JP4524597B2 - Driving force distribution device for four-wheel independent drive vehicle - Google Patents

Description

  The present invention relates to a driving force distribution device for a four-wheel independent drive vehicle including a drive motor corresponding to each drive wheel of the four-wheel drive vehicle.

  A driving force distribution device for a four-wheel independent drive vehicle that includes a drive motor corresponding to each drive wheel of the four-wheel drive vehicle is known (see Patent Document 1).

This means that when only one of the four drive wheels is slipping, it is allocated to the non-slip wheel on the same side as the slip wheel on the left and right sides, and to the slip wheel if no slip occurs. Distribute the output torque that should have been. Also, when there are two slip wheels, one on each of the left and right sides, the torque output that would have been distributed to that slip wheel if it did not slip is distributed to the non-slip wheels on the same side To do. Thus, before and after correcting the driving force, the change in the yaw moment around the center of gravity of the vehicle caused by the acceleration in the front-rear direction and the driving force of each wheel is suppressed.
Japanese Patent Laid-Open No. 10-295004

  However, in the above-described conventional example, the braking / driving force distributed to the front and rear wheels on each of the left and right sides of the vehicle is corrected so as not to change to suppress the change in the yaw moment around the center of gravity of the vehicle. It does not take into account changes in the lateral force generated between each wheel and the road surface. For this reason, the lateral force generated at the front wheel and the rear wheel may change greatly before and after the correction, and the lateral acceleration and the yaw moment around the center of gravity of the vehicle based on it may change. This is a change that is not intended by the driver and may impair driving performance.

  Therefore, the present invention has been made in view of the above problems, and when the braking / driving force of any one wheel is changed or arbitrarily changed, the wheel has a steering angle in addition to the left / right driving force difference. It is an object of the present invention to provide a driving force distribution device for a four-wheel independent drive vehicle capable of suppressing changes in acceleration in the front-rear and lateral directions and yaw moment around the center of gravity of the vehicle.

  The present invention relates to a driving force distribution device for a four-wheel independent drive vehicle that is capable of independently driving the four wheels and includes braking / driving force determining means for determining the braking / driving force of each of the four wheels based on a motion demand of the vehicle. , Tire lateral force sensitivity estimation means for estimating tire lateral force sensitivity k1, k2, k3, k4 with respect to changes in driving force of the left front wheel, right front wheel, left rear wheel, and right rear wheel, left front wheel, right front wheel, left Based on the steering angles δ1, δ2, δ3, δ4 of the rear wheel and the right rear wheel and the sensitivities k1, k2, k3, k4 estimated by the tire lateral force sensitivity estimation means, the left front wheel, the right front wheel, the left rear Means for correcting the driving force of each of the wheel and the right rear wheel, and when changing the braking / driving force determined by the braking / driving force determining means, the driving force correcting means includes the left front wheel and the right front wheel. , Steering angles δ1, δ2, δ3, δ4 of the left rear wheel and the right rear wheel, and sensitivities k1, k2 estimated by the tire lateral force sensitivity estimating means , K3, and k4, the driving force correction amounts ΔFx1, ΔFx2, ΔFx3, and ΔFx4 for the left front wheel, the right front wheel, the left rear wheel, and the right rear wheel are corrected so as to satisfy the motion requirement of the vehicle.

  Therefore, in the present invention, when changing the braking / driving force determined by the braking / driving force determining means for determining the braking / driving force of each of the four wheels based on the motion request of the vehicle, the driving force correcting means Based on the steering angles δ1, δ2, δ3, δ4 of the right front wheel, the left rear wheel, and the right rear wheel, and the sensitivities k1, k2, k3, k4 estimated by the tire lateral force sensitivity estimating means. The driving force correction amounts ΔFx1, ΔFx2, ΔFx3, and ΔFx4 for the left front wheel, the right front wheel, the left rear wheel, and the right rear wheel are corrected so as to satisfy the motion requirement. With such a configuration, even when the steering angle δi (i = 1 to 4) of each wheel is so large that it cannot be ignored, not only the longitudinal acceleration but also the lateral force change of the tire when the braking / driving force is corrected Therefore, it is possible to suppress changes in lateral acceleration and yaw moment around the center of gravity of the vehicle, which can prevent unintended disturbance of vehicle behavior and improve drivability.

  Hereinafter, a driving force distribution device for a four-wheel independent drive vehicle of the present invention will be described based on an embodiment. FIG. 1 is a system configuration diagram showing a first embodiment of a driving force distribution device for a four-wheel independent drive vehicle to which the present invention is applied.

  In FIG. 1, the driving force distribution device for a four-wheel independent drive vehicle has motors 11, 12, 13 and 14 connected to a left front wheel 1, a right front wheel 2, a left rear wheel 3 and a right rear wheel 4, respectively. The motors 11 to 14 are configured to be able to drive the wheels 1 to 4 independently. The rotation radii (R) of the wheels 1 to 4 are all equal, and the motors 11 to 14 and the wheels 1 to 4 rotate in a directly connected state with a reduction ratio of 1. Wheel speed sensors 21 to 24 are arranged on the respective drive shafts, and the detected rotational speed signal is output to the controller 8.

  The motors 11 to 14 are AC machines that can perform power running operation and regenerative operation such as a three-phase synchronous motor and a three-phase induction motor, and invert DC power from the battery 9 in accordance with commands from the controller 8, respectively. The wheels 1 to 4 can be driven by being independently powered by being converted into alternating current power via the wheel, and driven from the wheels 1 to 4 in response to a command from the controller 8. During regenerative operation, the AC regenerative power can be converted into DC power via inverters 31 to 34 to charge the battery 9. The battery 9 is preferably a nickel metal hydride battery or a lithium ion battery.

  The left and right front wheels 1 and 2 can be steered by steering the steering handle 5 via the steering gear 15, and the steering angle is mechanically adjusted by the steering of the steering handle 5 by the driver. The steering amount of the steering handle 5 is detected by a steering angle sensor 25 and output to the controller 8 as a steering angle signal. The gear ratio of the steering gear 15 is set so that the steering angle change amount of the left and right front wheels is 1/16 with respect to the steering angle change amount of the steering handle 5. The steering angles of the left and right rear wheels 3 and 4 are adjusted by the steering actuator 16 so as to follow the command value commanded from the controller 8. 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 controller 8 includes an accelerator stroke for detecting the steering angle signal of the steering angle sensor 25 for detecting the steering rotation angle of the steering handle 5 by the driver, the depression amount of the accelerator pedal 6 and the depression amount of the brake pedal 7 by the driver, respectively. Sensor 26 and brake stroke sensor 27 detection signals (depression amount), steering angle sensors 41 to 44 for detecting the steering angles of the wheels 1 to 4, detected steering angle signals, and the vehicle front-rear direction attached to the center of gravity of the vehicle And an acceleration signal from the acceleration sensor 100 that detects lateral acceleration, a yaw rate signal from the yaw rate sensor 101 that is attached to the center of gravity of the vehicle and detects the yaw rotation of the vehicle, and the wheel speed signal described above are input. The The controller 8 includes a CPU, a ROM, a RAM, an interface circuit, and the like, calculates torque distribution to the motors 11 to 14 based on the signals, and controls command values to the inverters 31 to 34.

  The flowchart of FIG. 2 shows a routine for calculating the torque distribution to each of the motors 11 to 14 and controlling the command value to each of the inverters 31 to 34, and is executed by the controller 8 at regular intervals. In this flowchart, steps S20 to S70 constitute braking / driving force determining means for determining the braking / driving force of each of the four wheels based on the vehicle motion request, and steps S80 to S90 and step S140 are the left front wheel 1 and the right front wheel 2. , Tire lateral force sensitivity estimation means for estimating the tire lateral force sensitivity k1, k2, k3, k4 with respect to the driving force changes of the left rear wheel 3 and the right rear wheel 4 is configured, and steps S100 to S130 determine the braking / driving force. A means for determining a necessary braking / driving force correction amount based on a factor for changing the braking / driving force determined by the means is configured, and steps S150 to S160 are used to steer the left front wheel, the right front wheel, the left rear wheel, and the right rear wheel. Based on the angles δ1, δ2, δ3, δ4 and the sensitivity k1, k2, k3, k4 estimated by the tire lateral force sensitivity estimation means, the left front wheel 1, the right front wheel 2, the left Rear wheel 3, right rear 4 each of the driving force ΔFx1, ΔFx2, ΔFx3, constitute a driving force correction means for correcting only DerutaFx4. This will be described below.

In step S10, the rotational speeds ω1, ω2, ω3, and ω4 [unit: rad / s] of the wheels 1 to 4 detected by the wheel speed sensors 21 to 24 are detected, respectively, and multiplied by the radius R of the wheels 1 to 4. The wheel speeds V1, V2, V3, V4 [unit: m / s] are calculated. Further, the steering angle sensors 41 to 44 detect the steering angles δ1, δ2, δ3, and δ4 [unit: rad] of the wheels 1 to 4, respectively. Further, the depression amounts AP [unit:%] and BP [unit:%] of the accelerator pedal 6 and the brake pedal 7 detected by the accelerator stroke sensor 26 and the brake stroke sensor 27, and the rotation of the steering handle 5 detected by the steering angle sensor 25. Angle θ [unit: rad], vehicle longitudinal acceleration Xg [unit: m / s ² ] and lateral acceleration Yg [unit: m / s ² ] detected by acceleration sensor 100, yaw rate γ detected by yaw rate sensor 101 Read [Unit: rad / s] respectively.

  The wheel speeds V1 to V4 are positive in the forward direction of the vehicle, the rotation angle θ of the steering handle 5 is positive in the counterclockwise direction, the longitudinal acceleration Xg is positive in the direction in which the vehicle accelerates forward, and the lateral acceleration Yg. Is positive in the direction from the center of gravity of the vehicle toward the turning center when the vehicle is turning left, and the yaw rate γ is positive in the counterclockwise direction when the vehicle is viewed from vertically above. As shown in FIG. 3, the steering angles δ1 to δ4 are set to 0 when the directions of the wheels 1 to 4 coincide with the longitudinal direction of the vehicle body, and the counterclockwise direction is positive when the vehicle is viewed from vertically above. To do. The distance from the vehicle center of gravity position in the yaw rotation direction of the vehicle to the front wheel axle is Lf [unit: m], the distance from the vehicle gravity center position in the yaw rotation direction to the rear wheel axle is Lr [unit: m], Both tread lengths are vehicles of Lt [unit: m]. In the following description, the wheel base length of the vehicle is L (= Lf + Lr).

In step S20, the vehicle speed V [unit: m / s] is expressed by the following equation (1).
V = (V1 + V2 + V3 + V4) ÷ 4 (1)
Ask as follows. The vehicle speed V is positive in the vehicle forward direction.

In step S30, the wheel loads W1, W2, W3, and W4 [unit: N] of each of the wheels 1 to 4 are expressed by the following equations (2) to (5).
W1 = (mLrg / 2L)-(mhXg / 2L)-(mhYg / 2Lt) (2)
W2 = (mLrg / 2L)-(mhXg / 2L)-(mhYg / 2Lt) (3)
W3 = (mLfg / 2L)-(mhXg / 2L)-(mhYg / 2Lt) (4)
W4 = (mLfg / 2L)-(mhXg / 2L)-(mhYg / 2Lt) (5)
Ask as follows.

In step S40, the steering angles δ3 and δ4 of the rear wheels 3 and 4 with respect to the rotation angle θ of the steering handle 5 are expressed by the following equation (6).
δ3 = δ4 = (1/16) [k0 / (1 + TeS) − (Kf / Kr) (TeS / (1 + TeS))] × θ (6)
The steering actuator 16 is controlled so that However, Te = IV / (2LLfKf + mLrV 2), K0 = - a [Lr + (mLf / 2LKr) KfV 2] / [Lf + (mLr / 2LKf) KrV 2]. In the equation (6), m [unit: kg] and I [unit: kgm 2] are the mass of the vehicle to be controlled and the yaw moment of inertia around the center of gravity of the vehicle shown in FIG. 3, and Kf, Kr [unit: N / rad] is a cornering force per unit side slip angle when the side slip angles of the front wheels 1 and 2 and the rear wheels 3 and 4 are sufficiently small. Further, as described above, “1/16” at the left end of the right side of the equation (6) is the sensitivity of the front wheel steering angles δ 1 and δ 2 with respect to the change in the rotation angle θ of the steering handle 5.

  Thus, by determining the target responses of the steering angles δ3 and δ4 of the left and right rear wheels 3 and 4 with respect to the rotation angle θ of the steering handle 5, when the difference in driving force between the left and right wheels is zero, the side slip angle of the vehicle body It is known that β can be nullified ("Motor Movement and Control", Chapter 8, Section 8.3.1, (Author) Masato Abe, (Publishing) Sankai-do).

In step S50, the driver's required braking / driving force tF for the electric vehicle is expressed by the following equation (7).
tF = tFa + tFb (7)
Ask as follows. As shown in FIG. 4, the required driving force tFa in the equation (7) is a required driving torque map in which the required driving force corresponding to the depression amount AP of the accelerator pedal 6 and the vehicle speed V is recorded in the ROM of the controller 8 in advance. It is set based on. Further, as shown in FIG. 5, the required braking force tFb is obtained by setting a required braking force corresponding to the depression amount BP of the brake pedal 7 based on a required braking force map previously recorded in the ROM of the controller 8. . Further, the required driving forces tF and tFa and the required braking force tFb are positive in the direction in which the vehicle is accelerated forward.

  In step S60, the left / right wheel driving force difference ΔF [unit: N] of the vehicle is calculated from the rotation angle θ of the steering handle 5 and the vehicle speed V in a target left / right driving force difference map stored in the ROM of the controller 8 in advance. Set based on. This target left / right driving force difference map is obtained by setting a left / right wheel driving force difference ΔF corresponding to the steering angle θ and the vehicle speed V, for example, as shown in FIG.

  The difference between the required driving force in step S50 and the left and right wheel driving force in step S60 is a request corresponding to the required driving force corresponding to the depression amount AP of the accelerator pedal 6 and the vehicle speed V by the driver and the depression amount BP of the brake pedal 7. It is set based on the motion demand in the acceleration / deceleration direction based on the sum of the braking force and the motion demand in the vehicle turning direction due to the steering of the steering handle 5. , 7 and the operation of the steering wheel 5, for example, according to a signal from an automatic control device such as an emergency avoidance device, an automatic tracking device that keeps the distance between the vehicles constant, or a lane keeping device that automatically maintains the traveling lane You may set based on the motion request | requirement of the vehicle which considered the longitudinal acceleration, the lateral acceleration, and the yaw rate.

In step S70, the braking / driving forces Fx1, Fx2, Fx3, and Fx4 of the wheels 1 to 4 are expressed by the following equations (8) and (9).
Fx1 = Fx2 = (tF / 4) − (ΔF / 4) (8)
Fx3 = Fx4 = (tF / 4) + (ΔF / 4) (9)
Ask for. The braking / driving forces Fx1, Fx2, Fx3, and Fx4 are positive forces acting in the direction of moving the vehicle forward.

  In step S80, the sideslip angles β1, β2, β3, β4 [unit: rad] of the wheels 1 to 4 are estimated. The side slip angle (also referred to as slip angle) is the current slip angle (current slip angle) formed by the traveling direction of the vehicle and the front-rear direction of the tire. Although there are various estimation methods, the following method is used here as an example. The vehicle body side slip angle β is estimated from the lateral acceleration Yg, yaw rate γ, vehicle speed V, and wheel steering angles δ1, δ2, δ3, and δ4 read in step S10. Then, the sideslip angles β1, β2, β3, β4 are estimated from the sideslip angle β, the yaw rate γ, the vehicle speed V, and the steering angle θ as follows.

First, the vehicle body side slip angle β is expressed by the following equation (10).
β = ∫ (Yg / V−γ) dt (10)
Estimated by

Next, the sideslip angles β1, β2, β3, and β4 of the wheels 1 to 4 are expressed by the following equations (11) and (12).
β1 = β2 = β + (θ / Gs) − (γ × Lf / V) (11)
β3 = β4 = β + (γ × Lr / V) (12)
Estimated by Here, β1, β2 are front wheel slip angles, β3, β4 are rear wheel slip angles, and Gs is a gear ratio of the steering gear 15. The signs of β1, β2, β3, and β4 are positive when the angle from the front-rear direction of the wheel to the direction of the wheel speed is counterclockwise when viewed from vertically above.

  In step S90, the road surface friction coefficients μ1, μ2, μ3, and μ4 of the wheels 1 to 4 are estimated. Although there are various estimation methods, the following method is used here as an example. First, the road surface reaction forces F′1 to F′4 that the wheels 1 to 4 receive from the road surface are estimated, and each wheel is determined from the road surface reaction forces F′1 to F′4 and the wheel loads W1 to W4 obtained in step S60. Estimate 1 to 4 road surface friction coefficients μ1, μ2, μ3, and μ4. That is, the electromagnetic torque Tm is applied to the motors 11 to 14, and the road surface reaction force torque obtained by multiplying the wheel surface reaction force F ′ by the wheel radius R is applied to the wheels 1 to 4 in the direction opposite to the torque by the motors 11 to 14. It has been added.

The motors 11 to 14 and the wheels 1 to 4 are in a directly connected state, and it can be assumed that the torsional rigidity κ of the axle is sufficiently large, and the rotational speeds and wheels of the motors 11 to 14 are ignored ignoring the torsional deformation of the axle. Assuming that the same speed ω holds with the rotational speeds 1 to 4, the equation of motion of the rotational system of the motors 11 to 14 and the wheels 1 to 4 is expressed by the following formula (13):
(Jm + Jw) ω ′ = Tm−Cmw · ω−Rmw−F · R (13)
Are summarized in Jm and Jw are moments of inertia of the motors 11 to 14 and wheels 1 to 4, Cm and Cw are viscous damping constants of the rotation systems of the motors 11 to 14 and wheels 1 to 4, and Rm and Rw are motors 11 to 14 and wheels. It is the solid friction of 1-4 rotating systems.

As a result, the road surface reaction force F ′ is expressed by the following equation (14) using the above equation (13).
F ′ = {Tm− (Jm + Jw) ω′−Cmw · ω−Rmw} / R (14)
Can be estimated. Therefore, the road surface reaction forces F′1 to F′4 are estimated and obtained for the wheels 1 to 4, respectively.

Similarly, the following formulas (15) to (18) are calculated based on the road surface reaction forces F′1 to F′4 and the tire loads W1 to W4 estimated in the same manner.
μ1 = F'1 / W1 (15)
μ2 = F'2 / W2 (16)
μ3 = F'3 / W3 (17)
μ4 = F'4 / W4 (18)
Can be used to estimate road surface friction coefficients μ1, μ2, μ3, and μ4. The estimation calculation of the road surface reaction force and the road surface friction coefficient as shown in the above formulas (14) and (15) to (18) can be realized by microcomputer software stored in the controller 8.

  In step S100, when any one of the wheels 1 to 4 slips or locks the wheel or the tendency is generated, the braking / driving necessary for preventing the slip or wheel lock of the wheel 1 to 4 is required. The force correction amount ΔFsi (i = 1 to 4) is obtained. The braking / driving force correction amount ΔFsi is obtained by the reaction force F′i (i = 1 to 4) received by each wheel 1 to 4 from the road surface and the torque of the motors 11 to 14 obtained in step S90. A difference from the braking / driving force Fx1 is defined as a braking / driving force correction amount ΔFsi (ΔFsi = F′i−Fxi).

  In step S100, the braking force correction amount ΔFsi necessary to prevent this is determined based on whether any of the wheels 1 to 4 slips or locks or whether such a tendency occurs. However, as a factor for changing the braking / driving force determined by the braking / driving force determining means in step S100, for example, performance degradation due to a failure of the motors 11 to 14 of any of the wheels 1 to 4 or the motor drive system Alternatively, a passive or active correction amount ΔFsi for a disturbance factor such as a braking / driving force command exceeding a driving force capability limit or an internal situation may be set.

  In step S110, if there is one or more wheels 1-4 where the absolute value | ΔFsi | of the braking / driving force correction amount ΔFsi is greater than a preset threshold value Fth, the process proceeds to step S120, and otherwise, the process proceeds to step S190. move on. The threshold value Fth is a threshold value for determining that the difference between the reaction force F′i received from the road surface and the braking / driving force Fxi is large, that is, the tendency of slip or wheel lock is strong. It is desirable that the vehicle weight W (unit: N) is 1%, that is, about 0.01 W. Note that the threshold value Fth is changed to a desired value according to the factor of change of the braking / driving force in step S100.

  In step S120, the braking / driving of the wheel having the largest absolute value | ΔFsi | of the braking / driving force correction value ΔFsi is considered in consideration of the case where a plurality of wheels 1 to 4 require the braking / driving force correction. The force correction value ΔFsi is set to ΔFk.

  Between step S120 and step S170 described later, one of the wheels 1 to 4 having the largest absolute value | ΔFsi | is recovered from the slip or wheel lock state, and the vehicle behavior (the longitudinal acceleration Xg , Lateral acceleration Yg, braking / driving force correction amount ΔFxi (i = 1 to 4) of each of the wheels 1 to 4 that does not disturb the yaw moment M around the center of gravity of the vehicle.

  In step S130, when | ΔFk | is equal to or smaller than the threshold value Fthb, “1” is set to the flag flg, and ΔFk is set to ΔFkr. If | ΔFk | is larger than the threshold value Fthb, “0” is set to the flag flg, ΔFkr = Fthb when ΔFk> = 0, and ΔFkr = −Fthb when ΔFk <0.

  The flag flg and the threshold value Fthb will be described below. When the driving force of any one of the wheels changes or is arbitrarily changed, the following equation (20) for determining the braking / driving force correction amount ΔFxi of the remaining three wheels that does not disturb the vehicle behavior, It is a precondition that the amount of change in driving force is minute. Therefore, when ΔFk is too large to be sufficiently small, it is difficult to accurately obtain the driving force correction amount ΔFxi for the remaining three wheels using Expression (20). The flag for determining this is flg, and “0” is set when the change is so large that it cannot be assumed to be small, and “1” is set otherwise.

  Further, when the absolute value of the maximum value of the braking / driving force variation that can be assumed to be minute is the threshold value Fthb, and when ΔFk is equal to or larger than the threshold value Fthb, the absolute value | ΔFsi | of the driving force correction value becomes the largest. Assuming that the braking / driving force of the wheel is changed by the threshold value Fthb, the braking / driving force Fxi of each wheel is corrected in steps S150 and S160 described later, and if ΔFk ← ΔFk−Fthb (ΔFk> = 0, step S190).

  By repeating this process until ΔFk becomes sufficiently small, that is, | ΔFk | <Fthb, the braking / driving force correction amount ΔFxi for the remaining three wheels can be obtained even when ΔFk is too small. In this embodiment, the threshold value Fthb is 4% of the vehicle weight W [unit: N], that is, 0.04 W.

  In step S140, the tire lateral force sensitivity ki (i (i) to the driving force change of each wheel 1 to 4 is calculated from the wheel load Wi, the side slip angle βi, and the road surface friction coefficient μi (i = 1 to 4) estimated in steps S30 to S90. = 1 to 4). The method for obtaining the sensitivity ki will be described by taking the case of the left front wheel 1 as an example.

  In the ROM of the controller 8, the relationship between the braking / driving force Fx1 and the tire lateral force Fy1 is obtained in advance for each wheel load W1, side slip angle β1, and road surface friction coefficient μ1 by experiment or simulation, as shown in FIG. A braking / driving force-tire lateral force map of the wheels 1 to 4 is stored for each wheel load W1, side slip angle β1, and road surface friction coefficient μ1 of each wheel 1 to 4.

The tire lateral force Fy1 corresponding to the current braking / driving force Fx1 and the tire lateral force (Fy1 + dFy1) at the next time corresponding to the braking / driving force at the next time (Fx1 + dFx1) are obtained with reference to this map. , Sensitivity ki, the following equation (19)
ki = dFy1 / dFx1 (19)
Ask according to. Here, the braking / driving force change dFx1 (unit: N, dFx1> 0) is a sufficiently small braking / driving force as compared with the wheel load W1. That is, the sensitivity k i of the tire lateral force Fy1 to the change in the braking / driving force Fx1 is obtained by obtaining the change amount dFy1 of the tire lateral force Fy1 when the braking / driving force Fx1 changes by a minute “dFx1”.

  Similarly, for the wheels 2 to 4, a braking / driving force-tire lateral force map is prepared, and the tire lateral force is defined by defining sufficiently small braking / driving force changes dFx2, dFx3, dFx4 as compared with the wheel loads W2 to W4. The sensitivities k2 to k4 are obtained.

In step S150, the braking / driving force correction amount ΔFxi (i = 1 to 4) of each wheel is obtained. Specifically, the wheels 1 to 4 having the largest absolute value | ΔFsi | of the braking / driving force correction amount ΔFsi are recovered from the slip or wheel lock state, and the vehicle behavior (the longitudinal acceleration Xg, the lateral direction) is restored. The acceleration / deceleration Yg and the braking / driving force correction amount ΔFxi (i = 1 to 4) of the wheels 1 to 4 that do not disturb the yaw moment M around the center of gravity of the vehicle are expressed by the following equation (20):
ΔFx1: ΔFx2: ΔFx3: ΔFx4
= [(Lt / L) (h4−h2) + h2 (h4−h3)] / (cosδ1−k1sinδ1): [(−Lt / L) (h3−h1) −h1 (h4−h3)] / (cosδ2− k2sinδ2): [(−Lt / L) (h4−h2) + h4 (h2−h1)] / (cosδ3−k3sinδ3): [(Lt / L) (h3−h1) + h3 (h2−h1)] / (cosδ4 -K4sinδ4) (20)
However, hi = (sinδi + kicosδi) / (cosδi−kisinδi)
Ask for. If the ratio of the braking / driving force correction amount ΔFxi of each of the wheels 1 to 4 is as shown in the above equation (20), the change in the longitudinal acceleration Xg, the lateral acceleration Yg, and the yaw moment M around the vehicle center of gravity is suppressed. Can do.

Therefore, for example, when the absolute value | ΔFs1 | of the driving force correction amount for the left front wheel 1 is the largest among the absolute values | ΔFs1 | to | ΔFs4 | 4 driving force correction amounts ΔFx1, ΔFx2, ΔFx3, and ΔFx4 are expressed by the following equations (21) to (24).
ΔFx1 = ΔFkr (21)
ΔFx2 = {[(− Lt / L) (h3−h1) −h1 (h4−h3)] / [(Lt / L) (h4−h2) + h2 (h4−h3)]} × [(cosδ1−k1sinδ1) / (Cosδ2-k2sinδ2)] × ΔFkr (22)
ΔFx3 = {[(− Lt / L) (h4−h2) + h4 (h2−h1)] / [(Lt / L) (h4−h2) + h2 (h4−h3)]} × [(cosδ1−k1sinδ1) / (cosδ3−k3sinδ3)] × ΔFkr (23)
ΔFx4 = {[(Lt / L) (h3−h1) + h3 (h2−h1)] / [(Lt / L) (h4−h2) + h2 (h4−h3)]} × [(cosδ1−k1sinδ1) / ( cosδ4−k4sinδ4)] × ΔFkr (24)
Ask as follows. Similarly, when the absolute value | ΔFsi | of the driving force correction values of the other wheels is the largest among the absolute values | ΔFs1 | to | ΔFs4 | of the driving force correction values, the driving force corrections of the wheels 1 to 4 are performed in the same manner. The quantity ΔFxi is determined.

  In this embodiment, the steering angles δ1, δ2, δ3, and δ4 of the wheels 1 to 4 are directly measured in step S10, and the driving force correction amount ΔFxi of each of the wheels 1 to 4 is obtained based on the equation (20). Yes. That is, the driving force correction amount ΔFxi is obtained in consideration of the steering angle change (compliance steer, roll steer, etc.) generated by the driving force of each wheel 1 to 4 and the tire lateral force applied to the suspension. It is none other than. Therefore, in a vehicle that does not have a means for directly detecting the steering angle δi of each of the wheels 1 to 4 and is estimated from the rotation angle θ of the steering handle 5 and the steering gear ratio, the steering angle change amount is determined from this suspension characteristic. By estimating and correcting the estimated value of the steering angle δi of each of the wheels 1 to 4, the driving force correction amount ΔFxi can be obtained with higher accuracy.

In step S160, the braking / driving force Fxi of each of the wheels 1 to 4 is expressed by the following equations (25) to (28).
Fx1 ← Fx1 + ΔFx1 (25)
Fx2 ← Fx2 + ΔFx2 (26)
Fx3 ← Fx3 + ΔFx3 (27)
Fx4 ← Fx4 + ΔFx4 (28)
Correct as follows.

  In step S170, if the flag flg is “1”, the process proceeds to step S190. Otherwise, in step S180, if ΔFk> 0, ΔFk ← ΔFk−Frhb, and if ΔFk <0, set ΔFk ← ΔFk + Fthb and proceed to step S130.

  In step S190, current command value control to the inverters 31 to 34 is performed so that the motors 11 to 14 output a value obtained by dividing the braking / driving force Fxi of each of the new wheels 1 to 4 by the tire radius R, that is, a torque command value. I do.

  By the way, in the prior application (Japanese Patent Application No. 2004-205789, filed on July 13, 2004), the present applicant has determined that the steering angle δi (i = 1 to 4) of each wheel in a vehicle that independently drives four wheels. Assuming that the driving force of any one wheel changes or the driving force of any one wheel is changed arbitrarily, the vehicle longitudinal and lateral accelerations and the yaw moment around the vehicle center of gravity are A driving force distribution device for a four-wheel independent driving vehicle that determines the driving force correction amount for the remaining three wheels so as not to change is proposed.

A method for obtaining the driving force correction amount for each wheel in which the acceleration in the vehicle longitudinal direction and the lateral direction and the yaw moment around the vehicle center of gravity according to this prior application will not change will be described below. FIG. 13 is a diagram showing the driving force and lateral force applied to the four-wheel independent driving vehicle and the yaw moment around the vehicle center of gravity on the assumption that the steering angle δi (i = 1 to 4) of each wheel is sufficiently small. is there. The sum Fx of the driving force of each wheel, the sum Fy of the tire lateral force of each wheel, and the sum M of the yaw moment around the vehicle center of gravity generated by the sum of the driving force and tire lateral force of each wheel are expressed by the following formula ( 29) to (31)
Fx = Fx1 + Fx2 + Fx3 + Fx4 (29)
Fy = Fy1 + Fy2 + Fy3 + Fy4 (30)
M = [(Fx2 + Fx4) − (Fx1 + Fx3)] × Lt / 2 + [(Fy1 + Fy2) × Lf− (Fy3 + Fy4) × Lr] (31)
Can be expressed as:

Therefore, when the driving force Fxi (i = 1 to 4) changes by the change amounts ΔFx1, ΔFx2, ΔFx3, and ΔFx4, the tire when the braking / driving force Fxi changes by this change amount ΔFxi (i = 1 to 4). When the lateral force change amount is ΔFyi (i = 1 to 4), the change amounts ΔFx, ΔFy, ΔM of the braking / driving force Fx, the tire lateral force Fy, and the yaw moment M are expressed by the following equations (32) to (34).
ΔFx = ΔFx1 + ΔFx2 + ΔFx3 + ΔFx4 (32)
ΔFy = ΔFy1 + ΔFy2 + ΔFy3 + ΔFy4 (33)
ΔM = [(ΔFx2 + ΔFx4) − (ΔFx1 + ΔFx3)] × Lt / 2 + [(ΔFy1 + ΔFy2) × Lf− (ΔFy3 + ΔFy4) × Lr] (34)
It becomes as follows.

Here, the relationship between the driving force and the tire lateral force is as shown in FIG. 7 and FIG. 9 in detail. Therefore, the sensitivity of the tire lateral force with respect to the driving force change amount ΔFxi at the current driving force Fxi and tire lateral force Fyi of each wheel is set to ki (i = 1 to 4). That is, as shown in FIG. 9, the lateral force sensitivity ki is an expression (35) when the braking / driving force variation ΔFxi and the tire lateral force variation ΔFyi are very small.
ki = ΔFyi / ΔFxi (35)
Is the value of

Then, if the braking / driving force change amount ΔFxi and the tire lateral force change amount ΔFyi are very small and the approximation of the equation (35) is sufficiently established, the tire lateral force change amount can be expressed as ΔFyi = kiΔFxi. ) To (34) of the tire lateral force total ΔFy and yaw moment total ΔM are expressed by the following equations (36) to (37).
ΔFy = k1ΔFx1 + k2ΔFx2 + k3ΔFx3 + k4ΔFx4 (36)
ΔM = [(ΔFx2 + ΔFx4) − (ΔFx1 + ΔFx3)] × Lt / 2 + [(k1ΔFx1 + k2ΔFx2) × Lf− (k3ΔFx3 + k4ΔFx4) × Lr]
= (K1Lf−Lt / 2) ΔFx1 + (k2Lf + Lt / 2) ΔFx2 + (− k3Lr−Lt / 2) ΔFx3 + (k4Lr−Lt / 2) ΔFx4 (37)
Is replaced as follows. Therefore, when the formula (32), the formula (36), and the formula (37) are put together, they are expressed as the following formula (38).

上記式（３８）の左辺、即ち、制駆動力変化量，タイヤ横力変化量，ヨーモーメント変化量の各総和ΔＦx,ΔＦy,ΔＭを０とした下記の式（３９）を満たす制駆動力補正量ΔＦx2,ΔＦx3,ΔＦx4は、式（３９）を制駆動力補正量ΔＦx2,ΔＦx3,ΔＦx4に関する連立方程式と見立てて解くと、制駆動力補正量ΔＦx1を用いて、下記の式（４０）〜式（４２）の通り表される。

The braking / driving force correction satisfying the following equation (39) where the left side of the above equation (38), that is, the sum ΔFx, ΔFy, ΔM of the braking / driving force variation, tire lateral force variation, and yaw moment variation is 0. The quantities ΔFx2, ΔFx3, and ΔFx4 are obtained by solving the equation (39) as simultaneous equations regarding the braking / driving force correction amounts ΔFx2, ΔFx3, ΔFx4, and using the braking / driving force correction amount ΔFx1, (42)

ΔＦx2＝〔[(−Ｌt/Ｌ)(ｋ3−ｋ1)−ｋ1(ｋ4−ｋ3)]／[(Ｌt/Ｌ)(ｋ4−ｋ2)−ｋ2(ｋ4−ｋ3)]〕×ΔＦx1 ・・・（４０）
ΔＦx3＝〔[(−Ｌt/Ｌ)(ｋ4−ｋ2)−ｋ4(ｋ2−ｋ1)]／[(Ｌt/Ｌ)(ｋ4−ｋ2)−ｋ2(ｋ4−ｋ3)]〕×ΔＦx1 ・・・（４１）
ΔＦx4＝〔[(Ｌt/Ｌ)(ｋ3−ｋ1)−ｋ3(ｋ2−ｋ1)]／[(Ｌt/Ｌ)(ｋ4−ｋ2)−ｋ2(ｋ4−ｋ3)]〕×ΔＦx1 ・・・（４２）
ただし、Ｌはホイールベース長さで、Ｌ＝Ｌf＋Ｌrである。

ΔFx2 = [[(− Lt / L) (k3−k1) −k1 (k4−k3)] / [(Lt / L) (k4−k2) −k2 (k4−k3)]] × ΔFx1. 40)
ΔFx3 = [[(− Lt / L) (k4−k2) −k4 (k2−k1)] / [(Lt / L) (k4−k2) −k2 (k4−k3)]] × ΔFx1. 41)
ΔFx4 = [[(Lt / L) (k3−k1) −k3 (k2−k1)] / [(Lt / L) (k4−k2) −k2 (k4−k3)]] × ΔFx1 (42 )
Here, L is the wheelbase length, and L = Lf + Lr.

As is apparent from the equations (40) to (42), the braking / driving force correction amounts ΔFx1, ΔFx2, ΔFx3, ΔFx4 are expressed by the following equation (43).
ΔFx1: ΔFx2: ΔFx3: ΔFx4
= (Lt / L) (k4-k2) -k2 (k4-k3): (-Lt / L) (k3-k1) -k1 (k4-k3): (-Lt / L) (k4-k2)- k4 (k2-k1) :( Lt / L) (k3-k1) -k3 (k2-k1) (43)
The ratio of the braking / driving force variation, the tire lateral force variation, and the yaw moment variation is ΔFx = ΔFy = ΔM = 0, and the braking / driving force Fx, tire lateral force Fy, and yaw moment M are The change can be made zero.

  From the above, when the sensitivity k i of the tire lateral force to the driving force change in each wheel 1 to 4 is defined, by changing the driving force of each wheel 1 to 4 at the ratio of the equation (43) based on this sensitivity ki, Not only braking / driving force Fx but also changes in tire lateral force Fy and yaw moment M can be made zero.

  That is, when the steering angle δ of each of the wheels 1 to 4 is sufficiently small, even if the driving force of any one wheel changes due to a failure, slip, etc., or the driving force changes arbitrarily, this one wheel If the driving force of the remaining three wheels is changed at a ratio of the expression (43) with respect to the braking / driving force change of the vehicle, it prevents the driver's unintended longitudinal and lateral acceleration and yaw moment around the vehicle's center of gravity. Can do.

  However, in the above-mentioned prior application, when it is assumed that the steering angle δ of each of the wheels 1 to 4 is sufficiently small, the acceleration in the front-rear direction and the lateral direction and the vehicle center of gravity around the center of gravity of the vehicle with respect to the driving force change of any one wheel A technique for determining the driving force correction amount for the remaining three wheels with zero change in yaw moment is proposed. When the front wheel steering angles δ1 and δ2 are increased during turning, the steering angles δi of the wheels 1 to 4 are Since the precondition is no longer satisfied when the value is increased, the driving force correction of the remaining three wheels that can prevent the change in the acceleration in the front and rear direction and the lateral direction and the yaw moment around the vehicle center of gravity with respect to the driving force change of any one wheel. You may not be able to ask for the amount.

  On the other hand, in the present embodiment, by calculating the braking / driving force correction amount ΔFxi (i = 1 to 4) of each wheel 1 to 4 based on the formula (20) proposed in step S150, each wheel 1 to 1 is obtained. 4 does not disturb the vehicle behavior (front-rear acceleration Xg, lateral acceleration Yg, yaw moment M around the vehicle center of gravity), that is, the longitudinal and lateral accelerations and the vehicle center of gravity. The driving force correction amount of each of the wheels 1 to 4 where the surrounding yaw moment does not change can be obtained.

  In the following, the braking / driving force correction amount ΔFxi (i = 1 to 4) of each wheel 1 to 4 is obtained based on the formula (20) proposed in step S150, thereby the steering angle δi of each wheel 1 to 4. Even if the vehicle behavior (the longitudinal acceleration Xg, the lateral acceleration Yg, the yaw moment M around the center of gravity of the vehicle) is not disturbed, that is, even if the steering angle δi of each wheel 1 to 4 is increased. A method for obtaining the driving force correction amount of each wheel 1 to 4 in which the acceleration in the front and rear direction and the lateral direction and the yaw moment around the center of gravity of the vehicle do not change will be described below.

  First, a method of obtaining the driving force correction amount ΔFxi of each wheel in which the longitudinal and lateral accelerations Xg, Yg and the yaw moment M around the center of gravity of the vehicle do not change in consideration of the steering angle δi of each wheel 1-4. Will be described with reference to FIG. FIG. 3 is a diagram showing the driving force, the tire lateral force, and the yaw moment around the center of gravity of the vehicle that are applied to the four-wheel independent driving vehicle. In the vehicle of FIG. 3, it is assumed that the wheel alignment change, the steering angle change, and the like generated by the force applied to the suspension are sufficiently small, and these suspension characteristics are ignored.

Here, when the steering angle of each wheel is cut by δi (i = 1 to 4) as shown in FIG. 8, the vehicle body longitudinal component Fx′i and the vehicle lateral component Fy′i of the tire force are as follows: Formula (44) and Formula (45)
Fx'i = Fxicosδi−Fyisinδi (44)
Fy'i = Fxisinδi + Fyicosδi (45)
It is expressed as follows. However, the vehicle body longitudinal component Fx′i is positive in the direction of accelerating the vehicle forward, and the vehicle body lateral component Fy′i is positive in the direction from the vehicle center of gravity to the turning center when the vehicle is turning left.

Accordingly, if the tire lateral force change amount when the braking / driving force changes by ΔFxi is ΔFyi, the vehicle longitudinal component and the vehicle lateral component components Fx′i and Fy′i change amounts ΔFx′i and ΔFy′i are: The following formula (46) and formula (47)
ΔFx′i = ΔFxicosδi−ΔFyisinδi (46)
ΔFy′i = ΔFxisinδi−ΔFyicosδi (47)
It is expressed as follows.

Furthermore, when the tire lateral force sensitivity ki for the minute braking / driving force change ΔFxi in the current braking / driving force Fxi and the tire lateral force Fyi of each of the wheels 1 to 4 defined by FIG. 9 and Expression (35) is used. Since the tire lateral force change amount ΔFyi≈kiΔFxi can be approximated, the vehicle longitudinal component and the vehicle lateral components ΔFx′i and ΔFy′i are expressed by the following equation (48) and equation using the sensitivity ki. (49)
ΔFx′i = (cosδi−kisinδi) ΔFxi = piΔFxi (pi = cosδi−kisinδi) (48)
ΔFy′i = (sinδi + kicosδi) ΔFxi = qiΔFxi (qi = sinδi + kicosδi) (49)
Can be expressed as:

Therefore, in the state of FIG. 3 with the steering angles δi of the wheels 1 to 4, the vehicle body longitudinal component Fx of the total tire force, the vehicle lateral component Fy of the total tire force, and the wheels 1 to 4 The sum M of the yaw moment around the center of gravity of the vehicle generated by the tire force is expressed by the following equations (50) to (52).
Fx = Fx'1 + Fx'2 + Fx'3 + Fx'4 (50)
Fy = Fy'1 + Fy'2 + Fy'3 + Fy'4 (51)
M = [(Fx′2 + Fx′4) − (Fx′1 + Fx′3)] × Lt / 2 + [(Fy′1 + Fy′2) × Lf− (Fy′3 + Fy′4) × Lr] (52)
Can be expressed as: However, the sum M of yaw moments is positive in the counterclockwise direction when the vehicle is viewed from above as shown in FIG.

Therefore, the braking / driving force Fx, the tire lateral force Fy, and the yaw moment M variation ΔFx, ΔFy, ΔM when the braking / driving force Fxi of each of the wheels 1 to 4 is changed by the correction amount ΔFxi, respectively, Using pi and qi of (49), the following equations (53) to (55)
ΔFx = ΔFx′1 + ΔFx′2 + ΔFx′3 + ΔFx′4 = p1ΔFx1 + p2ΔFx2 + p3ΔFx3 + p4ΔFx4 (53)
ΔFy = ΔFy′1 + ΔFy′2 + ΔFy′3 + ΔFy′4 = q1ΔFx1 + q2ΔFx2 + q3ΔFx3 + q4ΔFx4 (54)
ΔM = [(ΔFx′2 + ΔFx′4) − (ΔFx′1 + ΔFx′3)] × Lt / 2 + [(ΔFy′1 + ΔFy′2) × Lf− (ΔFy′3 + ΔFy′4) × Lr]
= [-(P1Lt / 2) + q1Lf] ΔFx1 + [(p2Lt / 2) + q2Lf] ΔFx2 + [− (p3Lt / 2) −q3Lr] ΔFx3 + [(p4Lt / 2) −q4Lr] ΔFx4 (55)
It is expressed as follows.

  The above formulas (53) to (55) can be summarized as the following formula (56).

上記した式（５６）の左辺、即ち制駆動力Ｆx、タイヤ横力ＦyおよびヨーモーメントＭの変化量ΔＦx,ΔＦy,ΔＭを０とした下記の式（５７）を満たす他の車輪２〜４の制駆動力補正量ΔＦx2,ΔＦx3,ΔＦx4は、式（５７）を他の車輪２〜４の制駆動力補正量ΔＦx2,ΔＦx3,ΔＦx4に関する連立方程式と見立てて解くと左前輪１の制駆動力ΔＦx1を用いて、下記の式（５８）〜式（６０）

Other wheels 2 to 4 satisfying the following expression (57) where the left side of the above expression (56), that is, the braking / driving force Fx, tire lateral force Fy, and yaw moment M variation ΔFx, ΔFy, ΔM is set to zero. The braking / driving force correction amounts ΔFx2, ΔFx3, ΔFx4 can be obtained by solving Equation (57) as simultaneous equations relating to the braking / driving force correction amounts ΔFx2, ΔFx3, ΔFx4 of the other wheels 2-4. Using the following formula (58) to formula (60)

ΔＦx2＝〔[ｑ1(ｐ4ｑ3−ｐ3ｑ4)Ｌ＋ｐ4(ｐ3ｑ1−ｐ1ｑ3)Ｌt]／[ｑ2(ｐ3ｑ4−ｐ4ｑ3)Ｌ＋ｐ3(ｐ2ｑ4−ｐ4ｑ2)Ｌt]〕×ΔＦx1 ・・・（５８）
ΔＦx3＝〔[ｑ4(ｐ2ｑ1−ｐ1ｑ2)Ｌ＋ｐ1(ｐ4ｑ2−ｐ2ｑ4)Ｌt]／[ｑ2(ｐ3ｑ4−ｐ4ｑ3)Ｌ＋ｐ3(ｐ2ｑ4−ｐ4ｑ2)Ｌt]〕×ΔＦx1 ・・・（５９）
ΔＦx4＝〔[ｑ3(ｐ1ｑ2−ｐ2ｑ1)Ｌ＋ｐ2(ｐ1ｑ3−ｐ3ｑ1)Ｌt]／[ｑ2(ｐ3ｑ4−ｐ4ｑ3)Ｌ＋ｐ3(ｐ2ｑ4−ｐ4ｑ2)Ｌt]〕×ΔＦx1 ・・・（６０）
の通り表される。

ΔFx2 = [[q1 (p4q3-p3q4) L + p4 (p3q1-p1q3) Lt] / [q2 (p3q4-p4q3) L + p3 (p2q4-p4q2) Lt]] × ΔFx1 (58)
ΔFx3 = [[q4 (p2q1-p1q2) L + p1 (p4q2-p2q4) Lt] / [q2 (p3q4-p4q3) L + p3 (p2q4-p4q2) Lt]] × ΔFx1 (59)
ΔFx4 = [[q3 (p1q2-p2q1) L + p2 (p1q3-p3q1) Lt] / [q2 (p3q4-p4q3) L + p3 (p2q4-p4q2) Lt]] × ΔFx1 (60)
It is expressed as follows.

As apparent from the equations (58) to (60), the braking / driving force correction amounts ΔFx1, ΔFx2, ΔFx3, and ΔFx4 of the wheels 1 to 4 are the following equations (20).
ΔFx1: ΔFx2: ΔFx3: ΔFx4
= Q2 (p3q4-p4q3) L + p3 (p2q4-p4q2) Lt: q1 (p4q3-p3q4) L + p4 (p3q1-p1q3) Lt: q4 (p2q1-p1q2) L + p1 (p4q2-p2q4) p1 (q3) p L + p2 (p1q3-p3q1) Lt
= [(Lt / L) (h4−h2) + h2 (h4−h3)] / (cosδ1−k1sinδ1): [(−Lt / L) (h3−h1) −h1 (h4−h3)] / (cosδ2− k2sinδ2): [(−Lt / L) (h4−h2) + h4 (h2−h1)] / (cosδ3−k3sinδ3): [(Lt / L) (h3−h1) + h3 (h2−h1)] / (cosδ4 -K4sinδ4) (20)
However, hi = (sinδi + kicosδi) / (cosδi−kisinδi)
When the ratio is taken as follows, the change amount ΔFx = ΔFy = ΔM = 0 of the braking / driving force Fx, the tire lateral force Fy, and the yaw moment M is obtained.

  Therefore, if the braking / driving force of any one wheel changes due to slipping of the wheels 1 to 4 or a motor failure, or if any braking / driving force of any one wheel is changed arbitrarily, braking / driving of the remaining three wheels If the force change amount ΔFxi is set to the ratio of the equation (20), the vehicle body longitudinal component Fx of the total tire force and the vehicle body of the total tire force even when the steering angle δi of each wheel is not negligible. The change in the sum M of the yaw moment around the center of gravity of the vehicle body generated by the lateral component Fy and the tire force of each wheel can be made zero.

By the way, in step S60 to step S70, the driving force distribution of each wheel 1 to 4 is set to the wheel load ratio obtained in step S30, that is, the following equations (61) to (64).
Fx1 = (W1 / (W1 + W2 + W3 + W4)) × tF (61)
Fx2 = (W2 / (W1 + W2 + W3 + W4)) × tF (62)
Fx3 = (W3 / (W1 + W2 + W3 + W4)) × tF (63)
Fx4 = (W4 / (W1 + W2 + W3 + W4)) × tF (64)
When the braking / driving force correction value ΔFsi is sufficiently small, that is, a slight slip or the like (when the flag flg is “1”), in step S150, as described below, The braking / driving force correction amount ΔFxi of the wheel may be obtained.

  That is, ignoring the roll (suspension characteristics) of the vehicle body and considering the movement of the horizontal plane of the vehicle running at a constant speed, the left and right wheels have the same rudder angle δi. It is known that the wheel slip angle βi (i = 1 to 4) can be approximated to be equal ("Motor Movement and Control", Chapter 3, Section 3.2.1, (Author) Masato Abe, (Publishing) Sankaido).

  As shown in FIGS. 7 and 9, the curve representing the relationship between the driving force and the tire lateral force is an ellipse as shown in FIG. 10 (the long radius of each wheel 1 to 4 is the wheel load Wi and the road surface friction coefficient μi). (Equal to μi × Wi multiplied by). Further, it can be approximated that the short radius of the ellipse also changes substantially in proportion to the wheel load Wi and the road surface friction coefficient μi.

  Therefore, if the slip angles of the left and right wheels are equal, an ellipse that approximates the relationship between the driving force and the tire lateral force as in the example of the left and right front wheels 1 and 2 shown in FIG. When the left and right wheel driving force distribution is made equal to the wheel load ratio, the sensitivity k i of the tire lateral force with respect to changes in driving force is substantially equal on the left and right wheels, that is, the sensitivity of each wheel 1-4 is k1 = k2 and k3 = k4. It can be approximated.

  This is a state in which the driving force is distributed so that the ratio of the driving force to the friction circle of the tire is equal between the left and right wheels, that is, the load on the left and right wheels is equalized. The resultant force (frictional force) between the driving force and tire lateral force generated on the tire contact surface basically does not exceed the wheel load of the tire, so the resultant force (frictional force) of the driving force and tire lateral force depends on the wheel load. The force generated by the left and right wheels equalizes the load on each of the left and right wheels, that is, the driving force is distributed so that slipping or locking is not likely to occur on either the left or right wheels. Refers to the state of

In such a traveling state (traveling state [1]), the steering angles of the wheels 1 to 4 can be approximated as δ1 = δ2, δ3 = δ4, and the sensitivity of the wheels 1 to 4 can be approximated as k1 = k2 and k3 = k4. The ratio of the longitudinal acceleration Xg, the lateral acceleration Yg, and the braking / driving force correction amounts ΔFx1, ΔFx2, ΔFx3, ΔFx4 of the wheels 1 to 4 that do not disturb the yaw moment M around the center of gravity of the vehicle in the step S150 is as follows. Equation (65)
ΔFx1: ΔFx2: ΔFx3: ΔFx4
= (Cosδ3-k3sinδ3) :-( cosδ3-k3sinδ3) :-( cosδ1-k1sinδ1) :( cosδ1-k1sinδ1) (65)
The correction amounts ΔFx1, ΔFx2, ΔFx3, and ΔFx4 of the braking / driving forces of the wheels 1 to 4 that suppress changes in the longitudinal and lateral acceleration and the yaw moment around the center of gravity of the vehicle can be determined with higher accuracy. Can be sought.

That is, when the steering angle δi of each wheel 1 to 4 can be approximated as δ1 = δ2, δ3 = δ4 and the sensitivity ki of each wheel 1 to 4 can be approximated as k1 = k2, k3 = k4, the above equation (20 ), The steering angles δi of the wheels 1 to 4 are set to δ1 = δ2, δ3 = δ4, and the sensitivities ki of the wheels 1 to 4 are set to k1 = k2 and k3 = k4. 67)
h1 = h2 = (sinδ1 + k1cosδ1) / (cosδ1−k1sinδ1), h3 = h4 = (sinδ3 + k3cosδ3) / (cosδ3−k3sinδ3) (∴δ1 = δ2, δ3 = δ4, k1 = k2, k3 = k4) (66) )

ΔFx1: ΔFx2: ΔFx3: ΔFx4
= [(Lt / L) (h4−h2) + h2 (h4−h3)] / (cosδ1−k1sinδ1): [(−Lt / L) (h3−h1) −h1 (h4−h3)] / (cosδ2− k2sinδ2): [(−Lt / L) (h4−h2) + h4 (h2−h1)] / (cosδ3−k3sinδ3): [(Lt / L) (h3−h1) + h3 (h2−h1)] / (cosδ4 -K4sinδ4)
= [(L / Lt) (h3−h1) + h1 (h3−h3)] / (cosδ1−k1sinδ1): [(−L / Lt) (h3−h1) −h1 (h3−h3)] / (cosδ1− k1sinδ1): [(−L / Lt) (h3−h1) + h3 (h1−h1)] / (cosδ3−k3sinδ3): [(L / Lt) (h3−h1) + h3 (h1−h1)] / (cosδ3) −k3sinδ3)
= 1 / (cosδ1-k1sinδ1):-1 / (cosδ1-k1sinδ1):-1 / (cosδ3-k3sinδ3): 1 / (cosδ3-k3sinδ3)
= (Cosδ3-k3sinδ3) :-( cosδ3-k3sinδ3) :-( cosδ1-k1sinδ1) :( cosδ1-k1sinδ1) (67)
(∴δ1 = δ2, δ3 = δ4, k1 = k2, k3 = k4, h1 = h2, h3 = h4)
This can be explained by the fact that the equation can be modified as follows.

  Further, as can be seen from FIG. 7 and FIG. 9, the slipping of each of the wheels 1 to 4 regardless of the case where the sliding angle βi of each of the wheels 1 to 4 is large and the driving force can be approximated to zero or the magnitude of the driving force. When the angle βi is small, for example, when the vehicle travels straight when the slip angle βi of each of the wheels 1 to 4 is sufficiently small, or when the wheel 1 to 4 has a large slip angle βi, the wheels 1 to 4 almost have braking / driving force. In a running state of the vehicle such as constant speed running or slow deceleration that is not output, the steering angles δi of the wheels 1 to 4 are in the relationship of δ1 = δ2, δ3 = δ4, and the sensitivity ki of each of the wheels 1 to 4 is k1 = k2. = K3 = k4 = 0.

  In such a running state of the vehicle (running state [2]), the front-rear direction acceleration Xg, the lateral acceleration Yg, and the yaw moment M around the center of gravity of the vehicle are not affected. The ratio of braking / driving force correction amounts ΔFx1, ΔFx2, ΔFx3, and ΔFx4 can be calculated more simply as cosδ3: -cosδ3: -cosδ1: cosδ1, and reduction in memory and processing of the computer (controller 8) that performs the calculation is expected. it can. In other words, as the sum of the driving force correction amounts of the left and right wheels is substantially zero for both the front and rear wheels, and the steering angles δ1 and δ2 of the front wheels 1 and 2 become larger than the steering angles δ3 and δ4 of the rear wheels 3 and 4, the right The driving force correction amount ΔFx4 for the rear wheel 4 is made smaller than the driving force correction amount ΔFx1 for the left front wheel 1.

That is, when the steering angle δi of each wheel 1 to 4 can be approximated as δ1 = δ2, δ3 = δ4 and the sensitivity ki of each wheel 1 to 4 can be approximated as k1 = k2 = k3 = k4 = 0, the above equation (20 ), When the sensitivity ki of each wheel 1 to 4 is set as k1 = k2 = k3 = k4 = 0, the following equation (68)
ΔFx1: ΔFx2: ΔFx3: ΔFx4
= 1: -1 :-( cosδ1-k1sinδ1) / (cosδ3-k3sinδ3) :( cosδ1-k1sinδ1) / (cosδ3-k3sinδ3)
= 1: -1: -cosδ1 / cosδ3: cosδ1 / cosδ3
= Cosδ3: -cosδ3: -cosδ1: cosδ1 (δk1 = k2 = k3 = k4 = 0) (68)
From this equation (37), as the absolute value of the steering angle δ1 = δ2 of the left and right front wheels 1, 2 increases with respect to the absolute value of the steering angle δ3 = δ4 of the left and right rear wheels 3, 4, the right It can be explained that the absolute value of the braking / driving force correction amount ΔFx4 of the rear wheel 4 is made smaller than the absolute value of the braking / driving force correction amount ΔFx1 of the left front wheel 1.

  As another example, a vehicle that steers only the front wheels that do not have the rear-wheel steering mechanism (steering actuator 16) can be cited. When applied to this vehicle, for example, in FIGS. 1 to 10, the values of the steering angles δ3 and δ4 of the rear wheels 3 and 4 may be constants (normally, the steering angle δ3 = δ4 = 0). Furthermore, when the vehicle that steers only the front wheels 1 and 2 is controlled based on FIGS. 1 to 10, the above-described equations (61) to (64) are obtained in steps S60 to S70 as described above. As described above, when the driving force distribution of each of the wheels 1 to 4 is obtained, in the case of a slight slip or the like (when the flag flg is “1”), as described below, each wheel 1 The braking / driving force correction amount ΔFxi of ˜4 may be obtained.

  That is, in the traveling state [1] in which the steering angles δi of the wheels 1 to 4 can be approximated as δ1 = δ2, δ3 = δ4 and the sensitivities ki of the wheels 1 to 4 can be approximated as k1 = k2, k3 = k4, If the rudder angle δi of the rear wheels 3 and 4 is zero (δ3 = δ4 = 0) and only the left and right front wheels 1 and 2 are in a traveling state (traveling state [3]), in step S150, The ratio of the braking / driving force correction amounts ΔFx1, ΔFx2, ΔFx3, ΔFx4 of the wheels 1 to 4 that do not disturb the yaw moment M around the center of gravity of the vehicle is 1: -1: -(Cosδ1-k1sinδ1): By setting (cosδ1-k1sinδ1), the braking / driving force correction amounts ΔFx1, ΔFx2, ΔFx3, ΔFx4 can be obtained more easily and the memory of the computer (controller 8) that performs the calculation And reduction of processing can be expected.

As described above, when the steering angles δi of the wheels 1 to 4 are δ1 = δ2, δ3 = δ4 = 0, and the sensitivities ki of the wheels 1 to 4 can be approximated as k1 = k2, k3 = k4, In the above equation (20), the steering angles δi of the wheels 1 to 4 can be set to be δ1 = δ2, δ3 = δ4 = 0, and the following equation (69)
ΔFx1: ΔFx2: ΔFx3: ΔFx4
= 1: -1 :-( cosδ1-k1sinδ1) / (cosδ3-k3sinδ3) :( cosδ1-k1sinδ1) / (cosδ3-k3sinδ3)
= 1: -1 :-( cos [delta] 1-k1sin [delta] 1) :( cos [delta] 1-k1sin [delta] 1)
(∴δ1 = δ2, δ3 = δ4 = 0) (69)
This can be explained by the fact that the equation can be modified as follows.

  Further, in the traveling state [3] in which the steering angle δi of each wheel 1 to 4 is δ1 = δ2, δ3 = δ4 = 0, and the sensitivity ki of each wheel 1 to 4 can be approximated to k1 = k2, k3 = k4. The left and right rear wheels 3 and 4 are in a running state in which the driving force is distributed between the left and right wheels 3 and 4 by the wheel load ratio of the left and right wheels. The left and right front wheels 1 and 2 have a large sliding angle βi and both the left and right wheels 1 and 2 In a driving state where the driving force is almost zero, the left and right front wheels 1 and 2 are in a driving state where the sliding angle βi is sufficiently small and the driving force distribution between the left and right wheels 1 and 2 is arbitrarily performed. Can be estimated as k1 = k2 = 0. Specific driving conditions to which these are applicable include straight driving with arbitrary driving force distribution, or the driving forces of the front wheels 1 and 2 are set to 0 for both the left and right wheels, and the rear wheels 3 and 4 are wheels of the left and right wheels. For example, the vehicle may turn while distributing the driving force between the left and right wheels according to the load ratio. In such a running state [4], the braking / driving force correction amount ΔFx1 of each wheel 1-4 that does not disturb the longitudinal acceleration Xg, the lateral acceleration Yg, and the yaw moment M around the center of gravity of the vehicle in step S150. , .DELTA.Fx2, .DELTA.Fx3, .DELTA.Fx4 is set to 1: -1: -cos .delta.1: cos.delta. Reduction of the memory and processing of the computer (controller 8) that performs the process can be expected.

That is, when the steering angle δi of each wheel 1 to 4 can be approximated as δ1 = δ2, δ3 = δ4 = 0 and the sensitivity ki of each wheel 1 to 4 can be approximated as k1 = k2 = 0, k3 = k4, In (20), if the sensitivity of the left and right front wheels 1 and 2 is set as k1 = k2 = 0, the following equation (70)
ΔFx1: ΔFx2: ΔFx3: ΔFx4
= 1: -1 :-( cos [delta] 1-k1sin [delta] 1) :( cos [delta] 1-k1sin [delta] 1)
= 1: -1: -cos .delta.1: cos .delta.1 (∴k1 = k2 = 0) (70)
As the absolute value of the front wheel rudder angle δ1 = δ2 increases from this equation (70), the absolute value of the braking / driving force correction amount ΔFx4 of the right rear wheel 4 becomes the braking / driving force correction amount of the left front wheel 1 It can be explained that the absolute value of ΔFx1 is reduced. This is because the driving force correction amount ΔFx4 of the right rear wheel 4 is changed to that of the left front wheel 1 as the sum of the driving force correction amounts of the left and right wheels is substantially zero for both the front and rear wheels and the steering angles δ1 and δ2 of the front wheels 1 and 2 are increased. This means a configuration in which the driving force correction amount ΔFx1 is reduced.

  As described above, in a vehicle having no rear wheel steering mechanism (steering actuator 16), when the driving force correction amount is obtained by the above-described prior art (Japanese Patent Laid-Open No. 10-295004) and the prior application technique, FIG. A result obtained by performing a simulation comparison with the case where the driving force correction amount is obtained based on the flowchart will be described below.

  As described above, this simulation assumes a vehicle in which the rear wheel steering mechanism (steering actuator 16) is not provided in the vehicle of FIG. 1 and the steering angles of the rear wheels 3 and 4 are fixed at δ3 = δ4 = 0. went. Further, the running conditions in which the simulation was performed were that the front wheels 1 and 2 were largely turned to the left (steering angles δ 1 and δ 2> 0), and the driving force sum of the right wheels 2 and 4 was larger than the driving force sum of the left wheels 1 and 3. Assuming that the driving force of the right rear wheel 4 suddenly becomes zero (Fx4 → 0 (Fx4 → 0 (Fx2 + Fx4> Fx1 + Fx3)) from the state of FIG. ΔFx4≈−750 [N])), and the driving force correction amounts for the remaining three wheels were determined based on the above-described prior art, the prior application, and the flowchart of FIG. In the case of using the prior application technique, the steering angle δ1 = δ2 = 0 was set using the flowchart of FIG.

  FIG. 12 shows vehicle speed, vehicle body longitudinal acceleration, vehicle body lateral acceleration, yaw rate, vehicle body slip angle, and driving force change of each wheel at this time. According to FIG. 12, when the driving force of the right rear wheel is reduced sufficiently slowly from the state of FIG. 11, the driving is performed based on the flowchart of FIG. 2 as compared with the prior art and the prior application. It was confirmed that the change in the force correction amount was able to reduce the change in any of the vehicle speed, the vehicle longitudinal acceleration, the vehicle lateral acceleration, the yaw rate, and the vehicle slip angle.

  In the present embodiment, the following effects can be achieved.

  (A) A four-wheel independent drive vehicle equipped with braking / driving force determining means (steps S20 to S70) capable of independently driving the four wheels and determining the braking / driving force of each of the four wheels on the basis of a motion request of the vehicle. In the driving force distribution device, tire lateral force sensitivity estimating means for estimating tire lateral force sensitivities k1, k2, k3, k4 with respect to changes in driving force of the left front wheel 1, the right front wheel 2, the left rear wheel 3, and the right rear wheel 4. (Steps S80 to S90, S140), the steering angles δ1, δ2, δ3, δ4 of the left front wheel 1, the right front wheel 2, the left rear wheel 3, and the right rear wheel 4 and the tire lateral force sensitivity estimation means. Means (steps S150 to S160) for correcting the driving forces of the left front wheel 1, the right front wheel 2, the left rear wheel 3, and the right rear wheel 4 based on the sensitivities k1, k2, k3, and k4. When changing the braking / driving force determined by the braking / driving force determining means, the driving force correction The steps are the steering angles δ1, δ2, δ3, δ4 of the left front wheel 1, the right front wheel 2, the left rear wheel 3, and the right rear wheel 4 and the sensitivities k1, k2, k3 estimated by the tire lateral force sensitivity estimation means. , K4 so as to correct the driving force correction amounts ΔFx1, ΔFx2, ΔFx3, ΔFx4 of the left front wheel 1, the right front wheel 2, the left rear wheel 3, and the right rear wheel 4 so as to satisfy the motion demand of the vehicle. did. By adopting such a configuration, even when the steering angle δi (i = 1 to 4) of each of the wheels 1 to 4 is so large that it cannot be ignored, not only the acceleration in the longitudinal direction but also the tire when the braking / driving force is corrected It is possible to suppress changes in lateral acceleration and yaw moment around the center of gravity of the vehicle that occur due to changes in lateral force, and to prevent unintended disturbances in vehicle behavior and improve drivability.

  (A) The steering angles δ1 and δ2 of the left and right front wheels 1 and 2 and the steering angles δ3 and δ4 of the left and right rear wheels 3 and 4 are substantially equal for the left and right wheels, respectively, and the difference between the sensitivity k1 and k2 of the left and right front wheels 1 and 2 When the difference between the sensitivity k3 and k4 of the rear wheels 3 and 4 is substantially zero, the driving force correction amount for each of the left front wheel 1, the right front wheel 2, the left rear wheel 3 and the right rear wheel 4 by the driving force correction means. The ratio of ΔFx1, ΔFx2, ΔFx3, and ΔFx4 is expressed as follows. For example, when the slip angle βi of the left and right wheels is equal and the driving force distribution of the left and right wheels is equal to the wheel load ratio Wi, braking / driving is performed to prevent any one of the wheels 1 to 4 from slipping or locking. When correcting the force, each wheel 1 that suppresses changes in the longitudinal and lateral acceleration and the yaw moment around the center of gravity of the vehicle. Correction amount of longitudinal force 4 can be determined more accurately.

  (C) When the steering angles δ1 and δ2 of the left and right front wheels 1 and 2 and the steering angles δ3 and δ4 of the left and right rear wheels 3 and 4 are substantially equal for the left and right wheels, the respective wheels estimated by the tire lateral force sensitivity estimation means When the sensitivities k1, k2, k3, and k4 of 1 to 4 are all about 0, the sum of the driving force correction amounts of the left and right wheels by the driving force correcting means is substantially 0 for both the front and rear wheels and As the steering angles δ1 and δ2 of the left and right rear wheels 3 and 4 become larger than the steering angles δ3 and δ4 of the left and right rear wheels 3, the driving force correction amount of each of the rear wheels 3, 4 is set to the diagonal position of the front wheels 1, 2. Decrease the driving force correction amount. That is, the ratio of the driving force correction amounts ΔFx1, ΔFx2, ΔFx3, and ΔFx4 for the left front wheel 1, the right front wheel 2, the left rear wheel 3, and the right rear wheel 4 is expressed as follows: ΔFx1: ΔFx2: ΔFx3: ΔFx4 = cosδ3: −cosδ3: − The relationship of cosδ1: cosδ1, for example, when the sliding angle βi of each of the wheels 1 to 4 is large and the driving force can be approximated to 0, or regardless of the magnitude of the driving force, the sliding angle βi of each of the wheels 1-4. Each wheel suppresses changes in longitudinal and lateral acceleration and yaw moment around the center of gravity of the vehicle when correcting braking / driving force to prevent slipping or locking of any of the wheels 1 to 4 when the wheel is small The braking / driving force correction amount ΔFxi of 1 to 4 can be obtained more easily, and a reduction in the memory and processing of the computer (controller 8) that performs the calculation can be expected.

  (D) The rudder angles δ1 and δ2 of the left and right front wheels 1 and 2 are substantially equal, and the rudder angles δ3 and δ4 of the left and right rear wheels 3 and 4 are both substantially zero, and the difference between the sensitivity k1 and k2 of the left and right front wheels 1 and 2 When the difference between the sensitivity k3 and k4 of the left and right rear wheels 3 and 4 is substantially zero, the driving force of each of the left front wheel 1, right front wheel 2, left rear wheel 3 and right rear wheel 4 by the driving force correction means. By setting the ratio of the correction amounts ΔFx1, ΔFx2, ΔFx3, and ΔFx4 to the relationship of ΔFx1: ΔFx2: ΔFx3: ΔFx4 = 1: −1: − (cosδ1−k1sinδ1): (cosδ1−k1sinδ1), When the braking / driving force is corrected to prevent slipping or locking of any of the wheels 1 to 4 when steering only the vehicle, the longitudinal and lateral acceleration and the change in the yaw moment around the vehicle center of gravity are suppressed. A computer (controller) that can calculate the braking / driving force correction amount ΔFxi of each of the wheels 1 to 4 more easily. Reduction of memory and processing of 8) can be expected.

  (E) The rudder angles δ1 and δ2 of the left and right front wheels 1 and 2 are substantially equal, the rudder angles δ3 and δ4 of the left and right rear wheels 3 and 4 are both substantially zero, and the sensitivity k1 and k2 of the left and right front wheels 1 and 2 are substantially both. When the left and right rear wheels 3 and 4 have substantially equal sensitivities k3 and k4, the sum of the driving force correction amounts of the left and right wheels by the driving force correcting means is substantially 0 for both the front and rear wheels and As the steering angles δ1 and δ2 increase, the driving force correction amount of the rear wheels 3 and 4 is made smaller than the driving force correction amount of the front wheels in the diagonal positions. That is, the ratio of the driving force correction amounts ΔFx1, ΔFx2, ΔFx3, and ΔFx4 of the left front wheel 1, the right front wheel 2, the left rear wheel 3, and the right rear wheel 4 is expressed as follows: ΔFx1: ΔFx2: ΔFx3: ΔFx4 = 1: −1: − By setting the relationship of cosδ1: cosδ1, for example, the left and right front wheels 1 and 2 are in a traveling state where the sliding angle βi is large and the driving force of both the left and right wheels is almost zero, or the sliding angle βi is sufficiently small and the left and right wheels 1 2 is arbitrarily distributed, and the left and right rear wheels 3 and 4 are in a running state where the left and right wheels 3 and 4 are distributed with the wheel load ratio Wi. When correcting the braking / driving force in order to prevent slipping or locking of the wheels 1 to 4, the braking / driving force of each wheel 1-4 that suppresses changes in the longitudinal and lateral accelerations and the yaw moment around the center of gravity of the vehicle A computer (controller) that can calculate the correction amount ΔFxi more easily and performs calculations. 8) Memory and processing can be reduced.

(F) The driving force correcting means is estimated by the steering angle δ1, δ2, δ3, δ4 of the left front wheel 1, the right front wheel 2, the left rear wheel 3, and the right rear wheel 4 and the tire lateral force sensitivity estimating means. Based on the sensitivity k1, k2, k3, k4, the ratio of the driving force correction amounts ΔFx1, ΔFx2, ΔFx3, ΔFx4 of the left front wheel 1, the right front wheel 2, the left rear wheel 3, and the right rear wheel 4 is determined as a four-wheel independent drive vehicle. The tread length is Lt and the wheelbase length is L.
ΔFx1: ΔFx2: ΔFx3: ΔFx4
= [(Lt / L) (h4−h2) + h2 (h4−h3)] / (cosδ1−k1sinδ1): − [(Lt / L) (h3−h1) + h1 (h4−h3)] / (cosδ2−k2sinδ2) ):-[(Lt / L) (h4−h2) + h4 (h2−h1)] / (cosδ3−k3sinδ3): [(Lt / L) (h3−h1) + h3 (h2−h1)] / (cosδ4− k4sinδ4)
However, hi = (sinδi + kicosδi) / (cosδi−kisinδi)
By setting so as to satisfy the following relationship, the braking / driving force is corrected in order to prevent slipping or locking of any of the wheels 1 to 4 even in each traveling state that is not included in the above (a) to (e). In this case, the braking / driving force correction amount ΔFxi of each of the wheels 1 to 4 that suppresses changes in the longitudinal and lateral accelerations and the yaw moment around the center of gravity of the vehicle can be obtained with high accuracy.

1 is a system configuration diagram of a driving force distribution device for a four-wheel independent drive vehicle according to an embodiment of the present invention. The flowchart of the driving force distribution control performed with a controller. The flowchart following FIG. 2A of the driving force distribution control performed by a controller. Explanatory drawing showing the driving force of each wheel applied to a four-wheel independent drive vehicle, tire lateral force, and yaw moment around the center of gravity of the vehicle. A map showing the driver's required driving force according to the amount of accelerator pedal depression and the vehicle speed. A map showing the driver's required driving force according to the amount of brake pedal depression. The map showing the target value of the left and right driving force difference of the vehicle according to the steering rotation angle and the vehicle speed. The figure showing the relationship between the braking / driving force memorize | stored in the controller, and a tire lateral force. Explanatory drawing which shows the vehicle body front-back direction component and vehicle body horizontal direction component of tire force when the steering angle of each wheel is cut by δi (i = 1 to 4). The characteristic view showing the relationship between braking / driving force and tire lateral force. The characteristic view explaining the state where the relationship between braking / driving force and tire lateral force becomes an ellipse that is approximately similar to the left and right front wheels. Explanatory drawing which shows the state from which the driving force of the right rear wheel suddenly became 0 from the driving | running | working state which attached the left-right driving force difference and made the left turn at constant speed. FIG. 11 shows the simulation results of the vehicle speed, the vehicle longitudinal acceleration, the vehicle lateral acceleration, the yaw rate, the vehicle slip angle, and the driving force change of each wheel when the driving force of the right rear wheel is reduced sufficiently slowly from the state of FIG. FIG. An explanatory view showing the driving force and lateral force applied to the four-wheel independent drive vehicle and the yaw moment around the center of gravity of the vehicle under the assumption that the steering angle δi (i = 1 to 4) of each wheel is sufficiently small.

Explanation of symbols

1-4 Wheel 5 Steering 6 Accelerator Pedal 7 Brake Pedal 8 Controller 9 Battery 11-14 Motor 15 Steering Gear 16 Steering Actuator 21-24 Wheel Speed Sensor 25 Steering Angle Sensor 26 Accelerator Stroke Sensor 27 Brake Stroke Sensor 31-34 Inverter 41- 44 Rudder angle sensor 100 Acceleration sensor 101 Yaw rate sensor

Claims (8)

In the driving force distribution device for a four-wheel independent drive vehicle, which is capable of independently driving the four wheels, and includes braking / driving force determining means for determining the braking / driving force of each of the four wheels based on the motion demand of the vehicle.
Tire lateral force sensitivity estimating means for estimating the sensitivity k1, k2, k3, k4 of the tire lateral force with respect to changes in driving force of the left front wheel, right front wheel, left rear wheel, and right rear wheel,
Based on the steering angles δ1, δ2, δ3, δ4 of the left front wheel, the right front wheel, the left rear wheel, and the right rear wheel and the sensitivity k1, k2, k3, k4 estimated by the tire lateral force sensitivity estimation means, Means for correcting the driving force of each of the front wheel, the right front wheel, the left rear wheel, and the right rear wheel,
In the case of changing the braking / driving force determined by the braking / driving force determining means, the driving force correcting means includes the steering angles δ1, δ2, δ3 of the left front wheel, the right front wheel, the left rear wheel, and the right rear wheel, respectively. Based on δ4 and the sensitivity k1, k2, k3, k4 estimated by the tire lateral force sensitivity estimating means, the left front wheel, the right front wheel, the left rear wheel, and the right rear wheel A driving force distribution device for a four-wheel independent driving vehicle, wherein only the driving force correction amounts ΔFx1, ΔFx2, ΔFx3, and ΔFx4 are corrected. The driving force correcting means is such that the steering angles δ1, δ2 of the left and right front wheels and the steering angles δ3, δ4 of the left and right rear wheels are substantially equal to the left and right wheels, and the difference between the sensitivity k1 and k2 of the left and right front wheels and the sensitivity k3 And k4 are almost zero, the ratio of the driving force correction amounts ΔFx1, ΔFx2, ΔFx3, ΔFx4 for the left front wheel, right front wheel, left rear wheel, and right rear wheel is
ΔFx1: ΔFx2: ΔFx3: ΔFx4
= (Cosδ3-k3sinδ3) :-( cosδ3-k3sinδ3) :-( cosδ1-k1sinδ1) :( cosδ1-k1sinδ1)
The drive power distribution device for a four-wheel independent drive vehicle according to claim 1, wherein:   The driving force correction means is configured to detect the sensitivity of each wheel estimated by the tire lateral force sensitivity estimation means when the steering angles δ1 and δ2 of the left and right front wheels and the steering angles δ3 and δ4 of the left and right rear wheels are substantially equal to the left and right wheels, respectively. When k1, k2, k3, and k4 are all zero, the sum of the driving force correction amounts for the left and right wheels is substantially zero for both the front and rear wheels, and the rudder angles δ1 and δ2 of the left and right front wheels are the rudder angles of the left and right rear wheels. 3. The driving force correction amount for each of the rear wheels is decreased with respect to the driving force correction amount for the front wheels at the diagonal positions as δ3 and δ4 increase. The drive power distribution device for the four-wheel independent drive vehicle described.   The driving force correction means is configured to detect the sensitivity of each wheel estimated by the tire lateral force sensitivity estimation means when the steering angles δ1 and δ2 of the left and right front wheels and the steering angles δ3 and δ4 of the left and right rear wheels are substantially equal to the left and right wheels, respectively. When k1, k2, k3, and k4 are all substantially zero, the ratio of the driving force correction amounts ΔFx1, ΔFx2, ΔFx3, and ΔFx4 for the left front wheel, the right front wheel, the left rear wheel, and the right rear wheel is expressed as ΔFx1: ΔFx2 The driving force distribution device for a four-wheel independent drive vehicle according to claim 1 or 2, wherein: ΔFx3: ΔFx4 = cosδ3: -cosδ3: -cosδ1: cosδ1. The driving force correction means is such that the steering angles δ1 and δ2 of the left and right front wheels are substantially equal and the steering angles δ3 and δ4 of the left and right rear wheels are both substantially zero, the difference between the sensitivity k1 and k2 of the left and right front wheels, When the difference between the sensitivities k3 and k4 is substantially zero, the ratio of the driving force correction amounts ΔFx1, ΔFx2, ΔFx3, ΔFx4 for the left front wheel, the right front wheel, the left rear wheel, and the right rear wheel is calculated as follows:
ΔFx1: ΔFx2: ΔFx3: ΔFx4 = 1: −1: − (cosδ1−k1sinδ1): (cosδ1−k1sinδ1)
The driving force distribution device for a four-wheel independent drive vehicle according to claim 1 or 2, wherein the relationship is as follows.   The driving force correcting means is such that the steering angles δ1 and δ2 of the left and right front wheels are substantially equal, the steering angles δ3 and δ4 of the left and right rear wheels are both substantially zero, the sensitivity k1 and k2 of the left and right front wheels are both substantially zero, and When the rear wheel sensitivities k3 and k4 are substantially equal, the sum of the driving force correction amounts for the left and right wheels becomes substantially zero for both the front and rear wheels, and as the steering angles δ1 and δ2 of the left and right front wheels increase, The driving force distribution device for a four-wheel independent drive vehicle according to claim 1 or 2, wherein the driving force correction amount of the four-wheel independent drive vehicle is made smaller than the driving force correction amount of the front wheel at the diagonal position. The driving force correcting means is such that the steering angles δ1 and δ2 of the left and right front wheels are substantially equal, the steering angles δ3 and δ4 of the left and right rear wheels are both substantially zero, the sensitivity k1 and k2 of the left and right front wheels are both substantially zero, and When the rear wheel sensitivities k3 and k4 are substantially equal, the ratios of the driving force correction amounts ΔFx1, ΔFx2, ΔFx3, ΔFx4 for the left front wheel, the right front wheel, the left rear wheel, and the right rear wheel,
ΔFx1: ΔFx2: ΔFx3: ΔFx4 = 1: −1: −cos δ1: cos δ1
The driving force distribution device for a four-wheel independent drive vehicle according to claim 1 or 2, wherein the relationship is as follows. The driving force correction means includes steering angles δ1, δ2, δ3, δ4 for the left front wheel, right front wheel, left rear wheel, and right rear wheel, and sensitivities k1, k2, k3 estimated by the tire lateral force sensitivity estimation means. , K4, the ratio of the driving force correction amounts ΔFx1, ΔFx2, ΔFx3, and ΔFx4 for the left front wheel, right front wheel, left rear wheel, and right rear wheel, the tread length of the four-wheel independent drive vehicle is Lt, and the wheel base length Let L be
ΔFx1: ΔFx2: ΔFx3: ΔFx4
= [(Lt / L) (h4−h2) + h2 (h4−h3)] / (cosδ1−k1sinδ1): − [(Lt / L) (h3−h1) + h1 (h4−h3)] / (cosδ2−k2sinδ2) ):-[(Lt / L) (h4−h2) + h4 (h2−h1)] / (cosδ3−k3sinδ3): [(Lt / L) (h3−h1) + h3 (h2−h1)] / (cosδ4− k4sinδ4)
However, hi = (sinδi + kicosδi) / (cosδi−kisinδi)
The driving force distribution device for a four-wheel independent drive vehicle according to claim 1, wherein the driving force distribution device is set so as to satisfy the following relationship.

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