A pre-accumulation electro-hydraulic coupling steer-by-wire system and an energy-saving mode switching method thereof

Abstract

The application discloses a novel pre-accumulation electro-hydraulic coupled steer-by-wire system and an energy-saving mode switching method thereof, and the system comprises an electric cylinder module, an electric hydraulic module, an accumulator module, a steering gear module, an ECU control module and a vehicle-mounted sensing module; the novel pre-accumulation electro-hydraulic coupled steer-by-wire system has an electric cylinder steering mode, an electric cylinder-accumulator steering mode and an electric cylinder-accumulator-hydraulic pump steering mode; the control method of the system is as follows: when driving in a straight line, the electric pump pre-accumulates the accumulator until the accumulator is full; the vehicle-mounted sensing module collects a navigation steering path and a vehicle state, and the ECU control module decides a steering mode according to the navigation steering path and the vehicle state. The application proposes a steering energy-saving mode switching method based on a future navigation steering path of a vehicle, decides a steering mode in a future period of time according to the steering path with the energy-saving as the target, and effectively improves the steering energy-saving property of the vehicle.

Description

Technical Field

[0001] This invention relates to the technical field of electro-hydraulic composite steering, and more particularly to a pre-stored energy electro-hydraulic coupled steer-by-wire system and its energy-saving mode switching method. Background Technology

[0002] Commercial vehicles have become one of the main modes of transportation in my country due to their convenience, economy, and versatility in carrying cargo. Compared to passenger cars, commercial vehicles have greater steering resistance due to their heavier weight, making pure electric motor-driven steer-by-wire systems unable to provide sufficient steering power. Electro-hydraulic coupled steer-by-wire systems combine the rapid response of electric motors with the high power density of hydraulic systems, providing ample steering power for commercial vehicles and meeting the requirements for steering tracking accuracy. Therefore, electro-hydraulic coupled steer-by-wire systems represent the future development trend of steer-by-wire systems for commercial vehicles.

[0003] However, significant differences in response and energy consumption characteristics between the motor and electric pump in existing electro-hydraulic coupled steer-by-wire systems result in both operating in low-efficiency regions during steering, leading to substantial energy loss. Furthermore, at the start, change of direction, and stop of steering, the electric pump's response speed is much slower than the motor due to its higher rotational inertia and hydraulic oil resistance, requiring the motor to output additional torque and further increasing energy loss. In summary, existing electro-hydraulic coupled steer-by-wire systems suffer from high energy consumption. Therefore, designing a novel low-energy electro-hydraulic coupled steer-by-wire system and its energy-saving mode switching method, tailored to the operating characteristics of such systems, has become an urgent problem to be solved in this field. Summary of the Invention

[0004] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0005] In view of the problems existing in the above-mentioned pre-storage electro-hydraulic coupled steering-by-wire system and its energy-saving mode switching method, the present invention is proposed.

[0006] Therefore, the purpose of this invention is to provide a pre-stored energy electro-hydraulic coupled steer-by-wire system and its energy-saving mode switching method. The energy-saving steering mode switching method based on the vehicle's future navigation steering path determines the steering mode for a future period of time based on the steering path with energy saving as the goal, effectively improving the vehicle's steering energy efficiency.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a pre-stored energy electro-hydraulic coupled steer-by-wire system, comprising: Steering module, electric cylinder module, electro-hydraulic module, accumulator module, ECU control module, and vehicle sensing module; The steering module connects the electric cylinder module and the electro-hydraulic module. The steering module includes steering tie rods, wheels, and steering tie rod sensors. Each wheel on both sides is connected to a steering tie rod. The radius of one side of each steering tie rod is consistent with the inner diameter of the hydraulic cylinder of the electro-hydraulic module, and the internal cavity is connected to the ball screw of the electric cylinder module. The other side of the steering tie rod passes through the hydraulic cylinder and is connected to the wheel. One end of the steering tie rod sensor is connected to the steering tie rod, and the other end is connected to the hydraulic cylinder. The electric cylinder module connects the steering gear module and the ECU control module. The electric cylinder module includes: a steering motor, a steering motor reducer, and a ball screw. The steering motor adjusts the torque according to the instructions of the ECU control module, and the torque is reduced and increased by the steering motor reducer and then transmitted to the ball screw. The ball screw converts the torque into force and acts on the steering tie rod to push the steering tie rod to move. The electro-hydraulic module is connected to the steering module via a hydraulic cylinder, to the accumulator module via an oil circuit, and to the ECU control module via a communication line. The electro-hydraulic module includes: an electric pump, a solenoid directional valve, a hydraulic cylinder, an oil circuit, and an oil reservoir. The electric pump adjusts its output torque according to the instructions transmitted by the ECU control module to pump hydraulic oil from the oil reservoir into the oil circuit. The oil circuit is connected to the solenoid directional valve, which determines the direction of hydraulic oil flow into the hydraulic cylinder, creating a hydraulic differential on both sides of the steering tie rod, which pushes the steering tie rod to move. The pressure sensors for the left and right hydraulic cylinders are respectively placed inside the hydraulic cylinders on both sides. The accumulator module is connected to the electro-hydraulic module via an oil circuit and to the ECU control module via a communication line. The accumulator module includes: an accumulator, a high-speed switching directional valve, and an accumulator pressure sensor. The high-speed switching directional valve is connected to the oil supply circuit of the electro-hydraulic module. The high-speed switching valve regulates the flow direction and flow rate of the hydraulic oil according to the instructions of the ECU control module, determining whether the accumulator stores or releases energy. The accumulator pressure sensor is placed inside the accumulator. The ECU control module is connected to the electro-hydraulic module, electric cylinder module, accumulator module and vehicle sensing module via communication lines; the vehicle sensing module is connected to the ECU control module via communication lines.

[0008] As a preferred embodiment of the pre-energy-storage electro-hydraulic coupled steer-by-wire system of the present invention, the ECU control module runs an energy-saving mode switching method for the pre-energy-storage electro-hydraulic coupled steer-by-wire system, receiving navigation steering path, vehicle status signal, hydraulic cylinder pressure signal, accumulator pressure signal and steering tie rod signal; after calculation, the ECU control module sends steering mode commands to the electro-hydraulic module, electric cylinder module and accumulator module.

[0009] As a preferred embodiment of the pre-energy-storage electro-hydraulic coupling steer-by-wire system of the present invention, the vehicle-mounted sensing module collects real-time maps of the navigation and steering path and vehicle status signals within the next 180 seconds and transmits them to the ECU control module. The vehicle status signals include: vehicle yaw rate signal, vehicle speed signal, center of gravity sideslip angle signal and front wheel steering angle signal.

[0010] The method for switching energy-saving modes in a pre-storage electro-hydraulic coupled steer-by-wire system includes the following steps: S1. Based on the dynamic model and efficiency diagram of the novel pre-stored electro-hydraulic coupled steer-by-wire system, draw the offline optimal steering energy consumption diagram for three steering modes. S2. When driving in a straight line, the electric pump operates in the high-efficiency range to pre-store energy in the accumulator until the accumulator is fully charged. S3. The vehicle sensing module acquires the steering path and real-time vehicle yaw angle, vehicle speed, center of gravity sideslip angle and front wheel angle signals within the next 180 seconds. The tie rod displacement sensor, hydraulic cylinder pressure sensor and accumulator pressure sensor collect the steering tie rod displacement signal, the pressure difference signal between the oil chambers on both sides of the hydraulic cylinder and the pressure signal in the accumulator in real time. S4. The ECU control module receives the signal from step S3 and calculates the expected resistance torque of the steering system within the next 180 seconds based on the vehicle kinematics model and dynamics model and the collected navigation steering path. S5. Calculate the energy-optimal steering mode switching trajectory based on the offline optimal steering energy consumption map and the online optimized cost function.

[0011] As a preferred embodiment of the energy-saving mode switching method for the pre-energy-storage electro-hydraulic coupled steer-by-wire system described in this invention, the specific steps of the offline optimal steering energy consumption map include: S11. Within the maximum steering power range, with the front wheel steering angle resistance torque as the x-axis, the speed as the y-axis, and the accumulator pressure as the z-axis, design the steering system operating point set using the average sampling method; S12. Optimal steering energy consumption diagram based on steering motor efficiency diagram and steering system operating point set fitting of electric cylinder steering mode; S13. A dynamic model of a novel pre-energy-storage electro-hydraulic coupled steer-by-wire system based on electric cylinder-accumulator steering mode. With the goal of minimizing the energy consumption of the steering system, the power of the electric cylinder-accumulator steering mode at each working point in the working set is optimized by using a cost function, and the optimal steering energy consumption map of the electric cylinder-accumulator steering mode is fitted by interpolation. S14. Dynamic model and efficiency diagram of a novel pre-stored electro-hydraulic coupled steer-by-wire system based on electric cylinder-accumulator-electric pump steering mode. With the goal of minimizing the energy consumption of the steering system, the power of the electric cylinder-accumulator-electric pump steering mode at each working point in the working set is optimized, and the optimal steering energy consumption diagram of the electric cylinder-accumulator-electric pump steering mode is fitted by interpolation method. S15. Compare the optimal steering energy consumption diagrams of the three steering modes under different working points, select the steering mode with the highest efficiency under the working point power requirements, and thus obtain the offline optimal steering energy consumption diagram with the front wheel steering angle resistance torque as the x-axis, the speed as the y-axis, and the accumulator pressure as the z-axis.

[0012] As a preferred embodiment of the energy-saving mode switching method for the pre-energy-storage electro-hydraulic coupled steer-by-wire system described in this invention, wherein: the efficiency diagram of the steering motor in step S12... The optimal steering energy consumption at each operating point in the electric cylinder steering mode was obtained through testing the steering motor. Obtained from the following formula: (1) in, For the front wheel steering resistance torque, The moment of inertia of the front wheels, For front wheel damping, The front wheel angular velocity, The front wheel angular acceleration, The force output by the steering tie rod. This refers to the gear ratio between the steering tie rod and the front wheels. For the mass of the steering tie rod, For the damping of the steering tie rod, For the speed of the steering tie rod, The acceleration of the steering tie rod, The force output by the electric cylinder. This refers to the transmission ratio between the steering motor and the steering tie rod. This refers to the rotational speed of the steering motor. This is the torque output by the steering motor.

[0013] As a preferred embodiment of the energy-saving mode switching method for the pre-storage electro-hydraulic coupled steer-by-wire system of the present invention, wherein: the dynamic model of the steering gear module of the novel pre-storage electro-hydraulic coupled steer-by-wire system in the electric cylinder-accumulator steering mode in step S13 is: (2) in, The force output by the hydraulic cylinder. The surface area of ​​one side of the steering tie rod hydraulic cylinder. The pressure on the high-pressure side of the hydraulic cylinder; In step S13, the pressure on the high-pressure side of the hydraulic cylinder of the novel pre-stored electro-hydraulic coupled wire-controlled steering system in the electric cylinder-accumulator steering mode... Obtained through the following formula: (3) in, For the oil pressure in the oil supply circuit, The oil pressure inside the accumulator. The flow rate output by the energy storage device. The density of the hydraulic oil, It is the acceleration due to gravity. r p The radius of the oil supply pipeline, For the displacement of the steering tie rod, The height difference between the accumulator and the hydraulic cylinder. This refers to the opening area of ​​the high-speed switching valve / directional valve. The flow coefficient of the high-speed switching valve / directional valve. Let be the leakage coefficient of the hydraulic cylinder. The maximum total volume of hydraulic oil that the accumulator's internal space can hold. The pressure when the accumulator is full of hydraulic oil. The rate of change of oil pressure within the accumulator; In step S13, the cost function of the electric cylinder-accumulator steering mode constrained by equations (2) and (3) is shown in equation (4). Based on equation (4), calculations are performed for each working point in the working set, and the optimal steering energy consumption diagram of the electric cylinder-accumulator steering mode is fitted according to the results. ; (4) in, Energy consumption for electric cylinder-accumulator steering mode. This represents the highest operating efficiency of the electric pump.

[0014] As a preferred embodiment of the energy-saving mode switching method for the pre-storage electro-hydraulic coupled steer-by-wire system of the present invention, wherein: in step S14, the pressure on the high-pressure side of the hydraulic cylinder of the novel pre-storage electro-hydraulic coupled steer-by-wire system under the electric cylinder-accumulator-electric pump steering mode is: (5) in, The flow rate output by the electric pump. This refers to the displacement of the electric pump. The speed of the electric pump. The flow output efficiency of the electric pump. The torque of the electric pump, The torque output efficiency of the electric pump; In step S14, the cost function of the electric cylinder-accumulator-electric pump steering mode constrained by equations (2) and (5) is shown in equation (6). Based on equation (6), calculations are performed for each working point in the working set, and the optimal steering energy consumption diagram of the electric cylinder-accumulator-electric pump steering mode is fitted according to the results. ; (6) in, This is an efficiency diagram for an electric pump, which can be obtained by testing the electric pump.

[0015] The comparison method of the optimal steering energy consumption map of the three steering modes at different working points in step S15 is shown in Equation (7). The steering mode with the lowest energy consumption at each working point is retained through the traversal of the working points, and the offline optimal steering energy consumption map is fitted. ; (7) in, , and They refer to the first i The front wheel steering resistance torque, front wheel speed, and accumulator pressure at each operating point.

[0016] As a preferred embodiment of the energy-saving mode switching method for the pre-energy-storage electro-hydraulic coupling steer-by-wire system described in this invention, step S4 further includes the following steps: S41. Based on the vehicle kinematics model, calculate the vehicle's yaw rate trajectory and center of gravity sideslip trajectory within the next 180 seconds according to the navigation and steering path within the next 180 seconds. S42. Using a vehicle dynamics model, track the vehicle's yaw rate trajectory and center of gravity sideslip trajectory within the next 180 seconds to predict the trajectory of the steering resistance torque generated by the front tires. In step S41, the desired yaw rate trajectory and the desired centroid sideslip angle trajectory are obtained by solving the navigation turning path within the next 180s based on equation (8). (8) in, k The first in 180 seconds k time, For the desired yaw rate, To determine the desired centroid sideslip angle, This represents the longitudinal position of the navigation turning path. This represents the lateral position of the navigation turning path. for k The longitudinal position of the vehicle at any given time. This refers to the front wheelbase. Rear wheelbase For the front wheel lateral stiffness, For rear wheel lateral stiffness, Wheelbase For vehicle quality, For vehicle speed; In step S42, the trajectory of the steering resistance torque generated by the front tires is predicted by equation (9) based on the expected yaw rate trajectory and the expected center of gravity sideslip angle trajectory. (9) in, To achieve the desired front wheel steering angle, To achieve the desired steering resistance torque, This refers to tire trail.

[0017] As a preferred embodiment of the energy-saving mode switching method for the pre-energy-storage electro-hydraulic coupling steer-by-wire system described in this invention, step S5 further includes the following steps: S51. Construct an online optimization cost function with the goal of minimizing global energy consumption; S52. Based on the dynamic model and efficiency diagram of the novel pre-stored electro-hydraulic coupled steer-by-wire system, the steering mode switching trajectory of the novel pre-stored electro-hydraulic coupled steer-by-wire system in the next 180 seconds is planned by iterating the online optimization cost function. In step S51, the cost function is optimized online. Energy consumption during dwelling in steering mode Energy loss from accumulators Energy penalty for mode switching Composition, its expression is as follows: (10) in, N This represents the total number of prediction steps. , and These are the weighting coefficients. This represents the equivalent rotational inertia of the electro-hydraulic module on the electric pump. Additional electrical energy required to start the electric hydraulic pump, Obtained through calibration. According to k Offline optimal steering energy consumption diagram based on real-time steering mode, desired steering resistance torque, desired front wheel steering angle increment, and accumulator pressure. Perform a search to obtain the energy consumed while residing in the current mode. P a (0) represents the initial accumulator pressure. P a ( k ) is the first k accumulator pressure at all times ωs ( k )and ω s ( k -1) are respectively the first k and the k Electric pump speed at -1 moment; In step S52, the cost function is based on online optimization. The steering mode switching trajectory is planned using equation (11); (11) in, n for k Selectable steering modes at any time, p for k The optional steering mode at time -1, C n (k) represents the turning mode from time 0. M 0 arrive k Turning mode at any moment M n The cumulative trip cost; In step S52, the novel pre-stored electro-hydraulic coupled steer-by-wire system updates the steering path for the next 180 seconds every 20 seconds and recalculates the steering mode switching trajectory according to the above steps.

[0018] The beneficial effects of this invention are as follows: This invention takes into account the energy-saving requirements of steering in commercial vehicles and proposes a novel pre-stored electro-hydraulic coupled steer-by-wire system. This system has an electric cylinder steering mode, an electric cylinder-accumulator steering mode, and an electric cylinder-accumulator-hydraulic pump steering mode. Based on the navigation steering path, the system plans the steering mode within the next 180 seconds with the goal of meeting the steering power requirements and achieving optimal energy consumption, thereby improving the energy efficiency of the steering system. This invention establishes a dynamic model of a novel pre-stored energy electro-hydraulic coupled steer-by-wire system to characterize the dynamic characteristics of the novel steer-by-wire system. Based on the dynamic model and efficiency diagram, the optimal steering energy consumption cost function for three steering modes is constructed, and the offline optimal steering energy consumption diagram is solved. This invention comprehensively considers the energy consumption of steering mode dwell, energy loss of accumulator and energy penalty of mode switching, and constructs an online optimized cost function to plan the steering mode switching trajectory within the next 180 seconds. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein: Figure 1 This is a schematic diagram of the system structure of the pre-energy storage electro-hydraulic coupling steer-by-wire system and its energy-saving mode switching method of the present invention.

[0020] Figure 2 This is a flowchart of the energy-saving mode switching method of the pre-energy-storage electro-hydraulic coupled steering system and its energy-saving mode switching method of the present invention. Detailed Implementation

[0021] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0022] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0023] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0024] Secondly, the present invention is described in detail with reference to the schematic diagrams. When detailing the embodiments of the present invention, for ease of explanation, the cross-sectional views illustrating the device structure may be partially enlarged, not according to the usual scale. Furthermore, the schematic diagrams are merely examples and should not limit the scope of protection of the present invention. In addition, actual fabrication should include three-dimensional spatial dimensions of length, width, and depth.

[0025] Reference Figures 1-2 A pre-storage electro-hydraulic coupled steer-by-wire system is provided, comprising: Steering module, electric cylinder module, electro-hydraulic module, accumulator module, ECU control module 2 and vehicle sensing module 1; The steering module connects the electric cylinder module and the electro-hydraulic module. The steering module includes a steering tie rod 10, wheels 13, and a steering tie rod sensor 6. Each wheel 13 on both sides is connected to a steering tie rod 10. The radius of one side of each steering tie rod 10 is the same as the inner diameter of the hydraulic cylinder 12 of the electro-hydraulic module, and the internal cavity is connected to the ball screw 8 of the electric cylinder module. The other side of the steering tie rod 10 passes through the hydraulic cylinder 12 and is connected to the wheel 13. One end of the steering tie rod sensor 6 is connected to the steering tie rod 10, and the other end is connected to the hydraulic cylinder 12. The electric cylinder module connects the steering gear module and the ECU control module 2. The electric cylinder module includes: a steering motor 5, a steering motor reducer 9, and a ball screw 8. The steering motor 5 adjusts the torque according to the instructions of the ECU control module 2, and the torque is reduced and increased by the steering motor reducer 9 and then transmitted to the ball screw 8. The ball screw 8 converts the torque into force and acts on the steering tie rod 10, pushing the steering tie rod 10 to move. The electro-hydraulic module is connected to the steering module via hydraulic cylinder 12, to the accumulator module via oil circuit, and to the ECU control module 2 via communication line. The electro-hydraulic module includes: electric pump 3, solenoid directional valve 14, hydraulic cylinder 12, oil circuit 16, and oil reservoir 4. The electric pump 3 adjusts its output torque according to the instructions transmitted by the ECU control module 2 to pump hydraulic oil from the oil reservoir 4 into the oil circuit. The oil circuit 16 is connected to the solenoid directional valve 14, which determines the direction of hydraulic oil flow into the hydraulic cylinder 12, creating a hydraulic differential on both sides of the steering tie rod 10, which pushes the steering tie rod 10 to move. The left hydraulic cylinder pressure sensor 11 and the right hydraulic cylinder pressure sensor 7 are respectively placed in the hydraulic cylinders 12 on both sides. The accumulator module is connected to the electro-hydraulic module via oil circuit 16 and to the ECU control module 2 via communication line. The accumulator module includes: accumulator 17, high-speed switching directional valve 15, and accumulator pressure sensor 18. The high-speed switching directional valve 15 is connected to the oil supply circuit of the electro-hydraulic module. The high-speed switching valve 15 regulates the flow direction and flow rate of hydraulic oil according to the instructions of the ECU control module 2, determining whether the accumulator 17 stores or releases energy. The accumulator pressure sensor 18 is placed inside the accumulator 17. The ECU control module 2 is connected to the electro-hydraulic module, electric cylinder module, accumulator module and vehicle sensing module 1 via communication lines; the vehicle sensing module 1 is connected to the ECU control module 2 via communication lines.

[0026] The ECU control module 2 operates a pre-energy-storage electro-hydraulic coupled steer-by-wire system energy-saving mode switching method, receiving navigation steering path, vehicle status signals, hydraulic cylinder pressure signals, accumulator pressure signals, and steering tie rod signals. After calculation, the ECU control module 2 sends steering mode commands to the electro-hydraulic module, electric cylinder module, and accumulator module. Furthermore, the vehicle-mounted perception module 1 collects real-time maps of the navigation steering path and vehicle status signals for the next 180 seconds and transmits them to the ECU control module 2. The vehicle status signals include: vehicle yaw rate signal, vehicle speed signal, center of gravity sideslip angle signal, and front wheel steering angle signal.

[0027] The energy-saving mode switching method for the pre-storage electro-hydraulic coupled steer-by-wire system includes the following steps: S1. Based on the dynamic model and efficiency diagram of the novel pre-stored electro-hydraulic coupled steer-by-wire system, draw the offline optimal steering energy consumption diagram for three steering modes. Specifically, the steps for creating an offline optimal steering energy consumption map include: S11. Within the maximum steering power range, with the front wheel steering angle resistance torque as the x-axis, the speed as the y-axis, and the accumulator pressure as the z-axis, design the steering system operating point set using the average sampling method; the maximum steering power range in step S11 refers to the maximum power that can be provided by the electric cylinder-accumulator-electric pump steering mode from 0. S12. Optimal steering energy consumption diagram based on steering motor efficiency diagram and steering system operating point set fitting of electric cylinder steering mode; Furthermore, in step S12, the efficiency diagram of the steering motor... The optimal steering energy consumption at each operating point in the electric cylinder steering mode was obtained through testing the steering motor. Obtained from the following formula: (1) in, For the front wheel steering resistance torque, The moment of inertia of the front wheels, For front wheel damping, The front wheel angular velocity, The front wheel angular acceleration, The force output by the steering tie rod. This refers to the gear ratio between the steering tie rod and the front wheels. For the mass of the steering tie rod, For the damping of the steering tie rod, For the speed of the steering tie rod, The acceleration of the steering tie rod, The force output by the electric cylinder. This refers to the transmission ratio between the steering motor and the steering tie rod. This refers to the rotational speed of the steering motor. This refers to the output torque of the steering motor; S13. A dynamic model of a novel pre-energy-storage electro-hydraulic coupled steer-by-wire system based on electric cylinder-accumulator steering mode. With the goal of minimizing the energy consumption of the steering system, the power of the electric cylinder-accumulator steering mode at each working point in the working set is optimized by using a cost function, and the optimal steering energy consumption map of the electric cylinder-accumulator steering mode is fitted by interpolation. Specifically, the dynamic model of the steering gear module of the novel pre-energy-storage electro-hydraulic coupled steer-by-wire system in step S13, under the electric cylinder-accumulator steering mode, is as follows: (2) in, The force output by the hydraulic cylinder. The surface area of ​​one side of the steering tie rod hydraulic cylinder. The pressure on the high-pressure side of the hydraulic cylinder; In step S13, the pressure on the high-pressure side of the hydraulic cylinder in the novel pre-stored electro-hydraulic coupled steer-by-wire system under the electric cylinder-accumulator steering mode... Obtained through the following formula: (3) in, For the oil pressure in the oil supply circuit, The oil pressure inside the accumulator. The flow rate output by the accumulator. The density of the hydraulic oil, It is the acceleration due to gravity. r p The radius of the oil supply pipeline, For the displacement of the steering tie rod, The height difference between the accumulator and the hydraulic cylinder. This refers to the opening area of ​​the high-speed switching valve / directional valve. The flow coefficient of the high-speed switching valve / directional valve. Let be the leakage coefficient of the hydraulic cylinder. The maximum total volume of hydraulic oil that the accumulator's internal space can hold. The pressure when the accumulator is full of hydraulic oil. The rate of change of oil pressure within the accumulator; In step S13, the cost function of the electric cylinder-accumulator steering mode constrained by equations (2) and (3) is shown in equation (4). Based on equation (4), the calculation is performed for each working point in the working set, and the optimal steering energy consumption diagram of the electric cylinder-accumulator steering mode is fitted according to the results. ; (4) in, Energy consumption for electric cylinder-accumulator steering mode. This represents the highest operating efficiency of the electric pump. S14. Dynamic model and efficiency diagram of a novel pre-stored electro-hydraulic coupled steer-by-wire system based on electric cylinder-accumulator-electric pump steering mode. With the goal of minimizing the energy consumption of the steering system, the power of the electric cylinder-accumulator-electric pump steering mode at each working point in the working set is optimized, and the optimal steering energy consumption diagram of the electric cylinder-accumulator-electric pump steering mode is fitted by interpolation method. Specifically, in step S14, the pressure on the high-pressure side of the hydraulic cylinder in the novel pre-energy-storage electro-hydraulic coupled steer-by-wire system under the electric cylinder-accumulator-electric pump steering mode is: (5) in, The flow rate output by the electric pump. This refers to the displacement of the electric pump. The speed of the electric pump. The flow output efficiency of the electric pump. The torque of the electric pump, The torque output efficiency of the electric pump; In step S14, the cost function of the electric cylinder-accumulator-electric pump steering mode constrained by equations (2) and (5) is shown in equation (6). Based on equation (6), calculations are performed for each working point in the working set, and the optimal steering energy consumption diagram of the electric cylinder-accumulator-electric pump steering mode is fitted according to the results. ; (6); in, This is an efficiency diagram for an electric pump, which can be obtained by testing the electric pump.

[0028] S15. Compare the optimal steering energy consumption diagrams of the three steering modes under different working points, select the steering mode with the highest efficiency under the working point power requirements, and thus obtain the offline optimal steering energy consumption diagram with the front wheel steering angle resistance torque as the x-axis, the speed as the y-axis, and the accumulator pressure as the z-axis. Specifically, the comparison method of the optimal steering energy consumption map of the three steering modes at different working points in step S15 is shown in Equation (7). The steering mode with the lowest energy consumption at each working point is retained through the traversal of the working points, and the offline optimal steering energy consumption map is fitted. ; (7) in, , and They refer to the first i The front wheel steering resistance torque, front wheel speed, and accumulator pressure at each operating point; S2. When driving in a straight line, the electric pump operates in the high-efficiency range to pre-store energy in the accumulator until the accumulator is fully charged. In step S2, the ECU control module acquires the signal from the accumulator pressure sensor and, based on the efficiency diagram of the electric pump... Find the most efficient output torque corresponding to the accumulator pressure sensor signal until the accumulator is fully charged; Furthermore, the efficiency diagram of the electric pump in step S2. The capacity can be obtained by testing and calibrating the electric pump; the pre-stored energy capacity in step S2 needs to be calibrated according to the specific vehicle. S3. The vehicle sensing module acquires the steering path and real-time vehicle yaw angle, vehicle speed, center of gravity sideslip angle and front wheel angle signals within the next 180 seconds. The tie rod displacement sensor, hydraulic cylinder pressure sensor and accumulator pressure sensor collect the steering tie rod displacement signal, the pressure difference signal between the oil chambers on both sides of the hydraulic cylinder and the pressure signal in the accumulator in real time. Specifically, in step S3, the turning path for the next 180 seconds is transmitted from the navigation system to the vehicle perception module; the vehicle perception module updates the turning path every 20 seconds to obtain the new turning path for the next 180 seconds. S4. The ECU control module receives the signal from step S3 and calculates the expected resistance torque of the steering system within the next 180 seconds based on the vehicle kinematics model and dynamics model and the collected navigation steering path. Specifically, step S4 also includes the following steps: S41. Based on the vehicle kinematics model, calculate the vehicle's yaw rate trajectory and center of gravity sideslip trajectory within the next 180 seconds according to the navigation and steering path within the next 180 seconds. S42. Using a vehicle dynamics model, track the vehicle's yaw rate trajectory and center of gravity sideslip trajectory within the next 180 seconds to predict the trajectory of the steering resistance torque generated by the front tires. In step S41, the desired yaw rate trajectory and the desired centroid sideslip angle trajectory are obtained by solving the navigation steering path within the next 180s based on equation (8). (8) in, k The first in 180 seconds k time, For the desired yaw rate, To determine the desired centroid sideslip angle, This represents the longitudinal position of the navigation turning path. This represents the lateral position of the navigation turning path. for k The longitudinal position of the vehicle at any given time. This refers to the front wheelbase. Rear wheelbase For the front wheel lateral stiffness, For rear wheel lateral stiffness, Wheelbase For vehicle quality, For vehicle speed; In step S42, based on the expected yaw rate trajectory and the expected center of gravity sideslip angle trajectory, the trajectory of the steering resistance torque generated by the front tires is predicted by equation (9); (9) in, To achieve the desired front wheel steering angle, To achieve the desired steering resistance torque, This refers to tire trail. S5. Calculate the energy-optimal steering mode switching trajectory based on the offline optimal steering energy consumption map and the online optimization cost function; Specifically, step S5 also includes the following steps: S51. Construct an online optimization cost function with the goal of minimizing global energy consumption; S52. Based on the dynamic model and efficiency diagram of the novel pre-stored electro-hydraulic coupled steer-by-wire system, the steering mode switching trajectory of the novel pre-stored electro-hydraulic coupled steer-by-wire system in the next 180 seconds is planned by iterating the online optimization cost function. In step S51, the cost function is optimized online. Energy consumption during dwelling in steering mode Energy loss from accumulators Energy penalty for mode switching Composition, its expression is as follows: (10) in, N This represents the total number of prediction steps. , and These are the weighting coefficients. This represents the equivalent rotational inertia of the electro-hydraulic module on the electric pump. Additional electrical energy required to start the electric hydraulic pump, Obtained through calibration. According to k Offline optimal steering energy consumption diagram based on real-time steering mode, desired steering resistance torque, desired front wheel steering angle increment, and accumulator pressure. Perform a search to obtain the energy consumed while residing in the current mode. P a (0) represents the initial accumulator pressure. P a ( k ) is the first k accumulator pressure at all times ω s ( k )and ω s ( k -1) are respectively the first k and the k Electric pump speed at -1 moment; In step S52, the cost function is optimized online. The steering mode switching trajectory is planned using equation (11); (11) in, n for k Selectable steering modes at any time, p for k The optional steering mode at time -1, C n (k) represents the turning mode from time 0. M0 arrive k Turning mode at any moment M n The cumulative travel cost; In step S52, the new pre-stored electro-hydraulic coupled steer-by-wire system updates the steering path for the next 180 seconds every 20 seconds and recalculates the steering mode switching trajectory according to the above steps.

[0029] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. 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 be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A pre-stored energy electro-hydraulic coupled steering-by-wire system, characterized in that, include: Steering module, electric cylinder module, electro-hydraulic module, accumulator module, ECU control module (2) and vehicle sensing module (1); The steering module connects the electric cylinder module and the electric hydraulic module. The steering module includes a steering tie rod (10), a wheel (13), and a steering tie rod sensor (6). Each wheel (13) on both sides is connected to a steering tie rod (10). The radius of one side of each steering tie rod (10) is consistent with the inner diameter of the hydraulic cylinder (12) of the electric hydraulic module, and the internal cavity is connected to the ball screw (8) of the electric cylinder module. The other side of the steering tie rod (10) passes through the hydraulic cylinder (12) and is connected to the wheel (13). One end of the steering tie rod sensor (6) is connected to the steering tie rod (10), and the other end is connected to the hydraulic cylinder (12). The electric cylinder module is connected to the steering module and the ECU control module (2). The electric cylinder module includes: a steering motor (5), a steering motor reducer (9) and a ball screw (8). The steering motor (5) adjusts the torque according to the instructions of the ECU control module (2), and the torque is reduced and increased by the steering motor reducer (9) and transmitted to the ball screw (8). The ball screw (8) converts the torque into force and acts on the steering tie rod (10) to push the steering tie rod (10) to move. The electro-hydraulic module is connected to the steering module via a hydraulic cylinder (12), to the accumulator module via an oil circuit, and to the ECU control module (2) via a communication line. The electro-hydraulic module includes: an electric pump (3), an electromagnetic reversing valve (14), a hydraulic cylinder (12), an oil circuit (16), and an oil reservoir (4). The electric pump (3) adjusts its output torque according to the instructions transmitted by the ECU control module (2) to pump hydraulic oil from the oil reservoir (4) into the oil circuit. The oil circuit (16) is connected to the electromagnetic reversing valve (14). The electromagnetic reversing valve (14) determines the direction of hydraulic oil flow into the hydraulic cylinder (12), forming a hydraulic differential on both sides of the steering tie rod (10), which pushes the steering tie rod (10) to move. The pressure sensor (11) of the left hydraulic cylinder and the pressure sensor (7) of the right hydraulic cylinder are respectively placed in the hydraulic cylinders (12) on both sides. The accumulator module is connected to the electro-hydraulic module via an oil circuit (16) and to the ECU control module (2) via a communication line. The accumulator module includes: an accumulator (17), a high-speed switching directional valve (15), and an accumulator pressure sensor (18). The high-speed switching directional valve (15) is connected to the oil supply circuit of the electro-hydraulic module. The high-speed switching valve (15) regulates the flow direction and flow rate of the hydraulic oil according to the instructions of the ECU control module (2) to determine whether the accumulator (17) stores or releases energy. The accumulator pressure sensor (18) is placed inside the accumulator (17). The ECU control module (2) is connected to the electro-hydraulic module, electric cylinder module, accumulator module and vehicle sensing module (1) via a communication line; the vehicle sensing module (1) is connected to the ECU control module (2) via a communication line.

2. The pre-stored energy electro-hydraulic coupled steering-by-wire system according to claim 1, characterized in that: The ECU control module (2) runs the energy-saving mode switching method of the pre-stored electro-hydraulic coupled steer-by-wire system, and receives navigation steering path, vehicle status signal, hydraulic cylinder pressure signal, accumulator pressure signal and steering tie rod signal; after calculation, the ECU control module (2) sends the steering mode command to the electro-hydraulic module, electric cylinder module and accumulator module.

3. The pre-stored energy electro-hydraulic coupled steer-by-wire system according to claim 2, characterized in that: The vehicle-mounted sensing module (1) collects real-time maps of the navigation and steering path and vehicle status signals within the next 180 seconds and transmits them to the ECU control module (2). The vehicle status signals include: vehicle yaw rate signal, vehicle speed signal, center of gravity sideslip angle signal and front wheel steering angle signal.

4. A pre-stored energy electro-hydraulic coupled steering-by-wire system according to any one of claims 1-3, characterized in that: The method for switching energy-saving modes in a pre-storage electro-hydraulic coupled steer-by-wire system includes the following steps: S1. Based on the dynamic model and efficiency diagram of the novel pre-stored electro-hydraulic coupled steer-by-wire system, draw the offline optimal steering energy consumption diagram for three steering modes. S2. When driving in a straight line, the electric pump operates in the high-efficiency range to pre-store energy in the accumulator until the accumulator is fully charged. S3. The vehicle sensing module acquires the steering path and real-time vehicle yaw angle, vehicle speed, center of gravity sideslip angle and front wheel angle signals within the next 180 seconds. The tie rod displacement sensor, hydraulic cylinder pressure sensor and accumulator pressure sensor collect the steering tie rod displacement signal, the pressure difference signal between the oil chambers on both sides of the hydraulic cylinder and the pressure signal in the accumulator in real time. S4. The ECU control module receives the signal from step S3 and calculates the expected resistance torque of the steering system within the next 180 seconds based on the vehicle kinematics model and dynamics model and the collected navigation steering path. S5. Calculate the energy-optimal steering mode switching trajectory based on the offline optimal steering energy consumption map and the online optimized cost function.

5. The energy-saving mode switching method for the pre-energy-storage electro-hydraulic coupled steering-by-wire system according to claim 4, characterized in that: The specific steps for creating the offline optimal steering energy consumption map include: S11. Within the maximum steering power range, with the front wheel steering angle resistance torque as the x-axis, the speed as the y-axis, and the accumulator pressure as the z-axis, design the steering system operating point set using the average sampling method; S12. Optimal steering energy consumption diagram based on steering motor efficiency diagram and steering system operating point set fitting of electric cylinder steering mode; S13. A dynamic model of a novel pre-energy-storage electro-hydraulic coupled steer-by-wire system based on electric cylinder-accumulator steering mode. With the goal of minimizing the energy consumption of the steering system, the power of the electric cylinder-accumulator steering mode at each working point in the working set is optimized by using a cost function, and the optimal steering energy consumption map of the electric cylinder-accumulator steering mode is fitted by interpolation. S14. Dynamic model and efficiency diagram of a novel pre-stored electro-hydraulic coupled steer-by-wire system based on electric cylinder-accumulator-electric pump steering mode. With the goal of minimizing the energy consumption of the steering system, the power of the electric cylinder-accumulator-electric pump steering mode at each working point in the working set is optimized, and the optimal steering energy consumption diagram of the electric cylinder-accumulator-electric pump steering mode is fitted by interpolation method. S15. Compare the optimal steering energy consumption diagrams of the three steering modes under different working points, select the steering mode with the highest efficiency under the working point power requirements, and thus obtain the offline optimal steering energy consumption diagram with the front wheel steering angle resistance torque as the x-axis, the speed as the y-axis, and the accumulator pressure as the z-axis.

6. The energy-saving mode switching method for the pre-stored energy electro-hydraulic coupled steer-by-wire system according to claim 5, characterized in that: The efficiency diagram of the steering motor in step S12 The optimal steering energy consumption at each operating point in the electric cylinder steering mode was obtained through testing the steering motor. Obtained from the following formula: (1)， in, For the front wheel steering resistance torque, The moment of inertia of the front wheels, For front wheel damping, The front wheel angular velocity, The front wheel angular acceleration, The force output by the steering tie rod. This refers to the gear ratio between the steering tie rod and the front wheels. For the mass of the steering tie rod, For the damping of the steering tie rod, For the speed of the steering tie rod, The acceleration of the steering tie rod, The force output by the electric cylinder. This refers to the transmission ratio between the steering motor and the steering tie rod. This refers to the rotational speed of the steering motor. This is the output torque of the steering motor.

7. The energy-saving mode switching method for the pre-storage electro-hydraulic coupled steer-by-wire system according to claim 5, characterized in that: The dynamic model of the steering module of the novel pre-energy-storage electro-hydraulic coupled steer-by-wire system in step S13, under the electric cylinder-accumulator steering mode, is as follows: (2)， in, The force output by the hydraulic cylinder. The surface area of ​​one side of the steering tie rod hydraulic cylinder. The pressure on the high-pressure side of the hydraulic cylinder; In step S13, the pressure on the high-pressure side of the hydraulic cylinder of the novel pre-stored electro-hydraulic coupled wire-controlled steering system in the electric cylinder-accumulator steering mode... Obtained through the following formula: (3)， in, For the oil pressure in the oil supply circuit, The oil pressure inside the accumulator. The flow rate output by the energy storage device. The density of the hydraulic oil, It is the acceleration due to gravity. r p The radius of the oil supply pipeline, For the displacement of the steering tie rod, The height difference between the accumulator and the hydraulic cylinder. This refers to the opening area of ​​the high-speed switching valve / directional valve. The flow coefficient of the high-speed switching valve / directional valve. Let be the leakage coefficient of the hydraulic cylinder. The maximum total volume of hydraulic oil that the accumulator's internal space can hold. The pressure when the accumulator is full of hydraulic oil. The rate of change of oil pressure within the accumulator; In step S13, the cost function of the electric cylinder-accumulator steering mode constrained by equations (2) and (3) is shown in equation (4). Based on equation (4), calculations are performed for each working point in the working set, and the optimal steering energy consumption diagram of the electric cylinder-accumulator steering mode is fitted according to the results. ; (4) in, Energy consumption for electric cylinder-accumulator steering mode. This represents the highest operating efficiency of the electric pump.

8. The energy-saving mode switching method for the pre-stored energy electro-hydraulic coupled steer-by-wire system according to claim 5, characterized in that: In step S14, the pressure on the high-pressure side of the hydraulic cylinder in the novel pre-energy-storage electro-hydraulic coupled wire-controlled steering system under the electric cylinder-accumulator-electric pump steering mode is: (5) in, The flow rate output by the electric pump. This refers to the displacement of the electric pump. The speed of the electric pump. The flow output efficiency of the electric pump. The torque of the electric pump, The torque output efficiency of the electric pump; In step S14, the cost function of the electric cylinder-accumulator-electric pump steering mode constrained by equations (2) and (5) is shown in equation (6). Based on equation (6), calculations are performed for each working point in the working set, and the optimal steering energy consumption diagram of the electric cylinder-accumulator-electric pump steering mode is fitted according to the results. ; (6) in, This is an efficiency diagram for an electric pump, which can be obtained by testing the electric pump. The comparison method of the optimal steering energy consumption map of the three steering modes at different working points in step S15 is shown in Equation (7). The steering mode with the lowest energy consumption at each working point is retained through the traversal of the working points, and the offline optimal steering energy consumption map is fitted. ; (7) in, , and They refer to the first i The front wheel steering resistance torque, front wheel speed, and accumulator pressure at each operating point.

9. The energy-saving mode switching method for the pre-energy-storage electro-hydraulic coupled steer-by-wire system according to claim 5, characterized in that: Step S4 also includes the following steps: S41. Based on the vehicle kinematics model, calculate the vehicle's yaw rate trajectory and center of gravity sideslip trajectory within the next 180 seconds according to the navigation and steering path within the next 180 seconds. S42. Using a vehicle dynamics model, track the vehicle's yaw rate trajectory and center of gravity sideslip trajectory within the next 180 seconds to predict the trajectory of the steering resistance torque generated by the front tires. In step S41, the desired yaw rate trajectory and the desired centroid sideslip angle trajectory are obtained by solving the navigation turning path within the next 180s based on equation (8). (8) in, k The first in 180 seconds k time, For the desired yaw rate, To determine the desired centroid sideslip angle, This represents the longitudinal position of the navigation turning path. This represents the lateral position of the navigation turning path. for k The longitudinal position of the vehicle at any given time. This refers to the front wheelbase. Rear wheelbase For the front wheel lateral stiffness, For rear wheel lateral stiffness, Wheelbase For vehicle quality, For vehicle speed; In step S42, the trajectory of the steering resistance torque generated by the front tires is predicted by equation (9) based on the expected yaw rate trajectory and the expected center of gravity sideslip angle trajectory. (9) in, To achieve the desired front wheel steering angle, To achieve the desired steering resistance torque, This refers to tire trail.

10. The energy-saving mode switching method for the pre-storage electro-hydraulic coupled steer-by-wire system according to claim 5, characterized in that: Step S5 also includes the following steps: S51. Construct an online optimization cost function with the goal of minimizing global energy consumption; S52. Based on the dynamic model and efficiency diagram of the novel pre-stored electro-hydraulic coupled steer-by-wire system, the steering mode switching trajectory of the novel pre-stored electro-hydraulic coupled steer-by-wire system in the next 180 seconds is planned by iterating the online optimization cost function. In step S51, the cost function is optimized online. Energy consumption during dwelling in steering mode Energy loss from accumulators Energy penalty for mode switching Composition, its expression is as follows: (10) in, N This represents the total number of prediction steps. , and These are the weighting coefficients. This represents the equivalent rotational inertia of the electro-hydraulic module on the electric pump. Additional electrical energy required to start the electric hydraulic pump, Obtained through calibration. According to k Offline optimal steering energy consumption diagram based on real-time steering mode, desired steering resistance torque, desired front wheel steering angle increment, and accumulator pressure. Perform a search to obtain the energy consumed while residing in the current mode. P a (0) represents the initial accumulator pressure. P a ( k ) is the first k accumulator pressure at all times ω s ( k )and ω s ( k -1) are respectively the first k and the k Electric pump speed at -1 moment; In step S52, the cost function is based on online optimization. The steering mode switching trajectory is planned using equation (11); (11) in, n for k Selectable steering modes at any time, p for k The optional steering mode at time -1, C n (k) represents the turning mode from time 0. M 0 arrive k Turning mode at any moment M n The cumulative trip cost; In step S52, the novel pre-stored electro-hydraulic coupled steer-by-wire system updates the steering path for the next 180 seconds every 20 seconds and recalculates the steering mode switching trajectory according to the above steps.

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