JP2015150963A - Steering control device for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform the automatic control of a steering operation angle which scarcely imparts incongruity to a driver even in an S-curve region.SOLUTION: In the case that a road width center line curvature radius Ra which is sequentially calculated at a radius curvature calculation part 106 on the basis of a current position of an own vehicle which is sequentially specified at a current position specifying part 101, and a road contour which is decided at a road contour deciding part 103 is increased, a prescribed upper limit is set at an increase rate of the road width center line radius curvature Ra which is used for calculating a curve turn required tire operation angle θ_curv, thus a frequent change of a steering direction at a steering indication part is suppressed, and the automatic control of a steering operation angle which scarcely imparts incongruity to a driver even in an S-curve region becomes possible.

Description

  The present invention relates to a vehicle steering control device that automatically controls a steering angle.

  2. Description of the Related Art Conventionally, a technique for automatically controlling a steering angle of a vehicle is known. For example, in Patent Literature 1, a steering angle target value is determined along a target route obtained through image processing, and feedback control is performed so that a difference between the steering angle target value and the detected value decreases. Is disclosed.

JP-A-9-128699

  However, in the technique disclosed in Patent Document 1, in a region where the target route is a straight line or a region where the curve direction of the target route is constant, feedback control is favorably performed so that the difference between the target value and the detected value decreases. However, in the S-curve region where the curve direction changes, there is a problem that the steering direction changes frequently and the driver feels uncomfortable. Details are as follows.

  In the S-curve region, the steering is near the neutral position on a short straight road connecting curves in opposite directions. If the feedback control is simply performed so that the difference between the target value and the detected value of the rudder angle is reduced on this straight road, the steering angle that was turned too far to the right is returned too far to the left or too far to the left. Repeatedly turning the steering angle too far to the right. As a result, the steering direction changes frequently, giving the driver a feeling of strangeness.

  SUMMARY OF THE INVENTION The present invention has been made in view of the above-described conventional problems, and an object of the present invention is to provide a vehicle steering control that enables automatic control of a steering angle with little discomfort to the driver even in an S-curve region. To provide an apparatus.

  A vehicle steering control device according to the present invention is mounted on a vehicle and sequentially determines a current position of the host vehicle, and a road outer shape determination that determines a road outer shape that is an outer shape of a road area on which the host vehicle is to travel. Radius of curvature that sequentially calculates the radius of curvature Ra for the road profile in front of the vehicle based on the current position of the vehicle and the road profile determined by the road profile determination unit Using the calculation unit (S3) and the curvature radius Ra calculated by the curvature radius calculation unit, a turning angle calculation unit (S13) that calculates a curve turning required tire turning angle θ_curv for steering the vehicle according to the curvature radius Ra. ), A target turning angle calculation unit (S31) that calculates a steering turning angle Θ corresponding to the curve turning required tire turning angle θ_curv calculated by the turning angle calculation unit, and a steering turning angle Θ calculated by the target turning angle calculation unit The vehicle steering control device (10) includes a steering instruction unit (S32) that controls the steering angle as a target, and the curvature radius Ra sequentially calculated by the curvature radius calculation unit increases. The turning angle calculation unit includes a limiting unit (109) that sets a predetermined upper limit on the increasing rate of the curvature radius Ra used for calculating the turning angle of the tire required to turn a curve.

  According to this, the steering instruction unit controls the steering angle with the steering turning angle Θ corresponding to the curve turning required tire turning angle θ_curv for steering according to the curvature radius Ra of the road profile in front of the host vehicle as a target. Therefore, the steering angle can be automatically controlled according to the curvature radius Ra of the road profile in front of the host vehicle.

  In the S-curve area, there is an area where the radius of curvature R changes greatly between the short straight road connecting the curves in opposite directions and the curved road before and after the straight road. There are situations where the road profile in front of the vehicle is a straight road, a right curve road, or a left curve road. In such a situation, the curvature radius Ra of the road contour in front of the host vehicle calculated by the curvature radius calculation section repeats abrupt increase and decrease, so that the curve turns corresponding to the curvature radius Ra calculated by the curvature radius calculation section as it is. If the required tire turning angle θ_curv is calculated by the turning angle calculation unit, the steering direction is frequently changed by the steering instruction unit.

  On the other hand, according to the present invention, since the limiting unit provides a predetermined upper limit to the increase rate of the radius of curvature Ra used to calculate the curve turning required tire turning angle, the behavior of the vehicle in the S-curve region is Even if it fluctuates, it becomes possible to suppress a rapid change in the turning angle of the tire required to turn the curve due to a rapid increase in the curvature radius Ra. As a result, it is possible to prevent the steering instruction unit from frequently changing the steering direction, and to automatically control the steering angle with less discomfort to the driver even in the S-curve region.

1 is a block diagram showing a schematic configuration of a driving support system 100. FIG. It is a schematic diagram which shows an example of the detection range of the ranging sensor. 2 is a functional block diagram showing an example of a schematic configuration of a vehicle control ECU 10. FIG. It is a flowchart which shows an example of the flow of the 1st request angle calculation related process in vehicle control ECU10. It is a mimetic diagram for explaining the 1st demand angle calculation related processing. It is a schematic diagram for demonstrating the process of S4. It is a flowchart which shows an example of the flow of the 2nd request angle calculation related process in vehicle control ECU10. It is a flowchart which shows an example of the flow of the behavior control related process in vehicle control ECU10. It is a schematic diagram for demonstrating the problem of a prior art. FIG. 6 is a schematic diagram for explaining an effect of the first embodiment. It is an enlarged view of H of FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The embodiment shown below is an embodiment corresponding to an area where the left-hand traffic is legalized, and in the area where the right-hand traffic is legalized, the left and right are reversed from the following embodiments.

(Embodiment 1)
In the first embodiment, a case where the vehicle steering control device of the present invention is applied to the driving support system 100 will be described as an example. In FIG. 1, the whole structure of the driving assistance system 100 of Embodiment 1 is shown. As shown in FIG. 1, the driving support system 100 includes a wheel speed sensor 1, a rudder angle sensor 2, a yaw rate sensor 3, an EPS_ECU 4, a distance measuring sensor 5, and a vehicle control ECU 10. The driving support system 100 is mounted on a vehicle.

<Schematic configuration of driving support system 100>
The wheel speed sensor 1 is a sensor that detects the speed of the host vehicle from the rotational speed of each rolling wheel, and transmits the detected host vehicle speed Vo to the in-vehicle LAN. The steering angle sensor 2 is a sensor that detects the steering angle of the host vehicle, and transmits the detected steering angle to the in-vehicle LAN. The yaw rate sensor 3 is a sensor that detects an angular velocity (that is, a yaw rate) around the vertical axis of the host vehicle, and transmits the detected yaw rate to the in-vehicle LAN.

  The EPS_ECU 4 controls the steering angle (that is, the steering angle) by operating the EPS actuator 11. The EPS actuator 11 is a mechanism that changes the steering angle based on a command signal from the EPS_ECU 4, and includes, for example, a reduction gear that rotates integrally with the intermediate shaft and a motor that rotates the reduction gear.

  The distance measuring sensor 5 is a sensor that detects a boundary position of a road area that can be traveled that exists in front of the host vehicle. For example, the distance measuring sensor 5 may be configured to use a radar or a camera.

  When the radar is used, as shown in FIG. 2, a laser beam or millimeter wave is applied to a predetermined range in front of the vehicle (see the broken line in FIG. 2), and the reflected light is received. A distance to an obstacle on the road such as a road boundary (for example, a guardrail or a curb) of a road ahead and a vehicle ahead is detected. And vehicle control ECU10 detects the position with respect to the own vehicle of the said road boundary and an obstruction from the distance data of the said road boundary and obstruction obtained with the radar. In addition, A of FIG. 2 represents the own vehicle.

  The predetermined range ahead of the host vehicle may be a range extending to the left side or the right side of the host vehicle. Moreover, it is good also as a structure which provides multiple ranging sensors 5 so that a sensing direction may differ. Note that the distance measuring sensor 5 may be configured to detect the position of the road boundary or the obstacle with respect to the own vehicle.

  When using a camera, a known image recognition technique is used to detect road boundaries (for example, white lines, guardrails, curbs, etc.) of roads ahead of the vehicle with respect to the vehicle and obstacles on the road such as vehicles ahead. do it. The distance from the vehicle to the road boundary can be calculated from the target position in the captured image if the camera installation position and the optical axis direction are determined. And the position calculated from the target position in the captured image.

  The vehicle control ECU 10 is mainly configured as a microcomputer, and each includes a known CPU, ROM, RAM, I / O, and a bus connecting them.

<Detailed Configuration of Vehicle Control ECU 10>
The vehicle control ECU 10 executes various processes based on various information input from the wheel speed sensor 1, the steering angle sensor 2, the yaw rate sensor 3, the EPS_ECU 4, and the distance measuring sensor 5. The vehicle control ECU 10 corresponds to the vehicle steering control device recited in the claims.

  As shown in FIG. 3, the vehicle control ECU 10 includes a current position specifying unit 101, a boundary position detecting unit 102, a road outer shape determining unit 103, a road boundary distance calculating unit 104, a road width direction distance calculating unit 105, and a curvature radius calculating unit 106. , Road shape determination unit 107, curve direction determination unit 108, restriction unit 109, first cut angle calculation unit 110, virtual boundary distance setting unit 111, conversion unit 112, position deviation calculation unit 113, converted position deviation calculation unit 114, A turning radius calculation unit 115, a second turning angle calculation unit 116, a target steering angle calculation unit 117, and a steering instruction unit 118 are provided.

  The current position specifying unit 101 performs current position specifying processing for sequentially specifying the current position of the host vehicle. As an example, in the current position specifying process, the vehicle position at a certain time is set as a starting point on a two-dimensional coordinate, and the vehicle speed Vo sequentially acquired from the wheel speed sensor 1 of the vehicle and the steering angle sensor 2 of the vehicle are sequentially acquired. The current position of the own vehicle is specified by sequentially calculating the current position of the own vehicle on the two-dimensional coordinates based on the steering angle Θ. The current position of the own vehicle is, for example, the center of the front wheel axle of the own vehicle.

  The current position specifying unit 101 determines the current position of the vehicle based on information obtained from other sensors such as a receiver for a satellite positioning system that detects the current position of the vehicle based on radio waves from the satellite. It is good also as a structure to calculate.

  The boundary position detection unit 102 sequentially detects the road boundary and the position of the obstacle with respect to the current position of the own vehicle from the road boundary and obstacle distance data obtained by the distance measuring sensor 5. As an example, the road boundary and the position of the obstacle may be configured to be represented as a position on the above-described two-dimensional coordinates.

  Based on the road boundary and the position of the obstacle detected by the boundary position detection unit 102, the road outer shape determination unit 103 sequentially determines the outer shape of the road area (hereinafter referred to as the road outer shape) on which the vehicle is to travel. As an example, a travel route for traveling while avoiding road boundaries and obstacles detected by the boundary position detection unit 102 is generated on the aforementioned two-dimensional coordinates, and has a predetermined width from the center line of this route to the left and right. Determine the road outline. For example, a road outline having a boundary line having a width corresponding to a distance corresponding to a distance of 1.75 m on the left and right with the travel route as a center line may be determined.

  It is assumed that the road outline determining unit 103 adds a new road outline to the road outline determined in the past. The vehicle control ECU 10 uses the road outline determined in the past, although the road outline itself at the current position of the vehicle cannot be determined from the road boundary or obstacle detected by the distance measuring sensor 5 at the current position of the own vehicle. The road outline of the current position of the vehicle can be determined.

  In addition, the vehicle control ECU 10 includes a road boundary distance calculation unit 104, a road width direction distance calculation unit 105, a curvature radius calculation unit 106, a road shape determination unit 107, a curve direction determination unit 108, a restriction unit 109, a first cutting angle. A calculation unit 110, a virtual boundary distance setting unit 111, a conversion unit 112, a position deviation calculation unit 113, a post-conversion position deviation calculation unit 114, a turning radius calculation unit 115, a second turning angle calculation unit 116, a target steering angle calculation unit 117, And the steering instruction | indication part 118 performs the below-mentioned 1st request angle calculation related process, 2nd request angle calculation related process, and behavior control related process.

  As an outline, in the first required angle calculation related process, a curve turning required tire turning angle θ_curv for steering the vehicle according to the curvature radius of the road outer shape is calculated. In the second required angle calculation related processing, a lane keep required tire turning angle θ_lane for adjusting the vehicle to the center of the road width of the road outline is calculated. In the behavior control-related processing, the vehicle turns to the road using the curve turning required tire turning angle θ_curv calculated in the first required angle calculation-related processing and the lane keep required tire turning angle θ_lane calculated in the second required angle calculation-related processing. The vehicle is adjusted to the center of the road width of the road outline while being steered according to the curvature radius of the outline.

<First request angle calculation related processing>
Here, the first required angle calculation-related processing in the vehicle control ECU 10 will be described using the flowchart shown in FIG. 4 and the schematic diagrams of FIGS. 5 and 6. As described above, in the first required angle calculation related processing, the curve turning required tire turning angle θ_curv for steering the vehicle according to the curvature radius of the road outer shape is calculated. The flowchart of FIG. 4 may be configured to start, for example, at regular intervals. In the present embodiment, as an example, the fixed period is set to 100 msec.

  First, in step S <b> 1, the road boundary distance calculation unit 104 calculates the road boundary distance Dr from the current position of the host vehicle specified by the current position specifying unit 101 and the road outer shape determined by the road outer shape determination unit 103. The road boundary distance Dr is based on the vehicle's current position (that is, the front wheel axle center) on the tangent line drawn with respect to the road width centerline (hereinafter referred to as the road width centerline). To the road boundary located in front of the host vehicle (see FIG. 5).

  In step S <b> 2, the road width direction distance calculating unit 105 calculates the road width direction distance L from the current position of the vehicle specified by the current position specifying unit 101 and the road outer shape determined by the road outer shape determining unit 103. The road width direction distance L is the distance of the vehicle center in the road width direction with respect to one boundary of the road outer shape (see FIG. 5). The one boundary here is a road boundary located in front of the host vehicle used when the road boundary distance Dr is calculated in S1.

  In the flowchart of FIG. 4, the configuration in which the process of S <b> 2 is performed after the process of S <b> 1 is shown. For example, the order of the process of S1 and the process of S2 may be reversed, or the process of S1 and the process of S2 may be performed in parallel.

In step S3, the curvature radius calculation unit 106 calculates the curvature radius of the road width centerline for the road outline located in front of the host vehicle from the road boundary distance Dr calculated in S1 and the road width direction distance L calculated in S2. A certain road width centerline curvature radius Ra is calculated (see FIG. 5). This S3 corresponds to a curvature radius calculation unit in claims. The road outline located in front of the vehicle referred to here is the road boundary located in front of the vehicle used when the road boundary distance Dr is calculated in S1. The road width centerline curvature radius Ra corresponds to the curvature radius of the claims. The road width centerline radius of curvature Ra is calculated by Expression 5 derived from Expressions 2 to 4 below.

  The road width centerline curvature radius Ra calculated in S3 is sequentially stored in the memory of the vehicle control ECU 10. Therefore, each time the flowchart of FIG. 4 is executed at regular intervals, the road width centerline curvature radius Ra is sequentially stored. The memory stores at least the road width centerline curvature radius Ra calculated by the new processing of S3 and the road width centerline curvature radius Ra calculated by the previous processing of S3 before the new processing of S3. Shall. For example, the storage in the memory may be configured to be erased when, for example, the ignition power of the own vehicle is turned off and the vehicle control ECU 10 is turned off.

  For example, as in the case where a straight road continues in front of the host vehicle, the road boundary located in front of the host vehicle is not recognized for the road profile determined by the road profile determining unit 103, and the road boundary distance Dr cannot be calculated. In such a case, the road width centerline curvature radius Ra may be infinite or set to a sufficiently large value such as R10000 m.

  In step S4, the road shape determination unit 107 determines whether the road contour located in front of the host vehicle is a curved road or a straight road from the road width centerline curvature radius Ra calculated in S3. This S4 corresponds to the road shape determination unit in the claims. The road outline located in front of the vehicle referred to here is the road boundary located in front of the vehicle used when the road boundary distance Dr is calculated in S1.

  As an example, if the road width centerline curvature radius Ra calculated in S3 is greater than or equal to a preset threshold value, it is determined as a straight road, and if it is less than the threshold value, it is determined as a curved road. The threshold value may be a value of a radius of curvature that can be said to be a straight road, and may be, for example, R10000 m.

  Here, the determination in S4 will be described with reference to FIG. In FIG. 6, the example in the case of drive | working the S-shaped curve area | region arranged in order of the straight line, the right curve, the straight line, the left curve, and the straight line is shown. In FIG. 6, the change in the road width centerline curvature radius Ra (see B) and threshold (see C) for the straight line, the right curve, and the area up to the straight line (hereinafter referred to as the first half area), the subsequent straight line, the left curve, and the straight line The change (refer to D) and the threshold value (refer to E) of the road width centerline curvature radius Ra for the region (hereinafter referred to as the second half region) are shown. The road width centerline curvature radius Ra in FIG. 6 is an output value from the curvature radius calculation unit 106.

  FIG. 6 is a schematic diagram, and it is easy to understand the case of a right curve, a case of a straight road, and a case of a left curve. The direction of the vertical axis of the graph showing is changed. Actually, the threshold value is the same in the first half area and the second half area, and both graphs are connected by a dotted line indicated by F in the figure. The curve direction is actually clarified by the determination in step S12 described later, and the process for distinguishing the curve direction is not performed in S4.

  As shown in FIG. 6, when the road width centerline curvature radius Ra is greater than or equal to a threshold value, the road is determined to be a straight road, and when the road width centerline curvature radius Ra is greater than or equal to the threshold value, a curve road is determined. Determined. As described above, FIG. 6 is a schematic diagram, and the process up to the curve direction is not determined in the process of S4.

  In step S5, when it is determined in S4 that the road boundary located in front of the host vehicle is a curved road (YES in S5), the process proceeds to step S7. On the other hand, if it is determined in S4 that the road boundary located in front of the vehicle is a straight road (NO in S5), the process proceeds to step S6, and the curve turning required tire turning angle θ_curv is assumed to be 0 in S6. Terminate the process. In other words, when the vehicle is running on a straight road and is not close to a curved road, and steering according to the road width centerline curvature radius Ra is not necessary, steering according to the road width centerline curvature radius Ra is performed. I will not do it.

  In step S7, the restriction unit 109 determines the current first requested angle from the road width centerline curvature radius Ra (hereinafter referred to as the previous road width centerline curvature radius Ra) calculated in the previous first requested angle calculation related process. The rate of change of the road width centerline curvature radius Ra (hereinafter, this road width centerline curvature radius Ra) calculated in the calculation related process is calculated. In the example of the present embodiment, since the first required angle calculation related processing is performed every 100 msec, the value obtained by subtracting the previous road width centerline curvature radius Ra from the current road width centerline curvature radius Ra is divided by 100 msec. Thus, the rate of change may be calculated.

  As for the previous road width centerline curvature radius Ra, what is stored in the memory as described in S3 may be read and used. If the previous road width centerline curvature radius Ra is not stored in the memory, the rate of change may be set to 0, for example.

  In step S8, when the change rate calculated in S7 is a positive increase rate (YES in S8), the process proceeds to step S9. On the other hand, when the rate of change calculated in S7 is 0 or the rate of decrease is a negative value (NO in S8), the process proceeds to step S11.

  In step S9, the limiting unit 109 determines whether the increase rate calculated in S7 is equal to or higher than the upper limit value. The upper limit value may be approximately the rate of change in a region where the rate of change of the radius of curvature is large, which corresponds to a connecting portion between a short straight road that connects curved roads in opposite directions in the S-curve area and the curved roads before and after the short straight road. For example, the upper limit value may be about R250 m / 100 msec.

  In step S10, the limiting unit 109 calculates the road width centerline curvature radius Ra where the increase rate from the previous road width centerline curvature radius Ra is the above-described upper limit value, and the calculated value (hereinafter referred to as the increase rate limit value). ) Is determined as the road width centerline curvature radius Ra for calculating the curve turning required tire turning angle θ_curv, and the process proceeds to step S12. That is, a predetermined upper limit is set for the increasing rate of the road width centerline curvature radius Ra.

  In step S11 in the case where the change rate calculated in S7 is 0 or a negative decrease rate, the limiting unit 109 uses the value of the road width centerline curvature radius Ra calculated in S3 as it is. The road turning centerline curvature radius Ra for calculating the curve turning required tire turning angle θ_curv is determined, and the process proceeds to step S12. That is, no lower limit is set for the reduction rate of the road width centerline curvature radius Ra.

  In step S12, the curve direction determination unit 108 determines the curve direction of the road boundary determined to be a curved road. As an example, if the road boundary located in front of the vehicle is the road boundary on the left side of the vehicle, it is determined as a right curve, and the road boundary located in front of the vehicle is the road boundary on the right side of the vehicle Is determined to be a left curve. This S12 corresponds to a curve direction determination unit in the claims.

  In step S13, the first turning angle calculation unit 110 determines from the road width centerline curvature radius Ra determined by the limiting unit 109, the curve direction determined in S7, and the wheelbase length WB of the own vehicle (see FIG. 5). Then, the curve turning required tire turning angle θ_curv (see FIG. 5) is calculated, and the processing of FIG. 4 is terminated.

  If it is determined in S11 that the aforementioned increase rate limit value is the road width centerline curvature radius Ra for calculating the curve turning required tire turn angle θ_curv, this increase rate limit value is used as the curve turning request tire turn angle θ_curv. Will be used as the road width centerline curvature radius Ra for calculating. On the other hand, in S12, when the road width centerline curvature radius Ra calculated in S3 is determined as the road width centerline curvature radius Ra for calculating the curve turning required tire turning angle θ_curv, the road calculated in S3 The width center line curvature radius Ra will be used. The first cut angle calculation unit 110 and S13 correspond to a cut angle calculation unit in claims.

The curve turning required tire turning angle θ_curv is calculated by the following equation 1. The sgn (RL) in Expression 1 is 1 when the curve direction determined in S7 is a right curve, and is -1 when the curve direction is a left curve. The wheel base length WB of the host vehicle may be configured to use a value stored in advance in the memory of the vehicle control ECU 10.

<Second request angle calculation related processing>
Next, the second required angle calculation related process in the vehicle control ECU 10 will be described using the flowchart shown in FIG. As described above, in the second required angle calculation related processing, the lane keep required tire turning angle θ_lane for adjusting the own vehicle to the center of the road width of the road outline is calculated. The flowchart of FIG. 7 may be configured to be performed in parallel with the first required angle calculation related process, for example, at regular intervals.

  First, in step S21, the road boundary distance calculation unit 104 calculates the road boundary distance Dr as in step S1. In step S22, when the road boundary distance Dr can be calculated (YES in S22), the process proceeds to step S24. On the other hand, when the road boundary located in front of the host vehicle is not recognized for the road outline determined by the road outline determination unit 103 and the road boundary distance Dr cannot be calculated (NO in S22), the process proceeds to step S23.

  In step S23, the virtual boundary distance setting unit 111 sets a predetermined virtual boundary distance Dr_virtual as the road boundary distance Dr. This virtual boundary distance Dr_virtual can be arbitrarily set, and may be about 50 m, for example.

  In step S <b> 24, the position deviation calculating unit 113 calculates the vehicle lateral position deviation Δw from the current position of the host vehicle specified by the current position specifying unit 101 and the road outer shape determined by the road outer shape determining unit 103. The own vehicle lateral position deviation Δw is a position deviation of the own vehicle center in the road width direction with respect to the road width center line.

  In step S25, the conversion unit 112 performs a distance conversion process. In the distance conversion process, when the road boundary distance Dr can be calculated in S21, a post-conversion boundary distance Dr ′ obtained by converting the road boundary distance Dr into a value in the traveling direction of the host vehicle is calculated. If the virtual boundary distance Dr_virtual has been set in S23, the converted boundary distance Dr ′ is calculated by converting the virtual boundary distance Dr_virtual into a value for the traveling direction of the host vehicle.

The conversion from the road boundary distance Dr to the post-conversion boundary distance Dr ′ may be calculated using the following formulas 6-8. In Expression 6, an angle θw for correcting the vehicle lateral position deviation Δw is calculated from the road boundary distance Dr calculated in S21 and the vehicle lateral position deviation Δw calculated in S24.

In Equation 7, the target travel direction for adjusting the traveling direction of the own vehicle and the own vehicle to the road width center line is calculated from the angle θw calculated in Equation 6 and the inclination θs of the traveling direction of the own vehicle with respect to the road width center line. The angle difference θws with respect to the direction is calculated. The inclination θs is calculated from the current position of the host vehicle specified by the current position specifying unit 101 and the road outer shape determined by the road outer shape determining unit 103.

  In Expression 8, the converted boundary distance Dr ′ is calculated from the angle difference θws calculated in Expression 7 and the distance Z that is the distance from the own vehicle to the road width center line of the virtual straight road at the position of the road boundary distance Dr. Is calculated. The distance Z is calculated from the current position of the host vehicle specified by the current position specifying unit 101 and the road outer shape determined by the road outer shape determining unit 103.

  The virtual straight road may be obtained by drawing a tangent to the road boundary of the road outline with reference to the front wheel axle position of the own vehicle. For example, the distance Z may be the distance from the front wheel axle center of the host vehicle to the intersection of the road width center line of the virtual straight road and the road boundary of the road outline determined by the road outline determining unit 103.

The distance Z is a virtual distance from the vehicle to the road width center line at the position of the virtual boundary distance Dr_virtual when the virtual boundary distance Dr_virtual is set in S23. For example, the distance Z may be a distance from the center of the front wheel axle of the host vehicle to a virtual boundary distance Dr_virtual on the road width center line of the road outline determined by the road outline determination process.

The conversion from the virtual boundary distance Dr_virtual to the post-conversion boundary distance Dr ′ may be calculated using the following Expression 9 and Expressions 7 and 8 described above. In Equation 9, the angle θw for correcting the vehicle lateral position deviation Δw is calculated from the virtual boundary distance Dr_virtual set in S23 and the vehicle lateral position deviation Δw calculated in S24.

  In step S <b> 26, the post-conversion position deviation calculation unit 114 calculates a post-conversion position deviation Δw ′ obtained by converting the own vehicle lateral position deviation Δw into a value in the traveling direction of the own vehicle. What is necessary is just to set it as the structure calculated using the following formula | equation 10 about the conversion from the own vehicle lateral position deviation Δw to the converted position deviation Δw ′.

In Expression 10, when the road boundary distance Dr can be calculated in S21, the converted position deviation Δw ′ is calculated from the angle difference θws calculated using Expressions 6 and 7 and the distance Z described above. If the virtual boundary distance Dr_virtual has been set in S23, the post-conversion position deviation Δw ′ is calculated from the angle difference θws calculated using Equations 9 and 7 and the distance Z described above.

  In addition, the process of S25 and the process of S26 may be reverse order, and it is good also as a structure performed in parallel.

In step S27, it is necessary for the turning radius calculation unit 115 to adjust the vehicle to the center line of the road width using the converted boundary distance Dr ′ calculated in S25 and the converted position deviation Δw ′ calculated in S26. A simple turning radius Rw is calculated. The turning radius Rw is calculated by Expression 13 derived from Expressions 11 to 12 below.

  In step S28, the second turning angle calculation unit 116 calculates the lane keeping required tire turning angle θ_lane based on the turning radius Rw calculated in S27, the wheelbase length WB of the host vehicle, and the aforementioned angle difference θws. Then, the process of FIG.

The lane keep request tire turning angle θ_lane is calculated by the following Expression 14. The sgn (θws) in Expression 14 is 1 when the angle difference θws is a positive value, and is −1 when the angle difference θws is a negative value. The wheel base length of the host vehicle may be configured to use a value stored in advance in the memory of the vehicle control ECU 10.

<Behavior control related processing>
Subsequently, behavior control related processing in the vehicle control ECU 10 will be described using a flowchart shown in FIG. As described above, the behavior control related process uses the curve turning required tire turning angle θ_curv calculated in the first required angle calculation related processing and the lane keep required tire turning angle θ_lane calculated in the second required angle calculation related processing. The vehicle is adjusted to the center of the road width of the road outline while the vehicle is steered according to the radius of curvature of the road outline. The flowchart of FIG. 8 is performed every time the curve turning required tire turning angle θ_curv and the lane keeping required tire turning angle θ_lane are newly calculated by, for example, the first required angle calculation related processing and the second required angle calculation related processing. And it is sufficient.

  In step S31, the target steering angle calculation unit 117 performs the curve turning required tire turning angle θ_curv calculated in the first required angle calculation related processing and the lane keep required tire cutting angle θ_lane calculated in the second required angle calculation related processing. From this, a target steering angle Θ (hereinafter, target steering angle Θ) is calculated. The target steering angle Θ is a steering angle Θ for adjusting the vehicle to the center of the road width of the road outline while steering the vehicle according to the curvature radius of the road outline. This S31 corresponds to a target cutting angle calculation unit.

The target steering angle Θ is calculated using the following formulas 15 and 16. First, as shown in Expression 15, the curve turning required tire turning angle θ_curv calculated in the first required angle calculation related processing and the lane keep required tire cutting angle θ_lane calculated in the second required angle calculation related processing are added. In addition, the required tire turning angle θ is calculated.

Subsequently, the target steering angle Θ is calculated using the equation 16 from the required tire turning angle θ. N in Expression 16 is a ratio (constant) between the steering angle (that is, the steering angle) Θ and the tire turning angle θ.

  In step S32, the steering instructing unit 118 transmits the target steering angle Θ calculated in S31 to the EPS_ECU 4, thereby matching the steering angle of the host vehicle with the target steering angle Θ, and the process of FIG. 8 ends. This S32 corresponds to the steering instruction section in the claims. Receiving the target steering angle Θ, the EPS_ECU 4 controls the EPS actuator 11 while detecting the steering angle by the steering angle sensor 2, and changes the steering angle in a direction approaching the target steering angle Θ at a predetermined change speed.

<Summary of Embodiment 1>
According to the configuration of the first embodiment, the curve turning required tire turning angle θ_curv for steering the host vehicle according to the road width centerline curvature radius Ra of the road profile, and the lane for adjusting the host vehicle to the center of the road width. The keep request tire cutting angle θ_lane can be calculated. Since the steering angle is controlled with the steering angle Θ corresponding to the required tire turning angle θ as the sum as a target, steering corresponding to the curve R of the road outline and steering matching the center of the road outline in the width direction are performed. It becomes possible.

  Further, the curve turning required tire turning angle θ_curv and the lane keep requesting tire turning angle θ_lane are both calculated in consideration of the wheelbase length WB of the own vehicle. Thus, there is no discrepancy with the steering to match the center in the width direction, and the vehicle can be easily converged to the center position of the traveling road not only on the straight road section but also on the curved road section. As a result, it is possible to stably converge the vehicle to the center position of the travel path while steering the vehicle according to the radius of curvature of the travel path.

  In addition, according to the configuration of the first embodiment, by providing a predetermined upper limit to the increase rate of the road width centerline curvature radius Ra used for calculating the curve turning required tire turning angle θ_curv, the driver feels uncomfortable in the S-curve region. There is an effect that it is possible to automatically control the steering angle that is rarely given. Details are as follows.

  First, a problem when it is assumed that a predetermined upper limit is not provided for the increasing rate of the road width centerline curvature radius Ra used for calculating the curve turning required tire turning angle θ_curv will be described with reference to FIG. FIG. 9 also shows an example in which the vehicle travels in an S-shaped curve region arranged in the order of a straight line, a right curve, a straight line, a left curve, and a straight line, as in FIG. In FIG. 9, as in FIG. 6, the change (see B) and threshold (see C) of the road width centerline curvature radius Ra for the straight line, the right curve, and the region up to the straight line (hereinafter referred to as the first half region), followed by the straight line , A change in the road width centerline curvature radius Ra (see D) and a threshold value (see E) for the area up to the left curve and the straight line (hereinafter, the second half area). The road width centerline curvature radius Ra in FIG. 9 is an output value from the curvature radius calculation unit 106.

  FIG. 9 is also a schematic diagram similar to FIG. 6, and in order to make it easier to understand the case of a right curve, a straight road, and a left curve, a road width center line in the first half area and the second half area. The direction of the vertical axis of the graph showing the change in the curvature radius Ra is changed. Actually, the threshold value is the same in the first half area and the second half area.

  As shown in FIG. 9, in the S-shaped curve region, there is a region where the radius of curvature R greatly changes between a short straight road connecting curves in opposite directions and a curved road before and after the straight road. Therefore, the behavior of the own vehicle is slightly fluctuated, and a situation occurs in which the road outline in front of the own vehicle becomes a straight road, a right curve road, or a left curve road. In such a situation, the road width centerline curvature radius Ra calculated in S3 repeats abrupt increase and decrease (see G in FIG. 9). Therefore, in such a situation, when the first turning angle calculation unit 110 calculates the curve turning required tire turning angle θ_curv that directly corresponds to the road width centerline curvature radius Ra calculated in S3, the steering instruction unit 118 performs the steering direction. This causes a problem of changing frequently.

  On the other hand, according to the configuration of the first embodiment, a predetermined upper limit is provided for the increase rate of the road width centerline curvature radius Ra used for calculating the curve turning required tire turning angle θ_curv. Even if the road width centerline curvature radius Ra suddenly increases, the road width centerline curvature radius Ra does not have to be reflected as it is on the curve turning required tire turning angle.

  Specifically, since a predetermined upper limit (see the slope indicated by the dotted arrow in FIG. 11) is provided for the increasing rate of the road width centerline curvature radius Ra, as shown in FIG. 10H and FIG. A sudden increase in the road width centerline curvature radius Ra output to the section 110 is suppressed. This also makes it possible to suppress a rapid change in the curve turning required tire turning angle θ_curv that accompanies a rapid increase in the road width centerline curvature radius Ra. As a result, it is possible to suppress the steering direction from being frequently changed by the steering instruction unit 118, and to automatically control the steering angle with little discomfort to the driver even in the S-curve region.

  FIG. 10 is a schematic diagram similar to FIG. 9 except that the road width centerline curvature radius Ra is an output value from the restriction unit 109 to the first cut angle calculation unit 110. . FIG. 11 is an enlarged view of H in FIG.

  In addition, since there is no lower limit for the reduction rate of the road width centerline curvature radius Ra, the road width centerline curvature radius Ra is rapidly reduced, such as a region where a straight road in the S-curve region is shifted to a curved road. It becomes possible to prevent a delay in turning off the steering in the region. As a result, it is possible to prevent deviation from the road boundary due to a delay in turning the steering wheel when entering a curve.

<Modification 1>
In the first embodiment, the restriction unit 109 has a configuration in which a lower limit is not provided for the reduction rate of the road width centerline curvature radius Ra, but is not limited thereto. For example, a configuration may be adopted in which a lower limit is provided for the reduction rate of the road width centerline curvature radius Ra (hereinafter, modified example 1).

  In the first modification, the limiting unit 109 determines whether or not the rate of decrease from the previous road width centerline curvature radius Ra is equal to or less than a predetermined lower limit value. If it is determined that the road width centerline curvature radius Ra is equal to or less than the lower limit value, the road width centerline curvature radius Ra is calculated such that the rate of decrease from the previous road width centerline curvature radius Ra is the aforementioned lower limit value. The road width centerline curvature radius Ra for calculating the required tire turning angle θ_curv is determined. On the other hand, if it is determined that the value is larger than the lower limit value, the road width centerline curvature radius Ra calculated in S3 is determined as the road width centerline curvature radius Ra for calculating the curve turning required tire turning angle θ_curv.

  Here, the lower limit value may be a value that has an absolute value smaller than the above-described upper limit value and is estimated to be unlikely to deviate from the road boundary due to a delay in turning off the steering wheel when entering a curve.

  According to the configuration of the first modified example, the rapid change in the tire turn angle required for the curve turning due to the rapid increase in the curvature radius Ra is suppressed, and the sharp turn angle required for the curve turning tire due to the rapid decrease in the curvature radius Ra. It becomes possible to suppress changes. In addition, the reduction rate of the road width centerline curvature radius Ra has a lower limit that is estimated to be unlikely to deviate from the road boundary due to a delay in turning the steering wheel when entering the curve. While preventing the departure from the road boundary due to the delay, it is possible to automatically control the steering angle with less discomfort to the driver in the S-curve area.

<Modification 2>
In S12 described above, when the road width centerline curvature radius Ra calculated in S3 is equal to or larger than a preset value, the curve direction determination unit 108 determines the curve determined in the previous first required angle calculation related processing. While maintaining the direction, if the value is less than the set value, the configuration may be such that the curve direction is determined in the same manner as in the first embodiment (hereinafter referred to as modified example 2). The set value here is smaller than the threshold value used for the determination of the straight road and the curved road described above, and is a value about the curvature radius of the area closer to the curved road side than the connecting portion between the straight road and the curved road. For example, R600m.

  In the road outline, the behavior of the host vehicle is a little on a short straight road that connects curves in opposite directions in the S-curve area where the road width centerline curvature radius Ra is equal to or greater than a preset value, and a curve road before and after that. A situation in which the outer shape of the road in front of the host vehicle becomes a right curve road or a left curve road can occur only by wobbling. In such a situation, since the inversion of the determination result in the curve direction frequently occurs, if the determination results are adopted one by one, the steering direction must be changed frequently.

  On the other hand, according to the configuration of the modified example 2, when the road width centerline curvature radius Ra is equal to or larger than a preset setting value, the curve direction determined in the previous first required angle calculation related process is maintained. Therefore, it is possible to suppress frequent inversion of the determination result of the curve direction.

<Modification 3>
In Embodiment 1, although the structure which determines a road external shape from the detection result of autonomous sensors, such as the ranging sensor 5 and a camera, was shown, it does not necessarily restrict to this. For example, it is good also as a structure (henceforth modification 3) which determines a road external shape based on the information obtained from other vehicles, such as a preceding vehicle, by inter-vehicle communication.

  In the third modification, the vehicle control ECU 10 determines the travel locus of the preceding vehicle based on the vehicle information such as the vehicle speed Vp and the steering angle Θ of the preceding vehicle acquired by inter-vehicle communication. As an example, the vehicle position at a certain point in time is set as a starting point on a two-dimensional coordinate, and is ahead of the starting point by a length corresponding to the distance between the own vehicle detected based on the signal from the distance measuring sensor 5 and the preceding vehicle. The separated position is set as the initial position of the traveling vehicle. Then, based on the vehicle speed Vp and the steering angle Θ of the preceding vehicle that are sequentially acquired, the traveling locus of the preceding vehicle is determined by sequentially calculating the traveling locus points following the initial position.

  Subsequently, a configuration may be adopted in which a virtual road outline ahead is determined from the determined travel locus of the preceding vehicle as a starting point. For example, a road outline having a boundary line with a width corresponding to a distance corresponding to a distance of 1.75 m on the left and right with the travel locus of the preceding vehicle as a center line may be determined. Then, after determining the virtual road outline, the same processing as described in the first embodiment is performed.

  In addition, as a configuration for performing the determination of the traveling locus of the preceding vehicle and the determination of the road outer shape with the device mounted on the preceding vehicle, and acquiring the traveling locus and the information of the road outer shape transmitted from the preceding vehicle by inter-vehicle communication. Also good.

  Moreover, it is good also as a structure which determines the driving | running | working locus | trajectory and road outline of a preceding vehicle based on the inner / outer wheel speed ratio of a preceding vehicle. Specifically, based on the fact that the angular velocity of the inner and outer wheels is the same, the radius of curvature of the curved road is calculated from the inner and outer wheel speed ratio by a known method, and the travel locus and road outline are determined. Good.

  In addition, the configuration may be such that the travel locus of the preceding vehicle and the road profile are determined based on the yaw rate of the preceding vehicle. Moreover, it is good also as a structure which determines a driving | running | working locus | trajectory or a road external shape using together the speed of a preceding vehicle, a steering angle, an inner / outer wheel speed ratio, and a yaw rate. In this case, the values calculated by different methods may be averaged.

  The configuration of Modification 3 has the same effect as that of Embodiment 1 because there is no substantial difference in configuration except that the information acquisition method for determining the road outline is different from that of Embodiment 1.

<Modification 4>
Moreover, it is good also as a structure (henceforth modification 4) which determines a road external shape based on the information obtained from the roadside machine etc. by road-to-vehicle communication. In the case of the fourth modification, the vehicle outer shape may be determined by the vehicle control ECU 10 based on information acquired from a roadside machine or the like by road-to-vehicle communication.

  The information acquired from the roadside machine or the like may be any information as long as the vehicle control ECU 10 can determine the road profile of the road area where the host vehicle should travel. For example, it may be information indicating the linear structure of the road around the target intersection position, and may be road linear information including information on the position of the target intersection. The road alignment information is information such as the position of the target intersection (latitude and longitude) as the positioning result of the satellite positioning system, the distance to the predetermined structural change point based on the position of the target intersection, the dimension of the road alignment, etc. To do.

  In addition, it may be travel history information obtained by collecting past travel histories of a plurality of vehicles. The travel history information is information on vehicle speed and steering angle, for example.

  The vehicle control ECU 10 determines the road outer shape of the road area where the host vehicle should travel based on the information acquired from the roadside machine etc., and after determining the road outer shape, the vehicle control ECU 10 is the same as described in the first embodiment. Processing shall be performed.

  The configuration of the modification 4 has the same effect as that of the first embodiment except that the information acquisition method for determining the road outer shape is substantially the same except for the difference from the first embodiment.

  The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims, and the technical means disclosed in different embodiments can be appropriately combined. Such embodiments are also included in the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 10 Vehicle control ECU (Vehicle steering control apparatus), 101 Current position specification part, 103 Road external shape determination part, 109 Restriction part, S3 Curvature radius calculation part, S4 Road shape determination part, S6 Curve direction determination part, S13 Cutting angle calculation Unit, S31 target cutting angle calculation unit, S32 steering instruction unit

Claims (3)

Mounted on the vehicle,
A current position specifying unit (101) for sequentially specifying the current position of the own vehicle;
A road outer shape determination unit (103) for determining a road outer shape that is an outer shape of a road area in which the host vehicle is to travel;
A radius of curvature for sequentially calculating a radius of curvature Ra for the road profile in front of the vehicle based on the current position of the vehicle sequentially specified by the current position specification unit and the road profile determined by the road profile determination unit. A calculation unit (S3);
A turning angle calculation unit (S13) for calculating a curve turning required tire turning angle θ_curv for steering the vehicle according to the curvature radius Ra using the curvature radius Ra calculated by the curvature radius calculation unit;
A target turning angle calculation unit (S31) for calculating a steering turning angle Θ according to the curve turning required tire turning angle θ_curv calculated by the turning angle calculation unit;
A vehicle steering control device (10) comprising a steering instruction unit (S32) for controlling the steering angle with the steering angle Θ calculated by the target angle calculation unit as a target,
When the curvature radius Ra sequentially calculated by the curvature radius calculation unit is increasing, a predetermined increase rate of the curvature radius Ra used to calculate the curve turning required tire turning angle by the turning angle calculation unit is predetermined. The vehicle steering control device is provided with a limiting unit (109) that sets an upper limit of the above. In claim 1,
The limiting unit uses the curvature radius Ra used to calculate the curve turning required tire turning angle by the turning angle calculation unit when the curvature radius Ra sequentially calculated by the curvature radius calculating unit is decreasing. The vehicle steering control device is characterized in that no lower limit is set for the rate of decrease of the vehicle. In claim 1 or 2,
A road shape determination unit (S4) for determining whether the road outline in front of the vehicle is a curved road or a straight road based on the curvature radius Ra calculated by the curvature radius calculation unit;
A curve direction determination unit (S7) for determining a curve direction of the curved road when the road shape determination unit determines that the road outline in front of the host vehicle is a curved road;
The cut angle calculation unit determines the curvature radius Ra calculated by the curvature radius calculation unit and the curve direction determination unit when the road shape determination unit determines that the road outline in front of the vehicle is a curved road. The curve turning required tire turning angle θ_curv for steering the vehicle according to the curvature radius Ra is calculated from the curve direction and the wheel base length WB of the vehicle according to the equation (1). Vehicle steering control device.

Ra: radius of curvature WB: wheelbase length RL = 1: right curve RL = -1: left curve

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