Method and system for acquiring rack force of SBW vehicle

Abstract

The invention relates to a method and a system for acquiring rack force of an SBW vehicle. The method comprises the steps that S10, according to operation parameters of a vehicle steering motor, whether the vehicle meets the state conditions that wheels are in a steering static state and friction force is dominant or not is judged; s20, responding to the condition that the state is not met, and adopting a first physical model; S21, obtaining rack thrust F1 applied to a rack by a steering motor and friction force f of the system; step S22, acquiring rack force F2 based on the rack thrust F1, the friction force f and the mass m and the acceleration a of the rack; s30, responding to the condition meeting the state, and adopting a second physical model; S31, obtaining the front axle transverse force Fy < front > of the front axle of the wheel; and step S32, acquiring rack force F2 based on the front axle transverse force Fy front and the running speed V of the vehicle. The actual working condition of the vehicle is considered, different physical models are adopted to calculate the rack force, reliability is high, and additional sensors are not needed.

Description

Technical Field

[0001] This invention relates to the field of SBW vehicle technology, and in particular to a method and system for obtaining rack force in SBW vehicles. Background Technology

[0002] Electric power steering (Steer-by-Wire, SBW) refers to a system where there is no direct mechanical connection between the steering wheel and the wheels; instead, the steering wheel controls the wheels via cables. For example... Figure 1 As shown, the steering system of the SBW vehicle includes the HWA system and the RWA system. The HWA system is the Hand Wheel Actuator, and the RWA system is the Road Wheel Actuator.

[0003] In traditional vehicles, because the steering wheel and wheels are connected by a mechanical structure, road information can be directly transmitted to the steering wheel through the connection between the wheels and mechanical components.

[0004] In SBW vehicles, because there is no mechanical connection or constraint between the steering wheel and the wheels, road information cannot be directly fed back to the steering wheel. In this case, the HWA system needs to accurately simulate road feel information. In simulation methods, the most important signal received by the HWA is the rack force provided by the RWA, which is the frictional force exerted on the wheel by the ground as it rotates. Therefore, in order to accurately simulate the steering torque felt by the steering wheel, the RWA system needs to accurately estimate the magnitude of the rack force.

[0005] In related technologies, rack force measurement mainly relies on rack force sensors, rack deformation sensors, or theoretically modeled state observers. However, while rack force sensors are direct and effective, they add extra cost; when using rack deformation sensors, the variable and non-constant elastic coefficient of the rack affects measurement accuracy, making it difficult to accurately obtain rack force; and model-based state observation methods are often too theoretical, making it difficult to achieve an ideal balance between accuracy and practicality in real-world applications. Therefore, providing an economical, practical, accurate, and reliable rack force estimation method has become a core challenge that urgently needs to be overcome to improve the driving experience of SBW vehicles. Summary of the Invention

[0006] To overcome the problems existing in related technologies, this disclosure provides a method and system for obtaining rack force of SBW vehicles.

[0007] According to the first aspect of the embodiment of the present disclosure, a rack force acquisition method of a SBW vehicle comprises the following steps: step S10: determining whether the vehicle meets a state condition that the wheels are in steering static and the friction force is dominant according to the operating parameters of the vehicle steering motor; step S20: in response to not meeting the state condition, a first physical model is used, comprising: step S21: acquiring the rack pushing force F1 applied by the steering motor on the rack and the friction force f of the system; step S22: acquiring the rack force F2 based on the rack pushing force F1, the friction force f, and the mass m and acceleration a of the rack; step S30: in response to meeting the state condition, a second physical model is used, comprising: step S31: acquiring the front axle lateral force Fy of the front axle of the vehicle 前 ; and step S32: acquiring the rack force F2 based on the front axle lateral force Fy 前 and the driving speed V of the vehicle.

[0008] In some embodiments, in the step S10, the operating parameters of the steering motor include the absolute value of the motor torque T, the absolute value of the motor rotation acceleration a, and the absolute value of the motor speed v, wherein when the absolute value of the motor torque T, the absolute value of the motor rotation acceleration a, and the absolute value of the motor speed v are all less than the corresponding limits, the vehicle is in the state that the wheels are in steering static and the friction force is dominant, meeting the state condition.

[0009] In some embodiments, in the step S21, the rack pushing force F1 applied by the steering motor on the rack is calculated based on the motor torque T, the motor moment of inertia J, and the motor rotation acceleration a and the equivalent force arm d of the motor to the rack.

[0010] In some embodiments, in the step S21, the friction force f of the system comprises: a first friction force f1, which is acquired by looking up a table after inputting the motor torque T and the rack position in the two-dimensional table; and a second friction force f2, which is acquired by looking up a table after inputting the motor speed v and the rack position in the two-dimensional table.

[0011] In some embodiments, the direction of the friction force f is determined based on the motor speed v, and when the direction of the friction force f changes, gradient smoothing processing is performed on the friction force f through a gradient filtering mechanism.

[0012] In some embodiments, in response to the motor speed v being greater than a first limit, the direction symbol of the friction force f is positive; in response to the motor speed v being less than a second limit, the direction symbol of the friction force f is negative; and in response to the motor speed v being greater than the second limit and less than the first limit, the direction of the friction force f remains the previous direction; wherein the motor drives the wheels to rotate counterclockwise, the direction symbol of the motor speed v is positive, the first limit is positive, the motor drives the wheels to rotate clockwise, the direction symbol of the motor speed v is negative, and the second limit is negative.

[0013] In some embodiments, in the step S32, the first proportional coefficient is obtained based on inputting the running speed V of the vehicle in a one-dimensional table, and the front axle lateral force Fy 前 is multiplied by the first proportional coefficient to obtain the rack force F2.

[0014] In some embodiments, in the step S32, the rack force F2 is obtained based on inputting the front axle lateral force Fy 前 and the running speed V of the vehicle in a two-dimensional table.

[0015] According to a second aspect of the embodiments of the present disclosure, the present disclosure provides a rack force obtaining system of an SBW vehicle, comprising: a judging unit configured to judge whether the vehicle meets a condition that the wheels are in a steering static state and the friction force is dominant according to an operating parameter of a steering motor of the vehicle; a first calculation model unit configured to, in response to not meeting the condition, obtain a rack thrust F1 applied on the rack by the steering motor and a friction force f of the system, and obtain a rack force F2 based on the rack thrust F1, the friction force f, and a mass m and an acceleration a of the rack; and a second calculation model unit configured to, in response to meeting the condition, obtain a front axle lateral force Fy 前 of the front axle of the wheels, and obtain the rack force F2 based on the front axle lateral force Fy 前 and a running speed V of the vehicle.

[0016] In some embodiments, in the judging unit, the operating parameter of the steering motor comprises an absolute value of a motor torque T, an absolute value of a motor rotation acceleration a, and an absolute value of a motor rotation speed v, wherein when the absolute value of the motor torque T, the absolute value of the motor rotation acceleration a, and the absolute value of the motor rotation speed v are all less than their corresponding limits, the vehicle is in a steering static state and the friction force is dominant, meeting the condition.

[0017] The technical solutions provided by the embodiments of the present disclosure can have the following beneficial effects: the operating parameter of the steering motor can reflect the actual working condition of the vehicle, different physical models are used to calculate the rack force according to different actual working conditions, not only the actual working condition is considered, but also the physical models are established according to basic physical laws, and various influences of the calculation process on the actual vehicle are also considered. Therefore, the rack force calculated by the method is more accurate, has high reliability and strong practicability, and does not need to increase additional sensors, and has low cost. BRIEF DESCRIPTION OF DRAWINGS

[0018] The accompanying drawings, which are incorporated into and form a part of the specification, illustrate one embodiment consistent with the present disclosure and, together with the description, serve to explain the principles of the disclosure.

[0019] Figure 1 is a flowchart of a method for acquiring rack force of a SBW vehicle according to an example embodiment;

[0020] Figure 2 is a schematic diagram of a first physical model according to an example embodiment;

[0021] Figure 3 is a schematic diagram of a second physical model according to an example embodiment. DETAILED DESCRIPTION

[0022] The example embodiments will be described in detail herein with reference to the attached drawings. In the following description, like reference numerals refer to like elements, unless the context clearly dictates otherwise. The following description of example embodiments is not representative of all embodiments consistent with the present disclosure. Rather, it is merely an example of devices and methods consistent with some aspects of the present disclosure as detailed in the appended claims.

[0023] To solve the above technical problem, the present disclosure provides a method for acquiring rack force of a SBW vehicle, as shown in Figure 1 The method of the present disclosure can include the following steps:

[0024] Step S10: judging whether the vehicle meets the condition that the wheels are in steering static and friction dominant state according to the operating parameters of the vehicle steering motor;

[0025] Step S20: in response to not meeting the condition, using a first physical model to calculate the rack force F2.

[0026] Step S30: in response to meeting the condition, using a second physical model to calculate the rack force F2.

[0027] In step S10, the operating parameters of the steering motor can include the absolute value of the motor torque T, the absolute value of the motor rotational acceleration a, and the absolute value of the motor speed v. When the absolute value of the motor torque T is greater than its corresponding limit, it indicates that the motor torque T meets the condition; when the absolute value of the motor rotational acceleration a is greater than its corresponding limit, it indicates that the motor rotational acceleration a meets the condition; and when the absolute value of the motor speed v is greater than its corresponding limit, it indicates that the motor speed v meets the condition.

[0028] In step S20, when at least one of the above operating parameters meets the condition, at this time, the vehicle does not meet the condition that the wheels are in steering static and friction dominant state, which indicates that the wheels are in a dynamic state of left and right rotation, therefore, a first physical model as shown in Figure 2The first physical model shown is used to calculate the rack force F2. The condition that at least one operating parameter satisfies refers to the condition that only one operating parameter satisfies, or the condition that two operating parameters satisfy, or the condition that all operating parameters satisfy.

[0029] When all the operating parameters do not satisfy the condition in step S30, it indicates that the wheel is in a steering static and friction dominant state, and at this time, the second physical model shown can be used to calculate the rack force F2. Figure 3 The second physical model shown is used to calculate the rack force F2. It should be noted that the wheel in steering static does not mean that the wheel is in a steering zero angle (i.e., the wheel is in a middle position), but can be in a steering angle state (i.e., the vehicle can be in a left turn or right turn steering angle position).

[0030] Therefore, the operating parameters such as motor torque T, motor rotational acceleration a and motor speed v can truly reflect the actual working condition of the vehicle, i.e., whether the wheel is in a static and friction dominant state. By considering the actual operating parameters of the steering motor, different physical models are used to calculate the rack force F2, which not only considers the actual working condition, but also considers the calculation process of the actual vehicle. Therefore, the method of the present application does not need to increase additional sensors to obtain the rack force, reduces the cost, and the calculated rack force F2 is more accurate, has high reliability and strong practicability.

[0031] Further, step S20 further includes the following steps:

[0032] Step S21: Obtain the rack thrust F1 applied by the steering motor on the rack and the friction force f of the system; specifically, based on the motor torque T, the motor moment of inertia J, and the motor rotational acceleration a and the equivalent force arm d of the motor to the rack, according to Newton mechanics, F1=(T-J* a) / d, the rack thrust F1 applied by the steering motor on the rack is calculated. Wherein, the motor torque T, the moment of inertia J, the motor rotational acceleration a can be measured by the existing sensors of the vehicle, and the equivalent force arm d is obtained according to the related mechanical data, such as the speed ratio of the gear, the lead of the ball screw.

[0033] Step S22: Based on the rack thrust F1, the friction force f, and the mass m and acceleration a of the rack, the rack force F2 is obtained; according to Newton mechanics, F1-f-F2=m*a, i.e., the rack force F2=F1-f-m*a. Wherein, a= a x d. Finally, the rack force F2=(T-J* a) / d-f-m x d x a. The mass m of the rack is the mass known at the factory.

[0034] Therefore, the rack force F2 can be obtained by the formula F2=(T-J*α) / d-f-m×d×α, which combines the basic principles of Newtonian mechanics and considers multiple key factors, including the motor torque T, the rotational inertia J, the motor rotational acceleration α, the system friction f, the mass m, and the rack acceleration a(d×α). This makes the calculated rack force F2 more closely resemble the complex conditions of the road surface during actual vehicle operation and comprehensively reflects the effects of various forces.

[0035] In addition, the formula for calculating the rack force F2 also considers the system friction f, which is a key factor that causes energy loss and dynamic performance degradation. By considering the friction f, the calculated rack force F2 is more accurate, which helps to more accurately predict and control the dynamics of the vehicle. This makes the calculated rack force F2 more accurate, significantly improving the practicality and accuracy of the calculation results.

[0036] Among them, the system friction f considers the influence of two factors on the friction f, so in step S21, the system friction f at least includes the first friction f1 and the second friction f2. The friction f considers the motor torque and the motor speed, which is more close to the actual working condition, and improves the reliability and accuracy of the friction f calculation.

[0037] Among them, the first friction f1 is obtained by looking up the table based on the input motor torque T and rack position in the two-dimensional table; the second friction f2 is obtained by looking up the table based on the input motor speed v and rack position in the two-dimensional table. Among them, the rack position can also be measured by the existing position sensor of the vehicle.

[0038] Through the pre-established two-dimensional lookup table, the steering system can quickly find the friction value corresponding to the current motor torque T, motor speed v and rack position in a short time, greatly shortening the calculation time, improving the control response speed, and meeting the needs of real-time control application.

[0039] Further, when calculating the system friction f, the direction of the friction f should also be further considered. The direction of the friction f is opposite to the direction of the wheel rotation, for example, when the wheel rotates to the left (counterclockwise), the direction of the friction f is to the right (clockwise), and similarly, when the wheel rotates to the right (clockwise), the direction of the friction f is to the left (counterclockwise).

[0040] The direction of the wheel rotation is related to the direction of the motor speed of the steering motor, so in this embodiment, the direction of the friction f is determined based on the motor speed v and the direction of the motor speed v, and when the direction of the friction f changes, the gradient smoothing processing is performed on the friction f through the gradient filtering mechanism.

[0041] Specifically, in response to the motor speed v being greater than a first limit, the first limit being a positive value, for example, the first limit = 2 rpm, the direction sign of the friction force f is defined as positive. It can be known that the motor speed v > 2 rpm and the motor drives the wheels to rotate in the counterclockwise direction, at this time, the direction of the friction force f is opposite to the direction of the wheel rotation, that is, the friction force f is in the clockwise direction, therefore, the direction sign of the friction force f is positive.

[0042] Similarly, in response to the motor speed v being less than a second limit, the second limit being a negative value, for example, the second limit = -2 rpm, the direction sign of the friction force f is defined as negative. It can be known that the motor speed v < -2 rpm and the motor drives the wheels to rotate in the clockwise direction, at this time, the direction of the friction force f is opposite to the direction of the wheel rotation, that is, the friction force f is in the counterclockwise direction, therefore, the direction sign of the friction force f is negative.

[0043] When the motor speed v is greater than the second limit and less than the first limit, the direction of the friction force f remains the previous direction. If the previous motor speed v > 2 rpm, the direction sign of the previous friction force f is positive, therefore, when -2 rpm < motor speed v < 2 rpm, the direction sign of the friction force f is also positive. If the previous motor speed v < -2 rpm, the direction sign of the previous friction force f is negative, therefore, when -2 rpm < motor speed v < 2 rpm, the direction sign of the friction force f is also negative.

[0044] By considering the motor speed v and the direction of the motor speed v, the direction of the friction force f is determined, which improves the accuracy of the determination of the friction force f and enhances the reliability and accuracy of the calculation result of the rack force F2.

[0045] In some embodiments, when the direction of the friction force f changes, the gradient smoothing processing is performed on the friction force f through a gradient filtering mechanism. Through gradient filtering, the impact of the sudden change of the friction force f on the steering system can be effectively inhibited, the gradient filtering can smooth the change of the transition force, reduce the jitter and instability in the system response, improve the smoothness of the wheel rotation, thereby improving the stability of the entire steering system and improving the user experience.

[0046] Further, the step S30 specifically comprises the following steps:

[0047] Step S31: acquiring the front axle lateral force Fy of the front axle of the wheel 前 . Wherein, Fy 前 is the force acting on the rack.

[0048] Specifically, as shown in Figure 3 , the sum of the lateral force Fy1 received by the left front wheel FL and the lateral force Fy2 received by the right front wheel FR is the front axle lateral force Fy 前= (Fy1 + Fy2), the sum of the lateral force Fy3 received by the left rear wheel RL and the lateral force Fy4 received by the right rear wheel RR is the rear axle lateral force Fy 后 = (Fy3 + Fy4).

[0049] Fy 前 and Fy 后 is obtained by the following formula:

[0050] (Fy1 + Fy2) x a - (Fy3 + Fy4) x b = J 车 x a 车 ;

[0051] Fy1 + Fy2 + Fy3 + Fy4 = M x ay;

[0052] wherein J 车 : the moment of inertia of the vehicle, which is a known quantity.

[0053] M: the mass of the vehicle, which is a known quantity.

[0054] V: the vehicle speed, which can be obtained by a sensor.

[0055] w: the lateral angular velocity of the vehicle, which can be obtained by a sensor.

[0056] a 车 : the lateral acceleration of the vehicle, which can be obtained by differentiating the lateral angular velocity w of the vehicle.

[0057] ay: the lateral acceleration of the vehicle, ax: the longitudinal acceleration of the vehicle, both of which can be obtained by a sensor.

[0058] Further, step S32: obtaining the rack force F2 based on the front axle lateral force Fy 前 and the running speed V of the vehicle.

[0059] In step S32, in one embodiment, a first proportional coefficient is obtained based on the input of the running speed V of the vehicle in a one-dimensional table, the front axle lateral force Fy 前 is multiplied by the first proportional coefficient to obtain the rack force F2.

[0060] In step S32, in another embodiment, the rack force F2 is obtained by table lookup based on the input of the front axle lateral force Fy 前 and the running speed V of the vehicle in a two-dimensional table.

[0061] In summary, the rack force F2 is obtained by the method of the present application, which is economical, efficient, accurate and reliable. This method can accurately capture and restore the road information in the vehicle driving without significantly increasing the cost, ensure that the driver can obtain the natural steering feedback close to the traditional vehicle through the steering wheel, and enable the driver to perceive the road feel of the actual driving state and road conditions of the vehicle, thereby comprehensively improving the control quality and user satisfaction of the SBW vehicle.

[0062] Based on the same inventive concept, the present disclosure provides a rack force acquisition system of an SBW vehicle, comprising: a judgment unit configured to judge whether the operating parameters of the vehicle steering motor meet the condition; a first calculation model unit configured to, in response to at least one operating parameter of the steering motor meeting the condition, acquire the rack thrust F1 applied by the steering motor on the rack and the friction force f of the system, and acquire the rack force F2 based on the rack thrust F1, the friction force f, and the mass m and acceleration a of the rack. 前 前 and the driving speed V of the vehicle.

[0063] In the judgment unit, the operating parameters of the steering motor include the absolute value of the motor torque T, the absolute value of the motor rotation acceleration a, and the absolute value of the motor speed v, wherein when the absolute value of the motor torque T, the absolute value of the motor rotation acceleration a, and the absolute value of the motor speed v are all less than the corresponding limit, the vehicle is in a steering static state and the friction force is dominant, which meets the state condition.

[0064] The specific manner of the functions realized in the rack force acquisition system of the SBW vehicle in the above-mentioned embodiments has been described in detail in the embodiments related to the method, and will not be described in detail here.

[0065] It can be understood that "multiple" in the present disclosure means two or more, and other quantifiers are similar. "And / or" describes the association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B can represent: A exists alone, A and B exist together, and B exists alone. The character " / " generally represents that the associated objects before and after it are in an "or" relationship. The singular form "a", "said" and "the" are also intended to include the plural form, unless the context clearly indicates otherwise.

[0066] ​It will be further appreciated that terms such as "first", "second", etc. for descriptive purposes only and not to be taken literally to denote a particular order or importance. These terms merely designate the different structures for one another, and do not constitute a specific sequential or chronological order. Indeed, complete permutations of such designations will be implicitly and explicitly encompassed herein. For example, a first structure can also be referred to as a second structure, and similarly, a second structure can also be referred to as a first structure, without departing from the scope of the present disclosure.

[0067] It will be further appreciated that, in embodiments of the present disclosure, although the operations are described in a particular, sequential order, this should not be understood as requiring that such operations be performed in the described order, or in sequential order, or that all operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing can be advantageous.

[0068] Other embodiments of the present disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the features of the present disclosure disclosed herein. It is intended that the present disclosure cover any and all variations of the present disclosure including those variations comprising any additional input means, signal processing means and / or output means to the structural elements of the present disclosure disclosed herein. It is intended that the specification and examples be considered exemplary only, with the true scope and spirit of the present disclosure being indicated by the following claims.

[0069] It is to be understood that the present disclosure is not limited to the precise structures herein described and illustrated in the drawings, and that various modifications and changes can be made without departing from the scope thereof. The scope of the present disclosure is limited only by the claims that follow.

Claims

1. A method for obtaining rack force in an SBW vehicle, characterized in that, Includes the following steps: Step S10: Based on the operating parameters of the vehicle steering motor, determine whether the vehicle meets the condition that the wheels are stationary and friction is dominant. Step S20: In response to the failure to meet the state conditions, adopt the first physical model, including: Step S21: Obtain the rack thrust F1 applied to the rack by the steering motor and the frictional force f of the system; Step S22: Based on the rack thrust F1, frictional force f, and the rack mass m and acceleration a, obtain the rack force F2; Step S30: In response to satisfying the state condition, adopt the second physical model, including: Step S31: Obtain the lateral force Fy of the front axle of the wheel. 前 ; Step S32: Based on the front axle lateral force Fy 前 The rack force F2 is obtained from the vehicle's speed V.

2. The method for obtaining rack force of an SBW vehicle according to claim 1, characterized in that, In step S10, the operating parameters of the steering motor include the absolute value of the motor torque T, the absolute value of the motor rotational acceleration α, and the absolute value of the motor speed v. Specifically, when the absolute values ​​of the motor torque T, the motor rotational acceleration α, and the motor speed v are all less than their corresponding limits, the vehicle is in a state of steering stillness and friction dominating, thus satisfying the state conditions.

3. The method for obtaining rack force of an SBW vehicle according to claim 1, characterized in that, In step S21, the rack thrust F1 applied by the steering motor to the rack is calculated based on the motor torque T, the motor moment of inertia J, the motor rotational acceleration α, and the equivalent force arm d of the motor on the rack.

4. The method for obtaining rack force of an SBW vehicle according to claim 1, characterized in that, In step S21, the frictional force f of the system includes: The first frictional force f1 is obtained by looking up the table after inputting the motor torque T and rack position in the two-dimensional table; The second frictional force f2 is obtained by looking up the table after inputting the motor speed v and rack position in the two-dimensional table.

5. The method for obtaining rack force of an SBW vehicle according to claim 1, characterized in that, Based on the motor speed v, the direction of the friction force f is determined. When the direction of the friction force f changes, the friction force f is smoothed by a gradient filtering mechanism.

6. The method for obtaining rack force in an SBW vehicle according to claim 5, characterized in that, When the motor speed v is greater than the first limit, the direction of the frictional force f is positive. When the motor speed v is less than the second limit, the direction of the frictional force f is negative. If the motor speed v is greater than the second limit and less than the first limit, the direction of the frictional force f remains the same as before. In this case, the motor drives the wheel to rotate counterclockwise, with the direction sign of the motor speed v being positive and the first limit being positive; when the motor drives the wheel to rotate clockwise, the direction sign of the motor speed v is negative and the second limit is negative.

7. The method for obtaining rack force in an SBW vehicle according to claim 1, characterized in that, In step S32, a first proportional coefficient is obtained based on the vehicle's driving speed V input in a one-dimensional table, and the front axle lateral force Fy is... 前 Multiply by the first proportionality coefficient to obtain the rack force F2.

8. The method for obtaining rack force of an SBW vehicle according to claim 1, characterized in that, In step S32, the front axle lateral force Fy is input into the two-dimensional table. 前 The rack force F2 is obtained by looking up the table based on the vehicle's speed V.

9. A rack force acquisition system for an SBW vehicle, characterized in that, include: Judgment unit: configured to determine whether the vehicle meets the condition that the wheels are stationary and friction is dominant based on the operating parameters of the vehicle steering motor; First calculation model unit: configured to respond to the failure to meet state conditions, including: obtaining the rack thrust F1 applied to the rack by the steering motor and the friction force f of the system, and obtaining the rack force F2 based on the rack thrust F1, the friction force f, and the mass m and acceleration a of the rack; The second computational model unit is configured to respond to satisfied state conditions, including: acquiring the front axle lateral force Fy of the wheel's front axle. 前 And based on the front axle lateral force Fy 前 The rack force F2 is obtained from the vehicle's speed V.

10. The rack force acquisition system for SBW vehicles according to claim 9, characterized in that, In the judgment unit, the operating parameters of the steering motor include the absolute value of the motor torque T, the absolute value of the motor rotational acceleration α, and the absolute value of the motor speed v. Specifically, when the absolute values ​​of the motor torque T, the motor rotational acceleration α, and the motor speed v are all less than their corresponding limits, the vehicle is in a state of steering stillness and friction dominating, thus satisfying the state conditions.

Images