Active return-to-center control methods, electric power steering systems, and automobiles

Abstract

This invention discloses an active self-centering control method, an electric power steering system, and a vehicle. The method includes: acquiring actual vehicle data, including actual vehicle speed and actual steering wheel angle; obtaining a first target self-centering speed based on the actual vehicle speed and the actual steering wheel angle; smoothing the first target self-centering speed to obtain a second target self-centering speed; and performing active self-centering control based on the second target self-centering speed. This method can achieve both a small self-centering residual angle after the steering wheel passes the midpoint and avoid sudden changes in steering torque after the steering wheel passes the midpoint.

Description

Technical Field

[0001] This invention relates to the field of automotive electronic control technology, and in particular to an active self-centering control method, an electric power steering system, and an automobile. Background Technology

[0002] Electric Power Steering (EPS) is a power steering system that directly relies on an electric motor to provide auxiliary torque. EPS mainly consists of a torque sensor, vehicle speed sensor, motor, reduction gear, and electronic control unit (ECU). EPS uses the motor and reduction gear to assist the driver in overcoming the resistance generated during steering. However, compared to traditional hydraulic power steering (HPS), the use of the motor and reduction gear significantly increases the internal friction of the EPS. This makes it difficult for the steering wheel to automatically return to the center position when driving, resulting in a large residual return angle. Generally, when the residual return angle exceeds a certain threshold (e.g., 5°), the driver needs to manually adjust the steering wheel to return it to near the center position, increasing the driver's workload. This center position refers to the position close to the 0° steering angle.

[0003] Existing EPS (Electric Power Steering) active self-centering control incorporates a target self-centering speed and the actual steering wheel speed. The control process presents two scenarios: First, when the target self-centering speed is relatively high in the small turning angle region, it ensures a small residual self-centering angle after the driver releases the steering wheel. However, when the driver maneuvers the steering wheel past the center position and turns to the other side, the speed difference between the target self-centering speed and the actual steering wheel speed causes a sudden change in steering torque when the steering wheel passes the center position. Second, when the target self-centering speed is relatively low in the small turning angle region, it avoids a sudden change in steering torque when the steering wheel passes the center position. However, because the target self-centering speed is low, it is difficult for the steering wheel to continue returning to the center position after reaching a 5° turning angle, resulting in a large residual self-centering angle during the steering wheel's self-centering process. Therefore, there is an urgent need for an active self-centering control method that can balance the residual self-centering angle and sudden changes in steering torque. Summary of the Invention

[0004] This invention provides an active self-centering control method, an electric power steering system, and a vehicle, in order to achieve the goal of reducing the self-centering residual angle and avoiding sudden changes in steering torque.

[0005] This invention provides an active self-alignment control method, comprising:

[0006] Acquire actual vehicle data, including actual vehicle speed and actual steering wheel angle;

[0007] The first target return-to-center speed is obtained based on the actual vehicle speed and the actual steering wheel angle.

[0008] The first target return speed is smoothed to obtain the second target return speed.

[0009] Active return-to-center control is performed based on the second target return-to-center speed.

[0010] Further, the step of smoothing the first target return-to-center speed to obtain the second target return-to-center speed includes:

[0011] Determine the smoothing correction coefficient based on the actual steering wheel angle;

[0012] The smoothing correction coefficient is used to smooth the first target homing speed to obtain the second target homing speed.

[0013] Furthermore, the actual vehicle data also includes the actual steering wheel rotation speed;

[0014] The step of smoothing the first target return speed to obtain the second target return speed includes:

[0015] Determine the smoothing correction coefficient based on the actual steering wheel angle and the actual steering wheel speed;

[0016] The smoothing correction coefficient is used to smooth the first target homing speed to obtain the second target homing speed.

[0017] Further, determining the smoothing correction coefficient based on the actual steering wheel angle and the actual steering wheel rotation speed includes:

[0018] The smoothing correction variable is determined by multiplying the actual steering wheel angle and the actual steering wheel speed.

[0019] The smoothing correction coefficient is determined by consulting the smoothing correction coefficient lookup table based on the smoothing correction variable.

[0020] Furthermore, if the smoothing correction variable is positive, then the smoothing correction coefficient is inversely proportional to the smoothing correction variable, and the minimum threshold of the correction coefficient is less than the smoothing correction coefficient and the critical threshold of the correction coefficient.

[0021] If the smoothing correction variable is negative, then the smoothing correction coefficient is proportional to the absolute value of the smoothing correction variable, and the critical threshold of the correction coefficient is less than the smoothing correction coefficient, which is less than the maximum threshold of the correction coefficient.

[0022] Furthermore, the actual vehicle data also includes the actual steering wheel rotation speed;

[0023] The active return-to-center control based on the second target return-to-center speed includes:

[0024] The target speed difference is determined based on the second target return speed and the actual speed of the steering wheel;

[0025] Based on the target speed difference, determine the active return torque control amount;

[0026] Active return-to-center control is performed based on the active return-to-center torque control amount.

[0027] Furthermore, the actual vehicle data also includes the driver's steering torque;

[0028] The active return-to-center control based on the active return-to-center torque control amount includes:

[0029] Based on the actual steering wheel angle and the driver's steering torque, the active return torque control amount is corrected to determine the target return torque control amount;

[0030] Active return-to-center control is performed based on the target return-to-center torque control value.

[0031] Further, the step of correcting the active return torque control amount based on the actual steering wheel angle and the driver's steering torque to determine the target return torque control amount includes:

[0032] The first control coefficient is determined by consulting the steering angle correction coefficient table based on the actual steering wheel angle.

[0033] The second control quantity coefficient is determined by consulting the torque correction coefficient table based on the driver's steering torque.

[0034] Based on the first control coefficient and the second control coefficient, the active return torque control quantity is corrected to determine the target return torque control quantity.

[0035] This invention provides an electric power steering system, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the active return-to-center control method described above.

[0036] This invention provides an electric power steering system that enables a smoother change in the target return speed over time during the steering wheel return control process.

[0037] This invention provides a vehicle including the above-described electric power steering system.

[0038] The aforementioned active self-centering control method, electric power steering system, and vehicle obtain a first target self-centering speed based on the actual vehicle speed and the actual steering wheel angle, ensuring a small self-centering residual angle. By smoothing the first target self-centering speed to obtain a second target self-centering speed, it is ensured that there will be no sudden change in steering torque when the steering wheel passes through the middle position. Thus, active self-centering control based on the second target self-centering speed can achieve the goal of balancing a small self-centering residual angle when the steering wheel passes through the middle position and avoiding sudden changes in steering torque when the steering wheel passes through the middle position. Attached Figure Description

[0039] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0040] Figure 1 This is a flowchart of an active homing control method according to an embodiment of the present invention;

[0041] Figure 2 This is another flowchart of the active homing control method in one embodiment of the present invention;

[0042] Figure 3 This is another flowchart of the active homing control method in one embodiment of the present invention;

[0043] Figure 4 This is another flowchart of the active homing control method in one embodiment of the present invention;

[0044] Figure 5 This is another flowchart of the active homing control method in one embodiment of the present invention;

[0045] Figure 6 This is another flowchart of the active homing control method in one embodiment of the present invention;

[0046] Figure 7 This is another flowchart of the active homing control method in one embodiment of the present invention;

[0047] Figure 8 This is a schematic diagram of a target return speed mapping table in one embodiment of the present invention;

[0048] Figure 9 This is a schematic diagram of a smoothing correction coefficient lookup table in one embodiment of the present invention;

[0049] Figure 10 This is a comparison diagram of an embodiment of the present invention and the prior art for calculating the target rotational speed difference;

[0050] Figure 11 This is a schematic diagram of a rotation angle correction coefficient table in one embodiment of the present invention;

[0051] Figure 12 This is a schematic diagram of a torque correction coefficient table in one embodiment of the present invention. Detailed Implementation

[0052] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0053] The active self-centering control method provided in this embodiment of the invention can be applied to automobiles equipped with EPS. The active self-centering control is achieved by EPS, which can reduce the self-centering residual angle when the steering wheel passes through the middle position and avoid sudden changes in steering torque when the steering wheel passes through the middle position.

[0054] In one embodiment, such as Figure 1 As shown, an active self-alignment control method is provided. Taking the application of this method in EPS as an example, the method includes the following steps:

[0055] S101: Obtain actual vehicle data, including actual vehicle speed and actual steering wheel angle;

[0056] S102: Obtain the first target return-to-center speed based on the actual vehicle speed and the actual steering wheel angle;

[0057] S103: Smooth the first target return speed to obtain the second target return speed;

[0058] S104: Perform active return-to-center control based on the second target return-to-center speed.

[0059] Here, actual vehicle data refers to the vehicle data actually measured at the current moment. As an example, actual vehicle data includes, but is not limited to, actual vehicle speed, actual steering wheel angle, actual steering wheel speed, and driver steering torque. Actual vehicle speed refers to the vehicle speed measured at the current moment, which can be represented by SPD. Actual steering wheel angle refers to the steering wheel rotation angle actually measured at the current moment, which can be represented by SWA. Actual steering wheel speed refers to the steering wheel rotation speed actually measured at the current moment, which can be represented by SWV. Driver steering torque refers to the torque exerted by the driver when operating the steering wheel at the current moment, which can be represented by Th.

[0060] As an example, in step S101, the EPS acquires real-time vehicle data during vehicle operation to perform active return-to-center control based on this data. In this example, the vehicle data includes, but is not limited to, the actual vehicle speed SPD acquired via the vehicle's bus, the actual steering wheel angle SWA and actual steering wheel speed SWV acquired via the steering angle sensor, and the driver's steering torque Th acquired via the torque sensor. Specifically, after the steering angle sensor acquires the actual steering wheel angle SWA, it performs a differential operation on the actual steering wheel angle SWA to obtain the actual steering wheel speed SWV.

[0061] The first target return-to-center speed is calculated based on the actual vehicle speed and the actual steering wheel angle, and is used to achieve active return-to-center control. It can be represented by SWV_target.

[0062] As an example, in step S102, after acquiring the actual vehicle data, the EPS can use a pre-set target return speed determination logic to calculate the actual vehicle speed SPD and the actual steering wheel angle SWA to obtain the first target return speed SWV_target. This target return speed determination logic is a pre-set processing logic for determining the target return speed based on the actual vehicle speed SPD and the actual steering wheel angle SWA, including but not limited to logic used in the prior art for determining the target return speed. In this example, the process of determining the first target return speed SWV_target based on the actual vehicle speed SPD and the actual steering wheel angle SWA needs to ensure that the first target return speed SWV_target satisfies the objective of having a small residual return angle.

[0063] In one specific implementation, after acquiring the actual vehicle data, the EPS can query a pre-set target return speed mapping table based on the actual vehicle speed SPD and the actual steering wheel angle SWA. From the target return speed mapping table, it obtains the first target return speed SWV_target that matches the actual vehicle speed SPD and the actual steering wheel angle SWA. Figure 8 As shown, the target return speed mapping table is a three-dimensional chart used to reflect the mapping relationship between "vehicle speed - steering angle - target return speed". This target return speed mapping table is a three-dimensional chart that has been tested in advance to ensure that it can meet the requirement of a small return residual angle, so as to ensure that the first target return speed SWV_target determined according to the actual vehicle speed SPD and the actual steering wheel angle SWA can meet the purpose of a small return residual angle.

[0064] The second target homing speed is the speed used to achieve active homing control after the first target homing speed has been smoothed. It can be represented by SWV_target_smoothed.

[0065] As an example, in step S103, after obtaining the first target return-to-center speed, the EPS can use a pre-set smoothing logic to smooth the first target return-to-center speed and obtain the second target return-to-center speed. This second target return-to-center speed can then be used for subsequent active return-to-center control. Since the second target return-to-center speed changes more smoothly over time during the active return-to-center control process, it can avoid sudden changes in steering torque when the steering wheel passes through the middle position. The middle position refers to the position close to the 0° steering angle of the steering wheel. The small steering angle region refers to the position close to the 0° steering angle of the steering wheel, that is, the range formed by turning a specific angle to the left or right with the 0° steering angle position of the steering wheel as the center. For example, with the 0° steering angle position of the steering wheel as the center, left is the negative direction and right is the positive direction. The specific angle is 5°. Then, when the steering wheel returns to center from left to right, the corresponding small steering angle region is [-5°, 0°], and when the steering wheel returns to center from right to left, the corresponding small steering angle region is [0°, 5°].

[0066] As an example, in step S104, after obtaining the second target return-to-center speed, the EPS can control the motor and reduction mechanism to provide assistance and perform active return-to-center control based on the second target return-to-center speed. Understandably, since the second target return-to-center speed is a smoothed version of the first target return-to-center speed, it ensures that there will be no sudden change in steering torque when the steering wheel passes the center position. Therefore, by ensuring that the residual return-to-center angle is small during the process of obtaining the first target return-to-center speed based on the actual vehicle speed and the actual steering wheel angle, the goal of both reducing the residual return-to-center angle when the steering wheel passes the center position and avoiding sudden changes in steering torque when the steering wheel passes the center position can be achieved.

[0067] The active self-centering control method provided in this invention obtains a first target self-centering speed based on the actual vehicle speed and the actual steering wheel angle, which ensures that the residual self-centering angle is small. By smoothing the first target self-centering speed, a second target self-centering speed is obtained, which ensures that there will be no sudden change in steering torque when the steering wheel passes through the middle position. Thus, active self-centering control based on the second target self-centering speed can achieve the goal of balancing a small residual self-centering angle when the steering wheel passes through the middle position and avoiding sudden changes in steering torque when the steering wheel passes through the middle position.

[0068] In one embodiment, such as Figure 2 As shown, step S103, which involves smoothing the first target return speed to obtain the second target return speed, includes:

[0069] S201: Determine the smoothing correction coefficient based on the actual steering wheel angle;

[0070] S202: Using a smoothing correction coefficient, the first target homing speed is smoothed to obtain the second target homing speed.

[0071] The actual steering wheel angle refers to the angle of rotation of the steering wheel actually measured at the current moment, which can be represented by SWA. The smoothing correction coefficient is a coefficient used to smooth the first target return speed.

[0072] As an example, in step S201, after obtaining the first target return speed, the EPS can use a smoothing correction coefficient function to calculate the variable parameter of the actual steering wheel angle SWA. Specifically, it can calculate the smoothing correction coefficient by combining the actual steering wheel angle SWA with constant variables; alternatively, it can calculate the smoothing correction coefficient by combining the actual steering wheel angle SWA with other actual vehicle data and constant variables. The smoothing correction coefficient function is a pre-set function used to calculate the smoothing correction coefficient. This function can use only the actual steering wheel angle SWA as a variable parameter, or it can use the actual steering wheel angle SWA with other parameters (including but not limited to the actual steering wheel speed SWV) as variable parameters.

[0073] As an example, in step S202, after obtaining the smoothing correction coefficient, the EPS can use this coefficient to smooth the first target return-to-center speed to obtain the second target return-to-center speed. This allows for subsequent active return-to-center control of the motor and reduction mechanism based on the second target return-to-center speed. In this example, the smoothing correction coefficient is inversely proportional to the actual steering wheel angle SWA. For instance, when the actual steering wheel angle SWA is in the large angle region, the smoothing correction coefficient is larger, resulting in a larger second target return-to-center speed and faster return-to-center. Conversely, when the actual steering wheel angle SWA is in the small angle region, the smoothing correction coefficient is smaller, resulting in a smaller second target return-to-center speed and preventing sudden changes in steering torque when the steering wheel returns to center past the 0° steering wheel position. Among them, the large corner area refers to the corner area that is greater than the critical corner threshold (for example, the area with a corner angle greater than 5°), and the small corner area refers to the corner area that is not greater than the critical corner threshold (for example, the area with a corner angle less than or equal to 5°). The critical corner threshold is a pre-set corner threshold used to distinguish between the large corner area and the small corner area, and can be set to a corner angle of 5°.

[0074] Understandably, since the first target return speed is determined by the actual vehicle speed and the actual steering wheel angle, it can ensure that the return angle of the steering wheel after returning to the center position is small. Meanwhile, the smoothing correction coefficient is determined by the actual steering wheel angle, which can avoid sudden changes in steering torque when the steering wheel returns to the center position. Thus, the goal of reducing the return angle of the steering wheel after returning to the center position and avoiding sudden changes in steering torque when the steering wheel returns to the center position is achieved.

[0075] In one embodiment, the actual vehicle data also includes the actual steering wheel rotation speed;

[0076] like Figure 3 As shown, step S103, which involves smoothing the first target return speed to obtain the second target return speed, includes:

[0077] S301: Determine the smoothing correction coefficient based on the actual steering wheel angle and the actual steering wheel speed;

[0078] S302: Using a smoothing correction coefficient, the first target homing speed is smoothed to obtain the second target homing speed.

[0079] The actual steering wheel rotation speed refers to the actual measured rotation speed of the steering wheel at the current moment, which can be represented by SWV. The smoothing correction coefficient is a coefficient used to smooth the first target return-to-center speed, which can be represented by K.

[0080] As an example, in step S301, after obtaining the first target return speed, the EPS can process the actual steering wheel angle SWA and actual steering wheel speed SWV from the vehicle's actual data as input variable parameters to determine their smoothing correction coefficients. The smoothing correction coefficient function is a pre-set function used to calculate the smoothing correction coefficients. This function can use the actual steering wheel angle SWA and actual steering wheel speed SWV as variable parameters, and may also include other variable parameters.

[0081] As an example, in step S302, after obtaining the smoothing correction coefficient K, EPS can use this smoothing correction coefficient K to smooth the first target recovery speed. Specifically, the product of the first target recovery speed and the smoothing correction coefficient is determined as the second target recovery speed (i.e.,

[0082] SWV_target_smoothed = SWV_target * K) is used so that the motor and reduction mechanism can be actively controlled to return to center based on the second target return speed.

[0083] Understandably, since the first target return-to-center speed is determined by the actual vehicle speed and the actual steering wheel angle, it ensures that the residual return-to-center angle after the steering wheel returns to the center position is small. The smoothing correction coefficient is determined by the actual steering wheel angle and the actual steering wheel speed, so that the corrected second target return-to-center speed is controlled by the actual steering wheel angle and the actual steering wheel speed. During the active return-to-center control of the steering wheel, the return-to-center control process is based on the second target return-to-center speed. This ensures that the steering wheel speed during the return-to-center process is reasonable and stable, avoiding sudden changes in steering torque when the steering wheel returns to the center position. Thus, it achieves the goal of reducing the residual return-to-center angle after the steering wheel returns to the center position and avoiding sudden changes in steering torque when the steering wheel returns to the center position.

[0084] In one embodiment, such as Figure 4 As shown, step S301, which involves determining the smoothing correction coefficient based on the actual steering wheel angle and actual steering wheel speed, includes:

[0085] S401: The product of the actual steering wheel angle and the actual steering wheel speed is used to determine the smoothing correction variable;

[0086] S401: Determine the smoothing correction coefficient by consulting the smoothing correction coefficient lookup table based on the smoothing correction variable.

[0087] Among them, the smoothing correction variable is an intermediate variable determined based on the actual steering wheel angle and the actual steering wheel speed.

[0088] As an example, in step S401, after obtaining the actual steering wheel angle and actual steering wheel speed, EPS can determine the product of the actual steering wheel angle and actual steering wheel speed as a smoothing correction variable. This smoothing correction variable serves as an intermediate variable for subsequently calculating the smoothing correction coefficient. Alternatively, the product of the actual steering wheel angle and actual steering wheel speed can be calculated first, and this product can be used together with other constant variables to calculate the smoothing correction variable.

[0089] The smoothing correction coefficient lookup table is a pre-set lookup table used to query and determine the smoothing correction coefficient. In this example, the smoothing correction coefficient lookup table is formed based on a pre-set smoothing correction coefficient function, which specifically uses the product of the actual steering wheel angle and the actual steering wheel speed (i.e., the smoothing correction variable) as the variable parameter.

[0090] As an example, in step S402, EPS uses the smoothing correction variable formed by the product of the actual steering wheel angle and the actual steering wheel speed to look up a pre-determined smoothing correction coefficient lookup table, which can quickly and accurately determine the smoothing correction coefficient. This smoothing correction coefficient is then used to correct the first target return speed. That is, the product of the first target return speed and the smoothing correction coefficient is determined as the second target return speed, i.e., SWV_target_smoothed=SWV_target*f(SWA*SWV). This ensures that the steering wheel speed is reasonable and stable during the return process, and avoids sudden changes in steering torque when the steering wheel returns to the center position. This achieves the goal of reducing the return residual angle of the steering wheel when it passes the center position and avoiding sudden changes in steering torque when the steering wheel passes the center position.

[0091] Traditional active self-centering control struggles to achieve a good balance between residual self-centering angle and sudden changes in steering torque. Traditional methods, by increasing the target self-centering speed in the small steering angle region, can reduce the residual self-centering angle, but this leads to a significant sudden change in steering torque when the steering wheel passes the center position. Conversely, decreasing the target self-centering speed in the small steering angle region avoids this sudden change, but results in a larger residual self-centering angle. Therefore, a reasonable setting of the target self-centering speed is necessary to balance these two factors. This solution employs a smoothing correction coefficient to smoothly correct the first target self-centering speed. Specifically, the smoothing correction coefficient is formed by multiplying the actual steering wheel angle and the actual steering wheel speed. This corrected second target self-centering speed avoids sudden changes in steering torque. By ensuring that the target self-centering speed meets the requirements for the residual self-centering angle, both factors can be balanced. In other words, when EPS performs active self-centering control, it only needs to ensure that the first target self-centering speed determined based on the actual vehicle speed and the actual steering wheel angle meets the requirements of the self-centering residual angle. Since the second target self-centering speed formed by using a smoothing correction coefficient to smoothly correct the first target self-centering speed can avoid sudden changes in steering torque, it can achieve both self-centering residual angle and sudden changes in steering torque.

[0092] In one embodiment, such as Figure 9 As shown, if the smoothing correction variable is positive, the smoothing correction coefficient is inversely proportional to the smoothing correction variable, with the minimum threshold of the correction coefficient < the smoothing correction coefficient < the critical threshold of the correction coefficient; if the smoothing correction variable is negative, the smoothing correction coefficient is directly proportional to the absolute value of the smoothing correction variable, with the critical threshold of the correction coefficient < the smoothing correction coefficient < the maximum threshold of the correction coefficient.

[0093] Among them, the minimum threshold of the correction coefficient is the minimum threshold corresponding to the smooth correction coefficient, which can be set to 0. The maximum threshold of the correction coefficient is the maximum threshold corresponding to the smooth correction coefficient, which can be set to 1. The critical threshold of the correction coefficient is the threshold corresponding to the smooth correction coefficient used to limit the critical points corresponding to the steering operation and the return operation. The critical threshold of the correction coefficient can be set to a value close to the minimum threshold of the correction coefficient, for example, a value between 0.1 and 0.2.

[0094] In this example, the smoothing correction variable can be the product of the actual steering wheel angle and the actual steering wheel speed. When the smoothing correction variable is 0, it means that at least one of the actual steering wheel angle and actual steering wheel speed is 0, and the corresponding smoothing correction coefficient is the critical threshold. When the smoothing correction variable is positive (SWA*SWV>0), it means that the actual steering wheel angle and actual steering wheel speed are in the same direction, indicating that the driver is turning the steering wheel to perform a steering operation. When the smoothing correction variable is negative (SWA*SWV<0), it means that the actual steering wheel angle and actual steering wheel speed are in opposite directions, indicating that the driver is turning the steering wheel to return to center or releasing both hands to allow it to automatically return to center, performing a centering operation.

[0095] As an example, when the driver performs a steering operation, turning the steering wheel away from the center position, the smoothing correction variable is positive (SWA*SWV>0). The smoothing correction coefficient is a value between the minimum threshold and the critical threshold (e.g., between 0 and 0.1). Since this value is small, the second target return-to-center speed after correction based on this smoothing correction coefficient is also small, even close to 0. Therefore, active return-to-center control based on the second target return-to-center speed has little impact on the steering operation, essentially having no effect. When the smoothing correction variable is positive (SWA*SWV>0), the smoothing correction coefficient is inversely proportional to the smoothing correction variable. Specifically, the smoothing correction coefficient decreases as the smoothing correction variable increases, and increases as the smoothing correction variable decreases. In this example, the larger the smoothing correction variable, the larger the product of the actual steering wheel angle and the actual steering wheel speed, and the smaller the corresponding smoothing correction coefficient. This results in a smaller impact of active return-to-center control based on the second target return-to-center speed on the steering operation, making it easier for the driver to perform the steering operation. For example, when the actual steering wheel angle SWA is in the large steering angle region and the driver continues to increase the steering angle, the absolute value of the smoothing correction variable is relatively large, that is, the absolute value of SWA*SWV is relatively large. At this time, the smoothing correction coefficient is very small, and correspondingly, the absolute value of the second target return-to-center speed is very small (note that the target return-to-center speed is opposite to the actual speed at this time), and the driver can turn the steering wheel more easily. When the actual steering wheel angle SWA is in the small steering angle region, the absolute value of the smoothing correction variable is relatively small, that is, the absolute value of SWA*SWV is relatively small. At this time, the smoothing correction coefficient is still relatively small, and correspondingly, the second target return-to-center speed is relatively small, which can avoid the sudden change in steering torque when the steering wheel returns to center after passing the 0° steering angle position.

[0096] As an example, when a driver performs a centering maneuver, they need to turn the steering wheel gradually from a larger angle towards the center position. If the smoothing correction variable is negative (SWA*SWV<0), then the smoothing correction coefficient is a value between the critical threshold and the maximum threshold (e.g., a value between 0.1 and 1). The smoothing correction coefficient is directly proportional to the absolute value of the smoothing correction variable; specifically, the smoothing correction coefficient increases as the absolute value of the smoothing correction variable increases, and decreases as the absolute value of the smoothing correction variable decreases. For instance, when the driver turns the steering wheel to center, moving from a larger angle towards the center position, the smoothing correction variable is negative (SWA*SWV<0) and its absolute value is large. Therefore, the smoothing correction coefficient is large, and correspondingly, the absolute value of the second target centering speed is large (note that the target centering speed is in the same direction as the actual speed), causing the active centering control to assist in centering the steering wheel. When the driver turns the steering wheel back to center, moving from the center position to the 0° steering angle position, the smoothing correction variable is negative (SWA*SWV<0) and the absolute value of the smoothing correction variable is small. Therefore, the smoothing correction coefficient decreases rapidly and smoothly, which makes the active return torque control amount decrease smoothly and reduces the sudden change in steering torque when the steering wheel crosses the 0° angle.

[0097] In this example, as the driver turns the steering wheel from a non-zero position to the center position, the product of the actual steering wheel angle and the actual steering wheel speed (SWA*SWV) changes from negative to zero. At this point, the steering wheel is in a return-to-center state, and it is desirable to have a larger active return-to-center torque to assist in centering. When the steering wheel is turned outward from the center position, the product of the actual steering wheel angle and the actual steering wheel speed (SWA*SWV) changes from zero to positive. At this point, the steering wheel is in a steering state, and it is desirable to have a smaller active return-to-center torque to avoid excessively interfering with the driver's steering operation.

[0098] In one embodiment, the actual vehicle data also includes the actual steering wheel rotation speed;

[0099] like Figure 5 As shown, step S104, which involves active return-to-center control based on the second target return-to-center speed, includes:

[0100] S501: Determine the target speed difference based on the second target return speed and the actual steering wheel speed;

[0101] S502: Determine the active return torque control amount based on the target speed difference;

[0102] S503: Perform active return-to-center control based on the active return-to-center torque control amount.

[0103] As an example, in step S501, when EPS performs active return-to-center control based on the second target return-to-center speed, it needs to calculate the speed difference between the second target return-to-center speed and the actual speed of the steering wheel, and determine it as the target speed difference.

[0104] Among them, the active return torque control quantity is the torque control quantity used to achieve active return control, which can be represented by T_AR_original.

[0105] As an example, in step S502, after the EPS calculates the target speed difference corresponding to the second target return speed and the actual speed of the steering wheel, it can use the pre-set torque control quantity determination logic to calculate the target speed difference and determine its corresponding active return torque control quantity. This active return torque control quantity can be understood as the torque control quantity used to control the motor and the reduction mechanism to perform active return.

[0106] As an example, in step S503, after determining the active return torque control amount based on the target speed difference, the EPS can control the motor and reduction mechanism to actively return to center based on the active return torque control amount. In this example, the magnitude of the active return torque control amount is directly related to the target speed difference; theoretically, the smaller the target speed difference, the smaller the corresponding active return torque control amount.

[0107] Figure 10 This chart shows a comparison of the target speed difference calculated from the first target recovery speed SWV_target and the second target recovery speed SWV_target_smoothed. Figure 10 It can be seen that when calculating the target speed difference using the second target return speed SWV_target_smoothed, the abrupt change in the target speed difference is significantly reduced the instant the actual steering wheel angle passes the 0° turning position. Therefore, it can be concluded that using... Figure 9 The smoothing correction coefficient shown can effectively reduce the sudden change in the second target return speed when the steering wheel passes through the middle position, thereby reducing the sudden change in the target speed difference, so that the active return torque control amount decreases rapidly and smoothly, avoiding the sudden change in steering torque when passing through the middle position.

[0108] In one embodiment, the actual vehicle data also includes the driver's steering torque;

[0109] like Figure 6 As shown, step S503, which involves performing active return-to-center control based on the active return-to-center torque control amount, includes:

[0110] S601: Based on the actual steering wheel angle and the driver's steering torque, the active return torque control amount is corrected to determine the target return torque control amount;

[0111] S602: Perform active return-to-center control based on the target return-to-center torque control amount.

[0112] Among them, the target return torque control quantity is the control quantity used to achieve active return torque control after being modified from the active return torque control quantity.

[0113] As an example, in step S601, after obtaining the active return torque control amount, the ESP can use two actual vehicle data—the actual steering wheel angle and the driver's steering torque—to correct the active return torque control amount in order to determine the target return torque control amount.

[0114] In this example, the EPS can look up the target correction coefficient lookup table based on the actual steering wheel angle and driver steering torque, or use the target correction coefficient function to process these two variable parameters to determine the target correction coefficient. Then, the target correction coefficient is used to correct the active self-centering torque control amount to determine the target self-centering torque control amount. Specifically, the target correction coefficient and the active self-centering torque control amount can be multiplied to determine the target self-centering torque control amount. The target correction coefficient lookup table is a pre-set lookup table used to look up and determine the target correction coefficient. This table can use the actual steering wheel angle and driver steering torque as query parameters, and can also include other query parameters, which can be determined according to the actual situation. The target correction coefficient function is a pre-set function used to calculate the target correction coefficient. This target correction coefficient function can use the actual steering wheel angle and driver steering torque as variable parameters, and can also include other variable parameters.

[0115] When adjusting the active return torque control amount using the actual steering wheel angle and the driver's steering torque, as the driver's steering torque Th increases, decreasing the active return torque control amount T_AR_original and obtaining the target return torque control amount T_AR_scaled can reduce the unnatural feeling caused by active return when the driver actively steers. As the actual steering wheel angle decreases, increasing or decreasing the active return torque control amount T_AR_original can achieve a better balance between a small return residual angle and a small sudden change in steering torque.

[0116] As an example, in step S602, after determining the target return torque control amount T_AR_scaled, EPS can use the target return torque control amount T_AR_scaled for active return control, which not only ensures the naturalness of the active return process, but also achieves the goal of balancing a small return residual angle and a small change in steering torque.

[0117] In one embodiment, such as Figure 7As shown, step S601, which involves correcting the active return torque control amount based on the actual steering wheel angle and the driver's steering torque, and determining the target return torque control amount, includes:

[0118] S701: Determine the first control quantity coefficient by referring to the steering angle correction coefficient table based on the actual steering wheel angle;

[0119] S702: Determine the second control quantity coefficient by consulting the torque correction coefficient table based on the driver's steering torque;

[0120] S703: Based on the first control coefficient and the second control coefficient, the active return torque control quantity is corrected to determine the target return torque control quantity.

[0121] The steering angle correction coefficient table is a pre-set table reflecting the correspondence between the actual steering wheel angle and the first control coefficient. For example... Figure 11 As shown in the table, the steering angle correction coefficient reflects the direct proportionality between the actual steering wheel angle and the first control coefficient. That is, the larger the actual steering wheel angle, the larger the first control coefficient; conversely, the smaller the actual steering wheel angle, the smaller the first control coefficient.

[0122] As an example, in step S701, during the process of EPS correcting the active return torque control amount, it needs to consult the steering angle correction coefficient table based on the actual steering wheel angle to quickly and accurately obtain the first control amount coefficient. This first control amount coefficient, to a certain extent, reflects the influence of the actual steering wheel angle on the target return torque control amount. Generally speaking, as the actual steering wheel angle decreases, increasing or decreasing the active return torque control amount T_AR_original can achieve a better balance between a small return residual angle and a small sudden change in steering torque. Therefore, it is necessary to obtain the first control amount coefficient used to correct the active return torque control amount T_AR_original, which can be represented by g(SWA).

[0123] The torque correction coefficient table is a pre-set lookup table reflecting the correspondence between the driver's steering torque and the second control coefficient. For example... Figure 12 As shown, the torque correction coefficient table reflects the inverse relationship between the driver's steering torque and the second control coefficient. That is, the greater the driver's steering torque, the smaller the second control coefficient; conversely, the smaller the driver's steering torque, the greater the second control coefficient.

[0124] As an example, in step S702, during the process of EPS correcting the active return torque control amount, it needs to consult the torque correction coefficient table based on the driver's steering torque to quickly and accurately obtain the second control amount coefficient. This second control amount coefficient, to a certain extent, reflects the influence of the driver's steering torque on the target return torque control amount. Generally speaking, as the driver's steering torque Th increases, the active return torque control amount T_AR_original is reduced, and the target return torque control amount T_AR_scaled is obtained. This can reduce the unnatural feeling caused by active return when the driver actively steers. Therefore, it is necessary to obtain the second control amount coefficient used to correct the active return torque control amount T_AR_original, which can be represented by h(Th).

[0125] As an example, in step S703, EPS corrects the active return torque control quantity T_AR_original based on the first control quantity coefficient g(SWA) and the second control quantity coefficient h(Th) to determine the target return torque control quantity T_AR_scaled. The correction formula is as follows: T_AR_scaled = T_AR_original * g(SWA) * h(Th).

[0126] In this embodiment, the EPS corrects the active return torque control amount based on the first control amount coefficient determined by the actual steering wheel angle and the second control amount coefficient determined by the driver's steering torque. This corrects the target return torque control amount T_AR_scaled for active return control, ensuring a natural feel to the active return process while also taking into account the small return residual angle and small sudden changes in steering torque.

[0127] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0128] In one embodiment, an electric power steering system is provided, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the active return-to-center control method described in the above embodiment, for example... Figure 1 As shown in S101-S104, or Figures 2 to 7 As shown, this achieves the goal of balancing a small residual angle for steering wheel return after passing the center position and avoiding sudden changes in steering torque when the steering wheel passes the center position. To avoid repetition, this will not be elaborated further here.

[0129] In one embodiment, an electric power steering system is provided to achieve a smoother change in the target return speed over time during the steering wheel return control process. This achieves the goal of balancing a small return residual angle when the steering wheel passes the middle position and avoiding sudden changes in steering torque when the steering wheel passes the middle position. To avoid repetition, this will not be elaborated further here.

[0130] In one embodiment, a vehicle is provided, including the electric power steering system described in the above embodiments. This electric power steering system can implement the active return-to-center control method described in the above embodiments, for example... Figure 1 As shown in S101-S104, or Figures 2 to 7 As shown, this achieves the goal of balancing a small residual angle for steering wheel return after passing the center position and avoiding sudden changes in steering torque when the steering wheel passes the center position. To avoid repetition, this will not be elaborated further here.

[0131] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. This computer program can be stored in a non-volatile computer-readable storage medium. When executed, the computer program can include the processes of the embodiments of the above methods. Any references to memory, storage, databases, or other media used in the embodiments provided in this application can include non-volatile and / or volatile memory. Non-volatile memory can include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), or flash memory. Volatile memory can include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in various forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), dual data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link DRAM (SLDRAM), RAMbus direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and RAMbus dynamic RAM (RDRAM), etc.

[0132] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional units and modules is used as an example. In practical applications, the above functions can be assigned to different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above.

[0133] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. An active self-alignment control method, characterized in that, include: Acquire actual vehicle data, including actual vehicle speed, actual steering wheel angle, and actual steering wheel rotation speed; The first target return-to-center speed is obtained based on the actual vehicle speed and the actual steering wheel angle. To obtain a second target return-to-center speed by smoothing the first target return-to-center speed, the process includes: determining a smoothing correction coefficient based on the actual steering wheel angle and the actual steering wheel speed; and using the smoothing correction coefficient to smooth the first target return-to-center speed to obtain the second target return-to-center speed. Active return-to-center control is performed based on the second target return-to-center speed.

2. The active homing control method as described in claim 1, characterized in that, The step of determining the smoothing correction coefficient based on the actual steering wheel angle and the actual steering wheel speed includes: The smoothing correction variable is determined by multiplying the actual steering wheel angle and the actual steering wheel speed. The smoothing correction coefficient is determined by consulting the smoothing correction coefficient lookup table based on the smoothing correction variable.

3. The active homing control method as described in claim 2, characterized in that, If the smoothing correction variable is positive, then the smoothing correction coefficient is inversely proportional to the smoothing correction variable, and the minimum threshold of the correction coefficient is less than the smoothing correction coefficient and the critical threshold of the correction coefficient. If the smoothing correction variable is negative, then the smoothing correction coefficient is proportional to the absolute value of the smoothing correction variable, and the critical threshold of the correction coefficient is less than the smoothing correction coefficient, which is less than the maximum threshold of the correction coefficient.

4. The active homing control method as described in claim 1, characterized in that, The actual vehicle data also includes the actual steering wheel rotation speed; The active return-to-center control based on the second target return-to-center speed includes: The target speed difference is determined based on the second target return speed and the actual speed of the steering wheel; Based on the target speed difference, determine the active return torque control amount; Active return-to-center control is performed based on the active return-to-center torque control amount.

5. The active homing control method as described in claim 4, characterized in that, The actual vehicle data also includes the driver's steering torque; The active return-to-center control based on the active return-to-center torque control amount includes: Based on the actual steering wheel angle and the driver's steering torque, the active return torque control amount is corrected to determine the target return torque control amount; Active return-to-center control is performed based on the target return-to-center torque control value.

6. The active homing control method as described in claim 5, characterized in that, The step of correcting the active return torque control amount based on the actual steering wheel angle and the driver's steering torque, and determining the target return torque control amount, includes: The first control coefficient is determined by consulting the steering angle correction coefficient table based on the actual steering wheel angle. The second control quantity coefficient is determined by consulting the torque correction coefficient table based on the driver's steering torque. Based on the first control coefficient and the second control coefficient, the active return torque control quantity is corrected to determine the target return torque control quantity.

7. An electric power steering system, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the active homing control method as described in any one of claims 1 to 6.

8. The electric power steering system as described in claim 7, characterized in that, This function enables a smoother change in the target return speed over time during the steering wheel return control process.

9. A car, characterized in that, Includes the electric power steering system as described in claim 7 or 8.

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