JP2018144661A - Deflection control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To give an appropriate yaw moment to a vehicle according to a tire characteristic. SOLUTION: A deflection control device (17) performs deflection control to deflect an own vehicle (1) by a difference in braking force between left and right wheels. The deflection control device has a vertical slip ratio during four-wheel braking in which braking force is applied to the left and right front wheels and left and right rear wheels of the own vehicle, or braking force on at least one of the left and right front wheels and rear wheels of the own wheel. Estimating means (172) for estimating the tire characteristics of the own vehicle based on the longitudinal slip ratio at the time of one-wheel braking, and control means (172) for performing deflection control based on the estimated tire characteristics. 173) and. [Selection diagram] Fig. 3

Description

  The present invention relates to a deflection control device that deflects a vehicle, and more particularly to a technical field of a deflection control device that deflects a vehicle using a braking force difference between left and right wheels.

  As this type of device, for example, when it is determined that the host vehicle is likely to deviate from the traveling lane, a device that generates a yaw moment in a direction to avoid the deviation based on the braking force difference between the left and right wheels has been proposed ( Patent Document 1).

JP 2006-282168 A

  Even if the difference in braking force between the left and right wheels when a yaw moment in a direction to avoid the deviation is applied to the vehicle, the yaw rate generated in the vehicle changes depending on the tire characteristics. In particular, since the tire can be arbitrarily changed by the user of the vehicle, as in the technique described in Patent Document 1, if a deviation is to be avoided due to a difference in braking force between the left and right wheels, depending on the characteristics of the tire, a yaw rate higher than expected can be obtained. May occur in the vehicle, and the vehicle behavior may become unstable.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a deflection control device capable of imparting an appropriate yaw moment according to tire characteristics to a vehicle.

  In order to solve the above-described problem, the deflection control device of the present invention is a deflection control device that performs deflection control for deflecting the host vehicle due to a difference in braking force between the left and right wheels, the left and right front wheels and the left and right rear wheels of the host vehicle. Based on a vertical slip ratio during four-wheel braking in which braking force is applied to the vehicle, or a vertical slip ratio during single-wheel braking in which braking force is applied to at least one of the left and right front wheels and rear wheels of the own wheel. And estimating means for estimating the tire characteristics of the host vehicle, and control means for performing the deflection control based on the estimated tire characteristics.

  In the deflection control device, tire characteristics are estimated, and deflection control based on the estimated tire characteristics is performed. Therefore, according to the deflection control apparatus, an appropriate yaw moment according to the tire characteristics can be given to the vehicle by the deflection control. For the relationship between the vertical slip ratio and the tire characteristics, refer to the embodiments described later.

  The effect | action and other gain of this invention are clarified from the form for implementing demonstrated below.

1 is a block diagram illustrating a configuration of a vehicle 1 according to an embodiment. It is a flowchart which shows the lane departure suppression operation | movement which concerns on embodiment. It is a flowchart which shows the deviation avoidance control which concerns on embodiment. It is a flowchart which shows the acquisition operation | movement of the tire state at the time of four-wheel braking which concerns on embodiment. (A) is a figure which shows an example of the relationship between a vertical slip ratio and braking hydraulic pressure. (B) is a figure which shows an example of the relationship between a characteristic value and cornering power. It is a flowchart which shows the acquisition operation | movement of the tire state at the time of the steering which concerns on embodiment. It is a figure which shows an example of the relationship between cornering power in case a yaw moment is constant, and a yaw rate. It is a flowchart which shows the deviation avoidance control which concerns on the 3rd modification of embodiment.

  An embodiment according to a deflection control apparatus of the present invention will be described with reference to FIGS. In the following embodiments, the description will be given using a vehicle equipped with the deflection control device of the present invention.

(Vehicle configuration)
First, the configuration of the vehicle 1 on which the deflection control device according to the embodiment is mounted will be described with reference to FIG. FIG. 1 is a block diagram illustrating a configuration of a vehicle 1 according to the embodiment.

  In FIG. 1, a vehicle 1 includes a brake pedal 111, a master cylinder 112, a brake actuator 13, a wheel cylinder 122FL disposed on a left front wheel 121FL, a wheel cylinder 122FR disposed on a left rear wheel 121RL, A wheel cylinder 122RL disposed on the right front wheel 121FR, a wheel cylinder 122RR disposed on the right rear wheel 121RR, and brake pipes 113FL, 113RL, 113FR, and 113RR are provided.

  The vehicle 1 further includes a steering wheel 141, a vibration actuator 142, a vehicle speed sensor 151, a wheel speed sensor 152, a yaw rate sensor 153, an acceleration sensor 154, a camera 155, a display 16, and a “deflection control device”. ECU (Electronic Control Unit) 17, which is a specific example of the above.

  The master cylinder 112 adjusts the pressure of the brake fluid (or any fluid) in the master cylinder 112 according to the depression amount of the brake pedal 111. The pressure of the brake fluid in the master cylinder 112 is transmitted to the wheel cylinders 122FL, 122RL, 122FR, and 122RR through the brake pipes 113FL, 113RL, 113FR, and 113RR, respectively. As a result, braking force corresponding to the pressure of the brake fluid transmitted to the wheel cylinders 122FL, 122RL, 122FR, and 122RR is applied to the left front wheel 121FL, the left rear wheel 121RL, the right front wheel 121FR, and the right rear wheel 121RR, respectively. .

  The brake actuator 13 can adjust the pressure of the brake fluid transmitted to each of the wheel cylinders 122FL, 122RL, 122FR, and 122RR regardless of the depression amount of the brake pedal 111 under the control of the ECU 17. Therefore, the brake actuator 13 can adjust the braking force applied to each of the left front wheel 121FL, the left rear wheel 121RL, the right front wheel 121FR, and the right rear wheel 121RR regardless of the depression amount of the brake pedal 111.

  The steering wheel 141 is an operator that is operated by a driver to steer the vehicle 1 (that is, to snake the snake wheel). The vibration actuator 142 can vibrate the steering wheel 141 under the control of the ECU 17.

  The ECU 17 controls the overall operation of the vehicle 1. Particularly in the present embodiment, the ECU 17 performs a lane departure suppression operation for suppressing the departure of the vehicle 1 from the currently traveling lane. That is, the ECU 17 functions as a control device for realizing so-called LDA (Lane Departure Alert) or LDP (Lane Departure Prevention).

  In order to perform the lane departure restraining operation, the ECU 17 includes a data acquisition unit 171, an LDA control unit 172, and a brake control unit 173 as processing blocks logically realized therein or as processing circuits physically realized. I have.

(Lane departure control operation)
Next, the lane departure restraining operation according to the present embodiment will be described with reference to the flowchart of FIG.

  In FIG. 2, first, the data acquisition unit 171 acquires detection data indicating detection results of the vehicle speed sensor 151, the wheel speed sensor 152, the yaw rate sensor 153, and the acceleration sensor 154, and image data indicating an image captured by the camera 155. (Step S101).

  The LDA control unit 172 analyzes the image data acquired in the process of step S101, thereby generating a lane end of the traveling lane in which the vehicle 1 is currently traveling (in this embodiment, “white line” is used as an example of the lane end). Are specified in the image captured by the camera 155 (step S102). Note that since the existing technology can be applied to the white line recognition method, the detailed description thereof is omitted.

  The LDA control unit 172 determines whether the traveling lane in which the vehicle 1 is currently traveling is a straight road or a curved road based on the white line specified in the process of step S102, and determines that it is a curved road. If so, the radius of curvature of the travel lane is calculated (step S103). The radius of curvature of the traveling lane is substantially equivalent to the radius of curvature of the white line. For this reason, the LDA control unit 172 may calculate the radius of curvature of the white line specified in the process of step S102 and handle the calculated radius of curvature as the radius of curvature of the traveling lane.

  The LDA control unit 172 further calculates the current lateral position, lateral speed, and departure angle of the vehicle 1 based on the white line specified in the process of step S102 (step S104). Here, the “lateral position” is a distance from the center of the traveling lane to the vehicle 1 (typically the center of the vehicle 1) along the lane width direction orthogonal to the direction in which the traveling lane extends (lane extending direction). Distance). “Lateral speed” means the speed of the vehicle 1 along the lane width direction. The “deviation angle” means an angle formed by the travel lane and the longitudinal axis of the vehicle 1 (that is, an angle formed by the white line and the longitudinal axis of the vehicle 1).

  The LDA control unit 172 further sets an allowable deviation distance (step S105). The allowable deviation distance indicates an allowable maximum value of the deviation distance of the vehicle 1 from the traveling lane (that is, the deviation distance of the vehicle 1 from the white line) when the vehicle 1 deviates from the traveling lane.

  For example, the allowable deviation distance may be set as follows. In other words, the LDA control unit 172 may set the allowable deviation distance from the viewpoint of satisfying a request for regulations and the like (for example, a request for NCAP: New Car Assessment Program). Note that the method of setting the allowable deviation distance is not limited to this.

  Thereafter, the LDA control unit 172 determines whether or not the vehicle 1 may deviate from the currently traveling lane (step S106). Specifically, for example, the LDA control unit 172 calculates the future position of the vehicle 1 (for example, after several seconds to several tens of seconds) based on the current speed, lateral position, lateral speed, and the like of the vehicle 1. Then, the LDA control unit 172 determines whether or not the vehicle 1 straddles or steps on the white line at a future position. When it is determined that the vehicle 1 straddles or steps on the white line at a future position, the LDA control unit 172 determines that the vehicle 1 may deviate from the travel lane.

  When it is determined in step S106 that there is no possibility that the vehicle 1 deviates from the travel lane (step S106: No), the lane departure suppression operation shown in FIG. 2 is terminated. Thereafter, the LDA control unit 172 starts the lane departure suppression operation shown in FIG. 2 again after a predetermined period (for example, several milliseconds to several tens of milliseconds) has elapsed. That is, the lane departure suppression operation shown in FIG. 2 is repeatedly performed at a period corresponding to a predetermined period.

  On the other hand, when it is determined in step S106 that the vehicle 1 may deviate from the travel lane (step S106: Yes), the LDA control unit 172 may cause the vehicle 1 to deviate from the travel lane. A warning is given to the driver of the vehicle 1 (step S107). Specifically, the LDA control unit 172 controls the display 16 so as to display, for example, an image indicating that the vehicle 1 may deviate from the traveling lane, and / or the vehicle 1 moves from the traveling lane. The vibration actuator 142 is controlled so that the driver may be notified by vibration of the steering wheel 141 that there is a possibility of deviation.

  In parallel with the processing in step S107, the LDA control unit 172 performs departure avoidance control (step S2). Here, the departure avoidance control is control for giving the vehicle 1 a yaw moment in a direction to avoid the departure so that the departure distance of the vehicle 1 from the traveling lane is within the allowable departure distance.

  In the departure avoidance control according to the present embodiment, a braking force is applied to at least one of the left front wheel 121FL, the left rear wheel 121RL, the right front wheel 121FR, and the right rear wheel 121RR so that a braking force difference between the left and right wheels is generated. As a result, the vehicle 1 is given a yaw moment in a direction to avoid the departure. Hereinafter, the departure avoidance control will be specifically described with reference to the flowchart of FIG.

3. Deviation avoidance control In FIG. 3, first, the LDA control unit 172 follows a target track (that is, a target travel line) in which the vehicle 1 traveling away from the center of the travel lane is directed toward the center of the travel lane. The target yaw rate (Yr) is calculated so as to travel (step S201).

  After step S201, the LDA control unit 172 acquires the tire state of the vehicle 1 (step S202). In the present embodiment, “cornering power” is given as an example of the tire condition. A method for specifying the tire condition will be described later.

Next, the LDA control unit 172 corrects the conversion formula for converting the yaw rate into the yaw moment (Mz) based on the cornering power as the tire state (step S203). In the present embodiment, the following formula (1) and formula (2) are given as examples of the conversion formula. Therefore, the LDA control unit 172 corrects the values of the parameters “A ₁ ” and “A ₂ ” based on the cornering power in the process of step S203.

Expression (2) is an approximate expression when the condition “A2 / v >> mv” is satisfied in Expression (1). In the equations (1) and (2), “θ”, “Mz”, “m”, “v”, “C _f ”, “C _r ”, “l _f ”, and “l _r ” are respectively "Yaw angle", "Yaw moment", "Vehicle mass", "Vehicle 1 speed", "Front wheel cornering power", "Rear wheel cornering power", "Center of gravity-front wheel axle distance" and "Center of gravity-rear wheel axle" Distance ".

Next, the LDA control unit 172 calculates a target yaw moment from the target yaw rate using the equation (1) or the equation (2) (step S204). Subsequently, the LDA control unit 172 calculates a braking force that can achieve the target yaw moment. At this time, the LDA control unit 172 individually calculates the braking force applied to each of the left front wheel 121FL, the left rear wheel 121RL, the right front wheel 121FR, and the right rear wheel 121RR.

  The LDA control unit 172 transmits a signal indicating the calculated braking force to the brake control unit 173.

  The brake control unit 173 calculates a pressure command value that specifies the pressure of the brake fluid necessary for generating the braking force on the condition that the signal indicating the braking force is received from the LDA control unit 172 (step S205). ). At this time, the brake control unit 173 individually calculates a pressure command value that designates the pressure of the brake fluid in each of the wheel cylinders 122FL, 122RL, 122FR, and 122RR.

  Next, the brake control unit 173 controls the brake actuator 13 based on the pressure command value (step S206). As a result, a braking force corresponding to the pressure command value is applied to at least one of the left front wheel 121FL, the left rear wheel 121RL, the right front wheel 121FR, and the right rear wheel 121RR. That is, a yaw moment in a direction to avoid the departure is applied to the vehicle 1 due to a difference in braking force between the left and right wheels.

(Tire condition acquisition operation)
Next, an operation for acquiring a tire state (here, cornering power) according to the present embodiment will be described. The LDA control unit 172 obtains the cornering power obtained in any of the following “at the time of four-wheel braking”, “at the time of one-wheel braking”, and “at the time of steering” in the process of step S202 described above.

Regarding the operation of acquiring cornering power during four-wheel braking of the vehicle 1 during four-wheel braking (that is, when braking force is applied to all of the left front wheel 121FL, the left rear wheel 121RL, the right front wheel 121FR, and the right rear wheel 121RR) This will be described with reference to the flowchart of FIG.

  In FIG. 4, the LDA control unit 172 acquires the initial vehicle body speed (that is, the vehicle body speed before braking) from the detection result of the wheel speed sensor 152 via the data acquisition unit 171 (step S301). Next, the LDA control unit 172 acquires the longitudinal acceleration Gx and / or the pressure of the brake fluid in the master cylinder 112 and / or the control braking force and / or driving force during braking (step S302). .

  Next, the LDA control unit 172 calculates the vehicle body speed of the vehicle 1 after the elapse of time t from the start of braking (step S303). For example, when the longitudinal acceleration Gx is used, the vehicle body speed is calculated by the following formula. In the following equations, “Vx (t)” and “Vx (0)” respectively represent “vehicle speed after time t has elapsed since the start of braking” and “initial vehicle speed”.

In parallel with the processing in step S303, the LDA control unit 172 determines the left front wheel 121FL, the left rear wheel 121RL, the right front wheel 121FR, and the right rear wheel 121RR from the detection result of the wheel speed sensor 152 via the data acquisition unit 171. Each wheel speed N _i (i = FL, RL, FR, RR) is acquired (step S304).

Next, based on the wheel speed N _i , the LDA control unit 172 calculates the estimated vertical slip ratio S _i (i = FL) of the left front wheel 121FL, the left rear wheel 121RL, the right front wheel 121FR, and the right rear wheel 121RR by the following formula. , RL, FR, RR) are calculated (step S305).

Next, the LDA control unit 172 calculates a tire characteristic value K _xi (i = FL, RL, FR, RR) from the estimated vertical slip ratio S _i and the braking / driving force (step S306). Here, FIG. 5A shows an example of the relationship between the vertical slip ratio and the braking hydraulic pressure (or longitudinal acceleration or driving force). As shown in FIG. 5A, the straight line indicating the summer tire and the straight line indicating the studless tire are clearly different in inclination (that is, the angle formed by the straight line and the horizontal axis). For this reason, in this embodiment, the inclination of the straight line is used as the tire characteristic value. In the process of step S306, the LDA control unit 172 obtains the slope of the straight line connecting the point indicated by the estimated vertical slip rate S _i and the braking / driving force and the coordinate origin as the characteristic value K _xi .

Next, the LDA control unit 172 calculates the cornering power Cp from the characteristic value K _xi based on a map that defines the relationship between the characteristic value and the cornering power, for example, as shown in FIG. 5B (step S307). ).

The cornering power acquisition operation during single-wheel braking of the vehicle 1 during single-wheel braking (for example, when the above-described departure avoidance control is performed) will be described with reference to the flowchart of FIG. In FIG. 6, the same processes as those shown in FIG. 4 are denoted by the same reference numerals.

In FIG. 6, the LDA control unit 172 acquires the longitudinal acceleration Gx and / or the pressure of the brake fluid in the master cylinder 112 and / or the control braking force and / or the driving force during one-wheel braking ( Step S302). Next, the LDA control unit 172 determines the wheel speed N _i (the left wheel 121FL, the left rear wheel 121RL, the right front wheel 121FR, and the right rear wheel 121RR) from the detection result of the wheel speed sensor 152 via the data acquisition unit 171. i = FL, RL, FR, RR) is acquired (step S304).

Next, based on the wheel speed N _i , the LDA controller 172 estimates the estimated vertical slip ratios S _i (i = FL, RL, FR) of the left front wheel 121FL, the left rear wheel 121RL, the right front wheel 121FR, and the right rear wheel 121RR. , RR) is calculated (step S305). Next, the LDA control unit 172 calculates a tire characteristic value K _xi (i = FL, RL, FR, RR) from the estimated vertical slip ratio S _i and the braking / driving force (step S306). Next, the LDA control unit 172 calculates the cornering power Cp from the characteristic value _Kxi based on a map that defines the relationship between the characteristic value and the cornering power (step S307).

An operation for obtaining cornering power when the vehicle 1 is steered will be described. The LDA control unit 172 acquires the vehicle state (for example, vehicle body speed, steering angle, yaw rate, etc.) when the vehicle 1 is steered. The LDA control unit 172 calculates the cornering power by solving the following simultaneous equations based on the acquired vehicle state. In the following formula, “Vx”, “δ”, “Yr”, “l”, “m”, “C _f ”, “C _r ”, “l _f ”, and “l _r ” are respectively “vehicle speed”. ”,“ Rudder angle ”,“ Yaw rate ”,“ Wheelbase ”,“ Vehicle mass ”,“ Front wheel cornering power ”,“ Rear wheel cornering power ”,“ Center of gravity-front wheel axle distance ”, and“ Center of gravity—rear wheel axle ” "Distance".

(Technical features)
FIG. 7 shows the relationship between the cornering power and the yaw rate when the yaw moment (that is, the braking force difference between the left and right wheels) applied to the vehicle is constant. As can be seen from FIG. 7, even if the yaw moment applied to the vehicle is constant, the yaw rate generated in the vehicle differs if the cornering power (that is, the tire characteristics) is different.

  In the present embodiment, the equation for converting the target yaw rate into the target yaw moment is corrected based on the cornering power. Therefore, according to the present embodiment, when the vehicle 1 may deviate from the travel lane, an appropriate yaw moment according to the tire characteristics is applied to the vehicle 1 so that the vehicle 1 deviates from the travel lane. Can be suppressed.

  The “LDA control unit 172” according to the embodiment is an example of the “estimating unit” according to the present invention. The “LDA control unit 172” and the “brake control unit 173” according to the embodiment are examples of the “control unit” according to the present invention.

<First Modification>
In the above-described embodiment, the values of the parameters “A1” and “A2” in the formula (1) or the formula (2) are corrected (ie, recalculated) based on the cornering power in the process of step S203. Thus, the target yaw moment is obtained from the target yaw rate by the equation (1) or the equation (2).

  Instead of modifying the values of the parameters “A1” and “A2”, the values of the parameters “A1” and “A2” obtained based on the cornering power as a reference are not changed, and the cornering power is changed. Expression (1) or Expression (2) may be modified by applying a coefficient according to the amount of change from the cornering power as a reference to Expression (1) or Expression (2). In this case, a coefficient that increases the target yaw moment as the cornering power becomes larger than the reference cornering power is applied to the expression (1) or (2). On the other hand, a coefficient that reduces the target yaw moment as the cornering power becomes smaller than the reference cornering power is applied to the equation (1) or (2).

<Second Modification>
In the above-described embodiment, formula (1) or formula (2) is corrected in the process of step S203, but the process of step S203 may not be performed. In this case, the target yaw moment obtained in the process of step S204 is corrected according to the amount of change from the cornering power that is the reference for the cornering power. Specifically, the target yaw moment is corrected so that the target yaw moment increases as the cornering power becomes larger than the reference cornering power. On the other hand, the target yaw moment is corrected so that the target yaw moment becomes smaller as the cornering power becomes smaller than the reference cornering power.

<Third Modification>
Deviation avoidance control according to the third modification will be described with reference to the flowchart of FIG. In this modification, after the cornering power as the tire state is acquired in the process of step S202, the LDA control unit 172 determines whether or not the cornering power is equal to or greater than a predetermined value (step S401). In this determination, when it is determined that the cornering power is less than the predetermined value (step S401: No), the LDA control unit 172 performs the processing after step S204.

  On the other hand, if it is determined in step S401 that the cornering power is equal to or greater than the predetermined value (step S401: Yes), the LDA control unit 172 prohibits the execution of the departure avoidance control using the braking force difference between the left and right wheels. (Step S402).

  If comprised in this way, it can prevent that a vehicle behavior becomes unstable resulting from the departure avoidance control using the braking force difference of a right-and-left wheel. In this case, departure avoidance control using an electric power steering system (not shown) may be performed.

  The “predetermined value” is a value that determines whether or not the departure avoidance control using the braking force difference between the left and right wheels is prohibited, and is set in advance as a fixed value or a variable value according to some physical quantity or parameter. The “predetermined value” is, for example, a relationship between the cornering power and the yaw rate generated in the vehicle 1, and based on the determined relationship, a yaw rate at which a vehicle stability control device such as a VSC (Vehicle Stability Control) is operated. What is necessary is just to set as corresponding cornering power.

  The present invention is not limited to the above-described embodiment, and can be appropriately changed without departing from the gist or concept of the invention that can be read from the claims and the entire specification, and the deflection control device with such a change. Is also included in the technical scope of the present invention.

  DESCRIPTION OF SYMBOLS 1 ... Vehicle, 13 ... Brake actuator, 17 ... ECU, 171 ... Data acquisition part, 172 ... LDA control part, 173 ... Brake control part

Claims (1)

A deflection control device that performs deflection control for deflecting the host vehicle due to a braking force difference between left and right wheels,
Vertical slip ratio during four-wheel braking in which braking force is applied to the left and right front wheels and left and right rear wheels of the host vehicle, or a piece in which braking force is applied to at least one of the left and right front wheels and rear wheels of the host vehicle Estimating means for estimating tire characteristics of the host vehicle based on a vertical slip rate during wheel braking;
Control means for performing the deflection control based on the estimated tire characteristics;
A deflection control device comprising: