Vehicle control device

Abstract

To provide a vehicle control device that can execute an appropriate VSC even when unexpected vibration occurs due to an earthquake or the like.SOLUTION: A vehicle control device is configured to perform stability control in which a brake control device is controlled to prevent the occurence of side slip on a wheel when the amount of change of a yaw rate is larger than a predetermined operation threshold value. If an earthquake has occurred (YES in step S2), a controller narrows the operation threshold value (step S6) and if at least one of the conditions is satisfied at the time of occurrence of the earthquake (YES in step S2) that a braking operation amount is larger than a braking determination threshold value (NO in step S3) and that a steering determination value is larger than a steering determination threshold value (NO in step S5), does not preform control of narrowing the operation threshold value (step S7)SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a vehicle control device that performs vehicle stability control (VSC). [Background technology]

[0002] Patent Document 1 discloses a vehicle driving control device that changes the characteristics of a vehicle behavior control device, including a skid prevention device, to improve behavior stability when overtaking is expected to become unstable due to factors such as the road surface, and performs overtaking. In the device of Patent Document 1, when there is information that suppresses overtaking, the deviation between the actual yaw rate and the target yaw rate, which is the threshold value for activating the skid prevention device, is changed to a small value to make it easier to activate the skid prevention device, and also changes it so that a large braking force is applied. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-002978 A Summary of the Invention [Problem to be solved by the invention]

[0004] Patent Document 1 describes that when overtaking is performed in the presence of overtaking suppression information, the vehicle behavior is stabilized by making the anti-skid device easier to operate. On the other hand, when an unexpected tremor occurs due to an earthquake or the like during overtaking control, the driver may operate the steering wheel relatively greatly to avoid an obstacle. In that case, the anti-skid device applies a braking torque to the wheels on the opposite side to the vehicle's traveling direction to prevent the vehicle from spinning. The anti-skid device of Patent Document 1 is easier to operate during overtaking control, so the braking torque applied early acts to hinder the avoidance of obstacles, etc. In other words, with the device of Patent Document 1, there was a possibility that the vehicle behavior would not be as intended by the driver when an earthquake or the like occurred.

[0005] The present invention has been made in consideration of the above-mentioned technical problems, and aims to provide a vehicle control device that is capable of executing appropriate stability control even when the vehicle experiences unexpected shaking due to an earthquake or the like. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, the present invention provides a vehicle control device comprising a brake device which generates a braking force on a vehicle when a driver operates a brake operating unit, and a steering wheel which is operated by the driver to adjust the direction of travel of the vehicle, and which performs stability control by controlling the brake device to suppress lateral skid of the wheels when an amount of change in yaw rate is greater than a predetermined activation threshold, the vehicle control device including a controller which controls the execution of the stability control, the controller having an earthquake determination unit which detects the occurrence of an earthquake, a braking determination unit which determines that the braking operation amount of the brake operating unit is greater than a predetermined braking determination threshold when the earthquake occurs, and a steering determination unit which determines that a steering determination value based on the steering amount of the steering wheel is greater than a predetermined steering determination threshold when the earthquake occurs, the controller being configured to narrow the activation threshold when the earthquake occurs, and not to perform control to narrow the activation threshold when at least one of the following is true: the braking operation amount is greater than the braking determination threshold and the steering determination value is greater than the steering determination threshold when the earthquake occurs. Effect of the Invention

[0007] According to the vehicle control device of the present invention, when an earthquake occurs, the threshold value for activating the vehicle stability control (VSC) is set to a small value, so that the VSC is activated early. When an earthquake occurs, the vehicle behavior becomes unstable due to unexpected shaking, so the VSC can be activated relatively early to suppress the deterioration of the vehicle stability. In addition, when the driver performs a relatively large braking operation or steering operation, the VSC activation threshold is maintained. In such a case, the driver may be trying to immediately stop the vehicle or avoid an obstacle, so that the VSC can be activated early to suppress the hindrance of these operations. Therefore, the VSC can be activated appropriately according to the vehicle behavior and the driver's operating state, and the vehicle behavior can be further stabilized. [Brief description of the drawings]

[0008] [Figure 1] 1 is a diagram showing a vehicle equipped with a control device according to an embodiment of the present invention. [Diagram 2] 4 is a flowchart showing an example of control executed by a control device in the embodiment of the present invention. [Diagram 3] 6 is a flowchart showing another example of control executed by the control device in the embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] A vehicle in an embodiment of the present invention is a vehicle capable of vehicle stability control (VSC) that controls the brake devices provided on each wheel so as to suppress skidding that occurs when the vehicle travels around a curve or when the driver suddenly operates the steering wheel. Fig. 1 shows a vehicle Ve configured in this manner. As shown in Fig. 1, the vehicle Ve includes a driving force source 1, a brake device 2, wheels 3, a steering device 4, an ECU (electronic control unit) 5, and a detection unit 6. The driving force source 1 is a conventionally known engine, motor generator, or the like, and outputs a torque for generating a driving force for the vehicle Ve.

[0010] The brake device 2 is a device similar to a conventionally known brake device, and is provided on each of the front and rear wheels 3 of the vehicle Ve. The brake device 2 is, for example, a friction brake such as a disk brake, drum brake, or powder brake, and is configured to generate frictional force by hydraulic pressure or electromagnetic force to generate a braking force in a direction to stop the rotation of each wheel 3. The brake device 2 outputs a braking torque not only when the driver operates a brake pedal (brake operation unit) 2a, but also when a VSC actuator (not shown) is activated. The VSC actuator is provided, for example, on a hydraulic path of brake oil, and when the amount of change in the yaw rate of the vehicle Ve is greater than a predetermined threshold, it individually controls the braking torque applied to each wheel 3 so as to improve the stability of the vehicle Ve.

[0011] The steering device 4 adjusts the traveling direction of the vehicle Ve by the driver operating the steering wheel 4a. This steering device 4 is the same as a conventionally known steering device 4, for example, a rack-and-pinion type steering device 4 provided with an electric power steering device (EPS).

[0012] The ECU 5 corresponds to the "controller" in the embodiment of the present invention and is mainly composed of, for example, a microcomputer, and is configured to perform calculations using data input from the detection unit 6 and pre-stored data, and to output a control command signal based on the calculation results. The input data includes, for example, the wheel speed, the acceleration of the vehicle Ve, the steering angle of the steering wheel 4a, the yaw rate, and the oil pressure to the brake device 2. The ECU 5 also includes a VSC-ECU 5a, a braking determination unit 5b, a steering determination unit 5c, and an earthquake determination unit 5d.

[0013] The VSC-ECU 5a acquires the acceleration, yaw rate, and steering angle of the vehicle Ve, and performs control to stabilize the behavior of the vehicle Ve. Based on the acquired data related to the behavior of the vehicle Ve, the VSC-ECU 5a operates the above-mentioned VSC actuator to control the wheels 3 to be controlled so as to output a braking torque according to the situation.

[0014] The braking determination unit 5b determines whether the braking operation amount B of the vehicle Ve based on the braking operation such as depressing the brake pedal 2a by the driver is greater than a predetermined braking determination threshold value Thb. The braking determination unit 5b obtains the braking operation amount B based on the braking operation, for example, by detecting the hydraulic pressure acting on the master cylinder with a sensor or detecting the stroke amount (depression amount) of the brake pedal 2a. The braking determination threshold value Thb is determined based on the maximum value of the braking force of the wheels 3 with respect to the brake hydraulic pressure, for example. In the VSC, the yaw angle of the vehicle Ve is controlled by the magnitude of the braking torque applied to each of the left and right wheels 3 to prevent spinning, etc. On the other hand, the maximum value of the braking force of the wheels 3 with respect to the brake hydraulic pressure or the slip rate of the wheels 3 is determined. Therefore, in the VSC, when the braking force of the wheels 3 is at its maximum, the braking torque applied to either of the left and right wheels 3 is reduced to control the yaw angle of the vehicle Ve. However, in that case, the total braking force of the wheels 3 is reduced, so that the deceleration of the vehicle Ve is reduced. Therefore, the braking determination threshold Thb is set to a value that allows the VSC to determine that such an event may occur. The braking determination threshold Thb may be set to a value that allows the driver to determine that the braking operation is intended to immediately stop the vehicle Ve or to significantly decelerate the vehicle Ve. Such a predetermined braking operation amount B may be determined in advance by experiments or the like, or may be determined based on data such as the driver's brake operation tendencies and habits.

[0015] The steering determination unit 5c determines that the steering determination value S based on the steering angle and steering speed of the steering wheel 4a by the driver is greater than a predetermined steering determination threshold value Ths. In the steering determination unit 5c, for example, the steering angle sensor 6f detects the steering angle and steering speed of the steering wheel 4a to obtain the steering determination value S. The steering determination value S may be obtained by detecting the stroke (steering rack stroke) of the rack that converts the rotational motion of the pinion gear in the steering device 4 into linear motion, or by detecting the rotational angle of the assist motor of the EPS. The steering determination threshold value Ths is set so that it can be determined that the driver is trying to avoid an obstacle or the like. When avoiding an obstacle or the like, the steering amount and steering speed become large, so that the vehicle Ve is likely to slip sideways. In that case, in the VSC, a relatively large braking torque is applied to the wheels 3 on the opposite side to the traveling direction so that the vehicle Ve does not spin. On the other hand, by controlling the braking torque in this way, the behavior of the vehicle Ve in response to the driver's operation may not be the behavior intended by the driver. Therefore, the steering determination threshold Ths is set to a value that allows the VSC to determine the possibility of such an event occurring. Such a steering determination threshold Ths may be determined in advance through experiments or the like, or may be determined based on data such as the driver's steering operation tendencies and habits.

[0016] The earthquake determination unit 5d determines the occurrence of an earthquake based on data acquired by the detection unit 6, notifications from the outside, etc. This determination of the occurrence of an earthquake may be performed by a conventionally known control, such as a case where an emergency earthquake warning is acquired by an emergency earthquake warning receiver (not shown), a control disclosed in Japanese Patent Application Laid-Open No. 2014-153750 that determines the occurrence of an earthquake based on a change in acceleration of the vehicle Ve and its duration, or a control disclosed in Japanese Patent Application Laid-Open No. 2008-224353 that determines the occurrence of an earthquake based on the difference between the amount of movement and attitude of the vehicle Ve based on an image captured by an on-board camera and the amount of movement and attitude of the vehicle Ve based on a sensor of the vehicle Ve.

[0017] The detection unit 6 is a device or apparatus for acquiring various data and information required for controlling the vehicle Ve. The detection unit 6 includes a wheel speed sensor 6a for detecting the wheel speed of each wheel 3, a vehicle speed sensor 6b for detecting the vehicle speed from the rotation speed of the wheels 3, a yaw rate sensor 6c for detecting the rate of change in the yaw angle of the vehicle Ve, an acceleration sensor 6d for detecting the acceleration of the vehicle Ve, a master cylinder pressure sensor 6e for detecting the hydraulic pressure acting on the master cylinder of the brake device 2, and a steering angle sensor 6f for detecting the steering angle of the steering wheel 4a. The detection unit 6, the ECU 5, and each actuator and sensor configured as described above are electrically connected to each other by, for example, a CAN or a wire harness, and output an electric signal corresponding to the detected value or the calculated value to the ECU 5 as detection data.

[0018] Next, the conditions under which the VSC operates will be described. The VSC-ECU 4a acquires the vehicle speed Vx based on the wheel speed of each wheel 3, the lateral acceleration Gy of the vehicle, the actual steering angle θ of the front wheels 3, and the actual yaw rate Yr. The reference yaw rate Yr_std is calculated by the following formula (1) that includes the stability factor Kh, steering gear ratio n, and wheelbase L, all of which are constants, in addition to these values. The actual steering angle θ is set to a positive value when the vehicle is steered to the left, and to a negative value when the vehicle is steered to the right. Yr_std=(Vx·θ / n·L)-Kh·Gy·Vx …(1)

[0019] A yaw rate deviation ΔYr is calculated, which is the difference between the reference yaw rate Yr_std calculated in this way and the detected actual yaw rate Yr, by performing a predetermined filter process on the reference yaw rate Yr_std.Then, the absolute value of the yaw rate deviation ΔYr is compared with a predetermined VSC start threshold (operation threshold) Th for determining the start of VSC, and if the absolute value of the yaw rate deviation ΔYr is large, VSC is started.

[0020] An example of a flowchart executed by the ECU 5 of the vehicle Ve configured as above is shown in Figure 2. First, in this flowchart, as shown in Figure 2, control is performed to determine the occurrence of an earthquake in step S1. As described above, the occurrence of an earthquake is determined by receiving an emergency earthquake warning, changes in acceleration in the lateral (front-back, left-right) and vertical directions of the vehicle Ve, image processing of an on-board camera, etc.

[0021] In step S1, when the control for determining the occurrence of an earthquake is executed, the process proceeds to step S2, where it is determined whether or not an earthquake has actually occurred. The occurrence of an earthquake here means, for example, that the seismic intensity or magnitude is greater than a predetermined value, or that the so-called main motion (S-wave) of an earthquake is occurring. For example, as described above, it is determined that the waveform indicating the change in acceleration in the longitudinal, lateral, and vertical directions of the vehicle Ve is a change specific to an earthquake, or that the movement amount and attitude of the vehicle Ve based on the image processing of the on-board camera and the data detected by the detection unit 6 are a change specific to an earthquake. For example, it may be determined that an earthquake has occurred when any one of the three determinations, including the reception of an emergency earthquake warning, or two or more of the three determinations are established. If the determination in step S2 is negative because an earthquake has not occurred, the flow chart is temporarily terminated without executing the subsequent control.

[0022] If the result of step S2 is affirmative because an earthquake has occurred, the process proceeds to step S3, where it is determined that the amount of braking operation B by the driver is smaller than the braking determination threshold value Thb. In step S3, it is determined that the amount of operation of the brake pedal 2a is such that the total braking force of the wheels 3 is reduced by the operation of the VSC as described above, or that the braking operation by the driver is intended to stop or slow down the vehicle due to an earthquake. For this reason, the braking determination threshold value Thb is determined based on a predetermined maximum braking force of the wheels 3, or is set based on experiments, the driver's preferences, etc.

[0023] If the braking operation amount B is smaller than the braking judgment threshold value Thb and thus the answer is affirmative in step S3, the process proceeds to step S4, where a steering judgment value S of the steering wheel 4a by the driver is calculated. The steering judgment value S is calculated by the following formula (2) based on the steering angle St, steering speed Sv, steering angle coefficient K1, and steering speed coefficient K2 of the steering wheel 4a. S = K1 × |St| + K2 × |Sv| … (2)

[0024] After the steering judgment value S is calculated, the process proceeds to step S5, where it is determined whether the steering judgment value S is smaller than a steering judgment threshold value Ths. The steering judgment threshold value Ths is set so that it can be determined that the driver is trying to avoid an obstacle or the like, and is determined in advance by experiments or the like, or is determined based on data such as the driver's steering operation tendencies and habits.

[0025] If the steering determination value S is smaller than the steering determination threshold Ths and therefore the answer is affirmative in step S5, the process proceeds to step S6, where the VSC start threshold Th for determining whether or not to activate the VSC is set to the earthquake determination threshold Th2. This earthquake determination threshold Th2 is set to a value smaller than the reference threshold Th1 for determining whether or not to activate the VSC when no earthquake has occurred. That is, in step S6, the VSC is set to activate earlier compared to when no earthquake has occurred. This flow chart is temporarily terminated after the VSC start threshold Th has been set to the earthquake determination threshold Th2.

[0026] If the braking operation amount B is equal to or greater than the braking judgment threshold Thb in step S3, or the steering judgment value S is equal to or greater than the steering judgment threshold Ths in step S5, and thus a negative judgment is made in step S3 or step S5, the process proceeds to step S7. In step S7, the VSC start threshold Th is set to a reference threshold Th1, which is a normal threshold for judging the operation of VSC. This reference threshold Th1 is a value that can detect a decrease in vehicle stability due to, for example, skidding or oversteering of the vehicle Ve. This flow chart is temporarily terminated after the VSC start threshold Th is set to the reference threshold Th1.

[0027] According to the above-described embodiment, when an earthquake occurs, the VSC start threshold Th is set to the earthquake determination threshold Th2, which is smaller than the reference threshold Th1, so that the VSC is activated early. When an earthquake occurs, the behavior of the vehicle Ve becomes unstable due to unexpected shaking, so that the stability of the vehicle Ve can be prevented from decreasing by activating the VSC relatively early. On the other hand, when the driver performs a relatively large braking operation or steering operation, the VSC start threshold Th is maintained at the reference threshold Th1. In such a case, the driver may immediately stop or slow down the vehicle Ve, or may try to avoid an obstacle, etc., so that early activation of the VSC may result in the vehicle not performing the behavior intended by the driver. Therefore, in such a case, by maintaining the VSC start threshold Th at the reference threshold Th1, the avoidance performance of the vehicle can be ensured, or a decrease in deceleration can be suppressed, so that the VSC can be appropriately executed.

[0028] Next, another example of the control executed by the ECU 5 in the embodiment of the present invention will be described with reference to Fig. 3. In the flowchart of the other example, a case is considered in which the driver is about to change the traveling direction of the vehicle Ve due to approaching a curve or an intersection, etc., when the steering judgment value S by the driver is greater than the steering judgment threshold value Ths. Note that in the flowchart of the other example described below, steps similar to those already described are given the same reference numerals, and their explanation is omitted or simplified.

[0029] As shown in Fig. 3, in the flowchart of the other example, the same control as in steps S1 to S4 in the flowchart shown in Fig. 2 is performed. Then, the process proceeds to step S8, where it is determined whether or not the above-mentioned steering judgment value S is greater than the steering judgment threshold value Ths. If the steering judgment value S is equal to or less than the steering judgment threshold value Ths in step S8, it is determined that the operation is not an operation to avoid an obstacle or the like. In that case, the process proceeds to the above-mentioned step S6, where the steering judgment threshold value Ths is set small in order to quickly suppress a decrease in the stability of the vehicle Ve due to the shaking of the earthquake, and the flowchart is temporarily terminated.

[0030] On the other hand, if the steering judgment value S is greater than the steering judgment threshold value Ths, it is judged that an operation to avoid an obstacle or the like is being performed. In that case, the answer is affirmative in step S8 and the process proceeds to step S9, where it is judged whether the actual yaw rate Yr of the vehicle Ve is smaller than 0. In step S9, the yaw rate is set to a positive value when the yaw angle of the vehicle Ve is changing to the left, and conversely, the yaw rate is set to a negative value when the yaw angle of the vehicle Ve is changing to the right. If the detected actual yaw rate Yr of the vehicle Ve is smaller than 0, and therefore the traveling direction of the vehicle Ve is to the right, the answer is affirmative in step S9 and the process proceeds to step S10.

[0031] In step S10, it is determined that the deviation ΔYr of the yaw rate is smaller than 0. As described above, the deviation ΔYr of the yaw rate is the deviation between the reference yaw rate Yr_std and the actual yaw rate Yr. Therefore, if the deviation ΔYr is a negative value and the result of the affirmative determination in step S10 is negative, the amount of change in the yaw angle of the vehicle Ve to the right is not in accordance with the steering operation of the driver, and the steering operation of the driver is not reflected. In other words, since it is necessary to further change the direction of the vehicle Ve to the right, it is determined that the driver is trying to change the course of the vehicle Ve. In such a case, a braking torque is applied to the inner wheel 3 on the rear side by the operation of the VSC, which assists the steering operation of the driver. In other words, since it is preferable to operate the VSC earlier, the process proceeds to step S6, the VSC start threshold Th is set to the earthquake determination threshold Th2, and this flow chart is temporarily terminated.

[0032] On the other hand, if the deviation Δ of the yaw rate is equal to or greater than 0 and the result of the negative determination in step S10 is negative, the vehicle Ve is at a yaw angle corresponding to the driver's steering operation, or the amount of change in the yaw angle of the vehicle Ve to the right is greater than the amount of change corresponding to the driver's steering operation (slipping). In other words, it is not necessary to further change the direction of the vehicle Ve to the right, and since the absolute value of the steering speed Sv or the steering angle St is reduced immediately after the steering operation, it is determined that the steering operation is an operation to avoid an obstacle or the like. In this case, since the result of the negative determination in step S10 is negative, the process proceeds to step S7, the VSC start threshold Th is set to the reference threshold Th1, and the flow chart is temporarily terminated. In other words, the flow chart is temporarily terminated without accelerating the operation of the VSC so that the avoidance operation intended by the driver is executed.

[0033] In the above-mentioned step S9, if the actual yaw rate Yr of the vehicle Ve is 0 or more, the result is negative, and the process proceeds to step S11, where it is determined that the yaw rate deviation Δ is 0 or more. If the result is negative in step S9, the traveling direction of the vehicle Ve has changed to the left. Therefore, if the yaw rate deviation Δ is 0 or more and the result is affirmative in step S11, the vehicle Ve has a yaw angle corresponding to the steering operation of the driver, or the amount of change in the yaw angle of the vehicle Ve to the left is not a change amount corresponding to the steering operation of the driver, and the steering operation of the driver is not reflected. In that case, as in the case where the result is affirmative in the above-mentioned step S10, it is better to operate the VSC early, so the process of step S6 is performed and this flowchart is temporarily terminated.

[0034] On the other hand, if the yaw rate deviation Δ is a negative value, the amount of change in the yaw angle of the vehicle Ve to the left in response to the steering operation is greater than the amount of change corresponding to the driver's steering operation (the vehicle is skidding). In this case, it is determined that the driver is trying to avoid an obstacle or the like, and the result is negative in step S11. In this case, the process proceeds to step S7, the VSC start threshold Th is set to the reference threshold Th1, and this flow chart is temporarily ended.

[0035] According to the embodiment of the other example described above, even if the driver performs a relatively large steering operation when an earthquake occurs, if the operation is to turn a curve or an intersection, the VSC start threshold Th is set to the earthquake determination threshold Th2. In such a case, the VSC applies a braking torque to the inner rear wheel 3 of the vehicle Ve to change the yaw angle of the vehicle Ve to perform the operation intended by the driver, or to smoothly turn the vehicle Ve. In the case of such brake control, the control by the VSC is less likely to interfere with the behavior of the vehicle Ve intended by the driver, compared to the case of avoiding an obstacle or the like as described above. Therefore, by starting the VSC early, it is possible to suppress the stability of the vehicle Ve from decreasing due to the shaking of the earthquake, that is, it is possible to execute an appropriate VSC. [Explanation of symbols]

[0036] Vehicle 1. Driving force source 2 Brake device 2a Brake pedal (brake operation part) 4a Steering wheel 5 ECU (controller) 5b Braking judgment section 5c Steering judgment section 5d Earthquake determination section

Claims

[Claim 1] a brake device that generates a braking force on a vehicle when a driver operates a brake operation unit; a steering wheel that is operated by the driver to adjust the traveling direction of the vehicle; A vehicle control device that performs stability control to suppress the occurrence of lateral skid of a wheel by controlling the brake device when a change amount of a yaw rate is greater than a predetermined operation threshold value, A controller for controlling execution of the stability control, The controller: An earthquake determination unit that detects the occurrence of an earthquake; a braking determination unit that determines whether a braking operation amount of the brake operation unit is greater than a predetermined braking determination threshold when the earthquake occurs; a steering determination unit that determines whether a steering determination value based on a steering amount of the steering wheel is greater than a predetermined steering determination threshold value when the earthquake occurs, When the earthquake occurs, the activation threshold is narrowed; When the earthquake occurs, if at least one of the following is true: the braking operation amount is greater than the braking determination threshold value and the steering determination value is greater than the steering determination threshold value, the control for narrowing the operation threshold value is not performed. A vehicle control device comprising:

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