Vehicle active rear wheel steering control method under emergency obstacle avoidance working condition

Abstract

The invention discloses a vehicle active rear wheel steering control method under an emergency obstacle avoidance working condition, which comprises the following steps of: firstly, dynamically optimizing safety boundary thresholds of a side slip angle and a yaw velocity based on collision time prediction and a real-time road adhesion state, and accurately judging a rear wheel steering intervention opportunity by constructing a phase plane trigger logic; according to the nonlinear characteristic of the limiting working condition, sliding mode control parameters are adjusted in real time according to the road adhesion coefficient and the vehicle speed, high-precision tracking control over rear wheel steering is achieved in combination with an anti-interference compensation mechanism, system buffeting is synchronously restrained, and the tire lateral force saturation boundary is maintained. Through a double-layer cooperation mechanism of dynamic safety decision and self-adaptive control, the emergency obstacle avoidance response precision is remarkably improved, and the safety and the control stability of the vehicle under the limiting working conditions of low-adhesion road surfaces, high-speed instability and the like are effectively enhanced.

Description

Technical Field

[0001] The present invention relates to the field of vehicle dynamics control, and in particular to a vehicle active rear wheel steering control method for emergency obstacle avoidance conditions. Background Art

[0002] As smart car applications expand into complex environments, the need for vehicle stability control in extreme conditions, such as low-adhesion roads and high-speed emergency obstacle avoidance, is becoming increasingly urgent. Current mainstream solutions, such as direct yaw moment control (DYC), rely on the braking system's differential pressure torque to adjust vehicle posture. However, this adjustment capability is significantly reduced due to tire lateral force saturation in low-adhesion conditions, and frequent braking exacerbates the risk of longitudinal instability. Active front steering (AFS) can correct for path deviations, but its mechanical transmission delay and road feel interference make it difficult to meet real-time requirements and human-machine collaboration. Existing rear-wheel active steering (ARS) control methods, while mitigating front-wheel road feel interference, are still limited by static threshold decision boundaries, fixed parameter control modes, and multi-actuator coordination conflicts. These factors lead to problems such as inaccurate steering intervention timing in low-adhesion conditions, delayed response in complex scenarios, and control command oscillation. Therefore, a rear-wheel steering control method that can dynamically integrate multi-source risk signals, adaptively decouple control parameters, and ensure actuator coordination stability is urgently needed to overcome the dual constraints of existing technologies in terms of response accuracy and robustness in extreme conditions. Summary of the Invention

[0003] In order to overcome the shortcomings of the existing technology, the present invention proposes a vehicle active rear-wheel steering control method for emergency obstacle avoidance conditions, so as to be able to define the vehicle safety boundary in real time through collision time and road adhesion coefficient, thereby accurately triggering rear-wheel steering intervention, optimizing yaw control, and solving the problems of inaccurate steering intervention timing, low-adhesion road control oscillation, and multi-actuator collaborative conflict in existing active collision avoidance systems.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions: The present invention provides a method for controlling active rear wheel steering of a vehicle in an emergency obstacle avoidance condition, which comprises the following steps: Step 1: Use the vehicle-mounted millimeter-wave radar to measure the relative distance to the obstacle ahead and relative speed ; Use the camera to identify the type of obstacle ahead T; Using the vehicle-mounted inertial measurement unit to collect vehicle lateral acceleration and yaw rate ; Detecting road adhesion coefficient using road adhesion coefficient observer ; The vehicle speed is collected by using the vehicle speed sensor, center of mass side slip angle sensor and steering wheel angle sensor respectively , center of mass side slip angle and front wheel steering angle ; Step 2: Based on the relative distance of the obstacle in front and relative speed , calculate the collision time TTC; Calculate the desired yaw rate based on the two-degree-of-freedom dynamic model of a front-wheel steering vehicle ; Based on the two-degree-of-freedom dynamic model of the four-wheel steering vehicle, the center of mass side slip angle is established and yaw rate The phase plane; Step 3: Based on the collision time TTC and the road adhesion coefficient And the type of obstacle in front T, calculate the center of mass sideslip angle threshold and yaw rate boundary threshold , so that the sideslip angle at the center of mass and yaw rate Define the vehicle safety boundary within the phase plane; Step 4: The center of mass side slip angle and yaw rate Compare with the vehicle's safety margin to determine the steering mode: When the real-time measured center of mass side slip angle and yaw rate If the vehicle is within the safety boundary, the front wheel steering mode of step 5 is executed; otherwise, the active rear wheel steering mode of step 6 is executed; Step 5: Control the front wheel steering angle by turning the steering wheel To control the direction of vehicle travel; Step 6: Control the front wheel steering angle by turning the steering wheel Direct vehicle direction, based on real-time road adhesion coefficient and vehicle speed The dual-factor dynamic adjustment of the sliding mode gain is achieved by integrating the desired yaw rate and vehicle lateral acceleration The anti-interference sliding mode control algorithm can accurately calculate the rear wheel steering angle .

[0005] The method for controlling active rear wheel steering of a vehicle in an emergency obstacle avoidance condition according to the present invention is also characterized in that, in step 3, the vehicle safety margin is determined according to the following process: Step 3.1: If the type of obstacle T is a pedestrian, let the first weight coefficient be , the second weight coefficient = ; If T is the vehicle type, let the first weight coefficient be , the second weight coefficient = ; If T is the object type, let the first weight coefficient be , the second weight coefficient = ,in, 、 、 are three coefficients, and ; Step 3.2: Calculate the real-time risk index R using formula (1): (1) In formula (1), is the engineering smoothing constant; Step 3.3: Calculate the center of mass sideslip angle boundary value using formula (2) and yaw rate boundary value : (2) In formula (2), represents the acceleration due to gravity, 、 、 、 are 4 constant coefficients; Step 3.4: Positive and negative boundary values ​​of the center of mass sideslip angle and the positive and negative boundary values ​​of the yaw rate Constitute the vehicle safety boundary.

[0006] Furthermore, in step 6, the rear wheel steering angle is calculated as follows: : Step 6.1: Use formula (3) to construct the sliding surface : (3) In formula (3), is the convergence rate coefficient; Step 6.2: Use formula (4) to get the first sliding mode gain and the second sliding mode gain : (4) In formula (4), is the gain coefficient, N is the friction attenuation coefficient, P is the speed proportional factor; Step 6.3: Use formula (5) to get the rear wheel steering angle : (5) In formula (5), is the rear wheel cornering stiffness, is the horizontal distance from the front and rear axles to the center of mass, is the vehicle mass, is the smoothing coefficient, Represents a symbolic function.

[0007] The present invention provides an electronic device, comprising a memory and a processor, wherein the memory is used to store a program that supports the processor to execute the vehicle active rear wheel steering control method, and the processor is configured to execute the program stored in the memory.

[0008] The present invention provides a computer-readable storage medium having a computer program stored thereon. The computer-readable storage medium is characterized in that when the computer program is run by a processor, the steps of the vehicle active rear wheel steering control method are executed.

[0009] Compared with the prior art, the beneficial effects of the present invention are embodied in: 1. This invention proposes a vehicle active rear-wheel steering control method for emergency obstacle avoidance. By integrating the time-to-collision (TTC) and the road adhesion coefficient to construct a dynamic safety margin, and employing a phase plane compression algorithm based on a risk index, it enables precise decision-making regarding the timing of rear-wheel steering intervention. Compared to traditional static threshold methods, this method can adaptively adjust the safety thresholds for the sideslip angle and yaw rate based on real-time road conditions and obstacle types, significantly reducing steering trigger errors on low-adhesion roads and collision avoidance response delays in complex scenarios. 2. The present invention proposes a dual-domain adaptive mechanism for sliding mode gain, which dynamically adjusts control parameters based on vehicle speed and road adhesion coefficient. It uses fuzzy logic to coordinate braking and rear-wheel steering to solve stability constraints in real time. It effectively suppresses sliding mode control chatter on low-adhesion roads and optimizes yaw rate tracking accuracy under high-speed conditions. This solves the technical limitations of traditional fixed-parameter sliding mode control in terms of actuator coordination and stability constraint decoupling. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 This is a control flow chart of the steering controller of the present invention; Figure 2 This is the phase plane safety boundary division diagram of the present invention. DETAILED DESCRIPTION

[0011] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0012] In this embodiment, a vehicle active rear wheel steering control method for emergency obstacle avoidance conditions is provided. Figure 1 The specific implementation steps are as follows: Step 1: Use the vehicle-mounted millimeter-wave radar to measure the relative distance of the obstacle in front using formula (1) and relative speed ; (1) Use the camera to identify the type of obstacle ahead T; Using the vehicle-mounted inertial measurement unit to collect vehicle lateral acceleration and yaw rate ; Detecting road adhesion coefficient using road adhesion coefficient observer ; The vehicle speed is collected by using the vehicle speed sensor, center of mass side slip angle sensor and steering wheel angle sensor respectively , center of mass side slip angle and front wheel steering angle .

[0013] Step 2: Based on the relative distance of the obstacle in front and relative speed , calculate the collision time TTC; Calculate the desired yaw rate based on the two-degree-of-freedom dynamic model of a front-wheel steering vehicle ; In the specific implementation, based on the two-degree-of-freedom dynamic model of the four-wheel steering vehicle as shown in Equation (2), and organized into a state space form, the chain rule is used to establish a phase plane with the sideslip angle of the center of mass as the horizontal coordinate and the yaw angular velocity as the vertical coordinate, see Figure 2 : (2) in, is the vehicle mass, is the yaw moment of inertia, is the front wheelbase, is the rear wheelbase, is the front wheel cornering stiffness, is the rear wheel cornering stiffness, is the front wheel turning angle, is the rear wheel turning angle.

[0014] Based on the two-degree-of-freedom dynamic model of the four-wheel steering vehicle, the center of mass side slip angle is established and yaw rate The phase plane; In the specific implementation, based on the two-degree-of-freedom dynamic model of the front-wheel steering vehicle as shown in formula (3), the expected yaw rate is calculated ; (3) In formula (3), is the vehicle mass, is the vehicle speed, is the vehicle's sideslip angle, is the vehicle yaw angular velocity, 、 is the vehicle sideslip angle, , , is the horizontal distance from the front and rear axles to the center of mass, is the rear wheel cornering stiffness, is the yaw moment of inertia; (4) In formula (4), is the horizontal distance from the front and rear axles to the center of mass, is the vehicle understeering gradient, which is expressed as .

[0015] Step 3: Based on the collision time TTC and the road adhesion coefficient And the type of obstacle in front T, calculate the center of mass sideslip angle threshold and yaw rate boundary threshold , so that the sideslip angle at the center of mass and yaw rate The vehicle safety boundary is defined in the phase plane.

[0016] Step 3.1: If the type of obstacle T is a pedestrian, let the first weight coefficient be , the second weight coefficient = ; If T is the vehicle type, let the first weight coefficient be , the second weight coefficient = ; If T is the object type, let the first weight coefficient be , the second weight coefficient = ,in, 、 、 are three coefficients, and ; Step 3.2: Calculate the real-time risk index R using formula (5): (5) In formula (5), is the engineering smoothing constant; Step 3.3: Calculate the center of mass sideslip angle boundary value using formula (6) and yaw rate boundary value : (6) In formula (2), represents the acceleration due to gravity, 、 、 、 are 4 constant coefficients; Step 3.4: The positive and negative boundary values ​​of the center of mass sideslip angle and the positive and negative boundary values ​​of the yaw rate Constitutes the vehicle safety boundary, see Figure 2 , area A is the vehicle safety boundary.

[0017] Step 4: The center of mass side slip angle and yaw rate Compare with the vehicle's safety margin to determine the steering mode: When the real-time measured center of mass side slip angle and yaw rate If the vehicle is within the safety boundary, the front wheel steering mode of step 5 is executed; otherwise, the active rear wheel steering mode of step 6 is executed.

[0018] Step 5: Control the front wheel steering angle by turning the steering wheel To control the direction of vehicle travel; Step 6: Control the front wheel steering angle by turning the steering wheel Direct vehicle direction, based on real-time road adhesion coefficient and vehicle speed The dual-factor dynamic adjustment of the sliding mode gain is achieved by integrating the desired yaw rate and vehicle lateral acceleration The anti-interference sliding mode control algorithm can accurately calculate the rear wheel steering angle .

[0019] Step 6.1: Use formula (7) to construct the sliding surface : (7) In formula (7), is the convergence rate coefficient; Step 6.2: Use formula (8) to get the first sliding mode gain and the second sliding mode gain : (8) In formula (8), is the gain coefficient,N is the friction attenuation coefficient, P is the speed proportional factor; Step 6.3: Use formula (9) to get the rear wheel steering angle : (9) In formula (9), is the rear wheel cornering stiffness, is the horizontal distance from the front and rear axles to the center of mass, is the vehicle mass, is the smoothing coefficient, Represents a symbolic function.

[0020] In this embodiment, an electronic device includes a memory and a processor, wherein the memory is used to store a program that supports the processor to execute the above method, and the processor is configured to execute the program stored in the memory.

[0021] In this embodiment, a computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the above method are executed.

Claims

1. A vehicle active rear wheel steering control method for emergency obstacle avoidance conditions, characterized in that: The steps include: Step 1: Use the vehicle-mounted millimeter-wave radar to measure the relative distance to the obstacle ahead and relative speed ; Use the camera to identify the type of obstacle ahead T; Using the vehicle-mounted inertial measurement unit to collect vehicle lateral acceleration and yaw rate ; Detecting road adhesion coefficient using road adhesion coefficient observer ; The vehicle speed is collected by using the vehicle speed sensor, center of mass side slip angle sensor and steering wheel angle sensor respectively , center of mass side slip angle and front wheel steering angle ; Step 2: Based on the relative distance of the obstacle in front and relative speed , calculate the collision time TTC; Calculate the desired yaw rate based on the two-degree-of-freedom dynamic model of a front-wheel steering vehicle ; Based on the two-degree-of-freedom dynamic model of the four-wheel steering vehicle, the center of mass side slip angle is established and yaw rate The phase plane; Step 3: Based on the collision time TTC and the road adhesion coefficient And the type of obstacle in front T, calculate the center of mass side slip angle threshold and yaw rate boundary threshold , so that the sideslip angle at the center of mass and yaw rate Define the vehicle safety boundary within the phase plane; Step 4: The center of mass side slip angle and yaw rate Compare with the vehicle's safety margin to determine the steering mode: When the real-time measured center of mass side slip angle and yaw rate If the vehicle is within the safety boundary, the front wheel steering mode of step 5 is executed; otherwise, the active rear wheel steering mode of step 6 is executed; Step 5: Control the front wheel steering angle by turning the steering wheel To control the direction of vehicle travel; Step 6: Control the front wheel steering angle by turning the steering wheel Direct vehicle direction, based on real-time road adhesion coefficient and vehicle speed The dual-factor dynamic adjustment of the sliding mode gain is achieved by integrating the desired yaw rate and vehicle lateral acceleration The anti-interference sliding mode control algorithm can accurately calculate the rear wheel steering angle .

2. The method for controlling vehicle active rear wheel steering in an emergency obstacle avoidance situation according to claim 1, wherein: In step 3, the vehicle safety boundary is determined according to the following process: Step 3.1: If the type of obstacle T is a pedestrian, let the first weight coefficient be , the second weight coefficient = ; If T is the vehicle type, let the first weight coefficient be , the second weight coefficient = ; If T is the object type, let the first weight coefficient be , the second weight coefficient = ,in, 、 、 are three coefficients, and ; Step 3.2: Calculate the real-time risk index R using formula (1): (1) In formula (1), is the engineering smoothing constant; Step 3.3: Calculate the center of mass sideslip angle boundary value using formula (2) and yaw rate boundary value : (2) In formula (2), represents the acceleration due to gravity, 、 、 、 are 4 constant coefficients; Step 3.4: Positive and negative boundary values ​​of the center of mass sideslip angle and the positive and negative boundary values ​​of the yaw rate Constitute the vehicle safety boundary.

3. The vehicle active rear wheel steering control method for emergency obstacle avoidance according to claim 1, wherein: In step 6, the rear wheel steering angle is calculated as follows: : Step 6.1: Use formula (3) to construct the sliding surface : (3) In formula (3), is the convergence rate coefficient; Step 6.2: Use formula (4) to get the first sliding mode gain and the second sliding mode gain : (4) In formula (4), is the gain coefficient, N is the friction attenuation coefficient, P is the speed proportional factor; Step 6.3: Use formula (5) to get the rear wheel steering angle : (5) In formula (5), is the rear wheel cornering stiffness, is the horizontal distance from the front and rear axles to the center of mass, is the vehicle mass, is the smoothing coefficient, Represents a symbolic function.

4. An electronic device comprising a memory and a processor, characterized in that: The memory is used to store a program that supports the processor to execute the vehicle active rear wheel steering control method according to any one of claims 1 to 3, and the processor is configured to execute the program stored in the memory.

5. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the vehicle active rear wheel steering control method according to any one of claims 1 to 3 are executed.

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