A vehicle dual front axle steering system optimization method

Abstract

The application provides a vehicle double-front-axle steering system optimization method, and belongs to the field of vehicle engineering and steering system control.The application proposes a successive optimization systematic method: firstly, the length of the first axle cross tie rod and the second axle cross tie rod is adjusted to realize trapezoidal symmetry optimization;then, the inclination of the first axle transition swing arm and / or the inclination of the second axle transition swing arm is adjusted to realize linkage symmetry optimization;finally, the inclination of the front connecting rod and / or the inclination of the intermediate connecting rod is adjusted to correct the equivalent transmission relationship from the first axle to the second axle, and realize transmission ratio optimization;through trapezoidal symmetry optimization, linkage symmetry optimization and transmission ratio optimization, the double-front-axle Ackerman can be optimized.Through the optimization process, the best effect of the double-front-axle Ackerman can be realized, the double-front-axle cooperative steering performance can be improved, the method is suitable for commercial vehicles equipped with a double-front-axle steering mechanism, and the abnormal wear of double-front-axle steering tires can be effectively reduced.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of vehicle engineering and steering system control, and particularly relates to a vehicle double front axle steering system optimization method. BACKGROUND

[0002] In recent years, with the increasing demand for heavy-duty vehicle maneuverability in the transportation industry and engineering field, double front axle steering systems are increasingly widely used in commercial vehicles. Through the coordinated steering action of the two front axles, i.e., the first front axle and the second front axle, the system significantly improves the low-speed turning performance and driving stability of the vehicle, optimizes the tire load distribution, and reduces the turning radius, theoretically reducing operating costs and tire wear. However, in actual application, due to insufficient Ackerman geometric matching accuracy or poor mechanical coordination, the system often has problems such as abnormal tire wear, vehicle deviation, and steering shimmy, which affect the full play of its performance advantages.

[0003] From the structural principle, the double front axle steering system is a steering solution specially designed for multi-axle heavy-duty vehicles. Among them, the design of the Ackerman steering angle is particularly critical. It makes the inside wheel steering angle greater than the outside wheel, so that the extended axes of the steering wheels intersect at the same instantaneous rotation center on the ground, thereby satisfying pure rolling to reduce tire slip. In this system, due to the coordinated motion of two groups of steering axles, the Ackerman geometric design is more complex, and the steering angles of each wheel must be accurately matched to effectively prevent tire interference and abnormal wear, and ultimately achieve the best balance between steering performance and mechanical efficiency. To achieve ideal Ackerman geometry, it is necessary to satisfy the coordinated steering relationship between the two front axles, such as steering synchronization between different front axles, Ackerman deviation control between left and right wheels, and spatial interference of steering link arrangement, steering arm length, and angle. The current steering optimization mostly focuses on single front axle design, while the optimization method for double front axle steering mechanism mostly splits the steering system into subsystems for analysis, and the steering angle relationship between left and right wheels is ensured by the axle steering trapezoidal mechanism to meet the Ackerman relationship. The motion coordination between axles is ensured by the rocker arm mechanism. In the multi-axle steering system, the main factor affecting the steering characteristics is the multi-rocker transmission mechanism, so the research focuses on the rocker arm mechanism, but existing research often simplifies the spatial link to a planar mechanism for single-objective optimization. These simplifications reduce the calculation difficulty, but result in a large deviation from the actual situation.

[0004] Currently, the optimization method for double front axle structure is often based on empirical parameter adjustment, which requires higher experience for design and development personnel, and lacks systematic modeling and decoupled optimization process methods, resulting in a large Ackerman error under typical working conditions, which in turn causes tire side slip, steering lag, mechanical interference, and other problems, seriously affecting vehicle performance and safety. SUMMARY

[0005] In order to solve the problems of complex optimization process, difficult collaborative control and poor parameter adaptability of the double front axle steering system of a commercial vehicle in Ackerman steering performance optimization, the application provides a vehicle double front axle steering system optimization method.

[0006] In order to achieve the above-mentioned purpose, the application provides the following technical scheme:

[0007] A vehicle double front axle steering system optimization method, the double front axle steering system has a front axle, a front axle cross tie rod, a front axle transition swing arm, a second axle, a second axle cross tie rod, a second axle transition swing arm, a front connecting rod and an intermediate connecting rod; the method comprises the following steps:

[0008] Taking the inner wheel of the front axle and the inner wheel of the second axle as reference wheels, the Ackerman errors of the outer wheels of the front axle and the second axle are calculated, the lengths of the front axle cross tie rod and the second axle cross tie rod are adjusted to minimize the Ackerman errors of the outer wheels of the front axle and the second axle, and the trapezoidal symmetry optimization is realized;

[0009] Taking the inner wheel of the front axle as a reference wheel, the Ackerman errors of the left wheel of the second axle under the conditions of left turning and right turning of the reference wheel are calculated, the inclination angle of the front axle transition swing arm and / or the inclination angle of the second axle transition swing arm are adjusted to make the absolute values of the Ackerman errors of the left wheel of the second axle under the conditions of left turning and right turning of the reference wheel by the same angle be equal and the signs be opposite, and the linkage symmetry optimization is realized;

[0010] Taking the inner wheel of the front axle as a reference wheel, the Ackerman errors of the left wheel of the second axle under the conditions of left turning and right turning of the reference wheel are calculated, the inclination angle of the front connecting rod and / or the inclination angle of the intermediate connecting rod are adjusted to make the Ackerman errors of the left wheel of the second axle under the conditions of left turning and right turning of the reference wheel by the same angle be controlled within a predetermined threshold range, and the transmission ratio optimization is realized;

[0011] Through the trapezoidal symmetry optimization, the linkage symmetry optimization and the transmission ratio optimization, the Ackerman of the double front axle steering is optimized.

[0012] Preferably, the double front axle steering system further has two front axle trapezoidal arms and two second axle trapezoidal arms, and the lengths of the front axle cross tie rod and the second axle cross tie rod are adjusted by adjusting the distances between the hard points on the two front axle trapezoidal arms and the distances between the hard points on the two second axle trapezoidal arms, respectively, and the lengths of the front axle cross tie rod and the second axle cross tie rod are corrected through the adjustment of the hard point distances.

[0013] Preferably, the length of the front axle transverse link and the rear axle transverse link is adjusted, specifically including: if the Ackerman error of the right wheel of the front axle is positive when the left wheel of the front axle turns to a set angle, it indicates that the actual turning angle of the right wheel of the front axle is smaller than the target value, and the right wheel of the front axle does not turn to the ideal Ackerman turning angle position, so that the distance between the two hard points on the front axle trapezoidal arm in the width direction of the vehicle body is increased, and the length of the front axle transverse link is increased; on the contrary, the distance between the two hard points on the front axle trapezoidal arm in the width direction of the vehicle body is reduced, and the length of the front axle transverse link is reduced, so that the turning angle of the right wheel of the front axle reaches the ideal position; the same checking method is used for the rear axle, and the distance between the two hard points on the rear axle trapezoidal arm in the width direction of the vehicle body is adjusted, so that the turning angle of the right wheel of the rear axle reaches the ideal position.

[0014] Preferably, the inclination angle of the front axle transition swing arm and / or the inclination angle of the rear axle transition swing arm is adjusted, specifically including: the position of the hard point on the front axle transition swing arm and / or the rear axle transition swing arm in the length direction of the vehicle body is adjusted, and the optimal parameter combination of the positions of the hard points is found to change the inclination angle of the front axle transition swing arm and / or the inclination angle of the rear axle transition swing arm.

[0015] Preferably, the front of the vehicle is set as the head direction, the rear of the vehicle is set as the tail direction, the left side of the driver's seat is set as the left side, and the right side of the co-pilot is set as the right side, wherein the front-rear direction of the vehicle body is the longitudinal direction of the vehicle, the left-right direction of the vehicle body is the transverse direction of the vehicle, and the height direction of the vehicle body is the direction perpendicular to the ground, and the linkage symmetry optimization method specifically includes:

[0016] Error sign difference: when the left wheel of the front axle turns to a set angle, the Ackerman error of the left wheel of the rear axle is one positive and one negative, if the absolute value of the negative error is greater than the absolute value of the positive error, the front axle transition swing arm and / or the rear axle transition swing arm is inclined backward, at least one of the upper end hard point of the front axle transition swing arm, the lower end hard point of the front axle transition swing arm, the upper end hard point of the rear axle transition swing arm, and the lower end hard point of the rear axle transition swing arm or any combination thereof is moved backward, and the turning angle of the left wheel of the rear axle is corrected to the right to reduce the difference between the positive and negative errors; if the absolute value of the positive error is greater than the absolute value of the negative error, the front axle transition swing arm and / or the rear axle transition swing arm is inclined forward, at least one of the upper end hard point of the front axle transition swing arm, the lower end hard point of the front axle transition swing arm, the upper end hard point of the rear axle transition swing arm, and the lower end hard point of the rear axle transition swing arm or any combination thereof is moved forward, and the turning angle of the left wheel of the rear axle is corrected to the left to reduce the difference between the positive and negative errors;

[0017] When the left turning and right turning set angles of the reference wheel of the first axle are the same, the Ackerman errors of the left wheel of the second axle are positive, the transition swing arm of the first axle and / or the transition swing arm of the second axle are inclined forward, at least one of the upper end hard point of the transition swing arm of the first axle, the lower end hard point of the transition swing arm of the first axle, the upper end hard point of the transition swing arm of the second axle and the lower end hard point of the transition swing arm of the second axle or any combination thereof is moved forward, the left turning angle of the left wheel of the second axle is corrected to the left to tend to the ideal position, and when the Ackerman errors of the left wheel of the second axle are negative, the transition swing arm of the first axle and / or the transition swing arm of the second axle are inclined backward, at least one of the upper end hard point of the transition swing arm of the first axle, the lower end hard point of the transition swing arm of the first axle, the upper end hard point of the transition swing arm of the second axle and the lower end hard point of the transition swing arm of the second axle or any combination thereof is moved backward, the left turning angle of the left wheel of the second axle is corrected to the right to tend to the ideal position.

[0018] Preferably, the double front axle steering system also has a steering gear assembly, and the transmission ratio optimization specifically adjusts the positions of at least one of the upper end hard point of the output swing arm of the steering gear assembly, the upper end hard point of the transition swing arm of the first axle and the upper end hard point of the transition swing arm of the second axle or any combination thereof in the height direction of the vehicle body, finds the optimal parameter combination of the positions of the hard points, changes the inclination angle of the front connecting rod and / or the inclination angle of the intermediate connecting rod, corrects the equivalent transmission relationship from the first axle to the second axle, and realizes the transmission ratio optimization.

[0019] Preferably, the transmission ratio optimization mode specifically includes the following steps:

[0020] After the linkage symmetry optimization is completed, when the left turning and right turning set angles of the reference wheel of the first axle are the same, the Ackerman errors of the left wheel of the second axle are positive and negative; if the left turning Ackerman error is negative and the right turning Ackerman error is positive, one of the following adjustment modes or any combination thereof is adopted: the upper end hard point of the output swing arm of the steering gear assembly is adjusted upward in the height direction of the vehicle body, the upper end hard point of the transition swing arm of the first axle is adjusted upward in the height direction of the vehicle body, and the upper end hard point of the transition swing arm of the second axle is adjusted downward in the height direction of the vehicle body; if the left turning Ackerman error is positive and the right turning Ackerman error is negative, one of the following adjustment modes or any combination thereof is adopted: the upper end hard point of the output swing arm of the steering gear assembly is adjusted downward in the height direction of the vehicle body, the upper end hard point of the transition swing arm of the first axle is adjusted downward in the height direction of the vehicle body, and the upper end hard point of the transition swing arm of the second axle is adjusted upward in the height direction of the vehicle body, to achieve the ideal transmission ratio.

[0021] The vehicle double front axle steering system optimization method provided by the application has the following beneficial effects:

[0022] This method employs a phased, progressive optimization strategy: first, trapezoidal symmetry optimization is performed, followed by linkage symmetry optimization, and finally, transmission ratio optimization, ultimately achieving overall optimization of the steering system. Each optimization step is independent, and subsequent adjustments do not interfere with the results of previous steps, thus achieving decoupling of the optimization process. This ensures optimal matching of the Ackermann characteristics of the dual front axles. The method is simple and efficient, systematically solving the coordination and matching problems of key parameters in the dual front axle steering mechanism, while effectively considering multiple performance indicators such as steering geometry accuracy and tire wear control. It achieves optimal collaborative optimization without the need for complex multi-objective coupled models. Compared to traditional optimization methods based on empirical parameter adjustments and relying on complex multi-objective coupled models, this method has a systematic optimization process and achieves collaborative optimization of the steering system without the need for complex models. It can significantly reduce abnormal tire wear and improve the overall performance of the dual front axle steering system. Attached Figure Description

[0023] To more clearly illustrate the embodiments and design schemes of the present invention, the accompanying drawings required for this embodiment will be briefly described below. The drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 A flowchart of the vehicle dual front axle steering system optimization method provided by the present invention;

[0025] Figure 2 This is a schematic diagram of the dual front axle model and hard point locations mentioned in the steps of the embodiments of the present invention;

[0026] Figure 3 This is a comparative diagram showing the adjustment effects of linkage symmetry optimization (error sign difference and larger absolute value of negative error); among which, Figure 3 (a) is a comparison chart showing the adjustment effect when the absolute value of the negative error is larger during the right turn condition. Figure 3 (b) is a comparison chart of the adjustment effect when the absolute value of the negative error is larger during the left turn condition;

[0027] Figure 4 This is a comparative diagram showing the adjustment effects of linkage symmetry optimization (error sign difference and larger absolute value of positive error); among which, Figure 4 (a) is a comparison chart showing the adjustment effect when the absolute value of the positive error is larger during the left turn condition. Figure 4 (b) is a comparison chart of the adjustment effect when the absolute value of the positive error is larger during the right turn condition;

[0028] Figure 5 This is a schematic diagram illustrating the adjustment direction for linkage symmetry optimization (errors with the same sign); among which, Figure 5(a) is the adjustment direction schematic diagram of the Ackerman error when the adjustment direction of (a) is positive, Figure 5 (b) is the adjustment direction schematic diagram of the Ackerman error when the adjustment direction of (a) is negative;

[0029] Figure 6 is the adjustment direction schematic diagram of the transmission ratio optimization (error sign difference), wherein, Figure 6 (a) is the adjustment direction schematic diagram of the Ackerman error when the adjustment direction of (a) is negative, Figure 6 (b) is the adjustment direction schematic diagram of the Ackerman error when the adjustment direction of (a) is negative.

[0030] BRIEF DESCRIPTION OF DRAWINGS

[0031] 1-direction machine assembly, 2-front connecting rod, 3-intermediate connecting rod, 4-steering straight pull rod, 5-first axle, 6-first axle transverse pull rod, 7-first axle transition swing arm, 8-first axle steering knuckle, 9-first axle trapezoidal arm, 10-second axle, 11-second axle transverse pull rod, 12-second axle transition swing arm, 13-second axle steering knuckle, 14-second axle trapezoidal arm. DETAILED DESCRIPTION

[0032] In order for those skilled in the art to better understand the technical solutions of the present application and to implement them, the present application will be described in detail below in conjunction with the drawings and specific embodiments. The following embodiments are only used to more clearly illustrate the technical solutions of the present application, and cannot be used to limit the protection scope of the present application.

[0033] In view of the problems of large Ackerman error, abnormal tire wear, poor steering coordination and complicated optimization process existing in the existing double front axle steering system, the present application proposes a vehicle double front axle steering system optimization method, which is suitable for steering system optimization and error control of commercial vehicle double front axle structure. Specifically, a method for commercial vehicle double front axle steering structure is provided, which can effectively analyze and optimize the Ackerman error, so as to reduce tire wear, improve vehicle steering performance, reduce design cost and shorten development cycle.

[0034] As shown in Figure 2 The double front axle steering system in the present application has a direction machine assembly 1, a front connecting rod 2, an intermediate connecting rod 3, a steering straight pull rod 4, a first axle 5, a first axle transverse pull rod 6, a first axle transition swing arm 7, two first axle steering knuckles 8, two first axle trapezoidal arms 9, a second axle 10, a second axle transverse pull rod 11, a second axle transition swing arm 12, two second axle steering knuckles 13, and two second axle trapezoidal arms 14. Among them, the direction machine assembly 1 and the first axle 5 are located in the direction of the vehicle head, and the second axle 10 is located in the direction of the vehicle tail. The two ends of the first axle 5 are connected with the two first axle steering knuckles 8 respectively, and the two ends of the second axle 10 are connected with the two second axle steering knuckles 13 respectively. The two first axle trapezoidal arms 9 are connected with the two first axle steering knuckles 8 respectively, and the two second axle trapezoidal arms 14 are connected with the two second axle steering knuckles 13 respectively.

[0035] The upper end of the output rocker arm of the steering gear assembly 1 has a hard point A hinged with one end of the front connecting rod 2, the upper end of the one-bridge transition swing arm 7 has a hard point B hinged with one end of the intermediate connecting rod 3, the lower end of the one-bridge transition swing arm 7 has a hard point C hinged with the other end of the front connecting rod 2, the upper end of the two-bridge transition swing arm 12 has a hard point D hinged with the other end of the intermediate connecting rod 3, the lower end of the two-bridge transition swing arm 12 has a hard point E hinged with one end of the steering straight pull rod 4, and the other end of the steering straight pull rod 4 is connected with one of the two-bridge steering knuckles 13. The two one-bridge trapezoidal arms 9 respectively have a hard point F and a hard point G hinged with the two ends of the one-bridge cross pull rod 6, and the two two-bridge trapezoidal arms 14 respectively have a hard point H and a hard point I hinged with the two ends of the two-bridge cross pull rod 11.

[0036] Definition: Ackerman error = actual wheel angle - ideal Ackerman angle corresponding to the wheel, when the wheel turns right, the angle is positive, and when the wheel turns left, the angle is negative. When the actual angle of a wheel under a given working condition minus the ideal Ackerman angle corresponding to the wheel is greater than 0, it is considered that the Ackerman error of the wheel is positive; when the difference is less than 0, it is considered that the Ackerman error of the wheel is negative.

[0037] At the same time, the front direction of the vehicle head is designated as the front side, and the rear direction of the vehicle tail is designated as the rear side, and when the vehicle is in a stationary state on a horizontal road surface, the coordinate system is defined as: taking the mass center position of the whole vehicle as the coordinate origin O, the x-axis is parallel to the ground and points to the rear direction of the vehicle tail (the length direction of the vehicle body), the z-axis passes through the mass center and points to the upper direction (the height direction of the vehicle body), and the y-axis is parallel to the ground and points to the right side of the cab (the width direction of the vehicle body).

[0038] In the present application, the inner wheel and the outer wheel respectively refer to the steering wheels located on the inside and outside of the turning when the vehicle turns. In a double front axle vehicle, they are respectively called one-bridge inner wheel, one-bridge outer wheel, two-bridge inner wheel and two-bridge outer wheel according to the types of the axles.

[0039] For example: when turning left, the left one-bridge wheel is a one-bridge inner wheel, and the right one-bridge wheel is a one-bridge outer wheel; and when turning right, it is the opposite.

[0040] As shown in Figure 1 The implementation of the vehicle double front axle steering system optimization method provided by the present application includes the following steps:

[0041] Step 1: Taking the one-bridge inner wheel and the two-bridge inner wheel as the reference wheels respectively, when the respective inner wheels are in a typical angle working condition (for example, the inner wheel turns left by 30°), the Ackerman errors of the one-bridge outer wheel and the two-bridge outer wheel are calculated, the lengths of the one-bridge cross pull rod and the two-bridge cross pull rod are adjusted, the Ackerman errors of the one-bridge outer wheel and the two-bridge outer wheel are analyzed and optimized, and the Ackerman errors are minimized to realize the optimization of trapezoidal symmetry.

[0042] The specific optimization method is to adjust the distance between the hard points on the two one-bridge trapezoidal arms 9 and the distance between the hard points on the two two-bridge trapezoidal arms 14, respectively, and correct the length of the one-bridge cross pull rod and the two-bridge cross pull rod by adjusting the distance between the hard points. The hard point positions of the two one-bridge trapezoidal arms 9 are shown in F and G in the attached Figure 2 The hard point positions of the two two-bridge trapezoidal arms 14 are shown in H and I in the attached Figure 2 By symmetrically adjusting the distance between the hard points F and G and the distance between the hard points H and I, the length of the one-bridge cross pull rod and the two-bridge cross pull rod is increased or decreased. When the trapezoidal symmetry is optimized, it should be ensured that the positions of the four hard points F, G, H, and I have been independently optimized.

[0043] Step 2: Take the one-bridge inner wheel as the reference wheel, calculate the Ackerman error of the two-bridge left wheel under the conditions of the reference wheel turning left and right, and analyze and optimize the Ackerman error of the two-bridge left wheel under the conditions of the reference wheel turning left and right by adjusting the inclination angle of the one-bridge transition swing arm or the inclination angle of the two-bridge transition swing arm, or simultaneously adjusting the inclination angle of the one-bridge transition swing arm and the two-bridge transition swing arm, so that the Ackerman error of the two-bridge left wheel under the conditions of the reference wheel turning left and right is symmetrically distributed in value, i.e., the absolute values are equal and the signs are opposite, to realize linkage symmetry optimization.

[0044] The specific optimization method is to adjust the distance between the hard points on the two one-bridge trapezoidal arms 9 and the distance between the hard points on the two two-bridge trapezoidal arms 14, respectively, and correct the length of the one-bridge cross pull rod and the two-bridge cross pull rod by adjusting the distance between the hard points. The hard point positions of the two one-bridge trapezoidal arms 9 are shown in F and G in the attached Figure 2 The hard point positions of the two two-bridge trapezoidal arms 14 are shown in H and I in the attached Figure 2 D and E in the attached

[0045] Step 3: After completing the linkage symmetry optimization, take the one-bridge inner wheel as the reference wheel, calculate the Ackerman error of the two-bridge left wheel under the conditions of the reference wheel turning left and right, and analyze the Ackerman error of the two-bridge left wheel under the two conditions by adjusting the inclination angle of the front connecting rod or the inclination angle of the intermediate connecting rod, or simultaneously adjusting the inclination angle of the front connecting rod and the intermediate connecting rod, so that the Ackerman error of the two-bridge left wheel under the above two conditions is controlled within a predetermined threshold, and the optimal value is close to 0, to realize transmission ratio optimization.

[0046] The specific optimization mode is adjusting the position of at least one of the hard points A of the output rocker arm of the direction machine assembly 1, the hard point B of the first bridge transition swing arm 7, and the hard point D of the second bridge transition swing arm 12 or any combination thereof in the Z direction, finding the optimal parameter combination of the positions of the hard points, and then changing the inclination angle of the front connecting rod or the inclination angle of the intermediate connecting rod or simultaneously changing the inclination angles of the front connecting rod and the intermediate connecting rod to correct the equivalent transmission relationship from the first bridge to the second bridge and realize transmission ratio optimization. The transmission ratio of the linkage mechanism is changed by adjusting the position of at least one of the hard points A, B, and D in the Z direction, and the positions of the hard points A, B, and D are as shown in FIG. 8. It should be noted that when the transmission ratio is optimized, the position of the hard point A is adjusted to adjust the inclination angle of the front connecting rod, and the position of the rear end of the front connecting rod remains unchanged, that is, the position of the hard point C remains unchanged. Figure 2

[0047] It should be noted that in the embodiment, the trapezoidal symmetry optimization of step 1 is based on the independent checking of the Ackerman errors of the first bridge and the second bridge, that is, the Ackerman error of the second bridge does not consider the linkage influence of the first bridge and the second bridge.

[0048] The present application first performs trapezoidal symmetry optimization, then performs linkage symmetry optimization, and finally performs transmission ratio optimization, so that the double front bridge Ackerman is optimized through the process. According to the above process, the double front bridge Ackerman can be optimized, and the steering geometry precision can be effectively considered, the comprehensive performance of the double front bridge steering system is improved, and the method is simple and efficient, which can effectively reduce the abnormal wear of the double front bridge steering tire. Embodiment

[0049] The following describes the implementation process of the vehicle double front bridge steering system optimization method provided by the present application by taking a certain double front bridge commercial vehicle as an example.

[0050] In this embodiment, the structure dynamics simulation software is used to optimize the 30° Ackerman error of the first bridge of a certain commercial vehicle, that is, to investigate the Ackerman errors of the remaining wheels when the inner wheel of the first bridge turns 30°, and to define that the turning angle direction is positive when the wheels turn right and negative when the wheels turn left, and the Ackerman error = actual wheel turning angle - ideal Ackerman turning angle corresponding to the wheel.

[0051] First, trapezoidal symmetry optimization is performed.

[0052] Since the steering trapezoid of the double front bridge has symmetry, only one side steering condition checking is required, and in this embodiment, only the Ackerman error of the right wheel when turning left is checked: the structure dynamics simulation software is used to automatically calculate the Ackerman error of the right wheel of the first bridge under the typical condition of the left wheel of the first bridge turning 30°.

[0053] ​If the Ackerman error of the right wheel of the first axle is positive, it indicates that the actual rotation angle of the right wheel of the first axle is smaller than the ideal Ackerman rotation angle corresponding to the wheel, and the length of the first axle transverse rod 6 needs to be appropriately increased to increase the distance between the hard points F and G in the Y direction. Conversely, the length of the first axle transverse rod 6 needs to be appropriately shortened to decrease the distance between the hard points F and G in the Y direction, so that the actual rotation angle of the right wheel of the first axle approaches the ideal Ackerman rotation angle corresponding to the wheel. Here, the calculation is for the left turning condition of the left wheel of the first axle. For example, at this time, the actual rotation angle of the right wheel of the first axle is -1°, the ideal rotation angle is -2°, the actual rotation angle is smaller than the ideal rotation angle, and the Ackerman error = (-1) - (-2) = 1, which is positive.

[0054] If the right wheel of the first axle turns right, for example, the actual rotation angle of the right wheel of the first axle is 1°, the ideal rotation angle is 2°, the actual rotation angle is smaller than the ideal rotation angle, and the Ackerman error = 1 - 2 = -1, which is negative.

[0055] The same checking method is used for the second axle. Taking the left turning of the inner wheel of the second axle by 30° as an example, during the optimization of the trapezoidal symmetry of the second axle, the coordinates of the hard points H and I in the Y direction are synchronously adjusted in pairs while ensuring the symmetry of the hard points H and I about the XOZ plane of the longitudinal center plane of the vehicle (i.e. Figure 2 For example, the Y coordinates of the hard points H and I can be simultaneously increased by 2 mm or simultaneously decreased by 1 mm, that is, the distance between the hard points H and I is increased by 4 mm or decreased by 2 mm, and the length of the second axle transverse rod 11 is increased or decreased accordingly, to construct a plurality of candidate parameter combinations including the Y coordinates of the hard points H and I. The actual rotation angle of the outer wheel of the second axle under each parameter combination is calculated based on the structural dynamics simulation software, and compared with the corresponding ideal Ackerman rotation angle, and the parameter combination that minimizes the Ackerman error of the outer wheel of the second axle and satisfies the symmetry constraint is selected as the optimization result of the trapezoidal symmetry of the second axle. For example, when the inner wheel of the second axle turns left by 30°, if the Ackerman error of the outer wheel of the second axle is close to 0, it can be considered that the actual rotation angle of the outer wheel of the second axle is basically the same as the ideal Ackerman rotation angle, and the Ackerman trapezoidal of the second axle reaches the ideal Ackerman rotation angle position corresponding to the wheel under this working condition.

[0056] Subsequently, linkage symmetry optimization and transmission ratio optimization are performed, both taking the inner wheel of the first axle as a reference to check the Ackerman error of the left wheel of the second axle when turning left and right.

[0057] The linkage symmetry optimization is as follows:

[0058] (1) Error sign: When the reference wheel of the first axle turns left and right by 30°, the Ackerman error signs of the left wheel of the second axle in the two working conditions are opposite, that is, the Ackerman error is positive in one working condition, and the Ackerman error is negative in the other working condition. If the absolute value of the negative error is larger, it indicates that the left wheel of the second axle is overall left in the two steering conditions, and the transition swing arm 7 of the first axle or the transition swing arm 12 of the second axle should be inclined backward, or the transition swing arm 7 of the first axle and the transition swing arm 12 of the second axle can be inclined backward at the same time, so that at least one of the hard points B, C, D and E or any combination thereof is moved backward along the vehicle longitudinal direction X, and the turning angle of the left wheel of the second axle is corrected to the right to reduce the positive and negative errors, so as to realize error adjustment, as shown in (a) and (b) of FIG. 13. Figure 3 (a) and (b) of FIG. 13. Figure 3 If the absolute value of the positive error is larger, it indicates that the left wheel of the second axle is overall right in the two steering conditions, and the transition swing arm 7 of the first axle or the transition swing arm 12 of the second axle should be inclined forward, or the transition swing arm 7 of the first axle and the transition swing arm 12 of the second axle can be inclined forward at the same time, so that at least one of the hard points B, C, D and E or any combination thereof is moved forward along the X direction, and the turning angle of the left wheel of the second axle is corrected to the left to reduce the positive and negative error difference, so as to realize error adjustment, as shown in (a) and (b) of FIG. 13. Figure 4 (a) and (b) of FIG. 13. Figure 4 The above optimization goal is to make the absolute values of the left and right turning Ackerman errors equal and the signs opposite.

[0059] (2) Error sign: When the reference wheel of the first axle turns left and right by 30°, the Ackerman error signs of the left wheel of the second axle in the two working conditions are opposite, that is, the Ackerman error is positive in one working condition, and the Ackerman error is negative in the other working condition. If the absolute value of the negative error is larger, it indicates that the left wheel of the second axle is overall left in the two steering conditions, and the transition swing arm 7 of the first axle or the transition swing arm 12 of the second axle should be inclined backward, or the transition swing arm 7 of the first axle and the transition swing arm 12 of the second axle can be inclined backward at the same time, so that at least one of the hard points B, C, D and E or any combination thereof is moved backward along the vehicle longitudinal direction X, and the turning angle of the left wheel of the second axle is corrected to the right to reduce the positive and negative errors, so as to realize error adjustment, as shown in (a) and (b) of FIG. 13. Figure 5 (a) and (b) of FIG. 13. Figure 5 If the absolute value of the positive error is larger, it indicates that the left wheel of the second axle is overall right in the two steering conditions, and the transition swing arm 7 of the first axle or the transition swing arm 12 of the second axle should be inclined forward, or the transition swing arm 7 of the first axle and the transition swing arm 12 of the second axle can be inclined forward at the same time, so that at least one of the hard points B, C, D and E or any combination thereof is moved forward along the X direction, and the turning angle of the left wheel of the second axle is corrected to the left to reduce the positive and negative error difference, so as to realize error adjustment, as shown in (a) and (b) of FIG. 13. (a) and (b) of FIG. 13.

[0060] The transmission ratio optimization is as follows:

[0061] After the linkage symmetry optimization is completed, when the left and right reference wheels of the first axle turn 30°, the Ackerman error of the left wheel of the second axle is positive and negative. If the left turn is negative and the right turn is positive, it indicates that the actual turning angles of the left and right wheels of the second axle are both larger than the theoretical values, and the transition swing arm transmission ratio needs to be reduced, so that at least one of the hard points A, B and D or any combination thereof is adjusted along the Z direction, wherein the hard points A and B are moved along the Z direction, and the hard point D is moved downward along the Z direction, to achieve the effect shown in (a) of FIG. 6. Figure 6 If the left turn is positive and the right turn is negative, it indicates that the actual turning angles of the left and right wheels of the second axle are both smaller than the theoretical values, and the transition swing arm transmission ratio needs to be increased, so that at least one of the hard points A, B and D or any combination thereof is adjusted along the Z direction, wherein the hard points A and B are moved downward along the Z direction, and the hard point D is moved upward along the Z direction, to achieve the effect shown in (b) of FIG. 6. Figure 6

[0062] The vehicle double-front-axle steering system optimization method provided by the present application adopts a staged progressive optimization strategy, first performs trapezoidal symmetry optimization, then performs linkage symmetry optimization, and finally performs transmission ratio optimization. Through this optimization process, the coordinated matching of various key parameters in the double-front-axle steering mechanism can be systematically solved, and the collaborative optimization effect can be achieved without establishing a complex multi-objective coupling model. Compared with the traditional optimization method based on empirical parameter adjustment and relying on a complex multi-objective coupling model, the present application has a systematic optimization process, the optimization steps are independent of each other, subsequent adjustments will not interfere with the results of the previous step, the optimization process can be decoupled, and the optimal matching of the double-front-axle Ackerman characteristics can be achieved without establishing a complex model, which is simple and efficient, can effectively balance multiple performance indicators such as steering geometric accuracy and tire wear control, significantly improves the comprehensive performance of the double-front-axle steering system, and is suitable for commercial vehicles such as heavy-duty tractors, engineering vehicles and cargo vehicles. The present application has the characteristics of simple engineering implementation and significant optimization effect. The problems of complex optimization process, large Ackerman error, abnormal tire wear and high requirement for developer experience of the existing double-front-axle steering system are solved.

[0063] It should be noted that the above specific embodiments can enable those skilled in the art to more fully understand the present application, but in no way limit the present application. Therefore, although the present application has been described in detail in the specification and examples, those skilled in the art should understand that modifications or equivalent replacements can still be made to the present application; and all technical solutions and improvements that do not deviate from the spirit and scope of the present application are covered by the protection scope of the present application. Any reference signs in the claims should not be considered as limiting the claims. Any simple changes or equivalent replacements of the technical solutions within the scope of the present disclosure can be obvious to those skilled in the art, and are within the protection scope of the present application.​

Claims

1. A method for optimizing a vehicle dual front axle steering system, the method comprising: The double front axle steering system has a front axle, a front axle cross tie rod, a front axle transition swing arm, a rear axle, a rear axle cross tie rod, a rear axle transition swing arm, a front connecting rod and a middle connecting rod. The method comprises the following steps: The Ackerman errors of the outer wheels of the front axle and the rear axle are calculated respectively based on the inner wheels of the front axle and the rear axle as reference wheels, the Ackerman errors of the outer wheels of the front axle and the rear axle are minimized by adjusting the lengths of the front axle cross tie rod and the rear axle cross tie rod, and the trapezoidal symmetry optimization is realized. The Ackerman errors of the left wheel of the rear axle under the conditions of left turning and right turning of the reference wheel are calculated based on the inner wheel of the front axle as the reference wheel, the Ackerman errors of the left wheel of the rear axle under the conditions of left turning and right turning of the reference wheel by the same angle are made equal in absolute value and opposite in sign by adjusting the inclination of the front axle transition swing arm and / or the inclination of the rear axle transition swing arm, and the linkage symmetry optimization is realized. The Ackerman errors of the left wheel of the rear axle under the conditions of left turning and right turning of the reference wheel are calculated based on the inner wheel of the front axle as the reference wheel, the Ackerman errors of the left wheel of the rear axle under the conditions of left turning and right turning of the reference wheel by the same angle are controlled within a predetermined threshold range by adjusting the inclination of the front connecting rod and / or the inclination of the middle connecting rod, and the transmission ratio optimization is realized. The double front axle steering Ackerman is optimized through the trapezoidal symmetry optimization, the linkage symmetry optimization and the transmission ratio optimization. The double front axle steering system also has two front axle trapezoidal arms and two rear axle trapezoidal arms, and the lengths of the front axle cross tie rod and the rear axle cross tie rod are adjusted by adjusting the distances between the hard points on the two front axle trapezoidal arms and the distances between the hard points on the two rear axle trapezoidal arms.

2. The vehicle dual front axle steering system optimization method of claim 1, wherein, The lengths of the front axle cross tie rod and the rear axle cross tie rod are adjusted by increasing the distance between the two hard points on the front axle trapezoidal arm in the vehicle width direction and increasing the length of the front axle cross tie rod if the Ackerman error of the right wheel of the front axle is positive when the left wheel of the front axle turns left to a set angle, and vice versa.

3. The vehicle dual front axle steering system optimization method of claim 2, wherein, The inclination of the front axle transition swing arm and / or the inclination of the rear axle transition swing arm is adjusted by adjusting the positions of the hard points on the front axle transition swing arm and / or the rear axle transition swing arm in the length direction of the vehicle body to find the optimal parameter combination of the positions of the hard points and change the inclinations of the front axle transition swing arm and / or the rear axle transition swing arm. The vehicle head direction is set as front, the vehicle tail direction is set as rear, the driver's seat side is set as left, and the co-pilot's seat side is set as right, wherein the vehicle body front-rear direction is the vehicle longitudinal direction, the vehicle body left-right direction is the vehicle transverse direction, and the vehicle body height direction is the direction perpendicular to the ground. The linkage symmetry optimization method is as follows: Error sign difference: when the left and right turning angles of the reference wheel of the first axle are set, the Ackerman error of the left wheel of the second axle is positive and negative, if the absolute value of the negative error is greater than that of the positive error, the rear end of the transition swing arm of the first axle and / or the transition swing arm of the second axle is inclined, at least one of the upper end hard point of the transition swing arm of the first axle, the lower end hard point of the transition swing arm of the first axle, the upper end hard point of the transition swing arm of the second axle, the lower end hard point of the transition swing arm of the second axle or any combination thereof is moved backward, and the turning angle of the left wheel of the second axle is corrected to the right to reduce the difference between the positive and negative errors; if the absolute value of the positive error is greater than that of the negative error, the front end of the transition swing arm of the first axle and / or the transition swing arm of the second axle is inclined, at least one of the upper end hard point of the transition swing arm of the first axle, the lower end hard point of the transition swing arm of the first axle, the upper end hard point of the transition swing arm of the second axle, the lower end hard point of the transition swing arm of the second axle or any combination thereof is moved forward, and the turning angle of the left wheel of the second axle is corrected to the left to reduce the difference between the positive and negative errors. Error sign difference: when the left and right turning angles of the reference wheel of the first axle are set, the Ackerman error of the left wheel of the second axle is positive and negative, if the absolute value of the negative error is greater than that of the positive error, the rear end of the transition swing arm of the first axle and / or the transition swing arm of the second axle is inclined, at least one of the upper end hard point of the transition swing arm of the first axle, the lower end hard point of the transition swing arm of the first axle, the upper end hard point of the transition swing arm of the second axle, the lower end hard point of the transition swing arm of the second axle or any combination thereof is moved backward, and the turning angle of the left wheel of the second axle is corrected to the right to reduce the difference between the positive and negative errors; if the absolute value of the positive error is greater than that of the negative error, the front end of the transition swing arm of the first axle and / or the transition swing arm of the second axle is inclined, at least one of the upper end hard point of the transition swing arm of the first axle, the lower end hard point of the transition swing arm of the first axle, the upper end hard point of the transition swing arm of the second axle, the lower end hard point of the transition swing arm of the second axle or any combination thereof is moved forward, and the turning angle of the left wheel of the second axle is corrected to the left to reduce the difference between the positive and negative errors.

4. The vehicle dual front axle steering system optimization method of claim 3, wherein, The transmission ratio optimization mode is specifically:

5. The vehicle dual front axle steering system optimization method of claim 4, wherein, After completing the linkage symmetry optimization, the Ackerman error of the left wheel of the second axle is positive and negative when the left and right turning angles of the reference wheel of the first axle are set; if the Ackerman error of the left turning is negative and the Ackerman error of the right turning is positive, one of the following adjustment methods or any combination thereof is adopted: the upper end hard point of the output rocker arm of the steering gear assembly is adjusted upward along the vehicle body height, the upper end hard point of the transition swing arm of the first axle is adjusted upward along the vehicle body height, and the upper end hard point of the transition swing arm of the second axle is adjusted downward along the vehicle body height; if the Ackerman error of the left turning is positive and the Ackerman error of the right turning is negative, one of the following adjustment methods or any combination thereof is adopted: the upper end hard point of the output rocker arm of the steering gear assembly is adjusted downward along the vehicle body height, the upper end hard point of the transition swing arm of the first axle is adjusted downward along the vehicle body height, and the upper end hard point of the transition swing arm of the second axle is adjusted upward along the vehicle body height, to achieve the ideal transmission ratio. ​

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