Front axle reinforced redundant braking method based on active slip angle adjustment and electric braking

Abstract

The invention discloses a front axle reinforced redundant braking method based on active slip angle adjustment and electric braking, and aims to solve the problem of insufficient electric redundant braking force under the working condition of large braking force demand of a front axle. Comprising the steps of receiving a braking instruction and calculating braking force of each wheel; judging whether left front wheel and right front wheel brakes fail or not; and if a certain wheel breaks down, redundant braking control over the wheel is carried out. The redundant braking control process comprises the steps that if the electric redundant braking force can be met, redundant braking is conducted on the faulty wheels in an electric braking mode, and friction braking is still conducted on the non-faulty wheels in an electromechanical braking mode; if not, the maximum electric redundant braking force is applied to the two front wheels for braking, and meanwhile an enhanced braking mode based on a wheel lateral force longitudinal component generated based on active slip angle adjustment is introduced for redundant braking; meanwhile, when the vehicle body deflects, the mechanical braking force of the two rear wheels is adjusted in real time, additional yawing force is generated to rectify the vehicle body, and the stability of the braking direction is enhanced.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of automobile chassis, and particularly relates to a front axle reinforced redundancy braking method based on active side slip angle adjustment and electric braking. BACKGROUND

[0002] In recent years, with the development of intelligent networked electric vehicles, the demand for chassis technology with higher control accuracy, response speed and control freedom is rapidly growing. Electronic mechanical brake systems and electronic hydraulic mechanical brake systems, as representatives of brake-by-wire systems, have attracted high attention from the industry and academia, and are gradually realizing mass production and popularization. Brake-by-wire systems use electronic components to replace the original mechanical connection mechanism, which, although realizes decoupling of control, causes lower reliability; if the actuator fails, the vehicle may face the situation of insufficient braking force and inability to safely brake in emergency braking conditions.

[0003] To solve the problem of insufficient reliability of brake-by-wire technology, some manufacturers and scholars apply redundancy braking force by setting up a backup brake actuator, which obviously increases the production cost of the vehicle. In addition, some manufacturers and scholars also apply redundancy braking control through the electric braking torque of the drive motor. Currently, electric vehicles usually have a drive system with large power and torque on the rear axle, and a drive system with small power and torque on the front axle. However, the demand for braking force is just the opposite: the front axle needs more braking force, and the rear axle needs less braking force. This means that the redundancy braking control method based on electric braking torque can meet the braking demand of the rear axle in most conditions, but it usually cannot meet the braking demand of the front axle in large braking force conditions, which may cause the problem of insufficient braking force of the front axle in emergency braking conditions.

[0004] To solve the above problems, the application provides a front axle reinforced redundancy braking method based on active side slip angle adjustment and electric braking, which uses the large steering angle control advantage of the front axle independent steering system to actively adjust the tire side slip angle, and then generates a redundancy braking force through the tire lateral force; and the cross-system reinforced redundancy braking method of the front axle is realized by combining the electric braking redundancy control. SUMMARY

[0005] The application aims to provide a front axle reinforced redundancy braking method based on active side slip angle adjustment and electric braking, which can generate a redundancy braking force in the forward direction of the vehicle through the control of the steering angle of the front axle independent steering system, and effectively realize the cross-system reinforced redundancy braking control of the front axle brake-by-wire system by combining the electric braking redundancy braking control.

[0006] To achieve the above purpose, the following technical solutions are adopted:

[0007] A front axle reinforced redundancy braking method based on active side slip angle regulation and electric braking, characterized in that:

[0008] The method is used in a vehicle braking control process and is applicable to a four-wheel distributed electric drive vehicle equipped with a front wheel distributed independent steering system, which comprises a left front wheel brake, a right front wheel brake, a left front drive system, a right front drive system, a left front steering system, a right front steering system, a brake controller, a drive controller, a steering controller, and a vehicle controller.

[0009] The vehicle controller is connected with the brake controller, the drive controller, and the steering controller through a communication bus; the brake controller is connected with the left front wheel brake and the right front wheel brake through a signal line, thereby controlling the wheel braking force of the left front wheel and the right front wheel; the drive controller is connected with the left front drive system and the right front drive system through a signal line, thereby controlling the drive force and electric braking force of the left front wheel and the right front wheel; the steering controller is connected with the left front steering system and the right front steering system through a signal line, thereby controlling the wheel steering angle of the left front wheel and the right front wheel, respectively.

[0010] The method is mainly applied to the front axle of a vehicle with insufficient electric redundancy braking force and large braking force demand; for the rear axle of a vehicle with sufficient electric redundancy braking force and small braking force demand, if the left rear wheel brake or the right rear wheel brake fails, the electric braking mode should be mainly used for redundancy braking control to ensure the braking stability and safety of the vehicle as much as possible.

[0011] The method is stored in the vehicle controller, and the specific process is as follows:

[0012] Step one, the vehicle controller receives the braking instruction in real time, and calculates the required braking force of the front axle of the vehicle under the current working condition as 2F bF , the required braking force of the left front wheel and the right front wheel as F bF and F bF , respectively, and the required braking deceleration of the whole vehicle as 2F bF / m (m is the mass of the vehicle); the braking force distribution rule is a front-rear axle braking force distribution curve according to the ideal front-rear axle braking force distribution I curve, or a front-rear axle braking force distribution curve prepared under the premise of meeting the braking regulations, so as to ensure the stable and safe braking of the vehicle as much as possible.

[0013] Step two, the vehicle controller determines whether the left front wheel brake or the right front wheel brake fails, if the left front wheel brake fails, step three is executed, if the right front wheel brake fails, step five is executed, if the left front wheel brake and the right front wheel brake both fail, step seven is executed, if the left front wheel brake and the right front wheel brake both do not fail, step twelve is executed; the vehicle controller can determine whether the left front wheel brake and the right front wheel brake fail through vehicle deceleration, yaw rate state information, left front wheel brake motor rotation angle and current signal and right front wheel brake motor rotation angle and current signal, and can also determine whether the vehicle body leans to the left or to the right.

[0014] Step three, if |F bF |≤|F ebm | (in the formula F ebm is the maximum electric braking force that the left front drive system and the right front drive system can reach under the current working condition), the vehicle controller controls the left front wheel brake and the right front wheel brake to generate braking forces 0, F bF respectively through the brake controller, and controls the left front drive system and the right front drive system to generate electric braking forces F bF , 0 respectively and simultaneously through the drive controller, so as to generate the vehicle front axle required braking force 2F bF , and then step nine is executed; if |F bF |≤|F ebm | is not met, step four is executed.

[0015] Step four, the vehicle controller controls the left front wheel brake and the right front wheel brake to generate braking forces 0, F ebm respectively through the brake controller, and controls the left front drive system and the right front drive system to generate electric braking forces F ebm , 0 respectively and simultaneously through the drive controller, uses |θ bF | vs F ebm two-dimensional lookup table to obtain the combination of the current F ebm and |θ bF |, controls the left front steering system and the right front steering system to generate wheel steering angles θ bFL , θ bFR respectively and simultaneously through the steering controller, wherein θ bFL =-θ bFR , |θ bFL | = |θ bFR | = |θ bF |, so as to meet the vehicle front axle component 2F bFThe braking deceleration requirement is / m, then step nine is executed;

[0016] Step 5: If |F bF |≤|F ebm Then, the vehicle controller controls the left front wheel brake and the right front wheel brake to generate braking force F through the brake controller. bF 0, and through the drive controller, the left front drive system and the right front drive system simultaneously generate 0 and F respectively. bF The electric braking force generates the braking force 2F required for the front axle of the vehicle. bF Then proceed to step nine; if |F is not satisfied bF |≤|F ebm If so, proceed to step six;

[0017] Step 6: The vehicle controller, through the brake controller, controls the left front wheel brake and the right front wheel brake to generate braking force F respectively. ebm 0, and through the drive controller, the left front drive system and the right front drive system simultaneously generate 0 and F respectively. ebm The electric braking force, utilizing |θ bF |vs F ebm Two-dimensional lookup table to obtain the current F ebm and |θ bF The combination of | allows the steering controller to simultaneously generate θ for the left front steering system and the right front steering system. bFL θ bFR The wheel steering angle, where θ bFL =-θ bFR ,|θ bFL |=|θ bFR |=|θ bF |, used to satisfy the vehicle's front axle component being 2F bF The braking deceleration requirement is / m, then step nine is executed;

[0018] Step 7: If |F bF |≤|F ebm Then, the vehicle controller controls the left front drive system and the right front drive system to simultaneously generate F through the drive controller. bF F bF The electric braking force generates the braking force 2F required for the front axle of the vehicle. bF Then proceed to step nine; if |F is not satisfied bF |≤|F ebm If |, then proceed to step eight;

[0019] Step 8: The vehicle controller, through the drive controller, controls the left front drive system and the right front drive system to simultaneously generate F. ebm F ebm The electric braking force, utilizing |θ bF |vs F ebm Two-dimensional lookup table to obtain the current F ebm and |θ bF The combination of | allows the steering controller to simultaneously generate θ for the left front steering system and the right front steering system. bFL θ bFR The wheel steering angle, where θ bFL =-θ bFR ,|θ bFL |=|θ bFR |=|θ bF |, used to satisfy the vehicle's front axle component being 2F bF The braking deceleration requirement is / m, then step nine is executed;

[0020] Step 9: The vehicle controller determines the yaw direction of the vehicle body based on the vehicle yaw rate status information. If the vehicle body yaws to the left, proceed to step 10; if the vehicle body yaws to the right, proceed to step 11; if the vehicle body does not yaw, proceed to step 13.

[0021] Step 10: The vehicle controller controls the right rear wheel brake to generate braking force ΔF through the brake controller. M This generates an additional yaw moment to correct the vehicle body yaw, and then determines whether the vehicle body has stopped yawing. If it is still yawing, proceed to step nine.

[0022] Step 11: The vehicle controller controls the left rear wheel brake to generate braking force ΔF through the brake controller. M This generates an additional yaw moment to correct the vehicle body yaw, and then determines whether the vehicle body has stopped yawing. If it is still yawing, proceed to step nine.

[0023] Step 12: The vehicle controller, through the brake controller, controls the left front wheel brake and the right front wheel brake to generate braking force F respectively. bF F bF This generates the braking force 2F required by the front axle of the vehicle. bF The vehicle controller controls the left front steering system and the right front steering system to perform normal steering control through the steering controller;

[0024] Step 13: The current loop ends. Return to Step 1 to start the next loop control.

[0025] In steps four, six, and eight above, the |θ bF |vs Febm Two-dimensional lookup tables can be obtained through test vehicle calibration.

[0026] First, taking the forward direction of the test vehicle as a reference, the left turn of the wheel and the turning angle value are defined as positive, and θ is... bFL >0, the θ bFR >0; the wheel turns right, the turning angle value is negative, the θ bFR <0, the θ bFL <0;

[0027] When the θ bFR >0, the θ bFL When <0, the current steering mode is defined as yaw steering;

[0028] When the θ bFR <0, the θ bFL When the value is greater than 0, the current steering mode is defined as outward steering.

[0029] |θ bF | Defined as the absolute value of the front wheel steering angle, satisfying the following relationship:

[0030] |θ bF |=|θ bFL |=|θ bFR |

[0031] The following tests were conducted on a flat, straight, and uniform road surface:

[0032] Experiment 1: The test vehicle was first accelerated to a speed of 100 km / h, then the driving force was reduced to 0. Starting 0.5 seconds after the driving force was reduced to 0, the θ... bFL With the θ bFR Both remain at 0. The left front drive system and the right front drive system generate an electric braking force F that increases linearly from 0N with a slope of 1000N / s. ebm When the left or right front wheel locks up, the application of electric braking force is stopped until the test vehicle comes to a stop. The braking deceleration F corresponding to 0.1g, 0.2g, 0.3g, 0.4g, and 0.5g during the above process is recorded respectively. ebm , as the |θ bF |vs F ebm The starting point of the horizontal axis of a two-dimensional lookup table;

[0033] Experiment 2: The test vehicle was first accelerated to a speed of 100 km / h, and the driving force was reduced to 0. Starting from 0.5 seconds after the driving force was reduced to 0, the left front steering system θ was controlled by the steering controller. bFL Starting from 0°, the angle changes linearly at a slope of 10° / s until it reaches -90°. Simultaneously, the θ of the right front steering system is controlled by the steering controller.bFR Starting from 0°, the steering angle changes linearly at a slope of 10° / s until it reaches 90°. The current steering method is the inward octagon steering. The electric braking force F ebm Keep the value at 0 until the test vehicle stops. Record the corresponding |θ| for braking decelerations of 0.1g, 0.2g, 0.3g, 0.4g, and 0.5g during the above process. bF |, as the |θ bF |vs F ebm The starting point of the vertical axis of a two-dimensional lookup table;

[0034] Test 3: The test vehicle was first accelerated to a speed of 100 km / h, and the driving force was reduced to 0. Starting from 0.5 seconds after the driving force was reduced to 0, the left front steering system θ was controlled by the steering controller. bFL Starting from 0°, the angle changes linearly at a slope of 10° / s until it reaches -90°. Simultaneously, the θ of the right front steering system is controlled by the steering controller. bFR Starting from 0°, the steering angle changes linearly at a slope of 10° / s until it reaches 90°. The current steering method is the inward octagon steering. The electric braking force F is then... ebm Five tests were conducted with braking decelerations of 500N, 1000N, 1500N, 2000N, and 2500N, respectively. The corresponding values ​​of |θ| were recorded for each deceleration: 0.1g, 0.2g, 0.3g, 0.4g, and 0.5g. bF |and F ebm , as the |θ nF |vs F ebm Vertical scatter plot of a two-dimensional lookup table;

[0035] Experiment 4: The test vehicle first accelerates to a speed of 100 km / h, then reduces the driving force to 0. Starting 0.5 seconds after the driving force reduces to 0, the |θ... nF Maintain the angles at 0°, 10°, 20°, 30°, 40°, 50°, and 60°, perform 5 tests, and ensure that the stated θ... bFR >0, the θ bFL <0, the current steering mode is the inward octagon steering, the left front drive system and the right front drive system generate an electric braking force F that increases linearly from 0N with a slope of 1000N / s. ebm When the left or right front wheel locks up, the application of electric braking force is stopped until the test vehicle comes to a stop. The braking deceleration F corresponding to 0.1g, 0.2g, 0.3g, 0.4g, and 0.5g during the above process is recorded respectively. ebm and |θ bF |, as the |θ bF |vs F ebm Horizontal scatter points of a two-dimensional lookup table chart;

[0036] The coordinate points obtained from the above experiment were divided into 5 groups according to the braking decelerations of 0.1g, 0.2g, 0.3g, 0.4g, and 0.5g. Five curves were fitted to each group to form the |θ|. bF |vs F ebm Two-dimensional lookup table, through the aforementioned |θ bF |vs F ebm By interpolating and looking up the table using a two-dimensional lookup table, we can obtain the value of any F under the current road surface adhesion conditions and when the steering mode is the inward yaw. ebm and the θ bFL With the θ bFR The correspondence.

[0037] Similar to Experiment 1, Experiment 2, Experiment 3, and Experiment 4, the |θ| can be obtained when the steering mode is the outward octagonal steering. bF |vs F ebm Two-dimensional lookup table diagram.

[0038] Furthermore, under the same other test conditions, the |θ| was tested under different road surface adhesion conditions. bF |vsF ebm The two-dimensional lookup table is drawn to obtain multiple sets of |θ under various road surface adhesion conditions. bF |vs F ebm Two-dimensional lookup table diagram.

[0039] The |θ bF |vs F ebm The two-dimensional lookup table is stored in the vehicle controller.

[0040] In steps four, six, and eight above, the specific choice between the inward-facing and outward-facing steering is determined through a road braking test:

[0041] Due to differences in the front axle suspension structure of different vehicles, the lateral stability of the vehicle body differs when performing outward or inward steering. Therefore, for a specific target vehicle, the split-road braking test is needed to determine whether to use inward or outward steering when performing front axle reinforced redundant braking. The split-road braking test method is as follows:

[0042] The test section is 100m long and 5m wide, with the left half being a high-adhesion surface and the right half a low-adhesion surface. The target vehicle travels in a straight line at a speed of 20km / h, with its centerline aligned with the centerline of the test section. Three meters before entering the test section, the driving force is reduced to zero, and the left and right front wheels are made to perform an outward yaw steering maneuver with a steering angle of 10°. The yaw rate of the vehicle during this process is recorded. Under the same test conditions, a second test is conducted, with the left and right front wheels performing an inward yaw steering maneuver with a steering angle of 10°, and the yaw rate of the vehicle during this process is recorded. By comparing the magnitudes of the yaw rates in the two experiments, the steering method with the smaller yaw rate is selected as the steering method used by the target vehicle when performing front axle reinforced redundant braking.

[0043] In steps ten and eleven above, the corrective force ΔF M Determined using the following method:

[0044] The corrective force ΔF M The PID control algorithm, stored in the vehicle controller, is used for calculation. The input to the PID control algorithm is the difference between the target yaw rate and the actual yaw rate, and the output is the corrective force ΔF. M The target yaw rate is 0, and the PID algorithm is as follows:

[0045]

[0046] Among them, K p ,K d ,K i These are the proportional, derivative, and integral gains, respectively; their specific values ​​are calibrated based on the actual situation. ω r The actual yaw rate is given.

[0047] The aforementioned front axle reinforced redundant braking method based on active sideslip angle adjustment and electric braking is also applicable to electric vehicles with independent dual-motor drive on the front and rear axles or electric vehicles with a single-motor drive on the front axle. In this case, since the electric redundant braking force cannot achieve independent control of the left and right front wheels, the following control should be performed in steps four to eight above when the failure of the left or right front wheel brake is detected:

[0048] If |F bF |≤|F ebm |(F in the formula) ebm (where the maximum electric braking torque that the front axle drive system can apply under the current operating conditions is defined as 2F), then the vehicle controller controls the front axle drive system to generate 2F through the drive controller. bF Electric braking force;

[0049] If |F is not satisfied bF |≤|F ebm Then the vehicle controller controls the front axle drive system to generate 2F through the drive controller. bF The electric braking force, at the braking deceleration required by the vehicle 2F bF Under the / m requirement, through |θ bF |vs F ebm In a two-dimensional lookup table, the steering controller controls the left front steering system and the right front steering system to simultaneously generate values ​​corresponding to the current F. ebm Corresponding θ bFL θ bFR The wheel steering angle, where θ bFL =-θ bFR This generates the braking force 2F required for the front axle of the vehicle. bF .

[0050] The beneficial effects of this invention are:

[0051] 1. The front axle reinforced redundant braking method based on active sideslip angle adjustment and electric braking described in this invention can achieve braking redundancy control based on the front wheel independent steering system and electric drive system, without the need to set up an additional brake-by-wire actuator for backup, thus reducing the vehicle production and manufacturing cost.

[0052] 2. The front axle reinforced redundant braking method based on active sideslip angle adjustment and electric braking described in this invention can further superimpose reinforced redundant braking force based on active sideslip angle adjustment of the steer-by-wire system on the basis of redundant electric braking force, so as to solve the problem of insufficient redundant electric braking force of the front axle under the condition of failure of the steer-by-wire mechanical braking system and meet the large braking force requirements of the vehicle under emergency braking conditions.

[0053] 3. The front axle reinforced redundant braking method based on active sideslip angle adjustment and electric braking described in this invention can further introduce a correction force to correct the vehicle's yaw rate online, while meeting the large braking force requirements under emergency braking conditions, so as to meet the vehicle's braking directional stability requirements. Attached Figure Description

[0054] Figure 1 This is a simplified diagram of a vehicle configuration based on a front axle reinforced redundant braking method using active sideslip angle adjustment and electric braking, as described in this invention.

[0055] Figure 2 This is a control flowchart of a front axle reinforced redundant braking method based on active sideslip angle adjustment and electric braking, as described in this invention.

[0056] Figure 3This is a schematic diagram of the front wheel inward octagon steering method based on active sideslip angle adjustment and electric braking, as described in this invention.

[0057] Figure 4 This is a schematic diagram of the front wheel octagon steering method based on active sideslip angle adjustment and electric braking, as described in this invention.

[0058] Figure 5 The |θ| of the front axle reinforced redundant braking method based on active sideslip angle adjustment and electric braking described in this invention. bF |vs F ebm Two-dimensional lookup table diagram.

[0059] Figure 6 This is a schematic diagram of a split-road braking test method based on active sideslip angle adjustment and electric braking, as described in this invention. Detailed Implementation

[0060] 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.

[0061] A cross-system redundant braking control method based on active sideslip angle adjustment, characterized in that,

[0062] like Figure 1 As shown, this method is used for vehicle braking control and is applicable to four-wheel distributed electric drive vehicles equipped with a front-wheel distributed independent steering system. The configuration includes: left front wheel 101, right front wheel 102, left rear wheel 103, right rear wheel 104, left front wheel brake 201, right front wheel brake 202, left rear wheel brake 203, right rear wheel brake 204, left front drive system 301, right front drive system 302, left rear drive system 303, right rear drive system 304, left front steering system 401, right front steering system 402, brake controller 502, drive controller 503, steering controller 504, and vehicle controller 501.

[0063] The vehicle controller 501 is connected to the brake controller 502, the drive controller 503, and the steering controller 504 via a communication bus. The brake controller 502 is connected to the left front wheel brake 201, right front wheel brake 202, left rear wheel brake 203, and right rear wheel brake 204 via signal lines, thereby controlling the braking force of the left front wheel 101, right front wheel 102, left rear wheel 103, and right rear wheel 104. The drive controller 503 is connected to the left front drive system 301, right front drive system 302, left rear drive system 303, and right rear drive system 304 via signal lines, thereby controlling the driving force and electric braking force of the left front wheel 101, right front wheel 102, left rear wheel 103, and right rear wheel 104. The steering controller 504 is connected to the left front steering system 401 and right front steering system 402 via signal lines, thereby controlling the wheel steering angle of the left front wheel 101 and right front wheel 102 respectively.

[0064] This method is mainly applied to the front axle of vehicles with insufficient electric redundant braking force and high braking force demand; while for the rear axle of vehicles with sufficient electric redundant braking force and low braking force demand, if the left rear wheel brake 203 or the right rear wheel brake 204 fails, electric braking should be mainly used for redundant braking control in order to ensure vehicle braking stability and safety as much as possible.

[0065] like Figure 2 As shown, this method is stored in the vehicle controller 501, and the specific process is as follows: Figure 2 As shown:

[0066] Step 1: The vehicle controller 501 receives braking commands in real time and calculates the braking force required by the front axle of the vehicle under the current operating conditions as 2F according to the braking force distribution rules. bF The required braking forces for the left front wheel 101 and the right front wheel 102 are F respectively. bF ,F bF The braking deceleration required for the entire vehicle is 2F. bF / m, (m is the vehicle mass); the braking force distribution rule is a front and rear axle braking force distribution curve formulated according to the ideal front and rear axle braking force distribution I curve, or a front and rear axle braking force distribution curve formulated under the premise of meeting braking regulations, so as to ensure the smooth and safe braking of the vehicle as much as possible.

[0067] Step 2: The vehicle controller 501 determines whether the left front wheel brake 201 or the right front wheel brake 202 is malfunctioning. If the left front wheel brake 201 is malfunctioning, proceed to step 3; if the right front wheel brake 202 is malfunctioning, proceed to step 5; if both the left front wheel brake 201 and the right front wheel brake 202 are malfunctioning, proceed to step 7; if neither the left front wheel brake 201 nor the right front wheel brake 202 is malfunctioning, proceed to step 12. The vehicle controller 501 can determine whether the left front wheel brake 201 or the right front wheel brake 202 is malfunctioning by using vehicle deceleration, yaw rate status information, the rotation angle and current signal of the left front wheel brake 201 actuator motor, and the rotation angle and current signal of the right front wheel brake 202 actuator motor. It can also determine whether the vehicle body is yawing to the left or to the right.

[0068] Step 3: If |F bF |≤|F ebm |(F in the formula) ebm Given the maximum electric braking force that the left front drive system 301 and the right front drive system 302 can achieve under the current operating conditions, the vehicle controller 501 controls the left front wheel brake 201 and the right front wheel brake 202 to generate braking forces O and F respectively through the brake controller 502. bF The drive controller 503 controls the left front drive system 301 and the right front drive system 302 to simultaneously generate F. bF The electric braking force of 0, thereby generating the braking force 2F required by the front axle of the vehicle. bF Then proceed to step nine; if |F is not satisfied bF |≤|F ebm If | then proceed to step four;

[0069] Step 4: The vehicle controller 501 controls the left front wheel brake 201 and the right front wheel brake 202 to generate braking forces F and F respectively through the brake controller 502. ebm The drive controller 503 controls the left front drive system 301 and the right front drive system 302 to simultaneously generate F. ebm The electric braking force of 0 is required to achieve the braking deceleration of 2F for the entire vehicle. bF Under the / m requirement, through |θ bF |vs F ebm In the two-dimensional lookup table diagram, the steering controller 504 controls the left front steering system 401 and the right front steering system 402 to simultaneously generate the current F. ebm Corresponding θ bFL θ bFR The wheel steering angle, where θ bFL=-θ bFR This generates the braking force 2F required for the front axle of the vehicle. bF Then proceed to step nine;

[0070] Step 5: If |F bF |≤|F ebm Then, the vehicle controller 501 controls the left front wheel brake 201 and the right front wheel brake 202 to generate braking force F through the brake controller 502. bF Simultaneously, the drive controller 503 controls the left front drive system 301 and the right front drive system 302 to simultaneously generate 0 and F respectively. bF The electric braking force generates the braking force 2F required for the front axle of the vehicle. bF Then proceed to step nine; if |F is not satisfied bF |≤|F ebm If so, proceed to step six;

[0071] Step 6: The vehicle controller 501 controls the left front wheel brake 201 and the right front wheel brake 202 to generate braking force F through the brake controller 502. ebm The drive controller 503 controls the left front drive system 301 and the right front drive system 302 to simultaneously generate 0 and F respectively. ebm The electric braking force, at the braking deceleration required by the vehicle 2F bF Under the / m requirement, through |θ bF |vs F ebm In the two-dimensional lookup table diagram, the steering controller 504 controls the left front steering system 401 and the right front steering system 402 to simultaneously generate the current F. ebm Corresponding θ bFL θ bFR The wheel steering angle, where θ bFL =-θ bFR This generates the braking force 2F required for the front axle of the vehicle. bF Then proceed to step nine;

[0072] Step 7: If |F bF |≤|F ebm Then, the vehicle controller 501 controls the left front drive system 301 and the right front drive system 302 to simultaneously generate F through the drive controller 503. bF F bF The electric braking force generates the braking force 2F required for the front axle of the vehicle. bF Then proceed to step nine; if |F is not satisfied bF |≤|F ebm If |, then proceed to step eight;

[0073] Step 8: The vehicle controller 501 controls the left front drive system 301 and the right front drive system 302 to simultaneously generate F through the drive controller 503. ebm F ebm The electric braking force, at the braking deceleration required by the vehicle 2F bF Under the / m requirement, through |θ bF |vs F ebm In the two-dimensional lookup table diagram, the steering controller 504 controls the left front steering system 401 and the right front steering system 402 to simultaneously generate the current F. ebm Corresponding θ bFL θ bFR The wheel steering angle, where θ bFL =-θ bFR This generates the braking force 2F required for the front axle of the vehicle. bF Then proceed to step nine;

[0074] Step 9: The vehicle controller 501 determines the yaw direction of the vehicle body based on the vehicle yaw rate status information. If the vehicle body yaws to the left, then proceed to step 10; if the vehicle body yaws to the right, then proceed to step 11; if the vehicle body does not yaw, then proceed to step 13.

[0075] Step 10: The vehicle controller 501 controls the right rear wheel brake 204 to generate braking force ΔF through the brake controller 502. M This generates an additional yaw moment to correct the vehicle body yaw, and then determines whether the vehicle body has stopped yawing. If it is still yawing, proceed to step nine.

[0076] Step 11: The vehicle controller 501 controls the left rear wheel brake 203 to generate braking force ΔF through the brake controller 502. M This generates an additional yaw moment to correct the vehicle body yaw, and then determines whether the vehicle body has stopped yawing. If it is still yawing, proceed to step nine.

[0077] Step 12: The vehicle controller 501 controls the left front wheel brake 201 and the right front wheel brake 202 to generate braking force F respectively through the brake controller 502. bF F bF This generates the braking force 2F required by the front axle of the vehicle. bF The vehicle controller 501 controls the left front steering system 401 and the right front steering system 402 to perform normal steering control through the steering controller 504;

[0078] Step 13: The current loop ends. Return to Step 1 to start the next loop control.

[0079] In steps four, six, and eight above, the |θ bF |vs F ebm Two-dimensional lookup tables can be obtained through test vehicle calibration.

[0080] like Figure 3 As shown, the |θ bF |vs F ebm The two-dimensional lookup table is stored in the vehicle controller 501.

[0081] First, taking the forward direction of the test vehicle as a reference, the left turn of the wheel and the turning angle value are defined as positive, and θ is... bFL >0, the θ bFR >0; the wheel turns right, the turning angle value is negative, the θ bFR <0, the θ bFL <0;

[0082] like Figure 4 As shown, when the θ bFR >0, the θ bFL When <0, the current steering mode is defined as yaw steering;

[0083] like Figure 5 As shown, when the θ bFR <0, the θ bFL When the value is greater than 0, the current steering mode is defined as outward steering.

[0084] |θ bF | Defined as the absolute value of the front wheel steering angle, satisfying the following relationship:

[0085] |θ bF |=|θ bFL |=|θ bFR |

[0086] The following tests were conducted on a flat, straight, and uniform road surface:

[0087] Experiment 1: The test vehicle was first accelerated to a speed of 100 km / h, then the driving force was reduced to 0. Starting 0.5 seconds after the driving force was reduced to 0, the θ... bFL With the θ bFR Both remain at 0. The left front drive system 301 and the right front drive system 302 generate an electric braking force F that increases linearly from 0N with a slope of 1000N / s. ebm When the left or right front wheel locks up, the application of electric braking force is stopped until the test vehicle comes to a stop. The braking deceleration F corresponding to 0.1g, 0.2g, 0.3g, 0.4g, and 0.5g during the above process is recorded respectively. ebm , as the |θ bF |vs Febm The starting point of the horizontal axis of a two-dimensional lookup table;

[0088] Test 2: The test vehicle was first accelerated to a speed of 100 km / h, and the driving force was reduced to 0. Starting from 0.5 seconds after the driving force was reduced to 0, the steering controller 504 controlled the θ of the left front steering system 401. bFL Starting from 0°, the angle changes linearly at a slope of 10° / s until it reaches -90°. Simultaneously, the steering controller 504 controls the θ of the right front steering system 402. bFR Starting from 0°, the steering angle changes linearly at a slope of 10° / s until it reaches 90°. The current steering method is the inward octagon steering. The electric braking force F ebm Keep the value at 0 until the test vehicle stops. Record the corresponding |θ| for braking decelerations of 0.1g, 0.2g, 0.3g, 0.4g, and 0.5g during the above process. nF |, as the |θ bF |vs F ebm The starting point of the vertical axis of a two-dimensional lookup table;

[0089] Test 3: The test vehicle was first accelerated to a speed of 100 km / h, and the driving force was reduced to 0. Starting from 0.5 seconds after the driving force was reduced to 0, the steering controller 504 controlled the θ of the left front steering system 401. bFL Starting from 0°, the angle changes linearly at a slope of 10° / s until it reaches -90°. Simultaneously, the steering controller 504 controls the θ of the right front steering system 402. bFR Starting from 0°, the steering angle changes linearly at a slope of 10° / s until it reaches 90°. The current steering method is the inward octagon steering. The electric braking force F is then... ebm Five tests were conducted with braking decelerations of 500N, 1000N, 1500N, 2000N, and 2500N, respectively. The corresponding values ​​of |θ| were recorded for each deceleration: 0.1g, 0.2g, 0.3g, 0.4g, and 0.5g. bF |and F ebm , as the |θ bF |vsF ebm Vertical scatter plot of a two-dimensional lookup table;

[0090] Experiment 4: The test vehicle first accelerates to a speed of 100 km / h, then reduces the driving force to 0. Starting 0.5 seconds after the driving force reduces to 0, the |θ... bF Maintain the angles at 0°, 10°, 20°, 30°, 40°, 50°, and 60°, perform 5 tests, and ensure that the stated θ... bFR >0, the θ bFL<0, the current steering mode is the inward octagon steering, the left front drive system 301 and the right front drive system 302 generate linearly increasing electric braking force F starting from 0N with a slope of 1000N / s. ebm When the left front wheel 101 or the right front wheel 102 locks up, the application of electric braking force is stopped until the test vehicle stops. The braking deceleration F corresponding to 0.1g, 0.2g, 0.3g, 0.4g, and 0.5g during the above process is recorded respectively. ebm and |θ bF |, as the |θ bF |vs F ebm Horizontal scatter points of a two-dimensional lookup table chart;

[0091] The coordinate points obtained from the above experiment were divided into 5 groups according to the braking decelerations of 0.1g, 0.2g, 0.3g, 0.4g, and 0.5g. Five curves were fitted to each group to form the |θ|. bF |vs F ebm Two-dimensional lookup table, through the aforementioned |θ bF |vs F ebm By interpolating and looking up the table using a two-dimensional lookup table, we can obtain the value of any F under the current road surface adhesion conditions and when the steering mode is the inward yaw. ebm and the θ bFL With the θ bFR The correspondence.

[0092] Similar to Experiment 1, Experiment 2, Experiment 3, and Experiment 4, the |θ| can be obtained when the steering mode is the outward octagonal steering. bF |vs F ebm Two-dimensional lookup table diagram.

[0093] Furthermore, under the same other test conditions, the |θ| was tested under different road surface adhesion conditions. bF |vsF ebm The two-dimensional lookup table is drawn to obtain multiple sets of |θ under various road surface adhesion conditions. bF |vs F ebm Two-dimensional lookup table diagram.

[0094] In steps four, six, and eight above, the specific choice between the inward-facing and outward-facing steering is determined through a road braking test:

[0095] Due to differences in the front axle suspension structure of different vehicles, the lateral stability of the vehicle body differs when performing outward or inward steering. Therefore, for a specific target vehicle, the split-road braking test is needed to determine whether to use inward or outward steering when performing front axle reinforced redundant braking. The split-road braking test method is as follows:

[0096] like Figure 6 As shown, the test section is 100m long and 5m wide, with the left half being a high-adhesion surface and the right half a low-adhesion surface. The target vehicle travels in a straight line at a speed of 20km / h, with its centerline aligned with the centerline of the test section. Three meters before entering the test section, the driving force is reduced to 0, and the left front wheel 101 and right front wheel 102 are made to perform an outward yaw steering maneuver with a steering angle of 10°. The yaw rate of the vehicle during this process is recorded. Under the same test conditions, a second test is conducted, with the left and right front wheels performing an inward yaw steering maneuver with a steering angle of 10°, and the yaw rate of the vehicle during this process is recorded. By comparing the magnitudes of the yaw rates in the two experiments, the steering method with the smaller yaw rate is selected as the steering method used by the target vehicle when performing front axle reinforced redundant braking.

[0097] In steps ten and eleven above, the corrective force ΔF M Determined using the following method:

[0098] The corrective force ΔF M The PID control algorithm, stored in the vehicle controller 501, is used for calculation. The input to the PID control algorithm is the difference between the target yaw rate and the actual yaw rate, and the output is the corrective force ΔF. M The target yaw rate is 0, and the PID algorithm is as follows:

[0099]

[0100] Among them, K p ,K d ,K i These are the proportional, derivative, and integral gains, respectively; their specific values ​​are calibrated based on the actual situation. ω r The actual yaw rate is given.

[0101] 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 front axle enhanced redundant braking method based on active sideslip angle adjustment and electric braking, characterized in that: This redundant braking method is used for electric vehicles with a steer-by-wire chassis equipped with a four-wheel independent steer-by-wire braking system and a front-wheel distributed independent steering system. This type of vehicle includes: a left front wheel brake, a right front wheel brake, a left rear wheel brake, a right rear wheel brake, a left front drive system, a right front drive system, a left rear drive system, a right rear drive system, a left front steering system, a right front steering system, a brake controller, a drive controller, a steering controller, and a vehicle controller. This method is stored in the vehicle controller, and the specific process is as follows: The vehicle controller first determines whether the left front wheel brake or the right front wheel brake is malfunctioning, and calculates the braking force F distributed to the left and right front wheels according to the braking force distribution rules under the current operating conditions. bF ,F bF Compare the maximum electric braking force F of the left front drive system and the right front drive system under the current operating conditions. ebm The braking force of the left front wheel brake, the braking force of the right front wheel brake, the electric braking force of the left front drive system, the electric braking force of the right front drive system, and the steering angle θ of the left front wheel. bFL and the steering angle θ of the right front wheel bFR Distribute; If either the left or right front wheel brake fails, and if |F bF |≤|F ebm Then the vehicle controller controls the brakes of the non-faulty wheels to generate F through the brake controller. bF The braking force is generated by the drive system of the faulty wheel through the drive controller. bF Electric braking force; if |F bF |≤|F ebm The vehicle controller controls the brakes of the non-faulty wheels to generate F through the brake controller. ebm The braking force is generated by the drive system of the faulty wheel through the drive controller. ebm The electric braking force, utilizing |θ bF |vs F ebm Two-dimensional lookup table to obtain the current F ebm and |θ bF The combination of | allows the steering controller to simultaneously generate θ for the left front steering system and the right front steering system. bFL θ bFR The wheel steering angle, where θ bFL =-θ bFR ,|θ bFL |=|θ bFR |=|θ bF |, used to satisfy the vehicle's front axle component being 2F bF Braking deceleration requirement of / m; When both the left and right front wheel brakes fail, if |F bF |≤|F ebm The vehicle controller, through the drive controller, controls the left front drive system and the right front drive system to generate F respectively. bF F bF Electric braking force; if |F bF |≤|F ebm The vehicle controller, through the drive controller, controls the left front drive system and the right front drive system to simultaneously generate F. ebm F ebm The electric braking force, utilizing |θ bF |vs F ebm Two-dimensional lookup table to obtain the current F ebm and |θ bF The combination of | allows the steering controller to simultaneously generate θ for the left front steering system and the right front steering system. bFL θ bFR The wheel steering angle, where θ bFL =-θ bFR ,|θ bFL |=|θ bFR |=|θ bF |, used to satisfy the vehicle's front axle component being 2F bF Braking deceleration requirement of / m; When neither the left nor the right front wheel brake malfunctions, the vehicle controller, through the brake controller, controls the left and right front wheel brakes to generate braking force F respectively. bF F bF At the same time, the left rear wheel brake and the right rear wheel brake are controlled to generate braking force as required according to the braking force distribution rules. When the vehicle controller determines that the vehicle body sways to the left during braking, the vehicle controller controls the right rear wheel brake to generate a corrective force ΔF through the brake controller. M This generates an additional yaw moment to correct vehicle body yaw; when the vehicle controller determines that the vehicle body yaws to the right during braking, the vehicle controller controls the left rear wheel brake through the brake controller to generate the corrective force ΔF. M This generates an additional yaw moment to correct the vehicle body yaw.

2. The front axle reinforced redundant braking method based on active sideslip angle adjustment and electric braking as described in claim 1, characterized in that, This method is mainly applied to the front axle of vehicles with insufficient electric redundant braking force and high braking force demand; while for the rear axle of vehicles with sufficient electric redundant braking force and low braking force demand, if the left rear wheel brake or the right rear wheel brake fails, the electric drive system should be mainly used to implement electric braking for redundant braking control in order to ensure vehicle braking stability and safety as much as possible.

3. The front axle reinforced redundant braking method based on active sideslip angle adjustment and electric braking as described in claim 1, characterized in that, The vehicle controller is connected to the brake controller, drive controller, and steering controller via a communication bus. The brake controller is connected to the left front wheel brake, right front wheel brake, left rear wheel brake, and right rear wheel brake via signal lines, thereby independently controlling the braking force of the four wheels. The drive controller is connected to the left front drive system, right front drive system, left rear drive system, and right rear drive system via signal lines, thereby controlling the driving force and electric braking force of the four wheels. The steering controller is connected to the left front steering system and right front steering system via signal lines, thereby controlling the steering angle of the left front wheel and right front wheel respectively.

4. The front axle reinforced redundant braking method based on active sideslip angle adjustment and electric braking as described in claim 1, characterized in that, The braking force distribution rule is a front and rear axle braking force distribution curve formulated according to the ideal front and rear axle braking force distribution curve I, or a front and rear axle braking force distribution curve formulated under the premise of meeting braking regulations, so as to ensure the smooth and safe braking of the vehicle as much as possible.

5. The front axle reinforced redundant braking method based on active sideslip angle adjustment and electric braking as described in claim 1, characterized in that, The vehicle controller can determine whether the left and right front wheel brakes are malfunctioning by using information on vehicle deceleration, yaw rate, the rotation angle and current signal of the left front wheel brake actuator motor, and the rotation angle and current signal of the right front wheel brake actuator motor. It can also determine whether the vehicle body is yawing to the left or to the right.

6. The front axle reinforced redundant braking method based on active sideslip angle adjustment and electric braking as described in claim 1, characterized in that, The |θ bF |vs F ebm Two-dimensional lookup tables can be obtained through test vehicle calibration, the specific process of which includes: First, taking the forward direction of the test vehicle as a reference, the turning angle value of the wheel turning left is defined as positive, and the turning angle value of the wheel turning right is defined as negative; When the θ bFR >0, the θ bFL When <0, the current steering mode is defined as yaw steering; When the θ bFR <0, the θ bFL When the value is greater than 0, the current steering mode is defined as outward steering. |θ bF | Defined as the absolute value of the front wheel steering angle, satisfying the following relationship: |θ bF |=|θ bFL |=|θ bFR | Through two sets of experiments, a set of |θ| corresponding to the inward yaw steering can be obtained. bF |vsF ebm Two-dimensional lookup table diagram, and a set of outward octagonal steering corresponding to |θ bf |vsF ebm Two-dimensional lookup table chart, experimental method as follows: The test vehicle underwent multiple braking tests under various road surface adhesion conditions using the aforementioned outward-facing eight-way steering method. Each test employed a different F-type braking technique. ebm and the aforementioned |θ bF The combination of | is used to record the braking deceleration of the test vehicle during the process. After multiple tests, the F under a certain braking deceleration can be determined. ebm and the aforementioned |θ bF The combined coordinates of |θ| are fitted to form a curve, and multiple curves corresponding to braking decelerations can then form a |θ|. bF |vsF ebm Two-dimensional lookup table diagram, various road surface adhesion conditions correspond to various |θ bF |vsF ebm A two-dimensional lookup table is used to obtain the F value under any road surface adhesion condition and any braking deceleration requirement when the vehicle performs the active sideslip angle adjustment in an outward eight-way steering mode. ebm and the aforementioned |θ bF | combinations; Similar to the above experimental method, a set of |θ values ​​can also be obtained when steering with the inward octagonal turn. bF |vsF ebm Using a two-dimensional lookup table, when the vehicle performs the active sideslip angle adjustment with an inward-facing steering configuration, the F value under any road surface adhesion condition and any braking deceleration requirement can be obtained. ebm and the aforementioned |θ bF The combination of |.

7. The front axle reinforced redundant braking method based on active sideslip angle adjustment and electric braking as described in claim 6, characterized in that, For a specific vehicle, the choice between inward-pointing and outward-pointing steering during the active sideslip angle adjustment is determined through a split-road braking test. The specific test method is as follows: The vehicle is instructed to travel in a straight line onto a split road surface, which is divided into a high-friction surface and a low-friction surface according to the vehicle's direction of travel. The vehicle travels with a relatively small |θ|. bF Perform both inward and outward yaw rates and record the corresponding vehicle yaw rate values ​​for each steering method. If the yaw rate of a vehicle is lower when performing inward yaw rate, then the vehicle should preferentially use inward yaw rate for active sideslip angle adjustment; otherwise, it should preferentially use outward yaw rate for active sideslip angle adjustment.

8. The front axle reinforced redundant braking method based on active sideslip angle adjustment and electric braking as described in claim 1, characterized in that, The corrective force ΔF M The following is determined using a PID control algorithm based on the yaw rate tracking error: Among them, K p ,K d ,K i These are the proportional, derivative, and integral gains, respectively, ω. r This represents the vehicle's current actual yaw rate.

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