Vehicle steering assistance system, control unit therefor and control procedure

Abstract

The present invention provides a vehicle steering assistance system, a control unit therefor, and a control method. The control unit comprises: a receiver module designed to receive a target steering angle of a vehicle; a stop control module designed to apply brakes to the vehicle in response to receiving the target steering angle, so that the vehicle is braked to a standstill; and a steering control module designed to: determine an initial drive torque and a target drive torque of the vehicle based on the coefficient of friction and the gradient of the current road surface; request the initial drive torque from the vehicle's drivetrain and control the actual drive torque of the vehicle to gradually increase from the initial drive torque;Releasing the braking applied to the vehicle when the actual drive torque of the vehicle reaches the target drive torque, causing the vehicle to begin steering, and monitoring the vehicle body yaw rate in real time; and dynamically adjusting the vehicle steering based on the monitored vehicle body yaw rate.

Description

Technical field

[0001] The present invention relates generally to the technical field of vehicle steering assistance. In particular, the present invention relates to a vehicle steering assistance system, a control unit therefor, and a control method. State of the art

[0002] Vehicle steering assistance functions can support a driver in achieving vehicle steering. However, existing vehicle steering assistance functions are unsatisfactory in terms of improving vehicle comfort and driving experience. For example, existing vehicle steering assistance functions typically require the driver to continuously operate the steering wheel and keep the accelerator pedal depressed, thus requiring a relatively large effort from the driver to achieve vehicle steering. Brief description of the invention

[0003] In view of the problems found in the prior art described above, according to one aspect of the present invention, a control unit for a vehicle steering assistance system is provided, comprising: a receiver module designed to receive a target steering angle of the vehicle; a stop control module designed to apply brakes to the vehicle in response to receiving the target steering angle, so that the vehicle is braked to a standstill; and a steering control module designed to: determine an initial drive torque and a target drive torque of the vehicle based on a current road surface adhesion coefficient and a current road gradient; request the initial drive torque from a drivetrain of the vehicle and control an actual drive torque of the vehicle to gradually increase from the initial drive torque;Releasing the braking applied to the vehicle when the actual drive torque of the vehicle reaches the target drive torque, causing the vehicle to begin steering, and monitoring a vehicle body yaw rate in real time; and dynamically adjusting the vehicle steering based on the monitored vehicle body yaw rate, wherein dynamically adjusting the vehicle steering based on the monitored vehicle body yaw rate includes: when it is detected that the vehicle body yaw rate exceeds an upper limit threshold, maintaining the target drive torque unchanged or adjusting a front axle target slip ratio of the vehicle in a downward direction, wherein the rate of decline of the front axle target slip ratio is positively correlated with the extent to which the monitored vehicle body yaw rate exceeds the upper limit threshold;and if it is detected that the vehicle body yaw rate is lower than a predetermined lower limit threshold, increasing the target drive torque or adjusting the front axle target slip ratio propels the vehicle in an upward direction, the rate of increase of the target drive torque or the rate of increase of the front axle target slip ratio being positively correlated with the extent to which the monitored vehicle body yaw rate is lower than the lower limit threshold.

[0004] In one embodiment, applying braking to the vehicle so that the vehicle is brought to a standstill comprises: turning the steering wheel to its stop or nearly to its stop in a direction corresponding to the target steering angle; locking an outer rear wheel of the vehicle; and determining braking for wheels other than the outer rear wheel, based on the current road surface friction coefficient and road gradient, as well as a vehicle mass, so that the vehicle is brought to a standstill.

[0005] In one embodiment, releasing the braking applied to the vehicle when the actual drive torque of the vehicle reaches the target drive torque comprises the following: releasing the braking applied to the other wheels and keeping the outer rear wheel locked.

[0006] In one embodiment, the steering control module is further designed to: determine, from several predetermined yaw rate thresholds, a yaw rate threshold corresponding to the target steering angle; determine a yaw rate adjustment amount based on the current road surface adhesion coefficient; add the determined yaw rate adjustment amount to the determined yaw rate threshold to obtain the upper limit threshold; and subtract the determined yaw rate adjustment amount from the determined yaw rate threshold to obtain the lower limit threshold.

[0007] In one embodiment, dynamic adjustment of vehicle steering comprises: matching a front axle drive torque of the vehicle to the target drive torque; and matching a rear wheel drive torque of the vehicle to the front axle drive torque or a value smaller by a predetermined amount of deviation.

[0008] In one embodiment, the steering control module is further designed to: predict an angle of inertia of the vehicle based on the current road surface condition and the current vehicle steering state, wherein the angle of inertia refers to the angle by which the vehicle rotates from the point at which the application of drive torque to the vehicle is stopped until the point at which the vehicle comes to a standstill; and stop the application of drive torque to the vehicle when, based on the monitored vehicle body yaw rate, it is calculated that the angle by which the vehicle has rotated is equal to an angular difference between the target steering angle and the angle of inertia.

[0009] According to another aspect of the present invention, a vehicle steering assistance system is provided comprising: a human-machine interface designed to receive driver input comprising a target steering angle of the vehicle; and the control unit described above, designed to automatically control the vehicle steering to achieve the target steering angle.

[0010] In one embodiment, the human-machine interface comprises one or more of the following for obtaining the target steering angle: several keys / buttons capable of receiving driver input or representing different vehicle steering angles; a text field into which the driver can enter a vehicle steering angle; an angle bar representing a steering angle range and a slider that can be operated by the driver to be moved along the angle bar; and a voice interface capable of receiving voice input from the driver.

[0011] According to yet another aspect of the present invention, a vehicle steering control method is provided, comprising: receiving a target steering angle of the vehicle; in response to receiving the target steering angle, applying brakes to the vehicle so that the vehicle is decelerated to a standstill; determining an initial drive torque and a target drive torque of the vehicle based on the current road surface adhesion coefficient and the current road gradient; requesting the initial drive torque from a drivetrain of the vehicle and controlling an actual drive torque of the vehicle to gradually increase from the initial drive torque; releasing the brakes applied to the vehicle when the actual drive torque of the vehicle reaches the target drive torque so that the vehicle begins to steer, and monitoring a vehicle body yaw rate in real time;and dynamic adjustment of the vehicle steering based on the monitored vehicle body yaw rate, wherein dynamic adjustment of the vehicle steering based on the monitored vehicle body yaw rate includes: when it is detected that the vehicle body yaw rate exceeds an upper limit threshold, maintaining the target drive torque unchanged or adjusting a front axle target slip ratio of the vehicle in a downward direction, wherein the rate of decline of the front axle target slip ratio is positively correlated with the extent to which the monitored vehicle body yaw rate exceeds the upper limit threshold;and if it is detected that the vehicle body yaw rate is lower than the predetermined lower limit threshold, increasing the target drive torque or adjusting the front axle target slip ratio propels the vehicle in an upward direction, the rate of increase of the target drive torque or the rate of increase of the front axle target slip ratio being positively correlated with the extent to which the monitored vehicle body yaw rate is lower than the lower limit threshold.

[0012] According to yet another aspect of the present invention, a machine-readable storage medium is provided which stores executable instructions, wherein the instructions, when executed, cause one or more processors to perform the vehicle steering control method as described above. Brief description of the drawings

[0013] The technical solution of the present invention will become more apparent from the following detailed description in conjunction with the drawings. It is understood that these drawings serve only for illustration and are not intended to limit the scope of protection of the present invention. Fig. Figure 1 is a schematic block diagram of a vehicle steering assistance system according to an embodiment of the present invention. Fig. 2A and Fig. 2B are some embodiments of a human-machine interface of the in Fig. 1 vehicle steering assistance system shown. Fig. Figure 3 is a flowchart of a vehicle steering assistance method according to an embodiment of the present invention. Fig. Figure 4 is a graph showing the dynamic adjustment of vehicle steering. Specific embodiments

[0014] Embodiments of the present invention provide a vehicle steering assistance solution that can automatically control vehicle steering, thereby achieving the target steering angle of the vehicle with the smallest possible turning radius.

[0015] Furthermore, according to embodiments of the present invention, the vehicle steering assistance task can provide an interface to be compatible / connected with other tasks of vehicle driving assistance (for example, upstream tasks or downstream tasks), thus improving the level of automation of the vehicle.

[0016] Specific embodiments of the present invention are described below in conjunction with the drawings.

[0017] Fig. Figure 1 schematically shows a vehicle driver assistance system 100 according to an embodiment of the present invention (hereinafter referred to as system 100). The system 100 is provided on a vehicle V, and therefore the system 100 is an in-vehicle system. As shown in Fig. As shown in Figure 1, the system 100 comprises the following: a human-machine interface (HMI) 10 and a control unit 20.

[0018] The human-machine interface 10 can interact with the driver of the vehicle V. The human-machine interface 10 can be implemented via a central control screen or a head-up display in the vehicle V. The human-machine interface 10 can receive a vehicle steering angle input from the driver. The received vehicle steering angle is the target steering angle for this vehicle steering assistance task. In other words, this steering assistance task is: automatically controlling the vehicle steering to achieve the vehicle steering angle input from the driver (the target steering angle) without the driver having to continuously operate the vehicle. Furthermore, while the target steering angle is being achieved, the vehicle's turning radius can be minimized.

[0019] In one embodiment, referring to Fig. In embodiment 2A, the human-machine interface 10 comprises several buttons / switches 11-14 capable of receiving driver input or representing different vehicle steering angles. For example, 90° is represented on button / switch 11; 180° is represented on button / switch 12; 27° is represented on button / switch 13; and 360° is represented on button / switch 14. When the driver touches or presses a button / switch, this indicates that the driver input is the vehicle steering angle represented on the button / switch. In other words, the vehicle steering angle for this steering assistance task, set / inputted by the driver, is received via the button / switch at the human-machine interface. In this embodiment, the human-machine interface 10 may also include a text field 15.The driver can enter / edit a desired vehicle steering angle in text field 15, which will be used as the target steering angle for this steering assistance task.

[0020] In a further embodiment, referring to Fig. 2B, the human-machine interface 10, an angle bar 16, and an operable slider 17. The angle bar 16 indicates a range of vehicle steering angles, for example, from a permissible minimum vehicle steering angle (e.g., 0°) to a maximum vehicle steering angle (e.g., 540°). The slider 17 can be moved along the angle bar 16 by the driver. For example, the driver pulls the slider 17 to move it along the angle bar 16, and the position at which the slider 17 stops indicates (corresponds to) the vehicle steering angle entered by the driver, that is, the target steering angle for this steering assistance task.

[0021] In yet another embodiment, the human-machine interface 10 can receive voice input from the driver, thus enabling the driver to input a vehicle steering angle into the human-machine interface 10 in the form of speech. In other words, in this embodiment, the target steering angle for this steering assistance task is determined based on the driver's voice input. For example, if the driver gives the voice command "Please steer 360°", the human-machine interface 10 determines, through speech recognition, that the target steering angle for this steering assistance task is 360°.

[0022] It should be noted that the three embodiments mentioned above are not mutually exclusive. Rather, the human-machine interface 10 can simultaneously possess the driver input methods described in the two or three embodiments above. For example, the human-machine interface 10 simultaneously features driver input via the slider and driver input via voice.

[0023] The control unit 20 is connected to and communicates with the human-machine interface 10. The control unit 20 receives the target steering angle from the human-machine interface 10 and controls the vehicle to achieve the target steering angle according to the steering control strategy of embodiments of the present invention. In one embodiment, the control unit 20 comprises a receiver module 21 for receiving the target steering angle, a stop control module 22 for controlling the braking of the vehicle to a standstill, and a steering control module 23 for controlling the vehicle steering.

[0024] These modules 21-23 of the control unit 20 can be implemented by hardware, software, or a combination of both. Hardware-implemented components can be implemented in one or more application-specific integrated circuits (ASICs), digital signal processors (DSPs), data signal processing devices (DSPDs), programmable logic devices (PLDs), field-programmable gate arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, electronic units designed to perform their functions, or a combination thereof. Software-implemented components can be implemented using microcode, program code, or code segments and can also be stored in a machine-readable storage medium, such as a storage component.

[0025] In one embodiment, the control unit 20 comprises a memory and a processor. The memory contains instructions which, when executed by the processor, cause the processor to carry out the steering control method according to one embodiment of the present invention.

[0026] The control unit 20 can be provided in an electronic control unit (ECU) of the vehicle V, can also be provided in a vehicle control unit (VCU) and can furthermore be provided in a domain controller of the vehicle V.

[0027] Fig. Figure 3 shows the vehicle steering control method 300 according to an embodiment of the present invention. The method 300 can be carried out by the system 100 described above and can also be carried out by the control unit 20 described above, and therefore the above descriptions of the system 100 and the control unit 20 are also applicable here.

[0028] In block 302, the receiver module 21 receives the target steering angle from the human-machine interface 10. As described above, the target steering angle is obtained based on a driver input into the human-machine interface 10.

[0029] In block 304, the stop control module 22, in response to the receiver module 21 receiving the target steering angle, applies brakes to the vehicle, thus braking it to a standstill. The process in block 304 can be considered an initial control stage of the steering control.

[0030] According to embodiments of the present invention, automated steering control of the vehicle mainly comprises two stages: 1) an initial control stage for stopping the vehicle in block 304; and 2) a steering control stage in the following blocks 306-318.

[0031] In one embodiment, block 304 comprises a sub-step (block 3041) for controlling the steering wheel and a sub-step (block 3042) for controlling the wheels.

[0032] In block 3041, the stop control module 22 sends a steering request to the electric power steering system (EPS) of vehicle V, comprising a predetermined target steering wheel angle, so that the electric power steering system acts on the steering wheel according to the target steering wheel angle. That is, in block 3041, the steering wheel of vehicle V is turned to a position corresponding to the target steering wheel angle.

[0033] It is understood that the direction of the target steering wheel angle corresponds to the target steering angle of the vehicle; for example, the two angles are in the same direction. Furthermore, the target steering wheel angle is predefined as a relatively large steering wheel angle, for example, an angle at which the steering wheel is turned to its full lock, or an angle at which the steering wheel is turned almost to its full lock (for example, 500°). Such an operation is advantageous because a relatively large steering wheel angle helps to achieve a smaller turning radius. Therefore, the steering assistance solution according to embodiments of the present invention has the advantage of a small turning radius.

[0034] In block 3042, the stop control module 22 issues a braking request to a braking system (for example, a brake caliper system) of vehicle V, which includes the following braking instructions: 1) locking an outer rear wheel of vehicle V; and 2) applying brakes to wheels other than the outer rear wheel, so that vehicle V comes to a standstill. Braking is determined based on the current road surface friction coefficient and gradient, as well as the mass of vehicle V. The gradient of the current road surface can be determined based on the detected value from the accelerometer or a gradient sensor in the vehicle. In the current scenario (that is, with the current road surface friction coefficient, the current road gradient, and the vehicle mass), braking can cause vehicle V to brake to a standstill.The present invention does not limit how to calculate the braking (braking force) to be provided for the wheels other than the outer rear wheel.

[0035] In block 306, the steering control module 23 determines an initial drive torque and a target drive torque for the vehicle V based on the current road surface friction coefficient. The initial drive torque is the initial value of the drive torque requested by the vehicle V's drivetrain. This initial value (i.e., the initial drive torque) increases as the current road surface friction coefficient increases. That is, the higher the current road surface friction coefficient, the higher the initial value (the initial drive torque). The target drive torque is the drive torque that, after the brakes are released on the wheels other than the outer rear wheel, is sufficient to hold the vehicle V stationary (for example, without rolling or sliding).

[0036] In one embodiment, a drive torque table is stored in the steering control module 23, and this table includes correspondences that relate several factors influencing the initial drive torque and the target drive torque (for example, the road surface adhesion coefficient, the road gradient, and the mass of the vehicle body) to the initial drive torque and the target drive torque. Based on the current scenario (that is, with the current road surface adhesion coefficient, the current road gradient, and the mass of the vehicle V), the steering control module 23 can determine the initial drive torque and the target drive torque by looking up the values ​​in the table.

[0037] In block 308, the steering control module 23 sends a drive torque request to the vehicle V's drivetrain, including the specified initial drive torque and the target drive torque, so that the drivetrain controls the actual drive torque of the vehicle V to gradually increase from the initial drive torque to the target drive torque.

[0038] In block 310, the steering control module 23 monitors the actual drive torque of vehicle V, and upon detecting that the actual drive torque has reached the target drive torque, it sends a command to the braking system of vehicle V to release the brakes on wheels other than the outer rear wheel. Vehicle V then begins to steer.

[0039] In block 312, the steering control module 23 monitors the vehicle body yaw rate of vehicle V during steering and dynamically adjusts the vehicle steering based on the monitored vehicle body yaw rate, so that the vehicle body yaw rate is within a yaw rate variation range defined by an upper limit (see “Yaw_thre1” in Fig. 4) and a lower threshold (see “Yaw_thre2” in Fig. 4) is defined. In one embodiment, block 312 may comprise several sub-steps: a sub-step (block 3121) for determining the upper limit threshold (Yaw_thre1) and the lower limit threshold (Yaw_thre2); a sub-step (block 3122) for dynamically adjusting the vehicle steering; and a sub-step (block 3123) for adjusting the front axle drive torque and the rear axle drive torque of vehicle V.

[0040] In block 3121, the steering control module 23 determines the upper limit threshold (Yaw_thre1) and the lower limit threshold (Yaw_thre2) of the yaw rate variation range.

[0041] In one embodiment, the steering control module 23 first determines a yaw rate threshold from several predetermined yaw rate thresholds, corresponding to the target steering angle. Generally, the larger the target steering angle, the larger the yaw rate threshold selected from the several predetermined yaw rate thresholds. For example, the several predetermined yaw rate thresholds comprise yaw rate thresholds from three levels: fast, medium, and slow (e.g., 20° / s, 30° / s, and 40° / s). If the target steering angle is 30–90°, the slow-level yaw rate threshold (20° / s) is determined; if the target steering angle is 90–270°, the medium-level yaw rate threshold (30° / s) is determined; and if the target steering angle is greater than 270°, the fast-level yaw rate threshold (40° / s) is determined. Another scenario is this: the yaw rate threshold is set by a user (for example, a vehicle manufacturer or a vehicle driver).Another scenario is this: the yaw rate threshold is determined by a preceding or subsequent task in this driver assistance task.

[0042] Next, the steering control module 23 determines a yaw rate adjustment amount (a yaw rate fluctuation range) based on the current road surface condition. A yaw rate adjustment amount table may be stored in the steering control module 23, and it includes several types of road surface conditions and corresponding yaw rate adjustment amounts; that is, a relationship between road surface types and recommended yaw rate adjustment amounts. For example, a flat road surface (without bumps or potholes) – a first yaw rate adjustment amount (e.g., ±6° / s); an icy / snowy road surface – a second yaw rate adjustment amount (e.g., ±4° / s); an asphalt road surface – a third yaw rate adjustment amount (e.g., ±8° / s), and so on. The steering control module 23 identifies the current road surface type and obtains the corresponding yaw rate adjustment amount by looking it up in the table.

[0043] Next, the specified yaw rate adjustment amount is added to the specified yaw rate threshold to obtain the upper limit. The specified yaw rate adjustment amount is then subtracted from the specified yaw rate threshold to obtain the lower limit.

[0044] It can be seen that the upper limit is obtained by increasing the specified yaw rate adjustment amount from the specified yaw rate threshold; and the lower limit is obtained by subtracting the specified yaw rate adjustment amount from the specified yaw rate threshold. The advantage of this is that adjustment to the target steering angle can be achieved, so that a relatively large target steering angle does not require too much time to execute, and that adjustment to the current road surface condition can also be achieved, thereby ensuring stability during vehicle steering.

[0045] In block 3122, the steering control module 23 monitors the vehicle body yaw rate and dynamically adjusts the vehicle steering based on the monitored vehicle body yaw rate.

[0046] Fig. Figure 4 is a graph showing a dynamic adjustment of the vehicle steering, where the horizontal axis represents time (t) and the vertical axis represents the vehicle body yaw rate (yr) of vehicle V. The gray curve shows the monitored vehicle body yaw rate. The two straight lines each indicate an upper limit (Yaw_thre1) and a lower limit (Yaw_thre2) of the vehicle body yaw rate, and they define an allowable yaw rate variation range.

[0047] Referring to Fig. 4. If it is detected that the vehicle body yaw rate is greater than the upper limit threshold (Yaw_thre1), the target drive torque will be left unchanged, or the vehicle's front axle target slip ratio will be adjusted in a downward direction so that the vehicle body yaw rate gradually returns to the aforementioned yaw rate variation range.

[0048] In one embodiment, the reduction of the front axle target slip ratio can be achieved as follows. The reduction of the front axle target slip ratio is intended to ensure that the front axle target slip ratio remains within a predetermined slip ratio variation range (for example, within 2 m / s to 4 m / s). The slip ratio variation range can be predetermined based on actual vehicle tests and / or a model calculation.Furthermore, the reduction of the front axle target slip ratio includes the following: the more the vehicle body yaw rate exceeds the upper limit (that is, the further it deviates from the vehicle body yaw rate variation range), the faster the reduction rate. In other words, the rate of reduction of the front axle target slip ratio is positively correlated with the extent to which the monitored vehicle body yaw rate exceeds the upper limit. The advantage of this is that if the vehicle body yaw rate deviates from the vehicle body yaw rate variation range by a relatively large amount, it can be quickly reduced. In other words, the rate of reduction of the front axle target slip ratio is a value that corresponds to the extent to which the upper limit is exceeded (the extent of deviation from the vehicle body yaw rate variation range).

[0049] The steering control module 23 can use the following formula (i) to calculate the rate of reduction of the front axle target slip ratio, so that a corresponding actuator performs a slip ratio reduction operation according to the calculated rate of reduction of the front axle target slip ratio: dSlip_Decrease=k1∗dDeltaYawrate / dt+k2∗DeltaYawrate In the formula, “dSlip_Decrease” indicates the rate of reduction of the front axle target slip ratio; “DeltaYawrate” indicates the yaw rate deviation between the actual yaw rate of the vehicle V and the upper limit of the yaw rate; “dDeltaYawrate / dt” is a derivative of the yaw rate deviation; “k1” is a coefficient of dDelta Yawrate / dt; “k2” is a coefficient of DeltaYawrate.

[0050] In formula (i), dDeltaYawrate / dt indicates how quickly the yaw rate changes. A larger coefficient k1 of dDeltaYawrate / dt indicates a faster response time to yaw rate adjustment, meaning the yaw rate can be pulled back below the upper limit more quickly. DeltaYawrate indicates yaw rate fluctuations. A larger coefficient k2 of DeltaYawrate indicates better yaw rate stability, meaning the yaw rate fluctuations during the process of pulling back below the upper limit are smaller.

[0051] In the steering control module 23, requirements for the response speed and stability of the yaw rate adaptation (for example, requirements of a vehicle manufacturer or preferences of an end user) can be stored in advance. The steering control module 23 calibrates the coefficients k1 and k2 according to the pre-stored requirements for response speed and stability of the yaw rate adaptation, thereby obtaining coefficients k1 and k2 that meet the requirements and thus determining the rate of yaw rate reduction.

[0052] Referring again to Fig. 4. If it is detected that the vehicle body yaw rate is less than the lower limit threshold (Yaw_thre2), the target drive torque will be increased, or the vehicle's front axle target slip ratio will be adjusted in an upward direction so that the vehicle body yaw rate gradually returns to the aforementioned yaw rate variation range.

[0053] In one embodiment, the increase in target drive torque should ensure that the target drive torque is not increased beyond the maximum drive torque that the vehicle's drive equipment can provide. Furthermore, the increase in target drive torque includes the following: the more the vehicle body yaw rate falls below the lower limit threshold (that is, the further it deviates from the vehicle body yaw rate variation range), the faster the rate of increase; that is, the rate of increase in target drive torque is positively correlated with the extent to which the monitored vehicle body yaw rate is lower than the lower limit threshold. The advantage of this is that if the vehicle body yaw rate deviates from the vehicle body yaw rate variation range by a relatively large amount, it can be quickly reduced.In other words, the rate of increase of the target drive torque is a value corresponding to the extent to which the lower limit threshold is undershot (the extent of deviation from the vehicle body yaw rate variation range). In this embodiment, there is also a constraint condition regarding the rate of increase of the target drive torque: the steering control module 23 adjusts the rate of increase of the target drive torque such that, after the vehicle body yaw rate stabilizes, the amount by which it exceeds the lower yaw rate limit is within a predetermined percentage of it (for example, within 10% of the lower yaw rate limit). For example, if the lower yaw rate limit is 10° / s and the predetermined percentage is 10%, the value of the vehicle body yaw rate after stabilization should be 10° / s–11° / s.

[0054] In one embodiment, the increase in the target front axle slip ratio can be achieved as follows. Increasing the target front axle slip ratio is intended to ensure that the target front axle slip ratio remains within a predetermined slip ratio variation range (for example, within 2 m / s to 4 m / s). The slip ratio variation range can be predetermined based on actual vehicle tests and / or a model calculation.Furthermore, increasing the front axle target slip ratio involves the following: the more the vehicle body yaw rate falls below the lower limit threshold (that is, the further it deviates from the vehicle body yaw rate variation range), the faster the rate of increase. In other words, the rate of increase of the front axle target slip ratio is positively correlated with the extent to which the monitored vehicle body yaw rate is lower than the lower limit threshold. The advantage of this is that if the vehicle body yaw rate deviates from the vehicle body yaw rate variation range by a relatively large amount, it can be quickly reduced. In other words, the rate of increase of the front axle target slip ratio is a value that corresponds to the extent to which the lower limit threshold is undershot (the extent of deviation from the vehicle body yaw rate variation range).

[0055] Similar to the above procedure for determining the rate of reduction of the front axle target slip ratio, the steering control module 23 can use the following formula (ii) to calculate the rate of increase of the front axle target slip ratio, so that a corresponding actuator performs a slip ratio increase operation according to the calculated rate of increase of the front axle target slip ratio: dSlip_Increase=k3*dDeltaYawrate' / dt+k4*DeltaYawrate' In the formula, “dSlip_Increase” indicates the rate of increase of the front axle target slip ratio; “DeltaYawrate” indicates the yaw rate deviation between the actual yaw rate of the vehicle V and the lower limit of the yaw rate; “dDeltaYawrate’ / dt” is a derivative of the yaw rate deviation; “k3” is a coefficient of dDeltaYawrate / dt; “k4” is a coefficient of DeltaYawrate’.

[0056] In formula (iii), dDeltaYawrate' / dt indicates how quickly the yaw rate changes, and if the coefficient k3 of dDeltaYawrate' / dt is larger, the response speed of the yaw rate adjustment is faster, meaning the yaw rate can be pulled back above the lower limit more quickly. DeltaYawrate' indicates yaw rate fluctuation, and if the coefficient k4 of DeltaYawrate' is larger, the stability of the yaw rate adjustment is better, meaning the yaw rate fluctuation during the process of pulling back above the lower limit is smaller.

[0057] In the steering control module 23, requirements for the response speed and stability of the yaw rate adjustment (for example, requirements of a vehicle manufacturer or preferences of an end user) can be stored in advance. The steering control module 23 calibrates the coefficients k3 and k4 according to the pre-stored requirements for response speed and stability of the yaw rate adjustment, thereby obtaining coefficients k3 and k4 that meet the requirements and thus determining the rate of yaw rate increase.

[0058] In block 3123, the steering control module 23 determines the rear axle drive torque based on the vehicle's front axle drive torque V. The vehicle's front axle drive torque V is equal to (i.e., is) the target drive torque. The vehicle's rear axle drive torque V is equal to the front axle drive torque or is less than the front axle drive torque by a predetermined deviation amount. The deviation amount can be predetermined based on actual vehicle tests and / or a model calculation.

[0059] In block 314, the steering control module 23 predicts an angle of inertia based on the current road surface condition (road surface type, coefficient of friction, gradient) and the current vehicle steering state (for example, the vehicle body yaw rate and fluctuation of the vehicle body yaw rate), that is, the angle through which the vehicle rotates from the point at which the application of the drive torque to the vehicle ceases until the point at which the vehicle comes to a standstill. The prediction can be implemented using a predictive model. The present invention does not limit the specific way in which the prediction of the angle of inertia is implemented.

[0060] In block 316, the steering control module 23 integrates the vehicle body yaw rate to obtain the angle by which the vehicle V has rotated. Furthermore, once it has been determined that the angle by which the vehicle V has rotated is exactly equal to the angle difference after subtracting the angle of inertia from the target steering angle, the application of the drive torque to the vehicle V is stopped.

[0061] The advantage of this is that when the vehicle comes to a standstill, it has rotated precisely by the target steering angle and will not rotate by any further angle due to inertia.

[0062] In block 318, once the vehicle has rotated through the target steering angle, the outer rear wheel lock is released, and braking force is applied to all four wheels of the vehicle, V, based on the current road gradient, to enter a vehicle pressure holding state (i.e., a HOLD state). The vehicle pressure holding state is terminated when the driver fully depresses the accelerator pedal.

[0063] It is understood that all operations in the processes and methods described above are merely exemplary and that the present invention is not limited to any operation in the methods or to the sequence of these operations, but is intended to cover all other equivalent variations under the same or a similar concept.

[0064] The present invention further provides a machine-readable storage medium that stores executable instructions which, when executed, cause a machine to perform the vehicle steering control method 300 as described above.

[0065] It is understood that the control unit can include one or more processors. These processors can be implemented using electronic hardware, computer software, or any combination thereof. Whether these processors are implemented as hardware or software depends on the specific application and the overall design constraints imposed on the system.As an example, the processor provided in the present invention, any part of the processor, or any combination of processors can be implemented as a microprocessor, a microcontroller, a digital signal processor (DSP), a field-programmable gate array (FPGA), a programmable logic device (PLD), a state machine, gate logic, discrete hardware circuits, and other suitable processing components designed to perform the various functions described in the present invention. The functions of the processor provided in the present invention, any part of the processor, or any combination of processors can be implemented as software executed by a microprocessor, a microcontroller, a DSP, or another suitable platform.

[0066] It is understood that software, in the broadest sense, can be considered to represent instructions, instruction sets, code, code segments, program code, programs, subroutines, software modules, applications, software applications, software packages, routines, subroutines, objects, running threads, processes, functions, and the like. The software may reside on a computer-readable medium. This computer-readable medium may, for example, include memory, and the memory may be, for example, a magnetic storage device (such as a hard disk, floppy disk, or magnetic stripe), an optical disk, a smart card, a flash memory device, random-access memory (RAM), read-only memory (ROM), a programmable ROM (PROM), an erasable PROM (EPROM), an electrically erasable PROM (EEPROM), a register, or a removable disk.Although the memory is shown to be separate from the processor in several aspects provided in the present invention, the memory can also be located within the processor (such as a cache or a register).

[0067] The above description is provided so that any person skilled in the art can implement the various aspects described herein. Various modifications of these aspects are obvious to a person skilled in the art, and the general principles defined herein can be applied to other aspects. Therefore, the claims are not intended to be limited to the aspects shown here. All structurally and functionally equivalent variations of elements of the various aspects described in the present invention that are known or become known to a person skilled in the art are expressly included here by reference and are intended to be covered by the claims.

Claims

[1] Control unit for a vehicle steering assistance system comprising the following: a receiving module designed to receive a target steering angle from a vehicle; a stop control module designed to apply braking to the vehicle in response to receiving a target steering angle, so that the vehicle is braked to a standstill; and a steering control module designed to: determine an initial drive torque and a target drive torque of the vehicle based on a current road surface adhesion coefficient and a current road gradient; requesting the initial drive torque from a vehicle drivetrain and controlling an actual vehicle drive torque to gradually increase from the initial drive torque; releasing the braking applied to the vehicle when the vehicle's actual drive torque reaches the target drive torque, so that the vehicle begins to steer, and monitoring of a vehicle body yaw rate in real time; and dynamically adjusting the vehicle steering based on the monitored vehicle body yaw rate, where dynamic adjustment of the vehicle steering based on the monitored vehicle body yaw rate includes the following: if it is detected that the vehicle body yaw rate exceeds a predetermined upper limit threshold, maintaining the target drive torque unchanged or adjusting a front axle target slip ratio of the vehicle in a downward direction, wherein the rate of decline of the front axle target slip ratio is positively correlated with the extent to which the monitored vehicle body yaw rate exceeds the upper limit threshold; and If it is detected that the vehicle body yaw rate is lower than a predetermined lower limit threshold, increase the target drive torque or adjust the vehicle's front axle target slip ratio in an upward direction, where a rate of increase in target drive torque or a rate of increase in front axle target slip ratio is positively correlated with an extent by which the monitored vehicle body yaw rate is lower than the lower limit threshold. [2] Control unit according to claim 1, wherein applying brakes to the vehicle so that the vehicle is braked to a standstill comprises: Turning the steering wheel in one direction according to the target steering angle until it reaches the stop; and Locking an outer rear wheel of the vehicle and determining brakes for wheels other than the outer rear wheel, based on a current road surface adhesion coefficient and a current road gradient, as well as a vehicle mass, so that the vehicle is braked to a standstill. [3] Control unit according to claim 2, wherein releasing the braking applied to the vehicle when the actual drive torque of the vehicle reaches the target drive torque comprises: Releasing the braking applied to the other wheels and Locking the outer rear wheel. [4] Control unit according to claim 1, wherein the steering control module is further designed to: Determine, from several predetermined yaw rate thresholds, a yaw rate threshold corresponding to the target steering angle; Determining a yaw rate adjustment amount based on a current road surface adhesion coefficient; Adding the specified yaw rate adjustment amount to the specified yaw rate threshold to obtain the upper limit threshold; and subtracting the specified yaw rate adjustment amount from the specified yaw rate threshold to obtain the lower limit threshold. [5] Control unit according to claim 1, wherein dynamic adjustment of the vehicle steering comprises: Matching the vehicle's front axle drive torque to the target drive torque; and Matching the rear axle drive torque of the vehicle to the front axle drive torque or to a value that is smaller than the front axle drive torque by a predetermined deviation amount. [6] Control unit according to claim 1, wherein the steering control module is further designed to: Prediction of a vehicle's angle of inertia based on a current road surface condition and a current vehicle steering condition, where the angle of inertia refers to an angle by which the vehicle rotates from the point at which the application of drive torque to the vehicle is stopped to the point at which the vehicle comes to a standstill; and stopping the application of drive torque to the vehicle when, based on the monitored vehicle body yaw rate, it is calculated that the angle by which the vehicle has rotated is equal to an angular difference between the target steering angle and the angle of inertia. [7] Vehicle steering assistance system comprising the following: a human-machine interface designed to receive driver input comprising a target steering angle of a vehicle; and the control unit according to one of claims 1-6, designed to automatically control the vehicle steering to achieve the target steering angle. [8] Vehicle steering assistance system according to claim 7, wherein the human-machine interface comprises one or more of the following to obtain the target steering angle: multiple buttons / switches capable of receiving driver input or representing different vehicle steering angles; a text field into which a driver can enter a vehicle steering angle; an angle bar representing a steering angle range; and a slider that the driver can use to move the vehicle along the angle bar; and a voice interface capable of receiving voice input from the driver. [9] Vehicle steering control procedure comprising the following: Receiving a vehicle's steering angle signal; In response to receiving a target steering angle, applying brakes to the vehicle so that the vehicle is braked to a standstill; Determining an initial drive torque and a target drive torque of the vehicle based on a current road surface adhesion coefficient and a current road gradient; Requesting the initial drive torque from a vehicle's drivetrain and controlling an actual vehicle drive torque to gradually increase from the initial drive torque; Releasing the braking applied to the vehicle when the actual drive torque of the vehicle reaches the target drive torque, so that the vehicle begins to steer, and monitoring a vehicle body yaw rate in real time; and Dynamic adjustment of vehicle steering based on the monitored vehicle body yaw rate, where dynamic adjustment of the vehicle steering based on the monitored vehicle body yaw rate includes the following: if it is detected that the vehicle body yaw rate exceeds a predetermined upper limit threshold, maintaining the target drive torque unchanged or adjusting a front axle target slip ratio of the vehicle in a downward direction, wherein the rate of decline of the front axle target slip ratio is positively correlated with the extent to which the monitored vehicle body yaw rate exceeds the upper limit threshold; and If it is detected that the vehicle body yaw rate is lower than a predetermined lower limit threshold, increase the target drive torque or adjust the vehicle's front axle target slip ratio in an upward direction, where a rate of increase in target drive torque or a rate of increase in front axle target slip ratio is positively correlated with an extent by which the monitored vehicle body yaw rate is lower than the lower limit threshold. [10] Machine-readable storage medium that stores executable instructions which, when executed, cause one or more processors to perform the vehicle steering control method according to claim 9.

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