within the range of the hood opening angle 15° to 30°. Obtain the hinge coordinates of the hood and calculate the horizontal distance between the hinge coordinates of the hood and the hinge point coordinates of the vehicle body. Based on the natural length of the gas spring, the preset curved surface of the vehicle body, the coordinates of the hinge point of the gas spring on the curved surface of the vehicle body, the minimum distance between the hinge point of the vehicle body and the geometric boundary, the angle constraint between the normal vector and the direction vector of the gas spring, and the horizontal distance between the hinge coordinates of the hood and the hinge point of the vehicle body, an arbitrary state gas spring model line is constructed.

8. The CATIA tool-aided design method for a four-link automotive hood according to claim 1, characterized in that: The process parameters include parameters for calculating the coordinates of the gas spring hinge point, parameters for verifying the gaps between surrounding components, parameters for constraining the direction vector of the gas spring, and parameters for matching the horizontal distance between the front hood and the hinge point of the vehicle body. By setting force and stroke constraint rules, process parameters are obtained by torque balancing, temperature correction, and clearance calculation. The force constraint rule is specifically as follows: Normal temperature operating conditions: manual door opening force ≤30N, manual door closing force ≥-150N; Extreme temperature conditions: opening force at -30℃ ≤ 35N, closing force at 50℃ ≥ -160N, with a deviation from the force value at normal temperature not exceeding 15%; The travel constraint rules are as follows: The maximum compression stroke of a gas spring must not exceed its standard stroke; With the hood in any open position, the length of the gas spring is controlled within the tolerance range of the natural extension and contraction length of the gas spring; The minimum clearance between the gas spring and surrounding components is ≥5mm; Operating conditions after force decay: When the gas spring force decays to 92% of the rated value, the manual door closing force at low temperature is ≥-165N.

9. The CATIA tool-aided design method for a four-link automotive hood according to claim 8, characterized in that: The torque balance specifically refers to: Obtain the weight of the hood, the total frictional torque at the hinge point, the instantaneous center coordinates in the four-bar linkage model under any state, and the center coordinates of the hood. Calculate the center arm of the hood and substitute it into the torque balance formula to calculate the actual supporting force of the gas spring under the current posture. The temperature correction specifically refers to: Based on the actual supporting force of the gas spring in the current posture, calculate the actual force values ​​of the gas spring at low and high temperatures; The gap calculation is specifically as follows: Obtain the hinge point coordinates of the gas spring model line in any state, as well as the surface geometry parameters of the surrounding components, and calculate the minimum clearance between the gas spring rod and the surrounding components.

10. The CATIA tool-aided design method for a four-link automotive hood according to claim 9, characterized in that: Compare the torque balance value, the actual force value of the gas spring under low temperature and high temperature with the force constraint rules. If the torque balance value, the actual force value of the gas spring under low temperature and high temperature are all within the force constraint rules, then it is determined to be a compliant parameter, and the compliant parameter is matched to the record type parameter of the corresponding working condition. Compare the minimum clearance with the travel constraint rules. If the minimum clearance meets the travel constraint rules, it is determined to be a compliant parameter, and the compliant parameter is matched to the record-type parameter of the corresponding working condition.

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