JP2007008402A - Operation assisting device for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a necessary assist torque when operation of avoiding an obstacle is carried out, while minimizing the incompatible feeling of a driver due to the assist torque of an operation assisting device for a vehicle. <P>SOLUTION: When a collision avoiding operation determining means M2 determines collision avoiding operation by a driver, an avoiding momentum calculating means M4 calculates avoiding momentum required by a vehicle for avoiding an obstacle. A target assist current is corrected by the avoiding momentum. In case where an absolute value of a yaw rate deviation is not more than a threshold value and a vehicular behavior is stable, a correcting coefficient calculating means M8 reduces the target assist current, so that the incompatible feeling of the driver due to excessive assist can be resolved. The reducing amount of the target assist current when the collision avoiding operation by the driver is determined, is set to be smaller than that when not determined, so that the target assist current is made hard to be reduced in an emergency when the collision avoiding operation has been carried out, thereby certainly avoiding the obstacle. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a vehicle operation support device that supports a collision avoidance operation performed by a driver to avoid a collision with an obstacle when the vehicle is traveling.

When the vehicle is approaching the limit of understeer turning and turning the steering wheel further, there is a risk of disturbing the vehicle behavior. Thus, it is known from Patent Document 1 below that the driver is informed that the vehicle is approaching the turning limit, and that the steering wheel is prevented from being disturbed by preventing the vehicle behavior from being disturbed.
JP 2004-352031 A

  By the way, in the above-mentioned conventional system, the assist torque is not corrected in the oversteer state, so that the driver may feel uncomfortable, and when the obstacle avoidance operation is performed, the steering reaction force becomes large and quick avoidance is achieved. Operation could be hindered.

  The present invention has been made in view of the above circumstances, and it is possible to obtain a necessary assist torque when performing an obstacle avoidance operation while minimizing a driver's uncomfortable feeling due to the assist torque of the vehicle operation support device. The purpose is to.

  In order to achieve the above object, according to the first aspect of the present invention, in a vehicle operation support device that supports a collision avoidance operation performed by a driver to avoid a collision with an obstacle when the vehicle is running, Reference yaw rate calculation means for calculating a reference yaw rate, collision avoidance operation determination means for determining a collision avoidance operation by a driver, obstacle detection means for detecting an obstacle with which the host vehicle may collide, and collision avoidance operation determination When the means determines the collision avoidance operation by the driver, the avoidance exercise amount calculating means for calculating the avoidance exercise amount necessary for avoiding the obstacle detected by the obstacle detection means, and the reference yaw rate calculated by the reference yaw rate calculation means The normative yaw rate correcting means for correcting with the avoiding momentum calculated by the avoiding momentum calculating means, and the Target assist current calculating means for calculating a target assist current to be supplied to the steering actuator based on the yaw rate deviation, and reducing the target assist current when the absolute value of the yaw rate deviation is less than or equal to a threshold value A vehicle operation support device is proposed, characterized in that it includes correction means for setting the amount smaller when the collision avoidance operation determination means determines the collision avoidance operation by the driver than when not.

  The correction coefficient calculation means M8 of the embodiment corresponds to the correction means of the present invention.

  According to the configuration of claim 1, when the target assist current calculated based on the yaw rate deviation that is the deviation between the standard yaw rate and the actual yaw rate is supplied to the steering actuator to assist the driver's steering operation, collision avoidance by the driver is avoided. When the operation is determined, the avoidance exercise amount necessary for the vehicle to avoid the obstacle is calculated, and the target assist current is corrected based on the avoidance exercise amount. When the absolute value of the yaw rate deviation is equal to or less than the threshold value and the vehicle behavior is stable, the correcting means reduces the target assist current, so that the driver's uncomfortable feeling due to excessive assist can be eliminated. In addition, since the reduction amount of the target assist current is set smaller than when the collision avoidance operation by the driver is determined, it is difficult to reduce the target assist current in an emergency in which the collision avoidance operation is performed, thereby obstructing the obstacle. Can be reliably avoided.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below based on examples of the present invention shown in the accompanying drawings.

  1 to 5 show a first embodiment of the present invention. FIG. 1 is a diagram showing the overall configuration of an automobile equipped with an operation support device, FIG. 2 is a diagram showing the configuration of a steering device, and FIG. 4 is a block diagram of the control system of the support device, FIG. 4 is an explanatory diagram of the target lateral movement distance, and FIG. 5 is a diagram showing a map for searching for the correction coefficient K from the yaw rate deviation Δγ.

  As shown in FIGS. 1 and 2, the four-wheeled vehicle equipped with the operation support device of the present embodiment has left and right front wheels WFL, WFR as drive wheels to which the driving force of the engine E is transmitted via a transmission T. The left and right rear wheels WRL and WRR are driven wheels that rotate as the vehicle travels.

  The rotation of the steering wheel 11 is transmitted to the rack 15 via the steering shaft 12, the connecting shaft 13 and the pinion 14, and the reciprocation of the rack 15 is transmitted to the left and right front wheels WFL, WFR via the left and right tie rods 16, 16. The The power steering device 17 provided in the steering device includes a drive gear 19 provided on the output shaft of the steering actuator 18, a driven gear 20 that meshes with the drive gear 19, a screw shaft 21 that is integrated with the driven gear 20, And a nut 22 engaged with the screw shaft 21 and connected to the rack 15. Therefore, when the steering actuator 18 is driven, the driving force is transmitted to the left and right front wheels WFL, WFR via the drive gear 19, the driven gear 20, the screw shaft 21, the nut 22, the rack 15, and the left and right tie rods 16,16. be able to.

  The electronic control unit U emits electromagnetic waves such as millimeter waves toward the front of the vehicle body, and based on the reflected waves, the relative distance between the obstacle and the vehicle, the relative speed between the obstacle and the vehicle, A radar device Sa that detects the offset distance from the host vehicle and the lateral width of the obstacle, a wheel speed sensor Sb that detects the rotational speeds of the front wheels WFL, WFR and the rear wheels WRL, WRR, and a steering angle δ of the steering wheel 11 A steering angle sensor Sc to be detected and a yaw rate sensor Se to detect the actual yaw rate γ of the vehicle are connected.

  Note that a laser radar can be employed in place of the radar device Sa composed of a millimeter wave radar.

  The electronic control unit U controls the operation of the steering actuator 18 based on the signal from the radar device Sa and the signals from the wheel speed sensor Sb..., The steering angle sensor Sc, and the yaw rate sensor Se.

  As shown in FIG. 3, the electronic control unit U includes a reference yaw rate calculation means M1, a collision avoidance operation determination means M2, an obstacle detection means M3, an avoidance exercise amount calculation means M4, a reference yaw rate correction means M5, a target Assist steering angle calculating means M6, target assist current calculating means M7, correction coefficient calculating means M8, and target current calculating means M9 are provided.

  Next, the normal operation in which the driver does not perform the obstacle avoidance operation will be described.

  The reference yaw rate calculation means M1 calculates a reference yaw rate γt based on the steering angle δ detected by the steering angle sensor Sc and the vehicle speed V calculated from the output of the wheel speed sensor Sb. The target assist steering angle calculation means M6 calculates a target assist steering angle based on the deviation between the actual yaw rate γ detected by the yaw rate sensor Se and the standard yaw rate γt. When the actual yaw rate γ is larger than the reference yaw rate γt, the vehicle is in an oversteer state, and when the actual yaw rate γ is smaller than the reference yaw rate γt, the vehicle is in an understeer state. This corresponds to the steering angle added by the power steering device 17 to the steering angle δ at which the driver actually operates the steering wheel 11 in order to eliminate the steer state and the understeer state. The target assist current calculation unit M7 converts the target assist steering angle calculated by the target assist steering angle calculation unit M6 into a target assist current that is supplied to the steering actuator 18.

  The correction coefficient calculation means M8 performs different corrections when a collision avoidance operation determination means M2 described later does not determine the driver's collision avoidance operation (normal time) and when the driver avoids a collision avoidance operation (when avoidance). The coefficient K is calculated. For both the normal time and the avoidance time, the correction coefficient K is a variable whose parameter is the deviation (yaw rate deviation Δγ) between the actual yaw rate γ and the reference yaw rate γt. The target assist current calculated by the target assist current calculating means M7 is corrected by multiplying it by the correction coefficient K.

  The target current calculation means M9 calculates a target current to be supplied to the steering actuator 18 based on, for example, the steering torque detected by the steering torque sensor and the vehicle speed V of the host vehicle calculated from the output of the wheel speed sensor Sb. Then, the steering actuator 18 is driven based on the current value obtained by adding the target assist current converted by the target assist current calculating means M7 to the target current calculated by the target current calculating means M9. Accordingly, when the vehicle is in an oversteer tendency, the steering wheel 11 is lightened in the cutback direction, and when the vehicle is in an understeer tendency, the steering wheel 11 is made heavy in the cut direction, thereby assisting the driver's steering operation. .

  Next, the operation at the time of avoidance in which the driver performs an obstacle avoidance operation will be described.

  The collision avoidance operation determination means M2 determines whether or not the driver has performed an operation for avoiding the obstacle O based on the steering angle δ of the steering wheel 11 detected by the steering angle sensor Sc. Specifically, the steering angular velocity dδ / dt obtained by time differentiation of the steering angle δ is equal to or higher than a predetermined value (for example, 0.85 rad / sec), or the steering angle δ output from the steering angle sensor Sc is a predetermined value (for example, 0.3 rad). At this time, it is determined that the driver has performed an operation for avoiding the obstacle.

  As shown in FIG. 4, in addition to the relative speed and relative distance between the obstacle O and the own vehicle, the radar device Sa has a lateral width w of the obstacle O and a deviation of the center of the obstacle O from the center line of the own vehicle. That is, the offset distance Do is detected.

The obstacle detection means M3 determines the obstacle O on the predicted course of the host vehicle based on the detection result by the radar device Sa. When the collision avoidance operation determination means M2 determines the avoidance operation by the driver, the avoidance momentum calculation means M4 automatically calculates the avoidance exercise amount calculation means M4 based on the width W of the obstacle O, the known width W of the host vehicle, and the predetermined margin α. The avoidance momentum (target lateral movement distance) Dt necessary for the vehicle to avoid the obstacle O is
Dt = (w / 2) + (W / 2) + α-Do
Calculated by

  It is most difficult to avoid a collision between the own vehicle and the obstacle O when the center of the obstacle O is on the center line of the own vehicle, that is, when the obstacle O is directly in front of the own vehicle. Even in this case, if the vehicle moves in the lateral direction by the target lateral movement distance Dt, it can pass through the obstacle O with a margin corresponding to the margin α.

  The normative yaw rate correcting means M5 corrects the normative yaw rate γt calculated by the normative yaw rate calculating means M1 by the avoiding exercise amount Dt calculated by the avoiding exercise amount calculating means M4. As a result, the standard yaw rate γt calculated from the steering angle δ and the vehicle speed V is corrected so as to increase as it becomes difficult for the vehicle to avoid the obstacle O. Thus, when the driver performs a steering operation for avoiding a collision with the obstacle O, the steering operation can be assisted by the power steering device 17 to effectively avoid the collision.

  At the time of avoidance, the correction coefficient calculation means M8 calculates a correction coefficient K different from the normal time described above, and corrects the target assist current with this correction coefficient K.

  FIG. 5 shows changes in the correction coefficient K using the yaw rate deviation Δγ (= standard yaw rate γt−actual yaw rate γ) as a parameter for both the normal time and the avoidance time. The area where the yaw rate deviation Δγ on the right side of the origin is positive is an understeer area where the standard yaw rate γt is larger than the actual yaw rate γ, and the area where the yaw rate deviation Δγ on the left side of the origin is negative is smaller than the actual yaw rate γ. A small oversteer area.

  Under normal conditions, when the yaw rate deviation Δγ is less than the threshold −Δγ2, the correction coefficient K is maintained at 1. However, when the yaw rate deviation Δγ is greater than or equal to the threshold −Δγ2 and less than the threshold −Δγ1, the correction coefficient K decreases from 1 to 0. When the yaw rate deviation Δγ is greater than or equal to the threshold value −Δγ1, the correction coefficient K is maintained at zero. As described above, when the absolute value of the yaw rate deviation Δγ is equal to or smaller than the threshold value Δγ2, the correction coefficient K is set to less than 1 so that the target assist current supplied to the steering actuator 18 is reduced. By reducing the target assist current supplied to the steering actuator 18 when the tendency is small and the vehicle behavior is stable, it is possible to prevent the driver from feeling uncomfortable due to excessive assist.

  The reason why the correction coefficient K is maintained at 0 in the understeer region where the yaw rate deviation Δγ exceeds the threshold value Δγ1 is as follows. That is, when the yaw rate deviation Δγ is large and the understeer tendency is strong, that is, when the steering actuator 18 generates assist torque when the vehicle approaches the turning limit, the vehicle slips beyond the turning limit, and the tire slips. Vehicle behavior may be disturbed. Therefore, in this case, by controlling the steering actuator 18 so as not to generate assist torque while maintaining the correction coefficient K at 0, disturbance of vehicle behavior can be avoided.

  On the other hand, when avoiding, when the absolute value of the yaw rate deviation Δγ exceeds the threshold value Δγ2, the correction coefficient K is maintained at 1. However, when the absolute value of the yaw rate deviation Δγ is equal to or less than the threshold value Δγ2 and exceeds the threshold value Δγ1, the correction coefficient K is 1. When the absolute value of the yaw rate deviation Δγ is equal to or smaller than the threshold value Δγ1, the correction coefficient K is maintained at the predetermined value (0.7). Even in this avoidance, when the absolute value of the yaw rate deviation Δγ is equal to or less than the threshold value Δγ2 and the vehicle behavior is stable, the correction coefficient K is set to less than 1 to reduce the target assist current supplied to the steering actuator 18. Since the correction is made, it is possible to prevent the driver from feeling uncomfortable due to excessive assist while maintaining ease of avoidance steering.

  When the absolute value of the yaw rate deviation Δγ is equal to or less than the threshold value Δγ1, the correction coefficient K is reduced from 1 to 0 in normal times, whereas the correction coefficient K is reduced only from 1 to a predetermined value (0.7) during avoidance. In other words, at the time of avoidance, control is performed so that the amount of reduction in assist torque generated by the steering actuator 18 is smaller than in normal operation. The reason is to make it easy to turn the steering wheel 11 by generating a sufficient assist torque in an emergency where it is necessary to avoid a collision with the obstacle O.

  6 to 8 show a second embodiment of the present invention. FIG. 6 is a block diagram showing the configuration of the reference yaw rate calculation means, FIG. 7 is a graph showing the lower limit value of the lateral acceleration with respect to the vehicle speed, and FIG. It is a graph which shows the effect | action of a selection means.

  In the first embodiment, the reference yaw rate calculation means M1 calculates the reference yaw rate γt from the steering angle δ and the vehicle speed V. In the second embodiment, the reference yaw rate γt is calculated based on the steering angle δ, the lateral acceleration G, and the vehicle speed V. It differs in the point to calculate.

  As is apparent from FIG. 6, the reference yaw rate calculation means M1 includes steering angle reference yaw rate calculation means m1, phase compensation means m2, lateral acceleration reference yaw rate calculation means m3, phase compensation means m4, and lateral acceleration lower limit regulation means. m5 and low select means m6.

  The steering angle reference yaw rate calculation means m1 calculates the steering angle reference yaw rate by multiplying the steering angle δ detected by the steering angle sensor Sc, a predetermined coefficient, and the vehicle speed V calculated from the output of the wheel speed sensor Sb, The phase deviation of the steering angle reference yaw rate is compensated by the phase compensation means m2. The lateral acceleration standard yaw rate calculation means m3 multiplies the vehicle speed V calculated from the output of the wheel speed sensor Sb and a predetermined coefficient by the lateral acceleration G detected by the lateral acceleration sensor Sf, thereby dividing the lateral acceleration standard yaw rate. , And the phase compensation means m4 compensates for the phase shift of the lateral acceleration standard yaw rate.

  If the lateral acceleration G detected by the lateral acceleration sensor Sf is equal to or lower than the lower limit value set by the lateral acceleration lower limit regulating means m5 shown in FIG. 7, the lateral acceleration G detected by the lateral acceleration sensor Sf is used instead of the lateral acceleration G shown in FIG. The lateral acceleration standard yaw rate is calculated using the lower limit value of the lateral acceleration G shown in FIG. Since the lower limit value of the lateral acceleration G is set so as to increase as the vehicle speed V decreases, the lateral acceleration standard yaw rate calculated at the low vehicle speed is calculated to a value larger than the actual value.

  The steering angle normative yaw rate and lateral acceleration normative yaw rate calculated in this way are input to the low select means m6, and the absolute value of the steering angle normative yaw rate and the lateral acceleration normative yaw rate is small as shown by a thick solid line in FIG. Is selected as the final reference yaw rate γt.

  By the way, on a road surface with a low coefficient of friction where the wheel is likely to slip, the steering angle standard yaw rate tends to be calculated to be larger than the actual yaw rate γ. Therefore, when feedback control is performed using this steering angle standard yaw rate as the standard yaw rate γt. In addition, oversteer suppression may be weakened or delayed on a road surface with a low friction coefficient. Further, since the lateral acceleration normative yaw rate does not accurately reflect the driver's intention to drive (the direction in which the driver wants to travel), if the lateral acceleration normative yaw rate is used as the normative yaw rate γt for feedback control, the driver may feel uncomfortable.

  Therefore, in this embodiment, the steering angle reference yaw rate is basically adopted as the reference yaw rate γt, and when the steering angle reference yaw rate exceeds the lateral acceleration reference yaw rate, the lateral acceleration reference yaw rate is replaced with the steering angle reference yaw rate. Since the standard yaw rate γt is adopted, when the steering angle standard yaw rate is excessively calculated on the road surface with a low friction coefficient while reflecting the driver's driving intention by the steering angle standard yaw rate on the normal road surface, the lateral acceleration standard yaw rate is calculated. Thus, control according to the road surface friction coefficient can be performed to suppress oversteer and understeer early and reliably.

  In a region where the vehicle speed V is low, the detected lateral acceleration G is small, so that the detection error increases, and the error of the lateral acceleration standard yaw rate calculated based on the lateral acceleration G also increases. However, according to the present embodiment, the lateral acceleration standard yaw rate is calculated to be larger than the actual value by the lateral acceleration lower limit regulating means m5 at a low vehicle speed, so that the steering angle standard yaw rate becomes smaller than the lateral acceleration standard yaw rate. As a result, since the steering angle standard yaw rate is selected as the standard yaw rate γt, it is possible to prevent the control with low accuracy based on the lateral acceleration standard yaw rate having low accuracy.

  Although the embodiments of the present invention have been described above, various design changes can be made without departing from the scope of the present invention.

  For example, in the embodiment, the collision with the obstacle O is avoided by the front wheel steering by the power steering device 17, but the yaw moment generated by giving a difference between the braking force of the left wheel and the braking force of the right wheel. It is also possible to avoid collision with the obstacle O.

The figure which shows the whole structure of the motor vehicle carrying the operation support device Diagram showing the configuration of the steering device Block diagram of the control system of the operation support device Illustration of target lateral movement distance The figure which shows the map which searches the correction coefficient K from yaw rate deviation (DELTA) gamma The block diagram which shows the structure of the normative yaw rate calculation means based on 2nd Example. Graph showing the lower limit of lateral acceleration against vehicle speed Graph showing the effect of the low-select means

Explanation of symbols

M1 reference yaw rate calculation means M2 collision avoidance operation determination means M3 obstacle detection means M4 avoidance exercise amount calculation means M5 reference yaw rate correction means M7 target assist current calculation means M8 correction coefficient calculation means (correction means)
O Obstacle γ Actual yaw rate γt Standard yaw rate Δγ Yaw rate deviation 18 Steering actuator

Claims (1)

In a vehicle operation support device that supports a collision avoidance operation performed by a driver to avoid a collision with an obstacle (O) during travel of the vehicle,
A reference yaw rate calculating means (M1) for calculating a reference yaw rate (γt) of the vehicle;
A collision avoidance operation determination means (M2) for determining a collision avoidance operation by the driver;
An obstacle detection means (M3) for detecting an obstacle (O) with which the host vehicle may collide,
When the collision avoidance operation determination means (M2) determines the collision avoidance operation by the driver, the avoidance exercise amount calculation calculates the avoidance exercise amount necessary to avoid the obstacle (O) detected by the obstacle detection means (M3). Means (M4);
A reference yaw rate correcting means (M5) for correcting the reference yaw rate (γt) calculated by the reference yaw rate calculating means (M1) by the avoidance exercise amount calculated by the avoidance exercise amount calculation means (M4);
Target assist current calculation means (M7) for calculating a target assist current to be supplied to the steering actuator (18) based on a yaw rate deviation (Δγ) that is a deviation between the corrected standard yaw rate (γt) and the actual yaw rate (γ);
When the absolute value of the yaw rate deviation (Δγ) is less than or equal to the threshold, the target assist current is reduced, and the reduction amount of the target assist current is determined when the collision avoidance operation determination means (M2) determines the collision avoidance operation by the driver. Correction means (M8) for setting smaller than when not,
A vehicle operation support device comprising:

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