JP6176194B2 - Lane maintenance support system - Google Patents

Description

  The present invention relates to a lane keeping support system.

  In the case of vehicles, particularly automobiles, steering is performed in a direction opposite to the direction of departure from the lane (that is, the direction toward the center of the lane) in order to support lane maintenance while driving, that is, to prevent lane departure. There is a tendency to increase the number of lane keeping assist torques to be applied. Since the steering force in the direction in which the lane keeping assist torque is applied becomes light, the driver is naturally urged to return to the lane center position. Of course, the magnitude of the assist torque for maintaining the lane is set to a size that can be overcome by the driver so as not to hinder the steering performed when the driver actively changes the lane.

  For lane keeping control, the road ahead of the host vehicle is photographed by a camera, and left and right traveling division lines (so-called white lines) that define the traveling lane of the host vehicle are detected from the captured images. The lane keeping assist torque is applied so that the host vehicle travels in the center of the white line. Patent Document 1 discloses a method for changing the holding hysteresis width of the steering assist torque in accordance with the grip force (that is, the lateral G) of the wheel in order to easily obtain road information.

JP 2011-201388 A

  By the way, the application of the lane keeping assist torque by the lane keeping control is also executed when traveling on a curve, but the lane keeping assist torque is increased as the lateral G increases. However, it has been found that when the assist torque for maintaining the lane becomes larger than a certain level during turning, there is a problem that the driving posture is difficult to take and the tires are easily fatigued.

  In pursuit of such a cause, the steering reaction force from the steering wheel to the driver is reduced by increasing the lane keeping assist torque, and accordingly the lateral direction in which the driver holds the driver in the left-right direction by the seat back. It was found that this was because the frictional force was reduced. That is, the steering reaction force acts to press the upper body of the driver against the seat back. However, when the steering reaction force decreases due to an increase in the lane keeping assist torque, the centrifugal force based on the lateral G rather than the lateral friction force. Thus, the upper body of the driver is tilted to the outside of the turn considerably, and the driver's neck is tilted accordingly. And the muscle strength of the driver's neck muscles (thoracic mastomas) and the thighs (quadriceps) located on the outside of the turn are increased, which is the cause of fatigue. Turned out to be.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a lane keeping support system capable of reducing driver fatigue during turning while performing lane keeping control. .

In order to achieve the above object, the following solution is adopted in the present invention. That is, as described in claim 1,
In the lane keeping assist system, the assist torque for maintaining the lane in the direction of preventing the own vehicle from deviating from the driving lane is applied in a size that can be overcome by the driver.
Lateral G detection means for detecting lateral G acting on the host vehicle;
When the lateral G detected by the lateral G detecting means is equal to or greater than a predetermined value set in advance , the lateral frictional force between the driver and the seat back acts on the driver based on the lateral G. As described above, assist torque correction means for suppressing an increase in the assist torque for maintaining the lane,
It is supposed to be equipped with.

According to the above solution, the assist torque for maintaining the lane is unnecessarily increased, but is suppressed, and accordingly, the steering force that the driver should exhibit is increased, and the driver and the seat back based on the steering reaction force are increased. The lateral frictional force between them can be kept large. Accordingly, the driver can prevent or suppress the upper body and neck from tilting from a preferable driving posture, and can reduce fatigue during turning. In addition to the above, it is preferable to set the lane keeping assist torque to a sufficiently large value within a range in which the driver is not fatigued.

A preferred mode based on the above solution is as described in claim 2 and the following claims. That is,
The assist torque correcting means gradually decreases the gain amount for calculating the lane keeping assist torque according to the increase in the lateral G when the lateral G detected by the lateral G detecting means is equal to or greater than the predetermined value. (Corresponding to claim 2). In this case, both the demand for maintaining the lane and the driver's fatigue reduction can be satisfied at a high level.

  The assist torque correcting means is configured to hold the lane keeping assist torque at the immediately preceding lane keeping assist torque when the lateral G detected by the lateral G detecting means is equal to or greater than the predetermined value. 3 correspondence). In this case, the driver's fatigue reduction can be satisfied at a very high level.

The lateral frictional force includes a static frictional force between the driver and the seatback, a load acting on the seatback due to the weight of the driver's upper body, and a steering reaction force acting on the seatback through the arm that grips the steering wheel. It is determined based on the above (corresponding to claim 4 ). In this case, the lateral frictional force corresponding to claim 1 can be accurately determined, and the effect corresponding to claim 1 can be sufficiently exerted.

  According to the present invention, it is possible to reduce driver fatigue during turning while performing lane keeping control.

The block diagram which shows the example of a control system of the lane maintenance assistance system to which this invention was applied. The characteristic view which shows the example of a change of the width | variety of the hysteresis according to the presence or absence of the assist torque for lane keeping. The figure for demonstrating determination of a target yaw rate. The figure which shows the example of a setting of the front gaze time T in FIG. The characteristic view which shows the example of a setting of the target steering torque which a driver | operator exhibits according to a target yaw rate. The characteristic view which shows the example of a setting of the reference | standard hysteresis width according to steering angular velocity. The figure which shows the example of a setting of a viscous torque. The flowchart which shows the example of control of this invention. The flowchart which shows the example of control of this invention. FIG. 10 is a characteristic diagram used for the control of FIG. 9. The figure for demonstrating the muscular site | part which a driver | operator exhibits during turning. It is explanatory drawing for determining lateral direction frictional force, and the figure which looked the driver | operator and the seat back from the side. The figure which shows the relationship between a lateral friction force and a centrifugal force, and the figure which looked at the driver | operator and the seat back from the information. The figure which shows collectively the concrete numerical example of the code | symbol used in explanatory drawing in FIG. 12, FIG. The characteristic view which shows the relationship between assist torque for lane maintenance, and lateral force. The figure which shows the mode of the muscular strength which the driver | operator is exhibiting in the lane maintenance control of this invention. The figure which shows the mode of the muscular strength which the driver | operator is exhibiting in the conventional lane keeping control.

  FIG. 1 is a block diagram showing an example of a control system of the present invention mounted on a vehicle (automobile). In FIG. 1, U is a controller (control unit) configured using a microcomputer. The controller U has a storage means M, and stores various characteristic diagrams and the like used for executing the control described later in addition to the program necessary for the control.

  The controller U receives signals from various sensors and devices S1 to S6. S1 is a steering angle sensor that detects an operation amount of a steering wheel operated by a driver, that is, a steering angle (a steering angle including an operation direction). For example, S2 is a torque sensor that is attached to the steering shaft and detects the steering torque in accordance with the amount of twisting of the steering shaft.

  S3 is a camera that captures the front of the host vehicle, and is used to detect the left and right white line positions that divide the lane in which the host vehicle is traveling, and to detect the lateral position of the host vehicle with respect to the left and right white line positions. (It also detects the center position of the physical lane). S4 is a vehicle speed sensor that detects the vehicle speed. S5 is a navigation device for detecting the current position of the host vehicle and using the map information to detect the current road condition where the host vehicle is traveling, the road condition ahead, and the like. . S6 is a change-over switch that is manually operated by the driver to select ON (execution) and OFF (execution prohibition) of lane keeping control described later.

  The controller U controls the motor S11 and display means S12 such as a display or a lamp. The motor S11 is incorporated in the steering system and performs power assist. That is, in the embodiment, the power steering mechanism is an electric type in which an assist force is generated by the motor S11. The steering assist force is changed by adjusting (changing) the supply current. The display means S12 is for informing the driver of the ON / OFF state of the changeover switch S6.

  FIG. 2 schematically shows the relationship between the steering angle and the steering torque in accordance with the presence or absence of the lane keeping assist torque. With respect to the steering torque in the direction in which the steering angle increases at the same steering angle, FIG. Thus, the steering torque in the direction in which the steering angle decreases is set to be small, and the difference indicates the hysteresis width. The width of the hysteresis is set large when the lane keeping assist torque indicated by the broken line is not applied, and is set small when the lane keeping assist torque indicated by the solid line is applied. By varying the width of the hysteresis depending on the presence or absence of the lane keeping assist torque, it is possible to make the steering wheel feel almost the same with and without the lane keeping assist torque (physical Even if the amount of change in the steering torque is the same, the amount of change in the perceived steering torque closer to the driver is smaller when the physical steering torque is large than when it is small.

  Next, an example of determining the lane keeping assist torque for lane keeping will be described. First, in the embodiment, as shown in FIG. 3 in which the vehicle is running on the left curve, the target yaw rate calculation required for guiding to the guidance target point α that is the physical lane center position ahead of the host vehicle X is performed. Done. The distance in the forward direction of the host vehicle to the guidance target point α is defined as VT. In this case, V is the vehicle speed and T is the forward gaze time. The forward gaze time is set as a characteristic as shown in FIG. 4, for example, but the point is the target time until the guidance target point α is reached. Basically, the front gaze time T decreases as the vehicle speed increases. (Upper limit value and lower limit value are set).

  The target yaw rate Υtarget required for guiding to the guidance target point α is obtained by the following equation (1) based on the vehicle speed, the lateral position of the host vehicle, the yaw angle, the curvature of the lane, and the clothoid parameter. In equation (1), V is the vehicle speed, T is the forward gaze time, R is the curvature of the lane, Ψ0 is the yaw angle of the host vehicle X, y0 is the lateral position of the host vehicle X, and A is the clothoid parameter. The curvature R and the like can be determined based on the detection result of the camera S3. For example, the curvature R is obtained based on the map information in the navigation device S5 or information from the infrastructure facility set on the roadside. Can be obtained by an appropriate method. The yaw rate of the host vehicle can be detected by a dedicated yaw rate sensor provided separately.

  When the target yaw rate Υtarget is determined, the target yaw rate Υtarget and the vehicle speed are collated with the characteristics shown in FIG. 5, and the target steering torque TDriver to be exhibited by the driver is determined. Next, the steering angular velocity is checked against the characteristic diagram shown in FIG. 6 to determine the hysteresis width. Note that a dead zone is set for the hysteresis width in a region where the steering angular velocity is small (for example, 0.00001 rad / s or less) (steering rattling is prevented). This hysteresis width corresponds to the case where a reference value without the lane keeping assist torque is set. When the lane keeping assist torque is present, the hysteresis width decreases so as to reduce the hysteresis width as described with reference to FIG. It is corrected.

  In order to determine the final output for the power steering apparatus, the following steering torque is determined. First, the steering torque TNormal necessary for the turning described with reference to FIG. 3 is calculated. The standard assist torque corresponding to TDriver is determined as TESP as the steering torque to be exhibited by the driver described above (TESP can also be determined according to the torque detected by torque sensor S2). Then, the basic lane keeping assist torque TBase is calculated based on the following equation (2).

TBase = TNormal-TDriver-TESP (2)
The basic lane keeping assist torque TBase is additionally applied to the case where there is no lane keeping control. When the lane keeping assist torque TBase is applied, the hysteresis width is corrected to be smaller than when the lane keeping assist torque TBase is not applied.

  In addition to the above, the viscous torque TViscosity is determined. This viscous torque TViscosity is calculated by multiplying the steering angular velocity by a gain coefficient C (> 0). The gain count C is determined based on characteristics as shown in FIG. That is, the gain coefficient C is determined to be smaller as the absolute value of the deviation obtained by subtracting the current yaw rate of the host vehicle X from the target yaw rate described in FIG. Further, the gain coefficient C is determined so as to decrease as the vehicle speed increases even if the absolute value of the deviation is the same. Thus, the viscous torque TViscosity is determined so as to increase as the steering angular velocity increases, increase as the deviation (absolute value) decreases, and increase as the vehicle speed decreases.

  The viscosity torque TViscosity determined as described above is subtracted from the basic lane keeping assist torque TBase described above to obtain the final lane keeping assist torque TLKA, and this final lane keeping assist torque TLKA. Is output (TLKA output from the motor S11). In particular, when the absolute value of the deviation between the target yaw rate and the actual yaw rate is small, it is at the time of steering or almost at the time of steering. In this case, since the viscous torque TViscosity is set large, the final lane The maintenance assist torque TLKA is reduced and the steering wheel stability is improved (preventing or suppressing the function of the antagonistic muscle).

  FIG. 8 is a flowchart showing a control example for determining (outputting) the above-described final TLKA by the controller U. Hereinafter, this flowchart will be described, but it is assumed that the changeover switch S6 is ON (with lane keeping assist torque control−with viscous torque). In the following description, Q indicates a step. Of course, FIG. 2, FIG. 4, FIG. 6, FIG. 7, Formula (1), Formula (2), etc. are memorize | stored in the memory | storage means M. FIG.

  Based on the above, first, in Q1, signals from various sensors S1 to S6 are read. Next, at Q2, as described in FIG. 3, the target yaw rate Υtaeget is calculated. Thereafter, in Q3, a target steering torque TDriver to be exhibited by the driver is calculated based on FIG. Thereafter, in Q4, a steering torque TNormal necessary for turning for guiding to the guidance target point α in FIG. 3 is calculated.

  After Q4, in Q5, the standard assist torque TESP is calculated based on the target steering torque TDriver calculated in Q3. Thereafter, in Q6, the basic lane keeping assist torque TBase is calculated based on the equation (2). Thereafter, in Q7, the reference hysteresis width is determined based on FIG.

  After Q7, at Q8, the target viscosity torque TViscosity is determined (a gain coefficient C is determined based on FIG. 7, and the gain coefficient C is multiplied by the steering angular velocity). Thereafter, in Q9, the final lane keeping assist torque TLKA is determined by subtracting the viscous torque KTViscosity from the basic lane keeping assist torque TBase determined in Q6. In Q10, a control signal (drive signal) is output to the motor S11 so that the final lane keeping assist torque TLKA is obtained. When the final lane keeping assist torque TLKA is not 0, the reference hysteresis width is corrected to decrease.

  Next, control for reducing driver fatigue during turning will be described with reference to FIG. First, FIG. 9 shows an example of control for correcting the lane keeping assist torque in the lane keeping control described above, and is executed after the interrupt processing for the flowchart of FIG. 8 or the processing in Q6 (or Q9) of FIG. The

  In FIG. 9, the lateral G is detected at Q21. The detection of the lateral G may be directly detected by the lateral G sensor, but may be performed by an appropriate method such as detection (calculation) by calculation based on the steering angle and the vehicle speed. In Q22, it is determined whether or not the detected lateral G is equal to or greater than a predetermined value set in advance. The predetermined value is 0.2 G in the embodiment, and is a value corresponding to, for example, turning when a curve having a curvature radius of 300 m is turned at 100 km / h.

  When the determination in Q22 is YES, the gain G for calculating the lane keeping assist torque is gradually reduced from 1 as shown in FIG. 10 (with a lower limit setting). Accordingly, the lane keeping assist torque becomes a value smaller than the torque value required in the control of FIG. 8, and the steering force that the driver's confidence steers is increased accordingly. By suppressing the increase of the lane keeping assist torque in this way, the driver's fatigue during turning is reduced. This fatigue reduction will be described in detail later. When the determination in Q22 is NO, the gain G is set to 1 in Q23 (setting of the lane keeping assist torque as controlled in FIG. 8).

  Next, the driver's fatigue reduction point by suppressing the increase of the lane keeping assist torque will be described. 11 and 12, reference numeral 11 denotes a handle, 12 denotes a driver's seat cushion, and 13 denotes a driver's seat back. FIG. 11 shows a state where the driver 20 is operating the handle 11 to the left. At this time, in the conventional lane keeping control, as shown in FIG. 17, the muscular strength of the arm (triceps surae) is reduced, but the neck (left and right sternocleidomastoid muscle) and the right (outside of turning) The muscle strength of the quadriceps femoris muscle (specific portions thereof are not shown in FIG. 11) is greatly increased. More specifically, FIG. 17 shows a straight road traveling at a vehicle speed of 100 km / h, a curve entrance road changing from a radius of curvature of 1000 m to 300 m, a curve of a radius of curvature of 300 m, and a radius of curvature changing from 300 m to 1000 m. 11 shows how the muscular strength exerted by the muscle portion shown in FIG. 11 changes when traveling on a curved exit road. In FIG. 17, the broken line indicates the case without lane keeping control, and the solid line indicates the case with lane keeping control. Note that the muscular strength of the muscles other than those described above is almost the same between the cases with and without the lane keeping control.

  As is clear from FIG. 17, when running at a radius of curvature of 300 m and in the vicinity thereof, the muscle strength of the right upper triceps muscle is reduced, but the neck (left and right sternocleidomastoid muscles) and right (outside of turning) The muscle strength of the quadriceps is greatly increased, which causes fatigue. In this way, the muscle strength of the neck (left and right sternocleidomastoid muscles) and the right (outside of turning) quadriceps is greatly increased. This is because the inclination of the neck accompanying this is attempted to be suppressed (countered) by the muscle having increased muscular strength.

  FIG. 16 corresponds to FIG. 17. When the lateral G is a predetermined value (0.2 G in the embodiment) or more, it corresponds to the control when the increase of the lane keeping assist torque is suppressed (FIG. 16). 9 when control 9 is performed). As can be seen from FIG. 16, according to the lane keeping control according to the present invention, the neck (left and right sternocleidomastoid muscles) and the right (outside of turning) quadriceps are reduced while reducing the strength of the right upper triceps muscle. Muscle strength is hardly increased, resulting in reduced fatigue.

  Next, the reason for reducing fatigue by suppressing the increase in the assist torque for maintaining the lane will be described. Basically, the lateral frictional force between the driver 20 and the seat back 13 is a centrifugal force based on the lateral G. If it is equal to or greater than (lateral force), the seat back 13 can prevent the driver's upper body from moving outwardly, and the neck (left and right sternocleidomastoid muscles) and right (outwardly turning) thighs can be reduced accordingly. There is no need to increase the strength of the quadriceps.

  The lateral frictional force can be calculated as follows. First, as shown in FIG. 12, the steering torque of the steering wheel 11 by the driver 20 is T, and the other parameters are as shown in FIG. At this time, out of the load mg of the upper body of the driver 20, the force that the vertical acts on the seat back 13 is mg · sin θ1. Further, a component in which the reaction force of the steering force T of the steering wheel acts perpendicularly to the seat back 13 through the arm of the driver 20 is F · cos θ2 (F = T · 3 / r). The lateral frictional force M between the driver 20 and the seat back 13 is expressed by the following equation.

M = μ (mg · sigθ1 + F · cosθ2)
If the lateral frictional force M is equal to or greater than the lateral force Y acting on the upper body of the driver 20, a situation in which the upper body of the driver is held by the seat back 13 and slides and moves outward is prevented. Will be. The lateral frictional force M increases as the steering torque T exerted by the driver 20 increases. Then, by suppressing the increase in the lane keeping assist torque, the steering torque T is increased accordingly, and the lateral friction force M is increased. As described above, in the present invention, the situation where the upper body of the driver 20 slips from the seat back 13 toward the outside in the turning direction is prevented or reduced, and the neck that worked to prevent this slipping movement accordingly. The muscular strength of the left and right sternocleidomastoid muscles and the right (rotating outside) quadriceps muscles will be reduced (reducing fatigue).

  FIG. 15 shows that when the steering torque T is less than 2.5 Nm, the lateral force Y becomes larger than the lateral friction force M, and it becomes difficult to maintain the posture of the driver 20. The reason for adopting 0.2 G as the lateral G size as a threshold value when suppressing the increase in the lane keeping assist torque is that the driver 20 is the standard physique, the driver seat is the standard position, the seat It is assumed that the skin of the back 13 is made of cloth, and the clothes on the upper body of the driver 20 are also made of cloth. Therefore, 0.2 G as the predetermined value is merely an example, and the size of the lateral G as the predetermined value can be changed according to the vehicle type or the like.

  Here, the increase suppression of the lane keeping assist torque when the lateral G becomes a predetermined value or more can be performed as follows. First, the lane keeping assist torque is maintained as it is when the lateral G reaches a predetermined value (a further increase in the lane keeping assist torque is regulated). Next, the lateral G when the lateral friction force M coincides with the lateral force Y is set as a predetermined value, and the lane keeping assist torque at this time is held. Of course, in addition to the above, an increase in the lane keeping assist torque can be suppressed by an appropriate method.

  Although the embodiments have been described above, the present invention is not limited to the embodiments, and appropriate modifications can be made within the scope of the claims. The power assist device is not limited to an electric type but may be a hydraulic type. In addition to using the camera S3, the position of the vehicle in the lateral direction relative to the lane can be detected by using another sensor such as a radar as an alternative or in cooperation, using a high-precision navigation device, It can be selected as appropriate, for example, by obtaining information from the infrastructure facility from the roadside by communication, or by combining them. As a parameter for determining the viscous torque, it is sufficient that at least the steering angular velocity is included, the deviation between the target yaw rate and the actual yaw rate and the vehicle speed may not be used as parameters, and in addition to the steering angular velocity, Either the deviation or the vehicle speed may be added as a parameter. The viscous torque is not limited to the continuously variable type, but may be changed stepwise. In addition, it is also possible to set so as not to use viscous torque. The hysteresis width may be always set to the same size. Of course, the object of the present invention is not limited to what is explicitly stated, but also implicitly includes providing what is substantially preferred or expressed as an advantage.

  The present invention is suitable as a vehicle lane keeping support system.

11: Handle 13: Seat back 20: Driver U: Controller (control means)
S1: Rudder angle sensor S2: Torque sensor S3: Camera S4: Vehicle speed sensor S5: Navigation device S6: Changeover switch (for ON / OFF of lane keeping control)
S11: Motor (for power assist)
M: Lateral friction force Y: Lateral force

Claims (4)

In the lane keeping assist system, the assist torque for maintaining the lane in the direction of preventing the own vehicle from deviating from the driving lane is applied in a size that can be overcome by the driver.
Lateral G detection means for detecting lateral G acting on the host vehicle;
When the lateral G detected by the lateral G detecting means is equal to or greater than a predetermined value set in advance , the lateral frictional force between the driver and the seat back acts on the driver based on the lateral G. As described above, assist torque correction means for suppressing an increase in the assist torque for maintaining the lane,
A lane keeping support system characterized by comprising: In claim 1,
The assist torque correcting means gradually decreases the gain amount for calculating the lane keeping assist torque according to the increase in the lateral G when the lateral G detected by the lateral G detecting means is equal to or greater than the predetermined value. Lane maintenance support system characterized by In claim 1,
The assist torque correcting means holds the lane keeping assist torque at the immediately preceding lane keeping assist torque when the lateral G detected by the lateral G detecting means is equal to or greater than the predetermined value. Support system. In claim 1,
Lane maintaining is characterized in that the lateral frictional force is determined on the basis of a load acting on the seat back due to the weight of the driver's upper body and a steering reaction force acting on the seat back through an arm gripping the steering wheel. Support system.

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