JP2007038696A - Steering supporting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a steering supporting device capable of performing a steering supporting control excellent in follow-up performance of the traveling of a vehicle at the time of traveling on a curve of a traveling road. <P>SOLUTION: The steering supporting device 1 imparts steering torque to a steering mechanism so that the vehicle may travel along the traveling road based on images that the traveling road in front of the vehicle is imaged. When a curve exit on the traveling road is detected and the vehicle travels at the curve exit, change amount of the steering torque is increased when returning a steering wheel 2 as compared with cases except the curve exit time. As a result, delay of returning of the steering wheel 2 at the curve exit can be suppressed, and the vehicle can be traveled by following up the traveling road. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a steering assistance device that provides steering assistance by applying a steering torque to a steering mechanism of a vehicle.

2. Description of the Related Art Conventionally, as a steering assistance device that provides steering assistance by applying a steering torque to a vehicle steering mechanism, as described in Japanese Patent Laid-Open No. 2001-10518, the front of the vehicle is imaged by a camera, and the captured image information Based on the travel path and the position of the vehicle relative to the travel path, calculating the basic steering assist torque based on the shape of the travel path, calculating the corrected steering assist torque based on the position of the vehicle, An output steering assist torque is calculated based on the corrected steering assist torque, and an operation amount of the steering actuator is determined based on the output steering assist torque. This device is intended to improve control accuracy by performing steering control using a shape parameter of a traveling road and a vehicle position parameter with high detection accuracy without using a yaw rate.
JP 2001-10518 A

  However, in such a steering assist device, when the vehicle travels on a curve and approaches the exit of the curve, a delay in turning back the steering wheel may occur. In this case, due to the delay in turning back the steering wheel, the vehicle does not follow the travel path, and the driver of the vehicle feels uncomfortable.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a steering assist device capable of performing steering assist control with excellent followability to a traveling road.

  That is, the steering assist device according to the present invention is a steering assist device that applies a steering torque to a steering mechanism so that the vehicle travels along a travel path based on an image obtained by imaging a travel path ahead of the vehicle. A detecting means for detecting a curve exit on the road, and a steering control means for increasing the amount of change in the steering torque when the detecting means detects a curve exit compared to a case other than when the curve exit. Yes.

  In the steering assist device according to the present invention, the steering control means increases the amount of change in the steering torque when the steering wheel is turned back when the detection means detects the curve exit, compared to the case other than when the curve exit. It is preferable.

  According to these inventions, when the curve exit is detected, the amount of change in the steering torque is increased, so that the steering amount for turning back the steering wheel at the curve exit can be increased. Thereby, the delay of the steering wheel turning back at the curve exit can be suppressed. For this reason, the vehicle travels following the traveling road, and steering assist control excellent in followability to the traveling road becomes possible.

  ADVANTAGE OF THE INVENTION According to this invention, a vehicle can be made to drive | work along a driving path in a curve exit, and the steering assistance control excellent in the followability to a driving path can be performed.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 1 is a schematic configuration diagram of a steering assist device according to an embodiment of the present invention.

  As shown in FIG. 1, a steering assist device 1 according to the present embodiment is a device that provides steering torque to a steering force transmission system of a vehicle to assist the driver of the vehicle. Used for lane keeping control that maintains the position of the vehicle at the center position. The vehicle steering force transmission system includes a steering shaft 3, a gear portion 4, and a tie rod 6 as main components. The steering shaft 3 is connected to the handle 2 and transmits the steering force of the handle 2 to the gear portion 4 and the tie rod 6.

  The gear unit 4 converts the steering torque transmitted from the steering shaft 3 into a horizontal force. As the gear part 4, a rack and pinion type, for example, is used. The gear unit 4 receives the assist force of the assist motor 5 and moves the tie rod 6 to steer the steered wheels 7.

  The gear unit 4 is provided with a torque sensor 8. The torque sensor 8 functions as a steering torque detection means for detecting the steering torque of the handle 2. As this torque sensor 8, for example, a torsion bar (not shown) is arranged between the steering shaft 3 and a pinion shaft (not shown), and the torsion bar is twisted according to the steering torque by two rotation sensors (not shown). What is detected by is used.

  The motor 5 is a motor that assists the steering force of the handle 2 and applies an assist force according to, for example, a steering torque to the steering force transmission system. In FIG. 1, the motor 5 is of a rack assist type that gives an assist force to the rack, but may be of a column assist type or the like.

  The steering assist device 1 is provided with an ECU (Electronic Control Unit) 20. The ECU 20 performs control processing for the entire apparatus, and includes, for example, a CPU, a ROM, a RAM, an input signal circuit, an output signal circuit, a power supply circuit, and the like. The steering assist device 1 is provided with a camera 11. The camera 11 functions as an imaging unit that images the front of the vehicle. For example, a CCD camera or the like is used. Image information captured by the camera 11 is input to the ECU 20.

  The ECU 20 functions as a vehicle position detection unit that detects the position of the vehicle with respect to the width direction of the travel path based on the image information. For example, the ECU 20 performs image processing on the captured image, recognizes a white line included in the image information, and detects the position of the vehicle with respect to the width direction of the traveling road based on the recognized shape and position of the white line. At that time, the positional deviation of the vehicle from the center position of the lane is referred to as an offset.

  Further, the ECU 20 functions as a curve detection unit that detects the curvature of the traveling road from a white line or the like and detects a curve based on the curvature. The curve of the traveling road means that the traveling road is bent with a curvature of a predetermined value or more, and includes a corner of the traveling road.

  The ECU 20 also functions as a curve exit detection unit that detects a curve exit based on a change in the curvature of the travel path. Further, the ECU 20 functions as a steering control unit that increases the amount of change in the steering torque when the vehicle is traveling on the curve exit of the travel path as compared to a case other than when traveling on the curve exit.

  The steering assist device 1 is provided with a vehicle speed sensor 12. The vehicle speed sensor 12 functions as a vehicle speed detection unit that detects the traveling speed of the vehicle.

  FIG. 2 is a schematic diagram of a basic control block of the steering assist control in the steering assist device 1 according to the present embodiment.

  As shown in FIG. 2, in the steering assist device 1, image information of the traveling road ahead of the vehicle imaged by the camera 11 is input to the ECU 20, and the curvature (R) of the traveling road, the vehicle position ( D) and the vehicle orientation (θ) relative to the white line are detected. The curvature of the traveling road is calculated based on, for example, the detection state of the white line on the traveling road. The vehicle position is a position with respect to the width direction of the travel path of the vehicle. This vehicle position is calculated based on, for example, a white line detection state. The direction of the vehicle with respect to the white line is calculated based on the detection state of the left and right white lines, for example.

  The curvature of the travel path, the vehicle position, and the vehicle direction are each multiplied by a predetermined gain (G) and then used for calculating the target lateral acceleration. The target lateral acceleration is a lateral acceleration necessary for returning the vehicle to the center of the lane. Then, by multiplying the target lateral acceleration by a predetermined coefficient, a steering torque (assist steering force) necessary for maintaining the lane is calculated. This steering torque is applied to the steering mechanism.

  On the other hand, an actuator (motor 5) of an electric power steering (EPS) applies an assist force in accordance with the steering force of the driver of the vehicle. A steering wheel steering force and an assisting force are applied to the steering mechanism from the actuator of the electric power steering.

  The steering mechanism is provided with steering force, steering assist force, and assist steering force for maintaining the lane as steering force. In response to the steering force, the traveling direction of the vehicle changes.

  FIG. 3 is a flowchart showing a curve determination process in the steering assist device 1 according to the present embodiment.

  This curve determination process is a process of determining whether or not the travel path (road) on which the vehicle travels is a curve. A series of control processes in FIG. 3 are repeatedly executed by the ECU 20 at a predetermined cycle, for example.

  First, as shown in S10 of FIG. 3, a road curvature calculation process is performed. This curvature calculation process is a process for calculating the curvature of the traveling road based on the image captured by the camera 2. For example, a white line on the road is extracted from the captured image, the curvature of the white line is calculated, and the curvature of the road is calculated based on the curvature of the white line. The curvature of the travel path is calculated, for example, assuming that the rightward curvature is positive and the leftward curvature is negative.

  Then, the process proceeds to S12, in which it is determined whether or not the previous value of the curve turning flag is OFF and the absolute value of the road curvature is greater than the first curvature value C1. The curve turning flag is a flag indicating whether or not the vehicle is turning. When the curve turning flag is on, it indicates that the vehicle is turning, and when the curve turning flag is off, it indicates that the vehicle is not turning. The first curvature value C1 is a set value set in advance in the ECU 20.

  If the previous value of the curve turning flag is OFF in S12 and the absolute value of the road curvature is greater than the first curvature value C1, the curve determination establishment timer is incremented (S14). On the other hand, if the previous value of the curve turning flag is not OFF or the absolute value of the road curvature is not greater than the first curvature value C1, the curve determination establishment timer is reset (S16).

  Then, the process proceeds to S18, where it is determined whether or not the previous value of the curve turning flag is ON and the absolute value of the road curvature is smaller than the second curvature value C2. The second curvature value C2 is a set value set in advance in the ECU 20. If the previous value of the curve turning flag is ON in S18 and the absolute value of the road curvature is smaller than the second curvature value C2, the curve determination cancellation timer is incremented (S20). On the other hand, if the previous value of the curve turning flag is not on or the absolute value of the road curvature is not smaller than the second curvature value C2, the curve determination cancellation timer is reset (S22).

  Then, the process proceeds to S24, where it is determined whether or not the previous value of the curve turning flag is OFF. If the previous value of the curve turning flag is OFF, it is determined whether or not the curve determination establishment timer has exceeded the first time T1 (S26). If the curve determination establishment timer exceeds the first time T1, the curve turning flag is set to ON (S28). On the other hand, if the curve determination establishment timer does not exceed the first time T1, the process proceeds to S32.

  By the way, if the previous value of the curve turning flag is not OFF in S24, it is determined whether or not the curve determination cancellation timer exceeds the second time T2 (S30). If the curve determination cancellation timer exceeds the second time T2, the process proceeds to S32.

  In S32, the curve turning flag is set to OFF. In S30, when the curve determination cancellation timer does not exceed the second time T2, the process proceeds to S28, and the curve turning flag is set to ON.

  Then, the process proceeds to S34, where the curve turning flag data is set as the previous value of the curve turning flag. Then, a series of processes of the curve determination process is finished.

  According to this curve determination processing, when the absolute value of the road curvature exceeds the first curvature value C1 exceeds the first time T1, the curve turning flag is turned on, and the travel path on which the vehicle travels is a curve. It can be detected. Note that, in the steering assist device 1 according to the present embodiment, such a curve determination process is an example of a method for detecting a curve of a traveling road, and curve determination may be performed using other methods.

  FIG. 4 is a flowchart showing a curve exit determination process in the steering assist device 1 according to the present embodiment.

  This curve exit determination process is a process of determining whether or not the travel path (road) on which the vehicle travels is a curve exit. A series of control processes in FIG. 4 are repeatedly executed by the ECU 20 at a predetermined cycle, for example.

  First, as shown in S40 of FIG. 4, it is determined whether or not the previous value of the curve turning flag is on. If the previous value of the curve turning flag is not on, zero is set to the maximum curvature value Cmax during curve traveling (S42). The maximum curvature value Cmax is a value indicating the maximum curvature of the traveling path during the curve traveling of the vehicle, and is updated at any time during the curve traveling. Then, the curve exit determination release timer is reset (S44), the curve exit determination establishment timer is reset (S46), and the curve exit flag is set to OFF (S48). Then, the curve exit determination process ends.

On the other hand, if the previous value of the curve turning flag is on in S40, it is determined whether or not the absolute value of the road curvature is larger than the maximum curvature value Cmax during curve traveling (S50). If the absolute value of the road curvature is not larger than the maximum curvature value Cmax during curve traveling, the process proceeds to S54.
On the other hand, if the absolute value of the road curvature is larger than the maximum curvature value Cmax during curve traveling, the absolute value of the road curvature is set as the maximum curvature value Cmax (S52).

  Then, the process proceeds to S54, where it is determined whether or not the previous value of the curve exit flag is OFF. If the previous value of the curve exit flag is OFF, the curve exit determination release timer is reset (S56). Then, it is determined whether or not the absolute value of the road curvature is smaller than a value obtained by multiplying the maximum curvature value Cmax by the curve exit determination coefficient Kr (S58). The curve determination coefficient Kr is a coefficient set in advance in the ECU 20, and is set based on a state in which the road is regarded as a straight line.

  If the absolute value of the road curvature is not smaller than the value obtained by multiplying the maximum curvature value Cmax by the curve exit determination coefficient Kr in S58, the curve exit determination establishment timer is reset (S62). Then, the process proceeds to S64. On the other hand, if the absolute value of the road curvature is smaller than the value obtained by multiplying the maximum curvature value Cmax by the curve exit determination coefficient Kr in S58, the curve exit determination establishment timer is incremented (S60). Then, the process proceeds to S64.

  In S64, it is determined whether or not the curve exit determination establishment timer has exceeded the third time T3. The third time T3 is a preset time set in the ECU 20 in advance. When the curve exit determination establishment timer exceeds the third time T3, the curve exit flag is set to ON (S66). The curve exit flag is a flag indicating that the travel path on which the vehicle travels is a curve exit. When the curve exit flag is on, the travel path is a curve exit, and when the curve exit flag is off, the travel path is not a curve exit. On the other hand, if the curve exit determination establishment timer does not exceed the third time T3 in S64, the process proceeds to S78, and the curve exit flag is set to OFF (S78).

  By the way, when the previous value of the curve exit flag is not OFF in S54, the curve exit determination establishment timer is reset (S68). Then, it is determined whether or not the absolute value of the road curvature is larger than a value obtained by multiplying the maximum curvature value Cmax by the curve exit determination coefficient Kr (S70). If the absolute value of the road curvature is not larger than the value obtained by multiplying the maximum curvature value Cmax by the curve exit determination coefficient Kr, the curve exit determination cancellation timer is reset (S72). Then, the process proceeds to S76. On the other hand, if the absolute value of the road curvature is larger than the value obtained by multiplying the maximum curvature value Cmax by the curve exit determination coefficient Kr in S70, the curve exit determination cancellation timer is incremented (S74). Then, the process proceeds to S76.

  In S76, it is determined whether or not the curve exit determination cancellation timer has exceeded the fourth time T4. The fourth time T4 is a set time set in the ECU 20 in advance. If the curve exit determination cancellation timer does not exceed the fourth time T4, the process proceeds to S66, and the curve exit flag is set to ON. On the other hand, when the curve exit determination cancellation timer exceeds the fourth time T4 in S76, the process proceeds to S78, and the curve exit flag is set to OFF (S78).

  Then, the process proceeds to S80, where the curve exit flag data is set to the previous value of the curve exit flag, and the series of curve exit determination processing ends.

  According to such a curve exit determination process, the curve exit flag is turned on when the road curvature of the travel path on which the vehicle travels decreases from the maximum curvature value Cmax to a predetermined value or more, and the travel path of the vehicle is the curve exit. Can be detected. Note that, in the steering assist device 1 according to the present embodiment, such a curve exit determination process is an example of a technique for detecting a curve exit on a traveling road, and even if a curve exit is detected using other techniques. Good.

  5 and 6 are flowcharts of the steering assist control process in the steering assist device according to the present embodiment. A series of control processes of the steering assist control process is repeatedly executed by the ECU 20 at a predetermined cycle, for example.

  First, as shown in S90 of FIG. 5, the target lateral acceleration (target G) is calculated. The target lateral acceleration is a lateral acceleration necessary for moving the traveling position of the vehicle to the center of the lane, and is calculated based on the offset of the vehicle (the amount of positional deviation of the vehicle with respect to the center position of the lane). Then, the process proceeds to S92, and filter processing is performed. The filter process is a process performed to remove noise from the target lateral acceleration value.

  Then, the process proceeds to S94, where it is determined whether or not the target lateral acceleration is smaller than a value obtained by subtracting the lateral acceleration value ΔG from the target lateral acceleration threshold value. The target lateral acceleration threshold value is a variable set in the ECU 20. The lateral acceleration value ΔG is a set value set in the ECU 20 in advance. If it is determined that the target lateral acceleration is smaller than the value obtained by subtracting the lateral acceleration value ΔG from the target lateral acceleration threshold value, the left direction is set in the temporary steering direction flag (S96). On the other hand, if the target lateral acceleration is not smaller than the value obtained by subtracting the lateral acceleration value ΔG from the target lateral acceleration threshold value, is the target lateral acceleration greater than the value obtained by adding the lateral acceleration value ΔG to the target lateral acceleration threshold value? It is determined whether or not (S100).

  If it is determined in S100 that the target lateral acceleration is not larger than the value obtained by adding the lateral acceleration value ΔG to the target lateral acceleration threshold value, the process proceeds to S104. On the other hand, if it is determined that the target lateral acceleration is greater than the value obtained by adding the lateral acceleration value ΔG to the target lateral acceleration threshold value, the right direction is set to the temporary steering direction flag (S102). Then, the process proceeds to S98, where the target lateral acceleration is set as the target lateral acceleration threshold value. Then, the process proceeds to S104.

  In S104, it is determined whether or not the temporary steering direction flag and the curve direction of the vehicle do not match and the curve exit flag is set to ON. If the temporary steering direction flag does not match the curve direction of the vehicle and the curve exit flag is set to ON, it is determined that the steering wheel is being turned back at the curve exit. In this case, the intermediate value cancellation flag is set to ON (S106). The intermediate value cancellation flag is a flag indicating whether or not to cancel the setting of the intermediate value to the steering torque calculated based on the target lateral acceleration. The intermediate value is a value set in the middle of the steering torque at the time of increasing the cutting and the steering torque at the time of switching back (see FIG. 7).

  On the other hand, if the temporary steering direction flag matches the curve direction of the vehicle, or if the curve exit flag is not set to ON, it is determined that the steering wheel is not turned back at the curve exit. In this case, the intermediate value cancellation flag is set to OFF (S108). Then, the process proceeds to S110 to determine whether or not the previous value of the steering direction flag is an intermediate value.

  If the previous value of the steering direction flag is an intermediate value in S110, the intermediate line timer is incremented (S112). On the other hand, if the previous value of the steering direction flag is not the intermediate value, the intermediate line timer is reset (S114). The intermediate line timer is a timer that measures the time for which the steering torque is set to an intermediate value. When the intermediate line timer becomes overtime, the setting value of the steering torque is changed from the intermediate value to another value.

  The process proceeds to S116, and it is determined whether or not the intermediate value cancellation flag is set to ON. If the intermediate value cancel flag is not set to ON, the process proceeds to S120 in FIG. On the other hand, when the intermediate value cancel flag is set to ON, ΔT is set to the intermediate line timer (S118). ΔT is a timer completion time for causing the intermediate line timer to overtime. By setting ΔT in the intermediate line timer, the intermediate line timer becomes overtime.

  Then, the process proceeds to S120 of FIG. 6 to determine whether or not the temporary steering direction flag does not match the previous value of the temporary steering direction flag and the intermediate value cancellation flag is off. If the temporary steering direction flag does not match the previous value of the temporary steering direction flag and the intermediate value cancellation flag is OFF, it is determined that the steering direction has changed, and the steering direction change flag is set to ON. (S122). On the other hand, if the temporary steering direction flag matches the previous value of the temporary steering direction flag, or if the intermediate value cancellation flag is not OFF, the steering direction change flag is set to OFF (S124).

  Then, the process proceeds to S126, and it is determined whether or not the steering direction change flag is turned on. If the steering direction change flag is on, an intermediate value is set in the steering direction flag (S128). If the steering direction change flag is not on, it is determined whether the previous value of the steering direction flag is not an intermediate value or the intermediate line timer is equal to or greater than ΔT (S130).

  In S130, when the previous value of the steering direction flag is not the intermediate value or the intermediate line timer is equal to or greater than ΔT, the temporary steering direction flag data is set in the steering direction flag (S132). If the previous value of the steering direction flag is an intermediate value and the intermediate line timer is not greater than ΔT, the previous value of the steering direction flag is set in the steering direction flag (S134).

  Then, the process proceeds to S136, and a steering torque calculation process is performed. The steering torque calculation process is a process for calculating a steering torque necessary for steering assistance. For example, as shown in FIG. 7, the steering torque (EPS required torque) is calculated based on the target lateral acceleration.

  In FIG. 7, the steering torque corresponding to the target lateral acceleration (target G) is set. However, the steering torque is set to a different value when the steering wheel is increased and when the steering wheel is turned back. When the cutting is increased, the absolute value of the steering torque is set to be larger than that at the time of switching back, and a hysteresis width (his width) is provided. In the characteristic of the target lateral acceleration-steering torque in FIG. 7, an intermediate line (dashed line) is set between the additional line (thick solid line) and the return line (thin solid line).

  When the steering wheel is turned up after turning it back, the steering torque is calculated using the turning back line, but when it is not traveling at the exit of the curve, the steering torque from the added line to the intermediate line is used for a predetermined time. After (ΔT), the steering torque is changed from the intermediate line to the return line (A in FIG. 7).

  On the other hand, when the vehicle is traveling at the curve exit, the intermediate line is skipped from the additional line and the steering torque of the return line is set (B in FIG. 7). As a result, as shown in FIG. 8, the amount of change in the steering torque for switching back when traveling on a curve exit can be increased.

  Then, the process proceeds to S138 in FIG. 6, and the driving process of the motor 5 is performed. The driving process of the motor 5 is a process of driving and controlling the motor 5 so that the steering torque set in S136 is applied to the steering mechanism. By driving the motor 5, a steering torque for steering assistance is applied to the steering mechanism of the vehicle.

  As described above, according to the steering assist device 1 according to the present embodiment, it is possible to increase the steering amount of the steering wheel return at the curve exit by increasing the amount of change in the steering torque when the curve exit is detected. it can. Thereby, it is possible to suppress a delay in turning back the handle at the curve exit. For this reason, the vehicle travels following the traveling road, and steering assist control excellent in followability to the traveling road becomes possible.

  For example, as shown in FIG. 9, the vehicle 60 is prevented from moving out of the lane center position by increasing the amount of turning back of the handle of the vehicle 60 near the curve exit 71 of the travel path 70. Therefore, the followability at the curve exit of the traveling path of the vehicle 60 can be improved. In addition, it is possible to prevent the driver of the vehicle 60 from feeling uncomfortable.

  Each embodiment mentioned above shows an example of the steering assistance device concerning the present invention. The steering assist device according to the present invention is not limited to the above, and the steering assist device according to the embodiment is modified or applied to others so as not to change the gist described in each claim. It may be a thing. For example, in this embodiment, the case where the present invention is applied to a device that assists the steering of a driver who performs steering of the vehicle has been described. However, the present invention may be applied to a device that performs automatic steering.

1 is a schematic configuration diagram of a steering assist device according to an embodiment of the present invention. It is a block schematic diagram of the steering assistance control in the steering assistance apparatus of FIG. It is a flowchart which shows the curve determination process in the steering assistance apparatus of FIG. It is a flowchart which shows the curve exit determination process in the steering assistance apparatus of FIG. It is a flowchart which shows the steering assistance control process in the steering assistance apparatus of FIG. It is a flowchart which shows the steering assistance control process in the steering assistance apparatus of FIG. It is explanatory drawing of the target lateral acceleration-steering torque characteristic in the steering assistance control process of the steering assistance apparatus of FIG. It is explanatory drawing of the steering torque output in the steering assistance control process of the steering assistance apparatus of FIG. It is explanatory drawing of the vehicle travel in the steering assistance control of the steering assistance apparatus of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Steering assistance apparatus, 2 ... Steering wheel, 11 ... Camera (imaging means), 12 ... Vehicle speed sensor, 20 ... ECU.

Claims (2)

In a steering assist device that applies a steering torque to a steering mechanism so that the vehicle travels along a travel path based on an image of a travel path ahead of the vehicle,
Detecting means for detecting a curve exit in the travel path;
Steering control means for increasing the amount of change in the steering torque when the detection means detects a curve exit, compared to a case other than when the curve exit
A steering assist device comprising: The steering control means increases the amount of change in steering torque when the steering wheel is turned back when the detection means detects a curve exit, compared to a case other than when the curve exit.
The steering assist device according to claim 1, wherein:

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