A method for calculating and evaluating the steering transmission ratio fluctuation of a vehicle

Abstract

This application relates to the field of steering ratio fluctuation calculation and evaluation technology, specifically, to a method for calculating and evaluating automotive steering ratio fluctuation, comprising the following: constructing an ADAMS improved steering system model, which includes upper fork modeling, lower fork modeling, and column adjustment modeling; specifically, a dual revolute joint modeling method is adopted, namely a first revolute joint and a second revolute joint; obtaining a front suspension model and simulation boundary conditions; assembling the front suspension model and the steering system model; and simulating the process to obtain the instantaneous steering ratio fluctuation curve; performing a multi-dimensional evaluation based on the instantaneous steering ratio fluctuation curve; and determining whether to adjust the phase angle based on the multi-dimensional evaluation results to simulate the actual structure of the steering intermediate shaft universal joint, thereby avoiding discrepancies between simulation results and reality.

Description

Technical Field

[0001] This application relates to the field of steering ratio fluctuation calculation and evaluation technology, and more specifically, to a method for calculating and evaluating automotive steering ratio fluctuation. Background Technology

[0002] As automotive knowledge becomes more widespread, the torque fluctuation that affects steering wheel feel during steering is receiving increasing attention. Steering system design primarily assesses torque fluctuation through the fluctuation of steering ratio. However, the fluctuation of steering ratio is often limited by the layout of ergonomic hard points (such as the corresponding mounting points of the steering wheel and steering components), platformization, and generalization. This leads to compromises in the layout of steering system hard points, resulting in poor steering ratio performance in real vehicles. In related technologies, the steering system model is built using the built-in templates of ADAMS software, and the transmission ratio fluctuation is simulated and calculated by changing the hardpoint method (industry target ≤10%). However, the universal joint hinge method in the ADAMS software's built-in templates has a fixed ten-byte direction, which often does not match the actual structure, leading to inaccurate simulation results. Furthermore, the inability to optimize by changing the phase angle results in poor performance and fails to effectively assess symmetry. Automakers often develop platforms for sedans, SUVs, and hatchbacks simultaneously, resulting in multiple sets of hardpoints in the steering system. Cost reduction and standardization require the column and steering gear hardware to be reused, meaning only the steering intermediate shaft hardware is adjustable. This severely limits the optimization of the steering transmission ratio, making it difficult to quickly and effectively assess the steering transmission ratio fluctuation. Therefore, we propose a method for calculating and evaluating automotive steering transmission ratio fluctuation. Summary of the Invention

[0003] The purpose of this application is to address the problem that automakers often develop multiple steering systems for sedans, SUVs, and hatchbacks simultaneously when using a platform model. This results in multiple hard points in the steering system, and the cost reduction and standardization requirements necessitate the reuse of the column and steering gear hardware, meaning that only the steering intermediate shaft hardware is adjustable. This severely limits the optimization of the steering ratio, and therefore the fluctuation of the steering ratio often cannot be quickly and effectively evaluated.

[0004] To accurately simulate the universal joint structure of a real vehicle steering system, avoid discrepancies between simulation results and reality, and enable rapid adjustment of the steering gear structure without altering the ergonomic hardpoints through parameterized phase angles and column vertical positions, thereby adjusting steering ratio fluctuations, this application presents a method for calculating and evaluating automotive steering ratio fluctuations, comprising the following: A steering system model is constructed, which includes upper fork modeling, lower fork modeling, and column adjustment modeling. A dual revolute joint model is adopted, namely a first revolute joint and a second revolute joint. The steering column in the steering system model has a built-in spindle, and the steering wheel and the spindle are assembled with scale alignment. Obtain the front suspension model and simulation boundary conditions; assemble the front suspension model with the steering system model; and run the simulation to obtain the instantaneous steering transmission ratio fluctuation curve; A multi-dimensional evaluation is performed based on the instantaneous steering ratio fluctuation curve; the phase angle is then adjusted based on the multi-dimensional evaluation results.

[0005] As a further improvement to this technical solution, the upper fork modeling is used to restore the actual hinge structure; the lower fork modeling is used to associate phase angle parameters; and the column adjustment modeling is used for parametric adjustment.

[0006] As a further improvement to this technical solution, the upper fork modeling specifically involves: Component definition and hard point positioning: Create the upper fork solid component and define the spatial coordinates of the upper fork center point B; First Revolute joint: Create the first Revolute joint along the input axis B-in, connecting the steering column and the upper fork UJ1; the line connecting the input axis B-in with the steering wheel center point A and the upper fork center point B is perpendicular, and the direction vector of the input axis B-in is defined by the line connecting the upper fork center point B and the upper fork input side fork arm, limiting the upper fork center point B and the upper fork input side fork arm to rotate only around the input axis B-in; Second Revolute joint: Create a second Revolute joint along the upper fork output shaft B-out, connecting the upper fork UJ1 with the steering intermediate shaft; the upper fork output shaft B-out is perpendicular to the line connecting the input shaft B-in and the center point B of the upper fork and the center point C of the lower fork. Parametric constraint verification: Set parametric variables to associate the spatial relationship between the input axis B-in and the upper fork output axis B-out, and verify the rotational degrees of freedom of the double first revolute joint and the second revolute joint.

[0007] As a further improvement to this technical solution, the lower fork modeling specifically involves: Component definition and hard point calibration: Create the lower fork solid component and locate the lower fork center point C; First Revolute joint: Create the first Revolute joint along the lower fork input shaft C-in, connecting the steering intermediate shaft and the lower fork UJ2; the lower fork input shaft C-in must be perpendicular to the line connecting the upper fork center point B and the lower fork center point C, establishing a connection with the upper fork output shaft B-out; Second Revolute joint: Create a second Revolute joint along the lower fork output shaft C-out, connecting the lower fork UJ2 with the steering gear input shaft; the lower fork output shaft C-out is perpendicular to the line connecting the input shaft B-in and the lower fork center point C and the input shaft hard point D, establishing a parametric association with the lower fork input shaft C-in; Phase angle parameterization configuration: Create the first angle parameter Set an adjustable range, and use a parameterized structure box to connect the direction vector of the lower fork input axis C-in with the direction vector and phase angle of the lower fork output axis C-out. Binding; Linkage verification and optimization: Adjusting the phase angle Observe the motion coordination and the change of the inter-shaft angle of the first and second revolute pairs to verify whether the transmission ratio fluctuation curve changes with the phase angle. The adjustments exhibit a regular pattern of change.

[0008] As a further improvement to this technical solution, the tubing adjustment modeling specifically includes: Adjustment bracket and hard point definition: Create the adjustment bracket for the steering column and define the spatial position of the upper and lower adjustment shafts P of the steering column; First Revolute pair: Create the first Revolute pair by connecting the center point A of the steering wheel and the center point B of the upper fork, and connect the steering column and the adjustment bracket; The line connecting the center point A of the steering wheel and the center point B of the upper fork is the axis of the steering column; Second Revolute joint: Create a second Revolute joint along the upper and lower adjustment axis P of the steering column, connect the adjustment bracket to the vehicle body, and limit the bracket to rotate only around the upper and lower adjustment axis P of the steering column; Adjusting Angle Parameterization Driven: Creating a Second Angle Parameter Define upward adjustment as a positive angle and downward adjustment as a negative angle, and convert the angle value into a radian value through the displacement driving function; Drive correlation and simulation verification: The drive function after radian conversion is correlated to the Revolute pair between the adjustment bracket and the vehicle body. Different α values ​​are set, and the simulation is run to observe the flexibility of the column up and down adjustment and the stability of the steering wheel center point A position, and to verify the motion coordination of the steering system under different adjustment positions.

[0009] As a further improvement to this technical solution, the instantaneous steering transmission ratio fluctuation curve is specifically as follows: Set the full steering range of the steering wheel and the frequency sweep drive range, select a fixed drive angle within the frequency sweep drive range, generate a steering drive signal, and use the steering drive signal to apply a steering angle drive to the steering wheel; After obtaining the output steering drive signal, the steering wheel angle is the steering wheel angle at the Revolute joint of the steering column and the upper fork UJ1. The steering knuckle angle, i.e., the left front wheel steering angle, is collected at the Revolute joint between the steering knuckle and the lower control arm. Right front wheel steering angle ; Calculate the instantaneous steering gear ratio; By associating the instantaneous steering ratio with the corresponding steering wheel angle according to the steering sequence, an instantaneous steering ratio fluctuation curve is generated.

[0010] As a further improvement to this technical solution, the instantaneous steering transmission ratio is obtained by calculating the average wheel angle and numerically differentiating the average steering wheel angle and wheel angle.

[0011] As a further improvement to this technical solution, the instantaneous steering transmission ratio fluctuation curve is generated, specifically based on the steering wheel angle. The horizontal axis represents the instantaneous steering ratio. Using the vertical axis as the ordinate, a functional relationship is established to obtain the instantaneous steering transmission ratio fluctuation curve.

[0012] As a further improvement to this technical solution, the multi-dimensional evaluation specifically includes: Calculate the transmission ratio fluctuation ζ, peak offset angle θ, and fluctuation symmetry ε, and set corresponding evaluation thresholds for transmission ratio fluctuation ζ, peak offset angle θ, and fluctuation symmetry ε respectively. Then, determine whether to adjust the phase angle by evaluating the corresponding transmission ratio fluctuation ζ, peak offset angle θ, and fluctuation symmetry ε at the evaluation thresholds. If the transmission ratio fluctuation ζ, peak offset angle θ, and fluctuation symmetry ε do not meet the corresponding evaluation thresholds, it is determined that the phase angle needs to be adjusted.

[0013] As a further improvement to this technical solution, the transmission ratio fluctuation ζ, peak offset angle θ, and fluctuation symmetry ε are as follows: ; in, The peak value at the zero steering position on the instantaneous steering ratio fluctuation curve. The trough value adjacent to Peak at the zero turning position of the same fluctuation curve; The peak offset angle θ is as follows: ; in, Instantaneous transmission ratio reaches peak At that time, the corresponding steering wheel angle; and θ is positive when the peak is to the right of the zero steering position and negative when it is to the left; the wave symmetry ε is as follows: ; in, Peak offset angle The absolute value, This is the angle-to-radian conversion factor. It is a sine function.

[0014] Beneficial effects: This application can accurately simulate the universal joint structure of the steering system of a real vehicle, avoiding discrepancies between simulation results and reality. It can also quickly adjust the steering gear structure to achieve the purpose of adjusting the steering ratio fluctuation by adjusting the parameterized phase angle and column position without changing the human-machine hardpoint. Furthermore, it can quickly obtain the steering ratio curve and fluctuation percentage. The added peak offset angle and symmetry evaluation method can comprehensively evaluate the steering system fluctuation performance. Especially in the development of the same platform, it can quickly determine whether different layouts of the steering system can meet the requirements of maximum versatility and performance balance.

[0015] In addition to the purposes, features, and advantages described above, this application has other purposes, features, and advantages. A further detailed description of this application will be provided below with reference to the figures. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the steering system structure; Figure 2 This is a schematic diagram of the existing ADAMS built-in steering system model; Figure 3 A schematic diagram of the ADAMS improved steering system model provided in this application; Figure 4 This is a schematic diagram illustrating the volatility parameters of the steering mechanism in this application; Figure 5 A schematic diagram of the B-point hinge method and modeling provided in this application; Figure 6 This application provides a schematic diagram of the C-point hinge method and its modeling. Figure 7 The phase and ADAMS parametric modeling diagram provided for this application; Figure 8 A schematic diagram of parametric modeling for the vertical adjustment of the steering column provided in this application; Figure 9 This is a schematic diagram of the ADAMS steering ratio processing method provided in this application; Figure 10 A schematic diagram comparing the transmission ratio fluctuation curves of the existing built-in template versus the improved modeling of this application; Figure 11 Schematic diagram of the steering system layout for vehicles developed for the G platform; Figure 12 Schematic diagram of the steering ratio fluctuation curve when adjusting the phase angle δ for right-hand drive SUVs; Figure 13 A schematic diagram of the hand force symmetry test of a modified SUVS1 with right-hand drive (right-hand drive-1 configuration); Figure 14 This is a schematic diagram illustrating the fluctuation of steering ratio among four models on the same platform as G.

[0017] Legend: 1. Steering column; 11. Spindle; 12. Adjusting bracket; 2. Steering intermediate shaft; 3. Steering gear; 31. Input shaft of steering gear. Detailed Implementation

[0018] The technical solutions in 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, and 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.

[0019] refer to Figures 1-14 As shown, a method for calculating and evaluating steering ratio fluctuation in automobiles can quickly derive the steering ratio curve and fluctuation percentage. The added peak offset angle and symmetry evaluation methods can comprehensively assess the fluctuation performance of the steering system. Especially in platform-based development, it can quickly determine whether different steering system layouts can meet maximum versatility and performance balance, including the following: refer to Figure 3 As shown, an improved steering system model for ADAMS is constructed, which includes upper fork modeling, lower fork modeling, and column adjustment modeling. refer to Figure 5 , Figure 6 As shown, the steering system model uses key hard points of the steering system (including but not limited to steering wheel center point A, upper fork center point B, lower fork center point C, and steering gear input shaft hard point D) as spatial positioning references. It is developed with the platform-based universality of steering column 1 / steering gear 3 and only the steering intermediate shaft 2 being adjustable. It also uses a double revolute joint to replicate the actual vehicle structure and parametric association to achieve flexible adjustment. In addition, the steering column in the steering system model has a built-in spindle 11. The steering wheel and spindle 11 are assembled with scale alignment. The spindle 11 is the core transmission component of the steering column 1 and bears the direct transmission of steering torque of the steering wheel. The aforementioned double revolute joints include a first revolute joint and a second revolute joint: Taking the upper fork UJ1 as an example, a secondary rotation constraint is constructed at the center point B of the upper fork: the first Revolute joint connects the steering column 1 and the upper fork UJ1 with the input shaft B-in as the center. The axis direction is perpendicular to the line connecting the center point A of the steering wheel and the center point B of the upper fork. By defining the line connecting the inherent feature point of the upper fork UJ1 and the center point B of the upper fork, the rotational torque is ensured to be accurately transmitted along the axis of the column. The second Revolute joint, with the upper fork output shaft B-out as the center, connects the upper fork UJ1 to the steering intermediate shaft 2, and the axial direction is determined by spatial cross multiplication (… It is generated and strictly satisfies the dual constraints of being orthogonal to the input axis B-in and perpendicular to the line connecting the center point B of the upper fork and the center point C of the lower fork (the axis of the steering intermediate axis 2); The lower fork UJ2 uses the same constraint logic at the lower fork center point C: the lower fork input shaft C-in is the first Revolute sub-center, connecting the steering intermediate shaft 2 and the lower fork UJ2, and the axial direction is perpendicular to the line connecting the upper fork center point B and the lower fork center point C; the lower fork output shaft C-out is the second Revolute sub-center, connecting the lower fork UJ2 and the steering gear input shaft, and the axial direction is orthogonal to the lower fork input shaft C-in and perpendicular to the line connecting the lower fork center point C and the input shaft hard point D, forming a continuous orthogonal constraint chain.

[0020] Furthermore, the orthogonal constraints of the first and second revolute pairs ensure that the steering motion transmission path (steering wheel → steering column 1 → upper fork UJ1 → steering intermediate shaft 2 → lower fork UJ2 → steering gear 3) completely replicates the mechanical characteristics of the actual vehicle. Specifically, when the steering wheel is rotated using a fixed drive angle, the steering column 1 drives the lower fork UJ2 to rotate around the input shaft B-in through the first revolute pair of the upper fork UJ1. Then, through the second revolute pair, the steering intermediate shaft 2 is driven to transmit torque along the line connecting the center point B of the upper fork and the center point C of the lower fork. The lower fork, through the same double revolute pairs (first and second revolute pairs), works together to transmit torque to the steering gear input shaft without deviation, ensuring the authenticity of the angle conversion and torque transmission.

[0021] refer to Figure 7 As shown, the steering system model is constructed as follows: Upper fork modeling: The hinge structure of the real vehicle's cross-shaped universal joint is accurately replicated using a double revolute joint. Simultaneously, parametric associations are established to ensure that the power transmission between the steering column 1 and the steering intermediate shaft 2 conforms to the laws of motion of the actual object, laying the foundation for subsequent phase angle... Optimization lays the foundation; by constructing two mutually perpendicular revolute joints at the center point B of the upper fork, the rotational degrees of freedom of the steering column P and the upper fork UJ1, and the upper fork UJ2 and the steering intermediate shaft 2 are respectively limited. This not only solves the defect that the universal joint axis direction of the ADAMS template is not adjustable, but also enables flexible adaptation of the axis direction through parametric association, ensuring that the simulation model is consistent with the actual vehicle structure and improving the accuracy of transmission ratio fluctuation calculation. The specific working principle is as follows: Component definition and hard point positioning: Create the upper fork UJ1 solid component, define the spatial coordinates of the upper fork center point B (center point of the upper fork of the steering intermediate shaft 2, the human-machine hard point of the steering system), and ensure that its assembly position matches the actual vehicle layout with the steering column 1 and the steering intermediate shaft 2. First Revolute joint (steering column P-upper fork UJ1 connection): Create a Revolute joint along the input axis B-in (upper fork input axis) to connect steering column 1 and upper fork UJ1; the input axis B-in must be perpendicular to the line connecting hard point A (steering wheel center point) and B (AB line). The direction vector of the input axis B-in is defined by the line connecting the upper fork center point B and the input side fork arm of upper fork UJ1, limiting the two to only rotate around the input axis B-in; The second Revolute joint (upper fork-steering intermediate shaft 2 connection): A Revolute joint is created along the upper fork output shaft B-out (upper fork output shaft) to connect the upper fork UJ1 and the steering intermediate shaft 2; the upper fork output shaft B-out must be perpendicular to the line connecting the input shaft B-in and the center points B and C of the upper fork (the BC line) to establish an association with the input shaft B-in, realize the parameterized drive of the upper fork output shaft B-out, and ensure the structural characteristics of the dual-axis orthogonal universal joint. Parametric constraint verification: Set parametric variables to associate the spatial relationship between the input shaft B-in and the upper fork output shaft B-out, and verify whether the rotational degrees of freedom of the double rotary joint meet the requirements (only allowed to rotate around their respective axes, with no additional degrees of freedom interference), ensuring that there is no jamming or simulation deviation during power transmission.

[0022] Lower fork modeling: refer to Figure 6 As shown, the lower fork UJ2 is specifically the transmission connection hub between the steering intermediate shaft 2 and the steering gear 3. Specifically, it replicates the double orthogonal rotation characteristics of the vehicle universal joint through double revolute joints (first revolute joint and second revolute joint), and introduces phase angle parameterization association to realize the function of adjusting the transmission angle of the steering intermediate shaft 2 without changing the hard point, and adapts to the constraint that only the steering intermediate shaft 2 is adjustable. The lower section fork UJ2 is connected to the steering intermediate shaft 2 at one end and the steering gear input shaft 31 of the steering gear 3 at the other end. Its specific function is as follows: Reproduce the flexible transmission of the universal joint of the lower fork of the actual vehicle (rotation around a double orthogonal axis). By adjusting the phase angle, the direction of the drive shaft is adjusted synchronously to optimize the fluctuation of the steering ratio; Parameterized linkage avoids adaptation costs caused by hard point changes.

[0023] The specific principle of lower fork modeling is as follows: Using a double revolute joint and phase angle as the core, a hinge structure identical to that of the actual vehicle is constructed at the center point C of the lower fork, relating the spatial angle (phase angle) between the upper fork output shaft B-out and the lower fork input shaft C-in. This allows for flexible optimization of steering gear ratio fluctuations; the dual revolute joint structure (first revolute joint, second revolute joint) ensures reliable power transmission between the steering intermediate shaft 2 and the input shaft of the steering gear 3; and phase angle parameterization allows for adjustment of the phase angle without changing the center point (A, B, C, D) of the human-machine steering wheel. This involves changing the universal joint transmission phase, thereby offsetting the transmission ratio fluctuations caused by the inter-shaft angle, and solving the performance optimization problem under the constraints of hard points in platform-based vehicle models; more details are as follows: Component definition and hard point calibration: Create the lower fork UJ2 solid component, locate the lower fork center point C (center point of the lower fork of the steering intermediate shaft 2, hard point of the steering system layout), and ensure that its assembly position with the steering intermediate shaft 2 and the input shaft 31 conforms to the actual vehicle design, and that the line connecting it to the input shaft hard point D (CD line) meets the spatial layout requirements.

[0024] First Revolute joint (Steering intermediate shaft 2 - lower fork UJ2 connection): Create a Revolute joint along the lower fork input shaft C-in, connecting steering intermediate shaft 2 and lower fork UJ2; the lower fork input shaft C-in must be perpendicular to the BC line, and its association with the upper fork output shaft B-out is established through a parameterized structure box, specifying the phase angle. Definition (Looking from the center point B of the upper fork to the center point C of the lower fork, the lower fork input shaft C-in rotates clockwise around the upper fork output shaft B-out as a positive angle, and counterclockwise as a negative angle).

[0025] Second Revolute pair (lower fork UJ2-steering gear 3 connection): Create a Revolute pair along the lower fork output shaft C-out, connecting the lower fork UJ2 and the steering gear 3 input shaft 31; the lower fork output shaft C-out must be perpendicular to both the lower fork input shaft C-in and the CD line, establishing a parameterized association with the lower fork input shaft C-in, ensuring that the lower fork output shaft C-out changes synchronously with the lower fork input shaft C-in, maintaining the orthogonal transmission characteristics of the two shafts; Phase angle parameterization configuration: Create the first angle parameter The adjustable range is set to -80° to 90°. The direction vector of the lower fork input axis C-in is connected to the direction vector of the upper fork output axis B-out and the phase angle through the parameterized structure box. Binding (expression: To achieve phase angle Adjust the synchronization of the lower fork input shaft C-in and the lower fork output shaft C-out; Linkage verification and optimization: Adjusting the phase angle Observe the kinematic coordination and the change in the inter-shaft angle of the two revolute joints (first revolute joint and second revolute joint) to verify whether the transmission ratio fluctuation curve changes with the phase angle. The adjustments exhibit regular changes to ensure that the parametric model meets optimization requirements.

[0026] refer to Figure 8 As shown, the column adjustment modeling: The column adjustment modeling replicates the mechanical trajectory of the up and down adjustment of the steering wheel of the real vehicle through the double rotary joints (first revolute joint and second revolute joint) of the steering column 1-adjustment bracket 12-vehicle body, and introduces angle parameterization drive to realize the function of calculating the transmission ratio fluctuation of different adjustment positions without remodeling, which meets the needs of ergonomics for adapting drivers of different body types. The adjustment object of the column adjustment is the steering column 1 (platform component, initial angle fixed); Its specific function is as follows: Reproduce the trajectory of the steering wheel swinging up and down around the steering column adjustment axis P of a real car; The steering ratio fluctuation at each position is calculated by quickly switching the adjustment position through parameterized drive.

[0027] The working principle of the steering column adjustment model is as follows: Through the combined structure of the adjustment bracket 12, two revolute joints (first and second revolute joints), and angle parameterization drive, the vertical adjustment function of the steering column in a real vehicle is simulated. This achieves parameterized adjustment of the column position without changing the center point A of the steering wheel. The adjustment bracket 12 acts as a transition component, limiting the rotational degrees of freedom between the steering column 1 and the adjustment bracket 12, and between the adjustment bracket 12 and the vehicle body, respectively, through the two revolute joints (first and second revolute joints). Adjusting the angle parameters drives the adjustment bracket 12 to rotate around the vertical adjustment axis P of the steering column, thereby causing the column to swing up and down. This allows for rapid simulation of steering ratio fluctuations at different adjustment positions, adapting to the usage needs of drivers of different heights, while ensuring the universality of the column hardware across platform vehicles. A more detailed explanation of the principle follows: Adjustment bracket 12 and hard point definition: Create adjustment bracket 12, clarify the spatial position of the upper and lower adjustment axis P (Y direction, upper and lower adjustment axis of steering column 1), and ensure that its assembly relationship with the body and steering column 1 conforms to the actual vehicle ergonomic design, and the relative position of the steering wheel center point A remains unchanged. First Revolute joint (steering column 1-adjusting bracket 12 connection): A Revolute joint is created along the AB line (steering column axis) to connect steering column 1 and adjusting bracket 12, limiting the two to only rotate around the AB axis, thus satisfying the steering transmission requirements of steering column 1 itself. Second Revolute joint (adjustment bracket 12-body connection): A Revolute joint is created along the up-down adjustment axis P of the steering column 1, connecting the adjustment bracket 12 to the body, limiting the bracket to rotate only around the up-down adjustment axis P of the steering column 1, providing a degree of freedom of motion for the up-down adjustment of the steering column 1; Adjusting Angle Parameterization Driven: Creating a Second Angle Parameter Define upward adjustment as a positive angle and downward adjustment as a negative angle. Convert the angle value to a radian value using a displacement-driven function (expression: ...). , 180 / (approximate value of ) Drive association and simulation verification: The drive function after radian conversion is associated with the Revolute pair between the adjustment bracket 12 and the vehicle body. Different α values ​​(such as -5°, 0°, 5°) are set, and the simulation is run to observe the flexibility of the steering column 1 in the up and down adjustment and the stability of the position of point A. The motion coordination of the steering system under different adjustment positions is verified to ensure the accuracy of the transmission ratio fluctuation calculation. The aforementioned upper fork modeling provides the basic articulated structure for power transmission, the lower fork modeling achieves transmission optimization through phase angle parameterization, and the column adjustment modeling adapts to changes in usage scenarios. All three adopt a double revolute joint (first revolute joint, second revolute joint) structure to replicate the characteristics of the actual vehicle, and the parameterization design remains consistent, ensuring the integrity and coordination of the steering system model. Furthermore, the core hard points such as A, B, C, and D were not modified during the modeling process, allowing for the complete reuse of platform components such as steering column 1 and steering gear 3, with only the phase angle of the steering intermediate shaft 2 being adjusted. With adjustments and minor tweaks to the upper fork of the UJ1, it can be adapted to different models on the same platform, such as sedans, SUVs, and left- or right-hand drive vehicles, meeting the requirements for cost reduction and universalization, and can quickly assess the fluctuation of steering transmission ratios across multiple models.

[0028] refer to Figure 4 As shown, the front suspension model and simulation boundary conditions are obtained; the front suspension model and the steering system model are assembled; and the simulation is run to obtain the instantaneous steering transmission ratio fluctuation curve. The front suspension model includes core components such as steering knuckle, tie rod, lower control arm, kingpin, spring, and shock absorber, as well as the hinge constraints between these components (such as the Revolute joint between the steering knuckle and the lower control arm, and the Ball joint between the tie rod and the steering knuckle). By assembling the front suspension model and the steering system model, the mapping relationship is strictly matched with the actual vehicle's mechanical structure to ensure that the kinematic chain is without deviation. When assembling the front suspension model and the steering system model, the steering wheel center point A is used as the reference to ensure that the hard point and the hard point of the front suspension are completely aligned in the vehicle coordinate system. For example, the lower fork center point C needs to coincide with the coordinate of the steering gear mounting bracket of the front suspension, and the input shaft hard point D needs to match the coordinate of the output end of the steering gear rack to avoid motion interference or transmission clearance caused by hard point offset. refer to Figure 9 As shown (specifically, the steering gear tie rod and wheel drive logic), this includes matching key connection relationships: The rigid connection between the steering gear 3 and the front suspension tie rod: The linear motion of the steering gear rack needs to be transmitted to the front suspension tie rod through the rack-tie rod joint, and then the tie rod drives the steering knuckle to rotate around the kingpin (the steering knuckle is rigidly connected to the wheel, and the steering knuckle angle is the wheel angle). Alignment is required during assembly. Figure 1 The input shaft hardpoint D and the front suspension tie rod mounting hardpoint are used to ensure that the force and motion transmission path conforms to the actual vehicle.

[0029] Constraint coordination between the steering system and the front suspension: The K&C characteristics of the front suspension (such as the steering stiffness of the steering knuckle and the elastic deformation of the tie rod) directly affect the realism of the wheel turning angle. Therefore, the simulation boundary conditions include the static vertical load of the front suspension (matching the pressure of the vehicle body on the suspension under the full load condition of the actual vehicle), the friction coefficient of each hinge of the steering system (the friction coefficient of the upper fork UJ1, lower fork UJ2 and Revolute pair is set to 0.01~0.03), the material properties of the components (density, elastic modulus, etc.), and the stiffness and damping characteristics of the steering gear rack. The instantaneous steering ratio fluctuation curve is as follows: Set the full steering range of the steering wheel (covering the steering requirements of the vehicle under all working conditions, including straight driving, turning, and parking, and matching the physical constraints of the steering gear rack travel and the front suspension steering limit), as well as the frequency sweep drive range. Select a fixed drive angle within the frequency sweep drive range and generate a steering drive signal to simulate the driver's steering wheel rotation. Use the steering drive signal to apply a steering angle drive to the steering wheel (or steering column 1): ; in: The steering wheel angle changes with time t, which is the output steering drive signal, reflecting the rotation position of the steering wheel at different times; To fix the sweep frequency drive angular velocity, the sweep frequency drive range is selected. For example, if the sweep frequency drive range is [5° / s, 10° / s], then the fixed sweep frequency drive angular velocities are 5° / s, 7.5° / s, and 10° / s, which determine the steering speed. The start / stop transition time can be uniformly set to 0.5s to achieve smooth start and stop of steering, avoiding fixed sweep frequency drive angular velocity. Simulated shock caused by a step jump; The simulation time refers to the time variable of the simulation process, covering the period from 0 to the total simulation duration. + The complete cycle of ); This is the moment when the uniform speed turning ends; It is a cosine function used to generate a smooth transition curve. By utilizing the continuous change characteristic of the cosine function from 0 to 1 to 0, it can achieve a shock-free transition of rotation angle and angular velocity. The aforementioned full steering range is set based on the steering wheel steering limits, steering gear rack travel, and front suspension steering limits of a real vehicle, ensuring that the simulation has no motion interference and covers common steering scenarios in real vehicles. The specific working principle is as follows: refer to Figure 10 , Figure 12 The sweep frequency drive range is typically -500° to +500°, depending on the actual steering wheel angle range from left to right full turn. The sweep frequency drive range is determined by the maximum travel of the steering gear rack: the effective travel of the steering gear rack (usually 100~150mm) is converted into the steering wheel angle through the steering gear transmission ratio (rack travel → maximum wheel angle → maximum steering wheel angle). This avoids setting the range too large, which could cause the rack to exceed its travel range and damage the steering gear in the simulation. If the sweep frequency drive range is too small, it will not be able to cover extreme scenarios such as low-speed parking and sharp turns.

[0030] Front suspension steering limit verification: The steering knuckle of the front suspension is limited by the structure of the kingpin and lower control arm. The maximum wheel turning angle is usually ±35°~±40° (different models vary). It is necessary to estimate the transmission ratio to inversely deduce the upper limit of the sweep frequency drive range: If the estimated transmission ratio is 14 (14° steering wheel rotation corresponds to 1° wheel rotation), then the maximum wheel turning angle ±35° corresponds to a steering wheel turning angle ±490°, which is consistent with the range of -500°~+500° in the real vehicle, ensuring that the wheel does not exceed the physical limit in the simulation; refer to Figure 1 , 5 6. After the steering drive signal is output, it is transmitted to the wheels through the steering system's transmission chain. The path perfectly matches the dynamic path of the actual vehicle's motion transmission: Steering wheel angle → Steering column 1 (rotates around axis AB) → Upper fork UJ1 (transmits motion via dual revolute joint, B-in→B-out) → Steering intermediate shaft 2 → Lower fork UJ2 (associated phase angle, C-in→C-out) → Steering gear 3 (input shaft rotation → rack linear motion) → Front suspension tie rod (rack drives tie rod translation) → Steering knuckle (rotates around kingpin) → Wheel (rotates synchronously with steering knuckle, generating wheel angle).

[0031] The dynamic constraints and loads of the aforementioned steering drive signal are as follows: Constraints: Key constraints such as the double revolute joints of the steering system (upper fork UJ1, lower fork UJ2) and the steering knuckle-kingpin revolute joint of the front suspension are retained, while unnecessary degrees of freedom are restricted (e.g., the wheel retains only the steering degree of freedom around the kingpin and the rotational degree of freedom around its own axis). Load: Apply static loads to the front suspension (such as the vertical load of the vehicle weight on the suspension) and frictional torques to the steering system (such as setting the friction coefficient of the upper fork UJ1 / lower fork UJ2 to 0.01~0.03 to simulate the friction of the real vehicle) to ensure that the simulated forces are consistent with those of the real vehicle.

[0032] After obtaining the output steering drive signal, the steering wheel angle is the steering wheel angle at the Revolute joint (input shaft B-in) between steering column 1 and upper fork UJ1. The steering knuckle angle, i.e., the wheel angle (left front wheel angle), is collected at the revolute joint (kingpin axis) between the steering knuckle and the lower control arm. Right front wheel steering angle Specifically: Because the steering wheel is rigidly connected to the steering column 1, the steering column 1 is connected to the upper fork UJ1 via a double Revolute joint at the center point B of the upper fork. The input shaft B-in (upper fork input shaft) is the initial reference shaft for steering torque transmission, and its angle is completely synchronized with the steering wheel angle (no transmission backlash). Therefore, the steering wheel angle... Data is collected at the Revolute sub-axis corresponding to input axis B-in; The wheel and the steering knuckle of the front suspension are rigidly fixed. Therefore, the rotation angle of the steering knuckle around the kingpin (the axis connecting the steering knuckle and the lower control arm) is the wheel turning angle. Calculate the instantaneous steering gear ratio: Calculate the mean wheel angle ; The instantaneous steering gear ratio (i.e., the change in steering wheel angle required for a unit change in wheel angle) can be obtained by numerically differentiating the mean values ​​of the steering wheel angle and the wheel angle. Instantaneous differentiation can accurately capture the fluctuation of the gear ratio at every instant. The specific expression is as follows: ; in, The simulation time step is set to 0.01s to 0.05s to ensure that minute fluctuations are captured; This is the current simulation moment; By associating the instantaneous steering ratio with the corresponding steering wheel angle according to the steering sequence, an instantaneous steering ratio fluctuation curve is generated, specifically based on the steering wheel angle. The horizontal axis (x-axis) represents the instantaneous steering gear ratio. Using the y-axis as the vertical axis, a functional relationship is established to obtain the instantaneous steering gear ratio fluctuation curve; the functional relationship is: .

[0033] A multi-dimensional evaluation is performed based on the instantaneous steering ratio fluctuation curve; the phase angle is then adjusted based on the multi-dimensional evaluation results. The working principle of multi-dimensional assessment is as follows: Calculate the transmission ratio fluctuation ζ, peak offset angle θ, and fluctuation symmetry ε, and set corresponding evaluation thresholds for transmission ratio fluctuation ζ, peak offset angle θ, and fluctuation symmetry ε respectively. Then, determine whether to adjust the phase angle by evaluating the corresponding transmission ratio fluctuation ζ, peak offset angle θ, and fluctuation symmetry ε at the evaluation thresholds. The evaluation thresholds for transmission ratio fluctuation ζ, peak offset angle θ, and fluctuation symmetry ε are as follows: Fluctuation threshold Offset threshold Symmetric threshold ; If the transmission ratio fluctuation ζ, peak offset angle θ, and fluctuation symmetry ε do not meet the corresponding evaluation threshold (i.e., transmission ratio fluctuation ζ > fluctuation threshold) Offset threshold lower limit <Peak offset angle Peak offset angle <Offset threshold upper limit Wave symmetry ε < symmetry threshold If the steering system transmission smoothness, fluctuation offset control, or left and right steering consistency does not meet the design requirements, it is determined that the phase angle needs to be adjusted to optimize steering feel and handling stability. When adjusting, the adjustment range and corresponding adjustment step size can be set for gradual adjustment. The transmission ratio fluctuation ζ is as follows: ; in, The zero steering position (steering wheel angle) on the instantaneous steering ratio fluctuation curve. =0°, corresponding to the straight-moving state of the actual vehicle) peak value (i.e. the maximum instantaneous transmission ratio in this area). The value of the trough adjacent to Peak1 at the zero turning position of the same ripple curve (i.e., the minimum instantaneous transmission ratio in this region). The peak offset angle θ is as follows: ; in, The steering wheel angle corresponding to when the instantaneous gear ratio reaches peak 1 (i.e., the position of the peak on the horizontal axis "steering wheel angle"); and the peak is located to the right of the zero steering position (steering wheel angle). When θ is >0° (corresponding to right turn of the steering wheel), it is positive and located on the left (steering wheel angle). When <0° (corresponding to the left turn direction), it is negative.

[0034] The wave symmetry ε is as follows: ; in, Peak offset angle The absolute value, This is the angle-to-radian conversion factor. It is a sine function, and it utilizes the characteristics that it outputs 0 when x=0, ≈0.707 when x=45°, and 1 when x=90° to amplify the effect of the offset angle on symmetry.

[0035] refer to Figure 11 , Figure 13 As shown in this example, after adjusting the phase angle, if the transmission ratio fluctuation ζ, peak offset angle θ, and fluctuation symmetry ε still do not meet the corresponding evaluation thresholds, the hard point position of the steering system cannot be changed due to the vehicle layout limitations. Therefore, simply optimizing the phase angle is insufficient to completely offset the transmission ratio fluctuation caused by the difference in the inter-axle angle of the dual cross-shaft universal joint. Thus, only minor modifications to the steering intermediate shaft 2 are needed—for example, fine-tuning the fork arm angle of the upper fork UJ1 to optimize the universal joint phase matching, and adjusting the length of the steering intermediate shaft 2 to fine-tune the inter-axle angle. There is no need to replace the entire steering intermediate shaft 2, nor to modify core components such as the steering column 1 and steering gear 3, which are costly, complex to disassemble and assemble, and affect the platform's versatility. This approach precisely improves transmission smoothness, fluctuation offset, and symmetry while controlling costs, shortening the development cycle, and maintaining the reusability of platform components. The aforementioned phase angle is the spatial angle between the upper fork output shaft B-out and the lower fork input shaft C-in (viewed from point B to point C, the lower fork input shaft C-in rotates clockwise around the upper fork output shaft B-out to be positive, with an adjustment range of -80° to 90°). Specifically, the transmission phase is changed through parametric linkage to achieve precise optimization of steering ratio fluctuations. The specific correlation logic is as follows: A reference coordinate system is established with the center point B of the upper section fork as the origin, and the direction vector of the upper section fork output axis B-out is bound as the reference axis of the coordinate system. The lower section fork input axis C-in is associated with the upper section fork output axis B-out and the phase angle. The lower section fork output axis C-out is further associated with the lower section fork input axis C-in through orthogonal constraints, forming a linkage chain of phase angle → lower section fork input axis C-in → lower section fork output axis C-out. When modifying the phase angle parameter, the lower fork input shaft C-in will rotate synchronously around the upper fork output shaft B-out. The lower fork output shaft C-out will automatically adapt and adjust based on orthogonal constraints, without needing to change the hard point coordinates or reconstruct the constraint relationship.

[0036] refer to Figure 12 Steering ratio fluctuation curve of SUV S right-hand drive with phase angle δ: The steering ratio curve adjustment evaluation of SUV S right-hand drive vehicle is achieved by rapidly adjusting the phase angle δ within the range of -80° to 90°. Theoretically, it is confirmed that the steering ratio fluctuation of S right-hand drive vehicle cannot be optimized by adjusting the phase angle alone; Table 1 below shows the steering ratio fluctuation optimization analysis results of 4 models on the G platform.

[0037]

[0038] The meanings of the labels in the diagram are as follows: A: Steering wheel center point, steering system ergonomic hard point; B: Upper fork center point of steering intermediate shaft 2; C: Lower fork center point of steering intermediate shaft 2; D: Steering gear input shaft hard point; P: Steering column up / down adjustment shaft; B-in: Upper fork input shaft, initial input shaft; B-out: Upper fork output shaft; C-in: Lower fork input shaft; C-out: Lower fork output shaft; UJ1: Upper fork; UJ2: Lower fork.

[0039] The foregoing has shown and described the basic principles, main features, and advantages of this application. Those skilled in the art should understand that this application is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the application. Various changes and modifications can be made without departing from the spirit and scope of this application, and all such changes and modifications fall within the scope of the claims. The scope of protection of this application is defined by the appended claims and their equivalents.

Claims

1. A method for calculating and evaluating the fluctuation of automotive steering ratio, characterized in that, Including the following: A steering system model is constructed, which includes upper fork modeling, lower fork modeling, and column adjustment modeling; wherein, a double revolute joint modeling is adopted, namely the first revolute joint and the second revolute joint. The steering column in the steering system model has a built-in spindle (11), and the steering wheel and the spindle (11) are assembled with scale alignment. Obtain the front suspension model and simulation boundary conditions; assemble the front suspension model with the steering system model; and run the simulation to obtain the instantaneous steering transmission ratio fluctuation curve; A multi-dimensional evaluation is performed based on the instantaneous steering ratio fluctuation curve; the phase angle is then adjusted based on the multi-dimensional evaluation results.

2. The method for calculating and evaluating the fluctuation of automotive steering ratio according to claim 1, characterized in that: The upper fork model is used to recreate the actual hinge structure; the lower fork model is used to associate phase angle parameters; and the tubing adjustment model is used for parametric adjustment.

3. The method for calculating and evaluating the fluctuation of automotive steering ratio according to claim 2, characterized in that: The modeling of the upper fork is specifically as follows: Component definition and hard point positioning: Create the upper fork solid component and define the spatial coordinates of the upper fork center point B; First Revolute joint: Create the first Revolute joint along the input axis B-in, and connect the steering column (1) and the upper fork UJ1; the line connecting the input axis B-in with the steering wheel center point A and the upper fork center point B is perpendicular, and the direction vector of the input axis B-in is defined by the line connecting the upper fork center point B and the upper fork input side fork arm, limiting the upper fork center point B and the upper fork input side fork arm to only rotate around the input axis B-in; Second Revolute joint: Create a second Revolute joint along the upper fork output shaft B-out, connecting the upper fork UJ1 with the steering intermediate shaft (2); the upper fork output shaft B-out is perpendicular to the line connecting the input shaft B-in and the center point B of the upper fork and the center point C of the lower fork. Parametric constraint verification: Set parametric variables to associate the spatial relationship between the input axis B-in and the upper fork output axis B-out, and verify the rotational degrees of freedom of the double first revolute joint and the second revolute joint.

4. The method for calculating and evaluating the fluctuation of automotive steering ratio according to claim 3, characterized in that: The lower fork modeling specifically involves: Component definition and hard point calibration: Create the lower fork solid component and locate the lower fork center point C; First Revolute joint: Create the first Revolute joint along the lower fork input shaft C-in, and connect the steering intermediate shaft (2) with the lower fork UJ2; the lower fork input shaft C-in needs to be perpendicular to the line connecting the upper fork center point B and the lower fork center point C, and establish the association with the upper fork output shaft B-out; Second Revolute joint: Create a second Revolute joint along the lower fork output shaft C-out, connecting the lower fork UJ2 with the steering gear input shaft (31); the lower fork output shaft C-out is perpendicular to the line connecting the input shaft B-in and the lower fork center point C and the input shaft hard point D, establishing a parameterized association with the lower fork input shaft C-in; Phase angle parameterization configuration: Create the first angle parameter Set an adjustable range, and use a parameterized structure box to connect the direction vector of the lower fork input axis C-in with the direction vector and phase angle of the lower fork output axis C-out. Binding; Linkage verification and optimization: Adjusting the phase angle Observe the motion coordination and the change of the inter-shaft angle of the first and second revolute pairs to verify whether the transmission ratio fluctuation curve changes with the phase angle. The adjustments exhibit a regular pattern of change.

5. The method for calculating and evaluating the fluctuation of automotive steering ratio according to claim 4, characterized in that: The specific steps of the tubular adjustment modeling are as follows: Adjustment bracket and hard point definition: Create the column adjustment bracket and define the spatial position of the upper and lower adjustment shafts P of the steering column; First Revolute pair: Create the first Revolute pair by connecting the center point A of the steering wheel and the center point B of the upper fork, and connect the steering column (1) and the adjusting bracket (12). The line connecting the center point A of the steering wheel and the center point B of the upper fork is the axis of the steering column (1); Second Revolute joint: Create a second Revolute joint along the upper and lower adjustment axis P of the steering column, connect the adjustment bracket (12) to the vehicle body, and limit the bracket to rotate only around the upper and lower adjustment axis P of the steering column; Adjusting Angle Parameterization Driven: Creating a Second Angle Parameter Define upward adjustment as a positive angle and downward adjustment as a negative angle, and convert the angle value into a radian value through the displacement driving function; Drive association and simulation verification: The drive function after radian conversion is associated with the adjustment bracket (12) and the Revolute pair of the vehicle body. Different α values ​​are set, and the simulation is run to observe the flexibility of the column up and down adjustment and the stability of the steering wheel center point A position, and to verify the motion coordination of the steering system under different adjustment positions.

6. The method for calculating and evaluating the fluctuation of automotive steering ratio according to claim 5, characterized in that: The instantaneous steering ratio fluctuation curve is specifically as follows: Set the full steering range of the steering wheel and the frequency sweep drive range, select a fixed drive angle within the frequency sweep drive range, generate a steering drive signal, and use the steering drive signal to apply a steering angle drive to the steering wheel; After obtaining the output steering drive signal, the steering wheel angle is the steering wheel angle at the Revolute joint of the steering column (1) and the upper fork UJ1. The steering knuckle angle, i.e., the left front wheel steering angle, is collected at the Revolute joint between the steering knuckle and the lower control arm. Right front wheel steering angle ; Calculate the instantaneous steering gear ratio; By associating the instantaneous steering ratio with the corresponding steering wheel angle according to the steering sequence, an instantaneous steering ratio fluctuation curve is generated.

7. The method for calculating and evaluating the fluctuation of automotive steering ratio according to claim 6, characterized in that: The instantaneous steering ratio is obtained by calculating the average wheel angle and numerically differentiating the average steering wheel angle and the average wheel angle.

8. The method for calculating and evaluating the fluctuation of automotive steering ratio according to claim 7, characterized in that: The instantaneous steering gear ratio fluctuation curve is generated, specifically based on the steering wheel angle. The horizontal axis represents the instantaneous steering ratio. Using the vertical axis as the ordinate, a functional relationship is established to obtain the instantaneous steering transmission ratio fluctuation curve.

9. The method for calculating and evaluating the fluctuation of automotive steering ratio according to claim 8, characterized in that: The multi-dimensional assessment specifically refers to: Calculate the transmission ratio fluctuation ζ, peak offset angle θ, and fluctuation symmetry ε, and set corresponding evaluation thresholds for transmission ratio fluctuation ζ, peak offset angle θ, and fluctuation symmetry ε respectively. Then, determine whether to adjust the phase angle by evaluating the corresponding transmission ratio fluctuation ζ, peak offset angle θ, and fluctuation symmetry ε at the evaluation thresholds. If the transmission ratio fluctuation ζ, peak offset angle θ, and fluctuation symmetry ε do not meet the corresponding evaluation thresholds, it is determined that the phase angle needs to be adjusted.

10. The method for calculating and evaluating the fluctuation of automotive steering ratio according to claim 9, characterized in that: The transmission ratio fluctuation ζ, peak offset angle θ, and fluctuation symmetry ε are as follows: ； in, The peak value at the zero steering position on the instantaneous steering ratio fluctuation curve. The trough value adjacent to Peak1 at the zero turning position of the same fluctuation curve; The peak offset angle θ is as follows: ； in, The steering wheel angle corresponding to the instantaneous gear ratio reaching peak Peak1; and θ is positive when the peak is to the right of the zero steering position and negative when it is to the left; the symmetry of the fluctuation ε is as follows: ； in, Peak offset angle The absolute value, This is the angle-to-radian conversion factor. It is a sine function.

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