JP2012056399A - Rear side steering support technology - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reliably reduce the collision risk with a peripheral object without any sense of incongruity of a driver in a vehicle having a mechanism capable of variably changing the steering angle ratio.SOLUTION: An object present around a vehicle is detected, the distance to the object is calculated, and the relative speed of the object and the time allowance before the vehicle reaches the object is estimated. The vehicle has a steering angle ratio control means capable of variably controlling the steering angle ratio which is the ratio of the turning angle of steered wheels to the steering angle to be input in a steering wheel of the vehicle. The steering angle ratio control means reduces the steering angle ratio as (1) the distance is smaller, (2) the relative speed is higher, or (3) the time allowance is smaller. Thus, the collision risk of the vehicle with the object is reliably reduced in the vehicle capable of variably changing the steering angle ratio.

Description

  The present invention relates to an apparatus for assisting steering of a vehicle driver to avoid an object around the vehicle.

  Conventionally, a mirror has been provided in a vehicle as a support for the blind spot on the rear side, and recently, a radar or a camera attached to the vehicle detects an object such as another vehicle in the outside world. It has been proposed to notify the driver. In addition to notifying the driver, it has also been proposed to control the running of the vehicle to avoid objects, for example via brake control.

  On the other hand, recently, a mechanism capable of variably controlling the steering angle ratio (also referred to as a steering ratio, a steering gear ratio, etc.) has been proposed. In Patent Document 1 below, there is provided means capable of variably changing the steering gear ratio, and when it is determined that the vehicle may collide with an obstacle ahead, the steering gear ratio is calculated based on the travel path width. It is described that the value is controlled to be smaller than the value to be changed.

JP 2008-44427 A

  By providing a mechanism capable of variably changing the steering angle ratio as described above, the operability of the vehicle by the driver can be improved. However, if the steering angle ratio is changed when there is a possibility of collision with surrounding objects due to the driver's steering, there is a possibility of causing a steering amount against the driver's intention, and the object will be inadvertently approached. There is a fear. In particular, if the rudder angle ratio is increased and the tire turning angle (steering angle) is increased under such circumstances, the time until the collision with the object is shortened and the risk of collision may be increased. is there.

  Therefore, in a vehicle equipped with a mechanism that can change the rudder angle ratio variably, there is a demand for a method that can reliably reduce the risk of collision with surrounding objects without causing the driver to feel uncomfortable.

  According to one aspect of the present invention, means for detecting an object existing around a vehicle, means for calculating a distance from the vehicle to the object, means for calculating a relative speed of the object with respect to the vehicle, Steering angle ratio for variably controlling a steering angle ratio, which is a ratio of a steering angle of a steering wheel to a steering angle input to the steering wheel of the vehicle, and means for estimating a margin time until the vehicle reaches the object The steering angle ratio control means includes: 1) the smaller the distance, 2) the greater the relative speed, or 3) the smaller the margin time, the steering angle ratio control means. Make it smaller.

  According to the present invention, the steer angle ratio is reduced as the distance to the object is decreased, the relative speed of the object is increased, or the margin time until reaching the object is decreased. The turning angle (steering angle) becomes smaller. Therefore, since the tires are not cut more than actual steering, it is possible to earn time and distance until reaching the object, and in the meantime, the driver can be noticed by an alarm or the like. In addition, the collision risk can be reliably reduced while protecting the driver's operation intention (intention to turn in a desired direction).

  According to an embodiment of the present invention, the steering angle ratio control means is in the straight traveling state if it is determined that the vehicle is in the straight traveling state when the reduced steering angle ratio is restored. Compared to the case where it is not determined, the time for returning the steering angle ratio is shortened.

  Even after the collision risk is resolved, the vehicle can be returned to the normal running state without causing the driver to feel uncomfortable by a natural action of returning the steering angle ratio. Further, if the vehicle is in a straight traveling state, there is no risk of a collision due to the turning of the vehicle, so that the steering angle ratio can be immediately returned to quickly return to the normal traveling state.

  Other features and advantages of the present invention will be apparent from the detailed description that follows.

The block diagram which shows the structure of the driving assistance device of the vehicle according to one Example of this invention. The figure which shows an example of the condition where the driving assistance device according to one Example of this invention can be applied. The figure which shows an example of transition of the input steering angle according to one Example of this invention, the output steering angle according to the parameter showing the risk state of a vehicle, and a steering angle ratio. The flowchart of the driving assistance process according to one Example of this invention.

  Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a driving support apparatus mounted on a vehicle according to an embodiment of the present invention.

  The external sensor 1 is attached to an appropriate location of the vehicle so as to detect an object existing in a desired direction around the vehicle. In this embodiment, the external sensor 1 is attached to the left and right sides of the vehicle (for example, in the vicinity of the door mirror) so as to detect an object present on the left and right sides of the vehicle (may be the left and right rear sides).

  The external sensor 1 can be configured to include a radar device and / or an imaging device using electromagnetic waves such as millimeter waves and lasers. Here, the radar apparatus can be realized by any known appropriate radar apparatus. For example, the radar device transmits an electromagnetic wave transmission signal so as to scan a detection target region set in the external environment of the host vehicle. The transmission signal is received by a reflection signal generated by reflection from an object outside the host vehicle (for example, another vehicle or structure), and a signal indicating a distance and direction to the object is generated and processed. Output to unit 10. In addition, the imaging device can be realized by any known appropriate imaging device. The imaging device acquires an image captured by one or more cameras and outputs the image data to the processing unit 10.

  The vehicle speed sensor 3 is a sensor that detects the traveling speed (vehicle speed) of the vehicle, the yaw rate sensor 5 is a sensor that detects the yaw rate of the vehicle, and these detected values are sent to the processing unit 10.

  The processing unit 10 and the EPS (electric power steering) control unit 20 can be realized by an electronic control unit (ECU) which is a computer including a central processing unit (CPU) and a memory, respectively. In the figure, functions realized by the processing unit 10 and the EPS control unit 20 are represented as blocks. In this embodiment, the processing unit 10 includes an object detection unit 11, a distance calculation unit 12, a relative speed calculation unit 13, a TTC (room time) calculation unit 14, a predicted trajectory calculation unit 15, a steering angle ratio change unit 16, and a determination. The unit 17 is provided. The EPS control unit 20 includes a steering angle ratio determination unit 21.

  In a vehicle, a steering angle ratio in which a ratio of a steering angle (tire turning angle) of a steering wheel (hereinafter referred to as a steering angle ratio) to a steering angle input to a steering wheel (steering wheel) can be changed variably. An electric power steering mechanism 30 including a variable gear ratio steering (VGS) device 31 is provided.

  The steering angle ratio determination unit 21 of the EPS control unit 20 determines the steering angle ratio by any known method. For example, the steering angle ratio can be set according to the vehicle speed. For example, the steering angle ratio is set to be small when traveling at high speeds to ensure stable turning behavior, and the steering angle ratio is increased during low speed traveling. , Agile turning behavior can be ensured. The EPS control unit 20 sends a control signal indicating the steering angle ratio thus determined to the steering angle ratio variable device 31 of the steering mechanism 30. In response to this, the steering angle ratio variable device 31 receives the received steering angle. Realize the ratio. Thus, the steering angle input to the steering wheel by the driver's operation is converted into the steering angle of the steering wheel according to the steering angle ratio, and the steering wheel is driven according to the converted steering angle. As the rudder angle ratio increases, the tire turning angle (steering angle) increases with the same steering operation.

  The steering angle ratio variable device 31 as described above is described in, for example, Japanese Patent Application Laid-Open Nos. 2010-167842 and 2010-95153. In this embodiment, the steering angle ratio variable device is used to change the steering angle ratio. Alternatively, the steering system and the steering wheel are mechanically separated, and the steering input to the steering wheel is performed. You may use what is called a steer-by-wire (SBW) apparatus which steers a steering wheel with an actuator etc. according to a corner | angular. In this case, for example, the steering angle is converted into a steering angle according to the steering angle ratio determined by the EPS control unit, and this is reflected on the steering wheel by an actuator or the like.

  In this embodiment, the steering angle ratio determined as described above is changed according to the processing result by the processing unit 10. The steering angle ratio changing process will be specifically described below.

  The object detection unit 11 detects an object present around the vehicle from the output signal of the external sensor 1. For example, another vehicle can be detected as an object. For example, an object such as another vehicle can be detected by a known method based on the output signal from the radar device and the image data from the imaging device.

  The distance calculation unit 12 calculates the distance (relative distance) from the host vehicle to the object detected by the object detection unit 11. The relative speed calculation unit 13 calculates the relative speed of the object with respect to the host vehicle based on the detected speed of the object and the speed of the host vehicle. The speed of the object can be calculated by temporally tracking the object with the external sensor 1. The speed of the host vehicle can be detected by the vehicle speed sensor 3.

  The predicted trajectory calculation unit 15 estimates (predicts) the future trajectory of the host vehicle based on the speed of the host vehicle detected by the vehicle speed sensor 3 and the yaw rate of the host vehicle detected by the yaw rate sensor 5. Specifically, the predicted trajectory calculation unit 15 calculates the turning radius of the vehicle from the detected yaw rate and vehicle speed, and connects the arc of the calculated turning radius to the current traveling direction of the host vehicle, thereby A future travel locus of the vehicle can be predicted.

  The TTC calculation unit 14 calculates a time required to reach an object of the host vehicle (referred to as a time to collision (TTC)). For example, the intersection of the predicted trajectory calculated by the predicted trajectory calculation unit 15 and the trajectory when it is assumed that the detected object has traveled while maintaining the current speed and direction is obtained, and the host vehicle reaches the intersection. The time until this can be obtained as the margin time TTC.

  Referring now to FIG. 2 (a), there is shown an example of a situation where there is a possibility of collision with an object by a driver's steering (turning) operation, to which the present invention can be effectively applied. The host vehicle V1 is traveling in the lane 1, and the other vehicle V2 is traveling in the lane 2 adjacent to the lane 1. The own vehicle V1 is provided with an external sensor 1 so as to detect an object on the left side of the vehicle. Therefore, the external sensor 1 can detect another vehicle V2. Thereby, the distance d to the other vehicle V2 and the relative speed ve of the other vehicle V2 are calculated.

  The vehicle V1 enters an operation of changing the lane from the lane 1 to the lane 2, and the predicted trajectory calculation unit 15 predicts the trajectory of the vehicle V1 to the lane 2 as described above. The predicted trajectory is indicated by a dotted line dL1. On the other hand, the other vehicle V2 travels straight in the lane 2 and the trajectory is estimated as indicated by the dotted line dL2. The intersection point I between the trajectories dL1 and dL2 is calculated, and the time TTC until the vehicle V1 reaches the intersection point I is calculated based on the distance from the current position of the vehicle V1 to the intersection point I and the current vehicle speed of the vehicle V1. be able to. Alternatively, the time until the vehicle V1 enters the lane V2 may be calculated as the margin time TTC.

  The steering angle ratio changing unit 16 changes the steering angle ratio based on one or more of the calculated distance d, relative speed ve, and margin time TTC. Specifically, when the distance d is equal to or less than a predetermined value, the relative speed ve is equal to or greater than the predetermined value, or the margin time TTC is equal to or less than the predetermined value, the object avoidance is supported. The steering angle ratio changing process is started. During the rudder angle ratio change process, the rudder angle ratio change unit 16 uses the rudder angle ratio determined by the rudder angle ratio determination unit 21 when entering the rudder angle ratio change process as a reference (this rudder angle ratio is changed). A predetermined steering angle ratio change signal so that the steering angle ratio decreases as the distance d decreases, the relative speed ve increases, or the margin time TTC decreases. Is sent to the EPS control unit 20. In response to the signal, the steering angle ratio determination unit 21 instructs the steering angle ratio variable device 31 to change the steering angle ratio. As a result, the tire turning angle with respect to the steering angle of the steering wheel is reduced. Even with the same steering, the tires are hard to run out, so that it is possible to give a margin to the distance and time to reach the object, and in the meantime, for example, an alarm is given to the driver, and the driver's voluntary Evasive behavior can be encouraged.

  Although the steering angle ratio is reduced, the driver's intention to operate (willingness to turn in the desired direction) is maintained, and the steering force is not forcibly increased or decreased. It is possible to support the avoidance action for the object.

  The degree of change of the steering angle ratio by the steering angle ratio changing unit 16 can be set by any appropriate method. For example, the degree of change in the steering angle ratio at a time (which can be expressed by a numerical value) is determined in advance. As the distance d becomes smaller (for example, every time the current value of the distance d becomes smaller than the previous value), the steering angle ratio can be decreased by a predetermined value. A similar method can be used for the relative speed and the margin time.

  When the rudder angle ratio changing unit 16 determines that the state of the risk of collision of the vehicle with respect to the object has been reduced or eliminated, the rudder angle ratio changed as described above is changed to the original rudder at the start of the rudder angle ratio changing process. The angle ratio is gradually returned (for example, by a predetermined value). The state of collision risk can be represented by a distance d, a relative speed ve, and a margin time TTC. For example, as the distance d increases, as the relative speed ve decreases, or as the margin time TTC increases, the steering angle ratio gradually increases (ie, returns to the original steering angle ratio). A steering angle ratio change signal can be sent to the EPS control unit 20.

  Preferably, a determination unit 17 is provided, and the determination unit 17 determines whether or not the vehicle is running straight. The determination of whether or not the vehicle is in the straight traveling state can be performed by any appropriate method, and can be determined based on, for example, a steering angle sensor attached to the steering wheel. The steering angle ratio changing unit 16 determines that the vehicle is in a straight traveling state by the determination unit 17 when determining that the collision risk state of the vehicle is reduced or eliminated. The steering angle ratio change signal is sent to the EPS control unit 20 so as to return immediately rather than gradually. Thereby, the steering angle ratio determination part 21 controls the steering angle ratio variable apparatus 31 so that it may become a steering angle ratio when a steering angle ratio change process is started. This is done because there is no possibility of collision with an object due to the steering (turning) operation of the vehicle when the vehicle is in a straight traveling state.

  If it returns to the original steering angle ratio, the steering angle ratio changing process ends. The steering angle ratio changing unit 16 notifies the EPS control unit 20 of the end of the changing process. In response to this, the steering angle ratio determination unit 21 determines the steering angle ratio by a normal method (for example, based on the vehicle speed as described above), and controls the steering angle ratio variable device 31 accordingly. .

  FIG. 3 shows an example of the transition of the steering angle ratio when the distance d is used as a parameter representing the collision risk state of the vehicle. The input steering angle indicates the steering angle input to the steering wheel, and the output steering angle indicates the tire turning angle (steering angle) after the steering angle is converted according to the steering angle ratio. During the time t1 to t2, the steering angle ratio is determined in the normal process. Here, the steering angle ratio is a predetermined value, and the input steering angle is the output steering angle according to the predetermined steering angle ratio. Has been converted.

  At time t2, the steering angle ratio changing process is started in response to the distance d to the object being equal to or less than the predetermined value TH1, and the steering angle ratio is decreased as the distance d is decreased. As a result, since the ratio of the output turning angle to the input steering angle becomes small, an increase in the output turning angle is suppressed after time t2 as compared with the time t1 to t2. Therefore, although the increase amount with respect to the time of the input steering angle is constant, the movement of the tire becomes slow, and the decrease amount with respect to the time of the distance d is suppressed (solid line).

  If the steering angle ratio reduction process as described above is not performed, the output steering angle increases in proportion to the input steering angle at the same rate as the times t1 to t2, so that the dotted line indicates The distance d decreases rapidly. When the distance d reaches zero, it indicates a collision with the object, but the distance and time required to reach the object can be given by the process of reducing the steering angle ratio. Therefore, it becomes possible to make the driver aware by giving an alarm to the driver during this period, and to promote spontaneous avoidance behavior.

  FIG. 4 shows a flowchart of a process performed by the driving assistance device according to an embodiment of the present invention. The process can be performed at predetermined time intervals. In this example, margin time TTC and distance d are used as parameters representing the risk state of the vehicle.

  In step S11, the outputs of the external sensor 1, the vehicle speed sensor 3, and the yaw rate sensor 5 are acquired. In step S12, an object is detected based on the output of the external sensor 1. In step S13, the distance d of the detected object from the host vehicle is calculated. In step S14, as described above, for example, based on the vehicle speed and the yaw rate, the traveling locus of the vehicle is predicted and the detected object is detected. Calculates the travel trajectory of the object on the assumption that the current speed and direction are maintained, and based on this and the travel trajectory predicted for the host vehicle, the time until the host vehicle reaches the object is calculated. Is calculated as a margin time TTC.

  In step S15, it is determined whether or not the calculated distance d is equal to or less than a predetermined value TH1. If this determination is No, the detected object exists relatively far away, and it is not necessary to change the steering angle ratio, so the process ends. If this judgment is Yes, it will progress to Step S16.

  In step S16, it is determined whether or not the calculated margin time TTC is equal to or less than a predetermined value TH2. When this determination is No, an object exists where the distance d is small but the margin time TTC is large. In this case, in step S17, the steering angle ratio is reduced according to the size of the distance d. For example, the amount by which the rudder angle ratio is reduced according to the size of the distance d can be determined in advance by storing it in a map or the like, for example. Based on the calculated distance d, a corresponding reduction amount of the steering angle ratio is obtained, and a steering angle ratio change signal indicating the reduction amount is sent to the EPS control unit 20. Thus, the steering angle ratio determined in the normal process is reduced according to the amount of decrease, and the result is reflected on the steering wheel via the steering angle ratio variable device 31. For example, although there is no danger of a collision because the margin time TTC is large, in a situation where the surroundings of the host vehicle are congested, the steering angle ratio is reduced in advance by the processing in step S17, and steering is actually performed. It is possible to suppress an increase in the risk of collision when broken.

  If the determination in step S16 is Yes, it indicates that an object exists where the distance d is small and the margin time TTC is small. In step S18, the previous risk is compared with the current risk, and in step S19, it is determined whether the risk has increased as a result of the comparison. For example, the margin time TTC calculated when the process was executed last time is compared with the margin time TTC calculated this time, and if the current value is smaller than the previous value, it is determined that the risk is increased. be able to. When the step is executed for the first time, since the previous value does not exist, the determination result can be Yes.

  If it is determined that the risk has increased, the steering angle ratio is decreased by one step in step S20. Here, the “stage” is a predetermined reduction amount. Therefore, each time step S20 is executed, the steering angle ratio is decreased by a predetermined amount. In step S21, a strong warning is issued to make the driver aware that he is approaching the object. The alarm can be issued in any suitable manner, for example, an audible, visual and / or tactile notification.

  If it is determined in step S19 that the risk has not increased, it indicates that at least the margin time TTC has not decreased. In step S22, it is determined whether the steering angle ratio is the original (normal) steering angle ratio. As described above, the “original rudder angle ratio” is the rudder angle ratio when the rudder angle ratio change process is started, in other words, the rudder angle ratio immediately before the change in step S20 is first performed in the process. Show.

  If the determination in step S22 is No, it is determined in step S23 whether the vehicle is traveling straight. If the vehicle is not in a straight traveling state, there is still a possibility of approaching an object due to turning of the vehicle. Therefore, in step S25, the steering angle ratio is increased by one step toward the original steering angle ratio (that is, determined in advance). Increase only the increase amount). Thus, under a situation where the risk is not increased, the steering angle ratio returns to the original value by a predetermined amount each time step S25 is executed. Thereby, the influence of the behavior of the vehicle due to the sudden return of the steering angle ratio can be avoided. If the rudder angle ratio returns to the original value, the determination in step S22 is Yes and the process is terminated.

  On the other hand, if the vehicle is in a straight traveling state under a situation where the risk has not increased, there is no risk of colliding with an object due to the steering operation. Therefore, in step S24, the steering angle ratio is immediately returned to the original steering angle ratio. Even if the vehicle is returned immediately, the vehicle behavior is not affected unless the vehicle is turning. Thus, it is possible to quickly return to the normal traveling state.

  Thus, in this example, the steering angle ratio is reduced as the margin time TTC is reduced. When reaching a situation where the margin time TTC does not become small, the steering angle ratio is restored. While respecting the driver's intention to steer (which one he wants to turn to), the steering angle ratio assists in avoiding objects, and when the risk is resolved, the driver automatically returns to the normal steering angle ratio. It is possible to avoid a sense of incongruity.

  Furthermore, in this example, the distance d is used to examine a sign of danger. That is, even if the distance d is small, if the margin time TTC is large, there is no guarantee that there is a risk of a collision immediately (for example, the vehicle travels substantially straight, but there is a vehicle on the side. In the case of steering, the risk increases at a stretch. Therefore, in such a case, as shown in step S17, it is possible to prepare for such danger by lowering the steering angle ratio in advance. Although not shown in the figure, when the steering angle ratio is reduced in step S17, a step of returning the reduced steering angle ratio to the original value when the distance d becomes larger than the predetermined value TH1 may be inserted. .

  In the flowchart of FIG. 4, the steering angle ratio is made smaller as the margin time TTC becomes smaller. Of course, the distance d and the relative speed ve may be used instead of the margin time TTC of the flow. In this flow, the distance d is used to check whether there is a risk sign, and the steering angle ratio is reduced in advance. However, the margin time TTC and the relative speed ve are used instead of the distance d. May be.

  Further, in this flow, when the condition that the margin time TTC is changed in the decreasing direction is satisfied in steps S18 and S19, the steering angle ratio is reduced (S20). 1) the margin time TTC is changing in the direction of decreasing, 2) the distance d is changing in the direction of decreasing, and 3) the relative speed ve is increasing in the direction of increasing. The steering angle ratio may be reduced when one or more of the conditions are satisfied. For example, A) When the distance d is smaller than the previous value, or when the margin time TTC is smaller than the previous value, the steering angle ratio is decreased, or B) the distance d is smaller than the previous value, or the relative speed Reduce the steering angle ratio when ve becomes larger than the previous value, or C) Decrease the steering angle ratio when the margin time TTC becomes smaller than the previous value or the relative speed ve becomes larger than the previous value. Can be. When the plurality of conditions are used, when all of the plurality of conditions are not satisfied, Step S19 becomes No, and the steering angle ratio is returned in Step S24 or S25. For example, in the case of the above A), when the distance d is equal to or greater than the previous value and the margin time TTC is equal to or greater than the previous value, the steering angle ratio is returned by step S24 or S25. The same applies to the cases B) and C).

  In the above embodiment, another vehicle is detected as an object as shown in FIG. 2, but the object is not limited to the vehicle, and includes other moving objects such as bicycles. Objects can also be included.

  As described above, specific embodiments of the present invention have been described. However, the present invention is not limited to these embodiments.

1 External sensor 10 Processing unit 20 EPS control unit 30 Steering mechanism 31 Steering angle ratio variable device

Claims (2)

Means for detecting an object present around the vehicle;
Means for calculating a distance from the vehicle to the object;
Means for calculating a relative speed of the object with respect to the vehicle;
Means for estimating a margin time until the vehicle reaches the object;
A steering angle ratio control means for variably controlling a steering angle ratio, which is a ratio of a steering angle of a steering wheel to a steering angle input to the steering wheel of the vehicle,
The rudder angle ratio control means 1) reduces the rudder angle ratio as the distance is smaller, 2) the relative speed is larger, or 3) the margin time is smaller. apparatus. The steering angle ratio control means, when returning the reduced steering angle ratio, if the vehicle is determined to be in a straight traveling state, compared to a case where it is not determined to be in the straight traveling state, Shorten the time to return the rudder angle ratio,
The driving support device according to claim 1.

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