Backup Redundancy Braking System and Braking Method to Meet the High-Level Intelligent Driving Needs of Autonomous Vehicles

Abstract

This invention discloses a backup redundant brake-by-wire system and braking method for advanced autonomous driving systems, belonging to the field of automotive chassis braking. It includes an independently configured main braking module and a backup redundant braking module, which are connected in parallel to the four wheel cylinders of the autonomous vehicle via main hydraulic lines and backup hydraulic lines, respectively. Both the main braking module and the backup redundant braking module communicate with the vehicle's ECU, and a real-time communication connection is established between them. By employing the aforementioned backup redundant brake-by-wire system and braking method for advanced autonomous driving systems, the accuracy of conventional braking is ensured while seamless emergency takeover is achieved in the event of main brake failure, significantly improving braking safety and system reliability in advanced autonomous driving scenarios.

Description

Technical Field

[0001] This invention relates to the field of automotive chassis braking technology, and in particular to a backup redundant drive-by-wire braking system and braking method that meets the requirements of advanced intelligent driving for unmanned vehicles. Background Technology

[0002] The rapid iteration and deep application of electrification and intelligent technologies in the automotive industry have driven the large-scale development of the unmanned logistics vehicle industry. Its application scenarios have gradually expanded from fixed, specific route operations within industrial plants to logistics and express delivery scenarios on urban public roads. On the one hand, the transportation demand in the express logistics industry continues to rise, and the market is placing higher demands on the efficiency and scale of logistics distribution. On the other hand, the continuous rise in labor costs in the logistics transportation sector has further spurred the market demand for large-scale applications of unmanned logistics vehicles, leading to a continuous expansion of the market demand for unmanned vehicles. However, once unmanned logistics vehicles enter public roads, they face more complex and variable traffic conditions, placing stringent standards on the safety performance of their braking systems, even requiring zero braking failure. Because unmanned logistics vehicles operate without on-site driver intervention, a braking system failure can easily lead to collisions with pedestrians and other vehicles on the road, potentially causing major traffic accidents, resulting in personal injury and property damage.

[0003] To meet the braking requirements of manned intelligent driving vehicles, brake-by-wire systems have emerged and rapidly gained popularity. These systems effectively satisfy the braking and control needs of manned intelligent driving vehicles due to their advantages of fast braking response and strong braking pressure output. However, for the comprehensive braking requirements of unmanned logistics vehicles—high braking pressure, rapid pressure build-up response, braking redundancy backup, and low cost—no mature solution has yet emerged in the market. Summary of the Invention

[0004] The purpose of this invention is to provide a backup redundant brake-by-wire system and braking method that meets the requirements of advanced intelligent driving for autonomous vehicles, thereby solving the aforementioned technical problems.

[0005] To achieve the above objectives, the present invention provides a backup redundant brake-by-wire system for advanced intelligent driving of unmanned vehicles, including a main braking module and a backup redundant braking module that are independently configured. The main braking module and the backup redundant braking module are connected in parallel to the four wheel cylinders of the unmanned vehicle via main hydraulic lines and backup hydraulic lines, respectively. Both the main braking module and the backup redundant braking module communicate with the vehicle's ECU, and a real-time communication connection is established between the main braking module and the backup redundant braking module. Under normal conditions, the main braking module performs braking pressure build-up, and the backup redundant braking module collects the working status signal of the main braking module in real time. When the main braking module fails, the backup redundant braking module can automatically trigger the backup braking program and independently take over the vehicle's braking control.

[0006] Preferably, the main braking module includes a power drive unit and an electronic control integrated unit. The power drive unit includes a three-phase asynchronous drive motor, a planetary gear reduction mechanism connected to the output end of the three-phase asynchronous drive motor, a ball screw connected to the output end of the planetary gear reduction mechanism, and a power cylinder piston connected to the output end of the ball screw. The oil port of the power cylinder is connected to the four-wheel cylinder of the unmanned vehicle via the main hydraulic pipeline. The main hydraulic pipeline includes two main high-pressure oil lines connected in parallel with the oil port of the power cylinder, and four main oil inlet oil lines connected in parallel with the two main high-pressure oil lines. The four main oil inlet oil lines are connected to the four wheel cylinders of the unmanned vehicle. Each of the two main high-pressure oil lines is equipped with a normally open pressure boosting valve, and each of the four main oil inlet oil lines is equipped with a normally open oil inlet valve. Both the normally open pressure boosting valve and the normally open oil inlet valve are connected to the electronic control integrated unit.

[0007] Preferably, the backup redundant braking module includes a hydraulic actuator and an electronic triggering unit, and the output end of the hydraulic actuator is connected to the four wheel cylinders of the unmanned vehicle via a backup hydraulic pipeline; The backup hydraulic lines include two backup high-pressure oil lines connected in parallel with the oil port of the hydraulic actuator, and four backup oil inlet lines connected in parallel with the two backup high-pressure oil lines respectively. The four backup oil inlet lines are connected to the four wheel cylinders of the unmanned vehicle. A main solenoid valve is installed on the two backup high-pressure oil lines. A branch solenoid valve is connected in parallel to the main solenoid valve. Both the main solenoid valve and the branch solenoid valve are connected to the electronic control trigger unit. The electronic control trigger unit communicates bidirectionally with the electronic control integration unit via the CAN bus, and both the electronic control trigger unit and the electronic control integration unit communicate with the vehicle ECU.

[0008] Preferably, in the advanced intelligent driving backup redundant drive-by-wire braking system of the unmanned vehicle, the main braking module is fixed to the vehicle body via a firewall mounting plate; the backup redundant braking module is fixed to the vehicle body via a fixed mounting bracket.

[0009] The braking method of the backup redundant brake-by-wire system for advanced autonomous driving systems includes the following steps: S1. System Standby and Status Initialization: The main braking module and the backup redundant braking module complete power-on self-test. The electronic control integration unit and the electronic control trigger unit establish a bidirectional communication connection through the CAN bus. At the same time, both of them complete a communication handshake with the vehicle ECU. The main braking module enters the standby state, the power drive unit remains depressurized, and the normally open pressure boosting valve and normally open oil inlet valve are in the power-off open state. The backup redundant braking module enters the monitoring standby state, the hydraulic actuator unit is depressurized, and the backup high-pressure solenoid valve and the unit solenoid valve are in the power-off closed state. The hydraulic pressure, screw displacement, motor torque and wheel cylinder pressure signals of the main braking module are collected in real time. S2. Conventional Braking Control: Based on the autonomous vehicle's driving conditions and intelligent driving decisions, the vehicle's ECU sends a target braking pressure command to the main braking module's electronic control integrated unit (ECU). The ECU, using a multi-closed-loop control strategy (hydraulic pressure loop, screw displacement loop, motor current loop), converts the target braking pressure into the target torque of the three-phase asynchronous drive motor and control signals for the normally open booster valve and normally open inlet valve. The output torque of the three-phase asynchronous drive motor is converted into linear motion of the power cylinder piston via a gear reduction mechanism and ball screw, building pressure in the power cylinder. The normally open booster valve and normally open inlet valve adjust their opening according to the control signals, and high-pressure hydraulic oil enters the four-wheel cylinders via the main high-pressure oil circuit and the main inlet oil circuit. The ECU feeds back the braking status signal to the vehicle's ECU in real time. S3. Real-time fault monitoring and failure determination: The electronic control triggering unit of the backup redundant braking module continuously receives the working status signal of the main braking module, and at the same time collects the pressure and speed data of the main hydraulic pipeline and wheel cylinder; when the electronic control triggering unit detects that the actual hydraulic pressure of the main braking module deviates from the target pressure by more than a preset threshold, the torque of the three-phase asynchronous drive motor is abnormal or the screw displacement is out of control, and the duration exceeds the preset time window, it determines that the main braking module has failed. S4. Backup Braking Program Trigger and Mode Switching: The electronic control trigger unit disconnects the communication connection with the main braking module's electronic control integrated unit, sends a backup braking trigger signal to the vehicle ECU, and simultaneously switches to autonomous control mode; the electronic control trigger unit drives the hydraulic actuator to start, the backup high-pressure solenoid valve is energized and opened, and a backup high-pressure oil circuit is established; S5. Braking and Parking Control: When the speed of the unmanned vehicle drops to a preset safety threshold, the electronic control trigger unit controls the backup high-pressure solenoid valve and the unit solenoid valve to maintain the current opening, maintain the wheel cylinder braking pressure, and prevent the vehicle from rolling away; if the unmanned vehicle comes to a complete stop, the electronic control trigger unit maintains the braking pressure until the vehicle ECU issues a parking command. S6. Brake pressure relief and system reset: After the braking task is completed or the vehicle ECU issues a pressure relief command, the electronic control trigger unit controls the backup high-pressure solenoid valve and the unit solenoid valve to switch to the pressure relief state. The high-pressure hydraulic oil in the wheel cylinder flows back to the hydraulic oil reservoir through the pressure relief branch, and the wheel cylinder pressure gradually decreases to zero. The power cylinder piston resets under the action of the return spring, and the backup redundant braking module returns to the standby state. S7. Status Feedback and System Recovery: The electronic control trigger unit feeds back the execution result of the backup braking and the system status to the vehicle ECU; if the fault of the main braking module has been eliminated, the electronic control integration unit and the electronic control trigger unit re-establish communication connection, the main braking module returns to standby state, the backup redundant braking module exits the autonomous control mode, returns to the monitoring standby state, and the system recovers to the normal braking control mode.

[0010] Preferably, step S2 specifically includes the following steps: S21, Target pressure reception and scenario-based correction; Command reception: The vehicle ECU sends the target pressure command for the power cylinder to the electronic control integrated unit of the main braking module according to the driving conditions of the unmanned vehicle. ; Determine the scenario-based correction factor : ; S22, Hydraulic pressure loop based on feedforward and PI feedback combined with scenario-based correction factors. The target displacement of the lead screw output by the hydraulic pressure ring is obtained. : ; in, ; ; In the formula, This indicates the displacement of the feedforward control lead screw; This indicates that the PI feedback control controls the displacement of the lead screw; and These represent the proportional and integral coefficients of the PI control, respectively. This indicates the actual hydraulic pressure of the power cylinder; , and This represents the coefficients of the quadratic term, the coefficients of the linear term, and the constant term of the quadratic polynomial representing the pressure-displacement characteristics of a hydraulic system. S23. Based on robust sliding mode control lead screw displacement loop; S231. Establish a nonlinear system model for the horizontal motion of the leadscrew: ; ; in, ; ; ; In the formula, Indicates the speed of the leadscrew movement; This indicates a variable used to refer to the speed of the leadscrew movement; This term represents the acceleration term generated by the initial pressure, static friction, and return spring force. This term represents the acceleration caused by changes in hydraulic pressure and dynamic friction. Indicates the control gain term; The displacement of the leadscrew is At that time, the initial hydraulic pressure of the power cylinder; Indicates the cross-sectional area of ​​the piston in the power cylinder; Indicates control input, , This represents the target torque of the three-phase asynchronous drive motor; Indicates the amount of disturbance; The displacement of the leadscrew is Speed ​​is Static friction at time; This indicates the stiffness of the return spring in the power cylinder; This represents the state variable of the leadscrew displacement; Indicates the mass of the equivalent power cylinder; The displacement of the leadscrew is Speed ​​is The change in hydraulic pressure of the power cylinder at that time; The displacement of the leadscrew is Speed ​​is The change in kinetic friction force over time; This indicates the transmission ratio of the planetary gear reduction mechanism; Indicates the lead of the ball screw; express The derivative; S232, Design as a sliding mold surface : ; in, ; ; In the formula, This indicates the rate of change of the lead screw tracking error; This indicates the lead screw displacement tracking error; Indicates the sliding surface coefficient; Indicates the target speed of the leadscrew; S233. Based on the backstepping method, design the control law to obtain the target torque of the three-phase asynchronous drive motor. : ; In the formula, Indicates the torque coefficient; Indicates the equivalent mass of the lead screw; Indicates the target acceleration of the leadscrew; Indicates the damping coefficient of the leadscrew; The frictional force representing the pressure build-up in the power cylinder is adaptively estimated using an RBF neural network; Indicates the synovial term; S24, Motor current loop control; S241, Target torque Convert to d-axis target current and q-axis target current : ; ; In the formula, Indicates the number of pole pairs of the motor; Indicates permanent magnet flux linkage; S242. By employing feedforward decoupling to eliminate the coupling between the d-axis current and the q-axis current, the voltage command is obtained. ; In the formula, and These represent voltage commands for the d-axis and q-axis, respectively. This represents the stator resistance of a three-phase asynchronous drive motor; and These represent the actual currents along the d-axis and q-axis, respectively. and These represent the inductance along the d-axis and q-axis, respectively. This represents the electrical angular velocity of a three-phase asynchronous drive motor. S243, Transfer voltage commands for the d-axis and q-axis. , The command is converted into a three-phase voltage command, which is then used to generate a drive signal through space vector pulse width modulation to control the inverter output. S25, actual torque output of the three-phase asynchronous drive motor The force is converted into a screw servo force through a planetary gear reduction mechanism and a ball screw. : ; S26. The lead screw drives the piston to move, compressing the hydraulic oil in the power cylinder and generating actual hydraulic pressure. : ; In the formula, This indicates the actual displacement of the leadscrew; S27, the normally open pressure boosting valve and oil inlet valve adjust their opening degree according to the control signal of the electronic control integrated unit. High-pressure hydraulic oil enters the four wheel cylinders through the main high-pressure oil circuit and the main oil inlet oil circuit, thus increasing the pressure in the wheel cylinders. The following conditions must be met: ; In the formula, Indicates the effective area of ​​the cylinder piston; S28. The electronic control integrated unit updates steps S22-S24 based on the collected power cylinder pressure, wheel cylinder pressure, actual screw displacement, and the actual torque, actual current, and mechanical angular velocity of the three-phase asynchronous drive motor, until the actual hydraulic pressure is reached. Tracking target pressure It also feeds back the braking status signal to the vehicle ECU in real time.

[0011] Preferably, during the braking holding process described in step S5, the electronic control trigger unit collects data from the four wheel speed sensors in real time and calculates the slip ratio of each wheel. When the slip ratio of any wheel exceeds a preset threshold, a low-selection ABS control strategy is adopted. Taking the wheel with the least adhesion among the four wheels as the benchmark, the backup high-pressure solenoid valve and unit solenoid valve of the corresponding wheel cylinder group are adjusted: the solenoid valve is opened when pressurizing, closed when holding pressure, and the pressure relief branch is opened when depressurizing to prevent wheel lock-up and maintain braking stability.

[0012] Therefore, the present invention employs the above-mentioned backup redundant drive-by-wire braking system and braking method that meet the requirements of advanced intelligent driving for unmanned vehicles, and has the following beneficial effects: 1. Enhanced system redundancy and reliability: The main braking module and the backup redundant braking module adopt completely independent hydraulic, electronic control and mechanical architectures to achieve "main and backup decoupling", avoid the main system failure from affecting the backup system, completely eliminate the risk of single point failure, and ensure the high reliability of the unmanned vehicle braking system. 2. Accuracy and adaptability of conventional braking: The main braking module adopts a multi-closed-loop composite control strategy of "hydraulic pressure loop - screw displacement loop - motor current loop", combined with scenario-based correction factors to dynamically adjust the feedforward / feedback weights, which can accurately adapt to various working conditions such as AEB emergency braking, ACC following, and conventional deceleration, while ensuring the pressure build-up speed and achieving accurate pressure following. 3. Emergency braking safety and stability assurance: The backup redundant braking module has real-time monitoring and automatic triggering capabilities. When the main brake fails, it can seamlessly switch to autonomous control mode, independently calculate the emergency target braking pressure, and adjust the wheel cylinder pressure based on the minimum road surface adhesion coefficient through low-select ABS anti-lock braking control logic, effectively avoiding wheel lock-up and vehicle sideslip, and ensuring the stability and safety of the emergency braking process. 4. Optimization of engineering cost and installation complexity: The backup hydraulic pipeline adopts an X-shaped diagonal braking topology of "two backup high-pressure oil circuits + dual-unit solenoid valves". It replaces the four-wheel independent control with two sets of wheel cylinder groups. While ensuring functional integrity, it simplifies the number of solenoid valves and pipeline layout, reduces system cost and chassis installation complexity, and is more suitable for the commercialization of unmanned vehicles. 5. Robustness and disturbance rejection capability of the control algorithm: The lead screw displacement loop adopts robust sliding mode control based on backstepping method, combined with RBF neural network to adaptively estimate friction disturbance, effectively suppressing the influence of hydraulic time-varying, model error and external load disturbance on control accuracy, and improving the robustness of the system under complex working conditions.

[0013] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the backup redundant drive-by-wire braking system for advanced intelligent driving of unmanned vehicles as described in this invention. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of the embodiments of the present invention and are not intended to limit the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of this application. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout.

[0016] It should be noted that the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion, such as a process, method, system, product, or server that includes a series of steps or units, not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such process, method, product, or device.

[0017] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0018] like Figure 1 As shown, the backup redundant brake-by-wire system of the advanced intelligent driving system for autonomous vehicles includes an independently configured main braking module and a backup redundant braking module. The main braking module and the backup redundant braking module are connected in parallel to the four wheel cylinders of the autonomous vehicle via main hydraulic lines and backup hydraulic lines, respectively. Both the main braking module and the backup redundant braking module communicate with the vehicle's ECU, and a real-time communication connection is established between the main braking module and the backup redundant braking module. Under normal conditions, the main braking module performs braking pressure build-up, and the backup redundant braking module collects the working status signal of the main braking module in real time. When the main braking module fails, the backup redundant braking module can automatically trigger the backup braking program and independently take over the vehicle's braking control.

[0019] The main braking module includes a power drive unit and an electronic control integration unit. The power drive unit includes a three-phase asynchronous drive motor, a planetary gear reduction mechanism connected to the output end of the three-phase asynchronous drive motor, a ball screw connected to the output end of the planetary gear reduction mechanism, and a power cylinder piston connected to the output end of the ball screw. The oil port of the power cylinder is connected to the four wheel cylinders of the unmanned vehicle through the main hydraulic pipeline. The main hydraulic pipeline includes two main high-pressure oil lines connected in parallel with the oil port of the power cylinder, and four main oil inlet lines connected in parallel with the two main high-pressure oil lines. The four main oil inlet lines are connected to the four wheel cylinders of the unmanned vehicle. Each of the two main high-pressure oil lines is equipped with a normally open booster valve (PSV1, PSV2), and each of the four main oil inlet lines is equipped with a normally open inlet valve (IV). Both the normally open booster valve and the normally open inlet valve are connected to the electronic control integrated unit.

[0020] The backup redundant braking module includes a hydraulic actuator and an electronic triggering unit. The output of the hydraulic actuator is connected to the four wheel cylinders of the unmanned vehicle via a backup hydraulic pipeline. The backup hydraulic lines include two backup high-pressure oil lines connected in parallel with the oil ports of the hydraulic actuator, and four backup oil inlet lines connected in parallel with the two backup high-pressure oil lines. The four backup oil inlet lines are connected to the four wheel cylinders of the unmanned vehicle. The two backup high-pressure oil lines are equipped with main solenoid valves (HSV1, HSV2), and branch solenoid valves (USV1, USV2) are connected in parallel to the main solenoid valves. Both the main solenoid valves and the branch solenoid valves are connected to the electronic control trigger unit. The electronic control trigger unit communicates bidirectionally with the electronic control integration unit via the CAN bus, and both the electronic control trigger unit and the electronic control integration unit communicate with the vehicle ECU.

[0021] The backup redundant brake-by-wire system of the advanced intelligent driving system of the autonomous vehicle has the main braking module fixed to the vehicle body via a firewall mounting plate; the backup redundant braking module is fixed to the vehicle body via a fixed mounting bracket.

[0022] The braking method of the backup redundant brake-by-wire system for advanced autonomous driving systems includes the following steps: S1. System Standby and Status Initialization: The main braking module and the backup redundant braking module complete power-on self-test. The electronic control integration unit and the electronic control trigger unit establish a bidirectional communication connection through the CAN bus. At the same time, both of them complete a communication handshake with the vehicle ECU. The main braking module enters the standby state, the power drive unit remains depressurized, and the normally open pressure boosting valve and normally open oil inlet valve are in the power-off open state. The backup redundant braking module enters the monitoring standby state, the hydraulic actuator unit is depressurized, and the backup high-pressure solenoid valve and the unit solenoid valve are in the power-off closed state. The hydraulic pressure, screw displacement, motor torque and wheel cylinder pressure signals of the main braking module are collected in real time. S2. Conventional Braking Control: Based on the autonomous vehicle's driving conditions and intelligent driving decisions, the vehicle's ECU sends a target braking pressure command to the main braking module's electronic control integrated unit (ECU). The ECU, using a multi-closed-loop control strategy (hydraulic pressure loop, screw displacement loop, motor current loop), converts the target braking pressure into the target torque of the three-phase asynchronous drive motor and control signals for the normally open booster valve and normally open inlet valve. The output torque of the three-phase asynchronous drive motor is converted into linear motion of the power cylinder piston via a gear reduction mechanism and ball screw, building pressure in the power cylinder. The normally open booster valve and normally open inlet valve adjust their opening according to the control signals, and high-pressure hydraulic oil enters the four-wheel cylinders via the main high-pressure oil circuit and the main inlet oil circuit. The ECU feeds back the braking status signal to the vehicle's ECU in real time. S3. Real-time fault monitoring and failure determination: The electronic control triggering unit of the backup redundant braking module continuously receives the working status signal of the main braking module, and at the same time collects the pressure and speed data of the main hydraulic pipeline and wheel cylinder; when the electronic control triggering unit detects that the actual hydraulic pressure of the main braking module deviates from the target pressure by more than a preset threshold, the torque of the three-phase asynchronous drive motor is abnormal or the screw displacement is out of control, and the duration exceeds the preset time window, it determines that the main braking module has failed. S4. Backup Braking Program Trigger and Mode Switching: The electronic control trigger unit disconnects the communication connection with the main braking module's electronic control integrated unit, sends a backup braking trigger signal to the vehicle ECU, and simultaneously switches to autonomous control mode; the electronic control trigger unit drives the hydraulic actuator to start, the backup high-pressure solenoid valve is energized and opened, and a backup high-pressure oil circuit is established; S5. Braking and Parking Control: When the speed of the unmanned vehicle drops to a preset safety threshold, the electronic control trigger unit controls the backup high-pressure solenoid valve and the unit solenoid valve to maintain the current opening, maintain the wheel cylinder braking pressure, and prevent the vehicle from rolling away; if the unmanned vehicle comes to a complete stop, the electronic control trigger unit maintains the braking pressure until the vehicle ECU issues a parking command. S6. Brake pressure relief and system reset: After the braking task is completed or the vehicle ECU issues a pressure relief command, the electronic control trigger unit controls the backup high-pressure solenoid valve and the unit solenoid valve to switch to the pressure relief state. The high-pressure hydraulic oil in the wheel cylinder flows back to the hydraulic oil reservoir through the pressure relief branch, and the wheel cylinder pressure gradually decreases to zero. The power cylinder piston resets under the action of the return spring, and the backup redundant braking module returns to the standby state. S7. Status Feedback and System Recovery: The electronic control trigger unit feeds back the execution result of the backup braking and the system status to the vehicle ECU; if the fault of the main braking module has been eliminated, the electronic control integration unit and the electronic control trigger unit re-establish communication connection, the main braking module returns to standby state, the backup redundant braking module exits the autonomous control mode, returns to the monitoring standby state, and the system recovers to the normal braking control mode.

[0023] Step S2 specifically includes the following steps: S21, Target pressure reception and scenario-based correction; Command reception: The vehicle ECU sends the target pressure command for the power cylinder to the electronic control integrated unit of the main braking module according to the driving conditions of the unmanned vehicle. ; Determine the scenario-based correction factor : ; S22, Hydraulic pressure loop based on feedforward and PI feedback combined with scenario-based correction factors. The target displacement of the lead screw output by the hydraulic pressure ring is obtained. : ; in, ; ; In the formula, This indicates the displacement of the feedforward control lead screw; This indicates that the PI feedback control controls the displacement of the lead screw; and These represent the proportional and integral coefficients of the PI control, respectively. This indicates the actual hydraulic pressure of the power cylinder; , and This represents the coefficients of the quadratic term, the coefficients of the linear term, and the constant term of the quadratic polynomial representing the pressure-displacement characteristics of a hydraulic system. S23. Based on robust sliding mode control lead screw displacement loop; S231. Establish a nonlinear system model for the horizontal motion of the leadscrew: ; ; in, ; ; ; In the formula, Indicates the speed of the leadscrew movement; This indicates a variable used to refer to the speed of the leadscrew movement; This term represents the acceleration term generated by the initial pressure, static friction, and return spring force. This term represents the acceleration caused by changes in hydraulic pressure and dynamic friction. Indicates the control gain term; The displacement of the leadscrew is At that time, the initial hydraulic pressure of the power cylinder; Indicates the cross-sectional area of ​​the piston in the power cylinder; Indicates control input, , This represents the target torque of the three-phase asynchronous drive motor; Indicates the amount of disturbance; The displacement of the leadscrew is Speed ​​is Static friction at time; This indicates the stiffness of the return spring in the power cylinder; This represents the state variable of the leadscrew displacement; Indicates the mass of the equivalent power cylinder; The displacement of the leadscrew is Speed ​​is The change in hydraulic pressure of the power cylinder at that time; The displacement of the leadscrew is Speed ​​is The change in kinetic friction force over time; This indicates the transmission ratio of the planetary gear reduction mechanism; Indicates the lead of the ball screw; express The derivative; S232, Design as a sliding mold surface : ; in, ; ; In the formula, This indicates the rate of change of the lead screw tracking error; This indicates the lead screw displacement tracking error; Indicates the sliding surface coefficient; Indicates the target speed of the leadscrew; S233. Based on the backstepping method, design the control law to obtain the target torque of the three-phase asynchronous drive motor. : ; In the formula, Indicates the torque coefficient; Indicates the equivalent mass of the lead screw; Indicates the target acceleration of the leadscrew; Indicates the damping coefficient of the leadscrew; The frictional force representing the pressure build-up in the power cylinder is adaptively estimated using an RBF neural network; Indicates the synovial term; S24, Motor current loop control; S241, Target torque Convert to d-axis target current and q-axis target current : ; ; In the formula, Indicates the number of pole pairs of the motor; Indicates permanent magnet flux linkage; S242. By employing feedforward decoupling to eliminate the coupling between the d-axis current and the q-axis current, the voltage command is obtained. ; In the formula, and These represent voltage commands for the d-axis and q-axis, respectively. This represents the stator resistance of a three-phase asynchronous drive motor; and These represent the actual currents along the d-axis and q-axis, respectively. and These represent the inductance along the d-axis and q-axis, respectively. This represents the electrical angular velocity of a three-phase asynchronous drive motor. S243, Transfer voltage commands for the d-axis and q-axis. , The command is converted into a three-phase voltage command, which is then used to generate a drive signal through space vector pulse width modulation to control the inverter output. S25, actual torque output of the three-phase asynchronous drive motor The force is converted into a screw servo force through a planetary gear reduction mechanism and a ball screw. : ; S26. The lead screw drives the piston to move, compressing the hydraulic oil in the power cylinder and generating actual hydraulic pressure. : ; In the formula, This indicates the actual displacement of the leadscrew; S27, the normally open pressure boosting valve and oil inlet valve adjust their opening degree according to the control signal of the electronic control integrated unit. High-pressure hydraulic oil enters the four wheel cylinders through the main high-pressure oil circuit and the main oil inlet oil circuit, thus increasing the pressure in the wheel cylinders. The following conditions must be met: ; In the formula, Indicates the effective area of ​​the cylinder piston; S28. The electronic control integrated unit updates steps S22-S24 based on the collected power cylinder pressure, wheel cylinder pressure, actual screw displacement, and the actual torque, actual current, and mechanical angular velocity of the three-phase asynchronous drive motor, until the actual hydraulic pressure is reached. Tracking target pressure It also feeds back the braking status signal to the vehicle ECU in real time.

[0024] During the braking holding process described in step S5, the electronic control trigger unit collects data from the four wheel speed sensors in real time and calculates the slip ratio of each wheel. When the slip ratio of any wheel exceeds a preset threshold, a low-selection ABS control strategy is adopted. Taking the wheel with the least adhesion among the four wheels as the benchmark, the backup high-pressure solenoid valve and unit solenoid valve of the corresponding wheel cylinder group are adjusted: the solenoid valve is opened when pressurizing, closed when holding pressure, and the pressure relief branch is opened when depressurizing to prevent wheel lock-up and maintain braking stability.

[0025] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A backup redundant drive-by-wire braking system for advanced intelligent driving in unmanned vehicles, characterized by: It includes a main braking module and a backup redundant braking module that are set up independently. The main braking module and the backup redundant braking module are connected in parallel to the four wheel cylinders of the unmanned vehicle through the main hydraulic pipeline and the backup hydraulic pipeline, respectively. Both the main braking module and the backup redundant braking module communicate with the vehicle's ECU, and a real-time communication connection is established between the main braking module and the backup redundant braking module. Under normal conditions, the main braking module performs braking pressure build-up, and the backup redundant braking module collects the working status signal of the main braking module in real time. When the main braking module fails, the backup redundant braking module can automatically trigger the backup braking program and independently take over the vehicle's braking control.

2. The backup redundant drive-by-wire braking system for advanced intelligent driving of unmanned vehicles according to claim 1, characterized in that: The main braking module includes a power drive unit and an electronic control integration unit. The power drive unit includes a three-phase asynchronous drive motor, a planetary gear reduction mechanism connected to the output end of the three-phase asynchronous drive motor, a ball screw connected to the output end of the planetary gear reduction mechanism, and a power cylinder piston connected to the output end of the ball screw. The oil port of the power cylinder is connected to the four wheel cylinders of the unmanned vehicle through the main hydraulic pipeline. The main hydraulic pipeline includes two main high-pressure oil lines connected in parallel with the oil port of the power cylinder, and four main oil inlet oil lines connected in parallel with the two main high-pressure oil lines. The four main oil inlet oil lines are connected to the four wheel cylinders of the unmanned vehicle. Each of the two main high-pressure oil lines is equipped with a normally open pressure boosting valve, and each of the four main oil inlet oil lines is equipped with a normally open oil inlet valve. Both the normally open pressure boosting valve and the normally open oil inlet valve are connected to the electronic control integrated unit.

3. The backup redundant drive-by-wire braking system for advanced intelligent driving of unmanned vehicles according to claim 2, characterized in that: The backup redundant braking module includes a hydraulic actuator and an electronic triggering unit. The output of the hydraulic actuator is connected to the four wheel cylinders of the unmanned vehicle via a backup hydraulic pipeline. The backup hydraulic lines include two backup high-pressure oil lines connected in parallel with the oil port of the hydraulic actuator, and four backup oil inlet lines connected in parallel with the two backup high-pressure oil lines respectively. The four backup oil inlet lines are connected to the four wheel cylinders of the unmanned vehicle. A main solenoid valve is installed on the two backup high-pressure oil lines. A branch solenoid valve is connected in parallel to the main solenoid valve. Both the main solenoid valve and the branch solenoid valve are connected to the electronic control trigger unit. The electronic control trigger unit communicates bidirectionally with the electronic control integration unit via the CAN bus, and both the electronic control trigger unit and the electronic control integration unit communicate with the vehicle ECU.

4. The backup redundant drive-by-wire braking system for advanced intelligent driving of unmanned vehicles according to claim 3, characterized in that: The main braking module is fixed to the vehicle body via a firewall mounting plate; the backup redundant braking module is fixed to the vehicle body via a fixed mounting bracket.

5. The braking method of the backup redundant brake-by-wire system for advanced autonomous driving as described in claim 3 or 4, characterized in that: Includes the following steps: S1. System Standby and Status Initialization: The main braking module and the backup redundant braking module complete power-on self-test. The electronic control integration unit and the electronic control trigger unit establish a bidirectional communication connection through the CAN bus. At the same time, both of them complete a communication handshake with the vehicle ECU. The main braking module enters the standby state, the power drive unit remains depressurized, and the normally open pressure boosting valve and normally open oil inlet valve are in the power-off open state. The backup redundant braking module enters the monitoring standby state, the hydraulic actuator unit is depressurized, and the backup high-pressure solenoid valve and the unit solenoid valve are in the power-off closed state. The hydraulic pressure, screw displacement, motor torque and wheel cylinder pressure signals of the main braking module are collected in real time. S2. Conventional Braking Control: Based on the autonomous vehicle's driving conditions and intelligent driving decisions, the vehicle's ECU sends a target braking pressure command to the main braking module's electronic control integrated unit (ECU). The ECU, using a multi-closed-loop control strategy (hydraulic pressure loop, screw displacement loop, motor current loop), converts the target braking pressure into the target torque of the three-phase asynchronous drive motor and control signals for the normally open booster valve and normally open inlet valve. The output torque of the three-phase asynchronous drive motor is converted into linear motion of the power cylinder piston via a gear reduction mechanism and ball screw, building pressure in the power cylinder. The normally open booster valve and normally open inlet valve adjust their opening according to the control signals, and high-pressure hydraulic oil enters the four-wheel cylinders via the main high-pressure oil circuit and the main inlet oil circuit. The ECU feeds back the braking status signal to the vehicle's ECU in real time. S3. Real-time fault monitoring and failure determination: The electronic control triggering unit of the backup redundant braking module continuously receives the working status signal of the main braking module, and at the same time collects the pressure and speed data of the main hydraulic pipeline and wheel cylinder; when the electronic control triggering unit detects that the actual hydraulic pressure of the main braking module deviates from the target pressure by more than a preset threshold, the torque of the three-phase asynchronous drive motor is abnormal or the screw displacement is out of control, and the duration exceeds the preset time window, it determines that the main braking module has failed. S4. Backup Braking Program Trigger and Mode Switching: The electronic control trigger unit disconnects the communication connection with the main braking module's electronic control integrated unit, sends a backup braking trigger signal to the vehicle ECU, and simultaneously switches to autonomous control mode; the electronic control trigger unit drives the hydraulic actuator to start, the backup high-pressure solenoid valve is energized and opened, and a backup high-pressure oil circuit is established; S5. Braking and Parking Control: When the speed of the unmanned vehicle drops to a preset safety threshold, the electronic control trigger unit controls the backup high-pressure solenoid valve and the unit solenoid valve to maintain the current opening, maintain the wheel cylinder braking pressure, and prevent the vehicle from rolling away; if the unmanned vehicle comes to a complete stop, the electronic control trigger unit maintains the braking pressure until the vehicle ECU issues a parking command. S6. Brake pressure relief and system reset: After the braking task is completed or the vehicle ECU issues a pressure relief command, the electronic control trigger unit controls the backup high-pressure solenoid valve and the unit solenoid valve to switch to the pressure relief state. The high-pressure hydraulic oil in the wheel cylinder flows back to the hydraulic oil reservoir through the pressure relief branch, and the wheel cylinder pressure gradually decreases to zero. The power cylinder piston resets under the action of the return spring, and the backup redundant braking module returns to the standby state. S7. Status Feedback and System Recovery: The electronic control trigger unit feeds back the execution result of the backup braking and the system status to the vehicle ECU; if the fault of the main braking module has been eliminated, the electronic control integration unit and the electronic control trigger unit re-establish communication connection, the main braking module returns to standby state, the backup redundant braking module exits the autonomous control mode, returns to the monitoring standby state, and the system recovers to the normal braking control mode.

6. The braking method of the backup redundant brake-by-wire system for advanced autonomous driving of unmanned vehicles according to claim 5, characterized in that: Step S2 specifically includes the following steps: S21, Target pressure reception and scenario-based correction; Command reception: The vehicle ECU sends the target pressure command for the power cylinder to the electronic control integrated unit of the main braking module according to the driving conditions of the unmanned vehicle. ; Determine the scenario-based correction factor : ； S22, Hydraulic pressure loop based on feedforward and PI feedback combined with scenario-based correction factors. The target displacement of the lead screw output by the hydraulic pressure ring is obtained. : ； in, ； ； In the formula, Indicates the displacement of the feedforward control lead screw; This indicates that the PI feedback control controls the displacement of the lead screw; and These represent the proportional and integral coefficients of the PI control, respectively. This indicates the actual hydraulic pressure of the power cylinder; , and This represents the coefficients of the quadratic term, the coefficients of the linear term, and the constant term of the quadratic polynomial representing the pressure-displacement characteristics of a hydraulic system. S23. Based on robust sliding mode control lead screw displacement loop; S231. Establish a nonlinear system model for the horizontal motion of the leadscrew: ； ； in, ； ； ； In the formula, Indicates the speed of the leadscrew movement; This indicates a variable used to refer to the speed of the leadscrew movement; This term represents the acceleration term generated by the initial pressure, static friction, and return spring force. This term represents the acceleration caused by changes in hydraulic pressure and dynamic friction. Indicates the control gain term; Indicates the displacement of the leadscrew as At that time, the initial hydraulic pressure of the power cylinder; Indicates the cross-sectional area of ​​the piston in the power cylinder; Indicates control input, , This represents the target torque of the three-phase asynchronous drive motor; Indicates the amount of disturbance; The displacement of the leadscrew is Speed ​​is Static friction at time; This indicates the stiffness of the return spring in the power cylinder; This represents the state variable of the leadscrew displacement; Indicates the mass of the equivalent power cylinder; Indicates the displacement of the leadscrew as Speed ​​is The change in hydraulic pressure of the power cylinder at that time; Indicates the displacement of the leadscrew as Speed ​​is The change in dynamic friction force over time; This indicates the transmission ratio of the planetary gear reduction mechanism; Indicates the lead of the ball screw; express The derivative; S232, Design as a sliding mold surface : ； in, ； ； In the formula, This indicates the rate of change of the lead screw tracking error; This indicates the lead screw displacement tracking error; Indicates the sliding surface coefficient; Indicates the target speed of the leadscrew; S233. Based on the backstepping method, design the control law to obtain the target torque of the three-phase asynchronous drive motor. : ； In the formula, Indicates the torque coefficient; Indicates the equivalent mass of the lead screw; Indicates the target acceleration of the leadscrew; Indicates the damping coefficient of the leadscrew; The frictional force representing the pressure build-up in the power cylinder is adaptively estimated using an RBF neural network; Indicates the synovial term; S24, Motor current loop control; S241, Target torque Convert to d-axis target current and q-axis target current : ； ； In the formula, Indicates the number of pole pairs of the motor; Indicates permanent magnet flux linkage; S242. By employing feedforward decoupling to eliminate the coupling between the d-axis current and the q-axis current, the voltage command is obtained: ； In the formula, and These represent voltage commands for the d-axis and q-axis, respectively. This represents the stator resistance of a three-phase asynchronous drive motor; and These represent the actual currents along the d-axis and q-axis, respectively. and These represent the inductance along the d-axis and q-axis, respectively. This represents the electrical angular velocity of a three-phase asynchronous drive motor. S243, Transfer voltage commands for the d-axis and q-axis. , The command is converted into a three-phase voltage command, which is then used to generate a drive signal through space vector pulse width modulation to control the inverter output. S25, actual torque output of the three-phase asynchronous drive motor The force is converted into a screw servo force through a planetary gear reduction mechanism and a ball screw. : ； S26. The lead screw drives the piston to move, compressing the hydraulic oil in the power cylinder and generating actual hydraulic pressure. : ； In the formula, This indicates the actual displacement of the leadscrew; S27, the normally open pressure boosting valve and oil inlet valve adjust their opening degree according to the control signal of the electronic control integrated unit. High-pressure hydraulic oil enters the four wheel cylinders through the main high-pressure oil circuit and the main oil inlet oil circuit, thus increasing the pressure in the wheel cylinders. The following conditions must be met: ； In the formula, Indicates the effective area of ​​the cylinder piston; S28. The electronic control integrated unit updates steps S22-S24 based on the collected power cylinder pressure, wheel cylinder pressure, actual screw displacement, and the actual torque, actual current, and mechanical angular velocity of the three-phase asynchronous drive motor, until the actual hydraulic pressure is reached. Tracking target pressure It also feeds back the braking status signal to the vehicle ECU in real time.

7. The braking method of the backup redundant brake-by-wire system for advanced autonomous driving of unmanned vehicles according to claim 5, characterized in that: During the braking holding process described in step S5, the electronic control trigger unit collects data from the four wheel speed sensors in real time and calculates the slip ratio of each wheel. When the slip ratio of any wheel exceeds a preset threshold, a low-selection ABS control strategy is adopted. Taking the wheel with the least adhesion among the four wheels as the benchmark, the backup high-pressure solenoid valve and unit solenoid valve of the corresponding wheel cylinder group are adjusted: the solenoid valve is opened when pressurizing, closed when holding pressure, and the pressure relief branch is opened when depressurizing to prevent wheel lock-up and maintain braking stability.

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