Rear wheel steering follow-up control method and device

Abstract

The invention discloses a rear wheel steering follow-up control method and device. And obtaining a boundary value first vehicle speed of the low-speed-section vehicle speed and the medium-speed-section vehicle speed according to the calibration parameters. According to the corresponding relation between the steady-state yaw velocity gain and the vehicle speed, the boundary value second vehicle speed of the medium-speed-section vehicle speed and the high-speed-section vehicle speed is obtained. And according to the calibration curve and the front wheel rotation angle, the first rear wheel follow-up steering rotation angle is obtained as the low-speed-section rear wheel rotation angle. And acquiring a second rear wheel follow-up steering angle as a high-speed section rear wheel steering angle according to the ratio of the high-speed section rear wheel to the front wheel steering angle and the front wheel steering angle. And the sum of the first rear wheel follow-up steering angle and the second rear wheel follow-up steering angle serves as the middle-speed section rear wheel steering angle. According to the method, the vehicle speed is divided into three speed sections, the rear wheel turning angle is controlled through different strategies, the intention of a driver is recognized according to the vehicle speed, the front wheel turning angle and the like, the rear wheel turning angle is calculated through a calibration value, a theoretical basis is provided, and meanwhile engineering practicability is high. And the calibration value is stable, the acquisition difficulty is low, and the calculation result robustness is high.

Description

Technical Field

[0001] The present application relates to the field of automobile technology, and in particular to a method and device for rear wheel steering follow-up control. Background Art

[0002] With the popularization and deepening of intelligent driving technology, the rear-wheel assisted steering function is also constantly upgraded. When the vehicle is in a low-speed driving area, the rear wheel turns in the opposite direction to the front wheel, reducing the turning radius, thereby improving the convenience of the vehicle in a small space or when turning around. When the vehicle is in a high-speed driving area, the rear wheels turn slightly in the opposite direction, which is not as sensitive as in a low-speed driving area, making the vehicle's steering movement easier to control and less likely to become unstable, thereby improving the vehicle's high-speed driving stability.

[0003] In the prior art, the rear wheel steering follow-up function mostly adopts a feedforward plus feedback control method, which only provides a theoretical basis and has low engineering practicality. Moreover, these physical theories contain too many parameters, which are complicated to obtain and are easily affected by external interference or vehicle factors. Therefore, the present invention provides a rear wheel steering follow-up control method with clear physical meaning and engineering implementation value and high robustness. Summary of the invention

[0004] Based on the above problems, the present application provides a method and device for rear wheel steering follow-up control, which has clear physical meaning and engineering implementation value, and controls the rear wheel steering follow-up function with high robustness.

[0005] The present application discloses a method for rear wheel steering follow-up control, the method comprising:

[0006] According to the maximum lateral acceleration limited by the tire adhesion limit, steering sensitivity, maximum rack displacement and lever arm, the boundary value between the low-speed segment speed and the medium-speed segment speed is obtained as the first vehicle speed;

[0007] According to the change process of the steady-state yaw rate gain along with the vehicle speed, the vehicle speed corresponding to when the steady-state yaw rate gain reaches the maximum value is obtained, and the vehicle speed is used as the dividing value between the medium speed segment and the high speed segment as the second vehicle speed;

[0008] When the vehicle speed is lower than the first vehicle speed, according to the ratio curve of the rear wheel and front wheel turning angles in the low speed section and the front wheel turning angle, a first rear wheel follow-up steering angle is obtained as the rear wheel turning angle in the low speed section;

[0009] When the vehicle speed is higher than the second vehicle speed, according to the ratio of the rear wheel to the front wheel turning angle in the high speed section and the front wheel turning angle, a second rear wheel follow-up steering angle is obtained as the rear wheel turning angle in the high speed section;

[0010] When the vehicle speed is between the first vehicle speed and the second vehicle speed, the sum of the first rear wheel follow-up steering angle and the second rear wheel follow-up steering angle is used as the rear wheel steering angle in the middle speed section.

[0011] Optionally, the dividing value between the low-speed segment vehicle speed and the medium-speed segment vehicle speed is obtained as the first vehicle speed according to the maximum lateral acceleration limited by the tire adhesion limit, the steering sensitivity, the maximum rack displacement for forward rotation, and the lever arm, including:

[0012] Obtaining a ratio of the maximum lateral acceleration limited by the tire adhesion limit to the steering sensitivity; there is a corresponding relationship between the steering sensitivity and the current vehicle speed;

[0013] Obtaining the ratio of the maximum rack displacement of the forward rotation to the lever arm;

[0014] When the ratio of the maximum lateral acceleration limited by the tire adhesion limit to the steering sensitivity is equal to the ratio of the forward maximum rack displacement to the lever arm, the current vehicle speed is obtained as the first vehicle speed.

[0015] Optionally, the obtaining, according to the variation process of the steady-state yaw rate gain with the vehicle speed, a vehicle speed corresponding to when the steady-state yaw rate gain reaches a maximum value, and taking the second vehicle speed as a dividing value between the medium-speed segment vehicle speed and the high-speed segment vehicle speed, comprises:

[0016] When the steady-state yaw rate gain reaches a maximum value, the second vehicle speed is a negative exponential power of a stability factor; and the stability factor is related to the steady-state yaw rate gain.

[0017] Optionally, obtaining the first rear wheel follow-up steering angle according to the ratio curve of the rear wheel and front wheel steering angles in the low speed section and the front wheel steering angle includes:

[0018] Collect steering wheel angle;

[0019] Obtaining the quotient of the steering wheel angle and the front wheel steering transmission ratio as the front wheel angle;

[0020] The product of the value in the ratio curve corresponding to the current vehicle speed and the front wheel turning angle is obtained as the first rear wheel follow-up steering angle.

[0021] Optionally, obtaining a second rear wheel follow-up steering angle according to a ratio of a rear wheel angle to a front wheel angle in a high speed section and the front wheel angle includes:

[0022] Obtain the ratio of the rear wheel turning angle to the front wheel turning angle in the high-speed section;

[0023] The product of the ratio and the front wheel turning angle is obtained as the second rear wheel following steering angle.

[0024] Optionally, obtaining the ratio of the rear wheel turning angle to the front wheel turning angle in the high speed section includes:

[0025] The ratio is obtained according to the first vehicle speed, the second vehicle speed and the current vehicle speed.

[0026] Optionally, after obtaining the low-speed rear wheel angle, the low-speed rear wheel angle or the low-speed rear wheel angle, the method further includes:

[0027] Obtain the calibrated rear wheel steering following gain;

[0028] Obtaining a limit value of the rear wheel turning angle according to the maximum lateral acceleration limited by the tire adhesion limit, the steering sensitivity, the rear turn maximum rack displacement and the lever arm;

[0029] The obtained rear wheel turning angle at low speed section, rear wheel turning angle at low speed section or rear wheel turning angle at low speed section, rear wheel steering following gain, and limit value are taken as an output value set;

[0030] The smallest value in the output value set is output to control the rear wheels of the vehicle.

[0031] Based on the above-mentioned method for rear wheel steering follow-up control, the present application also discloses a device for rear wheel steering follow-up control, including: a first vehicle speed acquisition unit, a second vehicle speed acquisition unit, a low speed zone turning angle acquisition unit, a high speed zone turning angle acquisition unit and a medium speed zone turning angle acquisition unit;

[0032] The first vehicle speed acquisition unit is used to obtain the boundary value between the low speed segment vehicle speed and the medium speed segment vehicle speed as the first vehicle speed according to the maximum lateral acceleration limited by the tire adhesion limit, the steering sensitivity, the maximum rack displacement and the lever arm for forward rotation;

[0033] The second vehicle speed acquisition unit is used to acquire the vehicle speed corresponding to when the steady-state yaw rate gain reaches a maximum value according to the change process of the steady-state yaw rate gain with the vehicle speed, and use the vehicle speed as the dividing value between the medium speed segment and the high speed segment as the second vehicle speed;

[0034] The low-speed zone turning angle acquisition unit is used to acquire a first rear wheel follow-up steering angle as the low-speed zone rear wheel turning angle according to the ratio curve of the rear wheel and front wheel turning angles in the low-speed zone and the front wheel turning angle when the vehicle speed is lower than the first vehicle speed;

[0035] The high-speed zone turning angle acquisition unit is used to acquire a second rear wheel follow-up steering angle as the high-speed section rear wheel turning angle according to the ratio of the rear wheel turning angle to the front wheel turning angle in the high-speed section and the front wheel turning angle when the vehicle speed is higher than the second vehicle speed;

[0036] The medium speed area steering angle acquisition unit is used to use the sum of the first rear wheel follow-up steering angle and the second rear wheel follow-up steering angle as the medium speed section rear wheel steering angle when the vehicle speed is between the first vehicle speed and the second vehicle speed.

[0037] Optionally, the first vehicle speed obtaining unit includes:

[0038] A first ratio acquisition subunit is used to acquire a ratio of the maximum lateral acceleration limited by the tire adhesion limit to the steering sensitivity; there is a corresponding relationship between the steering sensitivity and the current vehicle speed;

[0039] A second ratio acquisition subunit, used to acquire the ratio of the maximum rack displacement of the forward rotation to the lever arm;

[0040] The first vehicle speed acquisition subunit is used to acquire the current vehicle speed as the first vehicle speed when the ratio of the maximum lateral acceleration limited by the tire adhesion limit to the steering sensitivity is equal to the ratio of the forward maximum rack displacement to the lever arm.

[0041] Optionally, the second vehicle speed obtaining unit includes:

[0042] A relationship acquisition subunit is used for, when the steady-state yaw rate gain reaches a maximum value, the second vehicle speed is a negative exponential power of a stability factor; and the stability factor is related to the steady-state yaw rate gain.

[0043] Optionally, the low-speed zone turning angle acquisition unit includes:

[0044] A steering wheel acquisition subunit, used to acquire the steering wheel angle;

[0045] A front wheel angle acquisition subunit, used for acquiring the quotient of the steering wheel angle and the front wheel steering transmission ratio as the front wheel angle;

[0046] The first turning angle obtaining subunit is used to obtain the product of the value in the ratio curve corresponding to the current vehicle speed and the front wheel turning angle as the first rear wheel follow-up steering angle.

[0047] Optionally, the high-speed zone corner acquisition unit includes:

[0048] A turning angle ratio acquisition subunit is used to acquire the ratio of the turning angles of the rear wheels to the front wheels in the high-speed section;

[0049] The second turning angle obtaining subunit is used to obtain the product of the ratio and the front wheel turning angle as the second rear wheel follow-up steering angle.

[0050] Optionally, the turning angle ratio acquisition subunit is used to:

[0051] The ratio is obtained according to the first vehicle speed, the second vehicle speed and the current vehicle speed.

[0052] Optionally, the device further comprises:

[0053] A gain acquisition unit, used for acquiring a calibrated rear wheel steering following gain;

[0054] a limit value acquisition unit, configured to acquire a limit value of the rear wheel turning angle according to the maximum lateral acceleration limited by the tire adhesion limit, the steering sensitivity, the rear turn maximum rack displacement and the lever arm;

[0055] an output value set acquisition unit, configured to use the acquired low-speed rear wheel angle, low-speed rear wheel angle or low-speed rear wheel angle, the rear wheel steering following gain, and the limit value as an output value set;

[0056] A rear wheel control unit is used to output the smallest value in the output value set to control the rear wheels of the vehicle.

[0057] The present application discloses a method and device for rear wheel steering follow-up control. A first vehicle speed, which is a dividing value between a low speed segment and a medium speed segment, is obtained according to calibration parameters. A second vehicle speed, which is a dividing value between a medium speed segment and a high speed segment, is obtained according to the correspondence between a steady-state yaw rate gain and the vehicle speed. According to a calibration curve and a front wheel turning angle, a first rear wheel follow-up steering angle is obtained as a rear wheel turning angle in a low speed segment. According to a ratio of a rear wheel turning angle to a front wheel turning angle in a high speed segment and the front wheel turning angle, a second rear wheel follow-up steering angle is obtained as a rear wheel turning angle in a high speed segment. The sum of the first rear wheel follow-up steering angle and the second rear wheel follow-up steering angle is taken as the rear wheel turning angle in a medium speed segment. The present method divides the vehicle speed into three speed segments, controls the rear wheel turning angle by different strategies respectively, identifies the driver's intention according to the vehicle speed, the front wheel turning angle, etc., and calculates the rear wheel turning angle by calibration values, which not only provides a theoretical basis but also has strong engineering practicality. Moreover, the calibration values ​​are stable and easy to obtain, which makes the calculation results highly robust, such as not changing with vehicle load. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0059] Figure 1 A schematic flow chart of a method for rear wheel steering follow-up control disclosed in an embodiment of the present application;

[0060] Figure 2 A schematic diagram of changes in the first rear wheel follow-up steering angle and the second rear wheel follow-up steering angle in each vehicle speed range disclosed in the embodiment of the present application;

[0061] Figure 3 This is a schematic structural diagram of a rear wheel steering follow-up control device disclosed in an embodiment of the present application. DETAILED DESCRIPTION

[0062] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0063] Embodiment 1: This application discloses a method for rear wheel steering follow-up control.

[0064] For details, please refer to Figure 1 A rear wheel steering follow-up control method disclosed in this embodiment includes the following steps:

[0065] Step 101: According to the maximum lateral acceleration limited by the tire adhesion limit, the steering sensitivity, the maximum rack displacement and the lever arm for forward turning, a boundary value between the low-speed segment vehicle speed and the medium-speed segment vehicle speed is obtained as the first vehicle speed.

[0066] In the method described in this embodiment, the front wheel angle data can be obtained according to the steering wheel data and the front wheel steering transmission ratio. Specifically, the front wheel angle can be obtained by dividing the steering wheel angle collected by the sensor by the front wheel steering transmission ratio, or the front wheel angular velocity can be obtained by dividing the steering wheel angular velocity collected by the sensor by the front wheel steering transmission ratio.

[0067] In the method described in this embodiment, the ratio of the maximum lateral acceleration limited by the tire adhesion limit to the steering sensitivity is obtained, and there is a corresponding relationship between the steering sensitivity and the current vehicle speed. Then the ratio of the maximum rack displacement and the lever arm for the forward turn is obtained. Then the front wheel steering angle limit is calculated by the following formula:

[0068]

[0069] In the formula, δ max is the front wheel turning angle limit, ay max is the maximum lateral acceleration limited by the tire adhesion limit, SS ch is the steering sensitivity, s rack_max f is the maximum rack displacement during forward rotation, and Lever is the lever arm.

[0070] In the method described in this embodiment, when the ratio of the maximum lateral acceleration limited by the tire adhesion limit to the steering sensitivity is equal to the ratio of the maximum rack displacement to the lever arm during forward rotation, the current vehicle speed is obtained as the first vehicle speed. That is, when v is greater than the first vehicle speed v 0 When, ay max With SS ch The ratio is greater than s rack_maxThe ratio of f to Lever. When v is less than v 0 When, ay max With SS ch The ratio is less than s rack_max The ratio of f to Lever. Therefore, when ay max With SS ch The ratio is equal to s rack_max When the ratio of f to Lever is used, the SS ch The corresponding relationship with v is v 0 That is, when the ratio of the maximum lateral acceleration limited by the tire adhesion limit to the steering sensitivity is equal to the ratio of the maximum rack displacement to the lever arm during forward rotation, the current vehicle speed is obtained as the first vehicle speed.

[0071] Step 102: According to the variation process of the steady-state yaw rate gain with the vehicle speed, the vehicle speed corresponding to when the steady-state yaw rate gain reaches the maximum value is obtained, and the boundary value between the medium speed segment and the high speed segment is used as the second vehicle speed.

[0072] In the method described in this embodiment, the steady-state yaw rate gain varies with the vehicle speed. When the steady-state yaw rate gain reaches a maximum value, the relationship between the stability factor associated with the steady-state yaw rate gain and the second vehicle speed is:

[0073]

[0074] Wherein, k is the stability factor.

[0075] Step 103: When the vehicle speed is lower than the first vehicle speed, a first rear wheel follow-up steering angle is obtained according to a ratio curve of rear wheel and front wheel steering angles in a low-speed section and the front wheel steering angle as the rear wheel steering angle in the low-speed section.

[0076] In the method described in this embodiment, the product of the value in the ratio curve corresponding to the current vehicle speed and the front wheel turning angle is obtained as the first rear wheel follow-up steering angle. The ratio curve is a calibration curve, and the corresponding ratio of the rear wheel to the front wheel turning angle can be found in the ratio curve according to the current vehicle speed, and the calculated front wheel turning angle is multiplied by the ratio to obtain the first rear wheel follow-up steering angle.

[0077] Step 104: When the vehicle speed is higher than the second vehicle speed, a second rear wheel follow-up steering angle is obtained according to the ratio of the rear wheel angle to the front wheel angle in the high speed section and the front wheel angle as the rear wheel angle in the high speed section.

[0078] In the method described in this embodiment, the ratio of the rear wheel turning angle to the front wheel turning angle in the high speed section is obtained according to the following formula:

[0079]

[0080] In the formula, L is the ratio, V0 is the first vehicle speed, V 1 is the second vehicle speed, and V is the current vehicle speed.

[0081] In the method described in this embodiment, the ratio of the rear wheel and front wheel turning angles in the high-speed section is multiplied by the front wheel turning angle to obtain the second rear wheel follow-up steering angle.

[0082] Step 105: When the vehicle speed is between the first vehicle speed and the second vehicle speed, the sum of the first rear wheel follow-up steering angle and the second rear wheel follow-up steering angle is used as the rear wheel angle in the medium speed section.

[0083] In the method described in this embodiment, a calibrated rear wheel steering following gain is obtained, which includes the gain of the rear wheel steering following the front wheel turning angle, the gain of the rear wheel steering following the front wheel turning angle speed, and the gain of the rear wheel steering following the front wheel turning angle.

[0084] In the method described in this embodiment, the limit of the rear wheel steering angle is obtained according to the maximum lateral acceleration limited by the tire adhesion limit, the steering sensitivity, the maximum rack displacement and the lever arm of the rear turn. The limit of the rear wheel steering angle is as follows:

[0085]

[0086] In the formula, δ rmax is the rear wheel turning angle limit, s rack_max r is the maximum rack displacement of the rear turn.

[0087] In the method described in this embodiment, the obtained rear wheel angle in the low speed section, the rear wheel angle in the medium speed section or the rear wheel angle in the high speed section, the rear wheel steering following gain, and the limit value are used as an output value set. The minimum value in the set is output to control the rear wheels of the vehicle.

[0088] As an optional method, the output value is:

[0089] δ rf =min(δ r *Gs*Gds*Gdb,δ rmax ) (5)

[0090] In the formula, δ rf is the output value, δ r is the rear wheel steering angle obtained from step 103 to step 105, Gs is the gain of the rear wheel steering with the front wheel steering angle, Gds is the gain of the rear wheel steering with the front wheel steering angle speed, and Gdb is the dead zone of the rear wheel steering with the front wheel steering angle.

[0091] The method described in this embodiment divides the vehicle speed into three speed sections, controls the rear wheel steering angle through different strategies respectively, identifies the driver's intention according to the vehicle speed, front wheel steering angle, etc., and calculates the rear wheel steering angle through calibration values, which not only provides a theoretical basis but also has strong engineering practicality. Moreover, the calibration values ​​in this method are stable and can be set, and are easy to obtain, so that changes in vehicle status (such as load) will not affect the calculation process and accuracy of the rear wheel steering follow-up function, and are robust to external interference. At the same time, this method takes into account safety limits and can directly introduce specific executable quantification methods, which has great engineering application value. In addition, this method does not require additional sensors for rear-wheel steering, nor does it require feedback on vehicle status quantities.

[0092] Figure 2 Schematic diagram of the change of the first rear wheel follow-up steering angle and the second rear wheel follow-up steering angle in each vehicle speed range disclosed in the embodiment of the present application. Figure 2 As shown:

[0093] The rear wheel steering angle changes with the vehicle speed. 0 When the vehicle speed is higher than v, the second rear wheel follow-up steering angle is set to 0, and only the first rear wheel follow-up steering angle is obtained as the rear wheel follow-up steering angle in the low-speed zone. 1 When the vehicle speed is v, the first rear wheel follow-up steering angle is set to 0, and only the second rear wheel follow-up steering angle is obtained as the rear wheel follow-up steering angle in the high-speed zone. 0 and v 1 When the speed is between 0 and 1, the calculated first rear wheel following steering angle and the calculated second rear wheel following steering angle are added together, and the obtained value is used as the rear wheel following steering angle in the medium speed zone.

[0094] Based on the method for rear wheel steering follow-up control disclosed in the above embodiment, this embodiment correspondingly discloses a device for rear wheel steering follow-up control. Figure 3 The rear wheel steering follow-up control device comprises: a first vehicle speed acquisition unit 301, a second vehicle speed acquisition unit 302, a low speed zone turning angle acquisition unit 303, a high speed zone turning angle acquisition unit 304 and a medium speed zone turning angle acquisition unit 305;

[0095] The first vehicle speed acquisition unit 301 is used to obtain the boundary value between the low speed segment vehicle speed and the medium speed segment vehicle speed as the first vehicle speed according to the maximum lateral acceleration limited by the tire adhesion limit, the steering sensitivity, the maximum rack displacement and the lever arm of the forward turn;

[0096] The second vehicle speed acquisition unit 302 is used to acquire the vehicle speed corresponding to when the steady-state yaw rate gain reaches a maximum value according to the change process of the steady-state yaw rate gain with the vehicle speed, and use the boundary value between the medium speed segment and the high speed segment as the second vehicle speed;

[0097] The low-speed zone turning angle acquisition unit 303 is used to acquire a first rear wheel following steering angle as the low-speed rear wheel turning angle according to the ratio curve of the rear wheel and front wheel turning angles in the low-speed section and the front wheel turning angle when the vehicle speed is lower than the first vehicle speed;

[0098] The high-speed zone turning angle acquisition unit 304 is used to acquire a second rear wheel following steering angle as the high-speed section rear wheel turning angle according to the ratio of the rear wheel turning angle to the front wheel turning angle in the high-speed section and the front wheel turning angle when the vehicle speed is higher than the second vehicle speed;

[0099] The medium speed zone steering angle acquisition unit 305 is used to take the sum of the first rear wheel follow-up steering angle and the second rear wheel follow-up steering angle as the medium speed section rear wheel steering angle when the vehicle speed is between the first vehicle speed and the second vehicle speed.

[0100] Optionally, the first vehicle speed obtaining unit 301 includes:

[0101] A first ratio acquisition subunit is used to acquire a ratio of the maximum lateral acceleration limited by the tire adhesion limit to the steering sensitivity; there is a corresponding relationship between the steering sensitivity and the current vehicle speed;

[0102] A second ratio acquisition subunit is used to acquire the ratio of the maximum rack displacement of the forward rotation to the lever arm;

[0103] The first vehicle speed acquisition subunit is used to acquire the current vehicle speed as the first vehicle speed when the ratio of the maximum lateral acceleration limited by the tire adhesion limit to the steering sensitivity is equal to the ratio of the forward maximum rack displacement to the lever arm.

[0104] Optionally, the second vehicle speed obtaining unit 302 includes:

[0105] A relationship acquisition subunit is used for, when the steady-state yaw rate gain reaches a maximum value, the second vehicle speed is a negative exponential power of a stability factor; and the stability factor is related to the steady-state yaw rate gain.

[0106] Optionally, the low-speed zone turning angle acquisition unit 303 includes:

[0107] A steering wheel acquisition subunit, used to acquire the steering wheel angle;

[0108] A front wheel angle acquisition subunit, used to acquire the quotient of the steering wheel angle and the front wheel steering transmission ratio as the front wheel angle;

[0109] The first turning angle obtaining subunit is used to obtain the product of the value in the ratio curve corresponding to the current vehicle speed and the front wheel turning angle as the first rear wheel follow-up steering angle.

[0110] Optionally, the high-speed zone corner acquisition unit 304 includes:

[0111] A turning angle ratio acquisition subunit is used to acquire the ratio of the turning angles of the rear wheels to the front wheels in the high-speed section;

[0112] The second turning angle obtaining subunit is used to obtain the product of the ratio and the front wheel turning angle as the second rear wheel follow-up steering angle.

[0113] Optionally, the turning angle ratio acquisition subunit is used to:

[0114] The ratio is obtained according to the first vehicle speed, the second vehicle speed and the current vehicle speed.

[0115] Optionally, the device further comprises:

[0116] A gain acquisition unit, used for acquiring a calibrated rear wheel steering following gain;

[0117] a limit value acquisition unit, configured to acquire a limit value of the rear wheel turning angle according to the maximum lateral acceleration limited by the tire adhesion limit, the steering sensitivity, the rear turn maximum rack displacement and the lever arm;

[0118] an output value set acquisition unit, configured to use the acquired low-speed rear wheel angle, low-speed rear wheel angle or low-speed rear wheel angle, the rear wheel steering following gain, and the limit value as an output value set;

[0119] A rear wheel control unit is used to output the smallest value in the output value set to control the rear wheels of the vehicle.

[0120] The embodiments in this specification are described in a progressive manner. As for the devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple, and the relevant parts can be referred to the description of the methods.

[0121] It should also be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0122] The steps of the method or algorithm described in conjunction with the embodiments disclosed herein may be implemented directly using hardware, a software module executed by a processor, or a combination of the two. The software module may be placed in a random access memory (RAM), a memory, a read-only memory (ROM), an electrically programmable ROM, an electrically erasable programmable ROM, a register, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art.

[0123] The features described in the embodiments of this specification can be replaced or combined with each other, so that professional and technical personnel in this field can implement or use the present application.

[0124] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for rear wheel steering follow-up control, It is characterized in that include: According to the maximum lateral acceleration limited by the tire adhesion limit, steering sensitivity, maximum rack displacement and lever arm, the boundary value between the low-speed segment speed and the medium-speed segment speed is obtained as the first vehicle speed; According to the change process of the steady-state yaw rate gain along with the vehicle speed, the vehicle speed corresponding to when the steady-state yaw rate gain reaches the maximum value is obtained, and the vehicle speed is used as the dividing value between the medium speed segment and the high speed segment as the second vehicle speed; When the vehicle speed is lower than the first vehicle speed, according to the ratio curve of the rear wheel and front wheel turning angles in the low speed section and the front wheel turning angle, a first rear wheel follow-up steering angle is obtained as the rear wheel turning angle in the low speed section; When the vehicle speed is higher than the second vehicle speed, according to the ratio of the rear wheel to the front wheel turning angle in the high speed section and the front wheel turning angle, a second rear wheel follow-up steering angle is obtained as the rear wheel turning angle in the high speed section; When the vehicle speed is between the first vehicle speed and the second vehicle speed, the sum of the first rear wheel follow-up steering angle and the second rear wheel follow-up steering angle is used as the rear wheel steering angle in the middle speed section.

2. The method according to claim 1, It is characterized in that The dividing value between the low-speed segment speed and the medium-speed segment speed is obtained as the first vehicle speed according to the maximum lateral acceleration limited by the tire adhesion limit, the steering sensitivity, the maximum rack displacement and the lever arm for forward rotation, including: Obtaining a ratio of the maximum lateral acceleration limited by the tire adhesion limit to the steering sensitivity; there is a corresponding relationship between the steering sensitivity and the current vehicle speed; Obtaining the ratio of the maximum rack displacement of the forward rotation to the lever arm; When the ratio of the maximum lateral acceleration limited by the tire adhesion limit to the steering sensitivity is equal to the ratio of the forward maximum rack displacement to the lever arm, the current vehicle speed is obtained as the first vehicle speed.

3. The method according to claim 1, It is characterized in that The step of obtaining the vehicle speed corresponding to when the steady-state yaw rate gain reaches a maximum value according to the change process of the steady-state yaw rate gain along with the vehicle speed, and taking the second vehicle speed as the dividing value between the medium-speed segment vehicle speed and the high-speed segment vehicle speed, comprises: When the steady-state yaw rate gain reaches a maximum value, the second vehicle speed is a negative exponential power of a stability factor; and the stability factor is related to the steady-state yaw rate gain.

4. The method according to claim 1, It is characterized in that The step of obtaining a first rear wheel follow-up steering angle according to a ratio curve of rear wheel and front wheel steering angles in a low speed section and the front wheel steering angle comprises: Collect steering wheel angle; Obtaining the quotient of the steering wheel angle and the front wheel steering transmission ratio as the front wheel angle; The product of the value in the ratio curve corresponding to the current vehicle speed and the front wheel turning angle is obtained as the first rear wheel follow-up steering angle.

5. The method according to claim 4, It is characterized in that The obtaining of a second rear wheel follow-up steering angle according to the ratio of the rear wheel to the front wheel steering angle in the high speed section and the front wheel steering angle comprises: Obtain the ratio of the rear wheel turning angle to the front wheel turning angle in the high-speed section; The product of the ratio and the front wheel turning angle is obtained as the second rear wheel following steering angle.

6. The method according to claim 5, It is characterized in that The method of obtaining the ratio of the rear wheel turning angle to the front wheel turning angle in the high speed section includes: The ratio is obtained according to the first vehicle speed, the second vehicle speed and the current vehicle speed.

7. The method according to any one of claims 1 to 6, It is characterized in that After obtaining the low-speed rear wheel angle, the low-speed rear wheel angle or the low-speed rear wheel angle, the method further includes: Obtain the calibrated rear wheel steering following gain; Obtaining a limit value of the rear wheel turning angle according to the maximum lateral acceleration limited by the tire adhesion limit, the steering sensitivity, the rear turn maximum rack displacement and the lever arm; The obtained rear wheel turning angle at low speed section, rear wheel turning angle at low speed section or rear wheel turning angle at low speed section, rear wheel steering following gain, and limit value are taken as an output value set; The smallest value in the output value set is output to control the rear wheels of the vehicle.

8. A device for rear wheel steering follow-up control, It is characterized in that include: a first vehicle speed acquisition unit, a second vehicle speed acquisition unit, a low-speed zone turning angle acquisition unit, a high-speed zone turning angle acquisition unit, and a medium-speed zone turning angle acquisition unit; The first vehicle speed acquisition unit is used to obtain the boundary value between the low speed segment vehicle speed and the medium speed segment vehicle speed as the first vehicle speed according to the maximum lateral acceleration limited by the tire adhesion limit, the steering sensitivity, the maximum rack displacement and the lever arm for forward rotation; The second vehicle speed acquisition unit is used to acquire the vehicle speed corresponding to when the steady-state yaw rate gain reaches a maximum value according to the change process of the steady-state yaw rate gain with the vehicle speed, and use the vehicle speed as the dividing value between the medium speed segment and the high speed segment as the second vehicle speed; The low-speed zone turning angle acquisition unit is used to acquire a first rear wheel follow-up steering angle as the low-speed zone rear wheel turning angle according to the ratio curve of the rear wheel and front wheel turning angles in the low-speed zone and the front wheel turning angle when the vehicle speed is lower than the first vehicle speed; The high-speed zone turning angle acquisition unit is used to acquire a second rear wheel follow-up steering angle as the high-speed section rear wheel turning angle according to the ratio of the rear wheel turning angle to the front wheel turning angle in the high-speed section and the front wheel turning angle when the vehicle speed is higher than the second vehicle speed; The medium speed area steering angle acquisition unit is used to use the sum of the first rear wheel follow-up steering angle and the second rear wheel follow-up steering angle as the medium speed section rear wheel steering angle when the vehicle speed is between the first vehicle speed and the second vehicle speed.

9. The device according to claim 8, It is characterized in that The first vehicle speed obtaining unit includes: A first ratio acquisition subunit is used to acquire a ratio of the maximum lateral acceleration limited by the tire adhesion limit to the steering sensitivity; there is a corresponding relationship between the steering sensitivity and the current vehicle speed; A second ratio acquisition subunit is used to acquire the ratio of the maximum rack displacement of the forward rotation to the lever arm; The first vehicle speed acquisition subunit is used to acquire the current vehicle speed as the first vehicle speed when the ratio of the maximum lateral acceleration limited by the tire adhesion limit to the steering sensitivity is equal to the ratio of the forward maximum rack displacement to the lever arm.

10. The device according to claim 8, It is characterized in that The second vehicle speed obtaining unit includes: A relationship acquisition subunit is used for, when the steady-state yaw rate gain reaches a maximum value, the second vehicle speed is a negative exponential power of a stability factor; and the stability factor is related to the steady-state yaw rate gain.

Images