Method and device for rear wheel steering servo control

Abstract

The application discloses a rear wheel steering servo control method and device. A demarcation value first vehicle speed of a low speed section vehicle speed and a medium speed section vehicle speed is obtained according to calibration parameters. A demarcation value second vehicle speed of the medium speed section vehicle speed and a high speed section vehicle speed is obtained according to a corresponding relationship between a steady state yaw rate gain and a vehicle speed. A first rear wheel servo steering angle as a low speed section rear wheel steering angle is obtained according to a calibration curve and a front wheel steering angle. A second rear wheel servo steering angle as a high speed section rear wheel steering angle is obtained according to a ratio of the high speed section rear wheel steering angle and the front wheel steering angle. A sum of the first rear wheel servo steering angle and the second rear wheel servo steering angle is taken as a medium speed section rear wheel steering angle. The method 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, the front wheel steering angle and the like, calculates the rear wheel steering angle through calibration values, provides a theoretical basis, and has strong engineering practicability. The calibration values are stable, the acquisition difficulty is low, and the calculation result has high robustness.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of automobiles, in particular to a rear wheel steering follow-up control method and device. BACKGROUND

[0002] With the popularization and in-depth of intelligent driving technology, the rear wheel auxiliary steering function is also constantly upgrading. In the low-speed driving area, the rear wheel angle is opposite to the front wheel angle, which reduces the turning radius, thereby improving the convenience of the vehicle in a small space or U-turn. In the high-speed driving area, the rear wheel slightly reverses the steering, which is not as sensitive as in the low-speed driving area, so that the steering motion of the vehicle is easier to control and not easy to lose stability, thereby improving the high-speed driving stability of the vehicle.

[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 weak engineering practicability. Moreover, these physical theories contain too many parameters, which are not only complex to obtain, but also easily affected by external interference or self-vehicle factors. Therefore, the present application provides a rear wheel steering follow-up control method with clear physical meaning and engineering implementation value, and high robustness. SUMMARY

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

[0005] The present application discloses a rear wheel steering follow-up control method, which comprises:

[0006] According to the maximum lateral acceleration limited by the tire adhesion limit, the steering sensitivity, the maximum rack displacement of the front wheel, and the force arm, the dividing value of the low-speed section vehicle speed and the medium-speed section vehicle speed is obtained as a first vehicle speed;

[0007] According to the change process of the steady-state yaw rate gain with the vehicle speed, the vehicle speed corresponding to the maximum value of the steady-state yaw rate gain is obtained as the dividing value of the medium-speed section vehicle speed and the high-speed section vehicle speed as a second vehicle speed;

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

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

[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 taken as the medium-speed section rear wheel angle.

[0011] Optionally, the maximum lateral acceleration limited according to the tire adhesion limit, the steering sensitivity, the maximum rack displacement of the front turning and the force arm, the dividing value of the low-speed section vehicle speed and the medium-speed section vehicle speed is a first vehicle speed, comprising:

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

[0013] Obtaining the ratio of the maximum rack displacement of the front turning and the force arm;

[0014] When the ratio of the maximum lateral acceleration limited according to the tire adhesion limit and the steering sensitivity is equal to the ratio of the maximum rack displacement of the front turning and the force arm, obtaining the current vehicle speed as the first vehicle speed.

[0015] Optionally, the dividing value of the medium-speed section vehicle speed and the high-speed section vehicle speed is a second vehicle speed, which is obtained according to the change process of the steady-state yaw rate gain with the vehicle speed, and the second vehicle speed is obtained when the steady-state yaw rate gain reaches the maximum value, comprising:

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

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

[0018] Collecting the 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] Obtaining the product of the current vehicle speed corresponding to the value in the ratio curve and the front wheel angle as the first rear wheel follow-up steering angle.

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

[0022] Obtaining the ratio of the rear wheel angle and the front wheel angle in the high-speed section;

[0023] Obtaining the product of the ratio and the front wheel angle as the second rear wheel follow-up steering angle.

[0024] Optionally, the ratio of the rear wheel angle and the front wheel angle in the high-speed section is obtained, comprising:

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

[0026] Optionally, after the low-speed rear wheel angle, the low-speed rear wheel angle or the low-speed rear wheel angle is obtained, the method further comprises:

[0027] Obtaining a calibrated rear wheel steering follow-up gain;

[0028] According to the maximum lateral acceleration limited by the tire adhesion limit, the steering sensitivity, the rear wheel maximum rack displacement and the force arm, a limit value of the rear wheel angle is obtained;

[0029] The obtained low-speed rear wheel angle, the low-speed rear wheel angle or the low-speed rear wheel angle, the rear wheel steering follow-up gain and the limit value are taken as an output value set;

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

[0031] Based on the above-mentioned rear wheel steering follow-up control method, the application further discloses a rear wheel steering follow-up control device, comprising a first vehicle speed obtaining unit, a second vehicle speed obtaining unit, a low-speed zone angle obtaining unit, a high-speed zone angle obtaining unit and a medium-speed zone angle obtaining unit.

[0032] The first vehicle speed obtaining unit is used to obtain a first vehicle speed as a demarcation value of a low-speed section vehicle speed and a medium-speed section vehicle speed according to the maximum lateral acceleration limited by the tire adhesion limit, the steering sensitivity, the front wheel maximum rack displacement and the force arm;

[0033] The second vehicle speed obtaining unit is used to obtain a second vehicle speed as a demarcation value of a medium-speed section vehicle speed and a high-speed section vehicle speed according to a change process of the steady-state yaw rate gain with the vehicle speed, when the steady-state yaw rate gain reaches a maximum value.

[0034] The low-speed zone angle obtaining unit is used to obtain a first rear wheel follow-up steering angle as a low-speed section rear wheel angle according to a low-speed section rear wheel angle and a front wheel angle when the vehicle speed is lower than the first vehicle speed.

[0035] The high-speed zone angle obtaining unit is used to obtain a second rear wheel follow-up steering angle as a high-speed section rear wheel angle according to a high-speed section rear wheel angle and the front wheel angle when the vehicle speed is higher than the second vehicle speed.

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

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

[0038] a first ratio obtaining sub-unit, configured to obtain a ratio of the maximum lateral acceleration limited by the tire adhesion limit to the steering sensitivity, wherein the steering sensitivity has a corresponding relationship with the current vehicle speed;

[0039] a second ratio obtaining sub-unit, configured to obtain a ratio of the maximum rack displacement in the front turning to the force arm;

[0040] a first vehicle speed obtaining sub-unit, configured to obtain 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 maximum rack displacement in the front turning to the force arm.

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

[0042] a relationship obtaining sub-unit, configured to obtain the second vehicle speed as a negative exponential power of a stability factor when the steady-state yaw rate gain reaches a maximum value, wherein the stability factor is related to the steady-state yaw rate gain.

[0043] Optionally, the low-speed region turning angle obtaining unit comprises:

[0044] a steering wheel collecting sub-unit, configured to collect a steering wheel turning angle;

[0045] a front wheel turning angle obtaining sub-unit, configured to obtain a quotient of the steering wheel turning angle and a front wheel steering transmission ratio as the front wheel turning angle;

[0046] a first turning angle obtaining sub-unit, configured to obtain a product of a value corresponding to the ratio curve in the current vehicle speed and the front wheel turning angle as the first rear wheel follow-up steering turning angle.

[0047] Optionally, the high-speed region turning angle obtaining unit comprises:

[0048] a turning angle ratio obtaining sub-unit, configured to obtain a ratio of the rear wheel turning angle to the front wheel turning angle in the high-speed section;

[0049] a second turning angle obtaining sub-unit, configured to obtain a product of the ratio and the front wheel turning angle as the second rear wheel follow-up steering turning angle.

[0050] Optionally, the turning angle ratio obtaining sub-unit is configured to:

[0051] obtain the ratio 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 configured to acquire a calibrated rear wheel steering following gain;

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

[0055] an output value set acquisition unit configured to acquire 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 configured to output the smallest value in the output value set to control the rear wheels of the vehicle.

[0057] The application discloses a rear wheel steering following control method and device. A first vehicle speed is obtained according to a calibration parameter, which is a demarcation value between a low-speed section and a medium-speed section. A second vehicle speed is obtained according to a corresponding relationship between a steady-state yaw rate gain and a vehicle speed, which is a demarcation value between the medium-speed section and a high-speed section. A first rear wheel following steering angle is obtained as a low-speed rear wheel angle according to a calibration curve and a front wheel angle. A second rear wheel following steering angle is obtained as a high-speed rear wheel angle according to a ratio of the high-speed rear wheel angle to the front wheel angle and the front wheel angle. A sum of the first rear wheel following steering angle and the second rear wheel following steering angle is taken as a medium-speed rear wheel angle. The method divides the vehicle speed into three speed sections, controls the rear wheel angle through different strategies, identifies the driver's intention according to the vehicle speed, the front wheel angle and the like, and calculates the rear wheel angle through calibration values, thereby providing a theoretical basis and strong engineering practicability. The calibration values are stable, the acquisition difficulty is low, the calculation result is high in robustness, and the calculation result does not change with the vehicle load. BRIEF DESCRIPTION OF DRAWINGS

[0058] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, brief introductions will be given to the drawings needed in the embodiments or prior art description. Obviously, the drawings in the following description are only embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative effort on the basis of the provided drawings.

[0059] Figure 1 A flowchart of a rear wheel steering following control method disclosed by an embodiment of the present application;

[0060] Figure 2 Variation diagrams of the first rear wheel following steering angle and the second rear wheel following steering angle in each speed section disclosed by an embodiment of the present application;

[0061] Figure 3 A structural diagram of a rear wheel steering following control device disclosed by an embodiment of the present application. DETAILED DESCRIPTION

[0062] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative effort belong to the scope of protection of the present application.

[0063] Embodiment one: The present application discloses a rear wheel steering follow-up control method.

[0064] Specifically, please refer to Figure 1 The rear wheel steering follow-up control method disclosed in the embodiment comprises 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 of the front steering and the force arm, the demarcation value of the low-speed section vehicle speed and the medium-speed section vehicle speed is obtained as the first vehicle speed.

[0066] In the method described in the embodiment, the front wheel steering angle data can be obtained according to the steering wheel data and the front wheel steering transmission ratio. Specifically, the front wheel steering angle can be obtained by dividing the steering wheel steering angle collected by the sensor by the front wheel steering transmission ratio, or the front wheel steering angle 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 the embodiment, the ratio of the maximum lateral acceleration limited by the tire adhesion limit and the steering sensitivity is obtained, and the steering sensitivity and the current vehicle speed have a corresponding relationship. Then the ratio of the maximum rack displacement of the front steering and the force arm is obtained. Then the front wheel steering angle limit value is calculated by the following formula:

[0068]

[0069] In the formula, δ max is the front wheel steering angle limit value, 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 of the front steering, and Lever is the force arm.

[0070] In the method described in the embodiment, when the ratio of the maximum lateral acceleration limited by the tire adhesion limit and the steering sensitivity is equal to the ratio of the maximum rack displacement of the front steering and the force arm, the current vehicle speed is obtained as the first vehicle speed. That is, when v is greater than the first vehicle speed v0, the ratio of ay max to SS ch is greater than s rack_maxThe ratio of f to Lever. When v is less than v0, 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 given, it can be determined based on SS. ch The correspondence with v yields v0. That is, when the ratio of the maximum lateral acceleration limited by tire adhesion limit to steering sensitivity is equal to the ratio of the maximum rack displacement to the lever arm, the current vehicle speed is obtained as the first vehicle speed.

[0071] Step 102: Based on the change process of steady-state yaw rate gain with vehicle speed, obtain the vehicle speed corresponding to the maximum value of steady-state yaw rate gain, and use it as the dividing value between medium-speed and high-speed vehicle speeds 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 its maximum value, the relationship between the stability factor related to the steady-state yaw rate gain and the second vehicle speed is as follows:

[0073]

[0074] In the formula, k is the stability factor.

[0075] Step 103: When the vehicle speed is lower than the first vehicle speed, obtain the first rear wheel steering angle based on the ratio curve of the rear wheel to the front wheel steering angle in the low speed segment and the front wheel steering angle, and use it as the rear wheel steering angle in the low speed segment.

[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 steering angle is obtained as the first rear wheel steering angle. The ratio curve is a calibration curve; based on the current vehicle speed, the corresponding ratio of the rear wheel to the front wheel steering angle can be found in the ratio curve. The calculated front wheel steering angle is then multiplied by this ratio to obtain the first rear wheel steering angle.

[0077] Step 104: When the vehicle speed is higher than the second vehicle speed, obtain the second rear wheel steering angle based on the ratio of the rear wheel to the front wheel steering angle in the high-speed section and the front wheel steering angle, and use it as the rear wheel steering angle in the high-speed section.

[0078] In the method described in this embodiment, the ratio of the rear wheel to the front wheel steering 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, V1 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 turning angle to the front wheel turning angle in the high speed section is multiplied by the front wheel turning angle to obtain the second rear wheel following turning 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 following turning angle and the second rear wheel following turning angle is taken as the rear wheel turning angle in the medium speed section.

[0083] In the method described in this embodiment, the calibrated rear wheel turning following gain is obtained. The rear wheel turning following gain includes the gain of the rear wheel turning following the front wheel turning angle, the gain of the rear wheel turning following the front wheel turning angle velocity, and the gain of the rear wheel turning following the front wheel turning angle degree.

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

[0085]

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

[0087] In the method described in this embodiment, the obtained rear wheel turning angle in the low speed section, the rear wheel turning angle in the medium speed section, or the rear wheel turning angle in the high speed section, the rear wheel turning following gain, and the limit value are taken as an output value set. The minimum value in the set is output to control the rear wheel 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 turning angle obtained in steps 103 to 105, Gs is the gain of the rear wheel turning following the front wheel turning angle, Gds is the gain of the rear wheel turning following the front wheel turning angle velocity, and Gdb is the dead zone of the rear wheel turning following the front wheel turning angle degree.

[0091] The method disclosed in the embodiment divides the vehicle speed into three speed sections, controls the rear wheel turning angle through different strategies respectively, identifies the driver's intention according to the vehicle speed, the front wheel turning angle and the like, and calculates the rear wheel turning angle through a calibration value, thereby providing a theoretical basis and strong engineering practicability. The calibration value in the method is stable and can be set and obtained with low difficulty, so that the change of the vehicle state (such as load) will not affect the calculation process and accuracy of the rear wheel steering follow-up function, and the method has robustness to external interference. Meanwhile, the method considers the safety limit value and can directly introduce a specific executable quantization method, thereby having great engineering application value. In addition, the method does not need to increase a sensor for the rear wheel steering and does not need the feedback of the vehicle state quantity.

[0092] Figure 2 The first rear wheel follow-up steering turning angle and the second rear wheel follow-up steering turning angle change diagram for each speed section disclosed in the embodiment of the application is shown in FIG. 1. Figure 2

[0093] The rear wheel follow-up steering turning angle is continuously changed with the vehicle speed. When the vehicle speed is lower than v0, the second rear wheel follow-up steering turning angle is set to 0, and only the first rear wheel follow-up steering turning angle is obtained as the rear wheel follow-up steering turning angle in the low speed area. When the vehicle speed is higher than v1, the first rear wheel follow-up steering turning angle is set to 0, and only the second rear wheel follow-up steering turning angle is obtained as the rear wheel follow-up steering turning angle in the high speed area. When the vehicle speed is between v0 and v1, the first rear wheel follow-up steering turning angle and the second rear wheel follow-up steering turning angle calculated are added, and the obtained value is taken as the rear wheel follow-up steering turning angle in the medium speed area.

[0094] Based on the rear wheel steering follow-up control method disclosed in the above embodiment, the embodiment correspondingly discloses a rear wheel steering follow-up control device. Please refer to FIG. 2. Figure 3 The rear wheel steering follow-up control device comprises a first vehicle speed obtaining unit 301, a second vehicle speed obtaining unit 302, a low speed area turning angle obtaining unit 303, a high speed area turning angle obtaining unit 304 and a medium speed area turning angle obtaining unit 305.

[0095] The first vehicle speed obtaining unit 301 is used to obtain the first vehicle speed as the demarcation value of the low speed section vehicle speed and the medium speed section vehicle speed according to the maximum lateral acceleration limited by the tire adhesion limit, the steering sensitivity, the maximum rack displacement of the front wheel and the force arm.

[0096] The second vehicle speed obtaining unit 302 is used to obtain the second vehicle speed as the demarcation value of the medium speed section vehicle speed and the high speed section vehicle speed according to the change process of the steady state yaw rate gain with the vehicle speed, and the vehicle speed corresponding to the maximum value of the steady state yaw rate gain.

[0097] ​The low-speed area corner acquisition unit 303 is configured to acquire a first rear wheel follow-up steering corner as a low-speed stage rear wheel corner according to a low-speed stage rear wheel and front wheel corner ratio curve and the front wheel corner when the vehicle speed is lower than a first vehicle speed.

[0098] The high-speed area corner acquisition unit 304 is configured to acquire a second rear wheel follow-up steering corner as a high-speed stage rear wheel corner according to a high-speed stage rear wheel and front wheel corner ratio and the front wheel corner when the vehicle speed is higher than a second vehicle speed.

[0099] The medium-speed area corner acquisition unit 305 is configured to acquire a sum of the first rear wheel follow-up steering corner and the second rear wheel follow-up steering corner as a medium-speed stage rear wheel corner when the vehicle speed is between the first vehicle speed and the second vehicle speed.

[0100] Optionally, the first vehicle speed acquisition unit 301 comprises:

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

[0102] A second ratio acquisition subunit is configured to acquire a ratio of a maximum rack displacement to a force arm;

[0103] A first vehicle speed acquisition subunit is configured 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 maximum rack displacement to the force arm.

[0104] Optionally, the second vehicle speed acquisition unit 302 comprises:

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

[0106] Optionally, the low-speed area corner acquisition unit 303 comprises:

[0107] A steering wheel collection subunit is configured to collect a steering wheel corner;

[0108] A front wheel corner acquisition subunit is configured to acquire a quotient of the steering wheel corner and a front wheel steering transmission ratio as the front wheel corner;

[0109] A first corner acquisition subunit is configured to acquire a product of a value corresponding to the ratio curve in the current vehicle speed and the front wheel corner as the first rear wheel follow-up steering corner.

[0110] Optionally, the high-speed area corner acquisition unit 304 comprises:

[0111] a corner ratio acquisition subunit, configured to acquire a ratio of the rear wheel corner to the front wheel corner in the high-speed section;

[0112] a second corner acquisition subunit, configured to acquire a product of the ratio and the front wheel corner as the second rear wheel follow-up corner.

[0113] Optionally, the corner ratio acquisition subunit is configured to:

[0114] acquire the ratio 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, configured to acquire a calibrated rear wheel cornering follow-up gain;

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

[0118] an output value set acquisition unit, configured to acquire the low-speed section rear wheel corner, the low-speed section rear wheel corner or the low-speed section rear wheel corner, the rear wheel cornering follow-up gain and the limit value as an output value set;

[0119] a rear wheel control unit, configured to output a minimum value in the output value set to control the rear wheel of the vehicle.

[0120] Embodiments in the specification are described in a progressive manner. For the device disclosed by the embodiments, since it corresponds to the method disclosed by the embodiments, the description is relatively simple, and the relevant part is referred to the method part.

[0121] It should also be noted that, in this document, the relationship terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. Moreover, the terms "include", "contain" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or equipment. Without more limitations, the element defined by the statement "including a" does not exclude the presence of another identical element in the process, method, article or equipment including the element.

[0122] The steps of a method or algorithm described in connection with the embodiments disclosed herein can be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module can reside in Random Access Memory (RAM), non-volatile memory (ROM), erasable programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. The exemplary storage media are coupled to the processor such that the processor can read information from, and write information to, the storage media. In the alternative, hardwired circuitry can be used in place of, or in combination with, software instructions to implement processes consistent with the principles of the application. Although exemplary embodiments of the present application have been described herein, other and further modifications can be made by those skilled in the art without departing from the spirit and scope of the present application.

[0123] Any feature in the described embodiments that is recited in the specification and / or claims can be replaced by alternative features serving the same, equivalent or similar purpose, unless otherwise stated.

[0124] The foregoing description of the disclosed embodiments enables a person skilled in the art to make or use the application. Modifications of these embodiments will occur to those skilled in the art, without departing from the spirit of the application, and the general principles defined herein can be implemented in other embodiments. The present application is therefore not limited to the particular details shown and described herein but embraces all such modifications that are within the spirit and scope of the application.

Claims

1. A method of rear wheel steering servo control, characterized by, The method comprises the following steps: According to the maximum lateral acceleration limited by the tire adhesion limit, the steering sensitivity, the maximum rack displacement of the front steering and the force arm, the demarcation value of the low-speed section vehicle speed and the medium-speed section vehicle speed is obtained as the first vehicle speed; According to the change process of the steady-state yaw rate gain with the vehicle speed, the vehicle speed corresponding to the maximum value of the steady-state yaw rate gain is obtained as the demarcation value of the medium-speed section vehicle speed and the high-speed section vehicle speed as the second vehicle speed; When the vehicle speed is lower than the first vehicle speed, the first rear wheel follow-up steering angle is obtained according to the ratio curve of the low-speed section rear wheel and the front wheel steering angle and the front wheel steering angle as the low-speed section rear wheel steering angle; When the vehicle speed is higher than the second vehicle speed, the second rear wheel follow-up steering angle is obtained according to the ratio of the high-speed section rear wheel and the front wheel steering angle and the front wheel steering angle as the high-speed section rear wheel steering angle; 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 taken as the medium-speed section rear wheel steering angle.

2. The method of claim 1, wherein, The method comprises the following steps: The ratio of the maximum lateral acceleration limited by the tire adhesion limit and the steering sensitivity is obtained; the steering sensitivity and the current vehicle speed have a corresponding relationship; The ratio of the maximum rack displacement of the front steering and the force arm is obtained; When the ratio of the maximum lateral acceleration limited by the tire adhesion limit and the steering sensitivity is equal to the ratio of the maximum rack displacement of the front steering and the force arm, the current vehicle speed is obtained as the first vehicle speed.

3. The method of claim 1, wherein, The method comprises the following steps: When the steady-state yaw rate gain reaches the maximum value, the negative exponential power of the stability factor is obtained as the second vehicle speed; the stability factor is related to the steady-state yaw rate gain.

4. The method of claim 1, wherein, The method comprises the following steps: The steering wheel steering angle is collected; The quotient of the steering wheel steering angle and the front wheel steering transmission ratio is obtained as the front wheel steering angle; The product of the value corresponding to the ratio curve and the front wheel steering angle at the current vehicle speed is obtained as the first rear wheel follow-up steering angle.

5. The method of claim 4, wherein, The method comprises the following steps: The ratio of the high-speed section rear wheel and the front wheel steering angle is obtained; The product of the ratio of the high-speed section rear wheel and the front wheel steering angle and the front wheel steering angle is obtained as the second rear wheel follow-up steering angle.

6. The method of claim 5, wherein, The method comprises the following steps: According to the first vehicle speed, the second vehicle speed and the current vehicle speed, the ratio of the high-speed section rear wheel and the front wheel steering angle is obtained.

7. The method according to any one of claims 1 to 6, characterized in that, After the low-speed section rear wheel steering angle, the high-speed section rear wheel steering angle or the medium-speed section rear wheel steering angle is obtained, the method further comprises the following steps: The calibrated rear wheel steering gain is obtained; Obtaining a limit value of the rear wheel steering angle according to the maximum lateral acceleration limited by the tire adhesion limit, the steering sensitivity, the maximum rack displacement of the rear steering and the force arm; Obtaining the output value set as an output value set of the obtained low-speed rear wheel steering angle, the high-speed rear wheel steering angle or the medium-speed rear wheel steering angle, the rear wheel steering gain and the limit value; Outputting the minimum value in the output value set to control the rear wheel.

8. A device for rear wheel steering servo control, characterized by Comprise: A first vehicle speed obtaining unit, a second vehicle speed obtaining unit, a low-speed zone steering angle obtaining unit, a high-speed zone steering angle obtaining unit and a medium-speed zone steering angle obtaining unit; The first vehicle speed obtaining unit is configured to obtain a first vehicle speed as a demarcation value between a low-speed vehicle speed and a medium-speed vehicle speed according to the maximum lateral acceleration limited by the tire adhesion limit, the steering sensitivity, the maximum rack displacement of the front steering and the force arm; The second vehicle speed obtaining unit is configured to obtain a second vehicle speed as a demarcation value between the medium-speed vehicle speed and a high-speed vehicle speed according to a change process of the steady-state yaw rate gain with the vehicle speed, the second vehicle speed corresponding to a maximum value of the steady-state yaw rate gain; The low-speed zone steering angle obtaining unit is configured to obtain a first rear wheel follow-up steering angle as a low-speed rear wheel steering angle according to a ratio curve of the low-speed rear wheel steering angle to the front wheel steering angle and the front wheel steering angle when the vehicle speed is lower than the first vehicle speed; The high-speed zone steering angle obtaining unit is configured to obtain a second rear wheel follow-up steering angle as a high-speed rear wheel steering angle according to a ratio of the high-speed rear wheel steering angle to the front wheel steering angle and the front wheel steering angle when the vehicle speed is higher than the second vehicle speed; The medium-speed zone steering angle obtaining unit is configured to obtain a sum of the first rear wheel follow-up steering angle and the second rear wheel follow-up steering angle as a medium-speed rear wheel steering angle when the vehicle speed is between the first vehicle speed and the second vehicle speed.

9. The apparatus of claim 8, wherein, The first vehicle speed obtaining unit comprises: A first ratio obtaining subunit configured to obtain a ratio of the maximum lateral acceleration limited by the tire adhesion limit to the steering sensitivity, the steering sensitivity corresponding to a current vehicle speed; A second ratio obtaining subunit configured to obtain a ratio of the maximum rack displacement of the front steering to the force arm; A first vehicle speed obtaining subunit configured to obtain 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 maximum rack displacement of the front steering to the force arm.

10. The apparatus of claim 8, wherein, The second vehicle speed obtaining unit comprises: A relationship formula obtaining subunit configured to obtain a second vehicle speed as a negative exponential power of a stability factor when the steady-state yaw rate gain reaches a maximum value, the stability factor being related to the steady-state yaw rate gain.

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