A redundant braking control method, system and vehicle for an electric vehicle

Abstract

The application provides a redundancy brake control method, system and vehicle for an electric vehicle. When the main hydraulic brake system fails, the existing actuator resources of the vehicle are fully utilized without adding an independent hydraulic redundancy unit, the limitations of insufficient adhesion of the rear wheels and motor feedback restricted by the battery state are overcome, and stable, efficient and regulatory deceleration-requiring redundancy braking is realized. The method comprises: when the main brake system is identified to fail, controlling an electronic parking brake device to apply a first brake torque to the front wheels of the vehicle and controlling a drive motor to apply a second brake torque to the rear wheels of the vehicle in response to a deceleration signal of an upper controller; obtaining wheel slip rate and deceleration of the vehicle; adjusting the first brake torque and / or the second brake torque according to the wheel slip rate and the deceleration; and wherein the sum of the first brake torque and the second brake torque is equal to the total brake torque required by the vehicle braking.

Description

Technical Field

[0001] This application relates to the field of vehicle control, specifically to a redundant braking control method, system, and vehicle for an electric vehicle. Background Technology

[0002] With the rapid development of new energy vehicles and autonomous driving technology, the safety and reliability of vehicle braking systems have become increasingly important concerns. As a key component of vehicle active safety, the redundant braking capability of the service braking system in the event of failure directly affects the safety of the vehicle and its occupants.

[0003] Currently, mainstream new energy vehicles are typically equipped with integrated electro-hydraulic braking systems (such as IBCU, OneBox, etc.) as the main service braking system to achieve functions such as conventional braking, energy recovery braking, and stability control. However, when the main hydraulic braking system experiences electrical faults, hydraulic leaks, or control unit failures, the vehicle will lose all or part of its hydraulic braking force, urgently requiring reliance on backup braking methods to decelerate and stop.

[0004] In the prior art, to ensure driving safety after the failure of the main braking system, the common approach is to add an independent redundant hydraulic braking unit (RBU). This means that an additional complete hydraulic braking module is configured in addition to the main hydraulic braking unit. This module includes an independent electronic control unit, a plunger pump, a solenoid valve group, and hydraulic lines. It independently builds pressure to provide backup braking force when the main braking system fails. However, this approach has the following drawbacks: (1) It requires an additional redundant hydraulic unit and its auxiliary components, which significantly increases the overall vehicle cost; (2) The increase in hydraulic lines and valve bodies increases the system complexity and occupies chassis layout space; (3) The overall vehicle weight increases, which is not conducive to lightweighting and energy consumption optimization.

[0005] To address this, some existing technologies attempt to utilize the vehicle's existing regenerative braking and electronic parking brake (EPB) systems to achieve redundant braking, replacing additional hydraulic redundant units. For example, in the event of main braking system failure, energy recovery braking is performed via the drive motor, combined with auxiliary braking via EPB. However, this approach still faces the following technical challenges in practical applications:

[0006] Firstly, EPB (Electronic Braking Brake) is typically located on the rear wheels of a vehicle, and is conventionally understood to be used only for parking braking. When a vehicle brakes suddenly, inertia causes the vehicle's center of gravity to shift forward, significantly increasing the load on the front axle while decreasing the load on the rear axle, thus reducing the adhesion between the rear wheels and the road surface. At this time, if the rear-wheel EPB is relied upon to provide significant braking force, the rear wheels are highly likely to exceed the road surface adhesion limit, resulting in wheel lock-up or slippage. This not only fails to provide sufficient deceleration but may also lead to vehicle instability, posing a safety hazard. If the braking force output of the EPB is limited to avoid lock-up, the overall deceleration of the redundant braking system may not meet the minimum braking performance standards required by regulations.

[0007] Secondly, the regenerative braking capability of the electric motor is limited by the state of charge (SOC) of the battery and the ambient temperature. When the battery's charge is high (e.g., near full charge) or in a low-temperature environment, the battery's charging acceptance is limited, and the regenerative braking of the electric motor cannot be fully implemented or must operate at a reduced rate. Otherwise, it may lead to overcharging, lithium plating, or battery degradation, affecting battery life and safety. Furthermore, when the vehicle speed is too low, the efficiency of the regenerative braking of the electric motor decreases significantly, resulting in insufficient braking torque output. Under these conditions, relying solely on the regenerative braking of the electric motor is insufficient to provide stable and sufficient redundant braking force.

[0008] In summary, how to achieve stable, efficient, and regulatory-compliant redundant braking when the main hydraulic braking system fails, without adding an independent hydraulic redundancy unit, by making full use of the vehicle's existing actuator resources, overcoming the limitations of insufficient rear wheel adhesion and the constraints of motor feedback on battery status, has become a pressing technical problem to be solved in this field. Summary of the Invention

[0009] This application provides a redundant braking control method, system, and vehicle for electric vehicles. When the main hydraulic braking system fails, it makes full use of the vehicle's existing actuator resources without adding an independent hydraulic redundancy unit, overcoming the limitations of insufficient rear wheel adhesion and motor feedback constrained by battery status, and achieving stable, efficient, and regulatory-compliant redundant braking.

[0010] The technical solution of this application is as follows:

[0011] A redundant braking control method for electric vehicles includes:

[0012] When a failure of the main braking system is detected, the electronic parking brake is controlled to apply a first braking torque to the front wheels of the vehicle in response to the deceleration signal from the upper controller, and the drive motor is controlled to apply a second braking torque to the rear wheels of the vehicle.

[0013] Obtain the wheel slip ratio and deceleration of the vehicle;

[0014] Adjust the first braking torque and / or the second braking torque according to the wheel slip ratio and the deceleration;

[0015] Wherein, the sum of the first braking torque and the second braking torque is equal to the total braking torque required for the vehicle to brake.

[0016] Preferably, the method is executed by an existing domain controller or independent controller on the vehicle, the domain controller or independent controller being communicatively connected to the electronic parking brake and the drive motor respectively, and the control software of the electronic parking brake is integrated into the domain controller or independent controller.

[0017] Preferably, the steps of controlling the electronic parking brake to apply a first braking torque to the front wheels of the vehicle and controlling the drive motor to apply a second braking torque to the rear wheels of the vehicle include:

[0018] The drive motor is preferentially controlled to apply the second braking torque to the rear wheel;

[0019] When the second braking torque reaches the current maximum recovery capacity of the drive motor and the second braking torque is less than the total braking torque, the electronic parking brake device is controlled to apply the first braking torque to the front wheels to compensate for the difference between the second braking torque and the total braking torque.

[0020] The current maximum recovery capacity of the drive motor is determined based on the state of charge of the power battery and the ambient temperature.

[0021] Preferably, the step of adjusting the first braking torque and / or the second braking torque according to the wheel slip ratio and the deceleration includes:

[0022] When the deceleration is less than the target deceleration, on the premise of ensuring that the slip ratio of each wheel does not exceed the preset slip ratio threshold, the first braking torque and / or the second braking torque are increased until the deceleration reaches the target deceleration;

[0023] When the deceleration is greater than the target deceleration, the first braking torque and / or the second braking torque are reduced until the deceleration is equal to the target deceleration.

[0024] Preferably, the method further includes:

[0025] When the total braking torque decreases and the second braking torque is less than or equal to the reduced total braking torque, the first braking torque is released first.

[0026] Preferably, before the steps of controlling the electronic parking brake to apply a first braking torque to the front wheels of the vehicle and controlling the drive motor to apply a second braking torque to the rear wheels of the vehicle, the method further includes:

[0027] Obtain the state of charge of the vehicle's power battery and the vehicle speed;

[0028] The distribution ratio of the first braking torque to the second braking torque is determined based on the state of charge of the power battery and the vehicle speed.

[0029] Preferably, the step of obtaining the failure signal of the main braking system includes:

[0030] The status signals sent by the main braking system are received through the first CAN bus and the second CAN bus, respectively.

[0031] When neither the first CAN bus nor the second CAN bus receives the status signal, or when both the first CAN bus and the second CAN bus receive the fault flag bit, the main braking system is determined to have failed.

[0032] Preferably, the method further includes:

[0033] When the vehicle needs to be stationary, the electronic parking brake device is controlled to remain clamped.

[0034] When the vehicle needs to start, the driving force of the vehicle is acquired, and when the driving force is greater than a preset driving force threshold, the electronic parking brake device is controlled to release.

[0035] This application also provides a redundant braking control system for an electric vehicle, comprising:

[0036] An electronic parking brake device, connected to the front wheels of the vehicle, is used to apply a first braking torque to the front wheels;

[0037] A drive motor, connected to the rear wheel of the vehicle, is used to apply a second braking torque to the rear wheel;

[0038] A redundant controller is communicatively connected to the electronic parking brake device and the drive motor, respectively, and is used to execute the redundant braking control method of the electric vehicle as described above. The control software of the electronic parking brake device is integrated into the redundant controller, which is an existing domain controller or an independent controller on the vehicle.

[0039] This application also provides a vehicle including the aforementioned redundant braking control system for electric vehicles.

[0040] The beneficial effects of this application are as follows:

[0041] By placing the electronic parking brake (EPB) on the front wheels, the axle load transfer effect caused by inertia during braking allows the front wheels to gain greater road adhesion. Combined with energy recovery braking from the rear-wheel drive motor, this creates a differentiated redundant braking architecture consisting of mechanical braking on the front axle and electric braking on the rear axle. Compared to existing technologies that place the EPB on the rear wheels, this application effectively avoids the problem of insufficient adhesion on the rear wheels due to load transfer, significantly increasing the deceleration limit of the redundant braking system. It meets the minimum braking deceleration standards required by regulations without the need for an additional hydraulic redundant unit (RBU).

[0042] By integrating the control software of the electronic parking brake into the vehicle's existing domain controller or independent controller, and reusing the vehicle's existing electronic parking brake and drive motor as redundant brake actuators, this application eliminates the need for a separate redundant hydraulic control unit (RBU) or an additional dedicated brake controller. Compared to existing technologies that add independent redundant hydraulic units, this application reduces additional hardware such as hydraulic lines, valve bodies, and piston pumps, thereby lowering overall vehicle manufacturing costs, system complexity, and chassis layout space requirements, and contributing to vehicle lightweighting.

[0043] During redundant braking, the rear-wheel drive motor is used first for energy recovery braking. The front wheel EPB is only activated to supplement the motor when its recovery capacity is insufficient. When the deceleration demand decreases, the EPB braking torque is released first while the motor recovery torque is retained. This maximizes the conversion of the vehicle's braking kinetic energy into electrical energy to recharge the power battery, reducing energy loss and wear of braking components caused by mechanical friction braking, and improving energy utilization efficiency and vehicle range.

[0044] By collecting wheel speed signals of each wheel in real time through wheel speed sensors, calculating the slip ratio of each wheel and the deceleration of the whole vehicle, when the slip ratio of a certain wheel deviates from the optimal slip ratio range, adjustment commands are sent to the electronic parking brake device or drive motor respectively to dynamically adjust the braking torque of the corresponding axle, so that the slip ratio of each wheel is always maintained within the optimal slip ratio range, preventing wheel lock-up or slippage, realizing the anti-lock braking function under redundant braking conditions, and ensuring braking directional stability and driving safety. Attached Figure Description

[0045] Figure 1 This is an architecture diagram of the redundant braking control system for an electric vehicle in an embodiment of this application;

[0046] Figure 2 This is a flowchart of the redundant braking control method for an electric vehicle in an embodiment of this application. Detailed Implementation

[0047] Reference Figure 1This application provides a redundant braking control system for an electric vehicle, comprising:

[0048] The electronic parking brake (EPB) is connected to the front wheels of the vehicle and is used to apply a first braking torque to the front wheels.

[0049] The drive motor is connected to the rear wheels of the vehicle and is used to apply a second braking torque to the rear wheels;

[0050] The redundant controller is connected to the electronic parking brake and the drive motor respectively, and the control software of the electronic parking brake is integrated into the redundant controller.

[0051] The redundant braking control system provided in this application embodiment does not activate when the vehicle's main braking system is working normally. The redundant controller only takes over braking control when the main braking system malfunctions and cannot provide effective braking force. The vehicle's main braking system includes... Figure 1 The integrated brake control unit (IBCU) integrates the master cylinder, electric booster, hydraulic control unit, and electronic control unit, and is used to perform conventional hydraulic braking control of the vehicle in response to service braking requests.

[0052] In this embodiment of the main braking system, the rear wheel brakes are replaced with drum brakes instead of conventional disc brakes. This leverages the approximately 10% cost advantage of drum brakes over disc brakes, further reducing the overall vehicle braking system manufacturing cost while maintaining basic rear wheel braking performance. Since the rear wheels primarily rely on the drive motor for energy recovery braking under redundant braking conditions, and the motor-driven regenerative braking bears most of the rear wheel braking load, the frequency and intensity of use of the rear wheel mechanical brakes are significantly reduced. Therefore, replacing the rear wheel brakes with drum brakes will not substantially affect the overall vehicle braking performance or braking comfort. Through this differentiated brake configuration (front disc, rear drum), this application achieves further cost optimization of the braking system while ensuring braking safety and comfort.

[0053] In this embodiment, the integrated brake control unit is communicatively connected to the redundant controller, as shown in the reference. Figure 2When the integrated brake control unit malfunctions, it sends a failure signal to the redundant controller, or the redundant controller actively detects the failure status of the integrated brake control unit (corresponding to step S1). The main braking system performs real-time self-monitoring. When it detects a fault in its own system, it sends a main braking system fault signal to the redundant controller. Simultaneously, the redundant controller also monitors the main braking system for faults or communication loss. The redundant controller receives status signals from the main braking system via the first and second CAN buses. If neither the first nor the second CAN bus receives a status signal, or if both the first and second CAN buses receive a fault flag, the redundant controller determines that the main braking system has failed. When both CAN signals from the main braking system are lost, or both CAN signals issue a fault flag, the redundant controller determines that the main braking system has failed and takes over the vehicle's braking control.

[0054] The redundant controller is an existing domain controller on the vehicle (such as...). Figure 1 The redundant controller can be either a vehicle body domain controller (VIU) or an independent controller. After taking over the braking control of the entire vehicle, the redundant controller responds to the deceleration request of the intelligent driving system. That is, the domain controller system, which integrates the electronic parking brake control software, controls the electronic parking brake of the front wheels and the drive motor of the rear wheels for redundant braking control.

[0055] When the main braking system fails, the redundant controller receives a deceleration signal from the upper-level controller. In response to this signal, the redundant controller sends a first braking command to the electronic parking brake to apply a first braking torque to the front wheels. Simultaneously, the redundant controller sends a second braking command to the drive motor to apply a second braking torque to the rear wheels. The sum of the first and second braking torques equals the total braking torque required for vehicle braking.

[0056] In one implementation of this application, the steps of the redundant controller controlling the electronic parking brake to apply a first braking torque to the front wheels of the vehicle and controlling the drive motor to apply a second braking torque to the rear wheels of the vehicle specifically include: prioritizing the drive motor to apply the second braking torque to the rear wheels; when the second braking torque reaches the current maximum recovery capacity of the drive motor and the second braking torque is less than the total braking torque, controlling the electronic parking brake to apply the first braking torque to the front wheels to compensate for the difference between the second braking torque and the total braking torque. The current maximum recovery capacity of the drive motor is determined based on the state of charge of the power battery and the ambient temperature.

[0057] In this application, the electronic parking brake is positioned on the front wheels to utilize the axle load transfer effect caused by inertia during braking. Specifically, when the vehicle brakes suddenly, the center of gravity shifts forward, increasing the load on the front axle and consequently increasing the adhesion between the front wheels and the road surface. Therefore, positioning the electronic parking brake on the front wheels fully utilizes the higher road adhesion of the front wheels, allowing the electronic parking brake to output greater braking force without easily locking up or slipping, thereby increasing the deceleration limit of the redundant braking system. Simultaneously, the drive motor is positioned on the rear wheels, applying braking torque to the rear wheels through energy recovery. This not only shares the braking load of the front wheel electronic parking brake, reducing its wear and thermal fade risk, but also recovers some braking energy, improving energy utilization efficiency. The front wheel electronic parking brake and the rear wheel regenerative braking work together to form a differentiated redundant braking architecture of front axle mechanical braking and rear axle electric braking, achieving coordinated braking control of all four wheels.

[0058] Reference Figure 2 When determining the distribution ratio between the first braking torque output by the electronic parking brake and the second braking torque output by the drive motor, the redundant controller determines the distribution ratio based on the vehicle's power battery state of charge (SOC) and vehicle speed (step S2).

[0059] In step S2, when the state of charge of the power battery exceeds a preset charge threshold, it indicates that the power battery is close to full charge. In this state, if the drive motor performs regenerative braking, the generated electrical energy cannot be effectively absorbed by the power battery, potentially leading to overcharging and safety issues such as lithium plating, degradation, or even thermal runaway. Therefore, in this situation, the redundant controller determines that the second braking torque is zero, i.e., it disables the regenerative braking function of the drive motor and controls the electronic parking brake to apply only the first braking torque, which is equal to the total braking torque.

[0060] When the vehicle speed is lower than the preset speed threshold, the energy recovery efficiency of the drive motor is low under low-speed conditions, resulting in insufficient regenerative braking torque output and difficulty in providing effective braking. Therefore, in this situation, the redundant controller also determines that the second braking torque is zero, and the electronic parking brake device assumes all the total braking torque.

[0061] When the state of charge (SBC) of the power battery is not greater than a preset charge threshold and the vehicle speed is greater than a preset speed threshold, the redundant controller determines the distribution ratio of the first braking torque and the second braking torque based on the SBC and vehicle speed. Specifically, the distribution ratio is inversely correlated with the SBC, meaning that the lower the SBC, the stronger the energy recovery capability of the drive motor, and the larger the proportion of the second braking torque in the total braking torque. The distribution ratio is positively correlated with vehicle speed, meaning that the higher the vehicle speed, the higher the energy recovery efficiency of the drive motor, and the larger the proportion of the second braking torque in the total braking torque.

[0062] For example, when the state of charge of the power battery is less than 80% and the vehicle speed is greater than 60 km / h, the redundant controller determines that the second braking torque accounts for 60% to 80% of the total braking torque and the first braking torque accounts for 20% to 40% of the total braking torque; when the vehicle speed is between 20 km / h and 60 km / h, the redundant controller determines that the second braking torque accounts for 40% to 70% of the total braking torque and the first braking torque accounts for 30% to 60% of the total braking torque.

[0063] After determining the allocation ratio, the redundant controller sends a first braking command to the electronic parking brake device according to the allocation ratio, to control the electronic parking brake device to apply a first braking torque to the front wheels of the vehicle, and simultaneously sends a second braking command to the drive motor to control the drive motor to apply a second braking torque to the rear wheels of the vehicle (i.e., Figure 2 (Step S3 in the process). The sum of the first braking torque and the second braking torque is equal to the total braking torque required for vehicle braking.

[0064] In step S3, the redundant controller controls the electronic parking brake to apply a first braking torque to the front wheels of the vehicle and controls the drive motor to apply a second braking torque to the rear wheels of the vehicle. Specifically, a timing coordination strategy of motor priority and EPB supplementation is adopted.

[0065] Specifically, when responding to a deceleration and braking request from the intelligent driving system, the redundant controller prioritizes controlling the drive motor to apply a second braking torque to the rear wheels, that is, it prioritizes utilizing the energy recovery capability of the rear wheel motor for deceleration and braking. The redundant controller monitors the current maximum regenerative braking capability of the drive motor in real time, which is determined based on the state of charge of the power battery and the ambient temperature. After obtaining the current state of charge of the power battery and the ambient temperature, the redundant controller uses these two values ​​as indices to look up the corresponding current maximum regenerative braking capability in a mapping table. The lookup table method has a fast response speed and is suitable for embedded controllers with limited computing power.

[0066] The current maximum recovery capacity of the drive motor can be determined by looking up a pre-stored maximum recovery capacity mapping table based on the state of charge of the power battery and the ambient temperature. This mapping table contains the maximum recovery capacity values ​​corresponding to different combinations of power battery state of charge and ambient temperature.

[0067] The redundant controller can also send a query request to the power battery management system via the communication bus. The power battery management system calculates the current maximum allowable charging power in real time based on the SOC-temperature-charging power limit curve stored in its internal storage and returns it to the redundant controller. The redundant controller then converts it into the current maximum recovery capacity of the drive motor.

[0068] When the second braking torque reaches the current maximum recovery capacity of the drive motor, and the second braking torque is still less than the total braking torque required for vehicle braking, the redundant controller controls the electronic parking brake to apply the first braking torque to the front wheels to compensate for the difference between the second braking torque and the total braking torque.

[0069] In other words, at the initial stage of braking, the redundant controller prioritizes the use of the rear wheel motors for energy recovery braking, making full use of the motors' energy recovery capabilities. When the motors' recovery capabilities are utilized to their maximum extent, and this capability is still insufficient to meet the total braking torque requirements, the redundant controller then activates the electronic parking brakes on the front wheels for supplementary braking, so that the total braking torque meets the deceleration requirements of the intelligent driving system.

[0070] Through the aforementioned sequential coordinated control of the motor first and then the EPB, the wear-free energy recovery braking can be used preferentially during redundant braking, reducing the frequency and intensity of EPB mechanical braking intervention, thereby reducing the risk of brake component wear and thermal fade, while improving energy recovery efficiency and extending the vehicle's driving range.

[0071] During the application of the first and second braking torques, the redundant controller also acquires the vehicle's wheel slip ratio and deceleration in real time, and dynamically adjusts the first and / or second braking torques (corresponding to) based on the wheel slip ratio and deceleration. Figure 2 Step S4) is used to prevent wheel lock-up or slippage, ensuring braking stability and safety.

[0072] Specifically, each wheel of the vehicle is equipped with a wheel speed sensor, which is communicatively connected to a redundant controller to collect wheel speed signals in real time and send these signals to the redundant controller. The redundant controller calculates the wheel speed of each wheel based on the received wheel speed signals, calculates the slip ratio of each wheel based on the difference between its wheel speed and the reference vehicle speed, and calculates the vehicle's deceleration based on the vehicle's rate of change of speed.

[0073] The redundant controller acquires the target slip ratio range and target deceleration value for the vehicle under the current operating conditions. The target slip ratio range is the optimal slip ratio range for anti-lock braking control, set to 15% to 20%. The redundant controller compares the real-time slip ratio of each wheel with the target slip ratio range and compares the real-time deceleration of the vehicle with the target deceleration value.

[0074] When the real-time slip ratio of a wheel exceeds the upper limit of the target slip ratio range, it is determined that the wheel is prone to lock-up. The redundant controller reduces the braking torque applied to the axle containing that wheel. If the wheel is a front wheel, the redundant controller sends a reduction command to the electronic parking brake to reduce the first braking torque; if the wheel is a rear wheel, the redundant controller sends a reduction command to the drive motor to reduce the second braking torque, until the real-time slip ratio of that wheel falls back into the target slip ratio range. When the real-time slip ratio of a wheel exceeds the upper limit of the target slip ratio range, it is determined that the wheel is prone to lock-up. The redundant controller sends reduction commands to the electronic parking brake or drive motor according to the axle containing that wheel to reduce the braking torque of the corresponding axle, until the slip ratio falls back into the optimal slip ratio range. This prevents wheel lock-up from causing vehicle skidding or loss of control, ensuring that all wheels always operate in a high adhesion utilization state during redundant braking, improving braking stability and safety.

[0075] When the real-time slip ratio of a wheel is less than the lower limit of the target slip ratio range, the braking force of that wheel is determined to be insufficient. The redundant controller increases the braking torque applied to the axle of that wheel. If the wheel is a front wheel, the redundant controller sends an increase command to the electronic parking brake to increase the first braking torque; if the wheel is a rear wheel, the redundant controller sends an increase command to the drive motor to increase the second braking torque, until the real-time slip ratio of that wheel rises to within the target slip ratio range. When the real-time slip ratio of a wheel is lower than the lower limit of the target slip ratio range, the braking force of that wheel is determined to be insufficient. The redundant controller sends an increase command to the electronic parking brake or drive motor according to the axle of that wheel, until the slip ratio returns to the optimal slip ratio range. This ensures that all wheels always operate in a high adhesion utilization state, maximizing road adhesion utilization while preventing wheel lock-up or slippage, and improving the stability and braking efficiency of redundant braking.

[0076] When the vehicle's real-time deceleration is less than the target deceleration value, the redundant controller, while ensuring that the slip ratio of each wheel does not exceed the target slip ratio range, simultaneously increases the first and second braking torques until the real-time deceleration reaches the target deceleration value. When the vehicle's real-time deceleration is greater than the target deceleration value, the redundant controller simultaneously decreases the first and second braking torques until the real-time deceleration equals the target deceleration value. When the actual deceleration deviates from the target value, the redundant controller, with the slip ratio of each wheel not exceeding the optimal slip ratio range (15%~20%) as the constraint boundary, simultaneously adjusts the front wheel EPB mechanical braking torque and the rear wheel motor regenerative braking torque, so that the actual deceleration quickly converges to the target value. Thus, while ensuring braking stability without wheel lock-up or slippage, it achieves precise deceleration tracking, balancing braking safety and comfort.

[0077] In one implementation of this application, when the total braking torque decreases and the second braking torque is less than or equal to the reduced total braking torque, the redundant controller prioritizes releasing the first braking torque. This step aims to prioritize the recovery of motor energy to improve driving economy: when the deceleration demand decreases, the redundant controller prioritizes releasing the mechanical braking torque of the front wheel EPB, while retaining the regenerative braking torque of the rear wheel motor, thereby maximizing the conversion of braking energy into electrical energy to recharge the power battery, reducing energy loss and wear of braking components caused by mechanical friction.

[0078] The above comparison and adjustment steps are executed cyclically in a preset control cycle until the vehicle comes to a complete stop or the redundant braking request is released.

[0079] In one implementation of this application, when the vehicle needs to remain stationary, the redundant controller controls the electronic parking brake (EPB) to remain clamped; when the vehicle needs to start, the redundant controller acquires the vehicle's driving force, and when the driving force exceeds a preset driving force threshold, it controls the EPB to release. This step achieves parking hold and smooth start control when the redundant brake is disengaged: when parking, the EPB keeps the vehicle clamped to prevent rolling; when starting, the EPB is automatically released only after the driving force reaches the preset threshold, which avoids rolling due to premature release and jerking due to late release, thereby ensuring the safety and smoothness of starting on a slope.

[0080] Through the above methods, this application achieves reasonable distribution and dynamic adjustment of braking torque during redundant braking, taking into account energy recovery efficiency, braking deceleration requirements, and braking stability.

[0081] It should be noted that the technical solution of this application is particularly applicable to unmanned logistics vehicles. Unmanned logistics vehicles are typically unattended during operation. If the main braking system fails, manual intervention or emergency operation by the driver is impossible, placing higher demands on the autonomy, reliability, and braking deceleration limit of the redundant braking system. This application, through a collaborative redundant braking architecture of a front-mounted EPB and a rear-mounted regenerative braking system, can autonomously take over braking control when the main braking system fails, without manual intervention. Furthermore, the front-wheel EPB utilizes the axle load transfer effect to provide higher braking deceleration, fully meeting the safe deceleration and stopping requirements of unmanned logistics vehicles under conditions such as full load, high speed, and slopes. Simultaneously, unmanned logistics vehicles are typically purely electric-driven, possessing complete drive motors and power battery systems. This application reuses the vehicle's existing drive motor and domain controller as redundant braking resources, eliminating the need for additional dedicated redundant braking hardware, which highly aligns with the cost-sensitive and compact chassis space requirements of unmanned logistics vehicles. Furthermore, the control logic of this application, which automatically keeps the EPB clamped after parking and automatically releases the EPB when starting, is fully compatible with the unmanned and autonomous operation mode of unmanned logistics vehicles. It eliminates the need for manual operation of the parking brake, further improving the operational efficiency and safety of unmanned logistics vehicles.

[0082] It should be understood that the application of this application is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims. Those skilled in the art can understand that implementing all or part of the processes of the above embodiments and making equivalent changes according to the claims of this application still fall within the scope of this application.

Claims

1. A redundant braking control method for an electric vehicle, characterized in that, include: When a failure of the main braking system is detected, in response to the deceleration signal from the upper controller, the electronic parking brake is controlled to apply a first braking torque to the front wheels of the vehicle, and the drive motor is controlled to apply a second braking torque to the rear wheels of the vehicle. Obtain the wheel slip ratio and deceleration of the vehicle; Adjust the first braking torque and / or the second braking torque according to the wheel slip ratio and the deceleration; Wherein, the sum of the first braking torque and the second braking torque is equal to the total braking torque required for the vehicle to brake.

2. The redundant braking control method according to claim 1, characterized in that, The method is executed by an existing domain controller or independent controller on the vehicle. The domain controller or independent controller is communicatively connected to the electronic parking brake and the drive motor, respectively. The control software of the electronic parking brake is integrated into the domain controller or independent controller.

3. The redundant braking control method according to claim 1, characterized in that, The steps of controlling the electronic parking brake to apply a first braking torque to the front wheels of the vehicle and controlling the drive motor to apply a second braking torque to the rear wheels of the vehicle include: The drive motor is preferentially controlled to apply the second braking torque to the rear wheel; When the second braking torque reaches the current maximum recovery capacity of the drive motor and the second braking torque is less than the total braking torque, the electronic parking brake device is controlled to apply the first braking torque to the front wheels to compensate for the difference between the second braking torque and the total braking torque. The current maximum recovery capacity of the drive motor is determined based on the state of charge of the power battery and the ambient temperature.

4. The redundant braking control method according to claim 1, characterized in that, The step of adjusting the first braking torque and / or the second braking torque based on the wheel slip ratio and the deceleration includes: When the deceleration is less than the target deceleration, on the premise of ensuring that the slip ratio of each wheel does not exceed the preset slip ratio threshold, the first braking torque and / or the second braking torque are increased until the deceleration reaches the target deceleration; When the deceleration is greater than the target deceleration, the first braking torque and / or the second braking torque are reduced until the deceleration is equal to the target deceleration.

5. The redundant braking control method according to claim 1, characterized in that, The method further includes: When the total braking torque decreases and the second braking torque is less than or equal to the reduced total braking torque, the first braking torque is released first.

6. The redundant braking control method according to claim 1, characterized in that, Before the steps of controlling the electronic parking brake to apply a first braking torque to the front wheels of the vehicle and controlling the drive motor to apply a second braking torque to the rear wheels of the vehicle, the method further includes: Obtain the state of charge of the vehicle's power battery and the vehicle speed; The distribution ratio of the first braking torque to the second braking torque is determined based on the state of charge of the power battery and the vehicle speed.

7. The redundant braking control method according to claim 1, characterized in that, The steps for obtaining the failure signal of the main braking system include: The status signals sent by the main braking system are received through the first CAN bus and the second CAN bus, respectively. When neither the first CAN bus nor the second CAN bus receives the status signal, or when both the first CAN bus and the second CAN bus receive the fault flag bit, the main braking system is determined to have failed.

8. The redundant braking control method according to claim 1, characterized in that, The method further includes: When the vehicle needs to be stationary, the electronic parking brake device is controlled to remain clamped. When the vehicle needs to start, the driving force of the vehicle is acquired, and when the driving force is greater than a preset driving force threshold, the electronic parking brake device is controlled to release.

9. A redundant braking control system for an electric vehicle, characterized in that, include: An electronic parking brake device, connected to the front wheels of the vehicle, is used to apply a first braking torque to the front wheels; A drive motor, connected to the rear wheel of the vehicle, is used to apply a second braking torque to the rear wheel; A redundant controller is communicatively connected to the electronic parking brake device and the drive motor, respectively, and is used to execute the redundant braking control method of the electric vehicle as described in any one of claims 1 to 8. The control software of the electronic parking brake device is integrated into the redundant controller, which is an existing domain controller or an independent controller on the vehicle.

10. A vehicle, characterized in that, Includes the redundant braking control system for electric vehicles as described in claim 9.

Images