JP2009113661A - Vehicle behavior control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vehicle behavior control device that suppresses an undesirable vehicle behavior at the time of failure of a yaw rate sensor.
When a failure occurs in the yaw rate sensor 12 and the yaw rate detection value γ is output smaller than the actual yaw rate γr, the slip angle differential value β ′ may exceed the failure determination threshold value βth. In this case, since the determination in step S12 is Yes, the VSA-ECU 6 sets the braking prohibition flag Fpb to 1 in step S14 and returns to the start. As a result, in the understeer suppression control, even when the yaw rate difference Δγ exceeds the understeer determination threshold γth and the determination in step S2 is Yes, the determination in step S3 is No. It will not be done.
[Selection] Figure 5

Description

  The present invention relates to a vehicle behavior control apparatus, and more particularly to a technique for suppressing undesirable vehicle behavior when a yaw rate sensor fails.

  As a device that improves vehicle running safety, ABS (Anti-lock Breaking System) that prevents wheel locking during braking, TCS (Traction Control System) that prevents wheel slipping during acceleration, A vehicle attitude control device in which a side-slip suppression function and the like are added to these is adopted in part. If a side slip occurs due to understeer or oversteer during turning, the vehicle deviates from a travel locus intended by the driver (hereinafter referred to as a target course). For this reason, in the vehicle attitude control device, when the deviation from the target route is determined, control is performed to return the vehicle to the target route by, for example, braking one of the left and right wheels by an independent braking device.

Normally, the deviation from the target path when the vehicle is turning is calculated from the reference yaw rate and the yaw rate sensor by calculating the reference yaw rate from the vehicle speed information input from the vehicle speed sensor and the steering angle information input from the steering angle sensor. It is determined by comparing with the detected yaw rate detection value. For example, when the value obtained by subtracting the yaw rate detection value from the reference yaw rate exceeds a predetermined understeer determination threshold value, the vehicle attitude control device determines that the vehicle is in an understeer state and brakes the wheels inside the turn. Conversely, when the value obtained by subtracting the yaw rate detection value from the reference yaw rate is smaller than a predetermined oversteer determination threshold value (negative value), the vehicle attitude control device determines that the vehicle is in an oversteer state and determines the wheel outside the turn. Brake. (See Patent Documents 1 and 2)
Japanese Patent Laid-Open No. 7-117645 JP 2004-284485 A

  In the vehicle attitude control devices of Patent Documents 1 and 2, when a yaw rate sensor or an electronic component in the ECU has a failure (operation failure, contact failure, etc.) during turning, the value of the yaw rate detection value is output too small. The understeer state is determined, and the wheel inside the turn is braked with a relatively strong braking force. In this case, the vehicle behaves to turn inside the turn with respect to the target route (that is, the vehicle is in an oversteer state), and there is a possibility that the driver may be forced to countersteer or feel uneasy about steering.

  The present invention has been made in view of the above situation, and an object of the present invention is to provide a vehicle behavior control device that suppresses undesirable vehicle behavior when a yaw rate sensor fails.

  A vehicle behavior control device according to a first aspect of the present invention is based on vehicle body speed detection means for detecting a vehicle body speed of a vehicle, steering angle detection means for detecting a steering angle of a tearing wheel, and the vehicle body speed and the steering angle. A reference yaw rate calculating means for calculating the reference yaw rate of the vehicle, a yaw rate detecting means for detecting the yaw rate of the vehicle as a yaw rate detection value, and the inside of the turn according to the difference between the reference yaw rate and the yaw rate detection value during turning. Braking force applying means for applying braking force to the wheels, slip angle differential value calculating means for calculating the slip angle differential value of the vehicle body, and when the absolute value of the slip angle differential value exceeds a predetermined determination threshold, And a braking force application prohibiting unit that prohibits the application of the braking force by the braking force applying unit.

  According to the vehicle behavior control device of the present invention, even if the yaw rate detection value is output too low due to a failure of the yaw rate sensor or the like, even when a large braking force is applied from the braking force applying means to the turning inner wheel, the slip of the vehicle body When the angular differential value becomes large, the braking force is not applied by the braking force applying means, and the behavior of the vehicle that goes inside the turn with respect to the target course is suppressed.

Hereinafter, an embodiment of a vehicle behavior control device according to the present invention will be described in detail with reference to the drawings.
FIG. 1 is a plan view illustrating a device configuration of a vehicle according to the embodiment, FIG. 2 is a block diagram illustrating a schematic configuration of a VSA-ECU according to the embodiment, and FIG. 3 illustrates an understeer suppression unit and a braking prohibition determination unit. It is a block diagram which shows a structure.

<Vehicle device configuration>
First, the device configuration of the vehicle will be described with reference to FIG. In the description, for the four wheels and members arranged corresponding thereto, that is, tires, wheel speed sensors, and the like, subscripts indicating front, rear, left, and right are attached to the reference numerals, for example, wheel 3fl (front left) ), Wheel 3fr (right front), wheel 3rl (left rear), wheel 3rr (right rear), and collectively referred to as wheel 3, for example.

  As shown in FIG. 1, a vehicle (passenger car in this embodiment) 1 includes four wheels 3 on which tires 2 are mounted. Each wheel 3 has a brake 4 and a wheel speed sensor (vehicle speed detection means). 5 and are decorated. In addition, the vehicle 1 controls an EPS (Electric Power Steering) 7 and an EPS 7 in addition to a VSA (Vehicle Stability Assist: Vehicle Behavior Stabilization Control System) -ECU (Electronic Control Unit) 6 in the vehicle interior. An EPS-ECU 8 is provided, a hydraulic unit 9 that supplies pressure oil to each brake 4, and an ENG-ECU 11 that controls the engine 10. The vehicle 1 includes a yaw rate sensor (yaw rate detecting means) 12 that detects the yaw rate of the vehicle body 15, a longitudinal G sensor 13 that detects longitudinal acceleration of the vehicle body 15, and a lateral G sensor 14 that detects lateral acceleration of the vehicle body 15. Equipped in the passenger compartment.

  Each of the VSA-ECU 6, EPS-ECU 8 and ENG-ECU 11 includes a microcomputer, a ROM, a RAM, a peripheral circuit, an input / output interface, various drivers, etc., and a communication line (in this embodiment, a CAN (Controller Area Network)). The hydraulic unit 9 includes four systems of electromagnetic valves, hydraulic circuits, and the like that are PWM-controlled, and can supply pressure oils having different pressures to the brakes 4 of the wheels 3.

  The EPS 7 includes, as main components, a steering gear 21 including a rack and a pinion (not shown), a steering shaft 23 to which a steering wheel 22 is attached at the rear end, and an EPS motor 24 that applies a steering assist force to the steering shaft 23. A steering angle sensor (steering angle detecting means) 25 for detecting the steering angle of the steering wheel 22 is attached to the steering shaft 23.

<VSA-ECU>
Next, with reference to FIG. 2, the principal part structure of VSA-ECU6 of embodiment is demonstrated.
The VSA-ECU 6 of the embodiment includes a vehicle body speed estimation unit 31, a standard yaw rate calculation unit (standard yaw rate calculation means) 32, a control amount setting unit 33, and a control signal output unit 34.

  The vehicle body speed estimation unit 31 estimates the vehicle body speed V of the vehicle based on the wheel speed detection values Wfl, Wfr, Wrl, Wrr input from the wheel speed sensor 5 of each wheel 3. The reference yaw rate calculation unit 32 calculates the reference yaw rate γN based on the estimated value of the vehicle body speed V input from the vehicle body speed estimation unit 31 and the steering angle detection value δ input from the steering angle sensor 25.

  The control amount setting unit 33 inputs the vehicle body speed V input from the vehicle body speed estimation unit 31, the standard yaw rate γN input from the standard yaw rate calculation unit 32, the steering angle detection value δ input from the steering angle sensor 25, and the yaw rate sensor 12. Based on the detected yaw rate detection value γ, the longitudinal acceleration detection value GF of the vehicle body 15 input from the longitudinal G sensor 13, and the lateral acceleration detection value GL of the vehicle body 15 input from the lateral G sensor 14, the hydraulic unit 9, EPS-ECU 8, ENG- Each control amount of the ECU 11 is set. In addition, the control signal output unit 34 outputs a control signal to the hydraulic unit 9, the EPS-ECU 8, and the ENG-ECU 11 according to the control amount set by the control amount setting unit 33.

<Understeer suppression unit and braking prohibition determination unit>
As shown in FIG. 3, an understeer suppressing unit (braking force applying unit) 40 and a braking prohibition determining unit (braking force applying prohibiting unit) 50 are provided in the control amount setting unit 33. The understeer suppressing unit 40 includes a yaw rate difference calculating unit 41 that calculates a difference between the reference yaw rate γN and the detected yaw rate value γ as a yaw rate difference Δγ, and a target braking force Btgt to be applied to the wheel 3 inside the turn. And a braking force setting unit 42 that is set according to the calculation result. Further, the braking prohibition determination unit 50 calculates the time differential value (dβ / dt) of the vehicle body slip angle β as the slip angle differential value β ′ from the lateral acceleration detection value GL, the vehicle body speed V, and the yaw rate detection value γ. A braking prohibition command for outputting a braking prohibition command (a braking prohibition flag Fpb described later) to the braking force setting unit 42 of the understeer suppression unit 40 according to the calculation result of the differential value calculation unit 51 and the slip angle differential value calculation unit 51. And an output unit 52.

<< Operation of Embodiment >>
<Operation of VSA-ECU>
The VSA-ECU 6 includes wheel speed detection values Wfl, Wfr, Wrl, Wrr from the wheel speed sensor 5 of each wheel 3, a steering angle detection value δ from the steering angle sensor 25, and a yaw rate detection value from the yaw rate sensor 12. γ, the longitudinal acceleration detection value GF from the longitudinal G sensor 13 and the lateral acceleration detection value GL from the lateral G sensor 14 are input. In the VSA-ECU 6, after the vehicle body speed V is estimated by the vehicle body speed estimator 31 based on the detected wheel speed values Wfl, Wfr, Wrl, Wrr, the reference yaw rate is based on the vehicle body speed V and the detected steering angle value δ. The calculation unit 32 calculates the normative yaw rate γN. Next, after the braking control amount, the steering control amount, and the output control amount are set in the control amount setting unit 33 based on the input information from each sensor and the standard yaw rate γN, the control signal output unit 34 outputs the hydraulic unit. 9, EPS-ECU 8, ENG-ECU 11, control signals corresponding to the respective control amounts are output. As a result, undesired behavior of the vehicle body 15 is suppressed even when turning and running in the rain, and the steering stability of the vehicle 1 is improved.

<Understeer suppression control>
When the vehicle 1 starts traveling, the VSA-ECU 6 (understeer suppressing unit 40) repeatedly executes understeer suppressing control whose procedure is shown in the flowchart of FIG. 4 at predetermined control intervals. When the understeer suppression control is started, the VSA-ECU 6 first calculates the yaw rate difference Δγ by subtracting the yaw rate detection value γ from the reference yaw rate γN in step S1 of FIG. 4, and then in step S2, the yaw rate difference Δγ becomes a predetermined understeer determination threshold value. It is determined whether or not γth is exceeded. Note that the understeer determination threshold γth is set to a relatively small value within a range in which control hunting or the like is not caused.

  If the yaw rate difference Δγ is small and the determination in step S2 is No, the VSA-ECU 6 returns to the start without performing any processing. On the other hand, when the yaw rate detection value γ deviates greatly from the reference yaw rate γN, the yaw rate difference Δγ exceeds the predetermined understeer determination threshold γth, and the determination in step S2 becomes Yes, the VSA-ECU 6 performs braking described later in step S3. It is determined whether or not the prohibition flag Fpb is 0. When this determination is No, the process returns to the start without performing any processing.

  When the braking prohibition flag Fpb is 1 and the determination in step S3 is Yes, the VSA-ECU 6 calculates the target braking force Btgt corresponding to the yaw rate difference Δγ in step S4, and then in step S5, the target braking force Btgt. A braking control signal for achieving the above is output to the hydraulic unit 9. As a result, even if the vehicle is in an understeer state during turning, the wheel 3 on the inner side of the turn is braked according to the strength of the understeer, and a large deviation from the target course of the vehicle 1 is suppressed.

<Brake prohibition judgment control>
In parallel with the understeer suppression control described above, the VSA-ECU 6 (braking prohibition determination unit 50) repeatedly executes the braking prohibition determination control whose procedure is shown in the flowchart of FIG. 5 at predetermined control intervals. When the braking prohibition determination control is started, the VSA-ECU 6 first calculates the slip angle differential value β ′ by using the following equation in step S11 of FIG. Calculate using (1).
β ′ = GL / V−γ Expression (1)
Note that the equation (1) is expressed by the following equation of motion MV (β ′ + γ) = m · GL
Derived from. Here, m is the inertial mass of the vehicle.

  When the calculation of the slip angle differential value β ′ is finished, the VSA-ECU 6 determines in step S12 whether or not the absolute value | β ′ | of the slip angle differential value β ′ exceeds a predetermined failure determination threshold value βth. If this determination is No, the brake prohibition flag Fpb is set to 0 in step S13 and the process returns to the start. The failure determination threshold value βth is set to a relatively small value (for example, about 2 ° / s) in consideration of the detection error of the yaw rate sensor 12 and the like.

  If for some reason a failure occurs in the yaw rate sensor 12 or the like and the yaw rate detection value γ is output smaller than the actual yaw rate γr, the slip angle differential value β ′ may exceed the failure determination threshold value βth. In this case, since the determination in step S12 is Yes, the VSA-ECU 6 sets the braking prohibition flag Fpb to 1 in step S14 and returns to the start. As a result, in the understeer suppression control, even when the yaw rate difference Δγ exceeds the understeer determination threshold γth and the determination in step S2 is Yes, the determination in step S3 is No. It will not be done.

(When braking prohibition judgment control is not performed)
FIG. 6 shows each value (yaw rate detection value γ) when the brake prohibition determination control is not performed and the yaw rate sensor 12 has failed during the right turn (the yaw rate detection value γ becomes 10% of the actual yaw rate γ). The steering angle detection value δ, the lateral acceleration detection value GL, the target braking force Btgt, and the brake hydraulic pressure Pb) are time-dependent graphs. As can be seen from the figure, if the yaw rate sensor 12 fails and the lateral acceleration detection value GL increases due to right turn running, while the yaw rate detection value γ remains small, the yaw rate difference Δγ is understeered during turning. The threshold value γth may be exceeded. In that case, the wheel 3 on the inner side of the turn is braked (the values of the target braking force Btgt and the brake hydraulic pressure Pb are increased: a portion surrounded by a broken line in FIG. 6), and a spin moment toward the inner side of the turn acts. Falls into an oversteer state or spin state. In the example of FIG. 6, the driver performs reverse steering (counter steering: a portion surrounded by a two-dot chain line in FIG. 6) in order to suppress the spin of the vehicle 1.

(When braking prohibition judgment control is performed)
FIG. 7 shows each numerical value (yaw rate detection value γ) when the braking prohibition determination control is performed and the yaw rate sensor 12 is lost during the right turn traveling (the yaw rate detection value γ becomes 10% of the actual yaw rate γ). , Steering angle detection value δ, lateral acceleration detection value GL, slip angle differential value β ′, target braking force Btgt). As can be seen from the figure, due to the failure of the yaw rate sensor 12, the lateral acceleration detection value GL increases as the vehicle turns to the right, while the yaw rate detection value γ remains small. The difference Δγ may exceed the understeer determination threshold γth. However, when the braking prohibition determination control is performed, the absolute value | β ′ | of the slip angle differential value β ′ exceeds the failure determination threshold value βth, so that the wheel 3 inside the turn is not braked (target) The braking force Btgt remains 0), and the vehicle 1 does not receive a spin moment toward the inside of the turn. As a result, unlike the case where the braking prohibition determination control is not performed, the vehicle 1 does not fall into the oversteer state or the spin state, and extremely stable turning traveling is realized.

  Although description of specific embodiment is finished above, the aspect of the present invention is not limited to the above embodiment. For example, in the above-described embodiment, braking on the wheel on the inner side of the turn is prohibited when the yaw rate sensor fails, but steering on the inner side of the turn by the electric power steering device and engine output control by the engine ECU are prohibited. You may make it do. In addition, the specific configuration of the vehicle, the specific procedure of the control, and the like can be appropriately changed without departing from the gist of the present invention.

It is a top view which shows the apparatus structure of the vehicle which concerns on embodiment. It is a block diagram which shows schematic structure of VSA-ECU which concerns on embodiment. It is a block diagram which shows the structure of an understeer suppression part and a braking prohibition determination part. It is a flowchart which shows the procedure of the understeer suppression control which concerns on embodiment. It is a flowchart which shows the procedure of the braking prohibition determination control which concerns on embodiment. It is a graph which shows the time change of each numerical value when braking prohibition determination control is not performed. It is a graph which shows the time change of each numerical value when braking prohibition determination control is performed.

Explanation of symbols

1 Vehicle 3 Wheel 4 Brake 6 VSA-ECU
9 Hydraulic unit 12 Yaw rate sensor (Yaw rate detection means)
15 Body 25 Steering angle sensor (steering angle detection means)
31 Vehicle speed estimation unit (vehicle speed detection means)
32 reference yaw rate calculation unit 40 understeer suppression unit (braking force applying means)
50 Braking prohibition determination unit (braking force application prohibiting means)
51 Slip angle differential value calculation unit

Claims (1)

Vehicle speed detection means for detecting the vehicle speed of the vehicle;
Steering angle detection means for detecting the steering angle of the steering wheel;
A reference yaw rate calculating means for calculating a reference yaw rate of the vehicle based on the vehicle body speed and the steering angle;
Yaw rate detecting means for detecting the yaw rate of the vehicle as a yaw rate detection value;
Braking force applying means for applying a braking force to the wheel on the inner side of the turn according to the difference between the reference yaw rate and the detected yaw rate when turning;
Slip angle differential value calculating means for calculating the slip angle differential value of the vehicle body;
A vehicle behavior control device comprising braking force application prohibiting means for prohibiting application of braking force by the braking force applying means when the absolute value of the slip angle differential value exceeds a predetermined determination threshold.

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