System and method for providing evasive steering assistance

Abstract

A method for providing evasive steering assistance (ESA), the method comprising storing yaw rate data associated with a host vehicle, wherein the yaw rate data comprises a yaw rate stored at each time step from an initial time step [0] to a current time step [n]. The method further comprises determining whether to initiate ESA, wherein in response to determining to initiate ESA, the method comprises calculating a current position, a current heading angle, a destination position, and a destination heading angle, wherein the stored yaw rate is used to determine the current heading angle and the destination heading angle. The method further comprises generating an evasive steering assistance (ESA) output based on the current position, the current heading angle, the destination position, and the destination heading angle.

Description

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 189,835, filed on April 26, 2021, which is incorporated herein by reference in its entirety. Background Art

[0002] The present disclosure relates generally to methods of providing evasive steering assistance, and more particularly to evasive steering assistance in the absence of lane markings.

[0003] Evasive steering assist (ESA) amplifies steering maneuvers in the presence of an impending head-on collision. For example, ESA may be initiated in response to a determination that a steering maneuver initiated by the driver is insufficient to avoid a collision, wherein the ESA response may be in the form of an additional steering torque in the direction of the driver input. The additional steering torque is overlaid on the steering torque applied by the driver to avoid the primary object. As a result, the host vehicle will steer around the obstacle. Most ESA features utilize lane markings to determine the position, direction, and / or motion of the host vehicle. In the absence of lane markings, the ESA feature cannot be initiated. It would be beneficial to provide an ESA feature that can be implemented in the absence of lane markings. SUMMARY OF THE INVENTION

[0004] According to one aspect, a method for providing evasive steering assistance (ESA) includes storing yaw rate data associated with a host vehicle, wherein the yaw rate data includes a yaw rate stored at each time step from an initial time step [0] to a current time step [n]. The method further includes determining whether to initiate ESA, wherein in response to determining to initiate ESA, the method includes calculating a current position, a current heading angle, a destination position, and a destination heading angle, wherein the stored yaw rate is used to determine the current heading angle and the destination heading angle. The method further includes generating an evasive steering assistance (ESA) output based on the current position, the current heading angle, the destination position, and the destination heading angle.

[0005] According to another aspect, a system for providing evasive steering assistance (ESA) to a host vehicle includes a first input for receiving yaw rate data and an output for transmitting an ESA output. In addition, the system includes an evasive steering controller configured to store yaw rate data over a period of time to initiate ESA based on one or more inputs. In response to determining to initiate ESA, the evasive steering controller determines a current position and a current heading angle of the host vehicle using the stored yaw rate data, determines a destination heading angle using the stored yaw rate data, and determines a destination position using the current position, wherein the evasive steering controller generates an evasive steering assistance (ESA) output based on the current position, the current heading angle, the destination position, and the destination heading angle. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 is a block diagram of an evasive steering assist (ESA) system, according to some embodiments.

[0007] Figure 2 is a block diagram visually illustrating utilizing yaw rate over a period of time to determine the orientation of a host vehicle in accordance with some embodiments.

[0008] Figure 3 is a block diagram of a queue used to store yaw rates according to some embodiments.

[0009] Figure 4 is a flow chart illustrating steps implemented by an ESA system according to some embodiments.

[0010] Figure 5 is a flow chart illustrating steps implemented by an EAS system for determining a destination position and a destination heading angle of a host vehicle and for calculating a current position and heading angle of the host vehicle, according to some embodiments. DETAILED DESCRIPTION

[0011] Systems and methods for providing evasive steering assistance (ESA) are disclosed herein. Specifically, the EAS system includes a queue for storing yaw rates associated with a vehicle over a given period of time. In some embodiments, the yaw rate queue is a recirculating queue in which a new value replaces the oldest value in the queue. The yaw rate queue can be used to determine a current heading angle and a destination heading angle, which can be used to calculate an additional steering torque provided as part of an ESA operation.

[0012] Figure 11 is a block diagram of an evasive steering assist (ESA) system 100 according to some embodiments. The ESA system 100 may include an evasive steering controller 101, which may include a processor 102 and a memory 104. In some embodiments, the evasive steering controller 101 receives one or more inputs and generates an ESA output 114 in response to the inputs. In some embodiments, the evasive steering controller is implemented in hardware, software, or a combination thereof. For example, the processor 102 may be a microprocessor capable of executing instructions stored on the memory 104 to implement various functions. In other embodiments, the processor 102 may be implemented as a programmable device, such as a field programmable gate array (FPGA). Similarly, the yaw rate queue may be implemented in hardware, software, or a combination thereof. In some embodiments, the yaw rate queue 106 may be a recirculating queue in which the queue length is fixed and the oldest data is overwritten by the newest data. In other embodiments, other types of queues may be implemented by the processor 102 and the memory 104. In some embodiments, the ESA system 100 utilizes inputs including a steering input 108 (e.g., steering torque, steering angle rate, lateral jerk, and / or lateral acceleration), a frontal collision warning (FCW) input 110, and yaw rate data 112 (for storage in the yaw rate queue 106). As described in more detail below, the steering input 108 is used to determine whether the driver has initiated an evasive steering. In some embodiments, the steering input may be a binary input that indicates whether the evasive steering has been initiated by the driver (e.g., true or false). In other embodiments, the steering input 108 may include raw data (e.g., steering torque, steering angle rate, lateral jerk, and / or lateral acceleration) that the evasive steering controller 101 analyzes to detect an evasive steering event. In other embodiments, the steering input 108 may include information about a steering maneuver, including a direction and magnitude of the steering maneuver, wherein the evasive steering controller 101 utilizes the received input to determine whether the driver has initiated an evasive steering maneuver. In some embodiments, the frontal collision warning input 110 is generated by a frontal collision detection system (not shown). The frontal collision detection system may use radar, laser (e.g., a light detection and ranging system or LiDAR system), camera, or a combination thereof to detect an imminent frontal collision. The FCW input 110 may be a binary input indicating the presence or absence of an imminent frontal collision, or may provide specific information regarding the time of collision, collision distance, size / shape of the object, etc. The evasive steering controller 101 may utilize the received data to determine whether the data indicates an imminent frontal collision.

[0013] As described in more detail below, in some embodiments, the steering input 108 and the FCW input 110 are utilized by the evasive steering controller 101 to detect an evasive maneuver. In response to the detected evasive maneuver and the detected forward collision, the ESA system 100 can generate an ESA output 114 that causes an additional steering torque to be superimposed on the steering torque applied by the driver to assist the driver in avoiding a collision with the object.

[0014] In situations where lane markings are not present to provide a heading angle to the host vehicle, then the yaw rate queue 106 may be used to determine the heading angle (and position) of the host vehicle. The heading angle refers to the direction in which the host vehicle is traveling. Part of the evasive maneuver includes determining the desired position and heading angle of the host vehicle at the end of the ESA maneuver (e.g., following the detected collision object and traveling in substantially the same heading as before). In some embodiments, the yaw rate data stored in the yaw rate queue 106 is used to make these determinations, such as with respect to Figure 3-Figure 5 discussed in more detail.

[0015] Figure 2 is a block diagram visually illustrating the use of yaw rate over a period of time to determine the orientation of the host vehicle to help avoid obstacles 202 in accordance with some embodiments. Figure 2 In the block diagram shown in , the yaw rate of the host vehicle 200 is measured at multiple instances over a period of time. Figure 2 In the embodiment shown in , the yaw rate of the host vehicle is calculated at five discrete instances 204a, 204b, 204c, 204d, and 204e within the time window 206. In other embodiments, any number of yaw rate calculations may be performed within a given time window. In some embodiments, the destination position and destination heading angle are determined by the ESA system 100 (indicated by the host position 208 being safely located next to the obstacle 202). As described in more detail below, in the absence of lane markings, the yaw rates stored in the yaw rate queue 106 are used to calculate the destination position and destination heading angle as well as the current position and current heading angle.

[0016] In some embodiments, the yaw rate queue 106 is a fixed length queue corresponding to the vision window 206 (eg, 3 seconds, 4 seconds). Figure 3is a block diagram visually illustrating a fixed length yaw rate queue 106, where the most recent measurements are added to the end 300 (position n) of the queue 106, and the oldest measurements are discarded from the front 302 (position 0) of the queue 106. Each entry in the queue stores the yaw rate of the host vehicle 200 at a particular moment in time, where the yaw rate may be defined as the rate of change of the heading angle or rotation of the host vehicle 200 about the z-axis (perpendicular to the ground).

[0017] Figure 4 4 is a flow chart illustrating steps implemented by the ESA system according to some embodiments. At step 400, the yaw rate queue 106 is initialized to begin storing yaw rate data. At step 402, the yaw rate queue 106 is updated to store received yaw rate data. At step 404, it is determined whether a frontal collision warning (FCW) has been received. Figure 1 As shown in , the evasive steering controller 101 may receive a FCW input 110. In some embodiments, the FCW input 110 indicates whether a frontal collision is imminent. In other embodiments, the FCW input 110 may include raw data that is analyzed by the evasive steering controller 101 to determine whether a frontal collision is imminent. In the event that a FCW has been received, the process continues to step 408 to determine whether the driver has initiated an evasive steering. If it is determined at step 404 that a FCW has not been received, the process continues at step 402 to update the yaw rate queue 106.

[0018] At step 408, it is determined whether the driver has initiated evasive steering. Figure 1 As shown in , the evasive steering controller 101 can receive a steering input 108 that identifies the presence of an evasive steering maneuver or provides an input (e.g., steering angle rate, steering torque, lateral acceleration, lateral jerk) used to determine the presence of an evasive steering maneuver. For example, the evasive steering controller 101 can compare one or more inputs to a threshold value to determine whether an evasive steering maneuver has been initiated. If the driver has not yet initiated an evasive steering, then evasive steering assist (ESA) is not initiated starting at step 410, and the process continues at step 402 to update the yaw rate queue 106. If the driver has initiated an evasive steering at step 408, then initiation of ESA begins at step 410. In some embodiments, initiation of ESA begins with determining at step 410 whether the host vehicle has made a lane change or active steering within a defined time period (e.g., the past few seconds). In some embodiments, the defined time period is related to the length of the yaw rate queue 106 (i.e., Figure 24. In some embodiments, the data stored in the yaw rate queue is used to determine whether a lane change or active steering has been initiated within a defined time period, and thus the length of the yaw rate queue can determine the time period available for review of lane change or active steering events. In other embodiments, the defined time period can be separate from the yaw rate queue, and other criteria or inputs can be used to detect lane change or active steering events. If the host vehicle has made a lane change or active steering maneuver, ESA is not initiated, and the process continues at step 402 to update the yaw rate queue 106. If it is determined at step 410 that the host vehicle has not made a lane change and / or initiated an active steering event, the ESA process continues at step 412. In some embodiments, lane change and / or active steering events occurring within a time frame (e.g., the last four seconds) reduce the accuracy of the heading angle estimation performed at step 412, and thus prevent the use of ESA initiation at steps 412-418. However, assuming that the host vehicle has not implemented any lane change and / or active steering time within the time frame, ESA can be initiated at step 412.

[0019] In other embodiments, the order of steps 404, 408, and 410 may be modified. For example, in some embodiments, determining whether the driver has initiated evasive steering at step 408 may occur before or after the determination of whether the FCW warning is received at step 404. In some embodiments, the lowest cost step (i.e., the lowest computational step) may be performed first to determine whether any subsequent analysis is required. In other embodiments, each step is performed almost simultaneously, with the decision of whether to initiate evasive steering assistance (ESA) depending on the results of the simultaneous analysis. In yet other embodiments, only a subset of steps 404, 408, and 410 is required to determine whether to initiate ESA. For example, in some embodiments, the initiation of ESA may depend solely on whether the FCW warning is detected at step 404, or solely on whether the driver has initiated evasive steering at step 408.

[0020] At step 412, the destination position and the destination heading angle are determined. Figure 2 , the destination position and the destination heading angle represent the desired position of the host vehicle at the end of the evasive steering maneuver, when the host vehicle may be safely located adjacent to the obstacle that caused the evasive steering maneuver (e.g. Figure 2106). In the case where lane markings are present, the lane markings can be used in combination with the locations of detected obstacles to determine the desired position and the desired heading angle. In the case where lane markings are not present, the yaw rate data stored by the yaw rate queue 106 can be used to calculate the desired position and the desired heading angle. In some embodiments, a heading angle is determined for each time step n stored in the yaw rate queue, and the heading angle at the oldest time step (i.e., the front of the queue) is assigned to zero. The heading angle at each time step associated with the stored yaw rate can be calculated by integrating the previous yaw rates. In this way, the current heading angle of the host vehicle can be determined at the current time step (i.e., when the evasive steering maneuver is initiated). Similarly, the heading angle determined at each time step can be used to estimate the destination heading angle. In some embodiments, the destination heading angle is calculated as the average of the heading angles determined at each time step, assuming that the overall orientation of the host vehicle measured over a period of time is the best estimate of the desired orientation or heading of the car after the evasive steering maneuver. Likewise, the host vehicle's current position (at the start of the evasive steering maneuver) may be assigned a value of zero.The host vehicle's destination point may be assigned a value based on the host vehicle's current position and a defined safety offset value (eg, 3 meters).

[0021] At step 414, a current position and heading angle are determined based on the yaw rate stored to the yaw rate queue 106. In some embodiments, the current position is calculated based on the previous position, previous heading angle, and speed of the host vehicle. The current heading angle is calculated based on the previous heading angle and the most recent yaw rate stored to the yaw rate queue 106. In some embodiments, the yaw rate queue 106 is continuously updated during the evasive steering maneuver, and thus the updating of the yaw rate queue 106 may continue at regular time intervals or frequencies. In some embodiments, determining the destination position and destination heading angle at step 412 and determining the current position and heading angle at step 414 are performed at about the same time. In some embodiments, the current position and heading angle are continuously recalculated at step 414, while the destination position and destination heading angle are calculated only once at step 412.

[0022] At step 416, an ESA output is generated based on the current position and heading angle determined at step 414 and the desired position and heading angle calculated at step 412. In some embodiments, a proportional-integral-derivative (PID) control scheme can be used to minimize the error between the current position / heading angle and the destination position / heading angle. In other embodiments, other types of control schemes can be used to generate an ESA output to minimize the difference between the current position and heading angle of the vehicle and the destination position and heading angle (i.e., in order to guide the car to the desired destination position and destination heading). As described above, the ESA output overlays the additional steering torque on the steering torque applied by the driver, thereby helping the main vehicle to perform evasive maneuvers. In some embodiments, the ESA output is provided to a steering system, wherein the ESA output calculated at step 416 determines the direction and magnitude of the additional steering torque overlaid on the steering torque applied by the driver.

[0023] At step 418, it is determined whether to end the ESA intervention. If it is determined at step 418 to continue the ESA intervention, the ESA intervention continues by recalculating the current position and heading angle at step 414 and generating new ESA outputs at step 416. If it is determined at step 418 to end the ESA intervention, the process ends at step 420. Additional ESA outputs are not generated, and after the particular ESA intervention ends, the process will restart at step 400.

[0024] In some embodiments, ESA intervention is limited to a specific length of time. In this embodiment, it is determined at step 418 whether the ESA time period has expired. For example, in some embodiments, the ESA timer is started in response to the initiation of ESA, and the ESA timer is compared with a threshold value (e.g., 1-3 seconds) at step 418 to determine whether to end the ESA intervention. If the time limit for ESA intervention is not reached, the process continues by recalculating the current position / heading angle at step 414 and controlling the ESA output generated at step 416. In other embodiments, it is determined whether to end the ESA intervention based on whether the current position heading angle is approximately equal to the destination position and the destination heading angle. That is, once the vehicle arrives at the destination position and the destination heading angle, no additional ESA intervention is required. In some embodiments, a combination of methods can be utilized at step 418. For example, the process can end in response to the vehicle arriving at the destination position and heading angle or in response to the expiration of the timer. In this way, the ESA intervention is limited to a time length not exceeding the ESA timer, but can be terminated more quickly in response to the vehicle arriving at the desired destination position and heading angle.

[0025] Figure 51 is a flow chart showing steps implemented by an EAS system for determining a destination position and a destination heading angle of a host vehicle and for calculating a current position and heading angle of the host vehicle according to some embodiments. According to some embodiments, steps 500, 502, and 504 are used to determine the destination position and the destination heading angle. According to some embodiments, step 506 shows the calculation of the current point and the current heading angle.

[0026] Specifically, the heading angle for the past n steps is recursively calculated at step 500. For example, the heading angle at the earliest time step (i.e., time zero) is set equal to zero (h(0) = 0). The heading angle at the next time step (i.e., time n=1) is calculated based on the previous heading angle (in this case, h(0) = 0) and the integral of the yaw rate relative to the host vehicle stored at time step zero. For example, as shown in step 500, at t=1, the heading angle is calculated as h(1) = h(0) + yawrate_queue(0)*dt. This calculation is performed iteratively for each time step. Therefore, for time step n, the heading angle is calculated as h(n) = h(n-1) + yawrate_queue(n-1)*dt.

[0027] At step 502, the starting point position and starting heading angle are determined at the start of the evasive steering maneuver (corresponding to the current time step or position of the host vehicle). The starting point position (in the y direction) is initialized to zero (e.g., Y_0 = 0) relative to the starting point position. Likewise, the starting heading angle is initialized to the heading angle calculated at the current time step (e.g., heading_start = h(n)), where the value of h(n) is calculated as described at step 500.

[0028] At step 504, the destination point position and the destination heading angle are determined. The destination point position is calculated based on the starting point position and some offsets (e.g., safety offsets) corresponding to the safe distance to the detected obstacle. For example, in some embodiments, the destination point position is calculated as Y_destination = Y_0 + safety_offset. In addition, the destination heading angle is calculated based on the average of the heading angles calculated before the evasive maneuver is initiated. For example, in some embodiments, the destination heading angle is calculated as heading_destination = average value (h(0), …, h(n)). Therefore, the destination heading angle (i.e., the desired heading angle at the end of the evasive maneuver) is calculated to be approximately equal to the average heading angle of the host vehicle in the seconds before the initiation of the evasive maneuver begins, assuming that before the ESA is initiated, no matter what heading angle the host vehicle is at (represented by the average value of the measured heading angles), the same heading should be provided at the end of the evasive maneuver.

[0029] At step 506, the current position and current heading angle of the host vehicle are calculated. In some embodiments, the current position and current heading angle are calculated recursively. For example, the current position can be calculated as Y_current = Y_previous + heading angle_previous * host vehicle_speed * dt. That is, for each time step, the main heading angle and the speed of the host vehicle at the previous time step are used to calculate the position of the host vehicle in the y direction.

[0030] Although the present invention has been described with reference to one or more exemplary embodiments, it will be appreciated by those skilled in the art that various changes may be made and elements thereof may be substituted with equivalents without departing from the scope of the present invention. In addition, many modifications may be made to adapt specific circumstances or materials to the teachings of the present invention without departing from the essential scope of the present invention. Therefore, the present invention is not limited to one or more specific embodiments disclosed, but the present invention will include all embodiments falling within the scope of the appended claims.

Claims

1. A method for providing evasive steering assistance (ESA), the method comprising: storing yaw rate data associated with the host vehicle, wherein the yaw rate data includes yaw rates stored at a plurality of time steps from an initial time step [0] to a current time step [n]; Determine whether to initiate Evasive Steering Assist (ESA); responsive to determining to initiate evasive steering assistance (ESA), calculating a current position, a current heading angle, a destination position, and a destination heading angle, wherein the stored yaw rate data is used to determine the current heading angle and the destination heading angle, wherein the current heading angle is the heading angle at time step [n]; and An evasive steering assist (ESA) output is generated based on the current position, the current heading angle, the destination position, and the destination heading angle, the evasive steering assist (ESA) output resulting in an additional steering torque superimposed on a driver-applied steering torque.

2. The method according to claim 1, characterized in that Determining whether to initiate evasive steering assist (ESA) includes determining whether a frontal collision is imminent, wherein evasive steering assist (ESA) is initiated in response to determining that the frontal collision is imminent.

3. The method according to claim 1, characterized in that Determining whether to initiate evasive steering assist (ESA) includes determining whether a driver of the host vehicle has initiated evasive steering, wherein evasive steering assist (ESA) is initiated in response to determining that the driver has initiated evasive steering.

4. The method according to claim 1, characterized in that Determining whether to initiate evasive steering assist (ESA) includes determining whether a driver of the host vehicle has completed an active steering maneuver within a given time period, wherein evasive steering assist (ESA) is initiated in response to the driver not having completed an active steering maneuver within the given time period.

5. The method according to claim 1, characterized in that Calculating the current heading angle includes: The heading angle of the host vehicle is recursively calculated based on the stored yaw rate data, wherein the heading angle at the initial time step [0] is designated as the initial heading angle, and subsequent heading angles are calculated based on the integral of the yaw rate stored at each time step, wherein the heading angle at the current time step [n] is designated as the current heading angle.

6. The method according to claim 5, characterized in that The destination heading angle is calculated as an average of a plurality of heading angles calculated at each time step within a given time period.

7. The method according to claim 6, characterized in that The destination position is calculated as a sum of the current position of the host vehicle and a safety offset value, wherein the position of the host vehicle represents a lateral position of the host vehicle.

8. The method according to claim 7, characterized in that The current position of the host vehicle is updated at each time step based on a previous position of the host vehicle, a previous heading angle of the host vehicle, and a speed of the host vehicle.

9. The method according to claim 8, characterized in that The current heading angle of the host vehicle is updated at each time based on a previous heading angle and a yaw rate measured at the current time step.

10. The method of claim 1, further comprising: The evasive steering assist (ESA) is terminated in response to expiration of an evasive steering assist (ESA) timer, wherein the evasive steering assist (ESA) timer is initiated when the evasive steering assist (ESA) is initiated.

11. The method of claim 1, further comprising: The evasive steering assist (ESA) is terminated in response to the current position and the current heading angle being equal to the destination position and the destination heading angle.

12. The method according to claim 1, characterized in that The evasive steering assist (ESA) output is generated to minimize a difference between the current position and the destination position, and to minimize a difference between the current heading angle and the destination heading angle.

13. A system for providing evasive steering assistance (ESA) to a host vehicle, the system comprising: a first input for receiving yaw rate data; an evasive steering controller configured to store yaw rate data over a period of time from an initial time step [0] to a current time step [n] to initiate an evasive steering assist (ESA) based on one or more inputs, wherein in response to determining to initiate evasive steering assist (ESA), the evasive steering controller determines a current position and a current heading angle of the host vehicle using the stored yaw rate data, wherein the current heading angle is the heading angle at time step [n], determines a destination heading angle using the stored yaw rate data, and determines a destination position using the current position, wherein based on the current position, the current heading angle, the destination position, and the destination heading angle, the evasive steering controller generates an evasive steering assist (ESA) output; as well as An output is provided for transmitting the evasive steering assist (ESA) output, the evasive steering assist (ESA) output resulting in an additional steering torque superimposed on the driver applied steering torque.

14. The system of claim 13, further comprising: One or more inputs for receiving one or both of a forward collision warning (FCW) and a steering input, wherein the evasive steering controller determines whether to initiate evasive steering assist (ESA) in response to one or both of the forward collision warning (FCW) and the steering input.

15. The system of claim 14, wherein: The evasive steering controller initiates evasive steering assist (ESA) in response to a received forward collision warning (FCW) and a steering input indicating that a driver of the host vehicle has initiated evasive steering.

16. The system of claim 14, wherein: The evasive steering controller recursively calculates the heading angle of the host vehicle based on the stored yaw rate data, wherein the heading angle at an initial time step [0] is designated as an initial heading angle, and subsequent heading angles are calculated based on an integral of the stored yaw rate at each time step, wherein the heading angle at a current time step [n] is designated as the current heading angle.

17. The system of claim 16, wherein: The destination heading angle is calculated as an average of a plurality of heading angles calculated at each time step within a given time period.

18. The system of claim 17, wherein: The destination position is calculated as a sum of the current position of the host vehicle and a safety offset value, wherein the position of the host vehicle represents a lateral position of the host vehicle.

19. The system of claim 13, wherein: The evasive steering controller generates the evasive steering assist (ESA) output to minimize a difference between the current position, current position heading angle and the destination position, destination heading angle.

20. The system of claim 13, wherein: The evasive steering controller ends an evasive steering assist (ESA) in response to an ESA timer reaching a threshold.

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