JP2007210392A - Driving force distribution device of four-wheel independent drive vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance the driving effectiveness by establishing accurately the target vehicle behavior of a four-wheel independent drive vehicle. <P>SOLUTION: A controller 8 decides the target values of the vehicle fore-and-aft direction force, yawrate, and yaw moment, sets the fundamental values of the driving force distribution to different wheels which accomplishes the target values approximately, calculates the vehicle fore-and-aft direction force and yaw moment achieved by these fundamental values, and calculates the correction amount of the vehicle fore-and-aft direction force and the first correction amount of the yaw moment from the difference between the values achieved by the fundamental values and the target values. It also calculates the yawrate achieved by the target values of the driving force distribution to different wheels, and determines the second correction value of the yaw moment in such a direction as lessening the error of the calculated value from the target value of yawrate. The controller calculates the correction values of the driving force distribution to different wheels which accomplish the correction amount of the yaw moment and the correction amount of the vehicle fore-and-aft direction force using the sum of the first and second correction values as a yaw moment correction value, and sets the sum of the calculated correction amount and the fundamental values of the driving force distribution to the target values of the driving force distribution to different wheels. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a driving force distribution control of a four-wheel independent drive vehicle that can independently control and drive left and right wheels.

  In a four-wheel independent drive vehicle, if there is an error between the target yaw moment and the actual yaw moment determined according to the driver's operation due to disturbances such as crosswinds or changes in vehicle weight, this error should be reduced. Japanese Patent Application Laid-Open No. H10-228688 discloses a technique for providing a difference in driving force between left and right wheels.

  According to the technique described in Patent Document 1, the error between the target value of the yaw moment and the actual value can be reduced. However, the lateral force and yaw moment of the vehicle may change due to a change in the tire lateral force of the wheel that generates the driving force difference, which may reduce steering stability.

  In view of this, the applicant, in a vehicle that independently drives four wheels, considers the nonlinear relationship between the driving force and the tire lateral force, and targets the vehicle behavior (vehicle longitudinal force, vehicle lateral force, yaw moment). We have proposed a technology that uses feed-forward to determine the driving force distribution for each wheel that achieves this value.

  In this technique (hereinafter referred to as “prior art”), the driving force distribution of each wheel is obtained in the following procedure.

First, linear approximation is applied to the driving force distribution Fx _i ^## (i = 1 to 4) that substantially achieves the target values Fx ^** , Fy ^** , and M ^** of the vehicle longitudinal force, vehicle lateral force, and yaw moment. It is obtained by using the inverse model of the vehicle model.

Next, a vehicle model in which the vehicle longitudinal force Fx ^## , vehicle lateral force Fy ^## , and yaw moment M ^## realized by this Fx _i ^## are considered in a nonlinear relationship between driving force and tire lateral force. To obtain the differences ΔFx, ΔFy, ΔM between Fx ^** , Fy ^** , M ^** and Fx ^## , Fy ^## , M ^## .

Finally, the driving force correction amount ΔFx _i for each wheel that corrects ΔFx, ΔFy, ΔM is obtained using the sensitivity of the tire lateral force with respect to the driving force change of each wheel, and the like, and ΔFx _i and Fx _i ^## Is set as the target value Fx _i ^** of the driving force distribution of each wheel.
Japanese Patent Laid-Open No. 5-221300

In the prior art as a driving force correction amount DerutaFx _i of each wheel is sufficient small, (driving force and the tire lateral as the tire lateral force that varies in proportion to the driving force when changing the driving force by this DerutaFx _i non-linear relationship between the force as can be approximated as linear) seeking the correction ΔFx _i.

However, since the correction amount ΔFx _i is not infinitely small, the obtained target value Fx _i ^** of the driving force distribution of each wheel is the target value F _x ^{** of the} vehicle longitudinal force, vehicle lateral force, and yaw moment. , Fy ^** and M ^** cannot be strictly realized and an error occurs.

  An example of the transition of the yaw moment and the yaw rate when the control according to the prior art is performed is shown in FIG. FIG. 15 shows time on the horizontal axis, the upper diagram shows the yaw moment on the vertical axis, and the lower diagram shows the yaw rate on the vertical axis. In FIG. 15, the target values of the yaw moment and yaw rate are indicated by broken lines, and the response when control is performed using the above-described prior art is indicated by solid lines.

  In the upper diagram, the above-described error exists between the target value of yaw moment and the response. Since the yaw rate is a value obtained by dividing the yaw moment by the yaw inertia moment of the vehicle and integrated, this error is accumulated and an error occurs between the yaw rate and the target value as shown in the lower diagram.

  In the above prior art, a target value is not set for the yaw rate γ, but there is a relationship of the formula (1) between the yaw rate γ of the vehicle and the centripetal acceleration Yα. In the formula (1), V is the vehicle speed, and β ′ is a differential value of the vehicle slip angle β.

  Since the centripetal acceleration Yα is substantially equal to the vehicle lateral force when the vehicle side slip angle β is sufficiently small, if an error from the target value occurs in the yaw rate γ, an error occurs in the vehicle lateral force or the like. In an attempt to compensate for the lateral force error, β ′ in equation (1) becomes excessive, and the vehicle behavior may become unstable.

  The present invention has been made in view of this problem, and an object of the present invention is to achieve a target vehicle behavior with higher accuracy and to improve the drivability of the vehicle.

  The driving force distribution device for a four-wheel independent drive vehicle according to the present invention determines the target values of the vehicle longitudinal force, yaw rate, and yaw moment based on the driving state of the vehicle, and substantially distributes the driving force distribution of each wheel. The vehicle longitudinal force and yaw moment realized by the basic value of driving force distribution, and the vehicle longitudinal force realized by the target value of the vehicle longitudinal force and basic value of driving force distribution. The vehicle front-rear direction force correction amount is calculated from this difference, and the yaw moment first correction amount is calculated from the difference between the yaw moment target value and the yaw moment realized by the basic value of the driving force distribution.

  Further, the yaw rate realized by the target value of the driving force distribution of each wheel is calculated, the error between the target value of the yaw rate and the calculated yaw rate is calculated, and the second correction of the yaw moment is performed in a direction to reduce the yaw rate error. Find the amount.

  Then, the yaw moment correction amount calculated by the sum of the first correction amount and the second correction amount of the yaw moment and the correction amount of the driving force distribution of each wheel that realizes the correction amount of the vehicle longitudinal force are calculated. The target value of the driving force distribution of each wheel is set to the sum of the basic value of the driving force distribution and the correction amount of the driving force distribution, and the driving force of each wheel is independently controlled according to the target value of the driving force distribution.

  By using the present invention, the yaw rate of the vehicle can be made to follow the target value, so that the target vehicle behavior can be realized with higher accuracy and the drivability of the vehicle can be expected to improve.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  First, the outline | summary and effect of this invention are demonstrated, Then, embodiment which applied this invention to the electric vehicle is described.

1. Summary and Effects of the Invention (1) The invention described in claim 1 (hereinafter referred to as “first invention”).
An example of a control system for a four-wheel independent drive vehicle based on the first invention is shown in FIG. The processing of each block (A) to (H) in FIG. 1 is as follows. Detailed specific examples of each process will be described later in “2. Embodiment of the present invention”.

In the block (A), the vehicle front-rear direction force, the vehicle lateral direction are determined based on the driver's operation (accelerator pedal depression amount AP, brake pedal depression amount BP, steering rotation angle θ, etc.) and the measured vehicle speed V. The target values Fx ^** and M ^** for the directional force and yaw moment are set, and the target value γ ^** for the yaw rate γ is set.

In the block (B), an inverse model of a vehicle model that linearly approximates the driving force distribution Fx _i ^## (i = 1 to 4) that substantially realizes the target values Fx ^** , M ^** , and γ ^** is used. Ask.

In the block (C), the vehicle longitudinal force Fx ^## and yaw moment M ^## realized by this Fx _i ^## are calculated using a vehicle model considering a non-linear relationship between the driving force and the tire lateral force. . The vehicle model block (C) calculates the Fx ^{# #,} M ^{# #} from the block state quantity of the vehicle determined in (E) (wheel load W _i and slip angle beta _i of each wheel).

In the block (D), the vehicle front-rear direction force correction amount ΔFx and yaw moment correction amount ΔM (No. 1) are calculated from the difference between the vehicle behavior target values Fx ^** and M ^** and the estimated Fx ^## and M ^## . 1 correction amount).

The block (E) is a vehicle model that takes into account the nonlinear relationship between the driving force and the tire lateral force, as in the block (C), and the current value of the driving force distribution target value Fx _i ^** and the vehicle speed V are input. The vehicle state quantity such as the yaw rate γ is calculated.

In the block (F), a yaw moment correction amount DM (second correction amount) for compensating for an error Δγ between the yaw rate γ determined in the block (E) and the target value γ ^** set in the block (A). Ask.

In the block (G), the driving force correction amount ΔFx _i of each wheel that realizes the correction amounts ΔFx, ΔM + DM is obtained by using the sensitivity of the tire lateral force with respect to the driving force change of each wheel. Incidentally, the sensitivity or the like of the tire lateral force is determined from the drive force distribution Fx _i ^{# #} a block state quantity of the vehicle determined in (E) (wheel load W _i and slip angle beta _i of each wheel). Finally, the sum of the correction amount ΔFx _i and Fx _i ^## obtained in the block (B) is set as the target value Fx _i ^** for the driving force distribution of each wheel.

Thus, by setting the target value Fx _i ^** of the driving force distribution of each wheel and controlling the driving force of each wheel according to this, the error from the target value of the yaw rate γ in the lower part of FIG. Since it can be set to 0, the drivability of the vehicle can be improved.

(2) Invention of Claim 2 (hereinafter referred to as “second invention”)
The second invention proposes a technique for realizing the target vehicle behavior with high accuracy and improving the drivability of the vehicle by reducing the error from the target value of the side slip angle β of the vehicle in the same manner as the first invention. Is.

  An example of a control system for a four-wheel independent drive vehicle based on the second invention is shown in FIG. The processing of each block (A) ′ to (H) ′ in FIG. 2 is as follows. Detailed specific examples of each process will be described later in “2. Embodiment of the present invention”.

In the block (A) ′, the vehicle longitudinal force, the vehicle, based on the driver's operation (accelerator pedal depression amount AP, brake pedal depression amount BP, steering rotation angle θ, etc.) and the measured vehicle speed V, etc. The side slip angle target values Fx ^** and β ^** are set, and β ′ ^** obtained by time differentiation of the target value of the vehicle side slip angle is set.

In the block (B) ′, an inverse model of the vehicle model that linearly approximates the driving force distribution Fx _i ^## (i = 1 to 4) that substantially realizes the target values Fx ^** , β ^** , and β ′ ^**. Use to find out.

In the block (C) ′, the vehicle longitudinal force Fx ^## realized by this Fx _i ^## and β ′ ^## which is a time derivative of the target value of the side slip angle of the vehicle are expressed in a nonlinear manner between the driving force and the tire lateral force. Calculation is performed using a vehicle model that considers the relationship. The vehicle model of block (C) ′ calculates Fx ^## and β ′ ^## from the vehicle state quantities (wheel load W _{i of} each wheel, side slip angle β _i, etc.) obtained in block (E) ′. To do.

In the block (D) ′, the vehicle front-rear direction force correction amount ΔFx and the differential value of the vehicle body slip angle are calculated based on the difference between the vehicle behavior target values Fx ^** and β ′ ^** and the estimated Fx ^## and β ′ ^##. A correction amount Δβ ′ is obtained.

Block (E) 'is a vehicle model that takes into account the nonlinear relationship between driving force and tire lateral force, as in block (C)', and inputs the target value Fx _i ^** and vehicle speed V for the driving force distribution of each wheel. As described above, the vehicle state quantity such as the current vehicle side slip angle β is calculated.

In the block (F) ′, an error Δβ between the vehicle slip angle β obtained in the block (E) ′ and the target value β ^** set in the block (A) ′ is obtained, and this error Δβ and the correction amount Δβ ′ are obtained. The vehicle lateral force correction amount DFy is compensated for.

In the block (G) ′, the driving force correction amount ΔFx _i for each wheel realizing the correction amount ΔFx and the correction amount DFy is obtained by using the sensitivity of the tire lateral force with respect to the driving force change of each wheel. Incidentally, the sensitivity, etc. of the tire lateral force is determined from the drive force distribution Fx _i ^{# #} a block (E) state of the vehicle determined by '(wheel load W _i and slip angle beta _i of each wheel). Finally, the sum of the correction amount ΔFx _i and Fx _i ^## obtained in the block (B) ′ is set as a target value Fx _i ^** for driving force distribution of each wheel.

Thus, by setting the target value Fx _i ^** of the driving force distribution of each wheel and controlling the driving force of each wheel according to this, the error from the target value of the side slip angle β of the vehicle can be reduced. As with the first invention, the target vehicle behavior can be realized with high accuracy.

(3) The invention according to claim 3 (hereinafter referred to as “third invention”).
The third invention proposes a technique for realizing the target vehicle behavior with higher accuracy than the first and second inventions by reducing the error between the yaw rate γ and the side slip angle β of the vehicle. is there.

  An example of a control system for a four-wheel independent drive vehicle based on the third invention is shown in FIG. The processing of each block (A) "to (H)" in FIG. 3 is as follows. Detailed specific examples of each process will be described later in “2. Embodiment of the present invention”.

In block (A) ", the vehicle longitudinal force, yaw based on the driver's operation (accelerator pedal depression amount AP, brake pedal depression amount BP, steering rotation angle θ, etc.) and the measured vehicle speed V, etc. The target values Fx ^** , M ^** , and β ^** of the moment and the side slip angle of the vehicle are set, respectively, and the target value γ ^** of the yaw rate γ and the target value of the side slip angle of the vehicle are time-differentiated β ′ ^* Set ^* .

In the block (B) ", the driving force distribution Fx _i ^## (i = 1 to 4) that substantially realizes the target values Fx ^** , M ^** , γ ^** , β ^** , and β ′ ^** is linear. This is obtained using an inverse model of the approximate vehicle model.

In block (C) ", the Fx _i ^## vehicle longitudinal direction force Fx ^## realized by the yaw moment M ##, the target value time slip angle of the vehicle obtained by differentiating the beta 'driving the ^## force the tire Calculation is performed using a vehicle model that takes into account a nonlinear relationship with the lateral force.The vehicle model of the block (C) "is the vehicle state quantity (wheel load W _{i of} each wheel) obtained in the block (E)". Fx ^## , M ^## , β ′ ^## are calculated from the side slip angle β _{i and the} like.

In the block (D) ", the vehicle longitudinal force correction amount is calculated from the difference between the vehicle behavior target values Fx ^** , M ^** , β ' ^** and the estimated Fx ^## , M ^## , β'^##. ΔFx, yaw moment correction amount ΔM (first correction amount), and vehicle body side slip angle differential value correction amount Δβ ′ are obtained.

Block (E) "is a vehicle model that takes into account the non-linear relationship between driving force and tire lateral force like block (C)", and inputs the target value Fx _i ^** and vehicle speed V for the driving force distribution of each wheel. As described above, vehicle state quantities such as the current vehicle yaw rate γ and side slip angle β are calculated.

In the block (F) ", errors Δγ and Δβ between the yaw rate and the sideslip angles γ and β of the vehicle obtained in the block (E)" and the target values γ ^** and β ^** set in the block (A) "are calculated. Then, a yaw moment correction amount DM (second correction amount) for compensating the error Δγ is obtained, and a vehicle lateral force correction amount DFy for compensating the error Δβ and the correction amount Δβ ′ is obtained.

In the block (G) ", the driving force correction amount ΔFx _i of each wheel that realizes the correction amounts ΔFx, ΔM + DM, and DFy is obtained by using the sensitivity of the tire lateral force to the driving force change of each wheel, etc. Is obtained from the vehicle state quantity (wheel load W _{i of} each wheel, side slip angle β _i, etc.) and driving force distribution Fx _i ^## obtained in block (E) ". Finally, the sum of the correction amount ΔFx _i and Fx _i ^## obtained in the block (B) ″ is set as the target value Fx _i ^** of the driving force distribution of each wheel.

Thus, by setting the target value Fx _i ^** of the driving force distribution of each wheel and controlling the driving force of each wheel accordingly, the error between the yaw rate γ and the side slip angle β of the vehicle can be reduced. The target vehicle behavior can be realized with higher accuracy than the first and second inventions.

2. Embodiment of the Present Invention FIG. 4 is a block diagram showing an example of the mechanical configuration of an electric vehicle to which the present invention is applied. The electric vehicle shown in FIG. 4 has a left front wheel 1 by a motor 11 driven by electric power supplied from a battery 9, a right front wheel 2 by a motor 12, a left rear wheel 3 by a motor 13, and a right rear wheel by a motor 14. 4 are driven independently.

  The motors 11 to 14 are AC machines capable of powering operation and regenerative operation such as a three-phase synchronous motor and a three-phase induction motor, and the battery 9 is a nickel hydrogen battery or a lithium ion battery. The inverters 31 to 34 convert the alternating current generated by the motors 1 to 4 into a direct current and charge the battery 9, or convert the direct current discharged by the battery 9 into an alternating current and supply the alternating current to the motors 1 to 4. The speed of each wheel is detected by the wheel speed sensors 11 to 14, and the detected rotation speed of each wheel is transmitted to the controller 8.

  The rotation radii of the wheels 1 to 4 are all equal to R, and the reduction ratio is 1, that is, the motors and the wheels are directly connected. Furthermore, when the wheel load, the side slip angle, and the road surface friction coefficient are the same for the four wheels, the relationship between the driving force and the tire lateral force is the same for the four wheels, that is, the four wheels have the same tire characteristics.

  The lateral acceleration of the vehicle is detected by the acceleration sensor 100 attached to the center of gravity of the vehicle, the yaw rate of the vehicle is detected by the yaw rate sensor 101, and the detected lateral acceleration and yaw rate of the vehicle are transmitted to the controller 8.

  The steering angles of the front wheels 1 and 2 are mechanically adjusted via the steering gear 15 by the steering of the steering 5 by the driver. The steering angle change amount of the front wheels 1 and 2 is set to be 1/16 of the steering angle change amount of the steering 5. The steering angles of the wheels 1 to 4 are detected by the steering angle sensors 41 to 44, and the detected steering angles of the wheels are transmitted to the controller 8.

  The rotation angle θ of the steering 5 by the driver is detected by the steering angle sensor 25, and the depression amount AP of the accelerator pedal 6 and the depression amount BP of the brake pedal 7 are detected by the accelerator stroke sensor 26 and the brake stroke sensor 27, respectively, and transmitted to the controller 8. Is done.

  The controller 8 includes a CPU, a ROM, a RAM, an interface circuit, an inverter circuit, and the like, and is detected by wheel speed sensors 21 to 24, a steering angle sensor 25, an accelerator stroke sensor 26, a brake stroke sensor 27, an acceleration sensor 100, a yaw rate sensor 101, and the like. The received signals are received, and control such as distributing torque to the motors 1 to 4 is performed based on these signals.

  Next, the control contents of the controller 8 will be described.

  The flowchart of FIG. 5 shows the torque distribution control to the motors 1 to 4 executed by the controller 8 in the electric vehicle of FIG.

  Steps S10 to S40 are processes corresponding to the block (A) in FIG. 1, the block (A) ′ in FIG. 2, and the block (A) ″ in FIG.

  First, in step S10, the rotational speeds ω1, ω2, ω3, and ω4 (unit: rad / s) of the wheels 1 to 4 are detected by the wheel speed sensors 21 to 24, respectively, and multiplied by the radius R of each wheel. Speeds V1, V2, V3, and V4 (unit: m / s) are obtained, and the vehicle speed V (unit: m / s) is obtained by equation (2).

Further, the accelerator stroke sensor 26 and the brake stroke sensor 27 detect the depression amount AP (unit:%) of the accelerator pedal 6 and the depression amount BP (unit:%) of the brake pedal 7, respectively. The rotation angle θ (unit: rad) is detected, and the steering angles δ ₁ , δ ₂ , δ ₃ , and δ ₄ of the wheels 1 to 4 are detected by the steering angle sensors 41 to 44. V and V1 to V4 are positive in the vehicle forward direction, and the rotation angle θ of the steering 5 is positive in the counterclockwise direction.

In a vehicle that does not have a steering angle sensor, the steering angle of each wheel is obtained from the rotation angle θ of the steering 5. For example, in a vehicle that can steer only the front wheels, the steering angles δ ₁ and δ ₂ of the front wheels ₁ and ₂ are set to δ ₁ = δ ₂ = θ / 16, and the steering angles δ ₃ and δ ₄ of the rear wheels 3 and ₄ are set to δ _3. = Δ ₄ = 0. In such a case, it is preferable that the steering angle of each wheel can be corrected in consideration of the influence of the suspension such as compliance steer and roll steer.

In step S20, the static target value Fx ^* (unit: N) of the vehicle longitudinal force is obtained from the expression (3) based on the depression amount AP of the accelerator pedal 6, the depression amount BP of the brake pedal 7, and the vehicle speed V. .

In Formula (3), Fa _x ^* is a value obtained by referring to the target driving force map based on the depression amount AP of the accelerator pedal 6 and the vehicle speed V, and Fb _x is based on the depression amount BP of the brake pedal 7. The value obtained by referring to the target braking force map. The target driving force map and the target braking force map are set as shown in FIGS. 6 and 7, for example. Further, Fx, Fa _x ^*, both Fb _x ^* to the direction to accelerate the vehicle in front is positive.

In step S30, the static target value β ^* (unit: rad) of the side slip angle of the vehicle is referred to the target vehicle side slip angle map based on Fx ^* , the rotation angle θ of the steering 5 and the vehicle speed V set in step S20. And set. Also, the static target value γ ^* (unit: rad / s) of the yaw rate is set with reference to the target yaw rate map based on Fx ^* , θ, and V. The target vehicle side slip angle map and the target yaw rate map are maps set, for example, as shown in FIGS. 8 and 9, respectively. A method for setting these two maps will be described in step S40 described later. The yaw rate is positive in the counterclockwise direction when the vehicle is viewed from above, and the side slip angle of the vehicle is positive in the case where the angle from the vehicle front-rear direction to the vehicle speed direction is counterclockwise as viewed from above. .

In step S40, the dynamic target value F _x ^{** of} the vehicle longitudinal force, the dynamic target value β ^** of the vehicle side slip angle, and the dynamic target value γ ^** of the yaw rate can be realized by distributing the driving force of each wheel. In order to make the driver's maneuverability suitable within a certain range, it is obtained by adding a time delay element to the static target values Fx ^* , β ^* , γ ^* . Here, Fx ^** , β ^** , and γ ^** are obtained by using a second-order lag transfer function for Fx ^* and corresponding transfer functions for β ^* and γ ^* . In particular, the response of β ^** and γ ^** includes a time delay element that can be realized for each driving condition.

In step S40, the dynamic target value M ^** of the yaw moment and β ′ ^** obtained by time differentiation of the dynamic target value of the vehicle slip angle are also obtained. For the dynamic target value M ^** of yaw moment, the transfer function obtained by multiplying the transfer function of the time delay element used to obtain γ ^** by the derivative element is entered in γ ^* , and the yaw moment of inertia I of the vehicle is further calculated. Multiply to find. For β ' ^**, which is the time derivative of the dynamic target value of the vehicle side slip angle, find the transfer function obtained by multiplying the transfer function of the time delay element used to calculate β ^** by the derivative element into β ^* .

Moreover, in step S40, the dynamic target value Fy ^** of the vehicle lateral force is obtained by equation (4).

  The next steps S50 to S60 are processes corresponding to the block (B) in FIG. 1, the block (B) ′ in FIG. 2, and the block (B) ”in FIG.

At step S50, driving the static target value of the force distribution _{^{Fx 1 *, Fx 2 *,}} Fx 3 *, the Fx ₄ ^*, θ, V, with reference to the static driving force distribution map based on Fx ^* Configuration To do. The static driving force distribution map is set as shown in FIGS. 10a and 10b, for example.

  Here, how to obtain the static driving force distribution map (FIGS. 10a and 10b) and the target vehicle side slip angle map (FIG. 8) and the target yaw rate map (FIG. 9) used in step S30 will be described.

First, the four wheel driving force sum Fx _all (unit: N), left and right wheel driving force difference ΔFx _all (unit: N), front wheel driving force distribution η (unit: none), left and right wheel driving force difference front wheel distribution Δη ( (Unit: none) is defined as in equations (5) to (8). Here, η and Δη are always set to 0.6 (allocation to the front wheels is 60%).

Then, the following simulations or experiments are performed for all combinations of four parameters of Fx _all , ΔFx _all , the rotation angle θ of the steering wheel 5, and the static target value Fx ^* of the vehicle longitudinal force that can be taken by the vehicle. A static driving force distribution map, a target vehicle lateral force map, and a target yaw rate map are created.

First, the driving force distribution Fx _i of each wheel is obtained from the selected Fx _all and ΔFx _all by the equations (9) to (12), and the steering angles of the front wheels 1 and 2 are calculated from the selected θ ′ by δ ₁ = It is assumed that δ ₂ = θ ′ / 16 (the steering gear ratio is 1/16).

Next, the vehicle is driven with the set driving force distribution Fx _i and the front wheel steering angles δ ₁ and δ ₂ (the steering angles δ ₃ and δ ₄ of the rear wheels 3 and ₄ are 0), and −Fx ^{* is set} to the vehicle. It is added in the vehicle longitudinal direction at the position of the center of gravity. Then, the vehicle side slip angle β and yaw rate γ when the vehicle speed V ′ becomes constant (steady state) after a sufficient time has elapsed are obtained. In this experiment or simulation, the running resistance elements such as air resistance and rolling resistance are excluded, and in the case of simulation, non-linearity such as driving force of each wheel and tire lateral force. This is done using a vehicle model that fully considers performance.

Then, static driving force distribution map, the target vehicle slip angle map, the target yaw rate map of ^{V, θ, Fx *, β} *, γ *, V when the Fx _i ^*, which each carried out now simulation ', θ, Assuming that Fx ^* , β, γ, and Fx _i , a static driving force distribution map, a target vehicle lateral force map, and a target yaw rate map are set.

In step S60, based on the static target value Fx _i ^* of the driving force distribution set in step S40, the driving force distribution that substantially realizes the dynamic target values Fx ^** , Fy ^** , γ ^** of the vehicle behavior. Fx ₁ ^## , Fx ₂ ^## , Fx ₃ ^## , and Fx ₄ ^{## of the above} are obtained by equations (13) to (16).

However, as shown in step S40, η = Δη = 0.6, and Fx _all ^## is a time delay element included in Fx ^* when the dynamic target value Fx ^** of the vehicle longitudinal force is obtained in step S50. Is obtained by putting the value into the sum Fx ₁ ^* + Fx ₂ ^* + Fx ₃ ^* + Fx ₄ ^* of Fx _i ^* .

In addition, ΔFx _all ^## is a linear two-wheel model that approximates the vehicle linearly (“Motion and Control of Cars”, Chapter 3 Section 3.2.1, (Author) Masato Abe, (Publishing) Sankaido) Considering the case where a driving force difference ΔFx _all ^## is added, model following control designed so that the response of the yaw rate of this linear two-wheel model is γ ^** (“Vehicle Control”, Chapter 3, Section 3.2, Authors: Kimio Kanai, Tokumasa Ochi, Taketoshi Kawabuchi, Publisher: Kashiwa Shoten) and corrected to avoid deviations from the static target value Fx _i ^* of the driving force distribution in the steady state Obtained from (17).

However,

In the equation (17), fr (s) is a transfer function of a time delay element entered in the static target value γ ^* when obtaining the dynamic target value γ ^** of the yaw rate in step S50, I (unit: kg · m ² ) is the yaw moment of inertia of the vehicle, and Kf and Kr (unit: N / rad) are the cornering forces per unit side slip angle when the side slip angles of the front and rear wheels are sufficiently small.

  Lf is the distance from the vehicle center of gravity position to the front wheel axle (unit: m), Lr is the distance from the vehicle center of gravity position to the rear wheel axle in the yaw rotation direction (unit: m), and Lt is the tread length of the front and rear wheels (unit: m). Unit: m), Ll is the wheelbase length (unit: m), Ll = (Lf + Lt), and m is the mass of the vehicle (unit: kg).

Further, in Expression (17), ΔFx _all ^## is obtained so that the response of the yaw rate of the linear two-wheel model becomes γ ^** . In particular, when the second and third inventions are applied, the vehicle ΔFx _all ^## may be obtained by equation (19) using model following control so that the response of the side slip angle becomes β ^** .

However, in the equation (19), fβ (s) is a transfer function of a temporal delay element that is included in the static target value β ^* when the dynamic target value β ^** of the vehicle slip angle is obtained in step S50.

  The next step S70 is processing corresponding to the (E) block in FIG. 1, the (E) ′ block in FIG. 2, and the (E) ″ block in FIG.

In step S70, the yaw rate γ (unit: rad / s), which is the state quantity of the vehicle, from the target value Fx _i ^** of the driving force distribution of each wheel obtained in step S110 described later and the vehicle speed V obtained in step S10. The vehicle side slip angle β (unit: rad), the wheel load W _i (unit: N) of each wheel, and the side slip angle β _i (unit: rad) of each wheel are calculated. The calculation method is performed according to the flowchart of FIG. The sign of β _i is positive when the angle from the front-rear direction of the wheel to the direction of the wheel speed is counterclockwise as viewed from vertically above.

  The next step S80 is processing corresponding to the block (C) in FIG. 1, the block (C) 'in FIG. 2, and the block (C) "in FIG.

At step S80, driving force basic value Fx ₁ ^{# # _{distribution, Fx 2 ##, Fx 3 ##}} , realized by Fx ₄ ^{# #,} vehicle longitudinal direction force Fx ^{# #,} vehicle lateral force Fy ^{# #,} yaw The moment M ^## is obtained from the equations (20) to (22). Also, using the yaw rate γ determined in step S70 and the side slip angle β of the vehicle, a differential value β ′ ^## of the vehicle side slip angle realized by Fx _i ^## is determined by equation (23).

  However,

Fy ₁ ^## , Fy ₂ ^## , Fy ₃ ^## , Fy ₄ ^## are current vehicle conditions, and Fx ₁ ^## , Fx ₂ ^## , Fx ₃ ^## , Fx ₄ ^## are on each wheel. This is the tire lateral force that is generated when it is applied, and is set from a tire characteristic map that represents the relationship between the driving force and the tire lateral force based on the side slip angle β _i and the wheel load W _i of each wheel obtained in step S70. This tire characteristic map is common to each wheel, and is set as shown in FIG.

  The next step S90 is processing corresponding to the (D) block of FIG. 1, the (D) 'block of FIG. 2, and the (D) "block of FIG.

In step S90, the vehicle behavior target values Fx ^** , Fy ^** , M ^** , β ' ^** and Fx ^## , Fy ^## , M ^## , β'^## obtained in step S80. Differences ΔFx, ΔFy, ΔM (first correction amount), and Δβ ′ are obtained by Expressions (25) to (28).

In step S92, the differences Δγ and Δβ between the target values γ ^** and β ^{** of} the yaw rate and the vehicle side slip angle and γ and β obtained in step S70 are obtained by equations (29) and (30).

  The next step S94 is processing corresponding to the (F) block of FIG. 1 and the (F) "block of FIG.

In step S94, Δγ obtained in step S92 is reduced, and a yaw moment correction amount DM (second correction amount) for making the yaw rate asymptotic to the target value γ ^** is obtained by equation (31).

  However, Ts is a calculation cycle (unit: s) of the controller 8.

The equation (31) obtains a yaw moment correction amount DM that compensates Δγ by the next calculation cycle, and this may be a high gain control in the high frequency range by the controller 8. In such a case, the yaw moment correction amount DM may be obtained by the equation (32) including the proportional gain Pg (0 <P _g <1, unit: none).

  However, Δγ (k−1) is Δγ before one calculation cycle in the controller 8, and the initial value of Δγ (k−1) is 0.

In step S94, as a method other than the equations (31) and (32), a control system is designed so that the trade-off between the follow-up performance of the yaw rate to the target value γ ^** and the deviation can be considered, and the yaw moment More preferably, the correction amount DM is obtained.

  It is also known that the response of the yaw rate to the distribution of the driving force of each wheel and the steering angle of the front wheels changes depending on the vehicle speed V ("Automobile Movement and Control", Chapter 3, (Author) Masato Abe, (publishing) ) Sankaido). Therefore, in step S94, it is better to obtain the yaw moment correction amount DM by using a gain schedule control system or the like that can maintain the convergence of Δγ even if the vehicle speed V changes.

  The next step S96 is processing corresponding to the (F) 'block of FIG. 2 and the (F) "block of FIG.

In step S96, Δβ obtained in step S92 and Δβ ′ obtained in step S90 are reduced, and a vehicle lateral force correction amount DFy for making the vehicle side slip angle asymptotically approach the target value β ^** is obtained by equation (33).

  Here, ∂β ′ in Expression (33) is obtained from Expression (34).

  However, Δβ (k−1) is Δβ before one calculation cycle in the controller 8, and the initial value of Δβ (k−1) is 0.

In Equation (34), ∂β ′ is obtained so that Δβ is compensated by the next calculation cycle. However, in the same manner as in step S94, the control by the controller 8 may become high gain in the high frequency region. Therefore, ∂β ′ may be obtained as in Expression (35) including a proportional gain P _g ′ (0 <P _g ′ <1, unit: none).

In step S96, it is better to design a control system that can take into account the trade-off between the tracking performance of the vehicle side slip angle to the target value β ^** and the deviation, and to obtain the vehicle lateral force correction amount DFy.

  Further, as described in step S94, since the response of the vehicle side slip angle to the driving force distribution of each wheel and the front wheel rudder angle changes depending on the vehicle speed V or the like, the convergence of Δβ is not impaired even if the vehicle speed V or the like changes. It is better to obtain the vehicle lateral force correction amount DFy using a gain schedule control system or the like that can be used.

  The next steps S98 to S100 are processes corresponding to the (G) block of FIG. 1, the (G) 'block of FIG. 2, and the (G) "block of FIG.

  In step S98, ΔFx, ΔFy, and ΔM obtained in step S90 are reset. Since the resetting method differs depending on whether the first to third inventions are applied, the resetting method in each invention will be described.

  When using the first invention, ΔFx, ΔFy, and ΔM obtained in step S90 are reset as shown in equations (36) to (38).

  When the first invention is used, ΔFx, ΔFy, ΔM obtained in step S90 may be reset as shown in equations (39) to (41).

  Next, in the case of using the second invention, ΔFx, ΔFy, ΔM obtained in step S90 are reset as shown in equations (42) to (44).

  When the second invention is used, ΔFx, ΔFy, ΔM obtained in step S90 may be reset as in the equations (45) to (47).

  When using the third invention, ΔFx, ΔFy, ΔM obtained in step S90 are reset as shown in equations (48) to (50).

In step S100, ΔFx ₁ , ΔFx ₂ , ΔFx ₃ , and ΔFx ₄ for correcting ΔFx, ΔFy, and ΔM reset in step S98 are obtained. The correction amount DerutaFx _i is determined in accordance with the flowchart shown in FIG. 13. It will be described later how to obtain the DerutaFx _i according to the flowchart shown in FIG. 13.

In step S110, the sum of ΔFx _i and Fx _i ^## is set as a target value Fx _i ^** = Fx _i ^## + ΔFx _i for the driving force distribution of each wheel.

In step S120, control is performed so that the motors 11 to 14 of each wheel output a value obtained by dividing Fx _i ^** by the radius R of each wheel.

Next, in step S70 of the flowchart of FIG. 5, the yaw rate γ (unit: rad / s), the vehicle side slip angle β (unit: rad), the wheel load W _{i of} each wheel (unit: N), and the side slip angle of each wheel. The flowchart of FIG. 12 for calculating β _i (unit: rad) will be described.

First, in step S200, the vehicle longitudinal force Fx, the vehicle lateral force Fy, and the yaw moment M when the target value Fx _i ^{** for} driving force distribution is output are obtained by equations (51) to (53). .

  However,

Fy _i ^** is a tire lateral force generated when Fx _i ^** is applied to each wheel, and the driving force and tire are determined based on the side slip angle β _{i of} each wheel and the wheel load W _i obtained one calculation cycle before. It is set from a tire characteristic map that represents the relationship with the lateral force. The tire characteristic map is common to all the wheels, and the same one (FIG. 11) as used in step S80 in the flowchart of FIG.

In step S200, the vehicle longitudinal force Fx and the vehicle lateral force Fy are respectively divided by the vehicle mass, and the vehicle longitudinal acceleration α _x (unit: m / s ² ) and lateral acceleration α _y (unit: m / s ² ). At this time, it is more preferable to obtain α _x and α _y in consideration of air resistance and the like.

  In step S201, a value obtained by dividing the yaw moment M by the yaw inertia moment I of the vehicle is integrated to obtain the yaw rate γ. The initial value of the yaw rate γ is 0.

  In step S202, the time differential value β ′ of the vehicle slip angle is obtained by the equation (55), and the vehicle slip angle β is obtained by integrating β ′. The initial value of the side slip angle β of the vehicle is 0.

  However, β (k−1) is the side slip angle β of the vehicle one calculation cycle before.

In step S203, the wheel load W _i (unit: N) of each wheel is obtained by equations (56) to (59).

However, g is a gravitational acceleration (unit: m / s ² ) In step S204, the side slip angle β _i (unit: rad) of each wheel is obtained by Expressions (60) to (163).

Next, in step S100 of the flowchart of FIG. 5, the case of obtaining the feedback control amount DerutaFx _i of each wheel driving force distribution in accordance with the flowchart of FIG. 13.

According to this, first, in step S300, the sensitivity K _ix (unit: none), K _iy (unit: none), K _iM for the vehicle longitudinal force, vehicle lateral force, and yaw moment with respect to the driving force change of each wheel, respectively. (Unit: rad · m)) (for example, the sensitivity of the vehicle front-rear direction force to the driving force change of the left front wheel 1 is K _1x , and the sensitivity of the yaw moment to the driving force change of the right rear wheel 4 is K _4M ), Fx _i ^Obtained from ^## and β _i with reference to the vehicle behavior sensitivity map. For example, the vehicle behavior sensitivity map is set as shown in FIG. 14 (only the map of the left front wheel 1 is shown as an example in FIG. 14).

  This vehicle behavior sensitivity map extracts all combinations of the driving force and side slip angle that can be taken by the vehicle, and the vehicle when the driving force of any one wheel is changed by 1 [N] in each combination. The amount of change in the longitudinal force, vehicle lateral force, and yaw moment is obtained and mapped.

In step S301, three wheels whose [K _ix K _iy K _iM ] are linearly independent of each other, each of which represents the sensitivity of the vehicle longitudinal force, the vehicle lateral force, and the yaw moment with respect to the driving force change of each wheel as a vector. Choose a combination. How to choose is as follows.

First, the left front wheel 1 Consider the matrix K ₁ for arranging expression vectors of the remaining three wheels in the vertical (64) other than, the determinant det of the matrix K ₁ | K ₁ | if is not 0, the combination of the wheel The remaining three wheels other than the left front wheel 1 are set, and 1 is set in the flag flg.

If det | K ₁ | is 0, a matrix K _{2 in} which the vectors of the remaining 3 wheels other than the right front wheel 2 are vertically arranged is considered in the same manner as in equation (64), and the determinant det | K ₂ | If not, the combination of the wheels is the remaining three wheels other than the right front wheel 2, and 2 is set in the flag flg. If det | K ₂ | is also 0, this time, a matrix K _{3 in} which the vectors of the remaining three wheels other than the left rear wheel 3 are vertically arranged is considered in the same manner as in equation (64), and the determinant det | K ₃ | If it is not 0, the combination of the wheels is the remaining 3 wheels other than the left rear wheel 3, and 3 is set in the flag flg. If det | K ₃ | is also 0, this time, a matrix K _{4 in} which the vectors of the remaining three wheels other than the right rear wheel 3 are arranged vertically is considered in the same manner as in equation (64), and the determinant det | K ₄ | If it is not 0, the combination of the wheels is the remaining three wheels other than the left rear wheel 4, and 4 is set in the flag flg. If the determinant det | K ₄ | is also 0 and det | K _i | is all 0, the flag flg is set to 0 with no combination.

In step S302, if the flag flg is 0, the process proceeds to step S304, where Fx ₁ = Fx ₂ = Fx ₃ = Fx ₄ = 0. Otherwise, the process proceeds to step S303.

In step S303, obtains the Fx _i in operation method corresponding to the flag flg obtained in step S301, the flow is terminated. For example, when the flag flg is 1, Fx _i is obtained by Expression (65). That is, the driving force correction amount of the three wheels are selected [K _ix K _iy K _iM] is linearly independent from each other in step S301, determined by multiplying ΔFx, ΔFy, the inverse matrix K _i of the .DELTA.M, The driving force correction amount of the left front wheel 1 that has not been selected is set to zero. The same applies when the flag flg is 2-4.

Although the embodiment of the present invention has been described above, the present invention is not limited to the vehicle shown in FIG. 4, but a vehicle in which the rear wheels can be steered at an angle different from that of the front wheels and the rotation angle θ of the steering 5. The present invention is also applicable to a vehicle equipped with steer-by-wire, such as a vehicle that can control the steering angle δ _i of each wheel.

It is an example of the system configuration | structure of the driving force distribution control system by 1st invention. It is an example of the system configuration | structure of the driving force distribution control system by 2nd invention. It is an example of the system configuration | structure of the driving force distribution control system by 3rd invention. It is a figure which shows the structure of the electric vehicle provided with the motor which drives four wheels independently. It is a flowchart of torque distribution control in one embodiment. It is a map showing the static target value of the vehicle longitudinal force according to the depression amount of the accelerator pedal and the vehicle body speed. It is a map showing the static target value of the vehicle longitudinal force according to the depression amount of a brake pedal. It is a map showing the static target value of the vehicle lateral force according to the steering rotation angle, the vehicle speed, and the vehicle longitudinal force. It is a map showing the static target value of the yaw rate according to the steering rotation angle, the vehicle speed, and the vehicle longitudinal force. It is a map showing the static target value of the driving force distribution of each wheel. It is a map showing the static target value of the driving force distribution of each wheel. It is a figure showing the relationship between the driving force and tire lateral force which change according to a side slip angle and a wheel load. It is a flowchart which calculates the various state quantities of a vehicle. It is a figure which shows the flowchart which calculates | requires the feedback control amount of driving force distribution. It is a map of the sensitivity of the vehicle behavior with respect to the driving force change of each wheel. It is an example of the time transition of the yaw moment and yaw rate control by a prior art.

Explanation of symbols

1-4: Wheel 5: Steering 6: Accelerator pedal 7: Brake pedal 8: Controller 9: Battery 11-14: Motor 15: Steering gear 21-24: Wheel speed sensor 25: Steering angle sensor 26: Accelerator stroke sensor 27: Brake stroke sensors 31 to 34: inverters 41 to 44: rudder angle sensor 100: acceleration sensor 101: yaw rate sensor

Claims (3)

In the vehicle driving force distribution device that drives the four wheels independently,
Target vehicle behavior determining means for determining target values of the vehicle longitudinal force, yaw rate and yaw moment based on the driving state of the vehicle,
Driving force distribution basic value setting means for setting a basic value of driving force distribution of each wheel that substantially realizes the target values of the vehicle longitudinal force, yaw rate and yaw moment;
Vehicle behavior calculation means for calculating vehicle longitudinal force and yaw moment realized by the basic value of the driving force distribution;
The correction amount of the vehicle longitudinal force is calculated from the difference between the target value of the vehicle longitudinal force and the vehicle longitudinal force realized by the basic value of the driving force distribution, and the target value of the yaw moment and the driving force distribution are calculated. Vehicle behavior correction amount calculating means for calculating a first correction amount of the yaw moment from a difference from the yaw moment realized by the basic value of
A yaw rate calculating means for calculating a yaw rate realized by a target value of the driving force distribution of each wheel;
Yaw rate error calculation means for calculating an error between the target value of the yaw rate and the yaw rate calculated by the yaw rate calculation means;
A yaw moment correction amount calculating means for obtaining a second correction amount of the yaw moment in a direction to reduce the yaw rate error;
Driving that calculates a correction amount of the driving force distribution of each wheel that realizes the yaw moment correction amount calculated by the sum of the first correction amount and the second correction amount and the vehicle front-rear direction force correction amount. Force distribution correction amount calculation means;
Target driving force distribution determining means for setting the target value of the driving force distribution to the sum of the basic value of the driving force distribution and the correction amount of the driving force distribution;
Driving force control means for independently controlling the driving force of each wheel according to the target value of the driving force distribution;
A driving force distribution device comprising: In the vehicle driving force distribution device that drives the four wheels independently,
Target vehicle behavior determining means for determining a target value of time differentiation of vehicle longitudinal force, vehicle side slip angle, and vehicle side slip angle of the vehicle based on the driving state of the vehicle;
Driving force distribution basic value setting means for setting a basic value of the driving force distribution of each wheel that substantially realizes the target value of time differential of the vehicle longitudinal force, the vehicle body side slip angle, and the vehicle body side slip angle;
Vehicle behavior calculating means for calculating a differential value between the vehicle longitudinal force and the vehicle body side slip angle realized by the basic value of the driving force distribution;
A correction amount of the vehicle longitudinal force is calculated from a difference between the target value of the vehicle longitudinal force and the vehicle longitudinal force realized by the basic value of the driving force distribution, and the time differential target value of the vehicle body slip angle is calculated. Vehicle behavior correction amount calculating means for calculating a correction amount of the differential value of the vehicle body side slip angle from a difference from the differential value of the vehicle body side slip angle realized by the basic value of the driving force distribution;
A vehicle body side slip angle calculating means for calculating a vehicle body side slip angle realized by a target value of the driving force distribution of each wheel;
Vehicle body side slip angle error calculating means for calculating an error between the target value of the vehicle body side slip angle and the vehicle body side slip angle calculated by the vehicle body side slip angle calculating means;
Vehicle lateral force correction amount calculating means for obtaining a correction amount of the vehicle lateral force in a direction to reduce both the correction value of the differential value of the vehicle body side slip angle and the error of the vehicle body side slip angle;
Driving force distribution correction amount calculating means for calculating a correction amount of the driving force distribution of each wheel that realizes the correction amount of the vehicle lateral force and the correction amount of the vehicle longitudinal force;
Target driving force distribution determining means for setting the target value of the driving force distribution of each wheel to the sum of the basic value of the driving force distribution and the correction amount of the driving force distribution;
Driving force control means for independently controlling the driving force of each wheel according to the target value of the driving force distribution;
A driving force distribution device comprising: In the vehicle driving force distribution device that drives the four wheels independently,
Target vehicle behavior determining means for determining a target value of time differentiation of vehicle longitudinal force, yaw rate, yaw moment, vehicle body side slip angle and vehicle body side slip angle based on the driving state of the vehicle;
Driving force distribution basic value setting means for setting a basic value of driving force distribution of each wheel that substantially realizes a target value of time differentiation of the vehicle longitudinal force, yaw rate, yaw moment, vehicle body side slip angle and vehicle body side slip angle;
Vehicle behavior calculating means for calculating a differential value of the vehicle longitudinal force, yaw moment and vehicle side slip angle realized by the basic value of the driving force distribution;
The correction amount of the vehicle longitudinal force is calculated from the difference between the target value of the vehicle longitudinal force and the vehicle longitudinal force realized by the basic value of the driving force distribution, and the target value of the yaw moment and the driving force distribution are calculated. The first correction amount of the yaw moment is calculated from the difference from the yaw moment realized by the basic value of the vehicle, and the vehicle side skid angle realized by the target value of the differential value of the vehicle side slip angle and the basic value of the driving force distribution is calculated. Vehicle behavior correction amount calculation means for calculating the correction amount of the derivative value of the vehicle body side slip angle from the difference from the differential value of
A yaw rate calculating means for calculating a yaw rate realized by a target value of the driving force distribution of each wheel;
Yaw rate error calculation means for calculating an error between the target value of the yaw rate and the yaw rate calculated by the yaw rate calculation means;
A yaw moment correction amount calculating means for obtaining a second correction amount of the yaw moment in a direction to reduce the error of the yaw rate;
A vehicle body side slip angle calculating means for calculating a vehicle body side slip angle realized by a target value of the driving force distribution of each wheel;
Vehicle body side slip angle error calculating means for calculating an error between the target value of the vehicle body side slip angle and the vehicle body side slip angle calculated by the vehicle body side slip angle calculating means;
Vehicle lateral force correction amount calculation means for obtaining a correction amount of the vehicle body lateral force in a direction in which both the correction amount of the differential value of the vehicle body side slip angle and the error of the vehicle body side slip angle are reduced,
Driving force of each wheel that realizes the yaw moment correction amount calculated by the sum of the first correction amount and the second correction amount, the vehicle lateral force correction amount, and the vehicle longitudinal force correction amount. A driving force distribution correction amount calculating means for calculating a distribution correction amount;
Target driving force distribution determining means for setting the target value of the driving force distribution of each wheel to the sum of the basic value of the driving force distribution and the correction amount of the driving force distribution;
Driving force control means for independently controlling the driving force of each wheel according to the target value of the driving force distribution;
A driving force distribution device comprising: