JP2009269573A - Vehicle behavior control unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vehicle behavior control unit, achieving shortened processing time required for the cooperative control of a plurality of devices, and easiness to cope with at device malfunction. <P>SOLUTION: A wheel motion control unit 40 decides whether or not a point of application of force η is greater than a front shaft position (position of a front wheel 3f) Lf in step S7. When the above decision is Yes, in step S8, the wheel motion control unit 40 determines the point of application of force η to be the front shaft position Lf (η=Lf), and also calculates a braking moment Mb [Mb=(η-Lf)×F]. In step S12, the wheel motion control unit 40 calculates a total value Ffy of front wheel lateral forces and a total value Fry of rear wheel lateral forces so as to distribute the steering control component of a virtual lateral force F to the front and rear wheels 3f, 3r of a two-wheel model. In step S14, the wheel motion control unit 40 calculates a total value Flx of left wheel front-rear forces and a total value Frx of right wheel front-rear forces so as to distribute the braking moment Mb to left and right wheels 3l, 3r. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a vehicle behavior control apparatus that cooperatively controls a plurality of wheel motion control devices, and in particular, achieves shortening of processing time required for cooperative control of a plurality of devices, facilitation of handling in the event of a device failure, etc. Related to technology.

In recent years, instead of the conventional front-wheel steering vehicle in which only the front wheels are steered, a rear-wheel steering device that steers the left and right rear wheels in order to improve steering stability during high-speed driving and reduce the turning radius during parking A four-wheel steering vehicle equipped with is being developed. In addition, in order to realize further improvement in running stability and turning performance, a braking / driving device that brakes or drives each wheel according to a vehicle speed, a yaw rate, or the like has also appeared. In a vehicle including a plurality of devices of this type, in order to suppress control interference between the devices, the additional tire generation force to each wheel is determined based on the control limit calculated from the size of the friction circle of each wheel. Alternatively, cooperative control that sets control distribution of each device based on the grip margin of each wheel is generally employed (see Patent Document 1).
JP 2006-264561 A

  In the method of Patent Document 1, in order to individually calculate the size of the friction circle and the grip margin for each wheel, it is necessary to estimate the friction coefficient of the road surface and the self-aligning torque. Therefore, in order to cope with a situation where the road surface condition and the like change every moment, it is necessary to perform a calculation using a complicated calculation formula at a high speed, and a high-performance and expensive calculation processing device is required. In addition, when it is not easy to calculate the friction circle and the grip margin, there is a problem that it is difficult to distribute the tire generation force to each wheel and to distribute the control to each device. On the other hand, in order to solve such problems, it is conceivable to obtain analytical solutions for friction circles and grip margins by simple analytical means. Based on such analytical solutions, the above-described tire generation force distribution and control are considered. When the distribution is performed, the error of the analytical solution directly affects the control accuracy. For this reason, even if an excess or deficiency occurs in the behavior when applied to an actual vehicle, it cannot be handled by the control law, and as a result, the control result is lowered. In addition, the method using the analysis means requires an unrealistic countermeasure such as rebuilding a control rule when a change occurs in the control allocation target (for example, when a certain device fails) ( Or, the control result deteriorates by the amount of change).

  The present invention has been made in view of such a background, and provides a vehicle behavior control device that realizes shortening of processing time required for cooperative control of a plurality of devices and facilitation of handling when a device fails. With the goal.

  According to a first aspect of the present invention, a vehicle behavior control device includes: target behavior setting means for setting a target behavior of a vehicle based on at least one of a driving operation of a driver and a traveling state of the vehicle; Based on the actual behavior acquisition means for detecting or estimating the actual behavior of the vehicle, and based on the difference between the target behavior and the actual behavior, the virtual lateral force setting for setting the virtual lateral force to be applied to the vehicle and its force point And wheel motion control means for controlling the motion of the wheel based on the setting result of the virtual lateral force setting means.

  Moreover, 2nd invention is a vehicle behavior control apparatus which concerns on 1st invention, The said vehicle is equipped with the wheel steering means to steer the said wheel, The said wheel motion control means drives the said wheel steering means It is characterized by controlling.

  According to a third aspect of the present invention, in the vehicle behavior control device according to the first or second aspect of the invention, the vehicle includes a longitudinal force adding means for braking or driving the wheel, and the wheel motion control means. Is configured to drive and control the longitudinal force adding means.

  According to a fourth aspect of the present invention, in the vehicle behavior control apparatus according to the third aspect of the present invention, when the vehicle includes the wheel steering means, the wheel motion control means sets the wheel steering means to the longitudinal force. It is characterized in that drive control is given priority over the adding means.

  According to the vehicle behavior control apparatus according to the first to third inventions, since the steering amount and the braking amount are calculated based on the virtual lateral force and the applied force point, the size of the friction circle and the grip margin are individually set for each wheel. Compared to conventional devices that calculate the speed, the calculation process can be performed in a very short time, and it is possible to respond to changes in road surface conditions, etc. at a relatively high speed and with high accuracy. It becomes. Further, according to the vehicle behavior control device according to the fourth aspect of the invention, when the virtual lateral force is applied only by the steering control, the wheels are not braked, so that an unnecessary decrease in the vehicle speed is suppressed and the driver is controlled. No longer feels slow down.

Hereinafter, an embodiment of a four-wheeled vehicle (vehicle: hereinafter simply referred to as an automobile) to which a vehicle behavior control device according to the present invention is applied will be described in detail with reference to the drawings.
FIG. 1 is a plan view showing a device configuration of an automobile according to the embodiment, and FIG. 2 is a block diagram showing a schematic configuration of a VSA-ECU according to the embodiment.

<Vehicle device configuration>
First, a schematic configuration of an automobile according to an embodiment will be described with reference to FIG. In the description, for the four wheels and members arranged for them, that is, tires, suspensions, and the like, subscripts indicating front, rear, left and right are attached to the reference numerals, for example, left front wheel 3fl, right front wheel 3fr, left For example, the rear wheel 3rl and the right rear wheel 3rr are collectively referred to as the wheel 3.

  In the automobile 1 shown in FIG. 1, four wheels 3 are respectively installed on the front, rear, left and right of the vehicle body 2 and each wheel 3 supports the vehicle body 2 via a suspension 4 including a suspension arm, a spring, a damper and the like. Yes. Each wheel 3 is provided with a tire 5 on its outer periphery and a brake (disc brake caliper) 6 on its inner periphery. In addition, the automobile 1 is equipped with an engine 7 at the front thereof, and is also used for the front wheel steering mechanism 8 used for turning the left and right front wheels 3fl and 3fr, and the steering of the left and right rear wheels 3rl and 3rr, respectively. Left and right rear wheel steering mechanisms 9l and 9r are installed.

  A steering shaft 12 having a steering wheel 11 attached to the rear end thereof is installed in the driver's seat of the automobile 1. The steering shaft 12 is provided with a reaction force actuator 13 that applies a steering reaction force to the driver, and a steering angle sensor 15 that detects an operation amount of the steering wheel 11 by the driver. Further, the vehicle 1 is provided with a wheel speed sensor 16 for detecting the rotational speed (wheel speed) in each wheel 3, a lateral G sensor 17 for detecting lateral acceleration, and a longitudinal G sensor for detecting longitudinal acceleration. 18, a yaw rate sensor 19 for detecting the yaw rate, and the like are installed at appropriate positions of the vehicle body 2.

  The front wheel steering mechanism 8 includes a steering gear 21 having front wheel side knuckles 20fl and 20fr connected to both ends thereof, a front wheel steering actuator 22 that drives the steering gear 21, and the like. The rear wheel steering mechanisms 9l and 9r are composed of linear-acting rear wheel steering actuators 24l and 24r interposed between the vehicle body 2 and the rear wheel knuckle 20rl and 20rr, position sensors (not shown), and the like. Has been.

  The vehicle 1 includes a VSA (Vehicle Stability Assist: Vehicle Behavior Stabilization Control System) -ECU (Electronic Control Unit) 31, a steering ECU 32 that drives and controls the front wheel steering actuator 22, the rear wheel steering actuators 24l and 24r, and the like. A hydraulic unit 33 that supplies pressure oil to the brake 6 and an engine ECU 34 that performs overall control of the engine 7 are installed.

  Each of the VSA-ECU 31, the steering ECU 32, and the engine ECU 34 includes a microcomputer, a ROM, a RAM, a peripheral circuit, an input / output interface, various drivers, and the like, and a communication line (CAN (Controller Area Network) in this embodiment). ) Are connected to each other. The hydraulic unit 33 includes four systems of electromagnetic valves, hydraulic circuits, and the like that are PWM-controlled. In addition to supplying hydraulic pressure from a brake pedal (brake master cylinder) (not shown) to the brakes 6 of the wheels 3 as they are, Based on a drive signal from the VSA-ECU 31, pressure oils having different pressures are supplied to the brakes 6, respectively.

<Wheel motion control device>
The VSA-ECU 31 of this embodiment is equipped with a wheel motion control device.
As shown in FIG. 2, the wheel motion control device 40 includes a vehicle speed estimation unit 41, an acceleration / deceleration coefficient setting unit 42, a target yaw rate setting unit 43, a target skid angle setting unit 44, and an actual skid angle estimation unit 45. A pitch coefficient setting unit 46, a yaw rate difference calculating unit 47, a side slip angle difference calculating unit 48, a virtual lateral force setting unit 49, and a control amount setting unit 50. The vehicle speed estimation unit 41 estimates the vehicle speed v of the automobile 1 based on the wheel speeds Wfl, Wfr, Wrl, Wrr input from the wheel speed sensor 16 of each wheel 3.

  The acceleration / deceleration coefficient setting unit 42 sets the acceleration / deceleration coefficient Ka of the automobile 1 based on the differential value (that is, acceleration) of the vehicle speed v input from the vehicle speed estimation unit 41. The target yaw rate setting unit 43 sets the target yaw rate γtgt based on the vehicle speed v input from the vehicle speed estimation unit 41 and the steering angle δ input from the steering angle sensor 15. The target side slip angle setting unit 44 also sets the target side slip angle βtgt based on the vehicle speed v input from the vehicle speed estimation unit 41 and the steering angle δ input from the steering angle sensor 15. The actual side slip angle estimation unit 45 is based on the vehicle speed v input from the vehicle speed estimation unit 41, the yaw rate (actual yaw rate) γ input from the yaw rate sensor 19, and the side acceleration Gy input from the side G sensor 17. Estimate β. The pitch coefficient setting unit 46 sets the pitch coefficient Kp (Kpfl, Kpfr) of the vehicle body 2 based on the longitudinal acceleration Gx input from the longitudinal G sensor 18.

  On the other hand, the yaw rate difference calculation unit 47 calculates a difference (yaw rate difference Δγ) between the target yaw rate γtgt input from the target yaw rate setting unit 43 and the actual yaw rate γ input from the yaw rate sensor 19. The side slip angle difference calculating unit 48 calculates a difference (side slip angle difference Δβ) between the target side slip angle βtgt input from the target side slip angle setting unit 44 and the actual side slip angle β input from the actual side slip angle estimating unit 45. The virtual lateral force setting unit 49 sets a virtual lateral force F to be applied to the vehicle body 2 and an applied force point η based on the yaw rate difference Δγ and the side slip angle difference Δβ. Then, the control amount setting unit 50 sets / outputs the control amounts of the steering ECU 32 and the hydraulic unit 33 based on the setting result of the virtual lateral force setting unit 49, the acceleration / deceleration coefficient Ka, and the pitch coefficient Kp.

<< Operation of Embodiment >>
When the automobile 1 starts traveling, the wheel motion control device 40 repeats wheel motion control whose procedure is shown in the flowchart of FIG. 3 at a predetermined control interval (for example, 10 ms) based on the detection signals of the sensors 15 to 19. Execute.

  When the wheel motion control is started, the wheel motion control device 40 estimates the vehicle speed v in step S1 of FIG. 3 based on the wheel speeds Wfl, Wfr, Wrl, Wrr. Next, the wheel motion control device 40 sets the target yaw rate γtgt and the target skid angle βtgt in step S2 based on the vehicle speed v and the steering angle δ. Next, the wheel motion control device 40 estimates the actual skid angle β in step S3 based on the vehicle speed v, the steering angle δ, the actual yaw rate γ, and the lateral acceleration Gy.

Next, the wheel motion control device 40 calculates the difference between the target yaw rate γtgt and the actual yaw rate γ as the yaw rate difference Δγ in step S4, and calculates the difference between the target side slip angle βtgt and the actual side slip angle β as the side slip angle difference Δβ. To do. Thereafter, in step S5, the wheel motion control device 40, based on the mass m, the vehicle speed v, the yaw rate difference Δγ, and the side slip angle difference Δβ of the vehicle 1, uses the virtual lateral force F to be applied to the vehicle body 2 using equation (1). Set.
F = mv · (Δγ + Δβ) (1)

Next, in step S6, the wheel motion control device 40 applies the applied force point of the virtual lateral force F using equation (2) based on the inertia moment I, the yaw rate difference differential value Δγ ′, and the virtual lateral force F of the vehicle 1. η is calculated. The applied force point η is a point to which the virtual lateral force F should be applied, and is represented as a front-rear position with respect to the center of gravity G of the automobile 1 (a forward value from the center of gravity G is a positive value) as shown in the two-wheel model of FIG. The
η = I · Δγ '/ F (2)

Next, the wheel motion control device 40 determines whether or not the value of the force point η is greater than the value of the front shaft position (the position of the front wheel 3f) Lf in step S7. When this determination is Yes (that is, when the applied force point η is positioned forward of the front wheel 3f as shown in FIG. 4), the wheel motion control device 40 determines the applied force point η in step S8. The braking moment Mb is calculated using the formula (3) together with the front shaft position Lf (η = Lf). Here, the braking moment Mb is a moment obtained by operating the brakes 6 of the respective wheels 3 when the virtual lateral force F cannot be applied to the applied force point η only by the steering control.
Mb = (η−Lf) · F (3)

On the other hand, if the determination in step S7 is No, the wheel motion control device 40 determines whether or not the value of the force point η is smaller than the value of the rear axle position (rear wheel position: negative value) Lr in step S9. Determine. When this determination is Yes (that is, when the applied force point η is located behind the rear wheel 3r), the wheel motion control device 40 sets the applied force point η as the rear axle position Lr in step S10. Along with (η = Lr), the braking moment Mb is calculated using the equation (4).
Mb = (Lr−η) · F (4)

  On the other hand, when the determination in step S9 is also No (that is, when the applied force point η is located between the front wheel 3f and the rear wheel 3r), the wheel motion control device 40 uses the virtual lateral force F only by steering control. Therefore, the braking moment Mb is set to 0 in step S11.

Next, in step S12, the wheel motion control device 40 uses the equations (5) and (6) to distribute the steering control portion of the virtual lateral force F to the front and rear wheels 3f and 3r of the two-wheel model. A force total value Ffy and a rear wheel lateral force total value Fry are calculated.
Ffy = (Lr + η) / (Lf + Lr) · F (5)
Fry = (Lf−η) / (Lf + Lr) · F (6)

Next, the wheel motion control device 40 uses the equations (7) to (10) to distribute the front wheel lateral force total value Ffy and the rear wheel lateral force total value Fry to each wheel 3 in step S13. The forces Ffly to Fry are calculated. Note that Krfl is a roll distribution coefficient to the left front wheel 3fl, and Krrl is a roll distribution coefficient to the left rear wheel 3rl.
Ffly = Ffy · Krfl (7)
Ffly = Ffy · (1−Krfl) (8)
Frly = Fry · Krrl (9)
Fry = Ffy · (1−Krrl) (10)

Next, in step S14, the wheel motion control device 40 uses the expressions (11) and (12) to distribute the braking moment Mb to the left and right wheels 3l and 3r, and the left wheel longitudinal force total value Flx and the right wheel longitudinal force. A total value Frx is calculated. Here, d is a tread and is the same in the front and rear in the case of the present embodiment. The acceleration / deceleration coefficient Ka is 0.5 during constant speed traveling, and increases or decreases during acceleration / deceleration traveling.
Flx = (Mb / (d / 2)) · Ka (11)
Frx = (Mb / (d / 2)). (1-Ka) (12)

Next, in step S15, the wheel motion control device 40 uses the equations (13) to (16) to distribute the left wheel longitudinal force total value Flx and the right wheel longitudinal force total value Frx to each wheel 3. The longitudinal forces Fflx to Frrx of the wheel 3 are calculated. In equations (13) to (16), Kpfl is the pitch coefficient for the left front wheel 3fl, and Kpfr is the pitch coefficient for the right front wheel 3fr.
Fflx = Flx · Kpfl (13)
Ffrx = Frx · Kpfr (14)
Frlx = Flx · (1−Kpfl) (15)
Frrx = Frx · (1−Kpfr) (16)

  In this embodiment, since the steering amount and the braking amount are calculated based on the virtual lateral force F and the applied force point η, the size of the friction circle and the grip margin are calculated as compared with the conventional device that calculates each wheel 3 individually. Processing can be performed in a very short time, and it is possible to respond to changes in road surface conditions and the like with relatively high speed and high accuracy, and it is possible to employ a relatively low cost wheel motion control device 40. When the applied force point η is located between the front wheel 3f and the rear wheel 3r (that is, when the virtual lateral force F is applied only by the steering control), the braking moment Mb is not set (for each wheel 3). Therefore, the decrease in the vehicle speed v is suppressed and the driver does not feel an unnecessary deceleration.

  Although the description of the specific embodiment is finished as described above, the present invention is not limited to the embodiment and can be widely modified. For example, in the above embodiment, the present invention is applied to an automobile in which front and rear wheels are respectively steered by a steering actuator and each wheel is individually braked by a hydraulic unit. However, only the front wheels are steered. The present invention can also be applied to an automobile equipped with a drive control device that individually drives each wheel, an automobile equipped with a normal braking device, and the like. Also, it may be provided with a failure handling means that prevents the force point from moving forward from the center of gravity when the rear wheel side steering actuator fails, thereby reconstructing the control law at the time of failure, etc. No action is required. In addition to the specific configurations of the automobile and the wheel motion control device, the specific control procedures and the like can be changed as appropriate without departing from the spirit of the present invention.

It is a top view which shows the apparatus structure of the motor vehicle which concerns on embodiment. It is a block diagram which shows schematic structure of VSA-ECU which concerns on embodiment. It is a flowchart which shows the procedure of the wheel motion control which concerns on embodiment. It is a two-wheel model which shows the effect | action of embodiment.

Explanation of symbols

1 Automobile (vehicle)
2 Car body 3 Wheel 6 Brake (longitudinal force addition means)
8 Front wheel steering mechanism (wheel steering means)
9l Left rear wheel steering mechanism (wheel steering means)
9r Right rear wheel steering mechanism (wheel steering means)
19 Yaw rate sensor (actual behavior acquisition means)
31 VSA-ECU
32 Steering ECU
33 Hydraulic unit 40 Wheel motion control device (wheel motion control means)
41 vehicle speed estimation unit 42 acceleration / deceleration coefficient setting unit 43 target yaw rate setting unit (target behavior setting means)
44 Target skid angle setting section (target behavior setting means)
45 Actual skid angle estimator (actual behavior acquisition means)
46 Pitch coefficient setting unit 47 Yaw rate difference calculating unit 48 Side slip angle difference calculating unit 49 Virtual lateral force setting unit (virtual lateral force setting means)
50 Control amount setting part

Claims (4)

A target behavior setting means for setting a target behavior of the vehicle based on at least one of the driving operation of the driver and the traveling state of the vehicle;
Actual behavior acquisition means for detecting or estimating the actual behavior of the vehicle based on the motion state quantity of the vehicle;
Virtual lateral force setting means for setting a virtual lateral force to be applied to the vehicle and an applied force point based on a difference between the target behavior and the actual behavior;
A vehicle behavior control device comprising wheel motion control means for controlling wheel motion based on a setting result of the virtual lateral force setting means. The vehicle includes wheel turning means for turning the wheel,
2. The vehicle behavior control device according to claim 1, wherein the wheel motion control means controls driving of the wheel steering means. The vehicle includes a longitudinal force adding means for braking or driving the wheels,
The vehicle behavior control device according to claim 1 or 2, wherein the wheel motion control means controls the driving of the longitudinal force adding means. When the vehicle is provided with the wheel steering means,
4. The vehicle behavior control device according to claim 3, wherein the wheel motion control means drives and controls the wheel steering means with priority over the longitudinal force adding means.

Images