Cross-system redundancy brake control method for all-working-condition brake safety

Abstract

The invention discloses a cross-system redundant braking control method for all-working-condition braking safety. According to the cross-system redundant braking control method, the turning angle of wheels can be controlled through a four-wheel independent steering system to achieve cross-system redundant braking under the working condition of vehicle turning or linear braking. Comprising the steps that when only a front wheel braking system breaks down, cross-system redundant braking is carried out based on a front wheel steering system, and turning control can be carried out based on a rear wheel steering system to maintain an original traveling track. When the front and rear wheel braking systems fail, under the small braking force linear working condition, only the front wheel steering system conducts cross-system redundant braking; under the large braking force linear working condition, the front wheel steering system and the rear wheel steering system conduct cross-system redundant braking, the stability of the vehicle is monitored in real time, and if the vehicle has the instability risk, the cross-system redundant braking of the rear wheel steering system is canceled; when cross-system redundant braking is carried out under the turning working condition, cross-system redundant braking needs to be carried out only on the basis of a front wheel steering system, and meanwhile vehicle turning control is carried out on the basis of a rear wheel steering system to maintain an original traveling track.

Description

Technical Field

[0001] This invention belongs to the field of automotive drive-by-wire chassis, and specifically relates to a cross-system redundant braking control method for all-condition braking safety. Background Technology

[0002] In recent years, the intelligent connected electric vehicle industry has accelerated its rise, and the market has placed higher demands on vehicle chassis technology. Drive-by-wire chassis technology, with its high control precision, rapid response capabilities, and flexible control freedom, is experiencing explosive demand growth. Among these technologies, drive-by-wire steering technology, with four-wheel independent steering at its core, stands out. It not only precisely matches the stringent control precision standards of autonomous driving but also significantly improves vehicle handling stability in complex road conditions, making it the mainstream development direction for future automotive chassis technology.

[0003] While drive-by-wire chassis technology replaces traditional mechanical connections with electronic components, achieving control decoupling and optimizing handling logic, it also exposes a weakness in reliability. For example, in widely used brake-by-wire technology, a malfunction in the brake actuator can easily lead to a decrease in vehicle braking force, and in critical situations such as emergency braking, it may even result in a complete loss of safe braking capability, directly threatening the lives of passengers.

[0004] To address this pain point, the industry has begun relevant explorations. Some companies and scholars have adopted a solution of adding backup braking actuators to provide redundant braking force, but this would significantly increase vehicle production and manufacturing costs. Other studies have attempted to achieve redundant control through the electric braking torque of the drive motor, but this is limited by insufficient peak electric braking torque and the inability to be activated under certain operating conditions. Moreover, this solution is only applicable to drive axles or electric wheels equipped with electric drive systems, and it is difficult to form effective redundant protection for driven axles and driven wheels, resulting in significant limitations in application scenarios.

[0005] To address the aforementioned issues, this paper proposes a cross-system redundant braking control method for all-condition braking safety. Considering the stability requirements of vehicle cornering and straight-line braking, this method leverages the advantages of the four-wheel independent steering system in controlling large wheel steering angles to actively adjust the tire slip angle, thereby generating redundant braking force through tire lateral force. Summary of the Invention

[0006] The purpose of this invention is to propose a cross-system redundant braking control method for all-condition braking safety. It can generate redundant braking force in the vehicle's forward direction by controlling the wheel angle through a four-wheel independent steering system, and meet the stability requirements under turning and straight-line braking conditions, thereby effectively realizing cross-system redundant braking control of the brake-by-wire system.

[0007] To achieve the above objectives, the following technical solution is adopted:

[0008] A cross-system redundant braking control method for all-condition braking safety is characterized by comprising:

[0009] The vehicle controller determines in real time whether the front wheel braking system and the rear wheel braking system have failed. If both the front wheel braking system and the rear wheel braking system fail, or only the front wheel braking system fails, the cross-system redundant braking control method for all-condition braking safety is executed.

[0010] When only the front wheel braking system fails, the vehicle controller controls the left front steering system and the right front steering system to simultaneously generate θ. bfl θ bfr The wheel steering angle, where θ bfl =-θ bfr To maximize the braking requirements of the vehicle; wherein, when the front wheel braking system fails during cornering, the vehicle controller only controls the left front steering system and the right front steering system for cross-system redundant braking control, generating θ respectively. bfl θ bfr The wheel steering angle, where θ bfl =-θ bfr The vehicle controller controls the left rear steering system and the right rear steering system to control the vehicle's turning trajectory in order to follow the driver's desired turning trajectory. At this time, the left rear braking system and the right rear braking system can perform a certain degree of mechanical braking while ensuring the vehicle's turning control, so as to meet the vehicle's braking needs to the maximum extent.

[0011] When both the front and rear braking systems fail, under low braking force demand in a straight line, the vehicle controller only controls the left front steering system and the right front steering system for cross-system redundant braking control, generating θ respectively. bfl θ bfr The wheel steering angle, where θ bfl =-θ bfr To meet braking requirements; under high braking force demand in straight-line conditions, the vehicle controller controls the left front steering system, the right front steering system, the left rear steering system, and the right rear steering system to perform cross-system redundant braking control, generating θ respectively. bfl θ bfr θ brl θ brr The wheel steering angle, where θ bfl =-θ bfr θ brl =-θ brrWhen the left rear steering system and the right rear steering system perform cross-system redundant straight-line braking control, the vehicle controller needs to monitor the vehicle's stability in real time. If the vehicle is at risk of instability due to disturbance or the trajectory tracking deviation is too large, the cross-system redundant braking control based on the left rear steering system and the right rear steering system needs to be canceled. When the front wheel braking system and the rear wheel braking system fail during cornering, the vehicle controller only controls the left front steering system and the right front steering system to perform cross-system redundant braking control, generating θ respectively. bfl θ bfr The wheel steering angle, where θ bfl =-θ bfr The vehicle controller controls the left rear steering system and the right rear steering system to control the vehicle's turning trajectory in order to follow the driver's desired turning path.

[0012] The vehicle controller can receive steering commands from the driver or autonomous driving system in real time, with the steering wheel input angle δ. s With the desired rear wheel steering angle θ sr0 The following relationship exists:

[0013] Low-speed range (v≤v1):

[0014]

[0015] Transition interval (v1) <v<v2):

[0016]

[0017] High-speed range (v≥v2):

[0018]

[0019] Where, δ f For the steering angle of the car's front wheels, to meet (i is the steering system transmission ratio), v is the vehicle speed, v1 is the critical speed of the low-speed transition zone, v2 is the critical speed of the transition zone to high-speed. max k1 and k2 represent the maximum speed of the car, and k1 and k2 are the basic ratio coefficients for low speed and high speed. This is the correction factor for the steering angular velocity. k is the lateral acceleration correction factor. z This is the load distribution correction factor;

[0020] The following strategy is used to output the steering angle θ for the left rear steering system and the right rear steering system. srl * θ srr * Make real-time adjustments;

[0021] The vehicle controller can collect the vehicle's center of gravity position (x, y), center of gravity sideslip angle β, longitudinal vehicle speed v, and yaw rate ω; and obtain the reference lateral and longitudinal coordinates (x, y) required for the vehicle to achieve trajectory tracking. r ,,y r Reference centroid sideslip angle β r Reference yaw rate ω r The method is built into the vehicle controller;

[0022] A PID control strategy is used to calculate the rear wheel output steering angle to track the target driving trajectory.

[0023]

[0024] Where e represents the trajectory tracking deviation, including: lateral position deviation e y =y r -y, the deviation of the centroid side slip angle is e β =β r -β and the deviation of yaw rate are e ω =ω r -ω;δ θ δ is the deviation between the actual rear wheel steering angle and the desired rear wheel steering angle. θ =θ sr * -θ sr0 ;k p k i k d These are the proportional, integral, and derivative control coefficients, which are adjusted and calibrated by the vehicle under normal driving conditions on a good road surface and then stored in the vehicle controller.

[0025] To prevent overload of the vehicle steering system and vehicle instability, the output is saturated and limited:

[0026] Maximum rear wheel steering angle: |θ sr * |≤θ sr ** Maximum steering angular velocity: Steady-state control objective: |e y |≤e y * or |e β |≤e β * or |e ω |≤e ω * 、|δ θ |≤δ θ * ;

[0027] During the implementation of the control strategy, a cyclic correction is performed every time interval t, and the actual trajectory deviation is fed back to the vehicle controller in real time to dynamically update the parameters and output steering angle θ. sr * .

[0028] The θ bfl θ bfr θ brl θ brr The size can be obtained by looking up a table, as follows:

[0029] The following relationship exists during redundant braking:

[0030] F y-0 (|θ bf |)·sin|θ bf |=F bfw0

[0031] F y-0 (|θ br |)·sin|θ br |=F brw0

[0032] |θ bfl |=|θ bfr |=|θ bf |

[0033] |θ brl |=|θ brr |=|θ br |

[0034] In the formula, F y-0 (|θ bij |) represents the left front wheel, the right front wheel, the left rear wheel, or the right rear wheel at the current sideslip angle |θ. bij The reference lateral force generated under | can be experimentally determined at the reference load. Calibration was performed at the specified road surface adhesion coefficient μ0, F bfw0 With F brw0 To the current sideslip angle |θ bij The redundant braking force generated by the front and rear wheels can be uniformly expressed as F. bw0 m is the mass of the car, g is the acceleration due to gravity, and L is the acceleration due to gravity. * L is the distance from the car's center of gravity to the rear or front axle, where L is the wheelbase.

[0035] F can be obtained from the above formula. bw0 With |θ bij The relationship table is F. bw0 =Curve{|θ bijThe calibration results are stored in the vehicle controller.

[0036] According to the braking force requirement F of the left front wheel and the right front wheel bFL F bFR The θ can be obtained in real time by looking up the table based on the following formula. bfl With the θ bfr Size,

[0037]

[0038] |θ bfl |=|θ bfr |=|θ bfr |

[0039] According to the braking force requirement F of the left rear wheel and the right rear wheel bRL F bRR The θ can be obtained in real time by looking up the table based on the following formula. brl With the θ brr Size,

[0040]

[0041] |θ brl |=|θ brr |=|θ br |

[0042] In the formula, μ is the actual ground adhesion coefficient, and a x Let h be the longitudinal acceleration of the vehicle, and h be the height of the vehicle's center of gravity.

[0043] The beneficial effects of this invention are:

[0044] 1. The cross-system redundant braking control method for all-condition braking safety described in this invention can achieve redundant braking control based on a four-wheel independent steering system without the need for additional brake-by-wire actuator backup, thus reducing vehicle manufacturing costs.

[0045] 2. The cross-system redundant braking control method for all-condition braking safety described in this invention can meet the turning braking requirements and straight-line braking stability requirements of a vehicle under mechanical braking system failure conditions based on a four-wheel independent steering system, and can achieve a large redundant braking force, which can meet the braking force requirements under emergency braking conditions, thereby effectively improving the active safety of the vehicle. Attached Figure Description

[0046] Figure 1 This is a simplified diagram of the vehicle configuration for the cross-system redundant braking control method for all-condition braking safety described in this invention.

[0047] Figure 2This invention provides a redundant control flow for the simultaneous failure of the front and rear wheel braking systems in a cross-system redundant braking control method for all-condition braking safety. Figure 1 .

[0048] Figure 3 The control flow of the redundant braking control method of the present invention, which considers cornering and stability and includes active sideslip angle adjustment for front wheel braking system failure, is as follows: Figure 2 .

[0049] Figure 4 This is a schematic diagram of a four-wheel steering direction control method within the cross-system redundant braking control method for all-condition braking safety described in this invention.

[0050] Figure 5 This is a schematic diagram of the second four-wheel steering direction control method of the cross-system redundant braking control method for all-condition braking safety described in this invention.

[0051] Figure 6 This is a schematic diagram of the four-wheel steering direction control method of the cross-system redundant braking control method for all-condition braking safety described in this invention.

[0052] Figure 7 This is a schematic diagram of the four-wheel steering direction control method of the cross-system redundant braking control method for all-condition braking safety described in this invention.

[0053] Figure 8 This is a schematic diagram of the four-wheel steering direction control method of the cross-system redundant braking control method for all-condition braking safety described in this invention.

[0054] Figure 9 This is a schematic diagram of the four-wheel steering direction control method of the cross-system redundant braking control method for all-condition braking safety described in this invention. Detailed Implementation

[0055] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0056] A cross-system redundant braking control method for all-condition braking safety is characterized by comprising:

[0057] like Figure 1 As shown, the method is used in the vehicle braking control process and is applicable to a four-wheel distributed independent steering vehicle configuration, which includes: left front wheel 201, right front wheel 202, left rear wheel 203, right rear wheel 204, vehicle steering system 400, vehicle braking system 300, steering controller 103, brake controller 102, and vehicle controller 101.

[0058] The vehicle steering system 400 includes a left front steering system 410, a right front steering system 420, a left rear steering system 430, and a right rear steering system 440. The vehicle braking system 300 includes a left front braking system 310, a right front braking system 320, a left rear braking system 330, and a right rear braking system 340.

[0059] The left front steering system 410 consists of a left front steering knuckle 411, a left front steering tie rod 412, and a left front steering actuator 413. The left front steering knuckle 411 is connected to the left front wheel 201, and the left front steering tie rod 412 is connected to the left front steering knuckle 411 and the left front steering actuator 413 through a ball joint. The left front steering actuator 413 can drive the left front steering knuckle 411 to rotate around the kingpin through the left front steering tie rod 412, thereby realizing the steering control of the left front wheel 201.

[0060] The right front steering system 420 consists of a right front steering knuckle 421, a right front steering tie rod 422, and a right front steering actuator 423. The right front steering knuckle 421 is connected to the right front wheel 202, and the right front steering tie rod 422 is connected to the right front steering knuckle 421 and the right front steering actuator 423 through a ball joint. The right front steering actuator 423 can drive the right front steering knuckle 421 to rotate around the kingpin through the right front steering tie rod 422, thereby realizing the steering control of the right front wheel 202.

[0061] The left rear steering system 430 consists of a left rear steering knuckle 431, a left rear steering tie rod 432, and a left rear steering actuator 433. The left rear steering knuckle 431 is connected to the left rear wheel 203, and the left rear steering tie rod 432 is connected to the left rear steering knuckle 431 and the left rear steering actuator 433 through a ball joint. The left rear steering actuator 433 can drive the left rear steering knuckle 431 to rotate around the kingpin through the left rear steering tie rod 432, thereby realizing the steering control of the left rear wheel 203.

[0062] The right rear steering system 440 consists of a right rear steering knuckle 441, a right rear steering tie rod 442, and a right rear steering actuator 443. The right rear steering knuckle 441 is connected to the right rear wheel 204, and the right rear steering tie rod 442 is connected to the right rear steering knuckle 441 and the right rear steering actuator 443 through a ball joint. The right rear steering actuator 443 can drive the right rear steering knuckle 441 to rotate around the kingpin through the right rear steering tie rod 442, thereby realizing the steering control of the right rear wheel 204.

[0063] The left front braking system 310 includes a left front brake 311 and a left front brake disc 312, wherein the left front brake disc 312 is fixedly connected to the left front wheel 201, and the left front brake 311 can generate a corresponding braking force on the left front wheel 201 by clamping the left front brake disc 312.

[0064] The right front braking system 320 includes a right front brake 321 and a right front brake disc 322, wherein the right front brake disc 322 is fixedly connected to the right front wheel 202, and the right front brake 321 can generate a corresponding braking force on the right front wheel 202 by clamping the right front brake disc 322.

[0065] The left rear braking system 330 includes a left rear brake 331 and a left rear brake disc 332, wherein the left rear brake disc 332 is fixedly connected to the left rear wheel 203, and the left rear brake 331 can generate a corresponding braking force on the left rear wheel 203 by clamping the left rear brake disc 332.

[0066] The right rear braking system 340 includes a right rear brake 341 and a right rear brake disc 342, wherein the right rear brake disc 342 is fixedly connected to the right rear wheel 204, and the right rear brake 341 can generate a corresponding braking force on the right rear wheel 204 by clamping the right rear brake disc 342.

[0067] The vehicle controller 101 is connected to the steering controller 103 and the brake controller 102 via signal lines. The steering controller 103 is connected to the left front steering system 410, the right front steering system 420, the left rear steering system 430 and the right rear steering system 440 via signal lines, thereby controlling the wheel steering angles of the left front wheel 201, the right front wheel 202, the left rear wheel 203 and the right rear wheel 204 respectively. The brake controller 102 is connected to the left front braking system 310, the right front braking system 320, the left rear braking system 330 and the right rear braking system 340 via signal lines, thereby controlling the wheel braking force of the left front wheel 201, the right front wheel 202, the left rear wheel 203 and the right rear wheel 204 respectively.

[0068] The cross-system redundant braking control method for all-condition braking safety is stored in the vehicle controller 101 and executed cyclically in real time. Specifically, for the condition where both the front and rear wheel braking systems fail, the redundant braking control process is as follows: Figure 2 As shown:

[0069] Step 1: The vehicle controller 101 collects vehicle information in real time and receives braking commands from the driver or the autonomous driving system. If it determines that the left front wheel braking system 310 (or right front wheel braking system 320) and the left rear wheel braking system 330 (or right rear wheel braking system 340) have both failed, it calculates the braking force requirements F for the left front wheel 201, the right front wheel 202, the left rear wheel 203, and the right rear wheel 204 under normal operating conditions according to the pre-calibrated braking force distribution rules. bFL F bFR F bRL F bRR ;

[0070] Step 2: The vehicle controller 101 determines whether the vehicle is in a steering condition by real-time detection of the output signals of the vehicle steering system 400, including the left front steering system 410, the right front steering system 420, the left rear steering system 430 and the right rear steering system 440. If the vehicle is in a steering condition, step 3 is executed; if the vehicle is not in a steering condition, step 4 is executed.

[0071] Step 3: The vehicle controller 101 controls the left front steering system 410, the right front steering system 420, the left rear steering system 430, and the right rear steering system 440 to simultaneously generate θ through the steering controller 103. bfl θ bfr θ srl * θ srr * The wheel steering angle generates a total front axle braking force F. bfl +F bfr The vehicle controller 101 can output a steering angle θ to the left rear steering system 430 and the right rear steering system 440 based on driver commands or the autonomous driving system, or by judging the vehicle status information in real time and according to the steering angle adjustment strategy pre-stored in the vehicle controller 101. srl * θ srr * Make real-time adjustments, and then proceed to step nine;

[0072] Step 4: The vehicle controller 101 determines whether the braking requirements can be met by relying solely on the left front steering system 410 and the right front steering system 420 using a redundant braking mode with active sideslip angle. If the braking requirements can be met, then proceed to step 5; otherwise, proceed to step 6.

[0073] Step 5: The vehicle controller controls the left front steering system 410 and the right front steering system 420 to generate θ respectively through the steering controller. bfl θ bfr The wheel steering angle generates a total front axle braking force F. bfl +F bfr Then proceed to step nine;

[0074] Step Six: The vehicle controller, through the steering controller, controls the left front steering system 410, the right front steering system 420, the left rear steering system 430, and the right rear steering system 440 to generate θ respectively. bfl θ bfr θ brl θ brrThe wheel steering angle generates a total front axle braking force and a rear axle braking force of F, respectively. bfl +F bfl and F bfl +F brr Then proceed to step seven;

[0075] Step 7: The vehicle controller 101 monitors the yaw rate ω of the vehicle in real time. r The vehicle is determined to be in a stable state by the sideslip angle β. If the vehicle controller 101 determines that the vehicle is not in a stable state, step eight is executed. If the vehicle is determined to be in a stable state, step nine is executed.

[0076] Step 8: The vehicle controller 101 controls the left front steering system 410 and the right front steering system 420 to maintain θ respectively through the steering controller 103. bfl θ bfr The wheel steering angle, where θ bfl =-θ bfr Maintain the total front axle braking force at F bfl +F bfr The vehicle controller 101 controls the left rear steering system 430 and the right rear steering system 440 through the steering controller 103, so that the wheel steering angle of the left rear wheel 203 and the right rear wheel 204 changes from θ. brl θ brr Recycled to θ brl * θ brr * Then proceed to step nine;

[0077] Step 9: The current loop ends. Return to Step 1 to start the next loop control.

[0078] In step three, the vehicle controller 101 can receive steering commands from the driver or the autonomous driving system in real time, with the steering wheel input angle δ. s With the desired rear wheel steering angle θ sr0 The following relationship exists:

[0079] Low-speed range (v≤v1):

[0080]

[0081] Transition interval (v1) <v<v2):

[0082]

[0083] High-speed range (v≥v2):

[0084]

[0085] Where, δ f For the steering angle of the car's front wheels, to meet (i is the steering system transmission ratio), v is the vehicle speed, v1 is the critical speed of the low-speed transition zone, v2 is the critical speed of the transition zone to high-speed. max k1 and k2 represent the maximum speed of the car, and k1 and k2 are the basic ratio coefficients for low speed and high speed. This is the correction factor for the steering angular velocity. k is the lateral acceleration correction factor. z This is the load distribution correction factor;

[0086] The following strategy is used to output the steering angle θ to the left rear steering system 420 and the right rear steering system 440. srl * θ srr * Make real-time adjustments;

[0087] The vehicle controller 101 can collect the vehicle's center of gravity position (x, y), center of gravity sideslip angle β, longitudinal vehicle speed v, and yaw rate w; and obtain the reference lateral and longitudinal coordinates (x, y) required for the vehicle to achieve trajectory tracking. r ,,y r Reference centroid sideslip angle β r Reference yaw rate ω r The method is built into the vehicle controller 101;

[0088] A PID control strategy is used to calculate the rear wheel output steering angle to track the target driving trajectory.

[0089]

[0090] Where e represents the trajectory tracking deviation, including: lateral position deviation e y =y r -y, the deviation of the centroid side slip angle is e β =β r -β and the deviation of yaw rate are e ω =ω r -ω;δ θ δ is the deviation between the actual rear wheel steering angle and the desired rear wheel steering angle. θ =θ sr * -θ sr0 ;k p k i k d These are the proportional, integral, and derivative control coefficients, which are adjusted and calibrated by the vehicle under normal driving conditions on a good road surface and then stored in the vehicle controller 101.

[0091] To prevent overload of the vehicle steering system 400 and vehicle instability, the output is saturated and limited:

[0092] Maximum rear wheel steering angle: |θ sr * |≤θ sr ** Maximum steering angular velocity: Steady-state control objective: |e y |≤e y * or |e β |≤e β * or |e ω |≤e ω * 、|δ θ |≤δ θ * ;

[0093] During the implementation of the control strategy, a cyclic correction is performed every time interval t, and the actual trajectory deviation is fed back to the vehicle controller 101 in real time to dynamically update the parameters and output steering angle θ. sr * .

[0094] In steps three, five, six, and eight, the θ bfl θ bfr θ brl θ brr The size can be obtained by looking up a table, as follows:

[0095] The following relationship exists during redundant braking:

[0096] F y-0 (|θ bf |)·sin|θ bf |=F bfw0

[0097] F y-0 (|θ br |)·sin|θ br |=F brw0

[0098] |θ bfl |=|θ bfr |=|θ bf |

[0099] |θ brl |=|θ brr |=|θ br |

[0100] In the formula, F y-0 (|θ bij |) represents the left front wheel 201, the right front wheel 202, the left rear wheel 203, or the right rear wheel 204 at the current sideslip angle |θ. bij The reference lateral force generated under | can be experimentally determined at the reference load. Calibration was performed at the specified road surface adhesion coefficient μ0, F bfw0 With F brw0 To the current sideslip angle |θ bij The redundant braking force generated by the front and rear wheels can be uniformly expressed as F. bw0 m is the mass of the car, g is the acceleration due to gravity, and L is the acceleration due to gravity. * L is the distance from the car's center of gravity to the rear or front axle, where L is the wheelbase.

[0101] F can be obtained from the above formula. bw0 With |θ bij The relationship table is F. bw0 =Curve{|θ bij The calibration results are stored in the vehicle controller 101.

[0102] According to the braking force requirement F of the left front wheel 201 and the right front wheel 202 bFL F bFR The θ can be obtained in real time by looking up the table based on the following formula. bfl With the θ bfr Size,

[0103]

[0104] |θ bfl |=|θ bfr |=|θ bf |

[0105] According to the braking force requirement F of the left rear wheel 203 and the right rear wheel 204 bRL F bRR The θ can be obtained in real time by looking up the table based on the following formula. brl With the θ brr Size,

[0106]

[0107] |θ brl |=|θ brr |=|θ br |

[0108] In the formula, μ is the actual ground adhesion coefficient, and a x Let h be the longitudinal acceleration of the vehicle, and h be the height of the vehicle's center of gravity.

[0109] For the scenario where only the front wheel braking system fails, the specific process of redundant braking control is as follows: Figure 3 As shown:

[0110] Step 1: The vehicle controller 101 collects vehicle information in real time and receives braking commands from the driver or the autonomous driving system. It determines whether only the left front wheel braking system 310 or the right front wheel braking system 320 is faulty. Based on pre-calibrated braking force distribution rules, it calculates the braking force requirements F for the left front wheel 201, the right front wheel 202, the left rear wheel 203, and the right rear wheel 204 under normal operating conditions. bFL F bFR F bRL F bRR ;

[0111] Step 2: The vehicle controller 101 determines whether the vehicle is in a steering condition by real-time detection of the output signals of the vehicle steering system 400, including the left front steering system 410, the right front steering system 420, the left rear steering system 430 and the right rear steering system 440. If the vehicle is in a steering condition, step 3 is executed; if the vehicle is not in a steering condition, step 4 is executed.

[0112] Step 3: The vehicle controller 101 controls the left front steering system 410, the right front steering system 420, the left rear steering system 430, and the right rear steering system 440 to simultaneously generate θ through the steering controller 103. bfl θ bfr θ srl * θ srr * The wheel steering angle generates a total front axle braking force F. bfl +F bfr The vehicle controller 101 can output a steering angle θ to the left rear steering system 430 and the right rear steering system 440 based on driver commands or the autonomous driving system, or by judging the vehicle status information in real time and according to the steering angle adjustment strategy pre-stored in the vehicle controller 101. srl * θ srr * Real-time adjustments are made, and the vehicle controller 101, through the brake controller 102, controls the left rear braking system 330 and the right rear braking system 340 to supplement the braking force, generating a total rear axle braking force F. bfl +F bfr To meet braking requirements, then proceed to step seven;

[0113] Step 4: The vehicle controller 101 determines whether braking using the redundant braking mode with active sideslip angle by relying solely on the left front steering system 410 and the right front steering system 420 can meet the braking requirements. If the braking requirements can be met, proceed to step 5; if the braking requirements cannot be met, proceed to step 6.

[0114] Step 5: The vehicle controller 101 controls the left front steering system 410, the right front steering system 420, the left rear steering system 430, and the right rear steering system 440 to generate θ respectively through the steering controller 103. bfl θ bfr The wheel steering angle generates a total front axle braking force F. bfl +F bfr Then proceed to step seven;

[0115] Step 6: The vehicle controller 101 controls the left front steering system 410 and the right front steering system 420 to generate θ respectively through the steering controller 103. bfl θ bfr The wheel steering angle generates a total front axle braking force F. bfl +F bfr The vehicle controller 101 controls the left rear braking system 330 and the right rear braking system 340 through the steering controller 102 to supplement the braking force, generating a total rear axle braking force of F. bfl +F bfr To meet braking requirements, then proceed to step seven;

[0116] Step 7: The current loop ends. Return to Step 1 to start the next loop control.

[0117] In step three, the vehicle controller 101 can receive steering commands from the driver or the autonomous driving system in real time, with the steering wheel input angle δ. s With the desired rear wheel steering angle θ sr0 The following relationship exists:

[0118] Low-speed range (v≤v1):

[0119]

[0120] Transition interval (v1) <v<v2):

[0121]

[0122] High-speed range (v≥v2):

[0123]

[0124] Where, δ fFor the steering angle of the car's front wheels, to meet (i is the steering system transmission ratio), v is the vehicle speed, v1 is the critical speed of the low-speed transition zone, v2 is the critical speed of the transition zone to high-speed. max k1 and k2 represent the maximum speed of the car, and k1 and k2 are the basic ratio coefficients for low speed and high speed. This is the correction factor for the steering angular velocity. k is the lateral acceleration correction factor. z This is the load distribution correction factor;

[0125] The following strategy is used to output the steering angle θ to the left rear steering system 420 and the right rear steering system 440. srl * θ srr * Make real-time adjustments;

[0126] The vehicle controller 101 can collect the vehicle's center of gravity position (x, y), center of gravity sideslip angle β, longitudinal vehicle speed v, and yaw rate ω; and obtain the reference lateral and longitudinal coordinates (x, y) required for the vehicle to achieve trajectory tracking. r ,,y r Reference centroid sideslip angle β r Reference yaw rate ω r The method is built into the vehicle controller 101;

[0127] A PID control strategy is used to calculate the rear wheel output steering angle to track the target driving trajectory.

[0128]

[0129] Where e represents the trajectory tracking deviation, including: lateral position deviation e y =y r -y, the deviation of the centroid side slip angle is e β =β r -β and the deviation of yaw rate are e ω =ω r -ω;δ θ δ is the deviation between the actual rear wheel steering angle and the desired rear wheel steering angle. θ =θ sr * -θ sr0 ;、k i k d These are the proportional, integral, and derivative control coefficients, which are adjusted and calibrated by the vehicle under normal driving conditions on a good road surface and then stored in the vehicle controller 101.

[0130] To prevent overload of the vehicle steering system 400 and vehicle instability, the output is saturated and limited:

[0131] Maximum rear wheel steering angle: |θ sr * |≤θ sr ** Maximum steering angular velocity: Steady-state control objective: |e y |≤e y * or |e β |≤e β * or |e ω |≤e ω * 、|δ θ |≤δ θ * ;

[0132] During the implementation of the control strategy, a cyclic correction is performed every time interval t, and the actual trajectory deviation is fed back to the vehicle controller 101 in real time to dynamically update the parameters and output steering angle θ. sr * .

[0133] In steps three, five, and six, the θ bfl θ bfr θ brl θ brr The size can be obtained by looking up a table, as follows:

[0134] The following relationship exists during redundant braking:

[0135] F y-0 (|θ bf |)·sin|θ bf |=F bfw0

[0136] F y-0 (|θ br |)·sin|θ br |=F br w0

[0137] |θ bfl |=|θ bfr |=|θ bf |

[0138] |θ brl |=|θ brr |=|θ br |

[0139] In the formula, F y-0 (|θ bij|) represents the left front wheel 201, the right front wheel 202, the left rear wheel 203, or the right rear wheel 204 at the current sideslip angle |θ. bij The reference lateral force generated under | can be experimentally determined at the reference load. Calibration was performed at the specified road surface adhesion coefficient μ0, F bfw0 With F brw0 To the current sideslip angle |θ bij The redundant braking force generated by the front and rear wheels can be uniformly expressed as F. bw0 m is the mass of the car, g is the acceleration due to gravity, and L is the acceleration due to gravity. * L is the distance from the car's center of gravity to the rear or front axle, where L is the wheelbase.

[0140] F can be obtained from the above formula. bw0 With |θ bij The relationship table is F. bw0 =Curve{|θ bij The calibration results are stored in the vehicle controller 101.

[0141] According to the braking force requirement F of the left front wheel 201 and the right front wheel 202 bFL F bFR The θ can be obtained in real time by looking up the table based on the following formula. bfl With the θ bfr Size,

[0142]

[0143] |θ bfl |=|θ bfr |=|θ bf |

[0144] According to the braking force requirement F of the left rear wheel 203 and the right rear wheel 204 bRL F bRR The θ can be obtained in real time by looking up the table based on the following formula. brl With the θ brr Size,

[0145]

[0146] |θ brl |=|θ brr |=|θ br |

[0147] In the formula, μ is the actual ground adhesion coefficient, and a x Let h be the longitudinal acceleration of the vehicle, and h be the height of the vehicle's center of gravity.

[0148] The θ bFL The θbFR The θ bRL With the θ bRR There are several methods for controlling the steering angle, as follows (taking a positive steering angle value for a left turn and a negative steering angle value for a right turn as an example):

[0149] Method 1, such as Figure 4 As shown, the θ bFL If positive, then θ bFR If negative, then θ bRL If positive, then θ bRR If the value is negative, the left front wheel 201 and the right front wheel 202 are in an outward-pointing position, and the left rear wheel 203 and the right rear wheel 204 are in an outward-pointing position.

[0150] Method 2, such as Figure 5 As shown, the θ bFL If negative, then θ bFR If positive, then θ bRL If negative, then θ bRR When the left front wheel 201 and right front wheel 202 are in an inward-facing position, the left rear wheel 203 and right rear wheel 204 are in an inward-facing position.

[0151] Method 3, such as Figure 6 As shown, the θ bFL If positive, then θ bFR If negative, then θ bRL If negative, then θ bRR When the left front wheel 201 and right front wheel 202 are in an outward-facing position, the left rear wheel 203 and right rear wheel 204 are in an inward-facing position.

[0152] Method four, such as Figure 7 As shown, the θ bFL If negative, then θ bFR If positive, then θ bRL If positive, then θ bRR If the value is negative, the left front wheel 201 and the right front wheel 202 are in an inward-pointing position, while the left rear wheel 203 and the right rear wheel 204 are in an outward-pointing position.

[0153] Method 5, such as Figure 8 As shown, the θ bFL If positive, then θ bFR When the value is negative, the left front wheel 201 and the right front wheel 202 are in an outward-pointing position, and the left rear wheel 203 and the right rear wheel 204 are in a turning position.

[0154] Method Six, such as Figure 9 As shown, the θ bFL If negative, then θ bFR When the left front wheel 201 and right front wheel 202 are in an inward-pointing position, the left rear wheel 203 and right rear wheel 204 are in a turning position.

[0155] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A cross-system redundant braking control method for all-condition braking safety, characterized in that: The vehicle controller determines in real time whether the front wheel braking system and the rear wheel braking system have failed. If both the front wheel braking system and the rear wheel braking system fail, or only the front wheel braking system fails, the cross-system redundant braking control method for all-condition braking safety is executed. When only the front wheel braking system fails, the vehicle controller controls the left front steering system and the right front steering system to simultaneously generate θ. bfl θ bfr The wheel steering angle, where θ bfl =-θ bfr To maximize the braking requirements of the vehicle; wherein, when the front wheel braking system fails during cornering, the vehicle controller only controls the left front steering system and the right front steering system for cross-system redundant braking control, generating θ respectively. bfl θ bfr The wheel steering angle, where θ bfl =-θ bfr The vehicle controller controls the left rear steering system and the right rear steering system to control the vehicle's turning trajectory in order to follow the driver's desired turning trajectory. At this time, the left rear braking system and the right rear braking system can perform a certain degree of mechanical braking while ensuring the vehicle's turning control, so as to meet the vehicle's braking needs to the maximum extent. When both the front and rear braking systems fail, under low braking force demand in a straight line, the vehicle controller only controls the left front steering system and the right front steering system for cross-system redundant braking control, generating θ respectively. bfl θ bfr The wheel steering angle, where θ bfl =-θ bfr To meet braking requirements; under high braking force demand in straight-line conditions, the vehicle controller controls the left front steering system, the right front steering system, the left rear steering system, and the right rear steering system to perform cross-system redundant braking control, generating θ respectively. bfl θ bfr θ brl θ brr The wheel steering angle, where θ bfl =-θ bfr θ brl =-θ brr When the left rear steering system and the right rear steering system perform cross-system redundant straight-line braking control, the vehicle controller needs to monitor the vehicle's stability in real time. If the vehicle is at risk of instability due to disturbance or the trajectory tracking deviation is too large, the cross-system redundant braking control based on the left rear steering system and the right rear steering system needs to be canceled. When the front wheel braking system and the rear wheel braking system fail during cornering, the vehicle controller only controls the left front steering system and the right front steering system to perform cross-system redundant braking control, generating θ respectively. bfl θ bfr The wheel steering angle, where θ bfl =-θ bfr The vehicle controller controls the left rear steering system and the right rear steering system to control the vehicle's turning trajectory in order to follow the driver's desired turning path.

2. The cross-system redundant braking control method for all-condition braking safety as described in claim 1, characterized in that, This method is used in the braking control process of the vehicle and is applicable to a four-wheel distributed independent steering vehicle configuration, which includes: a left front wheel, a right front wheel, a left rear wheel, a right rear wheel, a vehicle steering system, a vehicle braking system, a steering controller, a braking controller, and the vehicle controller. The vehicle steering system includes the left front steering system, the right front steering system, the left rear steering system, and the right rear steering system; the vehicle braking system includes the left front braking system, the right front braking system, the left rear braking system, and the right rear braking system; the left front braking system and the right front braking system constitute the front wheel braking system; and the left rear braking system and the right rear braking system constitute the rear wheel braking system. The vehicle controller is connected to the steering controller and the brake controller via a communication bus. The steering controller is connected to the left front steering system, the right front steering system, the left rear steering system, and the right rear steering system via signal lines, thereby controlling the wheel steering angles of the left front wheel, the right front wheel, the left rear wheel, and the right rear wheel respectively. The brake controller is connected to the left front braking system, the right front braking system, the left rear braking system, and the right rear braking system via signal lines, thereby controlling the wheel braking force of the left front wheel, the right front wheel, the left rear wheel, and the right rear wheel respectively.

3. The cross-system redundant braking control method for all-condition braking safety as described in claim 2, characterized in that, The vehicle controller can determine whether the left front braking system, the right front braking system, the left rear braking system, and the right rear braking system have malfunctioned by using the vehicle's braking deceleration, yaw rate status information, and the rotation angle and current signals of each braking actuator motor. When the left front braking system or the right front braking system malfunctions, the front wheel braking system is considered to have malfunctioned; when the left rear braking system or the right rear braking system malfunctions, the rear wheel braking system is considered to have malfunctioned. When the front wheel braking system is functioning correctly but the rear wheel braking system is malfunctioning, the vehicle controller controls the left front braking system and the right front braking system to generate braking force through the brake controller to maximize the braking demand of the vehicle. The vehicle controller also controls the wheel steering angles of the left front steering system, the right front steering system, the left rear steering system, and the right rear steering system normally according to the trajectory tracking requirements of the driver or the autonomous driving system through the steering controller. When neither the front wheel braking system nor the rear wheel braking system malfunctions, the vehicle controller controls the left front braking system, the right front braking system, the left rear braking system, and the right rear braking system to generate braking force according to the braking force distribution rules to meet the braking requirements of the vehicle. The vehicle controller also controls the wheel steering angles of the left front steering system, the right front steering system, the left rear steering system, and the right rear steering system normally according to the trajectory tracking requirements of the driver or the autonomous driving system through the steering controller.

4. The cross-system redundant braking control method for all-condition braking safety as described in claim 2, characterized in that, The vehicle controller can determine whether the left front steering system, the right front steering system, the left rear steering system, and the right rear steering system are in a steering working state by using yaw rate status information and the rotation angle and current signals of each brake actuator motor, and thus determine whether the vehicle is in a steering state.

5. The cross-system redundant braking control method for all-condition braking safety as described in claim 1, characterized in that, When the left rear steering system and the right rear steering system perform cross-system redundant straight-line braking control, it is necessary to monitor the vehicle's stability in real time. At this time, the vehicle controller can monitor the vehicle's yaw rate and sideslip angle relative to the center of gravity in real time. When the yaw rate and sideslip angle relative to the center of gravity exceed the target limit value ω... r * β * Or when the yaw rate and the center-of-mass sideslip angle approach the target limit value ω r * β * Furthermore, after maintaining this state for a certain period of time, it was determined that the vehicle was not in a stable state and was at risk of instability.

6. The cross-system redundant braking control method for all-condition braking safety as described in claim 2, characterized in that, When the vehicle experiences a front wheel braking system failure while turning, or when both the front and rear wheel braking systems fail while turning, the vehicle controller can receive steering commands from the driver or the autonomous driving system in real time, with the steering wheel input angle δ. s With the desired rear wheel steering angle θ sr0 The following relationship exists: Low-speed range (v≤v1): Transition interval (v1) <v<v2): High-speed range (v≥v2): Where, δ f For the steering angle of the car's front wheels, to meet (i is the steering system transmission ratio), v is the vehicle speed, v1 is the critical speed of the low-speed transition zone, v2 is the critical speed of the transition zone to high-speed. max k1 and k2 represent the maximum speed of the car, and k1 and k2 are the basic ratio coefficients for low speed and high speed. This is the correction factor for the steering angular velocity. k is the lateral acceleration correction factor. z This is the load distribution correction factor; The following strategy is used to output the steering angle θ for the left rear steering system and the right rear steering system. srl * θ srr * Make real-time adjustments; The vehicle controller can collect the vehicle's center of gravity position (x, y), center of gravity sideslip angle β, longitudinal vehicle speed v, and yaw rate ω; and obtain the reference lateral and longitudinal coordinates (x, y) required for the vehicle to achieve trajectory tracking. r ,,y r Reference centroid sideslip angle β r Reference yaw rate ω r The method is built into the vehicle controller; A PID control strategy is used to calculate the rear wheel output steering angle to track the target driving trajectory. Where e represents the trajectory tracking deviation, including: lateral position deviation e y =y r -y, the deviation of the centroid side slip angle is e β =β r -β and the deviation of yaw rate are e ω =ω r -ω;δ θ δ is the deviation between the actual rear wheel steering angle and the desired rear wheel steering angle. θ =θ sr * -θ sr0 ;k p k i k d These are the proportional, integral, and derivative control coefficients, which are adjusted and calibrated by the vehicle under normal driving conditions on a good road surface and then stored in the vehicle controller. To prevent overload of the vehicle steering system and vehicle instability, the output is saturated and limited: Maximum rear wheel steering angle: |θ sr * |≤θ sr ** Maximum steering angular velocity: Steady-state control objective: |e y |≤e y * or |e β |≤e β * or |e ω |≤e ω * 、|δ θ |≤δ θ * ; During the implementation of the control strategy, a cyclic correction is performed every time interval t, and the actual trajectory deviation is fed back to the vehicle controller in real time to dynamically update the parameters and output steering angle θ. sr * .

7. The cross-system redundant braking control method for all-condition braking safety as described in claim 2, characterized in that, The θ bfl θ bfr θ brl θ brr The size can be obtained by looking up a table, as follows: The following relationship exists during redundant braking: F y-0 (|θ bf |)·sin|θ bf |=F bfw0 F y-0 (|θ br |)·sin|θ br |=F brw0 |θ bfl |=|θ bfr |=|θ bf | |θ brl |=|θ brr |=|θ br | In the formula, F y-0 (|θ bij |) represents the left front wheel, the right front wheel, the left rear wheel, or the right rear wheel at the current sideslip angle |θ. bij The reference lateral force generated under | can be experimentally determined at the reference load. Calibration was performed at the specified road surface adhesion coefficient μ0, F bfw0 With F brw0 To the current sideslip angle |θ bij The redundant braking force generated by the front and rear wheels can be uniformly expressed as F. bw0 m is the mass of the car, g is the acceleration due to gravity, and L is the acceleration due to gravity. * L is the distance from the car's center of gravity to the rear or front axle, where L is the wheelbase. F can be obtained from the above formula. bw0 With |θ bij The relationship table is F. bw0 =Curve{|θ bij The calibration results are stored in the vehicle controller. According to the braking force requirement F of the left front wheel and the right front wheel bFL F bFR The θ can be obtained in real time by looking up the table based on the following formula. bfl With the θ bfr Size, |θ bfl |=|θ bfr |=|θ bf | According to the braking force requirement F of the left rear wheel and the right rear wheel bRL F bRR The θ can be obtained in real time by looking up the table based on the following formula. brl With the θ brr Size, |θ brl |=|θ brr |=|θ br | In the formula, μ is the actual ground adhesion coefficient, and a x Let h be the longitudinal acceleration of the vehicle, and h be the height of the vehicle's center of gravity.

8. The cross-system redundant braking control method for all-condition braking safety as described in claim 2, characterized in that, The vehicle controller, through the steering controller, controls the left front steering system, the right front steering system, the left rear steering system, and the right rear steering system to generate θ respectively. bfl θ bfr θ brl θ brr The wheel steering angle, where θ bfl =-θ bfr θ bfr =-θ brr This causes the left front wheel, the right front wheel, the left rear wheel, and the right rear wheel to simultaneously generate |θ. bfl ′|、|θ bfr ′|、|θ brl ′|、|θ brr The sideslip angle of |′; Where θ bfl ′、θ bfr ′、θ brl ′、θ brr The specific value of ′ can be calculated by the following formula: In the formula, v y B is the lateral velocity at the car's center of mass, ω is the car's yaw rate, and B is the lateral velocity at the car's center of mass. f B r These are the front axle track and rear axle track of the car, respectively, L f L r These represent the distances from the vehicle's center of gravity to the front or rear axle, respectively, and u represents the longitudinal velocity at the vehicle's center of gravity. Finally, by utilizing the components of the lateral forces of the left and right front wheels in the vehicle's forward direction, a total front axle braking force of F is generated. bFL +F bFR By utilizing the components of the lateral forces from the left and right rear wheels in the vehicle's forward direction, a total rear axle braking force of F is generated. bRL +F bRR .

9. The cross-system redundant braking control method for all-condition braking safety as described in claim 2, characterized in that, The vehicle controller receives braking commands from the driver or the autonomous driving system in real time, and calculates the braking force requirements F for the left front wheel, the right front wheel, the left rear wheel, and the right rear wheel under normal operating conditions according to the pre-calibrated braking force distribution rules. bFL F bFR F bRL F bRR The maximum wheel steering angle θ that the left front steering system and the right front steering system of the vehicle can produce. bFL θ bFR The total maximum redundant braking force that can be generated by the vehicle controller is F. bFL * +F bFR * ; If F is satisfied bFL * +F bFR * ≥F bFL +F bFR +F bRL +F bRR If the condition is met, it can be determined that it is a linear operating condition with low braking force requirement. F bFL * +F bFR * <F bFL +F bFR +F bRL +F bRR If so, it can be determined that it is a linear operating condition with high braking force demand.

10. The cross-system redundant braking control method for all-condition braking safety as described in claim 5, characterized in that, When the left rear steering system and the right rear steering system perform cross-system redundant straight-line braking control and the vehicle is not in a stable state, the vehicle controller controls the left rear steering system and the right rear steering system to adjust their rear wheel steering angle θ via the steering controller. brl θ brr Recycle to θ brl * θ brr * Adjust the θ brl * With θ brr * The target value for the wheel steering angle should be such that the sideslip angle |θ| between the left and right rear wheels is equal. brr *′ |、|θ brr *′ |As close as possible to the slip angle between the left and right rear wheels when the vehicle is traveling normally in a straight line on a good road surface|θ brl0 |、|θ brr0 This allows the vehicle to generate maximum lateral force reserve.

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