JP4591250B2 - Steering support device - Google Patents

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 assist device that performs steering assist by applying a steering torque to a steering mechanism of a vehicle, as described in JP-A-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 intends to improve control accuracy by performing steering control using a shape parameter 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 position of the vehicle relative to the travel path cannot be accurately detected based on the image information, the appropriate steering assist is determined when the steering torque is determined based on the position of the vehicle. Will not be possible.

  Therefore, an object of the present invention is to provide a steering assist device that can prevent inappropriate steering assist control even when the position of the vehicle with respect to the travel path cannot be accurately detected.

  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. Vehicle position detection means for detecting the position of the vehicle with respect to the width direction of the road, change rate setting means for setting the maximum position change rate of the vehicle based on the vehicle speed of the vehicle, and detected by the vehicle position detection means When the vehicle position exceeds the maximum vehicle position change amount according to the maximum position change rate, the correction unit corrects the vehicle position so as not to exceed the maximum vehicle position change amount, and the vehicle position detection unit When the vehicle position detected by the vehicle position exceeds the maximum vehicle position change amount corresponding to the maximum position change rate, the steering torque is set using the vehicle position corrected by the correction means. Is constituted by a steering torque setting means for.

  According to this invention, when the vehicle position detected by the vehicle position detection means is not appropriate, the correction means corrects the vehicle position so as not to exceed the maximum change in vehicle position. For this reason, when the vehicle position is erroneously detected, setting of the steering torque based on the vehicle position can be avoided, and inappropriate steering support control can be prevented.

  In the steering assist device according to the present invention, it is preferable that the change rate setting means sets the maximum position change rate to be larger as the vehicle speed is higher.

  According to the present invention, inappropriate steering support control can be prevented even when the position of the vehicle with respect to the travel path cannot be accurately detected.

  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. In addition, 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 change rate setting means for setting the maximum position change rate of the vehicle based on the vehicle speed. In addition, when the detected position of the vehicle exceeds the maximum change amount of the vehicle position according to the maximum change rate of the vehicle, the ECU 20 serves as a correction unit that corrects the vehicle position so as not to exceed the maximum change amount of the vehicle position. Function. Further, the ECU 20 functions as a steering torque setting unit that sets the steering torque using the corrected vehicle position when the detected vehicle position exceeds the maximum vehicle position change amount.

  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 based on the image information, 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, for example, the detection state of the left and right white lines.

  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 an offset (vehicle position) calculation process of the steering assist device 1 according to the present embodiment.

  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, the offset maximum change rate is set. The offset means a position with respect to the width direction of the travel path of the vehicle. The maximum offset change rate is the maximum value (limit value) of the offset change amount during a predetermined time, and is set to a larger value as the vehicle speed increases. This maximum offset change rate is set by multiplying the vehicle speed by the maximum yaw angle of the vehicle. The maximum yaw angle is a preset yaw angle. As the maximum yaw angle, for example, a control limit yaw angle at which lane keeping control is prohibited is used.

  Then, the process proceeds to S12, and an offset change amount calculation process is performed. The offset change amount is a change amount of the current offset value with respect to the previous offset value in the repeatedly performed offset calculation process. The calculation process of the offset change amount is performed by subtracting the correction offset previous value from the current offset value.

  Then, the process proceeds to S14, where it is determined whether or not the absolute value of the offset change amount is larger than the maximum offset change amount. The offset change to the left side of the vehicle is positive, the offset change to the right side of the vehicle is negative, and it is determined whether the absolute value of the offset change amount is larger than the maximum offset change amount. The offset maximum change amount is a value calculated based on the offset maximum change rate calculated in S12, and is calculated by, for example, multiplying the offset maximum change rate by the cycle of the lane keeping control.

  When it is determined in S14 that the absolute value of the offset change amount is not larger than the maximum offset change amount, the current offset value is set as the correction offset value (S16). In this case, the offset change amount is not larger than the maximum offset change amount, and it is determined that the current offset value is not an inappropriate value, and the offset value is used as it is as a correction offset.

  On the other hand, if it is determined in S14 that the absolute value of the offset change amount is greater than the maximum offset change amount, it is determined whether the offset change amount is greater than zero (S18). When it is determined that the offset change amount is greater than zero, a value obtained by adding the maximum offset change amount calculated in S12 to the correction offset previous value is set as the correction offset (S20).

  On the other hand, when it is determined that the offset change amount is not larger than zero, a value obtained by subtracting the offset maximum change amount calculated in S12 from the correction offset previous value is set as the correction offset (S22). By the processes of S20 and S22, even when the offset is erroneously detected due to erroneous recognition of the image and the offset is largely changed, the offset is suppressed to a constant change or less. Then, the process proceeds to S24, and the correction offset is set as the correction offset previous value. Then, the control process ends.

  The correction offset calculated by the offset calculation process is used as the vehicle position D for determining the assist steering force for maintaining the lane (see FIG. 2).

  As described above, according to the steering assist device 1 according to the present embodiment, when the vehicle offset (vehicle position) detected based on the image of the camera 11 is not appropriate, the maximum offset change amount is not exceeded. The correction offset is corrected. For this reason, when a vehicle offset is erroneously detected due to erroneous recognition of a white line in the image, it is possible to avoid setting the steering torque based on the offset, and to prevent inappropriate steering support control. This is particularly effective when there are white lines that are forgotten to be erased.

  For example, as shown in FIG. 4, when an offset is skipped due to misrecognition of an image and the change amount of the offset exceeds the maximum offset change amount, the correction offset is set not to exceed the maximum offset change amount. (See the solid line in FIG. 4. The broken line is the prior art.) Thereby, the amount of change in the offset can be suppressed within a predetermined range.

  For this reason, as shown in FIG. 5, even if the steering output torque calculated using the correction offset fluctuates due to erroneous recognition of the white line in the image, the amount of change is suppressed to a low level (solid line in FIG. 5). See the dashed line for the prior art.)

  Accordingly, as shown in FIG. 6, the vehicle travel position is stable with respect to the travel path 50, the position close to the center of the lane can be maintained, and the followability at the travel position can be improved (see the solid line in FIG. 6). (The dashed line is the prior art.)

  In the steering assist device according to the present embodiment, it is preferable that the maximum position change rate is set larger as the vehicle speed increases. Thereby, an appropriate filter can be set for each vehicle speed, and delay due to the filter can be prevented while ensuring noise removal performance.

  In addition, embodiment mentioned above shows an example of the steering assistance apparatus which concerns on this 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 offset calculation process in the steering assistance apparatus of FIG. It is explanatory drawing of the offset correction in the steering assistance apparatus of FIG. It is explanatory drawing of the steering output torque in the steering assistance apparatus of FIG. It is explanatory drawing of the lane keeping control in 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,
Vehicle position detecting means for detecting the position of the vehicle with respect to the width direction of the travel path;
Change rate setting means for setting the maximum position change rate of the vehicle based on the vehicle speed of the vehicle;
When the vehicle position detected by the vehicle position detection means exceeds the maximum vehicle position change amount corresponding to the maximum position change rate, the vehicle position is corrected so as not to exceed the vehicle position maximum change amount. Correction means;
Steering torque for setting the steering torque using the vehicle position corrected by the correcting means when the vehicle position detected by the vehicle position detecting means exceeds the maximum vehicle position change amount corresponding to the maximum position change rate. Setting means;
A steering assist device comprising: The steering assist device according to claim 1, wherein the change rate setting means sets the maximum position change rate to a greater value as the vehicle speed increases.

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