JP6151318B2 - Vehicle stabilization device - Google Patents

Description

  The present invention relates to a vehicle stabilization device for ensuring running stability of a vehicle.

  Patent Document 1 includes a braking force distribution device that can distribute braking force to left and right wheels, and ensures vehicle running stability by controlling the yaw moment of the vehicle based on the braking force difference between the left and right wheels. A yaw moment control device is disclosed.

JP 2008-222139 A

  For example, when a braking operation is performed on a split μ road having different road surface resistance between the left and right wheels of the vehicle, the braking force distribution device according to Patent Document 1 distributes a relatively small braking force to the wheels on the low μ road side. A relatively large braking force is distributed to the wheels on the high μ road side. As a result, in the yaw moment control device according to Patent Document 1, a braking force difference is generated between the left and right wheels.

  By the way, the magnitude of the braking force acting on the vehicle wheel is usually obtained by detecting (or calculating / estimating) the brake fluid pressure generated by the brake mechanism provided on the wheel during the braking operation. In general, the magnitude of the braking force acting on the wheels of the vehicle correlates with a friction coefficient (pad μ value) related to a braking friction material such as a brake pad. That is, when the pad μ value related to a brake pad of a certain wheel changes (for example, rust due to moisture absorption or change over time due to wear), the magnitude of the braking force acting on the wheel also changes.

  In short, when the friction coefficient of the brake friction material for the wheel changes, the acquired value related to the magnitude of the braking force acting on the wheel becomes different from the normal value. In other words, the acquired value relating to the magnitude of the braking force acting on the wheel includes a change in the friction coefficient relating to the friction material for braking the wheel. Therefore, the difference in braking force between the left and right wheels is also affected by the change in the friction coefficient.

  As a result, the yaw moment control device according to Patent Document 1 has a problem that the calculation / estimation accuracy related to the yaw moment of the vehicle is lowered, and it is difficult to ensure the running stability of the vehicle.

  Therefore, an object of the present invention is to provide a vehicle stabilization device that can ensure the running stability of a vehicle even when the friction coefficient of the braking friction material changes.

In order to solve the above-described problem, the invention according to (1) includes a vehicle behavior stabilization control device that executes anti-lock brake control during braking of a vehicle and generates a braking force that suppresses wheel rotation in the braking device, And a yaw moment canceling means that operates to cancel the yaw moment of the vehicle. The vehicle behavior stabilization control apparatus estimates a friction coefficient related to the friction material for braking the wheel, calculates the braking force of the left and right wheels using the estimated friction coefficient, and further A yaw moment generated in the vehicle is calculated based on a braking force difference between a left wheel braking force that suppresses rotation of the left wheel of the vehicle and a right wheel braking force that suppresses rotation of the right wheel of the vehicle, and the yaw moment generated based on the calculated yaw moment is calculated. A control amount of the yaw moment canceling means is set, and the vehicle behavior stabilization control device determines a friction coefficient related to the braking friction material based on a brake fluid pressure supplied to the braking device and a longitudinal acceleration of the vehicle. Is estimated .

In the invention according to (1), in the vehicle behavior stabilization control device, the friction coefficient related to the friction material for braking the wheel is estimated based on the brake fluid pressure supplied to the braking device and the longitudinal acceleration of the vehicle , The braking force of the left and right wheels is calculated using the estimated friction coefficient. Further, the yaw moment generated in the vehicle is calculated based on the calculated braking force difference between the left and right wheels, and the control amount of the yaw moment canceling means is set based on the calculated yaw moment. In this case, when the friction coefficient related to the braking friction material changes, the control amount of the yaw moment canceling means also changes according to the change, so that the yaw moment canceling means is appropriately controlled.
According to the invention according to (1), even when the friction coefficient of the braking friction material changes, appropriate control is performed so as to eliminate the yaw moment of the vehicle. Can be secured. In addition, the vehicle behavior stabilization control device measures the friction coefficient because the friction coefficient related to the wheel braking friction material is estimated based on the brake hydraulic pressure supplied to the braking device and the longitudinal acceleration of the vehicle. Therefore, the friction coefficient of the braking friction material can be estimated by a simple method without requiring a separate measuring means such as a sensor.

The invention according to (2) includes a vehicle behavior stabilization control device that executes antilock brake control during braking of a vehicle to generate a braking force that suppresses wheel rotation in the braking device, and a yaw moment of the vehicle. And a yaw moment canceling means that operates so as to cancel. The vehicle behavior stabilization control apparatus estimates a friction coefficient related to the friction material for braking the wheel, calculates the braking force of the left and right wheels using the estimated friction coefficient, and further determines the left side of the vehicle. A yaw moment generated in the vehicle is calculated based on a braking force difference between a left wheel braking force that suppresses rotation of the wheel and a right wheel braking force that suppresses rotation of the right wheel of the vehicle, and the yaw moment generated based on the calculated yaw moment The control amount of the yaw moment canceling means is set, and when the control amount of the yaw moment canceling means is set, a wheel turning amount that cancels the yaw moment is set .

In the invention according to (2), in the vehicle behavior stabilization control device, the friction coefficient related to the friction material for braking the wheel is estimated, and the braking force of the left and right wheels is calculated using the estimated friction coefficient. Further, the yaw moment generated in the vehicle is calculated based on the calculated braking force difference between the left and right wheels, and the control amount of the yaw moment canceling means is set based on the calculated yaw moment. When setting the control amount of the yaw moment canceling means, the wheel turning amount is set so as to cancel the yaw moment. In this case, if the friction coefficient of the braking friction material changes , the wheel turning amount, which is the control amount of the yaw moment canceling means, also changes in accordance with this change, so that the yaw moment canceling means is appropriately controlled. .
According to the invention according to (2), even if the friction coefficient of the friction material for braking changes, the appropriate wheel turning amount control is performed so as to eliminate the yaw moment of the vehicle. Driving stability can be ensured.

In the invention according to (3), the vehicle behavior stabilization control device determines that the travel path of the vehicle is a split μ road when the braking force difference exceeds a predetermined threshold, and the travel path is When it is determined that the road is a split μ road, the yaw moment canceling means is operated using the set control amount .

In the invention according to (3), the braking force and the braking force difference between the left and right wheels are calculated using the estimated value of the friction coefficient (the pad μ value related to the brake pad ) related to the wheel braking friction material, and the calculation is performed. When the applied braking force difference exceeds a predetermined threshold value, it is determined that the vehicle traveling path is a split μ road.
According to the invention according to (3), the determination is made based on the braking force difference in consideration of the estimated value of the friction coefficient related to the friction material for braking. In addition to the effect of the invention according to (1), It is possible to improve the determination accuracy related to whether or not the vehicle traveling path is a split μ road.

  The invention according to (4) is characterized in that the yaw moment eliminating means is a steering device capable of automatically turning the steered wheels of the vehicle.

  According to the invention which concerns on (4), a vehicle stabilization apparatus can be provided in the vehicle provided with the steering apparatus which can steer a steering wheel automatically irrespective of a driver | operator's intention.

  According to the present invention, the running stability of the vehicle can be ensured even when the friction coefficient of the braking friction material changes.

It is a figure which shows a vehicle provided with a vehicle stabilization apparatus. It is a figure which shows the vehicle which drive | works a split micro road. (A) is a figure which shows the vehicle body speed and wheel speed in a split micro road, (b) is a figure which shows the brake fluid pressure supplied to a braking device in a split micro road. It is a figure which shows the brake fluid pressure characteristic which concerns on embodiment of this invention which changes according to the change of the pad micro value which concerns on a brake pad. 4A shows the brake fluid pressure characteristic when the pad μ value is larger than the reference value, FIG. 4B shows the brake fluid pressure characteristic when the pad μ value is the reference value, and FIG. 4C shows the pad. The brake fluid pressure characteristics when the μ value is smaller than the reference value are shown. It is a flowchart figure which shows the procedure for ensuring the driving | running | working stability of the vehicle on a split micro road. It is a figure which shows an example of the correlation map which shows the correlation of pad micro value, brake fluid pressure, and a longitudinal acceleration.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as appropriate.
FIG. 1 is a diagram illustrating a vehicle including a vehicle stabilization device.
As shown in FIG. 1, a vehicle stabilization device 1 according to the present embodiment is provided in a vehicle 2 and functions to ensure traveling stability of the vehicle 2.
The vehicle stabilization device 1 according to this embodiment includes an AS device 4, a VSA device 6, an AS motor 42, a vehicle control device 50, and a steering controller 51. The VSA device 6, the vehicle control device 50, and the steering controller 51 function as a “vehicle behavior stabilization control device” of the present invention.

The vehicle 2 is a four-wheel vehicle having four wheels 3, and the two wheels on the front side (FRONT side) are steered wheels. Each wheel 3 is provided with a braking device 30 including, for example, a disc brake mechanism.
The braking device 30 is not limited to the disc brake mechanism, and may be a drum brake mechanism. Further, in the vehicle 2, all four wheels 3 may be steering wheels.

  As shown in FIG. 1, the vehicle 2 of the present embodiment is set on the left side (LEFT) and the right side (RIGHT) toward the front (FRONT). In the following, the left side is indicated by a subscript “L” and the right side is indicated by a subscript “R” as necessary. For example, the left wheel is indicated by “3L” and the right wheel is indicated by “3R”.

  The vehicle 2 includes an active steering device (AS device) 4. The AS motor 42 provided in the AS device 4 is driven according to the operation amount of the steering wheel 43 by the driver. Further, the AS motor 42 can steer the steered wheels without depending on the steering operation by the driver. The AS motor 42 is controlled by the steering controller 51. As a mode in which the steering controller 51 controls the driving of the AS motor 42, a known method may be adopted as appropriate.

  The AS device 4 has a so-called steer-by-wire function in which the steering shaft 40 and the rack shaft 41 are individually operated, and the rack shaft 41 is displaced by driving the AS motor 42 according to the operation amount of the steering wheel 43. You may have.

The braking device 30 is driven using the brake fluid pressure generated by the braking control by the VSA device 6. When a brake pedal (not shown) is depressed, the VSA device 6 activates an ABS (anti-lock brake system) as necessary (for example, when the wheel 3 falls into a locking tendency). The VSA device 6 operates the ABS by adjusting the brake fluid pressure supplied to the braking device 30. The braking device 30 generates a braking force according to the brake fluid pressure supplied in accordance with the braking control by the VSA device 6.
The VSA device 6 is configured to be able to control the braking device 30 so as to suppress understeer and oversteer by individually controlling the braking force acting on the four wheels 3.
Hereinafter, the braking force that suppresses the rotation of the left wheel 3L is referred to as a left wheel braking force, and the braking force that suppresses the rotation of the right wheel 3R is referred to as a right wheel braking force, as necessary.

The vehicle 2 is provided with a vehicle control device 50. The vehicle control device 50 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and peripheral circuits (not shown).
The vehicle control device 50 is connected to the steering controller 51 and the VSA device 6 through a communication line so as to be capable of data communication with each other. A communication line connecting the vehicle control device 50, the steering controller 51, and the VSA device 6 is not particularly limited, and for example, a CAN (Controller Area Network) may be employed.

  Further, the vehicle 2 includes a wheel speed sensor 7, an acceleration sensor 8, a hydraulic pressure sensor 9, and a steering angle sensor 10.

  The wheel speed sensor 7 detects the rotational speed (wheel speed) of each wheel 3. The wheel speed sensor 7 outputs the detected wheel speed as a wheel speed signal. A wheel speed signal output from the wheel speed sensor 7 is input to the VSA device 6. The vehicle control device 50 calculates the vehicle speed (vehicle speed) of the vehicle 2 from the wheel speed signal.

  The acceleration sensor 8 detects longitudinal acceleration (longitudinal acceleration) generated in the vehicle 2. The acceleration sensor 8 outputs the detected longitudinal acceleration as an acceleration signal. The acceleration signal output from the acceleration sensor 8 is input to the vehicle control device 50. The vehicle control device 50 calculates the longitudinal acceleration of the vehicle 2 from the acceleration signal.

The hydraulic pressure sensor 9 detects the brake hydraulic pressure supplied to the braking device 30. The VSA device 6 calculates the brake fluid pressure supplied to the braking device 30 based on the brake fluid pressure detected by the fluid pressure sensor 9 and the control state of the VSA device 6 itself. The brake fluid pressure thus calculated is input to the vehicle control device 50.
A configuration may be adopted in which the brake fluid pressure supplied from the VSA device 6 to the left braking device 30L and the right braking device 30R is notified to the vehicle control device 50 via a communication line (CAN). If comprised in this way, the vehicle control apparatus 50 can acquire the brake hydraulic pressure supplied to the braking device 30 (the braking device 30L on the left side, the braking device 30R on the right side) from the VSA device 6 from the VSA device 6.

  The steering angle sensor 10 detects an operation amount (steering angle) of the steering wheel 43. The steering angle sensor 10 outputs the detected steering angle as a steering angle signal. A steering angle signal output from the steering angle sensor 10 is input to the vehicle control device 50. The rudder angle sensor 10 may adopt a configuration in which the steered angle of the wheel 3 that is a steered wheel is detected and the detected steered angle is output as a steered angle signal.

The VSA device 6 adjusts the brake fluid pressure supplied to the braking device 30 of each wheel 3 when the driver operates a brake pedal (not shown) while the vehicle 2 is traveling on the split μ road. It works to ensure the running stability of the vehicle 2.
FIG. 2 is a view of a vehicle traveling on a split μ road viewed from above. FIG. 3A is a diagram showing the vehicle speed and the wheel speed on the split μ road. FIG. 3B is a diagram showing the brake hydraulic pressure supplied to the braking device 30 in the split μ road. In FIG. 3A, the vertical axis represents the vehicle speed and the wheel speed, and the horizontal axis represents the passage of time. Moreover, in FIG.3 (b), a vertical axis | shaft shows brake fluid pressure and a horizontal axis shows time passage.

  The split μ road is a road surface having different road surface resistances on the left side (LEFT) and the right side (RIGHT) of the vehicle 2. In the split μ road shown in FIG. 2, the road surface resistance on the left side of the vehicle 2 is smaller than the standard road surface resistance (low μ road), while the road surface resistance on the right side is a standard value or larger than the standard value. (High μ road).

In FIG. 3A, the wheel speed of the wheel on the high μ road side (in the example shown in FIG. 2, the wheel speed of the right wheel 3R) is indicated by a broken line, and the wheel speed of the wheel on the low μ road side (in the example shown in FIG. 2). The wheel speed of the left wheel 3L) is indicated by a solid line. Note that the alternate long and short dash line in FIG.
3B, the brake hydraulic pressure supplied to the braking device on the high μ road side (the braking device 30R on the right side in the example shown in FIG. 2) is indicated by a broken line, and the braking device on the low μ road side (FIG. 2). In the example shown in FIG. 2, the brake hydraulic pressure supplied to the left braking device 30L) is indicated by a solid line.

When the travel path 100 of the vehicle 2 is a split μ road with a low μ road on the left side and a high μ road on the right side as shown in FIG. In the VSA device 6 according to the example, the left wheel 3L tends to lock, and thus operates to reduce the braking force. As a result, a clockwise yaw moment Ym is generated in the vehicle 2, and the traveling stability of the vehicle 2 is reduced. When the driver operates the steering wheel 43 and turns the wheel 3 of the steered wheel to the left when the yaw moment Ym is generated, the vehicle 2 enters a counter-steer state.
A state in which the turning angle (the turning angle of the drive wheels) is generated in the direction opposite to the turning direction of the vehicle 2 (rightward in the example shown in FIG. 2) (leftward in the example shown in FIG. 2) is counter-steered. State.

Therefore, in the VSA device 6 of the present embodiment, the wheel speed of the wheel 3 is calculated from the wheel speed signal output from the wheel speed sensor 7 (see FIG. 1), and is output to the vehicle control device 50. When there is a wheel 3 having a remarkably low wheel speed when the vehicle 2 is braked, the VSA device 6 determines that the wheel 3 is in a locking tendency and performs ABS control. In the split μ road where the left side is the low μ road shown in FIG. 2, the left (low μ road side) wheel 3L indicated by the solid line in FIG. 3A tends to be locked (see section A1).
In this case, as shown in FIG. 3B, the VSA device 6 reduces the brake hydraulic pressure supplied to the left braking device 30L (see B1). As shown in FIG. 3A, the ABS speed increases the wheel speed of the left wheel 3L (see section A2), thereby eliminating the locking tendency of the left wheel 3L.
A well-known ABS control technique is applied to the VSA device 6 and the vehicle control device 50.

  When the traveling path 100 of the vehicle 2 is a split μ road (see FIG. 2), a clockwise yaw moment Ym is generated in the vehicle 2. At this time, the vehicle control device 50 shown in FIG. 1 gives a command to the steering controller 51 to drive the AS device 4 and controls the front wheels 3 as steering wheels to be steered leftward. The vehicle control device 50 sets the turning amount of the wheel 3 (control amount of the AS device 4) based on the magnitude of the yaw moment Ym generated in the vehicle 2.

In short, the vehicle control device 50 according to the present embodiment (see FIG. 1) is generated in the vehicle 2 based on the braking force difference (difference between the left wheel braking force and the right wheel braking force) generated in the vehicle 2 on the split μ road. The yaw moment Ym (see FIG. 2) to be calculated is calculated (estimated).
The vehicle control device 50 calculates the braking force based on the formula (1) from the brake fluid pressure supplied to the braking device 30 (see FIG. 1).
Braking force = brake hydraulic pressure × brake piston area × pad μ value related to brake pad ×
Brake effective radius / tire dynamic radius (1)
In the formula (1), the brake piston area, the brake effective radius, and the tire moving radius are characteristic values of the vehicle 2 (the wheel 3 and the braking device 30) and are fixed values. The pad μ value related to the brake pad is synonymous with the friction coefficient related to the friction coefficient braking friction material.

The vehicle control device 50 shown in FIG. 1 determines whether or not the travel path 100 (see FIG. 2) of the vehicle 2 is a split μ road based on the calculated braking force.
The vehicle control device 50 calculates the left wheel braking force that stops the rotation of the left wheel 3L by substituting the brake hydraulic pressure supplied from the VSA device 6 to the left braking device 30L into the equation (1). Further, the vehicle control device 50 substitutes the brake fluid pressure supplied from the VSA device 6 to the right braking device 30R into the equation (1), and calculates the right wheel braking force that stops the rotation of the right wheel 3R. Then, the vehicle control device 50 determines that the travel path 100 of the vehicle 2 is a split μ road when the difference in braking force between the left wheel braking force and the right wheel braking force exceeds a predetermined threshold.
The predetermined threshold value when the vehicle control device 50 determines that the road is a split μ road is set in advance as a characteristic value of the vehicle 2.

  The vehicle control device 50 calculates the yaw moment Ym using, for example, a predetermined calculation formula. However, the vehicle control apparatus 50 employs a configuration in which a map indicating the correlation between the braking force difference and the yaw moment Ym is set in advance and the yaw moment Ym corresponding to the braking force difference is calculated using the map. Also good.

  Further, the vehicle control device 50 sets a turning amount of the wheel 3 (a control amount of the AS device 4) that cancels the yaw moment Ym based on the calculated yaw moment Ym. However, a map showing the correlation between the steering amount of the wheels 3 corresponding to the vehicle body speed and the yaw moment Ym is set in advance, and the steering amount of the wheels 3 corresponding to the vehicle body speed and the yaw moment Ym is used using the map. A configuration may be adopted in which

  When the turning amount of the wheel 3 is set, the vehicle control device 50 gives a command to the steering controller 51 and drives the AS motor 42 so that the wheel 3 (steering wheel) is turned using the set turning amount. . As a result, the AS device 4 is controlled, and the wheels 3 (steering wheels) are suitably steered, and the vehicle 2 is prevented from turning due to the yaw moment Ym and the posture is stabilized.

  Thus, in the vehicle 2 of the present embodiment, the AS device 4 is controlled, and the wheels 3 (steering wheels) are suitably steered to eliminate the yaw moment Ym. Thereby, the running stability of the vehicle 2 is ensured. The AS device 4 of the present embodiment operates to cancel the yaw moment Ym generated in the vehicle 2 and functions as a yaw moment canceling means that suppresses the rotation of the vehicle 2 due to the yaw moment Ym.

FIG. 4 is a diagram showing a brake hydraulic pressure characteristic according to the embodiment of the present invention that changes according to a change in the pad μ value. 4A shows the brake fluid pressure characteristic when the pad μ value is larger than the reference value, FIG. 4B shows the brake fluid pressure characteristic when the pad μ value is the reference value, and FIG. 4C shows the pad. The brake fluid pressure characteristics when the μ value is smaller than the reference value are shown. 4A to 4C, the vertical axis represents the brake fluid pressure and the horizontal axis represents the passage of time.
4A to 4C show the case where the left side of the vehicle 2 (see FIG. 1) is a low μ road as in FIG. 3, and the brake fluid supplied to the brake device 30R on the right side. The pressure is indicated by a broken line, and the brake hydraulic pressure supplied to the left braking device 30L is indicated by a solid line. The reference value of the pad μ is a pad μ value (friction coefficient related to a braking friction material) related to a standard brake pad (not shown).

  When the brake μ pressure is the same when the pad μ value related to the brake pad (in the following description, it may be abbreviated as “pad μ value”) is larger than the reference value, the braking force is large. Become. Therefore, when the pad μ value is larger than the reference value, in order to generate a braking force having the same magnitude as that in the case where the pad μ value is the reference value (see FIG. 4B), as shown in FIG. Thus, the change width of the brake fluid pressure supplied to the braking device 30 is reduced.

  On the other hand, when the pad μ value related to the brake pad is smaller than the reference value, the braking force is reduced if the brake hydraulic pressure is the same. Therefore, when the pad μ value is smaller than the reference value, in order to generate a braking force having the same magnitude as the case where the pad μ value is the reference value (see FIG. 4B), FIG. As described above, the change width of the brake hydraulic pressure supplied to the braking device 30 is increased.

  Here, in the vehicle control device 50 (see FIG. 1) according to the present embodiment, the braking force is calculated (estimated) using the equation (1). Conventionally, when the braking force is calculated using equation (1), the pad μ value is used as a reference value (fixed value). That is, the vehicle control device 50 according to the comparative example calculates the braking force using the pad μ reference value without considering the change of the pad μ value.

In the vehicle control device 50 according to the comparative example, the pad μ value related to the brake pad is the reference value (fixed value) in the case of the brake hydraulic pressure characteristic (see FIG. 4A) with a small change width of the brake hydraulic pressure. Then, the braking force calculated by the vehicle control device 50 is smaller than that in the case of the brake hydraulic pressure characteristic (see FIG. 4B) where the change width of the brake hydraulic pressure is medium.
On the other hand, in the case of the brake fluid pressure characteristic (see FIG. 4C) with a large variation range of the brake fluid pressure, the vehicle control device 50 calculates that the pad μ value related to the brake pad is the reference value (fixed value) The braking force to be applied is larger than that in the case of the brake fluid pressure characteristic (see FIG. 4B) in which the change range of the brake fluid pressure is medium.

  As described above, when an error occurs between the braking force calculated by the vehicle control device 50 according to the comparative example and the actual braking force due to the change in the pad μ value related to the brake pad, the vehicle control device 50 according to the comparative example. Cannot accurately calculate (estimate) the yaw moment Ym (see FIG. 2) generated in the vehicle 2 (see FIG. 2).

Further, in the vehicle control device 50 according to the present embodiment, it is determined whether or not the traveling road 100 of the vehicle 2 is a split μ road based on the braking force difference (difference between the left wheel braking force and the right wheel braking force). .
However, if the braking force difference is acquired based on the difference in brake fluid pressure supplied to the left and right braking devices (30L, 30R), the acquired value related to the braking force difference is the pad value related to the brake pad. An error corresponding to the change of μ is included. This is because the brake hydraulic pressure supplied to the left and right braking devices (30L, 30R) does not reflect the change in the pad value μ related to the brake pad, as described above.

  As described above, when the difference in the brake hydraulic pressure supplied to the left and right braking devices (30L, 30R) is changed due to the change in the pad μ value related to the brake pad, whether or not the traveling path 100 of the vehicle 2 is the split μ road. The determination accuracy according to this will decrease.

Therefore, in the vehicle control device 50 according to the present embodiment, the pad μ value related to the brake pad is estimated, and the braking force is calculated by substituting the estimated pad μ value into Equation (1).
In the vehicle control device 50 according to the present embodiment, the pad μ value related to the brake pad is estimated based on the brake hydraulic pressure supplied to the braking device 30 and the longitudinal acceleration of the vehicle 2.

When the brake fluid pressure is supplied to the braking device 30 in the traveling vehicle 2, a braking force is generated and the vehicle 2 decelerates. If the braking force is constant, the vehicle 2 decelerates at a constant rate. In other words, the longitudinal acceleration (deceleration acceleration) is constant. As shown in the equation (1), if the pad μ value and the brake fluid pressure are constant, the braking force is constant. That is, when the pad μ value is the same, if the brake fluid pressure is constant, the longitudinal acceleration generated in the traveling vehicle 2 is constant.
In short, since the pad μ value, brake fluid pressure, and longitudinal acceleration related to the brake pad have a predetermined correlation, the calculation includes a function indicating the correlation between the brake fluid pressure and longitudinal acceleration and the pad μ value. Using the equation, the pad μ value related to the brake pad can be calculated based on the brake fluid pressure and the longitudinal acceleration.

  Therefore, the vehicle control device 50 according to the present embodiment calculates the longitudinal acceleration generated in the vehicle 2 from the acceleration signal output from the acceleration sensor 8, and based on the calculated longitudinal acceleration and the brake hydraulic pressure, The pad μ value related to the pad is calculated (estimated).

  The vehicle control device 50 executes the estimation of the pad μ value related to the brake pad as described above at an appropriate timing. For example, the vehicle control device 50 estimates the pad μ value related to the brake pad when a braking force is generated in the braking device 30 such as when a brake pedal (not shown) is depressed. Further, the vehicle control device 50 may perform estimation of the pad μ value related to the brake pad each time an ignition switch (not shown) is turned ON, or a predetermined time (not particularly limited, for example, 100 hours). Etc.) may be performed each time the elapse of the pad μ value related to the brake pad.

  When calculating the braking force using the equation (1), the vehicle control device 50 calculates the braking force by substituting the estimated value of the pad for the brake pad. As a result, the vehicle control device 50 can accurately detect the brake pad state based on the longitudinal acceleration and the brake fluid pressure even when the brake pad state changes (for example, rust due to moisture absorption or change over time due to wear). The braking force can be calculated.

  As described above, the vehicle stabilization device 1 according to the present embodiment steers the wheels 3 (steering wheels) when the braking force is generated in the vehicle 2 on the split μ road, and the traveling stability of the vehicle 2 is increased. Secure. At this time, the vehicle control device 50 calculates (estimates) the yaw moment Ym (see FIG. 2) generated in the vehicle 2 based on the braking force difference generated in the vehicle 2 (difference between the left wheel braking force and the right wheel braking force). )

Further, the vehicle control device 50 calculates the braking force using the equation (1) including the estimated pad μ value related to the brake pad. For this reason, even when the pad μ value related to the brake pad changes for some reason, the vehicle control device 50 can calculate the braking force with high accuracy. Therefore, the running stability of the vehicle 2 is ensured with high accuracy.
Further, even when the pad μ value related to the brake pad changes for some reason, it is possible to improve the determination accuracy related to whether or not the travel path 100 of the vehicle 2 is a split μ road.

  FIG. 5 is a flowchart showing a procedure for ensuring the running stability of the vehicle on the split μ road. The vehicle control device 50 ensures the running stability of the vehicle 2 on the split μ road by executing the procedure shown in FIG. 5 every time braking force is generated. The procedure will be described below (refer to FIGS. 1 to 4 as appropriate).

  In step S <b> 1, when there is a wheel 3 with a lock tendency, the VSA device 6 executes ABS control and adjusts the left and right brake fluid pressures so that the lock tendency of the wheel 3 is eliminated.

  In step S <b> 2, the vehicle control device 50 estimates the pad μ value related to the brake pad based on the brake hydraulic pressure supplied to the braking device 30 and the longitudinal acceleration of the vehicle 2.

  In step S3, the vehicle control device 50 determines the braking force (left wheel braking force, right wheel braking force) generated in the vehicle 2 and the brake fluid pressure supplied to the braking device 30 and the brake estimated in step S2. The braking force is calculated by substituting the pad μ value related to the pad into the equation (1).

  In step S <b> 4, the vehicle control device 50 calculates the yaw moment Ym generated in the vehicle 2 based on the braking force difference (difference between the left wheel braking force and the right wheel braking force) generated in the vehicle 2.

In step S <b> 5, the vehicle control device 50 determines whether or not the travel path 100 of the vehicle 2 is a split μ road based on a braking force difference (a difference between the left wheel braking force and the right wheel braking force) generated in the vehicle 2. .
As a result of the determination in step S5, when it is determined that the traveling path 100 of the vehicle 2 is not a split μ road (step S5 → No), the vehicle control device 50 ends this procedure. On the other hand, when it is determined that the travel path 100 of the vehicle 2 is a split μ road (step S5 → Yes), the vehicle control device 50 advances the procedure to step S6.

  In step S6, the vehicle control device 50 sets the turning amount of the wheel 3 (the control amount of the AS device 4) based on the calculated yaw moment Ym.

  In step S7, the vehicle control device 50 controls the AS device 4 so that the wheels 3 (steering wheels) are steered by the set turning amount. As a result, the vehicle 2 is prevented from turning due to the yaw moment Ym, and traveling stability is ensured.

  The vehicle control device 50 may employ a configuration that calculates (acquires) the pad μ value related to the brake pad using the correlation map MP1 shown in FIG.

FIG. 6 is a diagram showing an example of a correlation map showing the correlation among the three of the pad μ value, the brake fluid pressure, and the longitudinal acceleration (deceleration) related to the brake pad. In FIG. 6, the vertical axis represents deceleration, and the horizontal axis represents brake fluid pressure.
In the correlation map MP1 shown in FIG. 6, when the brake fluid pressure increases, the deceleration (positive value) of the vehicle 2 increases.

In FIG. 6, the change characteristic of the longitudinal acceleration (deceleration) with respect to the increase of the brake fluid pressure when the pad μ value related to the brake pad takes the reference value (μa) is shown by a solid line.
In addition, the change characteristic of the longitudinal acceleration (deceleration) with respect to the increase of the brake fluid pressure when the pad μ value related to the brake pad takes a value (μb) smaller than the reference value (μa) is indicated by a broken line. . In this case (pad μ value = μb), the change characteristic of the deceleration with respect to the increase of the brake fluid pressure is compared with the change characteristic of the deceleration with respect to the increase of the brake fluid pressure when the pad μ value is the reference value (μa). Become smaller.
Further, the change characteristic of the deceleration with respect to the increase of the brake fluid pressure when the pad μ value related to the brake pad takes a value (μc) larger than the reference value (μa) is indicated by a one-dot chain line. In this case (pad μ value = μc), the change characteristic of the deceleration with respect to the increase of the brake fluid pressure is compared with the change characteristic of the deceleration with respect to the increase of the brake fluid pressure when the pad μ value is the reference value (μa). Become bigger.

  Specifically, for example, when the brake fluid pressure is “ps” and the deceleration is “αs” (see FIG. 6), the vehicle control device 50 relates the intersection “μs” on the correlation map MP1 to the brake pad. Obtained as pad μ value. When the intersection “μs” is located between the characteristic line (solid line) indicating “μa” and the characteristic line (broken line) indicating “μb”, the vehicle control device 50 determines that the characteristic line (solid line) “μa” ”And the characteristic line (broken line)“ μb ”, the value of the intersection“ μs ”is acquired as the pad μ value related to the brake pad.

  Further, in the vehicle control device 50 according to the present embodiment, it is determined whether or not the traveling path 100 of the vehicle 2 is a split μ road based on the braking force difference (the difference between the left wheel braking force and the right wheel braking force) in the vehicle 2. However, the present invention is not limited to this example. The vehicle control apparatus 50 according to the present embodiment may employ a configuration that determines whether or not the travel path 100 of the vehicle 2 is a split μ road based on the slip ratio of the left and right wheels 3.

  In the present embodiment, the AS device 4 has been described as an example of performing the function of the yaw moment eliminating means for suppressing the turning of the vehicle 2 by the yaw moment Ym, but the present invention is not limited to this example. As the yaw moment canceling means, any configuration may be adopted as long as it has a function of operating to cancel the yaw moment Ym of the vehicle 2.

1 Vehicle Stabilizer 2 Vehicle 3 Wheel (Steering Wheel)
4 AS device (yaw moment canceling means)
6 VSA device (vehicle behavior stabilization control device)
30 Braking device 50 Vehicle control device (vehicle behavior stabilization control device)
100 Road Ym Yaw moment

Claims (4)

A vehicle behavior stabilization control device that executes anti-lock brake control at the time of braking of the vehicle, and generates a braking force that suppresses rotation of the wheels in the braking device;
A yaw moment canceling means that operates to cancel the yaw moment of the vehicle,
The vehicle behavior stabilization control device includes:
A left wheel braking force for estimating the friction coefficient of the wheel braking friction material and calculating the braking force of the left and right wheels using the estimated friction coefficient, and further suppressing the rotation of the left wheel of the vehicle; calculating a yaw moment generated in the vehicle based on the braking force difference between the right wheel braking force to suppress the rotation of the right wheel of the vehicle, it sets the control amount of the yaw moment eliminating means on the basis of the yaw moment to the calculated ,
The vehicle behavior stabilization control device estimates a friction coefficient related to the braking friction material based on a brake fluid pressure supplied to the braking device and a longitudinal acceleration of the vehicle. A vehicle behavior stabilization control device that executes anti-lock brake control at the time of braking of the vehicle, and generates a braking force that suppresses rotation of the wheels in the braking device;
A yaw moment canceling means that operates to cancel the yaw moment of the vehicle,
The vehicle behavior stabilization control device includes:
A left wheel braking force for estimating the friction coefficient of the wheel braking friction material and calculating the braking force of the left and right wheels using the estimated friction coefficient, and further suppressing the rotation of the left wheel of the vehicle; calculating a yaw moment generated in the vehicle based on the braking force difference between the right wheel braking force to suppress the rotation of the right wheel of the vehicle, it sets the control amount of the yaw moment eliminating means on the basis of the yaw moment to the calculated ,
A vehicle stabilizing device characterized in that, when setting a control amount of a yaw moment canceling means, a steering amount of a wheel that cancels the yaw moment is set . The vehicle behavior stabilization control device includes:
When the braking force difference exceeds a predetermined threshold value, it is determined that the travel path of the vehicle is a split μ road, and when it is determined that the travel path is a split μ road, the set control amount is used. vehicle stabilization device according to claim 1 or 2, characterized in that actuating said yaw moment eliminating means Te. The vehicle stabilization device according to any one of claims 1 to 3, wherein the yaw moment elimination means is a steering device capable of automatically turning the steered wheels of the vehicle.

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