Steer-by-wire double-assist steering system with rear axle active steering and control method thereof

Abstract

The application discloses a steer-by-wire double-assist steering system with a rear axle active steering and a control method thereof, relates to the technical field of vehicle steering, and comprises a control assembly, a front axle steering system, a rear axle steering system, a vehicle controller and a mode selector. The front axle steering system and the rear axle steering system are symmetrically distributed and are connected with the vehicle controller with a coordination function. Multiple steering modes are designed to enable the vehicle to realize good steering in various road conditions. Multiple assist steering modes are designed to realize the optimal distribution of vehicle energy. The mechanical connection between the steering wheel and the steering execution mechanism and the mechanical connection between the front axle steering system and the rear axle steering system are cancelled, and the steer-by-wire connection is adopted, thereby saving space. Since there is no direct mechanical connection between the front axle and the rear axle, theoretically, multi-axle active steering can be realized. Multiple components of the application are provided with redundant components, so that when a component fails, the redundant component can replace the failed component, thereby ensuring driving safety.

Description

Technical Field

[0001] This invention relates to the field of vehicle steering technology, specifically to a steer-by-wire dual power steering system with active rear axle steering and its control method. Background Technology

[0002] Heavy-duty commercial vehicles commonly use hydraulic power steering systems (HPS), but traditional HPS can cause vehicles to feel unstable at high speeds, resulting in a lack of steering feel for the driver and an inability to provide speed-sensitive assistance. Furthermore, HPS suffers from significant energy loss. Electro-hydraulic power steering systems (EHS) no longer have their steering pump directly driven by the engine; instead, they are driven by an electric motor. An electronic control system is added to the EHS, reducing energy consumption and improving responsiveness. The steering assist can also be adjusted automatically based on parameters such as steering angle and vehicle speed. However, EHS still has drawbacks. Electric power steering (EPS) provides steering assistance directly from an electric motor, eliminating the need for the power steering pump, hoses, hydraulic fluid, transmission belt, and pulley mounted on the engine—all essential components of hydraulic power steering. This saves energy and protects the environment. However, due to current power system limitations, EPS is not yet suitable for heavy-duty commercial vehicles.

[0003] Rear-axle steering technology can significantly improve vehicle handling and stability, reduce the turning radius, and enhance vehicle safety under certain driving conditions. Currently, many automakers have developed various types of rear-axle steering systems, including electronic steering, mechanical steering, and hydraulic steering. However, traditional rear-axle steering systems generally suffer from several problems, such as complex structure, high cost, and difficulty in maintenance. Furthermore, under certain driving conditions, these systems are more prone to malfunction or failure, significantly impacting vehicle performance and compromising driver and passenger safety.

[0004] Therefore, a new rear-axle steering system and its control method are needed to address the shortcomings of traditional systems and provide a more efficient and reliable steering solution to improve vehicle performance and safety. Summary of the Invention

[0005] This invention addresses the problem of overly simplistic solutions in existing technologies by providing a significantly different approach. Specifically, the invention aims to provide a steer-by-wire dual-power steering system with rear-axle active steering and its control method. This solves the problems associated with traditional rear-axle steering systems mentioned in the background, such as complex structure, high cost, and difficulty in maintenance. Furthermore, these systems may malfunction or fail under certain driving conditions, affecting vehicle performance and safety.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a steer-by-wire dual-power steering system with rear axle active steering, comprising a control assembly, a front axle steering system, a rear axle steering system, and a vehicle controller, characterized in that: it further comprises a mode selector, wherein the front axle steering system and the rear axle steering system are symmetrically distributed and connected to the vehicle controller with coordination function, and both the front axle steering system and the rear axle steering system are connected to the vehicle controller via a CAN bus.

[0007] Preferably, the control assembly includes a steering wheel, a torque angle sensor, a road feel motor, and a motor reduction mechanism. The road feel motor simulates specific road feel and realizes steering return to center.

[0008] Preferably, the front axle steering system includes a first control unit, a second control unit, a first servo motor, a first electromagnetic clutch, a first worm gear reducer, a second servo motor, a second electromagnetic clutch, a first drive motor, a first oil pump clutch, a first hydraulic pump, a first recirculating ball steering assembly, a front axle steering linkage, and an oil tank. The second control unit is configured as a redundant component of the first control unit, which can quickly take over when the first control unit fails. The first servo motor is the main power steering motor for the front axle, and the second servo motor is an auxiliary backup motor. Both the first and second servo motors are electrically connected to the first and second control units, and the first control unit controls whether the first and second servo motors are engaged or not by controlling the on / off state of the first and second electromagnetic clutches.

[0009] Preferably, the first servo motor, the second servo motor, and the first drive motor are all equipped with speed sensors to monitor the speed, and the first hydraulic pump is equipped with a temperature and pressure sensor to monitor the temperature of the hydraulic oil and the pressure inside the pump. The front axle wheels are equipped with vehicle speed sensors to monitor the vehicle speed, and the first servo motor and the second servo motor are used to provide auxiliary power assistance.

[0010] Preferably, the rear axle steering system includes a third control unit, a fourth control unit, a third servo motor, a third electromagnetic clutch, a second worm gear reducer, a fourth servo motor, a fourth electromagnetic clutch, a second drive motor, a second oil pump clutch, a second hydraulic pump, a second recirculating ball steering assembly, a rear axle steering linkage, and an oil tank. The fourth control unit is a redundant component of the third control unit and can take over the operation of the third control unit when it fails. The third servo motor is the main power steering motor for the rear axle, and the fourth servo motor is an auxiliary backup motor. Both the third and fourth servo motors are electrically connected to the third and fourth control units. The third control unit controls whether the third and fourth servo motors are engaged or not by controlling the on / off state of the third and fourth electromagnetic clutches.

[0011] Preferably, the third servo motor, the fourth servo motor, and the second drive motor are all equipped with speed sensors to monitor the speed, and the second hydraulic pump is equipped with a temperature and pressure sensor to monitor the temperature and pressure of the hydraulic oil. A vehicle speed sensor is installed in the rear axle wheel to measure the vehicle speed, and a wheel angle sensor is installed on the wheel suspension system to monitor the steering accuracy.

[0012] This invention also provides a control method for the aforementioned steer-by-wire dual-power steering system with rear axle active steering. A mode selector is installed between the first control unit and the third control unit. The driver selects different steering modes according to the current road conditions. Control signals are transmitted to the first and third control units via the vehicle controller to control the front axle steering and the rear axle steering. The method specifically includes the following steps:

[0013] a. The vehicle controller outputs corresponding control signals to the front axle steering system control unit and the rear axle steering system control unit based on the signal from the mode selector;

[0014] b. The front axle steering system control unit outputs the optimal distribution of assist current to the corresponding actuator motor to control the front axle steering based on the torque angle signal and vehicle speed signal of the driver operating the steering wheel, according to a pre-written algorithm.

[0015] c. The rear axle steering system control unit outputs corresponding control current to control the rear axle steering based on the front axle steering angle and vehicle speed signals and the control signals transmitted by the vehicle controller.

[0016] Preferably, the control method for the above-mentioned steer-by-wire dual power steering system with rear axle active steering also includes fault control. For the front axle steering system, when the first servo motor fails, the first electromagnetic clutch disengages, the first servo motor stops assisting, the second electromagnetic clutch engages, and the second servo motor starts working. When the first drive motor fails, the first oil pump clutch disengages, stopping hydraulic assisting, the second electromagnetic clutch engages, and the second servo motor starts working. The first and second servo motors jointly provide assistance, and the vehicle enters pure electric power steering mode. When the first control unit fails, the second control unit takes over the control of the front axle steering system from the first control unit.

[0017] For the rear axle steering system, when the third servo motor fails, the third electromagnetic clutch disengages, the third servo motor stops assisting, the fourth electromagnetic clutch engages, and the fourth servo motor starts working; when the second drive motor fails, the second oil pump clutch disengages, stopping hydraulic assisting, the fourth electromagnetic clutch engages, and the fourth servo motor starts working, with the third and fourth servo motors jointly providing assistance, and the vehicle enters pure electric power steering mode; when the third control unit fails, the fourth control unit takes over the control of the rear axle steering system from the third control unit.

[0018] Preferably, the control method of the steer-by-wire dual-power steering system with rear axle active steering involves the following steps: When the vehicle makes a large-angle turn, the mode selector is used to enter a low-speed four-wheel steering mode, in which the front axle steering system and the rear axle steering system turn in opposite phases to reduce the turning radius; when the vehicle turns at low speed in a narrow space, the mode selector is used to enter a crab steering mode, in which the front axle steering system and the rear axle steering system turn in the same phase to quickly enter the target area; when the vehicle is traveling at high speed, the rear axle steering system is set to not turn to ensure stability and control precision during driving; in case of emergency avoidance or turning, the active steering function of the rear axle steering system is activated to improve the vehicle's agility.

[0019] Preferably, the control method of the steer-by-wire dual power steering system with rear axle active steering is as follows: when the vehicle is in low-speed four-wheel steering mode and crab steering mode, the second servo motor and the fourth servo motor are engaged to work together with the first servo motor and the third servo motor to assist steering; when the vehicle is traveling at high speed, hydraulic power steering is stopped and the vehicle enters pure electric power steering mode.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] 1. This invention uses the front axle steering system control unit to output the optimal distribution of assist current to the corresponding actuator motor based on the torque angle signal and vehicle speed signal of the driver operating the steering wheel 1, according to a pre-written algorithm. The design of multiple steering modes enables the vehicle to achieve good steering under various road conditions; the design of multiple power steering modes can achieve optimized distribution of vehicle energy.

[0022] 2. Regarding the rear axle steering system, when the third servo motor malfunctions, the third electromagnetic clutch disengages, the third servo motor stops assisting, and the fourth electromagnetic clutch engages, allowing the fourth servo motor to operate. When the second drive motor malfunctions, the second oil pump clutch disengages, stopping hydraulic assist, the fourth electromagnetic clutch engages, and the fourth servo motor operates. The third and fourth servo motors jointly provide assistance, and the vehicle enters pure electric power steering mode. When the third control unit malfunctions, the fourth control unit takes over the control of the rear axle steering system, eliminating the mechanical connection between the steering wheel and the steering actuator, as well as the mechanical connection between the front axle steering system and the rear axle steering system. By adopting a drive-by-wire connection, space is saved.

[0023] 3. This invention controls the associated mechanism through a control assembly, which includes a steering wheel, torque angle sensor, road feel motor and motor reduction mechanism. The steering column between the steering wheel and the steering mechanism is eliminated. The road feel motor simulates specific road feel and realizes steering return. Since there is no direct mechanical connection between the front and rear axles, multi-axle active steering can theoretically be realized.

[0024] 4. The present invention has redundant components in multiple parts. The second control unit 8 is set as a redundant component of the first control unit 7, and the fourth control unit 8 is set as a redundant component of the third control unit 7. This allows the second or fourth control unit to quickly take over when the first or third control unit fails. This enables the use of redundant components to replace faulty components when a component fails, thus ensuring the driving safety of drivers and passengers. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the system connection structure of the present invention;

[0026] Figure 2 This is a flowchart illustrating Embodiment 1 of the present invention;

[0027] Figure 3 This is a flowchart illustrating Embodiment 2 of the present invention.

[0028] In the diagram: 1. Steering wheel; 2. Torque angle sensor; 3. Road sensor motor; 4. Motor reduction mechanism; 5. Vehicle controller; 6. Mode selector; 7. First control unit; 8. Second control unit; 9. First servo motor; 10. First electromagnetic clutch; 11. Second servo motor; 12. Second electromagnetic clutch; 13. First worm gear reduction mechanism; 14. First drive motor; 15. First oil pump clutch; 16. First hydraulic pump; 17. First recirculating ball steering assembly; 18. Front axle steering linkage; 19. Front axle wheel; 20. Third control unit; 21. Fourth control unit; 22. Third servo motor; 23. Third electromagnetic clutch; 24. Fourth servo motor; 25. Fourth electromagnetic clutch; 26. Second worm gear reduction mechanism; 27. Second drive motor; 28. Second oil pump clutch; 29. ​​Second hydraulic pump; 30. Second recirculating ball steering assembly; 31. Rear axle steering linkage; 32. Rear axle wheel. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] Please see Figure 1-3 The present invention provides a technical solution: a steer-by-wire dual-power steering system with active rear axle steering, including a control assembly, a front axle steering system, a rear axle steering system and a vehicle controller 5, characterized in that: it also includes a mode selector 6, the front axle steering system and the rear axle steering system are symmetrically distributed and connected to the vehicle controller 5 with coordination function, and both the front axle steering system and the rear axle steering system are connected to the vehicle controller 5 via a CAN bus.

[0031] The control assembly includes a steering wheel 1, a torque angle sensor 2, a road feel motor 3, and a motor reduction mechanism 4. The steering column between the steering wheel 1 and the steering mechanism has been eliminated. The road feel motor 3 simulates specific road feel and realizes steering return to center.

[0032] The front axle steering system includes a first control unit 7, a second control unit 8, a first servo motor 9, a first electromagnetic clutch 10, a first worm gear reduction mechanism 13, a second servo motor 11, a second electromagnetic clutch 12, a first drive motor 14, a first oil pump clutch 15, a first hydraulic pump 16, a first recirculating ball steering assembly 17, a front axle steering linkage 18, and an oil tank. The second control unit 8 is a redundant component of the first control unit 7, which can quickly take over when the first control unit 7 fails. The first servo motor 9 is the main power steering motor for the front axle, and the second servo motor 11 is an auxiliary backup motor. Both the first servo motor 9 and the second servo motor 11 are electrically connected to the first control unit 7 and the second control unit 8. The first control unit 7 controls whether the first servo motor 9 and the second servo motor 11 are engaged or not by controlling the on / off state of the first electromagnetic clutch 10 and the second electromagnetic clutch 12.

[0033] The first servo motor 9, the second servo motor 11, and the first drive motor 14 are all equipped with speed sensors to monitor rotational speed. The first hydraulic pump 16 is equipped with temperature and pressure sensors to monitor the hydraulic oil temperature and pump pressure. A vehicle speed sensor is installed inside the front axle wheel 19 to monitor vehicle speed. Wheel angle sensors are installed on the wheel suspension system to monitor steering angle. The front axle steering system is primarily assisted by the pressure generated by high-pressure hydraulic fluid, with the first servo motor 9 and the second servo motor 11 providing auxiliary assistance. When the hydraulic power steering module malfunctions, a pure electric power steering mode can be entered: the second servo motor 11 engages and works together with the first servo motor 9 to provide steering assistance.

[0034] The rear axle steering system includes a third control unit 20, a fourth control unit 21, a third servo motor 22, a third electromagnetic clutch 23, a second worm gear reducer 26, a fourth servo motor 24, a fourth electromagnetic clutch 25, a second drive motor 27, a second oil pump clutch 28, a second hydraulic pump 29, a second recirculating ball steering assembly 30, a rear axle steering linkage 31, and an oil tank. The fourth control unit 21 is a redundant component of the third control unit 20 and can take over the work when the third control unit 20 fails. The third servo motor 22 is the main power steering motor for the rear axle, and the fourth servo motor 24 is an auxiliary backup motor. Both the third servo motor 22 and the fourth servo motor 24 are electrically connected to the third control unit 20 and the fourth control unit 21. The third control unit 20 controls whether the third servo motor 22 and the fourth servo motor 24 are engaged or not by controlling the on / off state of the third electromagnetic clutch 23 and the fourth electromagnetic clutch 25.

[0035] Speed ​​sensors are installed on the third servo motor 22, the fourth servo motor 24, and the second drive motor 27 to monitor rotational speed. A temperature and pressure sensor is installed on the second hydraulic pump 29 to monitor the temperature and pressure of the hydraulic oil. A vehicle speed sensor is installed inside the rear axle wheel 32 to measure vehicle speed. Wheel angle sensors are installed on the wheel suspension system to monitor steering accuracy. The pressure generated by the high-pressure hydraulic fluid provides primary steering assistance, while the two servo motors provide auxiliary assistance. When the hydraulic power steering module malfunctions, it can enter a pure electric power steering mode, in which the fourth servo motor 24 operates in conjunction with the third servo motor 22 to provide steering assistance.

[0036] The mode selector 6 is installed between the first control unit 7 and the third control unit 20. The driver selects different steering modes according to the current road conditions. The vehicle controller 5 transmits control signals to the first control unit 7 and the third control unit 20 to control the front axle steering and the rear axle steering. The specific steps include the following:

[0037] a. The vehicle controller 5 outputs corresponding control signals to the front axle steering system control unit (including the first control unit 7 and the second control unit 8) and the rear axle steering system control unit (including the third control unit 20 and the fourth control unit 21) based on the signal from the mode selector 6.

[0038] b. The front axle steering system control unit outputs the optimal distribution of assist current to the corresponding actuator motor to control the front axle steering based on the torque angle signal and vehicle speed signal of the driver operating the steering wheel, according to a pre-written algorithm.

[0039] c. The rear axle steering system control unit outputs a corresponding control current to control the rear axle steering based on the front axle steering angle and vehicle speed signals and the control signals transmitted by the vehicle controller 5.

[0040] It also includes fault control. For the front axle steering system, when the first servo motor 9 fails, the first electromagnetic clutch 10 disengages, the first servo motor 9 stops assisting, the second electromagnetic clutch 12 engages, and the second servo motor 11 starts working. When the first drive motor 14 fails, the first oil pump clutch 15 disengages, stopping hydraulic assisting, the second electromagnetic clutch 12 engages, and the second servo motor 11 starts working. The first servo motor 9 and the second servo motor 11 jointly provide assistance, and the vehicle enters pure electric power steering mode. When the first control unit 7 fails, the second control unit 8 takes over the control of the front axle steering system from the first control unit 7.

[0041] For the rear axle steering system, when the third servo motor 22 fails, the third electromagnetic clutch 23 disengages, the third servo motor 22 stops assisting, the fourth electromagnetic clutch 25 engages, and the fourth servo motor 24 starts working; when the second drive motor 27 fails, the second oil pump clutch 28 disengages, stopping hydraulic assisting, the fourth electromagnetic clutch 25 engages, and the fourth servo motor 24 starts working, with the third servo motor 22 and the fourth servo motor 24 jointly providing assist, and the vehicle enters pure electric power assist mode; when the third control unit 20 fails, the fourth control unit 21 takes over the control of the rear axle steering system from the third control unit 20.

[0042] When the vehicle makes a large-angle turn, the low-speed four-wheel steering mode can be set via mode selector 6, where the front and rear axle steering systems turn in opposite phases to reduce the turning radius. When the vehicle turns at low speed in a narrow space, the crab steering mode can be set via mode selector 6, where the front and rear axle steering systems turn in the same phase to quickly enter the target area. When the vehicle is traveling at high speed, the rear axle steering system is set to not turn to ensure stability and control precision. In case of emergency avoidance or turning, the active steering function of the rear axle steering system is activated to improve the vehicle's agility.

[0043] When the vehicle is in low-speed four-wheel steering mode and crab steering mode, the second servo motor 11 and the fourth servo motor 24 are engaged to assist steering in conjunction with the first servo motor 9 and the third servo motor 22, respectively; when the vehicle is traveling at high speed, hydraulic power steering is stopped and pure electric power steering mode is entered. Example 1

[0044] The front axle steering system includes a first control unit 7, a second control unit 8, a first servo motor 9, a first electromagnetic clutch 10, a first worm gear reduction mechanism 13, a second servo motor 11, a second electromagnetic clutch 12, a first drive motor 14, a first oil pump clutch 15, a first hydraulic pump 16, a first recirculating ball steering assembly 17, a front axle steering linkage 18, and an oil tank. The second control unit 8 is a redundant component of the first control unit 7, which can quickly take over when the first control unit 7 fails. The first servo motor 9 is the main power steering motor for the front axle, and the second servo motor 11 is an auxiliary backup motor. Both the first servo motor 9 and the second servo motor 11 are electrically connected to the first control unit 7 and the second control unit 8. The first control unit 7 controls whether the first servo motor 9 and the second servo motor 11 are engaged or not by controlling the on / off state of the first electromagnetic clutch 10 and the second electromagnetic clutch 12.

[0045] The first servo motor 9, the second servo motor 11, and the first drive motor 14 are all equipped with speed sensors to monitor speed. The first hydraulic pump 16 is equipped with a temperature and pressure sensor to monitor the temperature of the hydraulic oil and the pressure inside the pump. The front axle wheel 19 is equipped with a vehicle speed sensor to monitor the vehicle speed. The wheel suspension system is equipped with a wheel angle sensor to monitor the steering angle.

[0046] The front axle steering system is primarily assisted by pressure generated by high-pressure hydraulic fluid. The first servo motor 9 and the second servo motor 11 provide auxiliary assistance. When the hydraulic power steering module malfunctions, it can enter pure electric power steering mode, in which case the second servo motor 11 will engage and work together with the first servo motor 9 to provide steering assistance.

[0047] The rear axle steering system includes a third control unit 20, a fourth control unit 21, a third servo motor 22, a third electromagnetic clutch 23, a second worm gear reducer 26, a fourth servo motor 24, a fourth electromagnetic clutch 25, a second drive motor 27, a second oil pump clutch 28, a second hydraulic pump 29, a second recirculating ball steering assembly 30, a rear axle steering linkage 31, and an oil tank. The fourth control unit 21 is a redundant component of the third control unit 20 and can take over the work when the third control unit 20 fails. The third servo motor 22 is the main power steering motor for the rear axle, and the fourth servo motor 24 is an auxiliary backup motor. Both the third servo motor 22 and the fourth servo motor 24 are electrically connected to the third control unit 20 and the fourth control unit 21. The third control unit 20 controls whether the third servo motor 22 and the fourth servo motor 24 are engaged or not by controlling the on / off state of the third electromagnetic clutch 23 and the fourth electromagnetic clutch 25.

[0048] The third servo motor 22, the fourth servo motor 24, and the second drive motor 27 are all equipped with speed sensors to monitor speed. The second hydraulic pump 29 is equipped with a temperature and pressure sensor to monitor the temperature and pressure of the hydraulic oil. A vehicle speed sensor is installed in the rear axle wheel 32 to measure the vehicle speed. A wheel angle sensor is installed on the wheel suspension system to monitor steering accuracy. The pressure generated by the high-pressure hydraulic fluid provides the main power assist, and the two servo motors provide auxiliary power assist. When the hydraulic power assist module fails, it can enter the pure electric power assist mode, and the second servo motor 11 will work together with the first servo motor 9 to provide steering assistance. Example 2

[0049] The control method for a steer-by-wire dual-power steering system with active rear axle steering includes: the system is equipped with a mode selector 6, which allows the driver to select different steering modes according to the current road conditions, and transmits control signals to the first control unit 7 and the third control unit 20 via the vehicle controller 5 to control the front axle steering and the rear axle steering.

[0050] Furthermore, when the vehicle makes a large-angle turn in place, it can be set to enter four-wheel steering mode, with the front and rear axles turning in opposite phases to reduce the turning radius; when the vehicle turns at low speed in a narrow space, it can be set to enter crab steering mode, with the front and rear axles turning in the same phase to quickly enter the target area; when the vehicle is traveling at high speed, the rear axle is set not to turn to ensure stability and control precision during driving; in case of emergency avoidance or turning, the rear axle active steering function is activated to improve the vehicle's agility.

[0051] Furthermore, when the vehicle is in low-speed four-wheel steering and crab steering, the second and fourth motors can be engaged to assist the first servo motor 9 and the third servo motor 22 in steering, respectively; when the vehicle is traveling at high speed, hydraulic power steering can be stopped, and the second servo motor 11 and the fourth servo motor 24 can be engaged to enter pure electric power steering mode.

[0052] Furthermore, the specific steps include the following:

[0053] a. The vehicle controller 5 outputs corresponding control signals to the front axle steering control unit and the rear axle steering control unit based on the signal from the mode selector 6.

[0054] b. The front axle steering system control unit outputs the optimal distribution of assist current to the corresponding actuator motor according to the torque angle signal and vehicle speed signal of the driver operating the steering wheel 1, based on a pre-written algorithm, to control the front axle steering.

[0055] c. The rear axle steering system control unit outputs the optimal distribution of assist current to the corresponding actuator motor based on the front axle steering angle and vehicle speed signals and the control signals transmitted by the vehicle controller 5, in order to control the rear axle steering.

[0056] Furthermore, the control method also includes: for the front axle steering system, when the first servo motor 9 fails, the first electromagnetic clutch 10 disengages, the first servo motor 9 stops assisting, the second electromagnetic clutch 12 engages, and the second servo motor 11 starts working; when the first drive motor 14 fails, the first oil pump clutch 15 disengages, stopping hydraulic assisting, the second electromagnetic clutch 12 engages, and the second servo motor 11 starts working, with the first servo motor 9 and the second servo motor 11 jointly providing assistance, and the vehicle enters pure electric power assist mode; when the first control unit 7 fails, the second control unit 8 takes over from the first control unit 7 to perform control of the front axle steering system.

[0057] For the rear axle steering system, when the third servo motor 22 fails, the third electromagnetic clutch 23 disengages, the third servo motor 22 stops assisting, the fourth electromagnetic clutch 25 engages, and the fourth servo motor 24 starts working; when the second drive motor 27 fails, the second oil pump clutch 28 disengages, stopping hydraulic assisting, the fourth electromagnetic clutch 25 engages, and the fourth servo motor 24 starts working, with the third servo motor 22 and the fourth servo motor 24 jointly providing assistance, and the vehicle enters pure electric power assist mode; when the third control unit 20 fails, the fourth control unit 21 takes over the control of the rear axle steering system from the third control unit 20.

[0058] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A steer-by-wire dual-power steering system with active rear axle steering, comprising a control assembly, a front axle steering system, a rear axle steering system, and a vehicle controller (5), characterized in that: It also includes a mode selector (6), the front axle steering system and the rear axle steering system are symmetrically distributed and connected to a vehicle controller (5) with coordination function, and both the front axle steering system and the rear axle steering system are connected to the vehicle controller (5) via CAN bus communication. The front axle steering system includes a first control unit (7), a second control unit (8), a first servo motor (9), a first electromagnetic clutch (10), a first worm gear reduction mechanism (13), a second servo motor (11), a second electromagnetic clutch (12), a first drive motor (14), a first oil pump clutch (15), a first hydraulic pump (16), a first recirculating ball steering assembly (17), a front axle steering linkage (18), and an oil tank. The second control unit (8) is set as a redundant component of the first control unit (7) so that it can quickly take over when the first control unit (7) fails. The first servo motor (9) is the main power steering motor for the front axle, and the second servo motor (11) is an auxiliary backup motor. The first servo motor (9) and the second servo motor (11) are electrically connected to the first control unit (7) and the second control unit (8). The first control unit (7) controls whether the first servo motor (9) and the second servo motor (11) are engaged or not by controlling the on and off of the first electromagnetic clutch (10) and the second electromagnetic clutch (12). The rear axle steering system includes a third control unit (20), a fourth control unit (21), a third servo motor (22), a third electromagnetic clutch (23), a second worm gear reduction mechanism (26), a fourth servo motor (24), a fourth electromagnetic clutch (25), a second drive motor (27), a second oil pump clutch (28), a second hydraulic pump (29), a second recirculating ball steering assembly (30), a rear axle steering linkage (31), and an oil tank. The fourth control unit (21) is configured as a redundant component of the third control unit (20). When unit (20) fails, it can take over the work of the third control unit (20). The third servo motor (22) is the main steering assist motor of the rear axle, and the fourth servo motor (24) is the auxiliary backup motor. The third servo motor (22) and the fourth servo motor (24) are electrically connected to the third control unit (20) and the fourth control unit (21). The third control unit (20) controls whether the third servo motor (22) and the fourth servo motor (24) are engaged or not by controlling the opening and closing of the third electromagnetic clutch (23) and the fourth electromagnetic clutch (25).

2. The steer-by-wire dual-power steering system with rear axle active steering as described in claim 1, characterized in that: The control assembly includes a steering wheel (1), a torque angle sensor (2), a road feel motor (3) and a motor reduction mechanism (4). The road feel motor (3) simulates the steering road feel and realizes steering return to center.

3. The steer-by-wire dual-power steering system with rear axle active steering as described in claim 1, characterized in that: The first servo motor (9), the second servo motor (11) and the first drive motor (14) are all equipped with speed sensors to monitor speed. The first hydraulic pump (16) is equipped with a temperature and pressure sensor to monitor the temperature of the hydraulic oil and the pressure inside the pump. The front axle wheel (19) is equipped with a vehicle speed sensor to monitor the vehicle speed. The first servo motor (9) and the second servo motor (11) are used to provide auxiliary power.

4. The steer-by-wire dual-power steering system with rear axle active steering as described in claim 1, characterized in that: The third servo motor (22), the fourth servo motor (24), and the second drive motor (27) are all equipped with speed sensors to monitor speed. The second hydraulic pump (29) is equipped with a temperature and pressure sensor to monitor the temperature and pressure of the hydraulic oil. The rear axle wheel (32) is equipped with a vehicle speed sensor to measure the vehicle speed. The wheel suspension system is equipped with a wheel angle sensor to monitor steering accuracy.

5. The control method for a steer-by-wire dual-power steering system with rear axle active steering according to any one of claims 1-4, characterized in that: The mode selector (6) is installed between the first control unit (7) and the third control unit (20). The driver selects different steering modes according to the current road conditions, and transmits control signals to the first control unit (7) and the third control unit (20) through the vehicle controller (5) to control the front axle steering and the rear axle steering. Specifically, the following steps are included: a. The vehicle controller (5) outputs corresponding control signals to the front axle steering system control unit and the rear axle steering system control unit according to the signal from the mode selector (6); b. The front axle steering system control unit outputs the optimal distribution of assist current to the corresponding actuator motor to control the front axle steering based on the torque angle signal and vehicle speed signal of the driver operating the steering wheel, according to a pre-written algorithm. c. The rear axle steering system control unit outputs a corresponding control current to control the rear axle steering based on the front axle steering angle and vehicle speed signals and the control signals transmitted by the vehicle controller (5).

6. The control method for a steer-by-wire dual-power steering system with rear axle active steering according to claim 5, characterized in that, It also includes fault control. For the front axle steering system, when the first servo motor (9) fails, the first electromagnetic clutch (10) disengages, the first servo motor (9) stops assisting, the second electromagnetic clutch (12) engages, and the second servo motor (11) starts working. When the first drive motor (14) fails, the first oil pump clutch (15) disengages, stops hydraulic assisting, the second electromagnetic clutch (12) engages, and the second servo motor (11) starts working. The first servo motor (9) and the second servo motor (11) work together to provide assistance, and the vehicle enters pure electric power assist mode. When the first control unit (7) fails, the second control unit (8) takes over the control of the front axle steering system from the first control unit (7). For the rear axle steering system, when the third servo motor (22) malfunctions, the third electromagnetic clutch (23) disengages, the third servo motor (22) stops assisting, the fourth electromagnetic clutch (25) engages, and the fourth servo motor (24) starts working; when the second drive motor (27) malfunctions, the second oil pump clutch (28) disengages, stopping hydraulic assisting, the fourth electromagnetic clutch (25) engages, and the fourth servo motor (24) starts working, the third servo motor (22) and the fourth servo motor (24) jointly provide assistance, and the vehicle enters pure electric power assist; when the third control unit (20) malfunctions, the fourth control unit (21) takes over the control of the rear axle steering system from the third control unit (20).

7. The control method for a steer-by-wire dual-power steering system with rear axle active steering according to claim 5, characterized in that, When the vehicle makes a large-angle turn, the mode selector (6) is set to enter the low-speed four-wheel steering mode, and the front axle steering system and the rear axle steering system turn in opposite phase to reduce the turning radius. When the vehicle turns at low speed in a narrow space, the mode selector (6) is set to enter the crab steering mode, and the front axle steering system and the rear axle steering system turn in the same phase to quickly enter the target area. When the vehicle is traveling at high speed, the rear axle steering system is set not to turn to ensure stability and control accuracy during driving. When an emergency avoidance or turn occurs, the active steering function of the rear axle steering system is activated to improve the vehicle's flexibility.

8. The control method for a steer-by-wire dual-power steering system with rear axle active steering according to claim 7, characterized in that, When the vehicle is in low-speed four-wheel steering mode and crab steering mode, the second servo motor (11) and the fourth servo motor (24) are engaged to assist steering in coordination with the first servo motor (9) and the third servo motor (22), respectively. When the vehicle is traveling at high speed, hydraulic power assist is stopped and pure electric power assist mode is entered.

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