Target turning angle control method and system based on steer-by-wire

Abstract

The invention belongs to the field of control algorithms of target turning angle control systems, and particularly relates to a target turning angle control method and system based on steer-by-wire. The target turning angle control method based on the steer-by-wire comprises the steps that the current vehicle speed value and the gear target turning angle of a target turning angle control system during steering are obtained; calculating a first target rotation angle compensation angle and a second target rotation angle compensation angle according to the current vehicle speed value and the gear target rotation angle; determining one of the first target corner compensation angle and the second target corner compensation angle as a current compensation angle according to the current vehicle speed value; and compensating the target rotation angle of the gear by using the current compensation angle. The target rotating angle of the gear is adjusted through the selected compensation angle, and more accurate and stable steering control is achieved. At a low speed and a small steering wheel rotation angle, the compensation can reduce unnecessary transverse movement, and the problem that the transverse movement amount of a target rotation angle control system is too large due to a large steering angle caused by the low speed and the small steering wheel rotation angle is solved.

Description

Technical Field

[0001] The present application relates to the field of vehicle control, and in particular to a target turning angle control method and system based on wire-controlled steering. Background Art

[0002] The steer-by-wire (SBW) system uses an electronic control unit (ECU) to precisely control the steering of the target angle control system. The control process is as follows:

[0003] 1) The steering angle sensor and torque sensor at the steering wheel measure the steering wheel angle and torque respectively, and convert this information into electrical signals and transmit it to the central control unit (ECU). At the same time, other sensors (such as vehicle speed sensor, longitudinal acceleration sensor, yaw rate sensor, etc.) also collect the operating status information of the target angle control system and transmit it to the ECU.

[0004] 2) After receiving information from each sensor, the ECU performs data processing and fusion. This process includes data filtering and calibration to ensure that the system accurately recognizes the actual state of the target angle control system.

[0005] 3) Based on the steering wheel angle and the preset ideal transmission ratio, the ECU calculates the front pinion target angle for two-wheel steering. In a four-wheel steering system, the ECU further calculates the front pinion target angle and rear pinion target angle for four-wheel steering based on the front pinion target angle and vehicle speed information.

[0006] 4) The ECU sends the calculated target angle to the steering actuator controller, which then performs closed-loop control of the steering motor according to the target angle to achieve the steering operation of the target angle control system.

[0007] Existing steer-by-wire systems mostly rely solely on direct measurement and calculation of the steering wheel angle sensor when using the front wheel pinion target angle. The applicant has found that under high- and low-speed switching conditions, the method significantly increases the influence of the lateral acceleration of the target angle control system on the steering stability. If the front wheel pinion target angle is calculated only based on the steering wheel angle and the ideal transmission ratio, the influence of the lateral acceleration on the steering characteristics may be ignored, resulting in insufficient steering stability of the target angle control system when driving at high and low speeds. Summary of the invention

[0008] In order to solve the above problems, the present application develops a target angle control method and a target angle control system based on wire-controlled steering for a target angle control system.

[0009] According to one aspect of the present application, a target angle control method based on wire-controlled steering is provided, including: obtaining a current vehicle speed value and a gear target angle of a target angle control system during steering; calculating a first target angle compensation angle and a second target angle compensation angle according to the current vehicle speed value and the gear target angle; determining to use one of the first target angle compensation angle and the second target angle compensation angle as a current compensation angle according to the current vehicle speed value; and compensating the gear target angle using the current compensation angle.

[0010] In a further scheme of the present application, determining whether to use one of the first target steering angle compensation angle and the second target steering angle compensation angle as the current compensation angle based on the current vehicle speed value includes: judging whether the current vehicle speed value is lower than the target threshold; if it is lower than the target threshold, using the first target steering angle compensation angle as the current compensation angle, otherwise using the second target steering angle compensation angle as the current compensation angle.

[0011] In a further scheme of the present application, the method also includes: determining whether the current vehicle speed value reaches the target threshold during the steering process; if the target threshold is reached, transitioning the current compensation angle adopted from one of the first target turning angle compensation angle and the second target turning angle compensation angle to the other of the first target turning angle compensation angle and the second target turning angle compensation angle; determining whether the transition stop condition is met; if the transition stop condition is met, using the compensation angle after the transition as the current compensation angle.

[0012] In a further scheme of the present application, the determination of whether the transition stop condition is met includes: calculating the gain coefficient K based on the first target steering angle compensation angle and the second target steering angle compensation angle; determining whether the gain coefficient is less than the transition switching threshold; if it is less than the transition switching threshold, determining that the transition stop condition is met.

[0013] In a further scheme of the present application, calculating the gain coefficient K based on the first target angle compensation angle and the second target angle compensation angle includes: calculating the absolute value of the difference between the first target angle compensation angle and the second target angle compensation angle; and determining the corresponding gain coefficient K based on the absolute value of the difference.

[0014] In a further scheme of the present application, determining the corresponding gain coefficient K based on the absolute value of the difference includes: when the absolute value of the difference is less than a first threshold, using a fixed value K1 as the gain coefficient K; when the absolute value of the difference is greater than a second threshold, using a fixed value K2 as the gain coefficient K; when the absolute value of the difference is between the first threshold and the second threshold, using a preset linear relationship between the absolute value of the difference and the gain coefficient to determine the K3 value as the gain coefficient K.

[0015] In a further solution of the present application, if the current compensation angle adopts the first target rotation angle compensation angle, the transition of the current compensation angle adopted from one of the first target rotation angle compensation angle and the second target rotation angle compensation angle to the other of the first target rotation angle compensation angle and the second target rotation angle compensation angle comprises: calculating the target compensation angle during transition by using the following formula: second target rotation angle compensation angle*gain coefficient K-first target rotation angle compensation angle*(1-gain coefficient K);

[0016] If the current compensation angle adopts the second target angle compensation angle, the transition of the current compensation angle adopted from one of the first target angle compensation angle and the second target angle compensation angle to the other of the first target angle compensation angle and the second target angle compensation angle includes: using the following formula to calculate the target compensation angle during transition: second target angle compensation angle*(1-gain coefficient K)-first target angle compensation angle*gain coefficient K; wherein the gain coefficient K is calculated based on the first target angle compensation angle and the second target angle compensation angle.

[0017] The calculating the first target turning angle compensation angle according to the current vehicle speed value and the target turning angle includes:

[0018] In a further solution of the present application, the first target rotation angle compensation angle is obtained by the following formula:

[0019]

[0020]

[0021] Among them, a0 = k1k2lu 2 ;a1=k1k2blu;a2=-k1I z u 2 ; b1=-(k1+k2)I z u-(a 2 k1+b 2 k2)mu; b2=mI z u 2 ; b0 = l 2 k1k2-(ak1-bk2)mu 2 ; δ f =ne;

[0022] δ f_lowSpeedcmp is the first target turning angle compensation angle; l is the distance from the front axle to the rear axle; β is the sideslip angle of the center of mass; γ is the yaw rate; δ f is the front wheel turning angle; n is the proportional factor; e is the target turning angle; a is the distance from the center of mass to the front axle; b is the distance from the center of mass to the rear axle; u is the current vehicle speed; I zis the moment of inertia of the target steering angle control system around the z-axis; k1 is the cornering stiffness of the front tire; k2 is the cornering stiffness of the rear tire.

[0023] In a further solution of the present application, the calculating the second target turning angle compensation angle according to the current vehicle speed value and the target turning angle includes:

[0024] The second target rotation angle compensation angle is obtained by the following formula:

[0025]

[0026]

[0027] Among them, a0 = k1k2lu 2 ;a1=k1k2blu;a2=-k1I z u 2 ; b1=-(k1+k2)I z u-(a 2 k1+b 2 k2)mu; b2=mI z u 2 ; b0 = l 2 k1k2-(ak1-bk2)mu 2 ; δ f =n;

[0028] δ f_highSpeedcmp is the second target turning angle compensation angle; l is the distance from the front axle to the rear axle; β is the sideslip angle of the center of mass; γ is the yaw rate; δ f is the front wheel turning angle; n is the proportional factor; e is the target turning angle; a is the distance from the center of mass to the front axle; b is the distance from the center of mass to the rear axle; u is the current vehicle speed; I z is the moment of inertia of the target steering angle control system around the z-axis; k1 is the cornering stiffness of the front tire; k2 is the cornering stiffness of the rear tire.

[0029] The second aspect of the present application also provides a target angle control system, including: a gear target angle module, which obtains the current vehicle speed value and the steering wheel angle, and calculates the gear target angle based on the current vehicle speed value and the steering wheel angle; a target angle compensation module, which is electrically connected to the gear target angle module, and the gear target angle module is configured to execute the above-mentioned target angle control method based on wire-controlled steering.

[0030] In summary, the present application provides a method and system for controlling a target angle based on wire control steering, the method comprising: obtaining the current vehicle speed value and the gear target angle of the target angle control system during steering; calculating the first target angle compensation angle and the second target angle compensation angle according to the current vehicle speed value and the gear target angle; determining to use one of the first target angle compensation angle and the second target angle compensation angle as the current compensation angle according to the current vehicle speed value; compensating the gear target angle using the current compensation angle; adjusting the gear target angle by the selected compensation angle to achieve more accurate and stable steering control. At low speeds and small steering wheel angles, this compensation can reduce unnecessary lateral movement, solving the problem of excessive lateral movement of the target angle control system caused by large steering angles due to low speeds and small steering wheel angles; at the same time, it can also improve steering stability at high speeds, thereby improving driving comfort and safety.

[0031] Other features and advantages of the embodiments of the present application will be described in the subsequent detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the specific implementation of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific implementation or the prior art description. Obviously, the drawings described below are some implementations of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0033] Figure 1 The overall flow chart of the target turning angle control method based on wire control steering shown in this application;

[0034] Figure 2 This is a flow chart of step S20 in the target turning angle control method based on wire control steer shown in this application;

[0035] Figure 3 A further flow chart of the target turning angle control method based on wire control steering shown in the present application;

[0036] Figure 4 This is a flow chart of step S63 in the target turning angle control method based on wire control steer shown in this application;

[0037] Figure 5 This is a flow chart of step S631 in the target turning angle control method based on wire control according to the present application;

[0038] Figure 6 This is a flow chart of step S6312 in the target turning angle control method based on wire control according to the present application;

[0039] Figure 7 This is a graph showing a change in the gain coefficient K as shown in the present application; wherein the abscissa is the absolute value of the difference between the first target rotation angle compensation angle and the second target rotation angle compensation angle; and the ordinate is the gain coefficient K;

[0040] Figure 8 This is a diagram showing the change of the target lateral acceleration indicated in the present application; the horizontal axis is the steering wheel angle; the vertical axis is the target lateral acceleration;

[0041] Fig. 9 A control topology diagram of a specific embodiment of a target turning angle control method based on steer-by-wire; and

[0042] Fig.10 A control topology diagram with logic nodes for a target angle control system based on steer-by-wire. DETAILED DESCRIPTION

[0043] In the description of this application, if there is a feature defined as "first" or "second" for descriptive purposes only, it cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Features defined as "first" or "second" may explicitly or implicitly include at least one of the defined features. If the description of "plurality" appears, the general meaning is to include at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0044] In the description of this specification, if the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" appear, it means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, unless they are contradictory.

[0045] As mentioned above, steering stability refers to the ability of a vehicle to maintain a predetermined path without excessive deviation or loss of control during a turn. Lateral acceleration is the lateral acceleration generated by a vehicle when turning, which makes the vehicle turn vertically and generates centrifugal force along the outside. At low speeds, due to the slow speed, the lateral acceleration is relatively small, and the effect on steering stability is not obvious. However, at high speeds, the lateral acceleration increases significantly, which has a significant impact on the dynamic behavior of the vehicle. And due to the increase in lateral acceleration, the lateral stiffness of the tire may decrease, causing the vehicle to become more sensitive to the front wheel angle. At this time, if the target angle of the front wheel pinion is still output according to conventional technical means, the vehicle may oversteer or understeer, thereby reducing the steering stability. Therefore, in order to maintain the steering stability of the vehicle under high and low speed switching conditions, a more advanced steering control strategy needs to be adopted.

[0046] This application proposes the following solutions to the above problems: Figure 1 A target turning angle control method based on wire control steering, the target turning angle control method comprising at least the following steps:

[0047] Step S10, obtaining the current vehicle speed value and gear target angle when the vehicle is turning;

[0048] Step S20, calculating a first target rotation angle compensation angle and a second target rotation angle compensation angle according to the current vehicle speed value and the gear target rotation angle;

[0049] Step S30, determining one of the first target steering angle compensation angle and the second target steering angle compensation angle as the current compensation angle according to the current vehicle speed value;

[0050] Step S40: Compensate the target rotation angle of the gear using the current compensation angle.

[0051] In the embodiment of the present invention, the “current vehicle speed value” refers to the current driving speed when the vehicle steering is triggered.

[0052] The gear target angle (also referred to as the "front wheel target angle") is the angle to which the front wheels should turn, calculated based on the steering wheel angle and the preset ideal gear ratio, without considering the effects of vehicle speed and lateral acceleration. This is the target angle initially calculated by the steer-by-wire system.

[0053] Using the current vehicle speed value and the gear target angle as input, two compensation angles are calculated through a preset algorithm: a first target angle compensation angle and a second target angle compensation angle. These two angles represent the angle compensation amount that needs to be adjusted at the proposed high and low vehicle speeds, respectively. In this application, the front wheel angle compensation is used as an example, and of course, it is not limited to at least one of the front and rear wheels.

[0054] It should be noted that steps S10 to S20 are interpreted as follows: when the driver starts to perform the steering operation (i.e., the vehicle just starts to turn), the vehicle speed value at the time of the initial steering and the gear target angle desired by the driver will be immediately obtained. At this time, continue to use the preset algorithm to calculate the angle compensation angles in two different speed ranges based on the current vehicle speed value and the gear target angle, namely, the first target angle compensation angle (defined in this application as being applicable to the low-speed range) and the second target angle compensation angle (defined in this application as being applicable to the high-speed range). It should be noted that the first target angle compensation angle and the second target angle compensation angle both use the current vehicle speed value and the gear target angle as variables, that is, the value of the compensation angle actually used during the steering process will depend on the above two variables that change in real time.

[0055] Furthermore, in step S30, determining to use one of the first target steering angle compensation angle and the second target steering angle compensation angle as the current compensation angle according to the current vehicle speed value, refers to judging by the change of the current vehicle speed value and the value size as conditions. That is, after obtaining the values ​​of the first target steering angle compensation angle and the second target steering angle compensation angle, it is necessary to determine which compensation angle is currently applicable. According to the above-mentioned conditions set in the embodiment of the present invention, one or more vehicle speed thresholds are set to distinguish different vehicle speed intervals. For example:

[0056] If the current vehicle speed is lower than a certain target threshold, the first target steering angle compensation angle is selected as the current compensation angle. Conversely, if the current vehicle speed is higher than the target threshold, the second target steering angle compensation angle is selected as the current compensation. This helps maintain the stability and controllability of the vehicle.

[0057] Finally, the gear target angle is compensated by the current compensation angle to obtain the final front wheel target angle. This final target angle will be used to control the steer-by-wire system so that the vehicle can steer according to the expected trajectory and stability.

[0058] That is, the present application is based on a general inventive concept, which is to dynamically adjust the front wheel angle by calculating and applying the target angle compensation angle according to the current vehicle speed value and the gear target angle, and to achieve active steering adjustment to adapt to the steering requirements at different speeds. This dynamic compensation mechanism helps to reduce the steering instability caused by changes in vehicle speed and improve the stability of the vehicle under high-speed driving or complex working conditions. Through target angle control, the driver can experience a smoother and more natural steering process, especially when switching between high and low speeds, reducing the discomfort caused by sudden changes in steering.

[0059] like Figure 2 As shown, as a specific embodiment of the present invention, determining in step S30 according to the current vehicle speed value to use one of the first target steering angle compensation angle and the second target steering angle compensation angle as the current compensation angle includes:

[0060] Step S21, determining whether the current vehicle speed value is lower than the target threshold;

[0061] Step S22: If it is lower than the target threshold, the first target rotation angle compensation angle is used as the current compensation angle; otherwise, the second target rotation angle compensation angle is used as the current compensation angle.

[0062] Specifically, steps S21 to S22 can be illustrated as: determining whether the current vehicle speed value is constantly lower than the target threshold or constantly higher than the target threshold during the turning process; if it is constantly lower than the target threshold, using the first target steering angle compensation angle as the current compensation angle; if it is constantly higher than the target threshold, using the second target steering angle compensation angle as the current compensation angle.

[0063] Correspondingly, during the entire time period when the vehicle performs the steering operation, whether the vehicle speed is always kept below or above the preset target threshold, and this state below or above the threshold is stable. It should be emphasized that "constant" only refers to the fact that the vehicle speed is always above or below the target threshold during the steering process, and does not mean that the change in the current vehicle speed value remains unchanged. In simple terms, if the current vehicle speed value is constantly below the target threshold during the steering process, even if it accelerates and decelerates, but its vehicle speed value is not higher than the target threshold after the entire steering, the system will select the first target steering angle compensation angle for steering compensation. On the contrary, if it is found that the vehicle speed is constantly higher than the target threshold, the second target steering angle compensation angle is selected for steering compensation. Taking the target threshold of 50km / h as an example, the vehicle speed during the steering process is continuously monitored. If the vehicle speed is always kept below 50km / h during the entire steering process, it can be considered that the vehicle speed is "constantly lower than" the target threshold. On the contrary, if it is judged that the vehicle speed is constantly higher than 50km / h, then the second target steering angle compensation angle is selected for steering compensation.

[0064] Based on a general inventive concept of an embodiment of the present invention, a selected compensation angle is applied to adjust the gear target angle to achieve more accurate and stable steering control. At low speed and small steering wheel angle, this compensation can reduce unnecessary lateral movement, solve the problem of excessive lateral movement of the target angle control system caused by large steering angles caused by low speed and small steering wheel angle, and improve driving comfort and safety.

[0065] Similarly, based on the current vehicle speed value and the gear target angle, the system is able to perform special processing for high-speed driving conditions. When calculating the compensation angle, the system takes into account the higher stability requirements of the target angle control system when driving at high speeds. Therefore, the second target angle compensation angle (usually designed for high speeds) tends to reduce the sensitivity of the steering to stabilize the gain value of the lateral acceleration. When the vehicle speed reaches or exceeds the preset target threshold, the system automatically selects the second target angle compensation angle as the current compensation angle. This ensures that when driving at high speeds, the steering response of the target angle control system is smoother and the gain value of the lateral acceleration remains within a reasonable range, thereby improving the driver's operability and the stability of the target angle control system.

[0066] Finally, by applying this high-speed-optimized compensation angle, the system can effectively suppress oversteer or instability that may occur when driving at high speeds, providing the driver with a more secure and stable driving experience.

[0067] like Figure 3 In a further embodiment of the present application, the above method further comprises:

[0068] Step S610: during the turning process, determining whether the current vehicle speed value reaches the target threshold;

[0069] "Determine whether the current vehicle speed value reaches the target threshold value" indicates that the vehicle speed value reaches the target threshold value under acceleration or deceleration. Taking the target threshold value of 50km / h as an example, if during the turning process, the current vehicle speed value gradually decelerates from above 50km / h and drops below 50km / h at a certain moment, then it can be considered that the vehicle speed value has reached the target threshold value. On the contrary, if the vehicle speed is lower than 50km / h at the beginning of the turn, but gradually accelerates during the turning process and exceeds 50km / h at a certain moment, then it can also be considered that the vehicle speed value has reached the target threshold value.

[0070] Step S620: if the target threshold is reached, the current compensation angle used is transitioned from one of the first target rotation angle compensation angle and the second target rotation angle compensation angle to the other of the first target rotation angle compensation angle and the second target rotation angle compensation angle;

[0071] For the convenience of explanation, the current vehicle speed value exceeding the target threshold is defined as "high vehicle speed", and the current vehicle speed value below the target threshold is defined as "low vehicle speed". If the current vehicle speed value decreases from high vehicle speed to low vehicle speed, the system will gradually transition from the current high speed compensation angle (e.g., the second target steering angle compensation angle) to the low speed compensation angle (e.g., the first target steering angle compensation angle). The transition process is relatively smooth, aiming to avoid sudden changes in the target steering angle compensation angle. Conversely, if the current vehicle speed value increases from low vehicle speed to high vehicle speed, it will gradually transition from the current low speed compensation angle to the high speed compensation angle. Similarly, this transition process is also smooth to ensure the continuity and stability of the steering performance. This transition is crucial to improving the steering performance and driving experience of the target steering angle control system at different vehicle speeds. Ensure that the target steering angle control system can maintain stable steering response and safety when the vehicle speed changes.

[0072] Step S630, determining whether the transition stop condition is met;

[0073] After the compensation angle transition, it is determined whether the transition stop conditions are met. These conditions may include determining whether the steering transition is completed through a certain coefficient, or whether other related control instructions are received, etc., to ensure that the adjustment of the compensation angle stops at an appropriate time.

[0074] Step S640: When the transition stop condition is met, the compensation angle after the transition is used as the current compensation angle.

[0075] During the steering process, the value and changes of the current vehicle speed are continuously monitored and compared with the preset target threshold.

[0076] If the transition stop condition is met, the compensation angle after the transition is used as the current compensation angle (i.e., the transition from the first target angle compensation angle to the second target angle compensation angle, or the second target angle compensation angle to the first target angle compensation angle), and this angle continues to be used to compensate the front wheel angle to maintain the stability and safety of the target angle control system during the steering process.

[0077] Based on the above steps S510 to S520, and steps S610 to S640, the details are as follows:

[0078] First, the current vehicle speed value at the initial turn of the target angle control system is obtained, and the current vehicle speed value is compared with the preset target threshold value according to the change of the vehicle speed value. The change of the vehicle speed value and the result of the comparison will determine the working condition of the target angle control system.

[0079] When the current vehicle speed value at the time of turning is initially greater than the target threshold, it decelerates to below the target threshold. At this time, the target turning angle control system is determined to be in working condition 1, that is, from high vehicle speed to low vehicle speed as mentioned above.

[0080] When the current vehicle speed value is less than the target threshold value at the time of turning, and accelerates to be equal to or higher than the target threshold value, the target turning angle control system is determined to be in the second working condition, that is, from low speed to high speed as mentioned above. If the initial vehicle speed is greater than the target threshold value, and the vehicle speed is always kept above the target threshold value during the subsequent turning process (whether accelerating or decelerating), then the target turning angle control system is determined to be in the third working condition. On the contrary, if the initial vehicle speed is less than the target threshold value, and the vehicle speed is always kept below the target threshold value during the subsequent turning process, then the target turning angle control system is determined to be in the fourth working condition.

[0081] In the following working condition, the vehicle speed is decreasing from high speed to low speed. Therefore, the compensation angle suitable for high speed driving (i.e., the second target steering angle compensation angle) is used first to ensure that the target steering angle control system has good steering stability and responsiveness when the vehicle speed is high. As the vehicle speed decreases, the system will gradually transition to the compensation angle suitable for low speed driving (i.e., the first target steering angle compensation angle) to provide more precise steering control and a better driving experience.

[0082] In the second working condition, the vehicle speed is increasing from low speed to high speed. The compensation angle suitable for low speed driving (i.e., the first target angle compensation angle) is used first to ensure that the target angle control system can easily steer and avoid over-response when the vehicle speed is low. As the vehicle speed increases, the system will gradually transition to the compensation angle suitable for high speed driving (i.e., the second target angle compensation angle) to improve the stability and safety of the target angle control system when driving at high speed.

[0083] Under condition three, the target angle control system always maintains a vehicle speed above the preset target threshold, regardless of whether it is decelerating or accelerating. Conventional high-speed compensation (second target angle compensation angle) is always used as the current compensation angle. When the vehicle speed is higher than the target threshold, the target angle control system has higher requirements for steering responsiveness and stability. The use of high-speed compensation ensures that the target angle control system can still maintain good steering performance and safety under these conditions. Even if the vehicle speed changes (whether it is decelerating or accelerating), as long as it remains above the target threshold, the system will not change the compensation angle.

[0084] Under working condition 4: the system will always use conventional low-speed compensation (i.e. the first target steering angle compensation angle) as the current compensation angle. Low-speed compensation is designed to provide more precise steering control and a better driving experience when the vehicle speed is lower. When the vehicle speed is below the target threshold, the target steering angle control system has relatively low requirements for steering responsiveness and stability, so it is appropriate to use low-speed compensation. Similarly, even if the vehicle speed is changing (whether decelerating or accelerating), as long as it remains within the range below the target threshold, the system will not change the compensation angle.

[0085] Whether it is from high speed to low speed or from low speed to high speed, the system can provide steering response and precision that matches the current vehicle speed. At low speed, the steering is more flexible and easy to control; at high speed, the steering is more stable and predictable. This highly adaptable steering control can improve driving comfort.

[0086] like Figure 4 As a preferred solution of an embodiment of the present invention, the determination of whether the transition stop condition is met in step S630 includes:

[0087] Step S631, calculating a gain coefficient K according to a first target rotation angle compensation angle and a second target rotation angle compensation angle;

[0088] The gain coefficient K is used to quantify the difference or similarity between the first target steering angle compensation angle (low speed compensation) and the second target steering angle compensation angle (high speed compensation). This difference or similarity reflects the applicability of the two compensation angles at the current vehicle speed.

[0089] Step S632, determining whether the gain coefficient is less than the transition switching threshold;

[0090] The "transition switching threshold" is a preset threshold used to determine whether the compensation angle switching needs to be stopped. When the gain coefficient K is less than this threshold, it means that the difference between the two compensation angles is small enough, or the current compensation angle is sufficient to adapt to the current vehicle speed and steering requirements. If the gain coefficient K is less than the transition switching threshold, the system believes that a suitable compensation angle has been found and no further switching is required.

[0091] Step S633: If it is less than the transition switching threshold, it is determined that the transition stop condition is met.

[0092] When the gain coefficient K is less than the transition switching threshold, the system confirms that the transition stop condition has been met and stops further compensation angle switching. This ensures that the steering system can maintain stable performance under the current vehicle speed and steering requirements.

[0093] like Figure 5, in step S631, calculating the gain coefficient K according to the first target rotation angle compensation angle and the second target rotation angle compensation angle includes:

[0094] Step S6311, calculating the absolute value of the difference between the first target rotation angle compensation angle and the second target rotation angle compensation angle;

[0095] Step S6312: determine the corresponding gain coefficient K according to the absolute value of the difference.

[0096] Determine the specific difference between the two compensation angles. The positive and negative directions are not considered in this application because the angle difference of the steering compensation is relative in direction. Subtract the second target steering angle compensation angle from the first target steering angle compensation angle (or vice versa, depending on which angle is set as the reference), and then take the absolute value of the result. This absolute value represents the actual difference between the two compensation angles.

[0097] The absolute value of the difference is then mapped to a predefined gain coefficient K. This mapping relationship is usually implemented by looking up a table, which defines the corresponding relationship between different difference ranges and the gain coefficient K.

[0098] Combined with the above, the gain factor K allows the system to smoothly transition between high and low speed compensation angles, avoiding the target angle control system from losing control due to sudden changes in steering characteristics. This smooth transition reduces the steering differences that the driver needs to adapt to when the vehicle speed changes, thereby improving overall driving stability.

[0099] like Figure 6 and Figure 7 In a specific solution, determining the corresponding gain coefficient K according to the absolute value of the difference in step S6312 includes:

[0100] Step S6312a: when the absolute value of the difference is less than the first threshold, the fixed value K1 is used as the gain coefficient K;

[0101] Step S6312b: when the absolute value of the difference is greater than the second threshold, the fixed value K2 is used as the gain coefficient K;

[0102] Step S6312c: when the absolute value of the difference is between the first threshold and the second threshold, the K3 value is determined as the gain coefficient K using the preset linear relationship between the absolute value of the difference and the gain coefficient.

[0103] If the calculated absolute value of the difference is less than the preset first threshold, a fixed gain coefficient value K1 is used as the current gain coefficient K. If the calculated absolute value of the difference is greater than the preset second threshold, this indicates that there is a significant difference between the two compensation angles. Another fixed gain coefficient value K2 (K2 is greater than K1) is used as the current gain coefficient K. This is usually to enable the system to quickly and obviously switch to a more appropriate compensation angle when the difference is large.

[0104] If the calculated absolute value of the difference is between the first threshold and the second threshold, the system will use the preset linear relationship between the absolute value of the difference and the gain coefficient to determine a gain coefficient value K3 between K1 and K2. The purpose is to smoothly adjust the gain coefficient when the difference changes, so as to achieve a smooth transition between the two compensation angles. That is, when the absolute value of the difference is greater than the first threshold and less than the second threshold, the gain coefficient and the absolute value of the difference change linearly, and the gain coefficient value K3 can be determined based on the absolute value of the difference and the linear relationship. In one example, the correspondence between the absolute value of the difference between the high and low speed compensation angles and the gain coefficient is as follows: Figure 7 as shown in .

[0105] By flexibly determining the value of the gain coefficient K according to the absolute value of the difference of different sizes, it ensures that stable, smooth and appropriate steering compensation can be provided under different driving conditions, thereby improving driving safety, comfort and stability. At the same time, through the preset threshold and linear relationship, the system can also avoid unnecessary adjustments when the difference is small, and excessive adjustments when the difference is large, thereby further optimizing the performance and responsiveness of the system.

[0106] In an embodiment of the present application, in step S620, if the current compensation angle adopts the second target rotation angle compensation angle, that is, the above-mentioned working condition 1, the current compensation angle adopted is transitioned from one of the first target rotation angle compensation angle and the second target rotation angle compensation angle to the other of the first target rotation angle compensation angle and the second target rotation angle compensation angle, including:

[0107] The target compensation angle during transition is calculated using the following formula:

[0108] Second target rotation angle compensation angle*(1-gain coefficient K)-first target rotation angle compensation angle*gain coefficient K;

[0109] The gain coefficient K is calculated based on the first target rotation angle compensation angle and the second target rotation angle compensation angle.

[0110] In another embodiment, if the current compensation angle adopts the first target rotation angle compensation angle in step S620, that is, the above-mentioned working condition 2, transitioning the current compensation angle adopted from one of the first target rotation angle compensation angle and the second target rotation angle compensation angle to the other of the first target rotation angle compensation angle and the second target rotation angle compensation angle includes:

[0111] The target compensation angle during transition is calculated using the following formula:

[0112] Second target rotation angle compensation angle*gain coefficient K-first target rotation angle compensation angle*(1-gain coefficient K);

[0113] When the target angle control system decelerates from a high speed state (usually using the second target angle compensation angle) to a low speed state, the formula second target angle compensation angle * (1-gain coefficient K) - first target angle compensation angle * gain coefficient K can be used to ensure that the steering compensation angle is smoothly reduced to a compensation angle suitable for low speed (first target angle compensation angle). This smooth deceleration maintains the stability and controllability of the target angle control system. Sudden changes in steering angle may cause unnecessary shock to the target angle control system and passengers. By gradually adjusting the compensation angle, this shock can be reduced and driving comfort can be improved.

[0114] When the target angle control system accelerates from a low speed state (usually using the first target angle compensation angle) to a high speed state, the formula second target angle compensation angle * gain coefficient K-first target angle compensation angle * (1-gain coefficient K) can be used to ensure that the steering compensation angle is smoothly increased to a compensation angle suitable for high speed (second target angle compensation angle). During the acceleration process, if the steering compensation angle increases suddenly, it may cause the target angle control system to lose control. By gradually increasing the compensation angle, the system can ensure the continuity of steering performance, thereby improving driving safety.

[0115] Since the gain coefficient K can be adjusted according to different working conditions, it ensures that the best steering performance can be provided when switching from low speed to high speed, or from high speed to low speed.

[0116] In one embodiment of the present invention, the first target turning angle compensation angle is calculated according to the current vehicle speed value and the target turning angle in step S30, including:

[0117] The first target rotation angle compensation angle is obtained by the following formula:

[0118]

[0119]

[0120] Among them, a0 = k1k2lu 2;a1=k1k2blu;a2=-k1I z u 2 ; b1=-(k1+k2)I z u-(a 2 k1+b 2 k2)mu; b2=mI z u 2 ; b0 = l 2 k1k2-(ak1-bk2)mu 2 ; δ f =ne;

[0121] δ f_lowSpeedcmp is the first target turning angle compensation angle; m is the vehicle mass; l is the distance from the front axle to the rear axle; γ is the yaw rate; δ f is the front wheel turning angle; n is the proportional factor; e is the target turning angle; a is the distance from the center of mass to the front axle; b is the distance from the center of mass to the rear axle; u is the current vehicle speed; I z is the target steering angle control system's moment of inertia around the z-axis; k1 is the front tire cornering stiffness; k2 is the rear tire cornering stiffness; a y (s) is a transfer function, and s is a complex variable in the transfer function.

[0122] The derivation process of the above formula (2) is as follows:

[0123] Select two state variables, the sideslip angle of the center of mass and the yaw rate, and list the dynamic equation as:

[0124]

[0125] Where β is the sideslip angle of the center of mass, and the other parameters have been explained above. From formula (1), the transfer function of the lateral acceleration of the steer-by-wire system and the first target steering angle compensation angle can be obtained, as well as the above formula (2).

[0126] In an optional manner, the corresponding relationship between the steering wheel angle and the target lateral acceleration of the embodiment of the present invention is set as follows: Figure 8 :

[0127] Then, the target lateral acceleration (m / s 2 ) y =a ymax * Steering wheel angle;

[0128] The target lateral acceleration is the lateral acceleration value that the vehicle is expected to achieve in the design or control strategy, and is used to guide the vehicle's steering behavior. The actual lateral acceleration is the lateral acceleration actually generated by the vehicle during driving, which may deviate from the target lateral acceleration due to various factors (such as road conditions, vehicle load, tire characteristics, etc.). In order to reduce this deviation, it is necessary to introduce a compensation amount, namely the compensating lateral acceleration, to adjust the vehicle's steering behavior to make it closer to the target lateral acceleration. y (0)) Response As a general response, the target and actual lateral acceleration a y (s) The difference in response is compensated, and the compensated lateral acceleration is:

[0129] a y_lowSpeedcmp ={a y (s)-a y (0)}δ f (4)

[0130] Assume the first target angle compensation angle is δ f_lowSpeedcmp , then:

[0131] a y_lowSpeedcmp =a y (s)δ f_lowSpeedcmp (5)

[0132] Therefore, it can be deduced that the first target angle compensation angle for low speed is:

[0133]

[0134] That is the above formula (1).

[0135] Further, in the embodiment of the present invention, calculating the second target turning angle compensation angle according to the current vehicle speed value and the target turning angle includes:

[0136] The second target rotation angle compensation angle is obtained by the following formula:

[0137]

[0138]

[0139] Among them, a0 = k1k2lu 2 ;a1=k1k2blu;a2=-k1I z u 2 ; b1=-(k1+k2)I z u-(a 2 k1+b 2 k2)mu; b2=mI z u 2 ; b0 = l 2k1k2-(ak1-bk2)mu 2 ; δ f =n;

[0140] δ f_highSpeedcmp is the second target turning angle compensation angle; m is the vehicle mass; l is the distance from the front axle to the rear axle; β is the sideslip angle of the center of mass; γ is the yaw rate; δ f is the front wheel turning angle; n is the proportional factor; e is the target turning angle; a is the distance from the center of mass to the front axle; b is the distance from the center of mass to the rear axle; u is the current vehicle speed; I z is the moment of inertia of the target steering angle control system around the z-axis; k1 is the cornering stiffness of the front tire; k2 is the cornering stiffness of the rear tire; ay(s) is the transfer function, and s is the complex variable in the transfer function.

[0141] The calculation of high-speed target angle compensation is similar to that of low-speed target angle compensation. The actual high-speed lateral acceleration can be expressed as the above formula (6) according to experience. Set the high-speed target lateral acceleration (a y (0)), then the second target steering angle compensation angle for high speed can be calculated according to the above formula (4) as formula (7).

[0142] Of course, the relevant coefficients in formula (6) can be replaced equivalently according to the actual measurement situation, such as replacing 0.7 with 0.6, etc.; this should also fall within the scope of protection covered by this application.

[0143] like Fig. 9 To illustrate the present solution more clearly, a target turning angle control method based on wire control steering is provided in a specific embodiment, and its control logic is as follows:

[0144] a. When the steering is triggered, compensation control begins;

[0145] Determine the current working condition based on the current vehicle speed value: b1, the current vehicle speed value changes from low speed to high speed; if yes, enter c1, if no, enter b2;

[0146] b2, the current vehicle speed value changes from high to low speed. If yes, enter c2, otherwise enter the above working conditions 3 and 4;

[0147] b1 and b2 are the "determining whether the current vehicle speed value reaches the target threshold value during the turning process" described in the above step S610.

[0148] c1, control the first target rotation angle compensation angle to compensate; then enter d1;

[0149] d1, determine whether the current vehicle speed reaches the target threshold; if so, enter e1, otherwise enter c1 loop;

[0150] c2. Control the second target rotation angle compensation angle for compensation;

[0151] d2, determine whether the current vehicle speed reaches the target threshold; then enter d2; if so, enter e2, otherwise enter c2 loop;

[0152] c1~d1 and c2~d2 are the "if the target threshold is reached, the current compensation angle used is compensated from one of the first target angle compensation angle and the second target angle compensation angle" stated in the above step S620.

[0153] e1, the current compensation angle transitions from the first target angle compensation angle to the second target angle compensation angle. At this time, the current compensation angle is the second target angle compensation angle * gain coefficient K - first target angle compensation angle * (1 - gain coefficient K), and then enters f1;

[0154] f1, determine whether the gain coefficient K is less than the transition switching threshold; if not, enter e1 loop, if so, enter g1;

[0155] e2, the current compensation angle transitions from the second target angle compensation angle to the first target angle compensation angle. At this time, the current compensation angle is the second target angle compensation angle*(1-gain coefficient K)-first target angle compensation angle*gain coefficient K, and then enters f2;

[0156] f2, determine whether the gain coefficient K is less than the transition switching threshold; if not, enter e2 loop, if so, enter g2;

[0157] e1-f1 and e2-f2 refer to the transition process described in the above step S620 and the determination in step S630 whether the excessive stop condition is satisfied.

[0158] g1, control the second target angle compensation angle for compensation;

[0159] g2, control the first target rotation angle compensation angle for compensation;

[0160] g1-g2 are the compensation angles after the transition stops as described in the above step S640, and the compensation angles after the transition are used as the current compensation angles.

[0161] h. Stop compensation control at the end of steering.

[0162] In the embodiment of the present invention, the control process takes into account two vehicle speed change conditions: from low to high and from high to low, and designs corresponding compensation strategies, so that the vehicle can maintain good steering performance under various working conditions, especially when the high-speed and low-speed transitions, the lateral angular velocity can be better reduced to improve the stability of the focus. The introduction of the gain coefficient K and the setting of the transition switching threshold make the adjustment of the compensation angle smoother and more precise, which helps to improve the adaptability of the system.

[0163] like Fig.10 A control topology diagram with logic nodes for a target angle control system based on steer-by-wire is provided. In another aspect of the present application, a target angle control system is provided, comprising:

[0164] The gear target angle module 10 obtains the current vehicle speed value and the steering wheel angle, and calculates the gear target angle according to the current vehicle speed value and the steering wheel angle;

[0165] The target angle compensation module 20 is electrically connected to the gear target angle module, and the gear target angle module is configured to execute the above target angle control method based on steer-by-wire.

[0166] Obviously, the target angle control system has all the beneficial effects brought by the above method, such as better steering experience, etc., which will not be repeated here.

[0167] The various technical features described above can be combined arbitrarily. Although all possible combinations of these technical features are not described, any combination of these technical features should be considered to be covered by this specification as long as there is no contradiction in such combination.

[0168] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still adjust the technical solutions described in the aforementioned embodiments, or replace some or all of the embedded technical features with equivalent ones. However, these adjustments or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A target angle control method based on wire control steering, characterized in that: include: Obtain the current vehicle speed value and gear target angle of the target angle control system during steering; Calculate a first target rotation angle compensation angle and a second target rotation angle compensation angle according to the current vehicle speed value and the gear target rotation angle; Determine, according to the current vehicle speed value, to use one of the first target steering angle compensation angle and the second target steering angle compensation angle as a current compensation angle; The gear target rotation angle is compensated using the current compensation angle.

2. The target turning angle control method according to claim 1, characterized in that: The step of determining, according to the current vehicle speed value, to use one of the first target steering angle compensation angle and the second target steering angle compensation angle as the current compensation angle comprises: Determining whether the current vehicle speed value is lower than a target threshold; If it is lower than the target threshold, the first target rotation angle compensation angle is used as the current compensation angle; otherwise, the second target rotation angle compensation angle is used as the current compensation angle.

3. The target turning angle control method according to claim 1, characterized in that: The method further comprises: During the steering process, determine whether the current vehicle speed value reaches the target threshold; If the target threshold is reached, the current compensation angle used is transitioned from one of the first target rotation angle compensation angle and the second target rotation angle compensation angle to the other of the first target rotation angle compensation angle and the second target rotation angle compensation angle; Determine whether the transition stop condition is met; When the transition stop condition is met, the compensation angle after the transition is used as the current compensation angle.

4. The target turning angle control method according to claim 3, characterized in that: The determining whether the transition stop condition is met includes: Calculating a gain coefficient K according to the first target rotation angle compensation angle and the second target rotation angle compensation angle; Determining whether the gain coefficient is less than a transition switching threshold; If the gain coefficient is less than the transition switching threshold, it is determined that the transition stop condition is met.

5. The target turning angle control method according to claim 4, characterized in that: The step of calculating the gain coefficient K according to the first target rotation angle compensation angle and the second target rotation angle compensation angle comprises: Calculating an absolute value of a difference between the first target rotation angle compensation angle and the second target rotation angle compensation angle; The corresponding gain coefficient K is determined according to the absolute value of the difference.

6. The target turning angle control method according to claim 5, characterized in that: Determining the corresponding gain coefficient K according to the absolute value of the difference comprises: When the absolute value of the difference is less than a first threshold, a fixed value K1 is used as the gain coefficient K; When the absolute value of the difference is greater than a second threshold, a fixed value K2 is used as the gain coefficient K; When the absolute value of the difference is between the first threshold and the second threshold, the K3 value is determined as the gain coefficient K by using a preset linear relationship between the absolute value of the difference and the gain coefficient.

7. The target turning angle control method according to any one of claims 3 to 6, characterized in that: If the current compensation angle adopts the first target rotation angle compensation angle, the step of transitioning the current compensation angle adopted from one of the first target rotation angle compensation angle and the second target rotation angle compensation angle to the other of the first target rotation angle compensation angle and the second target rotation angle compensation angle comprises: Use the following formula to calculate the current compensation angle during transition: Second target rotation angle compensation angle*gain coefficient K-first target rotation angle compensation angle*(1-gain coefficient K); If the current compensation angle adopts the second target rotation angle compensation angle, the step of transitioning the current compensation angle adopted from one of the first target rotation angle compensation angle and the second target rotation angle compensation angle to the other of the first target rotation angle compensation angle and the second target rotation angle compensation angle comprises: Use the following formula to calculate the current compensation angle during transition: Second target rotation angle compensation angle*(1-gain coefficient K)-first target rotation angle compensation angle*gain coefficient K The gain coefficient K is calculated based on the first target steering angle compensation angle and the second target steering angle compensation angle.

8. The target turning angle control method according to any one of claims 1 to 6, characterized in that: The calculating the first target turning angle compensation angle according to the current vehicle speed value and the target turning angle includes: The first target rotation angle compensation angle is obtained by the following formula: where a0 = k1k2lu 2 ; a1 = k1k2blu; a2 = -k1I z u 2 ; b1 = -(k1 + k2)I z u-(a 2 k1 + b 2 k2)mu; b2 = mI z u 2 ; b0 = l 2 k1k2-(ak1 - bk2)mu 2 ; δ f = ne; δ f_lowSpeedcmp is the first target steering angle compensation angle; m is the vehicle mass; l is the distance from the front axle to the rear axle; β is the sideslip angle of the center of mass; γ is the yaw rate; δ f is the front wheel turning angle; n is the proportional factor; e is the target turning angle; a is the distance from the center of mass to the front axle; b is the distance from the center of mass to the rear axle; u is the current vehicle speed; I z is the moment of inertia of the target steering angle control system around the z-axis; k1 is the cornering stiffness of the front tire; k2 is the cornering stiffness of the rear tire; ay(s) is the transfer function, and s is the complex variable in the transfer function.

9. The target turning angle control method according to any one of claims 1 to 6, characterized in that: The calculating the second target turning angle compensation angle according to the current vehicle speed value and the target turning angle includes: The second target rotation angle compensation angle is obtained by the following formula: Among them, a0=k1k2lu 2 ;a1=k1k2blu;a2=-k1I z u 2 ; b1 = -(k1 + k2)I z u-(a 2 k1+b 2 k2)mu; b2=mI z u 2 ; b0 = l 2 k1k2-(ak1-bk2)mu 2 ; δ f = n; δ f_highSpeedcmp is the second target turning angle compensation angle; m is the vehicle mass; l is the distance from the front axle to the rear axle; β is the sideslip angle of the center of mass; γ is the yaw rate; δ f is the front wheel turning angle; n is the proportional factor; e is the target turning angle; a is the distance from the center of mass to the front axle; b is the distance from the center of mass to the rear axle; u is the current vehicle speed; I z is the moment of inertia of the target steering angle control system around the z-axis; k1 is the cornering stiffness of the front tire; k2 is the cornering stiffness of the rear tire; ay(s) is the transfer function, and s is the complex variable in the transfer function.

10. A target angle control system, characterized in that: include: The gear target angle module obtains the current vehicle speed value and the steering wheel angle, and calculates the gear target angle according to the current vehicle speed value and the steering wheel angle; A target angle compensation module is electrically connected to the gear target angle module, and the gear target angle module is configured to execute the target angle control method based on wire control according to any one of claims 1 to 9.

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