Vehicle control method and device based on rear wheel steering

Abstract

The invention provides a vehicle control method and device based on rear wheel steering. The method comprises the steps that whether a target vehicle is in an unstable state or not is judged based on a two-degree-of-freedom vehicle dynamics model of the target vehicle; when the target vehicle is in the unstable state, a rear wheel steering mode is determined according to the vehicle speed of the target vehicle; based on the deviation between the actual yaw velocity and the expected yaw velocity of the target vehicle, determining a rear wheel steering angle by adopting a proportional-integral-derivative controller; and controlling rear wheels of the target vehicle to steer according to the rear wheel steering mode and the rear wheel steering angle. By actively adjusting the steering angle of the rear wheel, the dynamic control capability of the vehicle is remarkably improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of vehicle control technology, in particular to a vehicle control method and device based on rear wheel steering. BACKGROUND

[0002] The current vehicle stability control (VSC) system usually adopts an electronic stability control system (ESC) or an electronic stability program (ESP), which is a safety system that actively intervenes in the dynamics of the vehicle through electronic technology, aiming to improve the stability of the vehicle control to prevent loss of control. Specifically, through a plurality of sensors, the vehicle state data is continuously collected, and then the collected real-time data is compared with the preset model (such as the expected path of the driver), to determine whether there is a situation such as skidding, side slipping or deviating from the track, and to actively intervene when necessary.

[0003] The existing VSC system is a stability control system mainly relying on brake intervention, and its control performance will be greatly reduced in extreme conditions. For example, on ice, snow, sand and other low-friction road surfaces, the VSC system may intervene excessively (such as frequent braking) due to tire skidding, and thus cause the controllability to decrease; when the vehicle approaches the physical limit (such as drifting) during extreme cornering or intense driving, the VSC system may forcibly intervene in the power output or braking, which violates the intention of the driver.

[0004] In summary, the existing VSC system mainly relying on brake intervention has great limitations, and there is an urgent need for a more stable vehicle control method. SUMMARY

[0005] The present application aims to solve at least one of the technical problems existing in the prior art, and provides a vehicle control method and device based on rear wheel steering.

[0006] In a first aspect, the present application embodiment provides a vehicle control method based on rear wheel steering, comprising:

[0007] determining whether the target vehicle is in an unstable state based on a two-degree-of-freedom vehicle dynamics model of the target vehicle;

[0008] when the target vehicle is in an unstable state, determining a rear wheel steering mode according to the vehicle speed of the target vehicle;

[0009] determining a rear wheel steering angle based on the deviation of the actual yaw rate of the target vehicle from the expected yaw rate using a proportional-integral-derivative controller;

[0010] controlling the rear wheels of the target vehicle to steer according to the rear wheel steering mode and the rear wheel steering angle.

[0011] Optionally, the rear wheel steering mode is determined according to a vehicle speed of the target vehicle, comprising:

[0012] when the vehicle speed of the target vehicle is less than a preset vehicle speed threshold, the rear wheel steering mode is opposite to the front wheel;

[0013] when the vehicle speed of the target vehicle is greater than or equal to the preset vehicle speed threshold, the rear wheel steering mode is same as the front wheel.

[0014] Optionally, the expected yaw rate of the target vehicle is determined according to the following expression:

[0015] ;

[0016] wherein, represents the expected yaw rate, represents the vehicle speed, represents the wheelbase, represents a stability factor, represents the front wheel steering angle.

[0017] Optionally, before controlling the rear wheels of the target vehicle to steer according to the rear wheel steering mode and the rear wheel steering angle, the method further comprises:

[0018] limiting the rear wheel steering angle within a preset steering angle range.

[0019] Optionally, before controlling the rear wheels of the target vehicle to steer according to the rear wheel steering mode and the rear wheel steering angle, the method further comprises:

[0020] when a center of mass side slip angle of the target vehicle is greater than a preset side slip angle threshold, the rear wheel steering angle is corrected according to the following expression:

[0021] ;

[0022] wherein, represents the corrected rear wheel steering angle, represents the uncorrected rear wheel steering angle, represents a center of mass side slip angle coefficient, represents the center of mass side slip angle.

[0023] Optionally, the method further comprises:

[0024] obtaining a road surface adhesion coefficient of a road surface on which the target vehicle travels through a tire force observer of the target vehicle;

[0025] adapting the weight of the rear wheel steering control and the brake control according to the road surface adhesion coefficient of the road surface on which the target vehicle travels and / or the vehicle speed.

[0026] Optionally, the weight of the rear wheel steering control and the brake control is adaptively adjusted according to the road adhesion coefficient of the target vehicle running road surface and / or the vehicle speed, comprising:

[0027] When the road adhesion coefficient of the target vehicle running road surface is less than a preset road adhesion coefficient threshold, and / or, the vehicle speed of the target vehicle is greater than a preset vehicle speed threshold, the weight of the rear wheel steering control is increased, and the weight of the brake control is reduced.

[0028] In a second aspect, the embodiments of the present application provide a vehicle control device based on rear wheel steering, comprising:

[0029] A judging module is configured to judge whether the target vehicle is in an unstable state based on a two-degree-of-freedom vehicle dynamics model of the target vehicle.

[0030] A first processing module is configured to determine a rear wheel steering mode according to the vehicle speed of the target vehicle when the target vehicle is in the unstable state.

[0031] A second processing module is configured to determine a rear wheel steering angle by using a proportional-integral-derivative controller based on the deviation between the actual yaw rate and the expected yaw rate of the target vehicle.

[0032] A control module is configured to control the rear wheel of the target vehicle to steer according to the rear wheel steering mode and the rear wheel steering angle.

[0033] In a third aspect, the present application provides an electronic device, comprising a processor and a memory, wherein the memory stores computer readable instructions, and when the computer readable instructions are executed by the processor, the steps in the method provided in the first aspect are executed.

[0034] In a fourth aspect, the present application provides a storage medium, which stores a computer program, and when the computer program is executed by a processor, the steps in the method provided in the first aspect are executed.

[0035] In a fifth aspect, the present application provides a computer program product, which comprises a computer program, and when the computer program is executed by a processor, the steps in the method provided in the first aspect are executed.

[0036] From the above technical solutions, it can be seen that the present application has the following advantages:

[0037] This invention provides a vehicle control method and apparatus based on rear-wheel steering. The method determines whether the target vehicle is in an unstable state based on a two-degree-of-freedom vehicle dynamics model. When the target vehicle is in an unstable state, the rear-wheel steering mode is determined based on the vehicle's speed. Based on the deviation between the actual and desired yaw rates of the target vehicle, a proportional-integral-derivative (PID) controller is used to determine the rear-wheel steering angle. The rear wheels of the target vehicle are then steered according to the rear-wheel steering mode and the rear-wheel steering angle. By actively adjusting the rear-wheel steering angle, the vehicle's dynamic control capability is significantly improved. Attached Figure Description

[0038] Figure 1 This is a flowchart illustrating a vehicle control method based on rear-wheel steering according to a first embodiment of the present invention.

[0039] Figure 2 This is a schematic flowchart of a second embodiment of a vehicle control method based on rear-wheel steering according to the present invention;

[0040] Figure 3 This is a flowchart illustrating a third embodiment of the vehicle control method based on rear-wheel steering according to the present invention.

[0041] Figure 4 This is a structural block diagram of an embodiment of a vehicle control device based on rear-wheel steering according to the present invention;

[0042] Figure 5 This is a structural block diagram of an electronic device provided in an embodiment of the present invention. Detailed Implementation

[0043] To enable those skilled in the art to better understand the technical solutions of the present invention, exemplary embodiments of the present invention are described below in conjunction with the accompanying drawings, including various details of the embodiments of the present invention to aid understanding. These should be considered merely exemplary. Therefore, those skilled in the art should recognize that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of the present invention. Similarly, for clarity and brevity, descriptions of well-known functions and structures are omitted in the following description.

[0044] Where there is no conflict, the various embodiments of the present invention and the features thereof may be combined with each other.

[0045] As used herein, the term “and / or” includes any and all combinations of one or more related enumerated entries.

[0046] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. "Coupled" or "connected" or similar terms are not restricted to physical or mechanical connections or associations, but can also include electrical connections, whether direct or indirect.

[0047] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present disclosure, and will not be interpreted in an overly literal or overly formal sense unless expressly so defined herein.

[0048] In the technical solutions of the present application, the collection, storage, use, processing, transmission, provision and disclosure of user personal information comply with relevant laws and regulations and do not violate public order and good customs. The use of user data in the technical solutions complies with relevant national laws and regulations (for example, "Information Security Technology Personal Information Security Specification" and the like). For example, appropriate measures are taken for personal information access control; restrictions are given to the display of personal information; the use purpose of personal information does not exceed the direct or reasonably related range; the use of personal information eliminates explicit identity pointing and avoids precise positioning to a specific individual.

[0049] The working principle of the existing VSC system is to continuously collect vehicle state data through multiple groups of sensors, and then compare the real-time data with a preset model (such as the expected path of the driver) by an electronic control unit (ECU) to determine whether there is a situation of slipping, side slipping or deviating from the track, and then to actively intervene. The system excessively relies on sensor data such as wheel speed, steering angle, yaw rate, etc. If the sensor is contaminated (such as snow, mud) or fails (such as electromagnetic interference), it may lead to misjudgment of the vehicle state. Moreover, there is a millisecond-level delay in the collection and processing of sensor data, which may not be able to respond in real time in extreme dynamic scenarios (such as high-speed emergency obstacle avoidance). Performance degradation may occur in extreme working conditions: for example, on low-friction road surfaces such as ice and snow, sand, etc., the system may excessively intervene (such as frequent braking) due to tire slip, which may in turn cause a decrease in handling; in extreme cornering or aggressive driving, the vehicle may approach the physical limit (such as drifting), at which point the system may forcibly intervene in power output or braking, disrupting the driver's intent (especially in track or off-road scenarios where the system needs to be manually turned off).

[0050] To solve at least one of the above technical problems in the related art, the present application provides a vehicle control method based on rear wheel steering. Figure 1 A flowchart of an embodiment of the vehicle control method based on rear wheel steering of the present application is shown in FIG. 1. As shown in FIG. 1, the vehicle control method based on rear wheel steering provided in the embodiment can include the following steps. Figure 1

[0051] In step S101, it is determined whether the target vehicle is in an unstable state based on a two-degree-of-freedom vehicle dynamics model of the target vehicle.

[0052] In the embodiment, various state data of the target vehicle, such as vehicle speed, steering wheel angle, yaw rate, etc., can be collected in real time by various vehicle-mounted sensors carried by the target vehicle. Specifically, the rotational speed of each wheel can be monitored by a wheel speed sensor, the steering wheel angle can be obtained by a steering angle sensor, the lateral force of the vehicle can be detected by a lateral acceleration sensor, and the rotational speed of the vehicle around the vertical axis (e.g., oversteer or understeer) can be measured by a yaw rate sensor. Then, a two-degree-of-freedom vehicle dynamics model of the target vehicle is constructed based on the collected data, and finally it is determined whether the target vehicle is in an unstable state based on the two-degree-of-freedom vehicle dynamics model of the target vehicle.

[0053] In an optional implementation, the vehicle dynamics model can be constructed based on sensor data, and the deviation between the actual yaw rate ( ) and the expected yaw rate ( ) is calculated. If the deviation exceeds a preset deviation threshold or the tire lateral force is saturated, it is determined that the vehicle enters an unstable state. The actual yaw rate can be obtained by a vehicle-mounted sensor, and the expected yaw rate can be calculated. In an optional implementation, the expected yaw rate of the target vehicle is determined according to the following expression:

[0054]

[0055]

[0056] wherein represents the expected yaw rate, represents the vehicle speed, represents the wheelbase, represents a stability factor, and represents the front wheel steering angle.

[0057] In step S102, when the target vehicle is in an unstable state, the rear wheel steering mode is determined according to the vehicle speed of the target vehicle.

[0058] ​​​After determining that the target vehicle is in the unstable state, the rear wheel steering mode can be further determined according to the vehicle speed of the target vehicle. In an optional embodiment, the rear wheel steering mode is determined according to the vehicle speed of the target vehicle, which can specifically include: when the vehicle speed of the target vehicle is less than a preset vehicle speed threshold, the rear wheel steering mode is opposite to the front wheel; and when the vehicle speed of the target vehicle is greater than or equal to the preset vehicle speed threshold, the rear wheel steering mode is the same as the front wheel. The preset vehicle speed threshold can be calibrated when the vehicle is manufactured, for example, can be 40 km / h.

[0059] When the vehicle speed of the target vehicle is less than the preset vehicle speed threshold, that is, the target vehicle is in low-speed driving, the rear wheel and the front wheel are reversely rotated, which can effectively reduce the turning radius and improve the maneuverability of the vehicle in a narrow space; when the vehicle speed of the target vehicle is greater than or equal to the preset vehicle speed threshold, that is, the target vehicle is in high-speed driving, the rear wheel and the front wheel are rotatable in the same direction, which can extend the virtual wheelbase, suppress the yaw vibration, and improve the lane changing or curve stability. Further, for the understeering scene, the rear wheel and the front wheel are rotatable in the same direction (at high speed) or reversely at a small angle (at low speed), which can increase the whole vehicle yaw moment; a braking force is applied to the inner rear wheel to further suppress the push nose effect; for the oversteering scene, the rear wheel is reversely deflected quickly to offset the tail side slip trend; and the outer front wheel is braked to assist in restoring the vehicle body posture.

[0060] In step S103, the rear wheel steering angle is determined by using a proportional-integral-derivative controller based on the deviation of the actual yaw rate of the target vehicle from the expected yaw rate.

[0061] In order to suppress the excessive deviation of the vehicle yaw rate and prevent the occurrence of the oversteering or understeering situation, in the embodiment, after the rear wheel steering mode is determined, the rear wheel steering angle is further determined by using a proportional-integral-derivative controller based on the deviation of the actual yaw rate of the target vehicle from the expected yaw rate. Specifically, the rear wheel steering angle can be determined according to the following expression:

[0062] ;

[0063] wherein, represents the rear wheel steering angle, represents the expected yaw rate, represents the actual yaw rate, represents a proportional coefficient, represents an integral coefficient, represents a differential coefficient. It should be noted that, , and are calibration values, which can be obtained by calibration during vehicle calibration.

[0064] Step S104, controlling the rear wheels of the target vehicle to steer according to the rear wheel steering mode and the rear wheel steering angle control target.

[0065] After determining the rear wheel steering mode and the rear wheel steering angle in the embodiment, the rear wheels of the target vehicle can be controlled to steer according to the rear wheel steering mode and the rear wheel steering angle. The rear wheel steering can directly correct the vehicle yaw angle by adjusting the lateral force of the rear wheels; on low adhesion road surface (such as ice and snow), the rear wheel steering can assist in adjusting the vehicle body trajectory, which can reduce the risk of tire lock caused by excessive intervention of the braking system and maintain a higher vehicle speed. When the vehicle is oversteering, the rear wheel steering can actively compensate in the opposite direction (such as outward deflection of the rear wheels), which can quickly restore the balance of the vehicle body. When the vehicle is understeering, the rear wheels can rotate in the same direction to increase the lateral force, which can assist the front wheels in completing the steering.

[0066] The vehicle control method based on rear wheel steering provided in the embodiment can determine whether the target vehicle is in an unstable state based on a two-degree-of-freedom vehicle dynamics model of the target vehicle; when the target vehicle is in an unstable state, determine the rear wheel steering mode according to the vehicle speed of the target vehicle; determine the rear wheel steering angle by using a proportional-integral-derivative controller based on the deviation between the actual yaw rate and the expected yaw rate of the target vehicle; and control the rear wheels of the target vehicle to steer according to the rear wheel steering mode and the rear wheel steering angle. By actively adjusting the rear wheel steering angle, the dynamic control ability of the vehicle is significantly improved. The rear wheel steering angle is taken as an active control variable and incorporated into the vehicle stability control system, which breaks through the limitation of traditional dependence on braking; the rear wheel steering actively generates a yaw moment, which reduces the dependence on the braking system, not only prolongs the service life of the brake, but also adjusts the vehicle body posture more smoothly, which can significantly improve the driving comfort. Further, the mechanical adjustment of the rear wheel steering can partially compensate for the control lag caused by sensor delay or error, which reduces the sensitivity to sensor errors; and compared with the conversion of excessive kinetic energy into heat loss caused by frequent braking intervention, the mechanical control of the rear wheel steering is more energy-saving, which can prolong the endurance in electric vehicles and significantly optimize the energy efficiency.

[0067] On the basis of the above-mentioned embodiments, in order to avoid the risk of overshoot or oscillation of the rear wheel steering angle, the vehicle control method based on rear wheel steering provided in the embodiment further limits the rear wheel steering angle within a preset steering angle range, so as to improve the stability of the vehicle. That is, before controlling the rear wheel of the target vehicle to steer according to the rear wheel steering mode and the rear wheel steering angle, the rear wheel steering angle is limited within a preset steering angle range. The preset steering angle range can be calibrated when the vehicle is manufactured, for example, it can be set to (-10°, +10°). Taking the preset steering angle range (-10°, +10°) as an example, if the rear wheel steering angle determined by the proportional-integral-derivative controller is 12°, the rear wheel steering angle is limited to 10°; if the rear wheel steering angle determined by the proportional-integral-derivative controller is -13°, the rear wheel steering angle is limited to -10°; if the rear wheel steering angle determined by the proportional-integral-derivative controller is -3°, it remains unchanged. The power system can also be used to reduce the driving wheel torque, while ensuring that the rear wheel steering angle change rate is gentle, avoiding the sense of driving impact.

[0068] Since the vehicle mass center side slip angle (β) ) is too large, the vehicle lateral stability is damaged, the risk of losing control is greatly improved, and the control response and driving safety are deteriorated, therefore, on the basis of the above-mentioned embodiments, in order to further improve the stability of the vehicle control, the vehicle control method based on rear wheel steering provided in the embodiment further corrects the rear wheel steering angle according to the mass center side slip angle of the target vehicle. Specifically, before controlling the rear wheel of the target vehicle to steer according to the rear wheel steering mode and the rear wheel steering angle, when the mass center side slip angle of the target vehicle is greater than a preset side slip angle threshold, the rear wheel steering angle is corrected according to the following expression:

[0069] ;

[0070] Wherein, represents the corrected rear wheel steering angle, represents the rear wheel steering angle before correction, represents the mass center side slip angle coefficient, represents the mass center side slip angle.

[0071] Figure 2 is a flowchart of a second embodiment of a vehicle control method based on rear wheel steering of the application. As shown in Figure 2 , the vehicle control method based on rear wheel steering provided in the embodiment can include:

[0072] Step S201, determining whether the target vehicle is in an unstable state based on a two-degree-of-freedom vehicle dynamics model of the target vehicle.

[0073] The specific implementation can refer to the above step S101, and details are not described here.

[0074] Step S202, when the target vehicle is in an unstable state, determining the rear wheel steering mode according to the vehicle speed of the target vehicle.

[0075] The specific implementation can refer to the above step S102, and details are not described here.

[0076] Step S203, based on the deviation of the actual yaw rate of the target vehicle and the expected yaw rate, a proportional-integral-derivative controller is used to determine the rear wheel steering angle.

[0077] The specific implementation can refer to the above step S103, and details are not described here.

[0078] Step S204, when the target vehicle's center of mass side slip angle is greater than a preset side slip angle threshold, the center of mass side slip angle of the target vehicle is used to correct the rear wheel steering angle, to obtain a corrected rear wheel steering angle.

[0079] The preset side slip angle threshold can be calibrated when the vehicle is shipped, for example, it can be calibrated to 3°. Specifically, the rear wheel steering angle can be corrected according to the following expression:

[0080] ;

[0081] Wherein, represents the corrected rear wheel steering angle, represents the rear wheel steering angle before correction, represents the center of mass side slip angle coefficient, represents the center of mass side slip angle.

[0082] It should be noted that the rear wheel steering angle can also be compensated in advance based on the driver's steering wheel angle and the vehicle speed , that is, to make the rear wheel steering motor intervene in advance.

[0083] Step S205, controlling the rear wheel of the target vehicle to steer according to the rear wheel steering mode and the corrected rear wheel steering angle.

[0084] The specific implementation can refer to the above step S104, and details are not described here.

[0085] The vehicle control method based on rear wheel steering provided in the embodiment, on the basis of the above embodiment, further corrects the rear wheel steering angle using the center of mass side slip angle of the target vehicle when the center of mass side slip angle of the target vehicle is greater than a preset side slip angle threshold, further improving the stability of vehicle control.

[0086] On the basis of any of the above embodiments, the vehicle control method based on rear wheel steering provided in the embodiment further combines rear wheel steering with brake control for collaborative control from multiple dimensions. For example, when emergency braking, slight steering of the rear wheels can optimize load distribution and shorten the braking distance (experimental data shows that it can be reduced by about 5%); when changing lanes at high speed, rear wheel steering cooperates with ESC to suppress body roll, which can improve passenger comfort. The contribution ratio of rear wheel steering and braking is dynamically adjusted based on the road adhesion coefficient and vehicle speed, which improves the robustness of the system. Figure 3 FIG. 3 is a flowchart of a third embodiment of a vehicle control method based on rear wheel steering according to the present application. As shown in FIG. 3, the vehicle control method based on rear wheel steering provided in the embodiment can include the following steps. Figure 3

[0087] In step S301, it is determined whether the target vehicle is in an unstable state based on a two-degree-of-freedom vehicle dynamics model of the target vehicle.

[0088] The specific implementation can refer to step S101 described above, and will not be repeated here.

[0089] In step S302, when the target vehicle is in an unstable state, the rear wheel steering mode is determined according to the vehicle speed of the target vehicle.

[0090] The specific implementation can refer to step S102 described above, and will not be repeated here.

[0091] In step S303, the rear wheel steering angle is determined by a proportional-integral-derivative controller based on the deviation between the actual yaw rate and the expected yaw rate of the target vehicle.

[0092] The specific implementation can refer to step S103 described above, and will not be repeated here.

[0093] In step S304, the rear wheels of the target vehicle are controlled to steer according to the rear wheel steering mode and the rear wheel steering angle.

[0094] The specific implementation can refer to step S104 described above, and will not be repeated here.

[0095] In step S305, the road adhesion coefficient of the road on which the target vehicle is running is obtained by a tire force observer of the target vehicle.

[0096] In step S306, the weights of rear wheel steering control and brake control are adaptively adjusted according to the road adhesion coefficient and / or the vehicle speed of the road on which the target vehicle is running.

[0097] ​On low adhesion road surface (such as ice and snow, wet road surface, etc.), the rear wheel steering is used to assist in adjusting the vehicle trajectory, which can reduce the risk of tire lock caused by excessive intervention of the braking system and maintain a higher speed. On low adhesion road surface, steering intervention is less likely to cause tire slip than braking, and is safer. That is, on low adhesion road surface, the rear wheel steering control is preferred, which can effectively reduce the risk of slip caused by braking control.

[0098] In an optional embodiment, the weight of the rear wheel steering control and the braking control is adaptively adjusted according to the road surface adhesion coefficient and / or the speed of the target vehicle driving road surface, which can specifically include: when the road surface adhesion coefficient of the target vehicle driving road surface is less than a preset road surface adhesion coefficient threshold, and / or, the speed of the target vehicle is greater than a preset speed threshold, the weight of the rear wheel steering control is increased, and the weight of the braking control is reduced. The preset road surface adhesion coefficient threshold and the preset speed threshold in the embodiment can be calibrated when the vehicle is manufactured.

[0099] The vehicle control method based on rear wheel steering provided in the embodiment further adaptively adjusts the weight of the rear wheel steering control and the braking control according to the road surface adhesion coefficient and / or the speed of the target vehicle driving road surface, so that the rear wheel steering control is preferred to the braking control on low adhesion road surface, and the driving safety is further improved.

[0100] In summary, the vehicle control method based on rear wheel steering provided in the present application takes the rear wheel steering angle as the active control variable into the vehicle stability control system, breaks through the limitation of the traditional dependence on braking, can inhibit the excessive deviation of the vehicle yaw rate, prevent the occurrence of spin or understeering, can also control the vehicle lateral acceleration and side slip angle within a safe range, and can assist the vehicle in accurately following the driver's desired path through rear wheel steering. According to the speed and road surface state, an adaptive weight mechanism is used to dynamically adjust the cooperative proportion of rear wheel steering and braking, which improves the robustness of the system. The lateral force moment is generated by the rear wheel steering, which reduces the dependence on the braking system and prolongs the service life of the brake; on low adhesion road surface, steering intervention is less likely to cause tire slip than braking, and is safer; the vehicle body posture adjustment is smoother, and the driving comfort is improved.

[0101] The rear wheel steering based vehicle control method provided in the application can be executed by a vehicle stability control system, which comprises a plurality of sensors for collecting real-time state data of a target vehicle, an actuator, and a controller. The actuator is a rear wheel steering motor, the controller adopts vehicle motion control (VMC), and the plurality of sensors include a yaw rate sensor, a lateral acceleration sensor, a steering wheel angle sensor, a vehicle speed sensor, a wheel speed sensor, and the like. When the rear wheel steering based vehicle control method is executed, the following optimization and robustness measures can also be adopted: 1) tire nonlinear compensation: correcting the cornering stiffness by using a Dugoff tire model or a magic formula; 2) multi-objective coordinated control: cooperating with an electronic stability program (ESP) and superimposing brake intervention if necessary; and 3) robustness design: using a sliding mode control (SMC) or H-infinity control to cope with model uncertainty.

[0102] Further, CarSim + MATLAB / Simulink joint simulation can also be used to verify the performance of the rear wheel steering based vehicle control method provided in the application under the working conditions of emergency lane changing and double lane shifting. According to simulation verification, the rear wheel steering based vehicle control method provided in the application can control the yaw rate tracking error to be less than 10%, the absolute value of the side slip angle to be less than 5°, and the path tracking deviation to be less than 0.3 m.

[0103] The embodiment of the application further provides a rear wheel steering based vehicle control device, please refer to Figure 4 , Figure 4 is a structural block diagram of an embodiment of a rear wheel steering based vehicle control device of the application. The device can comprise a judgment module 401, a first processing module 402, a second processing module 403, and a control module 404.

[0104] The judgment module 401 is configured to determine whether a target vehicle is in an unstable state based on a two-degree-of-freedom vehicle dynamics model of the target vehicle.

[0105] The first processing module 402 is configured to determine a rear wheel steering mode according to a vehicle speed of the target vehicle when the target vehicle is in the unstable state.

[0106] The second processing module 403 is configured to determine a rear wheel steering angle by using a proportional-integral-derivative controller based on a deviation between an actual yaw rate and an expected yaw rate of the target vehicle.

[0107] The control module 404 is configured to control the rear wheel of the target vehicle to steer according to the rear wheel steering mode and the rear wheel steering angle.

[0108] The device of the embodiment can be used to executeFigure 1 The technical solutions of the method embodiments shown, the implementation principles and technical effects are similar, and details are not repeated here.

[0109] In an optional implementation, the first processing module 402 is configured to determine the rear wheel steering mode according to the vehicle speed of the target vehicle, and specifically can include:

[0110] When the vehicle speed of the target vehicle is less than a preset vehicle speed threshold, the rear wheel steering mode is opposite to the front wheel;

[0111] When the vehicle speed of the target vehicle is greater than or equal to the preset vehicle speed threshold, the rear wheel steering mode is the same as the front wheel.

[0112] In an optional implementation, the expected yaw rate of the target vehicle is determined according to the following expression:

[0113] ;

[0114] Wherein, represents the expected yaw rate, represents the vehicle speed, represents the wheelbase, represents the stability factor, represents the front wheel steering angle.

[0115] In an optional implementation, the rear wheel steering based vehicle control device can further include a limiting module configured to limit the rear wheel steering angle within a preset steering angle range before controlling the rear wheel of the target vehicle to steer according to the rear wheel steering mode and the rear wheel steering angle.

[0116] In an optional implementation, the rear wheel steering based vehicle control device can further include a correction module configured to correct the rear wheel steering angle according to the following expression when the center of mass side slip angle of the target vehicle is greater than a preset side slip angle threshold before controlling the rear wheel of the target vehicle to steer according to the rear wheel steering mode and the rear wheel steering angle:

[0117] ;

[0118] Wherein, represents the corrected rear wheel steering angle, represents the uncorrected rear wheel steering angle, represents the center of mass side slip angle coefficient, represents the center of mass side slip angle.

[0119] In one optional implementation, the vehicle control device based on rear-wheel steering may further include an adaptive module for obtaining the road surface adhesion coefficient of the target vehicle's driving surface through the tire force observer of the target vehicle; and adaptively adjusting the weights of rear-wheel steering control and braking control based on the road surface adhesion coefficient and / or vehicle speed of the target vehicle's driving surface.

[0120] In one optional implementation, the adaptive module is used to adaptively adjust the weights of rear-wheel steering control and braking control based on the road surface adhesion coefficient and / or vehicle speed of the target vehicle. Specifically, it may include:

[0121] When the road surface adhesion coefficient of the target vehicle is less than the preset road surface adhesion coefficient threshold, and / or the vehicle speed of the target vehicle is greater than the preset vehicle speed threshold, the weight of rear wheel steering control is increased and the weight of braking control is decreased.

[0122] Based on the same inventive concept, embodiments of the present invention also provide an electronic device. Figure 5 This is a structural block diagram of an electronic device provided in an embodiment of the present invention. Figure 5 As shown, an embodiment of the present invention provides an electronic device including: one or more processors 101, a memory 102, and one or more I / O interfaces 103. The memory 102 stores one or more programs, which, when executed by the one or more processors, cause the one or more processors to implement any of the rear-wheel steering-based vehicle control methods described in the above embodiments; the one or more I / O interfaces 103 are connected between the processors and the memory, configured to enable information interaction between the processors and the memory.

[0123] The processor 101 is a device with data processing capabilities, including but not limited to a central processing unit (CPU); the memory 102 is a device with data storage capabilities, including but not limited to random access memory (RAM, more specifically SDRAM, DDR, etc.), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), and flash memory (FLASH); the I / O interface (read / write interface) 103 is connected between the processor 101 and the memory 102, and can realize information interaction between the processor 101 and the memory 102, including but not limited to a data bus (Bus).

[0124] In some embodiments, the processor 101, memory 102, and I / O interface 103 are interconnected via bus 104, and thus connected to other components of the computing device.

[0125] In some embodiments, the one or more processors 101 include a field-programmable gate array.

[0126] The embodiment of the present application also provides a computer readable medium. The computer readable medium stores a computer program, wherein the program is executed by a processor to implement the steps in the vehicle control method based on rear wheel steering in any of the above embodiments. The computer readable storage medium can be a volatile or non-volatile computer readable storage medium.

[0127] The embodiment of the present application also provides a computer program product comprising computer readable code or a non-volatile computer readable storage medium carrying computer readable code, when the computer readable code is run in a processor of an electronic device, the processor in the electronic device executes the vehicle control method based on rear wheel steering.

[0128] Those skilled in the art can understand that all or some of the steps in the method disclosed above, the functional modules / units in the system and the device can be implemented as software, firmware, hardware and appropriate combinations thereof. In the hardware implementation, the division between the functional modules / units mentioned in the above description does not necessarily correspond to the division of physical components; for example, one physical component can have multiple functions, or one function or step can be performed by several physical components in cooperation. Some or all of the physical components can be implemented as software executed by a processor, such as a central processing unit, a digital signal processor or a microprocessor, or as hardware, or as an integrated circuit, such as an application specific integrated circuit. Such software can be distributed on a computer readable storage medium, which can include computer storage media (or non-transitory media) and communication media (or transitory media).

[0129] As known to those skilled in the art, the term computer storage media includes volatile and non-volatile, removable and non-removable media implemented in any method or technology for storage of information such as computer readable program instructions, data structures, program modules or other data. Computer storage media includes, but is not limited to, random access memory (RAM), read only memory (ROM), erasable programmable read only memory (EPROM), static random access memory (SRAM), flash memory or other memory technology, portable compact disc read only memory (CD-ROM), digital versatile disc (DVD) or other optical disk storage, magnetic cassettes, magnetic tapes, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to store the desired information and can be accessed by a computer. In addition, it is known to those skilled in the art that communication media typically includes computer readable program instructions, data structures, program modules or other data in modulated data signals such as carrier waves or other transport mechanisms, and can include any information delivery medium.

[0130] The computer readable program instructions described herein can be downloaded to respective computing / processing devices from a computer readable storage medium or to an external computer or external storage device via a network, for example, the Internet, a local area network, a wide area network and / or a wireless network. The network can comprise copper transmission cables, optical transmission fibers, wireless transmission, routers, firewalls, switches, gateway computers and / or edge servers. A network adapter card or network interface in each computing / processing device receives computer readable program instructions from the network and forwards the computer readable program instructions for storage in a computer readable storage medium within the respective computing / processing device.

[0131] Computer readable program instructions for carrying out operations of the present application can be assembler instructions, instruction-set-architecture (ISA) instructions, machine instructions, machine dependent instructions, microcode, firmware instructions, state-setting data, or either source code or object code written in any combination of one or more programming languages, including an object oriented programming language such as Smalltalk, C++ or the like, and conventional procedural programming languages, such as the "C" programming language or similar programming languages. The computer readable program instructions can execute entirely on the user's computing / processing device, partly on the user's computing / processing device, as a stand-alone software package, partly on the user's computing / processing device and partly on a remote computing / processing device or entirely on the remote computing / processing device or server. In the latter scenario, the remote computing / processing device can be connected to the user's computing / processing device through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection can be made to an external computing / processing device, for example, through the Internet using an Internet Service Provider. In some embodiments, electronic circuitry including, for example, programmable logic circuitry, field-programmable gate array (FPGA), or programmable logic array (PLA) can execute the computer readable program instructions by utilizing state information of the computer readable program instructions to personalize the electronic circuitry, in order to perform aspects of the present application.

[0132] The computer program product described herein can be embodied specifically by hardware, software or a combination thereof. In an alternative embodiment, the computer program product is embodied specifically as a computer storage medium, and in another alternative embodiment, the computer program product is embodied specifically as a software product, such as a software development kit (SDK) or the like.

[0133] The computer program product described herein can be embodied specifically by hardware, software or a combination thereof. In an alternative embodiment, the computer program product is embodied specifically as a computer storage medium, and in another alternative embodiment, the computer program product is embodied specifically as a software product, such as a software development kit (SDK) or the like.

[0134] These computer readable program instructions can be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions / acts specified in the flowchart and / or block diagram block or blocks. These computer readable program instructions can also be stored in a computer readable storage medium that can include a non-transitory computer readable storage medium that can be a computer- readable storage medium having no data storage cycles that change state. The instructions can be executed by one or more processors of a computer, other programmable data processing apparatus, or other devices to produce a computer-implemented process such that the instructions which execute via the one or more processors of the computer or other programmable data processing devices create means for implementing the functions / acts specified in the flowchart and / or block diagram block or blocks. The computer program instructions can also be loaded onto a computer, other programmable data processing apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatus or other devices to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide processes for implementing the functions / acts specified in the flowchart and / or block diagram block or blocks.

[0135] The computer readable program instructions can also be loaded onto a computer, other programmable data processing apparatus, or other device to cause a series of operational steps to be performed on the computer, other programmable apparatus or other device to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide processes for implementing the functions / acts specified in the flowchart and / or block diagram block or blocks.

[0136] The flow diagrams and the block diagrams in the drawings are presented to illustrate the architecture, functionality, and operation of possible implementations of systems, methods and computer program products according to the present application. In this regard, each block in the flow diagrams and the block diagrams can represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical functions ("instructions"). In some alternative implementations, the functions noted in the blocks can occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks can sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and / or flow diagrams, and combinations thereof, can be implemented by special purpose hardware-based systems that perform the specified functions or acts, or combinations of special purpose hardware and

[0137] Example embodiments have been disclosed and, although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation. In some instances, it will be apparent to those skilled in the art that features, characteristics or aspects described in relation to one embodiment can be applied to other embodiments, unless explicitly stated otherwise. Thus, it will be appreciated that various modifications can be made to the procedures described herein and still be within scope of the application as set forth in the appended claims.

Claims

1. A vehicle control method based on rear wheel steering, characterized by, The method comprises: determining whether the target vehicle is in an unstable state based on a two-degree-of-freedom vehicle dynamics model of the target vehicle; when the target vehicle is in an unstable state, determining a rear wheel steering mode according to a vehicle speed of the target vehicle; determining a rear wheel steering angle based on a deviation between an actual yaw rate and an expected yaw rate of the target vehicle using a proportional-integral-derivative controller; controlling the rear wheel of the target vehicle to steer according to the rear wheel steering mode and the rear wheel steering angle.

2. The method of claim 1, wherein, The step of determining the rear wheel steering mode according to the vehicle speed of the target vehicle comprises: when the vehicle speed of the target vehicle is less than a preset vehicle speed threshold, the rear wheel steering mode is opposite to that of the front wheel; when the vehicle speed of the target vehicle is greater than or equal to the preset vehicle speed threshold, the rear wheel steering mode is the same as that of the front wheel.

3. The method of claim 1, wherein, The expected yaw rate of the target vehicle is determined according to the following expression: ； wherein, represents a desired yaw rate, represents a vehicle speed, represents a wheelbase, represents a stability factor, represents a front wheel steering angle.

4. The method of claim 1, wherein, Before the step of controlling the rear wheel of the target vehicle to steer according to the rear wheel steering mode and the rear wheel steering angle, the method further comprises: limiting the rear wheel steering angle within a preset steering angle range.

5. The method of claim 1, wherein, Before the step of controlling the rear wheel of the target vehicle to steer according to the rear wheel steering mode and the rear wheel steering angle, the method further comprises: when a center of mass side slip angle of the target vehicle is greater than a preset side slip angle threshold, correcting the rear wheel steering angle according to the following expression: ； wherein, represents the corrected rear wheel steering angle, represents the uncorrected rear wheel steering angle, represents the center of mass side slip angle coefficient, represents the center of mass side slip angle.

6. The method according to any one of claims 1 to 5, characterized in that, The method further comprises: obtaining a road surface adhesion coefficient of a road surface on which the target vehicle travels through a tire force observer of the target vehicle; adaptively adjusting a weight of rear wheel steering control and brake control according to the road surface adhesion coefficient and / or the vehicle speed of the target vehicle.

7. The method of claim 6, wherein, The step of adaptively adjusting the weight of rear wheel steering control and brake control according to the road surface adhesion coefficient and / or the vehicle speed of the target vehicle comprises: when the road surface adhesion coefficient of the target vehicle is less than a preset road surface adhesion coefficient threshold, and / or, the vehicle speed of the target vehicle is greater than a preset vehicle speed threshold, increasing the weight of rear wheel steering control and decreasing the weight of brake control.

8. A vehicle control device based on rear wheel steering, characterized by The method comprises: a determining module configured to determine whether the target vehicle is in an unstable state based on a two-degree-of-freedom vehicle dynamics model of the target vehicle; a first processing module configured to determine a rear wheel steering mode according to a vehicle speed of the target vehicle when the target vehicle is in an unstable state; a second processing module configured to determine a rear wheel steering angle based on a deviation between an actual yaw rate and an expected yaw rate of the target vehicle using a proportional-integral-derivative controller; a control module configured to control the rear wheel of the target vehicle to steer according to the rear wheel steering mode and the rear wheel steering angle.

9. An electronic device, comprising: The method comprises: one or more processors; a memory configured to store one or more programs; when the one or more programs are executed by the one or more processors, the one or more processors implement the method according to any one of claims 1 to 7.

10. A computer readable medium having stored thereon a computer program, characterized in that The computer program, when executed by a processor, implements the steps of the method according to any one of claims 1 to 7.

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