A high-fidelity modeling method for an electric power steering system

Abstract

The application discloses a high-fidelity modeling method of an electric power steering system, and belongs to the automobile field, and comprises the following steps: step 1: oscillation type angle input is carried out on a steering wheel at the longitudinal speed of 0 km / h, 10 km / h, 20 km / h, 40 km / h, 60 km / h, 80 km / h, 100 km / h and 120 km / h of an actual vehicle, and the input form of the oscillation type angle input of the steering wheel is a sine wave; the input frequency of the steering wheel is 0.2 Hz; the steering characteristic identification module and the steering characteristic control module are designed; the steering force feeling characteristic of the power assistance phase of the actual vehicle and the return speed characteristic of the hands-off phase can be accurately identified and controlled; the problem that other electric power steering system models cannot accurately express the steering characteristics of the power assistance phase and the hands-off phase of the vehicle is solved; the application has high fidelity; simulation can obtain consistent steering characteristics with the actual vehicle.

Description

Technical Field

[0001] This invention relates to the automotive field, and in particular to a high-fidelity modeling method for electric power steering systems. Background Technology

[0002] In recent years, electric power steering (EPS) systems have been widely used in automobiles. A good electric power steering system should perform well in terms of steering sensitivity, stability, accuracy, and comfort.

[0003] Invention patent CN113255153A discloses a simulation method, device, and storage medium for an electric power steering system in automobiles. The method involves building a complete vehicle model in the ADASM application and an electric power steering system model in the Amesim application. The complete vehicle model is constructed based on the physical structure of the vehicle. The complete vehicle model and the electric power steering system model are associated in the Amesim application. The electric power steering system of the automobile is simulated based on the complete vehicle model and the electric power steering system model. However, this modeling method cannot reflect the steering force feel of the electric power steering system. Invention patent CN114357825A discloses a finite element modeling method for an electric power steering system. This method involves individual modeling of key components of the electric power steering system and connecting these components to obtain a finite element model of the electric power steering system. The correctness of the finite element model is determined by the modal analysis results of the individual steering system components. Based on the model verification, the parameters of the finite element model of the electric power steering system are calibrated. However, this modeling method cannot accurately model any vehicle, and the simulation results deviate significantly from the steering characteristics of the actual vehicle. It cannot accurately reflect the steering force of the vehicle and cannot simulate the return-to-center speed characteristics of an actual vehicle when the steering wheel is released.

[0004] To address the above issues, this invention adopts a different approach from previous electric power steering (ESP) system modeling methods, proposing a high-fidelity modeling method for ESP systems. After conducting real-vehicle tests on the target vehicle and collecting and processing data, the correspondence between the driver's steering input torque and the steering wheel angle at different longitudinal speeds is identified, as well as the steering wheel return speed when the vehicle is released from the steering wheel in a stable state under a certain lateral acceleration. These characteristics—namely, the steering feel characteristics of the power steering phase and the return speed characteristics of the release phase—are used as the control targets for the ESP system model. Compared to existing modeling methods, this method offers high fidelity and wide applicability, enabling high-fidelity modeling of the ESP system of any vehicle, accurately representing its steering feel characteristics of the power steering phase and the return speed characteristics of the release phase, and exhibiting high consistency with actual vehicles. By identifying the steering force characteristics of the power steering phase and the return-to-center speed characteristics of the handbrake phase in a real vehicle, these are set as the control targets for the model's steering characteristics. The steering motion intensity of the simulated target vehicle, i.e., the desired steering motion intensity, is determined by the steering input torque. The desired pinion angle is determined by comparing the actual and desired steering motion intensity with the steady-state inverse characteristics of the vehicle's chassis dynamics. The equivalent steering resistance torque at the pinion is determined by comparing the actual and desired pinion angle with the steady-state inverse characteristics of the steering system. Subtracting the steering wheel torque from the equivalent steering resistance torque at the pinion yields the target assist of the EPS system. The steering force characteristic curves of the power steering phase and the return-to-center speed characteristic curves of the handbrake phase in a real vehicle are used as the control targets for the simulation model in the power steering and handbrake phases. This control strategy and modeling method ensure that the steering characteristics of the power steering and handbrake phases in the model have a high degree of realism compared to the actual vehicle. Summary of the Invention

[0005] The purpose of this invention is to provide a highly realistic modeling method for electric power steering systems to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A high-fidelity modeling method for an electric power steering system includes the following steps:

[0008] Step 1: Apply oscillating steering wheel angle input to the actual vehicle at longitudinal speeds of 0 km / h, 10 km / h, 20 km / h, 40 km / h, 60 km / h, 80 km / h, 100 km / h, and 120 km / h. The input form of the oscillating steering wheel angle input is a sine wave. The steering wheel input frequency is 0.2 Hz. The steering wheel is rotated until the lateral acceleration exceeds 0.65g or the maximum lateral acceleration achievable due to power limitations, or until the vehicle becomes unstable. Collect steering wheel input torque and steering wheel angle information at different longitudinal speeds.

[0009] Step 2: With the actual vehicle traveling at longitudinal speeds of 0 km / h, 10 km / h, 20 km / h, 40 km / h, 60 km / h, 80 km / h, 100 km / h, and 120 km / h, turn the steering wheel until the lateral acceleration of the car reaches a stable state of 0.1g, 0.2g, 0.3g, 0.4g, 0.5g, 0.6g, and 0.7g, respectively. Then, remove the steering input torque and return the steering wheel to the center area. Collect data on the steering wheel return speed under different longitudinal speeds and different steady-state lateral accelerations.

[0010] Step 3: Process the experimental data obtained in Steps 1 and 2 under different working conditions using the least squares method to obtain the boundary curves of the steering force characteristic field of the actual vehicle at different longitudinal speeds and the return-to-center speed curves at different steady-state lateral accelerations. Extract the steering wheel angles at 0 N.m, 0.25 Nm, 0.5 Nm, 0.75 Nm, 1 N.m, 1.25 Nm, 1.5 Nm, 1.75 Nm, 2 N.m, 2.25 Nm, and 2.5 Nm. Correspondingly, the relationship between the longitudinal speed steering input torque and the steering wheel angle at 0 km / h, 10 km / h, 20 km / h, 40 km / h, 60 km / h, 80 km / h, 100 km / h, and 120 km / h, and the return-to-center speed curves at different steady-state lateral accelerations can be obtained, i.e., the steering characteristics of the power assist phase and the hands-off phase at different longitudinal speeds, resulting in the steering characteristic curves.

[0011] Step 4: In the electric power steering system model, the steering characteristic curves of the power steering phase and the let-off phase at different longitudinal speeds of the actual vehicle are used as the control target to obtain a highly realistic electric power steering system model.

[0012] Compared with the prior art, the beneficial effects of the present invention are:

[0013] 1. This invention solves the problem that a single electric power steering system model cannot model the electric power steering system of any vehicle. It eliminates the need for remodeling due to differences in the electric power steering units of different vehicles. The electric power steering system model of this invention can model the electric power steering system of any vehicle.

[0014] 2. By designing a vehicle steering characteristic identification module and a steering characteristic control module, this invention can accurately identify and control the steering force characteristics of the power steering phase and the return speed characteristics of the let-off phase of a real vehicle. This solves the problem that other electric power steering system models cannot accurately express the steering characteristics of the power steering phase and the let-off phase of a vehicle. It has a high degree of realism, and the simulation can obtain steering characteristics consistent with those of the real vehicle. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the high-fidelity modeling implementation scheme described in this invention.

[0016] Figure 2 This is a diagram showing the steering force characteristics of a real vehicle's power steering system.

[0017] Figure 3 This is a diagram showing the speed characteristics of the vehicle's hands-off return phase. Detailed Implementation

[0018] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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.

[0019] like Figure 1-3 As shown, a high-fidelity modeling method for an electric power steering system consists of a real vehicle power steering phase steering force feel characteristic identification module, a real vehicle hand-off phase return-to-center speed characteristic identification module, a power steering phase steering force feel characteristic control module, and a hand-off phase return-to-center speed characteristic control module. A schematic diagram of the scheme is shown below. Figure 1 As shown. The real-vehicle power steering force feel characteristic identification module obtains the steering wheel angle under different longitudinal speeds and different driver steering input torques through experiments. After processing the experimental data using the least squares method, the real-vehicle power steering force feel characteristic curve is obtained. The real-vehicle release-phase return-to-center speed characteristic identification module obtains the return-to-center speed curve under different longitudinal speeds and different steady-state lateral accelerations through experiments. After processing the experimental data using the least squares method, the real-vehicle release-phase return-to-center speed characteristic curve is obtained. The power steering force feel characteristic control module and the release-phase return-to-center speed characteristic control module use the steering characteristic curves of the real vehicle as control targets in the model. The working process of this invention applied to the ASCL driving simulator at Jilin University is as follows:

[0020] Step 1: Apply oscillating steering wheel input at longitudinal speeds of 0 km / h, 10 km / h, 20 km / h, 40 km / h, 60 km / h, 80 km / h, 100 km / h, and 120 km / h using a sine wave input frequency of 0.2 Hz. Rotate the steering wheel until the lateral acceleration exceeds 0.65g (or the maximum lateral acceleration achievable due to power limitations, or until the vehicle becomes unstable). Collect steering wheel input torque and steering wheel angle information at different longitudinal speeds.

[0021] Step Two: At actual vehicle speeds of 0 km / h, 10 km / h, 20 km / h, 40 km / h, 60 km / h, 80 km / h, 100 km / h, and 120 km / h, rotate the steering wheel until the vehicle's lateral acceleration reaches a stable state of 0.1g, 0.2g, 0.3g, 0.4g, 0.5g, 0.6g, and 0.7g, respectively. Then, remove the steering input torque, returning the steering wheel to the center zone. Collect data on the steering wheel return speed at different longitudinal speeds and steady-state lateral accelerations.

[0022] Step 3: The experimental data obtained in Steps 1 and 2 under different operating conditions are processed using the least squares method to fit the boundary curves of the steering force characteristic field of the actual vehicle at different longitudinal speeds and the return-to-center speed curves under different steady-state lateral accelerations. Steering wheel angles at 0 N·m, 0.25 N·m, 0.5 N·m, 0.75 N·m, 1 N·m, 1.25 N·m, 1.5 N·m, 1.75 N·m, 2 N·m, 2.25 N·m, and 2.5 N·m are extracted. Correspondingly, the relationship between the longitudinal speed steering input torque and steering wheel angle at 0 km / h, 10 km / h, 20 km / h, 40 km / h, 60 km / h, 80 km / h, 100 km / h, and 120 km / h, and the return-to-center speed curves under different steady-state lateral accelerations are obtained, i.e., the steering characteristics in the power assist and release phases at different longitudinal speeds. The resulting steering characteristic curves are shown below. Figure 2 As shown.

[0023] Step 3: In the electric power steering system model, the steering characteristic curves of the assist phase and the let-off phase at different longitudinal speeds of the actual vehicle are used as control targets to obtain a highly realistic electric power steering system model. The steering characteristics at different vehicle speeds obtained from the simulation are in good agreement with the steering characteristics of the actual vehicle.

[0024] The symbol parameters used in this invention are shown in Table 1;

[0025] Table 1: Symbol Parameter Table.

[0026]

[0027]

[0028] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0029] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A high-fidelity modeling method for an electric power steering system, characterized in that, Includes the following steps: Step 1: Perform oscillating steering wheel input at actual vehicle longitudinal speeds of 0km / h, 10km / h, 20km / h, 40km / h, 60km / h, 80km / h, 100km / h, and 120km / h, and collect steering wheel input torque and steering wheel angle information at different longitudinal speeds; Step 2: At actual vehicle speeds of 0km / h, 10km / h, 20km / h, 40km / h, 60km / h, 80km / h, 100km / h, and 120km / h, turn the steering wheel until the vehicle's lateral acceleration reaches a stable state of 0.1g, 0.2g, 0.3g, 0.4g, 0.5g, 0.6g, and 0.7g, respectively. Then, remove the steering input torque and return the steering wheel to the center zone. Collect data on the steering wheel return speed at different longitudinal speeds and different steady-state lateral accelerations. Step 3: Use the least squares method to process the experimental data obtained in Step 1 and Step 2 under different working conditions, and fit the boundary curves of the steering force field of the actual vehicle at different longitudinal speeds and the return speed curves at different steady-state lateral accelerations. extract Steering wheel angles at 0 N.m, 0.25 Nm, 0.5 Nm, 0.75 Nm, 1 N.m, 1.25 Nm, 1.5 Nm, 1.75 Nm, 2 N.m, 2.25 Nm, and 2.5 Nm were obtained; the correspondence between longitudinal speed steering input torque and steering wheel angle at 0 km / h, 10 km / h, 20 km / h, 40 km / h, 60 km / h, 80 km / h, 100 km / h, and 120 km / h was obtained, along with the return-to-center speed curves under different steady-state lateral accelerations, i.e., the steering characteristics of the power assist phase and the hands-off phase at different longitudinal speeds, thus obtaining the steering characteristic curves; Step 4: In the electric power steering system model, the steering characteristic curves of the power steering phase and the let-off phase at different longitudinal speeds of the actual vehicle are used as the control target to obtain a highly realistic electric power steering system model.

2. A high-fidelity modeling method for an electric power steering system according to claim 1, characterized in that, The electric power steering system consists of a real vehicle power steering force feel characteristic identification module, a real vehicle let-off phase return speed characteristic identification module, a power steering force feel characteristic control module, and a let-off phase return speed characteristic control module.

3. A high-fidelity modeling method for an electric power steering system according to claim 2, characterized in that, The real vehicle power steering force feedback characteristic identification module obtains the steering wheel angle under different driver steering input torques at different longitudinal speeds of the car through experiments, and then processes the experimental data using the least squares method to obtain the real vehicle power steering force feedback characteristic curve.

4. A high-fidelity modeling method for an electric power steering system according to claim 2, characterized in that, The real vehicle let-off phase return speed characteristic identification module obtains the return speed curves of the let-off phase under different longitudinal speeds and different steady-state lateral accelerations of the vehicle through experiments. After processing the experimental data using the least squares method, the real vehicle let-off phase return speed characteristic curve is obtained.

5. A high-fidelity modeling method for an electric power steering system according to claim 2, characterized in that, The power steering force feedback characteristic control module and the hand-off steering return speed characteristic control module use the steering characteristic curve of the actual vehicle as the control target in the model.

6. A high-fidelity modeling method for an electric power steering system according to claim 1, characterized in that, In step 1, the input form for the oscillating steering wheel angle input is a sine wave.

7. A high-fidelity modeling method for an electric power steering system according to claim 6, characterized in that, The steering wheel input frequency is 0.2Hz. The steering wheel is turned until the lateral acceleration is greater than 0.65g or the maximum lateral acceleration that can be achieved due to power limitations, or until the vehicle becomes unstable.

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