Adjusting mechanism and active control method for caster angle of a mcfarland suspension steering wheel kingpin

Abstract

This invention relates to an adjustment mechanism and active control method for the kingpin inclination angle of a MacPherson strut suspension, belonging to the field of vehicle technology. The adjustment mechanism includes a MacPherson strut suspension and one or more adjustment mechanisms; the adjustment mechanism includes a support, an adjustment motor, a gear and rack mechanism, and a guide mechanism, realizing the active control adjustment of the kingpin inclination angle of the MacPherson strut suspension. The active control operation steps are as follows: (1) establish a wheel return torque calculation model, (2) establish a steering wheel return resistance torque calculation model, (3) establish an active control calculation formula for the kingpin inclination angle during vehicle driving; according to the calculation result of step (3), control the rotation direction and angle of the adjustment motor in the adjustment mechanism, and drive the adjustment bracket to perform horizontal displacement adjustment through the gear and rack mechanism to realize the active adjustment of the kingpin inclination angle α. This invention reduces the yaw rate amplitude of the vehicle by 10% to 15%, reduces the time for the vehicle to stabilize by about 50%, and improves driving stability.

Description

Technical Field

[0001] This invention belongs to the field of vehicle technology, specifically relating to an adjustment mechanism and active control method for the kingpin inclination angle of a MacPherson strut suspension. Technical Background

[0002] Vehicle handling and comfort are closely related to suspension structure and various related parameters. Currently, most passenger cars use MacPherson independent suspension for the front suspension, and the caster angle is one of the parameters. The caster angle is the angle between the kingpin axis in the side view and the tire's Z-axis. The initial value of the caster angle of the MacPherson independent suspension is determined during the design phase. However, in later vehicle use, it cannot meet the requirements of different operating conditions, vehicle speeds, and steering, and can only passively adapt to various driving conditions. When the caster angle is not met, it will cause wheel shimmy, fail to provide appropriate steering return torque, and may also cause vibration and noise, potentially leading to a deterioration of steering and handling performance.

[0003] With the increasing importance of active safety year by year, research on active control of the caster angle of MacPherson suspension is necessary and forward-looking. However, the control method is the core part of the control system, and the accuracy and limitations of the algorithm largely determine the performance of MacPherson suspension with active control of the caster angle.

[0004] Theoretical analysis of the kingpin inclination angle of MacPherson strut suspension in passenger vehicles reveals that its magnitude is related to factors such as wheelbase, track width, kingpin inclination angle, and wheel camber angle. Once these parameters are selected, suspension designers typically obtain the expected static kingpin inclination angle value directly through theoretical calculations. However, during vehicle operation, the forces on the steering wheels change due to the vehicle's driving posture, and the kingpin inclination angle also changes with wheel movement due to the MacPherson strut suspension structure. If the predetermined kingpin inclination angle value fails to meet the vehicle's dynamic requirements, it severely impacts vehicle stability. There is some research on active control mechanisms for the kingpin inclination angle, such as using worm gears to control the longitudinal horizontal displacement of the kingpin upper pivot. However, worm gear transmission has low efficiency and is prone to backlash, which has defects in the precise adjustment and control of the kingpin inclination angle. Furthermore, there is currently no mathematical model that can combine multiple factors such as vehicle speed and acceleration to obtain real-time and precise control of the MacPherson strut suspension kingpin inclination angle. Summary of the Invention

[0005] In order to achieve active control of the kingpin inclination angle of a passenger vehicle suspension during driving, and theoretically solve the problem of mismatch between the kingpin inclination angle and the vehicle state, this invention provides an adjustment mechanism for the kingpin inclination angle of a MacPherson independent suspension, and also provides an active adjustment method for the kingpin inclination angle of a MacPherson independent suspension.

[0006] An adjustment mechanism for the kingpin inclination angle of a MacPherson strut suspension includes a MacPherson strut suspension and a pair or more adjustment mechanisms.

[0007] The adjustment mechanism includes a support 4, an adjustment motor 5, a gear and rack mechanism, and a guide mechanism.

[0008] The support 4 is a U-shaped support; the adjusting motor 5 is fixedly mounted on the base plate inside the support 4.

[0009] The gear and rack mechanism includes a gear 6 and a rack 8; the gear 6 is fixedly mounted on the output shaft of the adjusting motor 5 via a spline fit; the two ends of the rack 8 in the length direction are respectively fixed to the two side plates inside the support 4 via connecting rods.

[0010] The guiding mechanism includes a guide bracket 9 and a guide shaft 10. The guide bracket 9 is a rectangular block with a guide hole in the middle. The guide shaft 10 is fitted into the guide hole of the guide bracket 9. The two ends of the guide shaft 10 are respectively fixed to the two side plates inside the support 4, and the guide shaft 10 is parallel to the rack 8.

[0011] The guide bracket 9 is fixedly connected to the back of the rack 8 through a pair of upper mounting holes at the top; the guide bracket 9 is fixedly connected to the upper fulcrum of the damper 12 through the bottom.

[0012] The technical solution for further defining the regulating mechanism is as follows:

[0013] The top of the guide bracket 9 is provided with an upper protrusion, and a pair of upper mounting holes are provided on the upper protrusion. The bottom sides of the guide bracket 9 are respectively provided with lower protrusions, and lower mounting holes are provided on the lower protrusions.

[0014] The active control operation steps based on a MacPherson strut steering wheel kingpin caster angle adjustment mechanism are as follows:

[0015] (1) Establish a calculation model for wheel return torque.

[0016] For the entire vehicle, the forward direction is taken as the positive x-axis, the rightward direction as the positive y-axis, and the upward direction as the positive z-axis; the wheel self-aligning torque consists of the following four parts: the self-aligning torque generated by the lateral force. Kingpin inclination angle The resulting restoring torque The restoring torque generated by the longitudinal force The restoring torque generated by the vehicle's own weight ;

[0017] The main pin axis is the line connecting the center of the upper fulcrum of the damper and the center of the outer ball head of the lower swing arm. In this invention, due to the existence of the adjustment mechanism, the main pin axis L should be the line connecting the center point of the back of the moving rack 8 and the center of the outer ball head of the lower swing arm 3.

[0018] Let the vehicle's forward direction be the positive X-axis, the rightward movement be the positive Y-axis, and the upward movement be the positive Z-axis; L is the kingpin axis; L1 is the projection of the kingpin axis L onto the XOZ plane; L2 is the projection of the kingpin axis onto the YOZ plane; the kingpin caster angle... The angle between L1 and the Z-axis is the kingpin backslope angle; the kingpin inclination angle is... The angle between L2 and the Z-axis is the kingpin inclination angle.

[0019] The formula for calculating the wheel return torque is as follows: ;

[0020] In formula (17), To provide the restoring torque, The restoring torque generated by the lateral force, The self-correcting torque generated by the inward inclination of the main pin The restoring torque generated by the longitudinal force, The restoring torque generated by the vehicle's own weight;

[0021] (2) Establish a calculation model for the positive resistance torque of the steering wheel.

[0022] The formula for calculating the positive resistance torque of the steering wheel return is as follows:

[0023]

[0024] In formula (20), This represents the dynamic load coefficient of the axle, and is dimensionless. This represents the friction coefficient of the upper pivot kingpin bearing, which is dimensionless. This indicates the radius of the upper pivot kingpin bearing, in meters (m). This represents the coefficient of bearing friction between the steering knuckle and the lower control arm; it is dimensionless. This indicates the bearing radius between the steering knuckle and the lower control arm, in meters (m). This represents the road surface adhesion coefficient, which is dimensionless. The kingpin inclination angle is represented in degrees (°); r represents the wheel rolling radius, in units of... ;

[0025] (3) Establish the calculation formula for active control of caster angle during vehicle operation.

[0026] When the vehicle is moving, the steering wheels stop returning to center when the total return torque of the front wheels is balanced with the total return resistance torque. The formula for balancing the total return torque and the total return resistance torque is as follows:

[0027]

[0028] Based on formulas (17), (20), and (21), the calculation formula for active control of kingpin caster angle is as follows:

[0029]

[0030] In formula (22), The frictional resistance distance experienced by the kingpin at the upper pivot bearing and the lower control arm and steering knuckle bearing when the wheel rotates is expressed in N·m. It is the sum of the frictional resistance torque of the steering transmission mechanism and the resistance torque when the steering gear reverses, in N·m; This represents the frictional torque between the road surface and the tire, expressed in N·m. The lateral force acting on the tire is expressed in N; r represents the wheel rolling radius, expressed in units of... ; Indicates the axle spacing, in units of ;

[0031] The ideal kingpin inclination angle is obtained according to equation (22). The rotation direction and angle of the adjusting motor 5 in the adjusting mechanism are controlled. The adjusting bracket 9 is driven by the gear and rack mechanism to adjust the horizontal displacement, thereby realizing the corresponding adjustment of the kingpin axis L, and finally realizing the kingpin inclination angle. Active regulation;

[0032] For two-wheel steering vehicles, the ideal caster angle value is calculated by treating the two steering wheels as a whole, following the steps above, so as to achieve active adjustment of the caster angle.

[0033] For vehicles with four-wheel steering, calculate the ideal front caster angle as a whole using the two front steering wheels as a whole, and calculate the ideal rear caster angle as a whole using the two rear steering wheels as a whole. Based on the ideal front and rear caster angles, actively adjust the caster angles of the front and rear wheels respectively.

[0034] The technical solution for the further defined active control method is as follows:

[0035] In step (1), the direction of vehicle movement is taken as the positive x-axis, the rightward direction of vehicle movement is taken as the positive y-axis, and the upward direction is taken as the positive z-axis.

[0036] (1.1) Calculate the restoring torque generated by the lateral force.

[0037] Righting moment Due to lateral force Total tire trail It is derived from product calculation;

[0038] (1.1.1) Calculate the lateral force

[0039] Lateral force The calculation formula is as follows:

[0040]

[0041] In formula (3): This represents the coefficient of sliding friction, which is dimensionless. Indicates tire camber stiffness ; This indicates the wheel camber angle, measured in rad. This indicates the turning radius, in meters (m). Indicates vehicle speed, in units of h; Representing the dimensionless sideslip angle: ,in This is the front wheel slip angle, in degrees. Tire slip angle Tire lateral stiffness at time, in units , This is the front wheel toe angle, in degrees;

[0042] It is the total vertical load on the steering wheel :

[0043] The formula for the vertical load on the first right tire is as follows:

[0044]

[0045] The formula for the vertical load on the first left tire is as follows:

[0046]

[0047] The vertical load on the right tire is expressed in units of... ; The vertical load on the left tire is expressed in units of... ; Indicates the total vehicle mass, in units of ; This represents the distance from the vehicle's center of gravity to the front axle, in units of... ; Indicates the height of the center of mass, in units of ; This indicates the distance between the two kingpin axles of the front wheel and the points where they intersect the ground, in units of... ; Indicates the axle spacing, in units of ; Represents the longitudinal acceleration of a vehicle, in units of ; This represents the lateral acceleration of a vehicle, measured in units of... ;

[0048] (1.1.2) Calculate the total tire drag moment

[0049] The total tire trail consists of two parts: the tire trail and the caster angle and the tire contact patch.

[0050] The formula for calculating total tire trail is as follows:

[0051]

[0052] In formula (6): This represents the total tire drag, in units of... ; This indicates the tire trail distance, in units of... ; Indicates the kingpin inclination angle, in units of ; r represents the wheel rolling radius, in units of ; Indicates the length of the tire contact patch. The unit is ; D is the nominal outer diameter of the tire. It is the radial deformation of the axle under load, in units of ; b is the tire width, in units of C and Q are coefficients. , , This is the vertical load of the axle, in units of ;p is tire pressure, the unit is . ;

[0053] (1.1.3) Calculate the corrective torque generated by the lateral force.

[0054] The corrective torque generated by the lateral force is the product of the lateral force and the component of the total drag torque of the front wheels in the direction perpendicular to the lateral force. The total corrective torque generated by the lateral forces of the left and right wheels can be obtained according to formulas (3) and (6). Formula (7) is as follows:

[0055]

[0056] because , Substituting formula (6) into formula (7), we obtain formula (8) as follows:

[0057]

[0058] Formula (8) applies to vehicles with two-wheel steering;

[0059] For vehicles with four-wheel steering, the return torque is calculated separately for the two front steering wheels as a whole and the two rear steering wheels as a whole. The solution for the front steering wheels of a four-wheel steering vehicle is the same as in step (1.1); the solution for the rear steering wheels of a four-wheel steering vehicle differs from step (1.1) in that the solution described in step (1.1.1) is different. The total vertical load on the steering wheels is the total vertical load on the rear steering wheels. ;

[0060] The vertical load on the right tire is expressed in units of... ; The vertical load on the left tire is expressed in units of... ;

[0061] At this point, formulas (4) and (5) in step (1.1.1) above should be calculated according to formulas (41) and (51) below:

[0062] The formula for the vertical load of the second right tire (41) is as follows:

[0063] (41)

[0064] The formula for the vertical load of the second left tire (51) is as follows:

[0065] (51)

[0066] In formulas (41) and (51), Indicates the total vehicle mass, in units of ; This represents the distance from the vehicle's center of gravity to the front axle, in units of... ; Indicates the height of the center of mass, in units of ; This indicates the distance between the two kingpin axles of the front wheel and the points where they intersect the ground, in units of... ; Indicates the axle spacing, in units of ; Represents the longitudinal acceleration of a vehicle, in units of ; This represents the lateral acceleration of a vehicle, measured in units of... ;

[0067] The other operations for solving the rear steering wheel of a four-wheel steering vehicle are the same as in step (1.1).

[0068] (1.2) Calculate the restoring torque generated by the kingpin inclination.

[0069] According to the Ackermann ideal relation, during vehicle cornering, due to the presence of toe angle, the steering angles of the left and right steering wheels are not equal, thus causing a self-centering torque. Calculations need to be made separately for the left and right steering wheels;

[0070] Righting moment It is the kingpin inclination angle of the left steering wheel. The resulting restoring torque and right steering wheel kingpin inclination angle The resulting restoring torque The sum, as shown in formula (11), is as follows:

[0071]

[0072] Assuming the vehicle turns left, the left steering wheel angle is... The unit is °; right steering wheel angle. The unit is °;

[0073] The return torque generated by the kingpin inclination angle of the right steering wheel The formula is as follows:

[0074]

[0075] The return torque generated by the kingpin inclination angle of the left steering wheel The formula is as follows:

[0076]

[0077] In formulas (9) and (10), This indicates the distance from the steering knuckle joint to the front wheel mounting center plane, in meters (m). Indicates the kingpin inclination angle, in degrees; The vertical load on the right tire is expressed in units of... ; The vertical load on the right tire is expressed in units of... ;

[0078] Formula (11) applies to vehicles with two-wheel steering;

[0079] For vehicles with four-wheel steering, the return torque is calculated by treating the two front steering wheels as a single unit and the two rear steering wheels as a single unit. The calculation of the front steering wheel as a whole is the same as in step (1.2); the calculation of the rear steering wheel as a whole differs from step (1.2) in that the calculation in step (1.2) is different. The total vertical load on the steering wheels is the total vertical load on the rear steering wheels. ;

[0080] (1.3) Calculate the restoring torque generated by the longitudinal force.

[0081] The self-aligning torques are in opposite directions. Due to the toe angle, the steering angles of the left and right steering wheels are unequal during vehicle turning, resulting in unequal magnitudes of the self-aligning torques generated by the longitudinal forces on the left and right sides. Therefore, it is necessary to solve for the self-aligning torques generated by the left and right steering wheels separately and take the difference. Assuming the vehicle is turning left... It is determined by the friction between the left front tire and the ground and the kingpin offset. The product of its vertical components and the friction between the right front tire and the ground and the kingpin offset. The difference of the products of its vertical components, the restoring torque. Formula (14) is as follows:

[0082]

[0083] In formula (14), the left steering wheel angle The unit is °; right steering wheel angle. The unit is °;

[0084]

[0085]

[0086] Formula (14) applies to vehicles with two-wheel steering;

[0087] For vehicles with four-wheel steering, the return torque is calculated by treating the two front steering wheels as a single unit and the two rear steering wheels as a single unit. The calculation of the front steering wheel as a whole is the same as in step (1.3); the calculation of the rear steering wheel as a whole differs from step (1.3) in that the calculation in step (1.3) is different. The total vertical load on the steering wheels is the total vertical load on the rear steering wheels. ;

[0088] (1.4) Calculate the restoring torque generated by the vehicle's own weight.

[0089] The restoring torque generated by the vehicle's own weight Formula (16) is as follows:

[0090]

[0091] In formula (16), The vertical force on the tire contact patch is shifted towards the wheel centerline and decomposed into two directions: parallel to the steering knuckle axis and perpendicular to the steering knuckle axis. , The force perpendicular to the kingpin axis is Considering the kingpin caster angle The force perpendicular to the kingpin axis is Due to the kingpin caster angle Usually smaller, therefore The force perpendicular to the kingpin axis is ;

[0092] Lever arm from the force dividing point to the kingpin axis for:

[0093]

[0094] Formula (15) applies to vehicles with two-wheel steering;

[0095] For vehicles with four-wheel steering, the return torque is calculated by treating the two front steering wheels as a single unit and the two rear steering wheels as a single unit. The calculation of the front steering wheel as a whole is the same as in step (1.4); the calculation of the rear steering wheel as a whole differs from step (1.4) in that the calculation in step (1.4) is different. The total vertical load on the steering wheels is the total vertical load on the rear steering wheels. ;

[0096] (1.5) Calculation model for normalizing torque

[0097] Total restoring torque Formula (17) is as follows:

[0098]

[0099] In formula (17), The restoring torque generated by the lateral force, The self-correcting torque generated by the inward inclination of the main pin The restoring torque generated by the longitudinal force, The restoring torque is generated by the vehicle's own weight.

[0100] In step (2), the return resistance torque It consists of three parts: the frictional torque experienced by the kingpin at the upper pivot bearing and the lower control arm at the steering knuckle bearing during rotation. The sum of the frictional resistance torque of the steering transmission mechanism and the resistance torque when the steering gear reverses. Friction torque between the road surface and the tire ;

[0101] (2.1) Calculate the frictional resistance distance

[0102] Frictional resistance distance The force exerted on the kingpin at the upper pivot bearing and the lower control arm and steering knuckle bearing is given by formula (18) as follows;

[0103]

[0104] In formula (18): This represents the dynamic load coefficient of the axle, and is dimensionless. This represents the friction coefficient of the upper pivot kingpin bearing, which is dimensionless. This indicates the radius of the upper pivot kingpin bearing, in meters (m). This represents the coefficient of bearing friction between the steering knuckle and the lower control arm; it is dimensionless. This indicates the bearing radius between the steering knuckle and the lower control arm, in meters (m). Indicates the kingpin inclination angle, in degrees; This is the vertical load of the axle, in units of ;

[0105] According to the force analysis, the force at the upper pivot point of the MacPherson strut suspension is... The force at the bearing between the steering knuckle and the lower control arm is ;

[0106] Formula (18) applies to vehicles with two-wheel steering;

[0107] For vehicles with four-wheel steering, the return torque is calculated by treating the two front steering wheels as a single unit and the two rear steering wheels as a single unit. The calculation of the front steering wheel as a whole is the same as in step (2.1); the calculation of the rear steering wheel as a whole differs from that in step (2.1) in that the calculation in step (2.1) is different. The total vertical load on the steering wheels is the total vertical load on the rear steering wheels. ;

[0108] (2.2) Calculate the sum of resistance torques

[0109] The sum of the frictional resistance torque of the steering transmission mechanism and the resistance torque when the steering gear reverses. Measured based on actual vehicle configuration;

[0110] (2.3) Calculate the frictional torque between the road surface and the tire.

[0111] Frictional torque between the road surface and the tire The formula (19) is obtained by multiplying the supporting force between the vehicle tire and the ground by the road surface adhesion coefficient:

[0112]

[0113] In formula (19), This represents the road surface adhesion coefficient, which is dimensionless. This is the vertical load of the axle, in units of ; r represents the wheel rolling radius, in units of ;

[0114] Formula (19) applies to vehicles with two-wheel steering;

[0115] For vehicles with four-wheel steering, the return torque is calculated by treating the two front steering wheels as a single unit and the two rear steering wheels as a single unit. The calculation of the front steering wheel as a whole is the same as in step (2.3); the calculation of the rear steering wheel as a whole differs from that in step (2.3) in that the calculation of the rear steering wheel as described in step (2.3) is different. The total vertical load on the steering wheels is the total vertical load on the rear steering wheels. ;

[0116] (2.4) Calculate the positive resistance torque M of the steering wheel. f

[0117] From equations (18) and (19), the positive resistance torque M of the steering wheel can be obtained. f Formula (20) is as follows:

[0118]

[0119] Formula (20) is the calculation model for the positive resistance torque of the steering wheel.

[0120] In step (3), when the front wheels steer and the tires begin to straighten, With the tire slip angle The decrease in lateral force generates a restoring torque. It also gradually decreases, while the restoring torque generated by the axle position energy is... The sum also varies with the steering wheel angle. The total return torque of the front wheels decreases as the total return resistance torque decreases until it balances with the total return resistance torque, at which point the steering wheels stop returning to center, resulting in the balance formula (21).

[0121] The beneficial technical effects of this invention are reflected in the following aspects:

[0122] 1. The active control method of the present invention provides a control algorithm for vehicles under different driving conditions. Specifically, when the vehicle is traveling at too high a speed and the turning angle is too large, the yaw rate of the vehicle will increase, making the car difficult to control. Therefore, the active control method of MacPherson suspension kingpin caster angle reduces the yaw rate of the vehicle by real-time monitoring factors such as vehicle speed, acceleration, and steering angle, thereby improving the vehicle's handling stability and driving safety.

[0123] 2. Referring to Example 1, in a front-wheel steering vehicle, when the vehicle speed is 100 km / h... When the wheel turning angle is 10°, the optimal kingpin inclination angle is calculated using the MacPherson suspension kingpin inclination angle control algorithm. See also Figure 9 By establishing a four-degree-of-freedom vehicle model for analysis, this active control method reduces the vehicle's yaw rate amplitude by 10% to 15% and the time it takes for the vehicle to stabilize by about 50%, thereby improving the vehicle's driving stability.

[0124] 3. This invention uses a gear and rack transmission mechanism to achieve longitudinal displacement adjustment and control of the kingpin back tilt angle. The gear and rack transmission has higher efficiency and a relatively simple manufacturing process, and its precision is easy to control, making the kingpin back tilt angle adjustment more accurate.

[0125] 4. Currently, there is some research on active control methods for caster angle, such as static methods that consider the lateral force, the self-aligning torque caused by the kingpin inclination angle, and the self-aligning torque generated by the vehicle's own weight to obtain the size of the caster angle. However, these methods do not consider the influence of wheel toe-in or the effects of changes in vehicle acceleration and turning radius caused by changes in vehicle driving posture. Therefore, the caster angle obtained by the above methods has errors and cannot meet the real-time requirements of the dynamically changing caster angle of the vehicle.

[0126] 5. This invention is applicable to all vehicles containing MacPherson strut steering wheels, and has a wide range of applications. Attached Figure Description

[0127] Figure 1 This is a schematic diagram of the structure of the present invention based on the MacPherson strut suspension;

[0128] Figure 2 This is a detailed schematic diagram of the kingpin caster angle adjustment mechanism of the present invention. Figure 1 ;

[0129] Figure 3 This is a detailed schematic diagram of the kingpin caster angle adjustment mechanism of the present invention. Figure 2 ;

[0130] Figure 4 The adjustment mechanism support 9 of this invention;

[0131] Figure 5 The adjusting mechanism rack 8 of this invention;

[0132] Figure 6 This is a schematic diagram of the installation of the present invention based on the MacPherson strut suspension;

[0133] Figure 7 This is a schematic diagram of the tire slip angle of the present invention;

[0134] Figure 8 This is a graph showing the trend of the ratio of transient yaw acceleration to steady-state yaw rate of a vehicle over time when the front wheel steering speed is 100 km / h.

[0135] Figure 9 This is a graph showing the trend of the ratio of transient yaw acceleration to steady-state yaw rate of a vehicle with a four-wheel steering speed of 100 km / h over time.

[0136] Figure 1-6 The components are numbered as follows: 1. Helical spring; 2. Half shaft; 3. Lower swing arm; 4. Support; 5. Adjusting motor; 6. Gear; 7. Motor spline shaft; 8. Rack; 9. Adjusting bracket; 10. Guide load-bearing rod. Detailed Implementation

[0137] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0138] Example 1

[0139] See Figure 1 A MacPherson strut steering wheel caster adjustment mechanism includes a MacPherson strut suspension and one or more adjustment mechanisms.

[0140] See Figure 2 The adjustment mechanism includes a support 4, an adjustment motor 5, a gear and rack mechanism, and a guide mechanism.

[0141] See Figure 2 Support 4 is a U-shaped support; the adjusting motor 5 is fixedly installed on the base plate inside support 4.

[0142] See Figure 2 The gear and rack mechanism includes a gear 6 and a rack 8; the gear 6 is fixedly mounted on the output shaft of the regulating motor 5 via a spline fit; the two ends of the rack 8 in the length direction are respectively fixedly mounted on the two side plates inside the support 4 via connecting rods.

[0143] See Figure 3The guiding mechanism includes a guide bracket 9 and a guide shaft 10. The guide bracket 9 is a rectangular block with a guide hole in the middle. The guide shaft 10 is fitted into the guide hole of the guide bracket 9. The two ends of the guide shaft 10 are respectively fixed to the two side plates inside the support 4, and the guide shaft 10 is parallel to the rack 8.

[0144] See Figure 4 The top of the guide bracket 9 is provided with an upper protrusion, and a pair of upper mounting holes are provided on the upper protrusion. The bottom sides of the guide bracket 9 are respectively provided with lower protrusions, and lower mounting holes are provided on the lower protrusions.

[0145] See Figure 6 The guide bracket 9 is fixedly connected to the back of the rack 8 through a pair of mounting holes on the top upper protrusion; the guide bracket 9 is fixedly connected to the upper fulcrum of the damper 12 through the bottom.

[0146] See Figure 1 In the coordinate system, the direction of vehicle movement is the positive X-axis, the rightward direction of vehicle movement is the positive Y-axis, and upward is the positive Z-axis; L is the kingpin axis; L1 is the projection of the kingpin axis L onto the XOZ plane; L2 is the projection of the kingpin axis onto the YOZ plane. The angle between L1 and the Z-axis is the kingpin inclination angle. The angle between L2 and the Z-axis is the kingpin inclination angle.

[0147] Example 2

[0148] Analysis of front-wheel steering implementation examples:

[0149] Taking a domestically produced passenger vehicle as the research object, the detailed parameters of the vehicle are as follows:

[0150]

[0151]

[0152]

[0153]

[0154] 100 km / h The longitudinal acceleration is 0, the lateral acceleration is 3 m / s², and the rotation angle is 10°.

[0155] Under normal driving conditions of the aforementioned vehicle, the active control operation steps based on the adjustment mechanism of the kingpin inclination angle of the MacPherson strut steering wheel are as follows:

[0156] (1) Establish a calculation model for wheel return torque.

[0157] For the entire vehicle, the forward direction is taken as the positive x-axis, the rightward direction as the positive y-axis, and the upward direction as the positive z-axis; the wheel self-aligning torque consists of the following four parts: the self-aligning torque generated by the lateral force. Kingpin inclination angle The resulting restoring torque The restoring torque generated by the longitudinal force The restoring torque generated by the vehicle's own weight ;

[0158] The main pin axis is the line connecting the center of the upper fulcrum of the damper and the center of the outer ball head of the lower swing arm. In this invention, due to the existence of the adjustment mechanism, the main pin axis L should be the line connecting the center point of the back of the moving rack 8 and the center of the outer ball head of the lower swing arm 3.

[0159] See Figure 1 ,exist Figure 1 In the coordinate system, let the vehicle's forward direction be the positive X-axis, the rightward movement be the positive Y-axis, and the upward movement be the positive Z-axis; L is the kingpin axis; L1 is the projection of the kingpin axis L onto the XOZ plane; L2 is the projection of the kingpin axis onto the YOZ plane; the kingpin caster angle... The angle between L1 and the Z-axis is the kingpin backslope angle; the kingpin inclination angle is... The angle between L2 and the Z-axis is the kingpin inclination angle.

[0160] The formula for calculating the wheel return torque is as follows: ;

[0161] In formula (17), To provide the restoring torque, The restoring torque generated by the lateral force, The self-correcting torque generated by the inward inclination of the main pin The restoring torque generated by the longitudinal force, The restoring torque is generated by the vehicle's own weight.

[0162] The specific steps for step (1) are as follows:

[0163] With the vehicle's forward direction as the positive x-axis, the rightward direction as the positive y-axis, and the upward direction as the positive z-axis;

[0164] (1.1) Calculate the restoring torque generated by the lateral force.

[0165] Righting moment Due to lateral force Total tire trail It is derived from product calculation;

[0166] (1.1.1) Calculate the lateral force

[0167] Lateral force The calculation formula is as follows:

[0168]

[0169] In formula (3): This indicates that the coefficient of sliding friction is 0.8; This indicates that the tire camber stiffness is 2000. ; Indicates wheel camber angle -1 ; This indicates that the vehicle's speed is 100. h; Representing the dimensionless sideslip angle: ,in The front wheel slip angle is 1°. Tire slip angle The tire lateral stiffness at that time was 2000. , With the front wheel toe angle set at 0.1667°, the following is derived: The value is 0.0035;

[0170] It is the total vertical load on the steering wheel :

[0171] The formula for the vertical load on the first right front tire is as follows:

[0172]

[0173] The formula for the vertical load on the first left front tire is as follows:

[0174]

[0175] Vertical load on the right front tire, in units of ; Vertical load on the left front tire, in units of ; Indicates the total vehicle weight as ; This indicates the distance from the vehicle's center of gravity to the front axle. ; The height of the centroid is ; This indicates the distance between the intersection points of the two kingpin axes of the front wheel and the ground. ; Indicates the axle spacing as ; The longitudinal acceleration of the vehicle is... ; The lateral acceleration of the vehicle is... Substituting the above parameters into formula (4), formula (5) calculates... 6384 , It is 3894N. It is 10278N; Substituting into formula (3), we get It is 2028.78N.

[0176] (1.1.2) Calculate the total tire drag moment

[0177] The total tire trail consists of two parts: the tire trail and the caster angle and the tire contact patch.

[0178] The formula for calculating total tire trail is as follows:

[0179]

[0180] In formula (6): This represents the total tire drag, in units of... ; This indicates the tire trail distance, in units of... ; Indicates the kingpin inclination angle, in units of ; r represents the rolling radius of the wheel. ; Indicates the length of the tire contact patch. The unit is ; D represents the nominal outer diameter of the front wheel, which is 0.508m. It is the radial deformation of the axle under load, in units of b is the tire width. C and Q are coefficients. , , The front axle vertical load is 10278. ;p means the tire pressure is 200. Substitute the above parameters into formula (6) to calculate It is 0.0317 + 0.0254 ;

[0181] (1.1.3) Calculate the corrective torque generated by the lateral force.

[0182] The corrective torque generated by the lateral force is the product of the lateral force and the component of the total drag torque of the front wheels in the direction perpendicular to the lateral force. The total corrective torque generated by the lateral forces of the left and right wheels can be obtained according to formulas (3) and (6). Formula (7) is as follows:

[0183]

[0184] because , Substituting formula (6) into formula (7), we obtain formula (8) as follows:

[0185]

[0186] Substituting the calculation results from steps (1.1.1) and (1.1.2) into formula (8), we obtain the correcting torque generated by the lateral force. It is 64.31 + 51.53 N·m.

[0187] (1.2) Calculate the restoring torque generated by the kingpin inclination.

[0188] According to the Ackermann ideal relation, during vehicle cornering, due to the presence of toe angle, the steering angles of the left and right steering wheels are not equal, thus causing a self-centering torque. Calculations need to be made separately for the left and right steering wheels;

[0189] Righting moment It is the kingpin inclination angle of the left steering wheel. The resulting restoring torque and right steering wheel kingpin inclination angle The resulting restoring torque The sum, as shown in formula (11), is as follows:

[0190]

[0191] Assuming the vehicle turns left, the left steering wheel angle is... It is 10.1667°; right steering wheel angle It is 9.8333°;

[0192] The return torque generated by the kingpin inclination angle of the right steering wheel The formula is as follows:

[0193]

[0194] The return torque generated by the kingpin inclination angle of the left steering wheel The formula is as follows:

[0195]

[0196] In formulas (9) and (10), This indicates that the distance from the steering knuckle joint to the front wheel mounting center plane is 0.2m; This indicates that the kingpin inclination angle is 8°; The vertical load on the right front tire is 6384. ; The vertical load on the right front tire is 3894. Substitute the above parameters into formula (11) to calculate the restoring torque generated by the kingpin inclination. It is 97.99 N·m.

[0197] (1.3) Calculate the restoring torque generated by the longitudinal force.

[0198] The self-aligning torques are in opposite directions. Due to the toe angle, the steering angles of the left and right steering wheels are unequal during vehicle turning, resulting in unequal magnitudes of the self-aligning torques generated by the longitudinal forces on the left and right sides. Therefore, it is necessary to solve for the self-aligning torques generated by the left and right steering wheels separately and take the difference. Assuming the vehicle is turning left... It is determined by the friction between the left front tire and the ground and the kingpin offset. The product of its vertical components and the friction between the right front tire and the ground and the kingpin offset. The difference of the products of its vertical components, the restoring torque. Formula (14) is as follows:

[0199]

[0200] In formula (14), the left steering wheel angle The unit is °; right steering wheel angle. The unit is °;

[0201]

[0202]

[0203] In formula (14), the kingpin offset distance The rolling friction coefficient is 0.04m. It is 0.8. The vertical load on the right tire is 6384. ; The vertical load on the left tire is 3894. Left steering wheel angle It is 10.1667°; right steering wheel angle The value is 9.8333°; substituting the above parameters into formula (14) yields the result. It is 201.29 N·m. The value is 122.65 N·m. Therefore, the restoring torque generated by the longitudinal force is... It is 78.64 N·m.

[0204] (1.4) Calculate the restoring torque generated by the vehicle's own weight.

[0205] The restoring torque generated by the vehicle's own weight Formula (16) is as follows:

[0206]

[0207] In formula (16), The vertical force on the tire contact patch is shifted towards the wheel centerline and decomposed into two directions: parallel to the steering knuckle axis and perpendicular to the steering knuckle axis. , The force perpendicular to the kingpin axis is Considering the kingpin caster angle The force perpendicular to the kingpin axis is Due to the kingpin caster angle Usually smaller, therefore The force perpendicular to the kingpin axis is ;

[0208] Lever arm from the force dividing point to the kingpin axis for:

[0209]

[0210] In formula (14), the kingpin offset distance It is 0.04m. The vertical load on the right front tire is 6384. ; The vertical load on the right front tire is 3894. Left steering wheel angle It is 10.1667°; right steering wheel angle The angle is 9.8333°; substituting the above parameters into formula (16) yields the restoring torque generated by the vehicle's own weight. It is 18.54 N·m.

[0211] (1.5) Calculation model for normalizing torque

[0212] Total restoring torque Formula (17) is as follows:

[0213]

[0214] In formula (17), The restoring torque generated by the lateral force, The self-correcting torque generated by the inward inclination of the main pin The restoring torque generated by the longitudinal force, The total restoring torque is calculated by substituting the results of steps (1.1), (1.2), (1.3), and (1.4) into formula (17) to obtain the restoring torque, which is the restoring torque generated by the vehicle's own weight. It is 259.48 + 51.53 N·m.

[0215] (2) Establish a calculation model for the positive resistance torque of the steering wheel.

[0216] The formula for calculating the positive resistance torque of the steering wheel return is as follows:

[0217]

[0218] In formula (20), This represents the dynamic load coefficient of the axle, and is dimensionless. This represents the friction coefficient of the upper pivot kingpin bearing, which is dimensionless. This indicates the radius of the upper pivot kingpin bearing, in meters (m). This represents the coefficient of bearing friction between the steering knuckle and the lower control arm; it is dimensionless. This indicates the bearing radius between the steering knuckle and the lower control arm, in meters (m). This represents the road surface adhesion coefficient, which is dimensionless. The kingpin inclination angle is represented in degrees (°); r represents the wheel rolling radius, in units of... .

[0219] The specific steps for step (2) are as follows:

[0220] Returning resistance torque It consists of three parts: the frictional torque experienced by the kingpin at the upper pivot bearing and the lower control arm at the steering knuckle bearing during rotation. The sum of the frictional resistance torque of the steering transmission mechanism and the resistance torque when the steering gear reverses. Friction torque between the road surface and the tire ;

[0221] (2.1) Calculate the frictional resistance distance

[0222] Frictional resistance distance The force exerted on the kingpin at the upper pivot bearing and the lower control arm and steering knuckle bearing is given by formula (18) as follows;

[0223]

[0224] In formula (18): This indicates that the dynamic load factor of the axle is 1; This indicates that the friction coefficient of the upper pivot kingpin bearing is 0.02; This indicates that the radius of the upper pivot kingpin bearing is 0.03m; This indicates that the coefficient of friction of the bearing between the steering knuckle and the lower control arm is 0.02. This indicates that the bearing radius between the steering knuckle and the lower control arm is 0.03m; This indicates that the kingpin inclination angle is 8°; The vertical load of the axle is 10278. Substituting the above parameters into formula (18) yields the frictional torque. It is 7.09 N·m.

[0225] (2.2) Calculate the sum of resistance torques

[0226] The sum of the frictional resistance torque of the steering transmission mechanism and the resistance torque when the steering gear reverses. The actual measured value based on the vehicle configuration is 32.5 N·m.

[0227] (2.3) Calculate the frictional torque between the road surface and the tire.

[0228] Frictional torque between the road surface and the tire The formula (19) is obtained by multiplying the supporting force between the vehicle tire and the ground by the road surface adhesion coefficient:

[0229]

[0230] In formula (19), This indicates that the road surface adhesion coefficient is 0.27; The vertical load of the axle is 10278. Substituting the above parameters into formula (19), the frictional torque between the road surface and the tire is calculated. It is 704.87 N·m.

[0231] (2.4) Calculate the positive resistance torque M of the steering wheel. f

[0232] From equations (18) and (19), the positive resistance torque M of the steering wheel can be obtained. f Formula (20) is as follows:

[0233]

[0234] Formula (20) is the calculation model for the positive resistance torque of the steering wheel. Substituting the results of steps (2.1), (2.2), and (2.3) into formula (20) yields the positive resistance torque of the steering wheel. It is 744.46 N·m.

[0235] (3) Establish the calculation formula for active control of caster angle during vehicle operation.

[0236] When the vehicle is moving, the steering wheels stop returning to center when the total return torque of the front wheels is balanced with the total return resistance torque. The formula for balancing the total return torque and the total return resistance torque is as follows:

[0237]

[0238] Based on formulas (17), (20), and (21), the calculation formula for active control of kingpin caster angle is as follows:

[0239]

[0240] In formula (22), The frictional resistance distance experienced by the kingpin at the upper pivot bearing and the lower control arm and steering knuckle bearing when the wheel rotates is expressed in N·m. It is the sum of the frictional resistance torque of the steering transmission mechanism and the resistance torque when the steering gear reverses, in N·m; This represents the frictional torque between the road surface and the tire, expressed in N·m. The lateral force acting on the tire is expressed in N; r represents the wheel rolling radius, expressed in units of... ; Indicates the axle spacing, in units of ;

[0241] The ideal kingpin inclination angle is obtained according to equation (22). The rotation direction and angle of the adjusting motor 5 in the adjusting mechanism are controlled. The adjusting bracket 9 is driven by the gear and rack mechanism to adjust the horizontal displacement, thereby realizing the corresponding adjustment of the kingpin axis L, and finally realizing the kingpin inclination angle. Active adjustment.

[0242] When the front wheels turn, the tires begin to straighten. With the tire slip angle The decrease, see Figure 7 The restoring torque generated by the lateral force It also gradually decreases, while the restoring torque generated by the axle position energy is... The sum also varies with the steering wheel angle. The total return torque of the front wheels decreases as the total return resistance torque is balanced, and the steering wheels stop returning to center, resulting in the balance formula (21). Substituting the calculation results from steps (1) and (2) into formula (22) yields the ideal caster angle under the current vehicle condition. .

[0243] To verify the improvement in vehicle stability achieved by the active kingpin caster angle control method in Example 1, a four-degree-of-freedom vehicle model was established, taking into account the vehicle's lateral motion, yaw motion, roll motion, and wheel rotation around the kingpin.

[0244]

[0245] Taking the two-wheel steering vehicle of Embodiment 1 as the research object, the vehicle speed was calculated by analyzing the lateral motion, yaw motion, and roll motion of the prototype vehicle. The transient response of the yaw rate at the original caster angle and the caster angle obtained by the algorithm is analyzed, and the time history of the ratio of transient to steady-state yaw rate of the prototype vehicle is analyzed; see [link to relevant documentation]. Figure 8 It can be seen that the active control method of the MacPherson strut steering wheel kingpin inclination angle adjustment mechanism of the present invention achieves the desired kingpin inclination angle. The yaw rate overshoot corresponding to the original kingpin caster angle is lower than that corresponding to the original kingpin caster angle, and the settling time is shorter, proving that the kingpin caster angle... Algorithms can help improve vehicle driving stability.

[0246] Example 3

[0247] Analysis of a Four-Wheel Steering Example:

[0248] Taking a domestically produced passenger vehicle as the research object, the detailed parameters of the vehicle are as follows:

[0249]

[0250]

[0251]

[0252] Front wheel alignment parameters:

[0253] Rear wheel alignment parameters:

[0254] 100 km / h The longitudinal acceleration is 0, the lateral acceleration is 3 m / s², the front wheel angle is 10°, and the rear wheel angle is 3°.

[0255] The calculation process for the active control method of caster angle with a front wheel steering angle of 10° is the same as in Example 2. Therefore, it is only necessary to calculate the predicted ideal caster angle with a rear wheel steering angle of 3°. The operation steps are as follows:

[0256] (1) Establish a calculation model for wheel return torque.

[0257] For the entire vehicle, the forward direction is taken as the positive x-axis, the rightward direction as the positive y-axis, and the upward direction as the positive z-axis; the wheel self-aligning torque consists of the following four parts: the self-aligning torque generated by the lateral force. Kingpin inclination angle The resulting restoring torque The restoring torque generated by the longitudinal force The restoring torque generated by the vehicle's own weight ;

[0258] The main pin axis is the line connecting the center of the upper fulcrum of the damper and the center of the outer ball head of the lower swing arm. In this invention, due to the existence of the adjustment mechanism, the main pin axis L should be the line connecting the center point of the back of the moving rack 8 and the center of the outer ball head of the lower swing arm 3.

[0259] See Figure 1 ,exist Figure 1 In the coordinate system, let the vehicle's forward direction be the positive X-axis, the rightward movement be the positive Y-axis, and the upward movement be the positive Z-axis; L is the kingpin axis; L1 is the projection of the kingpin axis L onto the XOZ plane; L2 is the projection of the kingpin axis onto the YOZ plane; the kingpin caster angle... The angle between L1 and the Z-axis is the kingpin backslope angle; the kingpin inclination angle is... The angle between L2 and the Z-axis is the kingpin inclination angle.

[0260] The formula for calculating the wheel return torque is as follows: ;

[0261] In formula (17), To provide the restoring torque, The restoring torque generated by the lateral force, The self-correcting torque generated by the inward inclination of the main pin The restoring torque generated by the longitudinal force, The restoring torque generated by the vehicle's own weight;

[0262] The specific steps for step (1) are as follows:

[0263] With the vehicle's forward direction as the positive x-axis, the rightward direction as the positive y-axis, and the upward direction as the positive z-axis;

[0264] (1.1) Calculate the restoring torque generated by the lateral force.

[0265] Righting moment Due to lateral force Total tire trail It is derived from product calculation;

[0266] (1.1.1) Calculate the lateral force

[0267] Lateral force The calculation formula is as follows:

[0268]

[0269] In formula (3): ; ; ; ; ,in , , Calculation The value is 0.0035;

[0270] It is the total vertical load on the steering wheel :

[0271] The formula for the vertical load on the second right rear tire is as follows:

[0272]

[0273] The formula for the vertical load on the second left rear tire is as follows:

[0274]

[0275] The parameters in formulas (41) and (51) are: ; ; ; ; ; ; Substituting the above parameters into formulas (41) and (51) yields the results. 6384 , It is 3894N, therefore, For 10278N, Substitute into formula (3) to calculate It is 2028.78N.

[0276] (1.1.2) Calculate the total tire drag moment

[0277] The total tire trail consists of two parts: the tire trail and the caster angle and the tire contact patch.

[0278] The formula for calculating total tire trail is as follows:

[0279]

[0280] In formula (6): ; ; D = 0.508m, b = 0.275 C and Q are coefficients. , , 10278 p = 200 Substituting the above parameters into formula (6) yields the result. = 0.0317 + 0.0254 ;

[0281] (1.1.3) Calculate the corrective torque generated by the lateral force.

[0282] The corrective torque generated by the lateral force is the product of the lateral force and the component of the total drag torque of the front wheels in the direction perpendicular to the lateral force. The total corrective torque generated by the lateral forces of the left and right wheels can be obtained according to formulas (3) and (6). Formula (7) is as follows:

[0283]

[0284] because , Substituting formula (6) into formula (7), we obtain formula (8) as follows:

[0285]

[0286] Substituting the calculation results from steps (1.1.1) and (1.1.2) into formula (8), we obtain the correcting torque generated by the lateral force. It is 64.31 + 51.53 N·m.

[0287] (1.2) Calculate the restoring torque generated by the kingpin inclination.

[0288] According to the Ackermann ideal relation, during vehicle cornering, due to the presence of toe angle, the steering angles of the left and right steering wheels are not equal, thus causing a self-centering torque. Calculations need to be made separately for the left and right steering wheels;

[0289] Righting moment It is the kingpin inclination angle of the left steering wheel. The resulting restoring torque and right steering wheel kingpin inclination angle The resulting restoring torque The sum, as shown in formula (11), is as follows:

[0290]

[0291] Assuming the vehicle turns left, the left steering wheel angle is... The right steering wheel angle is 3.1667°. It is 2.8333°;

[0292] The return torque generated by the kingpin inclination angle of the right steering wheel The formula is as follows:

[0293]

[0294] The return torque generated by the kingpin inclination angle of the left steering wheel The formula is as follows:

[0295]

[0296] In formulas (9) and (10), = 0.2m; ; ; Substitute the above parameters into formula (11) to calculate the restoring torque generated by the kingpin inclination. It is 29.12 N·m.

[0297] (1.3) Calculate the restoring torque generated by the longitudinal force.

[0298] The self-aligning torques are in opposite directions. Due to the toe angle, the steering angles of the left and right steering wheels are unequal during vehicle turning, resulting in unequal magnitudes of the self-aligning torques generated by the longitudinal forces on the left and right sides. Therefore, it is necessary to solve for the self-aligning torques generated by the left and right steering wheels separately and take the difference. Assuming the vehicle is turning left... It is determined by the friction between the left rear tire and the ground and the kingpin offset. The product of its vertical components and the friction between the right rear tire and the ground and the kingpin offset. The difference of the products of its vertical components, the restoring torque. Formula (14) is as follows:

[0299]

[0300] In formula (14), the left steering wheel angle The right steering wheel angle is 3.1667°. It is 2.8333°;

[0301]

[0302]

[0303] In formula (14) , = 0.8, ; ; °; 2.8333°; Substituting the above parameters into formula (14) yields the result. It is 204.04 N·m. The value is 122.98 N·m. Therefore, the restoring torque generated by the longitudinal force is... It is 81.06 N·m.

[0304] (1.4) Calculate the restoring torque generated by the vehicle's own weight.

[0305] The restoring torque generated by the vehicle's own weight Formula (16) is as follows:

[0306]

[0307] In formula (16), the lever arm from the force dividing point to the kingpin axis is... for:

[0308]

[0309] In formula (14) , ; ; 3.1667°; 2.8333°; Substituting the above parameters into formula (16), the restoring torque generated by the vehicle's own weight is calculated. It is 5.51 N·m.

[0310] (1.5) Calculation model for normalizing torque

[0311] Total restoring torque Formula (17) is as follows:

[0312]

[0313] In formula (17), The restoring torque generated by the lateral force, The self-correcting torque generated by the inward inclination of the main pin The restoring torque generated by the longitudinal force, The restoring torque is generated by the vehicle's own weight. Substituting the results of steps (1.1), (1.2), (1.3), and (1.4) into formula (17) yields the total restoring torque. It is 180 + 51.53 N·m.

[0314] (2) Establish a calculation model for the positive resistance torque of the steering wheel.

[0315] The formula for calculating the positive resistance torque of the steering wheel return is as follows:

[0316]

[0317] The specific steps for step (2) are as follows:

[0318] Returning resistance torque It consists of three parts: the frictional torque experienced by the kingpin at the upper pivot bearing and the lower control arm at the steering knuckle bearing during rotation. The sum of the frictional resistance torque of the steering transmission mechanism and the resistance torque when the steering gear reverses. Friction torque between the road surface and the tire ;

[0319] (2.1) Calculate the frictional resistance distance

[0320] Frictional resistance distance The force exerted on the kingpin at the upper pivot bearing and the lower control arm and steering knuckle bearing is given by formula (18) as follows;

[0321]

[0322] In formula (18): = 1; = 0.02; ; = 0.02; ; ; Substitute the above parameters into formula (18) to calculate the friction torque. It is 7.09 N·m.

[0323] (2.2) Calculate the sum of resistance torques

[0324] The sum of the frictional resistance torque of the steering transmission mechanism and the resistance torque when the steering gear reverses. The actual measured value based on the vehicle configuration is 32.5 N·m;

[0325] (2.3) Calculate the frictional torque between the road surface and the tire.

[0326] Frictional torque between the road surface and the tire The formula (19) is obtained by multiplying the supporting force between the vehicle tire and the ground by the road surface adhesion coefficient:

[0327]

[0328] In formula (19), = 0.15; r = 0.254 Substitute the above parameters into formula (19) to calculate the frictional torque between the road surface and the tire. It is 391.59 N·m;

[0329] (2.4) Calculate the positive resistance torque M of the steering wheel. f

[0330] From equations (18) and (19), the positive resistance torque M of the steering wheel can be obtained. f Formula (20) is as follows:

[0331]

[0332] Formula (20) is the calculation model for the positive resistance torque of the steering wheel. Substituting the results of steps (2.1), (2.2), and (2.3) into formula (20) yields the positive resistance torque of the steering wheel. It is 431.18 N·m.

[0333] (3) Establish the calculation formula for active control of caster angle during vehicle operation.

[0334] When the vehicle is moving, the steering wheels stop returning to center when the total return torque of the rear wheels is balanced with the total return resistance torque. The formula for balancing the total return torque and the total return resistance torque (21) is as follows:

[0335]

[0336] Based on formulas (17), (20), and (21), the calculation formula for active control of kingpin caster angle is as follows:

[0337]

[0338] The ideal kingpin inclination angle is obtained according to equation (22). The rotation direction and angle of the adjusting motor 5 in the adjusting mechanism are controlled. The adjusting bracket 9 is driven by the gear and rack mechanism to adjust the horizontal displacement, thereby realizing the corresponding adjustment of the kingpin axis L, and finally realizing the kingpin inclination angle. Active adjustment.

[0339] When the rear wheels turn, the tires begin to straighten. With the tire slip angle The decrease, see Figure 7 The restoring torque generated by the lateral force It also gradually decreases, while the restoring torque generated by the axle position energy is... The sum also varies with the steering wheel angle. The total return torque of the front wheels decreases as the total return resistance torque is balanced, and the steering wheels stop returning to center, resulting in the balance formula (21). Substituting the calculation results from steps (1) and (2) into formula (22) yields the ideal caster angle under the current vehicle condition. .

[0340] To verify the improvement in vehicle stability achieved by the active caster angle control method in Example 1, a three-degree-of-freedom model of the vehicle was established, taking into account lateral motion, yaw motion, and roll motion. By considering the driver's control behavior, a preview-tracking model was introduced based on the three-degree-of-freedom model, thus establishing a four-degree-of-freedom model.

[0341]

[0342] Using the aforementioned four-wheel steering prototype as the research object, this study analyzes the prototype's lateral motion, yaw motion, and roll motion. The transient response of the yaw rate at the original caster angle and the caster angle obtained by the algorithm is calculated. The time history of the ratio of the transient to the steady-state yaw rate is analyzed. (See [link to relevant documentation]). Figure 9 It can be seen that the active control method of the MacPherson strut steering wheel kingpin inclination angle adjustment mechanism of the present invention achieves the desired kingpin inclination angle. The yaw rate overshoot is significantly lower than that of the original kingpin caster angle, and the settling time is significantly shortened, proving that the kingpin caster angle algorithm is beneficial to improving vehicle driving stability.

[0343] Those skilled in the art will readily understand that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An active control method for adjusting the kingpin inclination angle of a MacPherson strut suspension, comprising a MacPherson strut suspension, characterized in that: It also includes one or more adjustment mechanisms; The adjustment mechanism includes a support (4), an adjustment motor (5), a gear and rack mechanism, and a guide mechanism; The support (4) is a U-shaped support; the adjusting motor (5) is fixedly installed on the base plate inside the support (4); The gear and rack mechanism includes a gear (6) and a rack (8); the gear (6) is fixed on the output shaft of the regulating motor (5) by spline engagement; the two ends of the rack (8) in the length direction are respectively fixed on the two side plates inside the support (4) by connecting rods; The guiding mechanism includes a guide bracket (9) and a guide shaft (10). The guide bracket (9) is a rectangular block with a guide hole in the middle. The guide shaft (10) is fitted into the guide hole of the guide bracket (9). The two ends of the guide shaft (10) are respectively fixed on the two side plates inside the support (4), and the guide shaft (10) is parallel to the rack (8). The guide bracket (9) is fixedly connected to the back of the rack (8) through a pair of upper mounting holes at the top; the guide bracket (9) is fixedly connected to the upper fulcrum of the damper (12) through the bottom; Its active control operation steps are as follows: (1) Establish a calculation model for wheel return torque. For the entire vehicle, the forward direction is taken as the positive x-axis, the rightward direction as the positive y-axis, and the upward direction as the positive z-axis; the wheel self-aligning torque consists of the following four parts: the self-aligning torque generated by the lateral force. Kingpin inclination angle The resulting restoring torque The restoring torque generated by the longitudinal force The restoring torque generated by the vehicle's own weight ; The main pin axis is the line connecting the center of the upper fulcrum of the damper and the center of the outer ball head of the lower swing arm. Since the adjustment mechanism exists, the main pin axis L should be the line connecting the center point of the back of the moving rack (8) and the center of the outer ball head of the lower swing arm (3). L is the kingpin axis; L1 is the projection of the kingpin axis L onto the XOZ plane; L2 is the projection of the kingpin axis onto the YOZ plane; the kingpin inclination angle... The angle between L1 and the Z-axis is the kingpin backslope angle; the kingpin inclination angle is... The angle between L2 and the Z-axis is the kingpin inclination angle. The formula for calculating the wheel return torque is as follows: ; In formula (17), To provide the restoring torque, The restoring torque generated by the lateral force, The self-correcting torque generated by the inward inclination of the main pin The restoring torque generated by the longitudinal force, The restoring torque generated by the vehicle's own weight; (2) Establish a calculation model for the positive resistance torque of the steering wheel. The formula for calculating the positive resistance torque of the steering wheel return is as follows: In formula (20), This represents the dynamic load coefficient of the axle, and is dimensionless. This represents the friction coefficient of the upper pivot kingpin bearing, which is dimensionless. This indicates the radius of the upper pivot kingpin bearing, in meters (m). This represents the coefficient of bearing friction between the steering knuckle and the lower control arm; it is dimensionless. This indicates the bearing radius between the steering knuckle and the lower control arm, in meters (m). This represents the road surface adhesion coefficient, which is dimensionless. The kingpin inclination angle is represented in degrees (°); r represents the wheel rolling radius, in units of... ; The frictional resistance torque experienced by the kingpin at the upper pivot bearing and the lower control arm and steering knuckle bearing is expressed in N·m. It is the sum of the frictional resistance torque of the steering transmission mechanism and the resistance torque when the steering gear reverses, in N·m; This represents the frictional torque between the road surface and the tire, expressed in N·m. It is the total vertical load on the steering wheel, in units of ; (3) Establish the calculation formula for active control of caster angle during vehicle operation. When the vehicle is moving, the steering wheels stop returning to center when the total return torque of the front wheels is balanced with the total return resistance torque. The formula for balancing the total return torque and the total return resistance torque is as follows: Based on formulas (17), (20), and (21), the calculation formula for active control of kingpin caster angle is as follows: In formula (22), The lateral force acting on the tire is expressed in N; r represents the wheel rolling radius, expressed in units of... ; Indicates the axle spacing, in units of ; The ideal kingpin inclination angle is obtained according to equation (22). The rotation direction and angle of the adjusting motor (5) in the adjusting mechanism are controlled. The horizontal displacement of the adjusting guide bracket (9) is adjusted through the gear and rack mechanism, so as to realize the corresponding adjustment of the kingpin axis L and finally realize the kingpin inclination angle. Active regulation; For two-wheel steering vehicles, the ideal caster angle value is calculated by treating the two steering wheels as a whole, following the steps above, so as to achieve active adjustment of the caster angle. For vehicles with four-wheel steering, calculate the ideal front caster angle as a whole using the two front steering wheels as a whole, and calculate the ideal rear caster angle as a whole using the two rear steering wheels as a whole. Based on the ideal front and rear caster angles, actively adjust the caster angles of the front and rear wheels respectively.

2. The active control method for the adjustment mechanism of the kingpin inclination angle of a MacPherson strut suspension according to claim 1, characterized in that: The top of the guide bracket (9) is provided with an upper protrusion, and a pair of upper mounting holes are provided on the upper protrusion. The bottom sides of the guide bracket (9) are respectively provided with lower protrusions, and lower mounting holes are provided on the lower protrusions.

3. The active control method according to claim 1, characterized in that: In step (1), the direction of vehicle movement is taken as the positive x-axis, the rightward direction of vehicle movement is taken as the positive y-axis, and the upward direction is taken as the positive z-axis. (1.1) Calculate the restoring torque generated by the lateral force. Righting moment Due to lateral force Total tire trail It is derived from product calculation; (1.1.1) Calculate the lateral force Lateral force The calculation formula is as follows: In formula (3): This represents the coefficient of sliding friction, which is dimensionless. Indicates tire camber stiffness ; This indicates the wheel camber angle, measured in rad. Representing the dimensionless sideslip angle: ,in This is the front wheel slip angle, in degrees. Tire slip angle Tire lateral stiffness at time, in units , This is the front wheel toe angle, in degrees; It is the total vertical load on the steering wheel : The formula for the vertical load on the first right tire is as follows: The formula for the vertical load on the first left tire is as follows: The vertical load on the right tire is expressed in units of... ; The vertical load on the left tire is expressed in units of... ; Indicates the total vehicle mass, in units of ; This represents the distance from the vehicle's center of gravity to the front axle, in units of... ; Indicates the height of the center of mass, in units of ; This indicates the distance between the two kingpin axles of the front wheel and the points where they intersect the ground, in units of... ; Indicates the axle spacing, in units of ; Represents the longitudinal acceleration of a vehicle, in units of ; This represents the lateral acceleration of a vehicle, measured in units of... ; (1.1.2) Calculate the total tire drag moment The total tire trail consists of two parts: the tire trail and the caster angle and the tire contact patch. The formula for calculating total tire trail is as follows: In formula (6): This represents the total tire drag, in units of... ; This indicates the tire trail distance, in units of... ; Indicates the kingpin inclination angle, in units of ; r represents the wheel rolling radius, in units of ; Indicates the length of the tire contact patch. The unit is ; D is the nominal outer diameter of the tire. It is the radial deformation of the axle under load, in units of ; b is the tire width, in units of... C and Q are coefficients. , , p is the tire pressure, measured in units of... ; (1.1.3) Calculate the corrective torque generated by the lateral force. The restoring torque generated by the lateral force is the product of the lateral force and the component of the total tire drag torque in the direction perpendicular to the lateral force. The total restoring torque generated by the lateral forces of the left and right wheels can be obtained according to formulas (3) and (6). Formula (7) is as follows: because , Substituting formula (6) into formula (7), we obtain formula (8) as follows: Formula (8) applies to vehicles with two-wheel steering; For vehicles with four-wheel steering, the return torque is calculated separately for the two front steering wheels as a whole and the two rear steering wheels as a whole. The solution for the front steering wheels of a four-wheel steering vehicle is the same as in step (1.1); the solution for the rear steering wheels of a four-wheel steering vehicle differs from step (1.1) in that the total vertical load on the steering wheels described in step (1.1.1) is... Total vertical load on the rear steering wheel , The vertical load on the right rear tire is expressed in units of... ; The vertical load on the left rear tire is expressed in units of... ; At this point, formulas (4) and (5) in step (1.1.1) above should be calculated according to formulas (41) and (51) below: The formula for the vertical load of the second right tire (41) is as follows: （41） The formula for the vertical load of the second left tire (51) is as follows: （51） In formulas (41) and (51), Indicates the total vehicle mass, in units of ; This represents the distance from the vehicle's center of gravity to the front axle, in units of... ; Indicates the height of the center of mass, in units of ; This indicates the distance between the two kingpin axles of the front wheel and the points where they intersect the ground, in units of... ; Indicates the axle spacing, in units of ; Represents the longitudinal acceleration of a vehicle, in units of ; This represents the lateral acceleration of a vehicle, measured in units of... ; The other operations for solving the rear steering wheel of a four-wheel steering vehicle are the same as in step (1.1). (1.2) Calculate the restoring torque generated by the kingpin inclination. According to the Ackermann ideal relation, during vehicle cornering, due to the presence of toe angle, the steering angles of the left and right steering wheels are not equal, thus causing a self-centering torque. Calculations need to be made separately for the left and right steering wheels; Righting moment It is the kingpin inclination angle of the left steering wheel. The resulting restoring torque and right steering wheel kingpin inclination angle The resulting restoring torque The sum, as shown in formula (11), is as follows: Assuming the vehicle turns left, the left steering wheel angle is... The unit is °; right steering wheel angle. The unit is °; Steering wheel angle; The return torque generated by the kingpin inclination angle of the right steering wheel The formula is as follows: The return torque generated by the kingpin inclination angle of the left steering wheel The formula is as follows: In formulas (9) and (10), This indicates the distance from the steering knuckle joint to the front wheel mounting center plane, in meters (m). Indicates the kingpin inclination angle, in degrees; The vertical load on the right tire is expressed in units of... ; The vertical load on the right tire is expressed in units of... ; Formula (11) applies to vehicles with two-wheel steering; For vehicles with four-wheel steering, the return torque is calculated by treating the two front steering wheels as a single unit and the two rear steering wheels as a single unit. The calculation of the front steering wheel as a whole is the same as in step (1.2); the calculation of the rear steering wheel as a whole differs from step (1.2) in that the calculation in step (1.2) is different. The total vertical load on the steering wheels is the total vertical load on the rear steering wheels. ; (1.3) Calculate the restoring torque generated by the longitudinal force. The self-aligning torques are in opposite directions. Due to the toe angle, the steering angles of the left and right steering wheels are unequal during vehicle turning, resulting in unequal magnitudes of the self-aligning torques generated by the longitudinal forces on the left and right sides. Therefore, it is necessary to solve for the self-aligning torques generated by the left and right steering wheels separately and take the difference. Assuming the vehicle is turning left... It is determined by the friction between the left front tire and the ground and the kingpin offset. The product of its vertical components and the friction between the right front tire and the ground and the kingpin offset. The difference of the products of its vertical components, the restoring torque. Formula (14) is as follows: In formula (14), the left steering wheel angle The unit is °; right steering wheel angle. The unit is °; Formula (14) applies to vehicles with two-wheel steering; For vehicles with four-wheel steering, the return torque is calculated by treating the two front steering wheels as a single unit and the two rear steering wheels as a single unit. The calculation of the front steering wheel as a whole is the same as in step (1.3); the calculation of the rear steering wheel as a whole differs from step (1.3) in that the total vertical load of the steering wheel in step (1.3) is... Total vertical load on the rear steering wheel ; (1.4) Calculate the restoring torque generated by the vehicle's own weight. The restoring torque generated by the vehicle's own weight Formula (16) is as follows: In formula (16), The vertical force on the tire contact patch is shifted towards the wheel centerline and decomposed into two directions: parallel to the steering knuckle axis and perpendicular to the steering knuckle axis. , The force perpendicular to the kingpin axis is Considering the kingpin caster angle Then the force perpendicular to the kingpin axis is Due to the kingpin caster angle Usually smaller, therefore The force perpendicular to the kingpin axis is ; Lever arm from the force dividing point to the kingpin axis for: Formula (15) applies to vehicles with two-wheel steering; For vehicles with four-wheel steering, the return torque is calculated by treating the two front steering wheels as a single unit and the two rear steering wheels as a single unit. The calculation of the front steering wheel as a whole is the same as in step (1.4); the calculation of the rear steering wheel as a whole differs from that in step (1.4) in that the total vertical load of the steering wheel in step (1.4) is... Total vertical load on the rear steering wheel .

4. The active control method according to claim 1, characterized in that: In step (2), the return resistance torque It consists of three parts: the frictional torque experienced by the kingpin at the upper pivot bearing and the lower control arm at the steering knuckle bearing during rotation. The sum of the frictional resistance torque of the steering transmission mechanism and the resistance torque when the steering gear reverses. Friction torque between the road surface and the tire ; (2.1) Calculate the frictional resistance torque Frictional resistance torque The force on the kingpin at the upper pivot bearing and the lower control arm and steering knuckle bearing is given by formula (18) as follows; In formula (18): This represents the dynamic load coefficient of the axle, and is dimensionless. This represents the friction coefficient of the upper pivot kingpin bearing, which is dimensionless. This indicates the radius of the upper pivot kingpin bearing, in meters (m). This represents the coefficient of bearing friction between the steering knuckle and the lower control arm; it is dimensionless. This indicates the bearing radius between the steering knuckle and the lower control arm, in meters (m). Indicates the kingpin inclination angle, in degrees; According to the force analysis, the force at the upper pivot point of the MacPherson strut suspension is... The force at the bearing between the steering knuckle and the lower control arm is ; Formula (18) applies to vehicles with two-wheel steering; For vehicles with four-wheel steering, the frictional resistance torque is calculated by treating the two front steering wheels as a single unit and the two rear steering wheels as a single unit. The calculation of the front steering wheel as a whole is the same as in step (2.1); the calculation of the rear steering wheel as a whole differs from that in step (2.1) in that the calculation in step (2.1) is different. The total vertical load on the steering wheels is the total vertical load on the rear steering wheels. ; (2.2) Calculate the sum of resistance torques The sum of the frictional resistance torque of the steering transmission mechanism and the resistance torque when the steering gear reverses. Measured based on actual vehicle configuration; (2.3) Calculate the frictional torque between the road surface and the tire. Frictional torque between the road surface and the tire The formula (19) is obtained by multiplying the supporting force between the vehicle tire and the ground by the road surface adhesion coefficient: In formula (19), This represents the road surface adhesion coefficient, which is dimensionless. r represents the wheel rolling radius, in units of r ; Formula (19) applies to vehicles with two-wheel steering; For vehicles with four-wheel steering, the friction torque is calculated by treating the two front steering wheels as a single unit and the two rear steering wheels as a single unit. The calculation of the front steering wheel as a whole is the same as in step (2.3); the calculation of the rear steering wheel as a whole differs from that in step (2.3) in that the total vertical load of the steering wheel in step (2.3) is... Total vertical load on the rear steering wheel ; (2.4) Calculate the positive resistance torque M of the steering wheel. f From equations (18) and (19), the positive resistance torque M of the steering wheel can be obtained. f Formula (20) is as follows: Formula (20) is the calculation model for the positive resistance torque of the steering wheel.

5. The active control method according to claim 1, characterized in that: In step (3), When the front wheels turn, the tires begin to straighten. With the tire slip angle The decrease in lateral force generates a restoring torque. It also gradually decreases, while the restoring torque generated by the axle position energy is... The sum also varies with the steering wheel angle. The total return torque of the front wheels decreases as the total return resistance torque decreases until it balances with the total return resistance torque, at which point the steering wheels stop returning to center, resulting in the balance formula (21).

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