JP4867369B2 - Driving force control device for electric vehicle, automobile and driving force control method for electric vehicle - Google Patents

Description

  The present invention relates to a driving force control device for an electric vehicle that performs driving force control for controlling the driving force of driving wheels, an automobile including the same, and a driving force control method for an electric vehicle.

As a conventional driving force control device for an electric vehicle, an apparatus that performs antilock control or traction control according to the variation width of the wheel speed of a wheel is known (see, for example, Patent Document 1).
In this conventional apparatus, the difference between the highest and the third of the wheel speeds of the four wheels is acquired as the wheel speed variation width, and the wheel speed variation width is set within a certain range so that each wheel is within a certain range. Anti-lock control that suppresses wheel slip during braking is performed by controlling the braking force.

In the traction control, the difference between the lowest and the third lowest wheel speeds of the four wheels is adopted as the wheel speed variation width so that the wheel speed variation width falls within a substantially constant range. By controlling the driving force of each wheel, wheel slip during driving is suppressed.
JP-A-10-29524

However, when slip control such as antilock control or traction control is performed so that the variation in wheel speed is within a predetermined range as in the conventional driving force control device for an electric vehicle, the road surface from the wheel to the left and right driving wheels. There may be a difference in the driving force transmitted to.
For example, when the vehicle starts and accelerates with the left and right drive wheels having different road surface friction coefficients, the left and right drive wheels have different wheel speeds, and the traction control operation weakens the output drive force of the low μ road drive wheels. At this time, a large driving force is transmitted from the wheel to the road surface on the high μ road side, whereas a driving force transmitted from the wheel to the road surface is small on the low μ road side, so there is a large difference in the driving force transmitted from the wheel to the road surface on the left and right driving wheels. Occurs.

  The movement of the vehicle is based on a force applied to the vehicle by a reaction force from the road surface. If there is a difference in the driving force transmitted from the wheels to the road surface between the left and right drive wheels as described above, the road reaction force on the low μ road side will be smaller than the road reaction force on the high μ road side, so the yaw moment will be appear. Therefore, even when the steering is maintained in the straight traveling position, the vehicle turns to the low μ road side and the vehicle behavior becomes unstable.

  Therefore, the present invention provides a driving force control device for an electric vehicle capable of preventing the vehicle behavior from becoming unstable during the slip control operation, an automobile equipped with the same, and a driving force control method for the electric vehicle. It is an issue.

In order to solve the above problems, a driving force control device for an electric vehicle according to the present invention includes :
As the slip ratio of left-right driving wheel falls within a predetermined range, a driving force control device for an electric vehicle including a driving force control means for controlling the electric motor as a driving source of the driving wheel,
Based on the motor operation detection means for detecting the operation state of the electric motor and the operation state of the electric motor detected by the motor operation detection means, the driving force transmitted from the left and right drive wheels to the road surface is calculated. The control amount of the driving force control by the driving force control unit is corrected so that the difference between the driving force of the driving force calculation unit and the driving force of the left and right driving wheels calculated by the driving force calculation unit becomes a predetermined target driving force difference. Control amount correction means,
The control amount correction means performs a feedback control based on the current driving force transmitted from the driving wheel to the road surface, and calculates a first correction amount for correcting the control amount of the driving force control. Calculation means and second correction amount calculation means for calculating a second correction amount for correcting the control amount of the driving force control by performing feedforward control based on a future driving force transmitted from the driving wheel to the road surface The second correction amount calculating means includes a change in the output driving force of the electric motor in a predetermined past reference period, and a change in the driving force transmitted from the driving wheel to the road surface in the reference period. The future driving force transmitted from the driving wheel to the road surface is estimated on the basis of the driving force transmission characteristic obtained from the above and the control amount of the next driving force control.

Also, automobile according to the present invention,
So that the slip rate of the left and right drive wheels of the vehicle generated by OPERATION's accelerator operation is within the predetermined range, the driving force of the electric vehicle having a driving force control means for controlling the electric motor as a driving source of the driving wheel A car equipped with a control device,
Based on the motor operation detection means for detecting the operation state of the electric motor and the operation state of the electric motor detected by the motor operation detection means, the driving force transmitted from the left and right drive wheels to the road surface is calculated. The control amount of the driving force control by the driving force control unit is corrected so that the difference between the driving force of the driving force calculation unit and the driving force of the left and right driving wheels calculated by the driving force calculation unit becomes a predetermined target driving force difference. Control amount correction means,
The control amount correction means performs a feedback control based on the current driving force transmitted from the driving wheel to the road surface, and calculates a first correction amount for correcting the control amount of the driving force control. Calculation means and second correction amount calculation means for calculating a second correction amount for correcting the control amount of the driving force control by performing feedforward control based on a future driving force transmitted from the driving wheel to the road surface The second correction amount calculating means includes a change in the output driving force of the electric motor in a predetermined past reference period, and a change in the driving force transmitted from the driving wheel to the road surface in the reference period. The future driving force transmitted from the driving wheel to the road surface is estimated on the basis of the driving force transmission characteristic obtained from the above and the control amount of the next driving force control.

The driving force control method for an electric vehicle according to the present invention includes :
As the slip ratio of left-right driving wheel falls within a predetermined range, a driving force control method for an electric vehicle which performs driving force control for controlling the electric motor as a driving source of the driving wheel,
The driving force transmitted from the left and right driving wheels to the road surface is calculated based on the operating state of the electric motor, and the driving force is set so that the difference between the driving forces of the left and right driving wheels becomes a predetermined target driving force difference. When correcting the control amount of force control,
Feedback control is performed based on the current driving force transmitted from the driving wheel to the road surface, a first correction amount for correcting the control amount of the driving force control is calculated, and the electric motor in a past predetermined reference period Based on a driving force transmission characteristic obtained from a change in the output driving force of the driving force, a change in driving force transmitted from the driving wheel to the road surface during the reference period, and a control amount of the next driving force control. A second driving force that estimates the future driving force transmitted from the wheel to the road surface, performs feedforward control based on the future driving force transmitted from the driving wheel to the road surface, and corrects the control amount of the driving force control. The correction amount is calculated.

According to the driving force control apparatus for an electric vehicle according to the present invention, since the corrected driving force controlled variable such that the difference of the driving force transmitted to the road surface from left to right driving wheel becomes the target driving force difference, the driving force control Thus, when the driving force of one of the left and right driving wheels becomes smaller than the driver command value, the driving force of the other driving wheel is controlled so that the driving force difference follows the target driving force difference. As a result, for example, in starting acceleration on a split μ road, when the driving force of the driving wheel on the low μ road side is controlled to decrease by driving force control, the driving force transmitted from the driving wheel on the low μ road side to the road surface is reduced. It is possible to suppress the occurrence of a yaw moment that is not intended by the driver, such as the vehicle turning to the low μ road side due to being smaller than the high μ road side.
Further, according to the driving force control apparatus for an electric vehicle according to the present invention, the driving force difference transmitted from the left and right driving wheels to the road surface becomes the target driving force difference by using both feedback control and feedforward control. Since the force difference control is performed, the driving force difference between the left and right driving wheels can be made to follow the target driving force difference more appropriately. In addition, from the driving wheel using the driving force transmission characteristics obtained from the change in the output driving force of the electric motor in the past predetermined reference period and the change in the driving force transmitted from the driving wheel to the road surface in the reference period. Since the future driving force transmitted to the road surface is estimated, it is possible to accurately estimate the future driving force by taking advantage of the property of accurately modeling the output characteristics of the electric motor.

Further, according to the vehicle of the present invention, the difference in driving force transmitted from the left and right driving wheels to the road surface when the driving force of either one of the left and right driving wheels becomes smaller than the driver command value by the driving force control. The driving force of the other driving wheel can be controlled so as to appropriately follow the target driving force difference . Therefore, it is possible to effectively suppress the yaw moment that is not intended by the driver, and to stabilize the vehicle behavior .

Further, according to the driving force control method for an electric vehicle according to the present invention, when either driving force of the left and right driving wheels becomes smaller than the driver command value by the driving force control, the driving force is transmitted from the left and right driving wheels to the road surface. The driving force of the other driving wheel can be controlled so that the difference in driving force appropriately follows the target driving force difference . Therefore, it is possible to effectively suppress the yaw moment that is not intended by the driver, and to stabilize the vehicle behavior .

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
(Constitution)
FIG. 1 is a block diagram showing a functional configuration of a driving force control apparatus for an electric vehicle according to the present invention.
In FIG. 1, the driving force control device for an electric vehicle includes a motor operation detection unit 101, a driving operation amount detection unit 102, a TCS control unit 103, a driving force calculation unit 104, a driving force difference adjustment unit 105, And a motor 106.

The motor operation detection unit 101 detects the operation state of the electric motor 106 that drives the driving wheels of the vehicle.
The driving operation amount detection unit 102 detects the operation amounts (steering angle, accelerator pedal operation amount, brake pedal operation amount) of devices such as a steering wheel, an accelerator pedal, and a brake pedal that are operated by the driver during vehicle travel.

The motor operation detection unit 101 passes the detection result to the TCS control unit 103 and the driving force calculation unit, and the driving operation amount detection unit 102 passes the detection result to the TCS control unit 103.
The TCS control unit 103 calculates a driver command torque corresponding to the driver's request based on the detection result of the driving operation amount detection unit 102. Further, a drive torque command for calculating the slip ratio of the drive wheels driven by the electric motor 106 and adjusting the output torque of the electric motor 106 so that the slip ratio falls within a predetermined range using the driver command torque. Is calculated.

The driving force calculation unit 104 calculates the driving force transmitted from the driving wheels to the road surface according to the operating state of the electric motor 106.
The driving force difference adjusting unit 105 outputs the output of the electric motor 106 so that the driving force difference between the left and right driving wheels obtained based on the driving force calculated by the driving force calculating unit 104 becomes a predetermined target driving force difference. A drive torque command for adjusting the torque is calculated. Then, the drive torque command calculated by the TCS control unit 103 is corrected by the drive torque command, and the electric motor 106 is driven.

The electric motor 106 is disposed independently on the left and right drive wheels of the vehicle, and individually controls the driving force applied to the left and right drive wheels.
In FIG. 1, the motor operation detection unit 101 constitutes a motor operation detection unit, the driving operation amount detection unit 102 constitutes an operation amount detection unit, and the TCS control unit 103 constitutes a driving force control unit. The force calculation unit 104 constitutes a driving force calculation unit, and the driving force difference adjustment unit 105 constitutes a control amount correction unit. The motor operation detection unit 101, the driving operation amount detection unit 102, the TCS control unit 103, the driving force calculation unit 104, and the driving force difference adjustment unit 105 constitute a driving force difference control unit.

FIG. 2 is a schematic configuration diagram of a vehicle to which the driving force control device for an electric vehicle according to the embodiment of the present invention is applied. In FIG. The left and right rear wheels 2RL and 2RR are drive wheels that are individually driven by the electric motors 3RL and 3RR, and the electric motors 3RL and 3RR are designed integrally with the drive wheels 2RL and 2RR, respectively.
The motor inverters 4RL and 4RR output a drive current for driving the electric motors 3RL and 3RR to the electric motors 3RL and 3RR based on a drive signal output from the control unit 20 described later. The motor inverters 4RL and 4RR output the drive current values of the electric motors 3RL and 3RR to the control unit 20 as the operating states of the electric motors 3RL and 3RR.

The power supply unit 21 supplies a drive current for driving the electric motors 3RL and 3RR to the motor inverters 4RL and 4RR.
Reference numerals 5RL and 5RR in the figure denote suspensions that suspend the drive wheels 2RL and 2RR from the vehicle body.
The vehicle 1 includes a steering wheel 10 that is steered by the driver to indicate the traveling direction of the vehicle 1, a steering angle sensor 11 that detects an angle (steering angle δ) by which the driver steers the steering wheel 10, and An accelerator pedal sensor 12 for detecting an operation amount ACC of an unillustrated accelerator pedal operated by a driver, a brake pedal sensor 13 for detecting an operation amount BRK of an unillustrated brake pedal operated by a driver, and the behavior of the vehicle 1 are measured. The vehicle behavior sensor 14 is provided, and detection signals from the various sensors are output to the control unit 20.

  Then, the control unit 20 controls the traction control system for suppressing the acceleration slip of the vehicle 1 based on the operation state of the electric motors 3RL, 3RR and the driving operation amount such as the accelerator pedal operation amount ACC by the driver ( TCS control) and driving force difference control for controlling the output torque of the electric motors 3RL and 3RR so that the difference in driving force transmitted from the wheels of the left and right driving wheels 2RL and 2RR to the road surface becomes a predetermined target driving force difference. Driving force control for controlling the driving force of the motors 3RL and 3RR is executed.

  FIG. 3 is a control block diagram of the driving force difference control. In this driving force difference control, as shown in FIG. 3, the current driving force transmitted from the driving wheels to the road surface is calculated and the output torque of the electric motor is calculated by taking advantage of the ability to accurately model the output characteristics of the electric motor. A control method is used that uses both feedback control for controlling the motor and feedforward control for estimating the future driving force that will be transmitted from the drive wheels to the road surface and controlling the output torque of the electric motor.

FIG. 4 is a flowchart showing a driving force control process executed by the control unit 20. This driving force control process is repeatedly executed when the ignition switch of the vehicle 1 is in the on state.
First, in step S1, the control unit 20 calculates the driving force Td transmitted from the driving wheels 2RL and 2RR to the road surface based on the operating state of the electric motors 3RL and 3RR. The driving force Td transmitted to the road surface is calculated based on the following equation.

Td = KI−J _w (dV _w / dt) (1)
Here, K is the motor torque constant, I is the drive current of the motor, the J _w inertia of the driven rotating system, the V _w is the wheel speed.
FIG. 5 is a control block diagram showing the concept of a method for calculating the driving force Td transmitted from the wheel to the road surface. Thus, in the above equation (1), the torque (KI) generated by the motor is used as the force for turning the wheel (J _w (dV _w / dt)) and the force (Td) transmitted from the wheel to the road surface. It is expressed based on.

Next, in step S2, the control unit 20 calculates the drive torque command T _ACC of the electric motor corresponding to the driver's request, so-called driver command torque, according to the accelerator pedal operation amount ACC and the vehicle speed V.
Next, in step S3, the control unit 20 calculates a drive torque command _TTCS of the electric motor for suppressing acceleration slip of the drive wheels as a TCS control amount.

First, the control unit 20 calculates the slip ratio λ of the drive wheels 2RL and 2RR from the wheel speeds Vw _RL and Vw _{RR of} the drive wheels 2RL and 2RR detected by the wheel speed sensor 15 and the vehicle body speed V.
Next, it is determined whether or not the slip ratio λ exceeds a preset slip ratio threshold λ _TH . If the slip ratio λ exceeds the slip ratio threshold λ _TH , the slip ratio λ of the drive wheels 2RL and 2RR is A drive torque command T _TCS for controlling the output torque of the electric motors 3RL and 3RL is calculated so as to be equal to or less than the slip ratio threshold λ _TH . For example, the drive torque command T _TCS is calculated by multiplying a value obtained by subtracting the slip ratio threshold λ _TH from the slip ratio λ by a constant K.

On the other hand, if the slip ratio λ does not exceed the slip ratio threshold λ _TH , it is determined that it is not necessary to perform TCS control, and the drive torque command T _{TCS is set} to “0”.
Next, in step S4, the control unit 20 determines whether TCS control is executed based on the result of step S3. If T _TCS = 0 and TCS control is not executed, the driving force control is performed as it is. The process ends. On the other hand, when the TCS control is executed, the processes after step S5 are executed.

  In step S5, the control unit 20 calculates a target driving force difference between the left and right driving wheels so that a yaw moment intended by the driver is generated according to the driving operation by the driver. In this embodiment, the target driving force difference is calculated based on the steering angle δ detected by the steering angle sensor 11, and when it is detected that the steering position steered by the driver is in the neutral position. The driver determines that he is going straight ahead and sets the target driving force difference to zero.

  Regardless of the steering angle δ of the steering wheel, the target driving force difference can always be set to 0 in order to eliminate the influence on the yaw moment by the TCS control. Further, since the lateral force generated by the tire is reduced on the low μ road compared to the high μ road, the yaw rate similar to that on the high μ road is also obtained on the low μ road based on the steering angle δ and the yaw rate φ of the vehicle. It is also possible to set the target driving force difference so as to occur.

In step S6, the control unit 20 calculates a feedforward correction amount T _FF performs Ford-forward control based on the driving wheel 2RL, driving force Td future would be transmitted to the road from 2RR, the A process of adding the feedforward correction amount _TFF to the drive torque command (T _ACC −T _TCS ) is performed.
Here, based on the TCS control amount T _TCS calculated in step S3, the driving force transmitted from the driving wheels to the road surface when the TCS control is activated and the output torque of the electric motor is controlled is estimated in advance. Then, based on the estimated driving force, the feedforward correction amount _TFF is calculated as a driving torque command for setting the driving force difference between the left and right driving wheels to the target driving force difference calculated in step S5. A specific method for calculating the feedforward correction amount _TFF will be described later.

Next, in step S7, the control unit 20 performs Ford back control based on the current driving force Td transmitted from the driving wheels 2RL and 2RR to the road surface to calculate the feedback correction amount T _FB , and in step S6. the drive torque command obtained by adding the feedforward correction amount T _FF, by adding the feedback correction amount T _FB, performs processing for calculating a final command drive torque.

Here, the driving force difference between the left and right driving wheels is calculated based on the driving force Td calculated in step S1, and the deviation between the driving force difference and the target driving force difference calculated in step S5 is previously determined. A feedback correction amount T _FB is calculated by multiplying the set feedback gain K_FB.
Next, in step S8, the control unit 20 outputs a drive signal for realizing the final drive torque command calculated in step S7 to the motor inverters 4RL and 4RR, and then ends the drive force control process.

Next, the feedforward control executed in step S6 will be described.
In the feedforward control, a driving force transmission characteristic (ΔTd / ΔFm) which is a change in driving force Td transmitted to the road surface with respect to a change in motor driving force Fm is obtained from past sampling data, and a slip ratio λ and a road surface friction coefficient μ are obtained. TCS control is activated using the road surface characteristics indicating the relationship between the slip ratio and the equilibrium characteristics indicating the state (equilibrium state) where the slip ratio λ and the road surface friction coefficient μ are balanced when the electric motor outputs the driving force Fm. the driving force Td that would be transmitted to the road from the driving wheels estimated in advance by, performs processing so as to calculate the feedforward correction amount T _FF based on the estimated driving force Td.

(Electric vehicle motion equation)
First, the equation of motion of the electric vehicle will be described.
FIG. 6 is a diagram illustrating the driving force transmitted from the driving wheel to the vehicle body. In FIG. 6, M is vehicle mass, M _w is (the sum of the left and right wheels) equivalent mass of the rotating system that transmits a driving force, V is the vehicle speed, V _w is the wheel speed, Fm is the output driving force of the driving source, Td Is the driving force transmitted from the tire to the road surface. Further, r is the radius of the rotating body, θ is the rotation angle of the rotating body, and N is the vertical drag of the driving wheel.
For an electric vehicle configured to drive the vehicle forward by independently driving the front wheel or the left and right wheels of the rear wheel with an electric motor, the relationship between the driving force transmitted from the driving wheel to the vehicle body and the movement of the vehicle body is
(1) Friction and transmission torque at the left and right drive wheels are equal (2) Under the assumption that the rolling resistance and air resistance are sufficiently small, the equation of motion is described as follows.

(Fm−Td) = M _w V _w ′ (2)
Td = MV ′ (3)
Here, the above equation (3) applies the second law of Newton's motion to the motion of the vehicle body. Here, 'is a symbol indicating first order differentiation, and V' is equivalent to dV / dt.

Next, the above equation (2) is verified. The equation of motion of the rotating body is expressed by the following equation.
Iθ ″ = T = Fr (4)
Here, I is the moment of inertia of the rotating body, T is the rotational torque, and F is the rotational force. Note that “is a symbol indicating second-order differentiation, and θ” is equivalent to d ² θ / dt ² . From the above equation (4), the force used to change the rotational speed of the driving force transmission system is as follows.
F = (I / r) θ ″
= (I / r) ω '
= (I / r ² ) rω ′ (5)
Here, ω is the rotational angular velocity of the tire, and since V _w = rω, the above equation (5) is as follows.

F = (I / r ² ) V _w ′ (6)
Further, since I = M _w · r ² , the above equation (6) is as follows.
F = M _w V _w ′ (7)
Since the force used to change the rotational speed of the driving force transmission system can be considered as the remainder obtained by subtracting the driving force transmitted from the rotating body to the road surface from the output of the driving source, F = (Fm−Td) Thus, the equation (2) is established.
(Explanation of road surface characteristics)
The relationship between the driving force Fd transmitted from the tire to the road surface and the road surface friction coefficient is expressed by the following equation.

Td = Nμ (λ) (8)
Here, λ is a slip ratio, and the slip ratio at the time of driving (V _w > V) is expressed by the following equation.
λ = (V _w −V) / V _w (9)
Further, μ (λ) is a road surface friction coefficient at a slip ratio λ, and has a characteristic according to the road surface state. FIG. 7 is a diagram showing the relationship (road surface characteristics) between the slip ratio λ and the road surface friction coefficient μ.
(Explanation of equilibrium characteristics)
Next, the relationship between the output driving force Fm of the driving source that brings the slip ratio λ into an equilibrium state at a certain value and the driving force Td transmitted from the tire to the road surface is obtained. From the equations (2) and (3), the following relationship is established.

(Fm-Td) / Td = M w V w '/ MV' ......... (10)
Thereby, the following expression is obtained.
(M _w / M) · (V _w ′ / V ′) = (Fm / Td) −1 (11)
It slip ratio λ is called equilibrium state, it means that the vehicle speed V, the slip rate λ is unchanged even if the wheel speed V _w is changed minutely, to obtain the following equation on the basis of the equation (9).

_{λ = (V w -V) /} V w = (V w + V w '-V-V') / (V w + V w ')
_{(V w -V) (V w} + V w ') = V w (V w + V w' -V-V ')
^{_{V w 2 + V w V w}} '-VV w -VV w' = V w 2 + V w V w '-VV w -V'V w
VV _w ′ = V′V _w (12)
Therefore, the following equation is obtained from the above equation (12).

_Vw '/ V' = _Vw / V = 1 / V / _Vw = 1 / {1- ( _Vw- V) / _Vw }
= 1 / (1-λ) ……… (13)
Substituting Equation (8) and Equation (13) into Equation (11) gives the following.
(M _w / M) {1 / (1-λ)} = Fm / Nμ (λ) −1
Fm / Nμ (λ) = {M _w + M (1−λ)} / M (1−λ)
μ (λ) = (Fm / N) [M (1-λ) / {M _w + M (1-λ)}]
= (Fm / N) [1- _Mw / { _Mw + M (1-λ)}]
= (Fm / N) [1- ( _Mw / M) / {( _Mw / M) + 1-λ}] (14)
Therefore, from the equation (14),
μ → Fm / N at λ → −∞,
λ = 0 and μ = (Fm / N) {M / (M _w + M}),
λ = 1 and μ = 0,
λ → M _w / M + 1 and μ → −∞
It becomes. FIG. 8 is a diagram showing the characteristics shown in the equation (14). Thus, the equilibrium characteristic is a hyperbola.

FIG. 9 is a diagram showing the relationship between the road surface characteristics shown in FIG. 7 and the equilibrium characteristics shown in FIG. The solid line in FIG. 9 is the road surface characteristic, and the broken line is the balance characteristic (vehicle characteristic). FIG. 9 is an enlarged view of the balance characteristic shown in FIG. 8 in the range of 0 ≦ λ ≦ 1, and overlapped with the road surface characteristic shown in FIG. It is a thing.
Since the intersections A to C of these two curves are the points that satisfy both the vehicle and the road surface, the traveling state of the vehicle is one of these intersections A to C.

FIG. 10 is a diagram for explaining a specific method for calculating the feedforward correction amount _TFF .
In FIG. 10, a curve indicated by a solid line is a road surface characteristic line, and curves (a) to (d) indicated by a broken line are equilibrium characteristic lines. As is clear from the equation (14), the equilibrium characteristic line gradually changes from (A) to (D) as the driving force Fm decreases.
When the equilibrium characteristic line changes from (a) to (c) with the change of the output driving force Fm of the electric motor, the output driving force Fm = KI of the electric motor and the driving force Td = Nμ transmitted from the driving wheel to the road surface. Based on the above, it is observed that the equilibrium point has changed from point D to point E. In this case, the change rate ΔTd / ΔKI of the minute section, so-called driving force transmission characteristics can be obtained. The driving force transmission characteristic is indicated by a straight line α in FIG. 10, and it can be estimated that the equilibrium point shifts on the driving force transmission characteristic as the output driving force Fm of the electric motor changes.

Therefore, when the output torque of the electric motor is controlled by the TCS control and the output driving force Fm of the next electric motor is known, the balance characteristic line corresponding to the driving force Fm and the driving force transmission are determined. It can be seen that the intersection with the characteristic line α becomes the next equilibrium point.
That is, when it is found that the equilibrium characteristic line corresponding to the output driving force Fm of the next electric motor becomes (D), it can be estimated that the intersection F between the broken line (D) and the straight line α becomes the next equilibrium point. Then, the driving force Td transmitted to the next road surface can be estimated from the road surface friction coefficient μ at the point F.

That is, in this feedforward control, the change in the output driving force Fm (= KI) of the electric motors 3RL and 3RR in the past predetermined reference period and the driving force transmitted from the driving wheels 2RL and 2RR to the road surface in the reference period. Based on the driving force transmission characteristic ΔTd / ΔKI determined from the change in Td and the output driving force Fm of the electric motors 3RL, 3RR when the TCS control is activated according to the TCS control amount T _TCS , the driving wheels 2RL, The future driving force Td transmitted from 2RR to the road surface is estimated. Then, the driving force difference between the left and right driving wheels is calculated from the driving force Td estimated in advance as described above, and the feedforward correction amount _TFF is calculated as a driving torque command so that the driving force difference becomes the target driving force difference. To do.

(Operation)
Next, the operation of the first embodiment of the present invention will be described.
Now, from a state where the vehicle 1 is stopped on the frozen road surface, the depression of the accelerator pedal as the driver attempts to start the vehicle, the slip ratio of the same size greater than the slip rate threshold lambda _TH to the drive wheels 2RL and 2RR lambda Is assumed to occur. In this case, the control unit 20 calculates the driver command torque T _ACC based on the accelerator pedal operation amount ACC in Step 2 of FIG. Further, since the drive wheels 2RL, the slip ratio lambda of 2RR exceeding the slip ratio threshold lambda _TH, in step S3, the control unit 20, the drive wheels 2RL, slip ratio of 2RR lambda is equal to or less than the slip rate threshold lambda _TH Thus, the drive torque command T _TCS for controlling the output torque of the electric motors 3RL, 3RL is calculated.

At this time, assuming that the steering angle δ = 0 and the steering is maintained at the neutral position (straight forward position), the control unit 20 sets the target driving force difference to “0” in step S5.
By the way, when the road surface friction coefficient of the left driving wheel 2RL and the road surface friction coefficient of the right driving wheel 2RR are equal, when the same driving force is applied to the electric motors of the left and right driving wheels, the transmission is transmitted to the road surface of the driving wheels. There is no difference between the left and right driving wheels (driving force difference = 0).

Drive wheels 2RL, TCS control on the basis of the drive torque command T _TCS in order to suppress the acceleration slip of 2RR are operated, the electric motor 3RL, when the output torque of the 3RR is both reduction control, the electric motor of the left and right drive wheels Since the same amount of driving force is applied, the driving force difference between the left and right driving wheels is “0”, which matches the target driving force difference. Therefore, there is no need to perform the driving force difference control for adjusting the driving force difference between the left and right driving wheels, and the control unit 20 calculates the feedforward correction amount _TFF as “0” in step S6.

Further, when the current driving force difference between the left and right driving wheels is also “0” and matches the target driving force difference, it is not necessary to perform driving force difference control for adjusting the driving force difference between the left and right driving wheels. In step S7, the control unit 20 calculates the feedback correction amount T _FB as “0”.
Thereby, in the control unit 20, only TCS control for suppressing the acceleration slip of the vehicle is executed, and a drive signal based on the drive torque command T _TCS is output to the motor inverters 4RL and 4RR, and electric Both the output torques of the motors 3RL and 3RR are controlled to decrease. As a result, it is possible to suppress slipping of the drive wheels 2RL and 2RR. At this time, the vehicle behavior does not become unstable, and the vehicle starts in the straight direction in accordance with the steering by the driver.

  FIG. 11 is a diagram for explaining the operation when only the TCS control for suppressing the acceleration slip of the vehicle is performed without performing the driving force difference control as in the present embodiment. The road surface conditions here are split μ roads with different road surface friction coefficients on the left and right sides in the vehicle width direction, a low μ road on the left side in the vehicle width direction and a high μ road on the right side in the vehicle width direction. As shown in FIG. 11A, from the state where the vehicle 201 is stopped with the left driving wheel 202RL on the low μ road and the right driving wheel 202RR on the high μ road, the driver moves the steering to the neutral position. Assume that the accelerator pedal is depressed while maintaining (straight forward).

At this time, the left driving wheel 202RL slips and the TCS control is activated, so that the output driving force of the driving wheel 202RL on the low μ road side is weakened. On the high μ road side, a large driving force is transmitted from the wheel to the road surface, whereas on the low μ road side, the driving force transmitted from the wheel to the road surface is small. Therefore, there is a large difference in the driving force transmitted from the wheel to the road surface between the left and right driving wheels.
The movement of the vehicle is based on a force applied to the vehicle by a reaction force from the road surface. If there is a difference in the driving force transmitted from the wheels to the road surface between the left and right drive wheels as described above, the road reaction force on the low μ road side becomes smaller than the road reaction force on the high μ road side, so the yaw moment is generated in the vehicle. appear. Therefore, even when the steering is maintained at the straight traveling position, the vehicle 201 turns to the low μ road side and the vehicle behavior becomes unstable as shown in FIG. 11B.

On the other hand, in this embodiment, by controlling the output torque of the electric motor so that the driving force difference between the left and right driving wheels becomes the target driving force difference, the vehicle behavior is prevented from becoming unstable during the TCS control intervention. To do.
That is, from the state where the vehicle 1 is stopped on the split μ road as in FIG. 11, the driver depresses the accelerator pedal to start the vehicle, the left driving wheel 2RL of the vehicle 1 slips, and the driving wheel 2RL _Assume that a slip ratio λ exceeding the slip ratio threshold λ _TH occurs. In this case, the control unit 20 calculates the driver command torque T _ACC based on the accelerator pedal operation amount ACC in Step 2 of FIG. Since the slip ratio lambda of the drive wheels 2RL exceeding the slip ratio threshold lambda _TH, in step S3, the control unit 20, the slip ratio of the driving wheels 2RL lambda is of the electric motor 3RL to be equal to or less than the slip rate threshold lambda _TH A drive torque command T _TCS for controlling the output torque is calculated.

At this time, since the steering angle δ = 0 and the steering wheel is maintained at the neutral position, the control unit 20 sets the target driving force difference to “0” in step S5.
By the way, the road surface friction coefficient of the left driving wheel 2RL is different from the road surface friction coefficient of the right driving wheel 2RR. When the same driving force is applied to the electric motors of the left and right driving wheels, the left and right driving wheels A difference occurs in the driving force transmitted from the wheel to the road surface.

When the TCS control is activated, while maintaining the output torque of the electric motor 3RR only the output torque of the electric motor 3RL is reduced controlled based on the drive torque command T _TCS in order to suppress the acceleration slip of the driving wheels 2RL .
As the output torque of the electric motor 3RL is reduced by the TCS control, the driving force Td transmitted from the left driving wheel 2RL to the road surface also changes, but the difference in driving force transmitted from the wheel to the road surface by the left and right driving wheels is reduced. There is no. Accordingly, since it is necessary to perform the driving force difference control for adjusting the driving force difference between the left and right driving wheels, the control unit 20 determines the driving force transmission characteristic ΔTd / ΔKI and the next output driving force Fm of the electric motor 3RL in step S6. Is used to estimate the next driving force Td of the left driving wheel 2RL, and based on the estimated driving force Td, a feedforward correction amount _TFF for calculating the left / right driving force difference is calculated.

Further, since there is a difference in the driving force between the current left and right driving wheels and it does not coincide with the target driving force difference, the control unit 20 determines based on the deviation between the current left and right driving force difference and the target driving force difference in step S7. Thus, a feedback correction amount T _FB for making the current left / right driving force difference coincide with the target driving force difference is calculated.
As a result, the control unit 20 executes TCS control for suppressing the acceleration slip of the vehicle and driving force difference control for setting the left / right driving force difference to 0, and the drive torque command T _TCS is set. drive signal based on the drive torque command corrected by the feedforward correction amount T _FF and the feedback correction amount T _FB is output motor inverter 4RL, to 4RR. As a result, the output torque of the electric motor 3RL is controlled to decrease in order to suppress the acceleration slip of the left drive wheel 2RL, and the output torque of the electric motor 3RR is controlled to decrease to set the left / right driving force difference to zero.

FIG. 12 is a diagram for explaining the effect of this embodiment.
In the case where only TCS control is performed as shown in FIG. 11, when the vehicle starts and accelerates on a split μ road and slip occurs on any of the left and right drive wheels, the TCS control is activated and the slip ratio λ of the slip wheel is Only the output torque on the slip wheel side is controlled to decrease so that becomes less than the slip ratio threshold λ _TH . Therefore, for example, when the slip ratio λ of the left and right drive wheels is both 0.1, which is equal to or less than the slip ratio threshold λ _TH , the running state of the vehicle is a point A state on the low μ road side and a point B state on the high μ road side. It becomes. At this time, there is a large difference in the driving force transmitted from the wheels to the road surface between the left and right driving wheels, and the vehicle turns to the low μ road side even when the steering is maintained at the straight traveling position.

As described above, the traveling state of the vehicle is in the state of point A on the low μ road side and in the state of point B on the high μ road side, so that a driving force difference of about 2.4 times in friction coefficient ratio occurs.
On the other hand, in this embodiment, when the vehicle starts and accelerates on the split μ road and a slip occurs in any of the left and right drive wheels, the TCS control is activated and the slip ratio λ of the slip wheel is equal to or less than the slip ratio threshold λ _TH. The output torque on the slip wheel side is reduced and controlled so that the difference between the left and right driving forces is zero. Therefore, when the slip of the left and right drive wheels is suppressed, the running state of the vehicle is in the state of point A on the low μ road side and in the state of point C on the high μ road side. At this time, since the driving force transmitted from the wheels to the road surface is equal between the left and right driving wheels, when the steering is maintained at the straight traveling position, the vehicle starts moving in the straight traveling direction without becoming unstable.

As described above, in this embodiment, the output torque of the driving wheel on the high μ road side is controlled to be in the state of point A on the low μ road side and in the state of point C on the high μ road side. The difference can be eliminated and the occurrence of a yaw moment unintended by the driver can be suppressed.
In the present embodiment, the accelerator pedal sensor 12 constitutes a driving operation amount detection means, and the motor inverters 4RL, 4RR constitute a motor operation detection means. Further, step S1 in FIG. 4 constitutes a driving force calculating means, step S3 constitutes a slip ratio calculating means and a driving force control means, the process of step S6 constitutes a second correction amount calculating means, and step S7 of FIG. The process constitutes a first correction amount calculation means, and the processes in steps S6 and S7 constitute a control amount correction means.

(Effects of the first embodiment)
(1) The TCS control amount is corrected so that the difference in driving force transmitted from the left and right driving wheels to the road surface becomes the target driving force difference. Therefore, when the driving force of one of the left and right driving wheels becomes smaller than the driver command value by the TCS control, the driving force of the other driving wheel is controlled so that the driving force difference follows the target driving force difference. The As a result, for example, in the start acceleration on the split μ road, when the driving force of the driving wheel on the low μ road side is reduced by TCS control, the driving force transmitted from the driving wheel on the low μ road side to the road surface is high. It is possible to suppress the occurrence of a yaw moment unintended by the driver, such as the vehicle turning to the low μ road side due to being smaller than the μ road side.

(2) The driving force difference control in which the driving force difference transmitted from the left and right driving wheels to the road surface becomes the target driving force difference is performed by using both feedback control and feedforward control. Therefore, the driving force difference between the left and right driving wheels can be made to follow the target driving force difference more appropriately.
In addition, from the driving wheel using the driving force transmission characteristics obtained from the change in the output driving force of the electric motor in the past predetermined reference period and the change in the driving force transmitted from the driving wheel to the road surface in the reference period. Estimate the future driving force transmitted to the road surface. Therefore, it is possible to accurately estimate the future driving force by taking advantage of the property of accurately modeling the output characteristics of the electric motor.

  (3) At the time of TCS control intervention, the difference in driving force transmitted from the left and right driving wheels to the road surface is made to follow the target driving force difference for generating the yaw moment intended by the driver. Therefore, even if the driving force of one of the left and right driving wheels becomes smaller than the driver command value by TCS control, the yaw moment unintended by the driver is generated by controlling the driving force of the other driving wheel. Can be suppressed, and the vehicle behavior can be stabilized.

  (4) When the driving force of one of the left and right driving wheels becomes smaller than the driver command value by the TCS control, the difference in driving force transmitted from the left and right driving wheels to the road surface follows the target driving force difference. The driving force of the other driving wheel is controlled. Therefore, generation of a yaw moment not intended by the driver can be suppressed, and an automobile capable of stabilizing the vehicle behavior can be obtained.

  (5) When the driving force of one of the left and right driving wheels becomes smaller than the driver command value by the TCS control, the difference in the driving force transmitted from the left and right driving wheels to the road surface follows the target driving force difference. By controlling the driving force of the other drive wheel, it is possible to suppress the yaw moment that is not intended by the driver, and to stabilize the vehicle behavior.

(Second Embodiment)
Next, a second embodiment of the present invention will be described.
(Constitution)
In the second embodiment, the sampling time for calculating the driving force transmission characteristic of the road surface is changed according to the TCS control amount, in other words, the change of the driving force transmitted from the driving wheel to the road surface with respect to the change amount of the output driving force of the electric motor. It is changed according to the amount.

  FIG. 13 is a flowchart showing a driving force control processing procedure executed by the control unit 20 in the second embodiment. In the driving force control process of this embodiment, step S21 for setting a sampling time for calculating the driving force transmission characteristic of the road surface is added after step S8 in the driving force control process of the first embodiment shown in FIG. Except for this, processing similar to the driving force control in the first embodiment shown in FIG. 4 is executed. Therefore, the same step number is assigned to the part that executes the same process as the driving force control in the first embodiment, and the different part of the process will be mainly described.

In step S21, a sampling time for calculating the road surface driving force transmission characteristic is set based on the driving force change ΔTd transmitted from the driving wheel to the road surface with respect to the output driving force change ΔKI of the electric motor.
FIG. 14 is a diagram for explaining a sampling time setting method for calculating driving force transmission characteristics.

  The change ΔTd in the driving force transmitted from the driving wheel to the road surface with respect to the change ΔKI in the output driving force of the electric motor in the predetermined period is different in each of the areas [1] to [3] in FIG. The value is a negative value having a small absolute value, and the value of ΔTd / ΔKI in the region [2] is a negative value having a large absolute value compared to the value of ΔTd / ΔKI in the region [1]. The value of ΔTd / ΔKI in [3] is a positive value having a large absolute value.

  When the traveling state of the vehicle is in the state [1], the absolute value of ΔTd / ΔKI is small, so that even if the ΔKI section for calculating the driving force transmission characteristic ΔTd / ΔKI is long, the accuracy is sufficiently high. The driving force transmission characteristic ΔTd / ΔKI can be calculated. Therefore, when the change ΔTd in the driving force transmitted from the driving wheel to the road surface with respect to the change ΔKI in the output driving force of the electric motor is small, the sampling time T for calculating the driving force transmission characteristic is set to T = T1.

On the other hand, when the change ΔTd in the driving force transmitted from the driving wheel to the road surface with respect to the change ΔKI in the output driving force of the electric motor is large, the ΔKI interval is shortened so that the driving force transfer characteristic ΔTd / ΔKI is sequentially updated. . Therefore, in this case, the sampling time T for calculating the driving force transmission characteristic is set to T = T2 (<T1).
In addition, although the case where the sampling time T is changed stepwise according to which region in FIG. 14 is in the traveling state of the vehicle has been described, from the driving wheel to the road surface with respect to the change ΔKI in the output driving force of the electric motor. The sampling time T can be changed continuously according to the magnitude of the transmitted driving force change ΔTd.

  Thus, in step S21, after changing the sampling time T in accordance with the change ΔTd in the driving force transmitted from the driving wheel to the road surface with respect to the change ΔKI in the output driving force of the electric motor, the driving force control process ends.

(Operation)
Next, the operation of the second embodiment of the present invention will be described.
From the state where the vehicle 1 is stopped on the split μ road, the driver depresses the accelerator pedal to start the vehicle, the left driving wheel 2RL of the vehicle 1 slips, and the slip ratio threshold λ _TH is set to the driving wheel 2RL. It is assumed that a slip ratio λ that exceeds is generated. In this case, the control unit 20 calculates the driver command torque T _ACC based on the accelerator pedal operation amount ACC in Step 2 of FIG. Since the slip ratio lambda of the drive wheels 2RL exceeding the slip ratio threshold lambda _TH, in step S3, the control unit 20, the slip ratio of the driving wheels 2RL lambda is of the electric motor 3RL to be equal to or less than the slip rate threshold lambda _TH A drive torque command T _TCS for controlling the output torque is calculated.

Further, in step S6, the control unit 20 estimates the next driving force Td of the left driving wheel 2RL based on the driving force transmission characteristic ΔTd / ΔKI and the next output driving force Fm of the electric motor 3RL, and the estimated driving force. Based on Td, a feedforward correction amount _TFF is calculated for setting the left / right driving force difference to zero.
Further, in step S7, the control unit 20 calculates a feedback correction amount T _FB for making the current left / right driving force difference coincide with the target driving force difference based on the deviation between the current left / right driving force difference and the target driving force difference. To do.

As a result, the control unit 20 executes TCS control for suppressing the acceleration slip of the vehicle and driving force difference control for setting the left / right driving force difference to 0, and the drive torque command T _TCS is set. drive signal based on the drive torque command corrected by the feedforward correction amount T _FF and the feedback correction amount T _FB is output motor inverter 4RL, to 4RR.

  Further, at this time, the slip ratio λ of the left drive wheel 2RL is large, the vehicle is in the state [1] in FIG. 14, and the drive transmitted from the drive wheel to the road surface with respect to the change ΔKI in the output drive force of the electric motor. If the force change ΔTd is small, the control unit 20 sets the sampling time T for calculating the driving force transmission characteristic at step S21 to a relatively long T = T1.

When the next driving force control processing flow is executed, the control unit 20 takes a long ΔKI section based on the sampling time T = T1 set in step S21 one sampling before in step S6, and the driving force transmission characteristics. ΔTd / ΔKI is calculated.
Thereafter, when the slip ratio λ of the left drive wheel 2RL is gradually suppressed and the vehicle traveling state shifts to the state in the region [2] in FIG. 14, the road surface from the drive wheel to the change ΔKI in the output driving force of the electric motor. Therefore, the control unit 20 sets the sampling time T for calculating the driving force transmission characteristic to a relatively short T = T2 in step S21.

As a result, when the next driving force control processing flow is executed, the control unit 20 shortens the ΔKI section based on the sampling time T = T2 set in step S21 one sampling before in step S6, and transmits the driving force. The characteristic ΔTd / ΔKI is calculated.
As described above, in the section where the change in the road surface friction coefficient μ with respect to the change ΔKI in the output driving force of the electric motor (change ΔTd in the driving force transmitted from the driving wheel to the road surface) is small, the sampling time T for calculating the driving force transmission characteristic is lengthened. Therefore, since a large estimation section of the driving force Td transmitted from the next driving wheel to the road surface is taken, a robust estimation can be made with respect to the estimation error.
In the above embodiment, the process of step S21 constitutes a reference period setting unit.

(Effect of 2nd Embodiment)
(1) The sampling time for calculating the driving force transmission characteristic of the road surface is changed according to the change amount of the driving force transmitted from the driving wheel to the road surface with respect to the change amount of the output driving force of the electric motor. Therefore, if the amount of change in the driving force transmitted from the driving wheel to the road surface relative to the amount of change in the output driving force of the electric motor is small, a longer sampling time is used for robust estimation of the future driving force transmitted from the driving wheel to the road surface. Can be estimated.

(Third embodiment)
Next, a third embodiment of the present invention will be described.
(Constitution)
In the third embodiment, the maximum control amount of TCS control is changed according to the driving force transmission characteristics.

  FIG. 15 is a flowchart showing a driving force control processing procedure executed by the control unit 20 in the third embodiment. In the driving force control process of this embodiment, except that the step S31 for setting the maximum control amount of TCS control is added after step S8 in the driving force control process of the first embodiment shown in FIG. Performs the same processing as the driving force control in the first embodiment shown in FIG. Therefore, the same step number is assigned to the part that executes the same process as the driving force control in the first embodiment, and the different part of the process will be mainly described.

In step S31, the maximum control amount corresponding to the upper limit of the TCS control amount is set according to the driving force transmission characteristic ΔTd / ΔKI calculated in step S6, and then the driving force control process is terminated.
In FIG. 14, region [3] is the range of the target slip ratio in the TCS control (region of slip ratio threshold λ _TH or less), and the value of driving force transfer characteristic ΔTd / KI in region [3] is a positive predetermined value. TH or higher.

When ΔTd / KI ≧ TH and the driving force transmission characteristic ΔTd / KI is in the region [3], the maximum value of the TCS control is set to a small value, and the driving force transmission characteristic ΔTd / KI is in the region [3]. If it is outside, the maximum value of the TCS control amount is set to a large value.
In step S3, an upper limit is set for the TCS control amount T _TCS according to the maximum control amount set in step S31.

(Operation)
Next, the operation of the third embodiment of the present invention will be described.
When the vehicle 1 is stopped on an icy road, the driver depresses the accelerator pedal to start the vehicle, and a slip ratio λ exceeding the slip ratio threshold λ _TH is generated in the drive wheels 2RL and 2RR of the vehicle 1 And In this case, the control unit 20 calculates the driver command torque T _ACC based on the accelerator pedal operation amount ACC in Step 2 of FIG. Drive wheels 2RL, because the slip ratio lambda of 2RR exceeding the slip ratio threshold lambda _TH, in step S3, the control unit 20, the drive wheels 2RL, so that the slip ratio of 2RR lambda is equal to or less than the slip rate threshold lambda _TH A drive torque command T _TCS for controlling the output torque of the electric motors 3RL and 3RR is calculated.

Since the road surface friction coefficient of the left driving wheel 2RL and the road surface friction coefficient of the right driving wheel 2RR are equal and the driving force transmitted from the wheel to the road surface is not different between the left and right driving wheels, the control unit 20 feeds in step S6. The forward correction amount _{TFF is set} to 0, and the feedback correction amount _{TFB is set} to 0 in step S7.
Thereby, in the control unit 20, only TCS control for suppressing the acceleration slip of the vehicle is executed, and a drive signal based on the drive torque command T _TCS is output to the motor inverters 4RL and 4RR.

At this time, the slip ratio λ of the driving wheels 2RL and 2RR is large, the driving force transmission characteristic ΔTd / ΔKI calculated in step S6 is not equal to or greater than the positive predetermined value TH, and the running state of the vehicle is in the region of FIG. [3] If it is assumed that the state is outside, the control unit 20 sets the maximum control amount of the TCS control to a relatively large value in step S31.
When the next driving force control processing flow is executed, the control unit 20 provides a large upper limit of the TCS control amount T _TCS in step S3 based on the maximum control amount set in step S31 before one sampling.

After that, when the slip ratio λ of the drive wheels 2RL and 2RR is gradually suppressed and the vehicle traveling state shifts to the state in the region [3] in FIG. 14, ΔTd / ΔKI ≦ TH, so the control unit 20 In step S31, the maximum value of the TCS control amount is set small.
Thereby, at the time of execution of the next driving force control processing flow, the control unit 20 sets a small upper limit of the TCS control amount T _TCS in step S3 based on the maximum control amount set in step S31 before one sampling.

As described above, when the state is outside the region [3], the TCS control can be operated largely by setting the maximum value of the TCS control amount to a large value, so that the acceleration slip of the slip ring can be quickly suppressed. Thus, it is possible to quickly converge within the region [3] that is the range of the target slip ratio. At the same time, the above processing makes it possible to finely observe the value of the output driving force KI of the electric motor and the driving force Td transmitted from the driving wheel to the road surface in the section of region [3]. It becomes easy to maintain the linearity in the portion where ΔTd / KI greatly changes.
In the above embodiment, the process in step S31 constitutes a maximum control amount setting means.

(Effect of the third embodiment)
(1) The maximum control amount of the TCS control amount is changed according to the change amount of the driving force transmitted from the driving wheel to the road surface with respect to the change amount of the output driving force of the electric motor. Therefore, if it is determined that the slip ratio of the slip wheel is not within the range of the target slip ratio based on the change amount of the drive force transmitted from the drive wheel to the road surface with respect to the change amount of the output drive force of the electric motor, the maximum By setting the control amount large and operating the TCS control greatly, it is possible to quickly suppress the acceleration slip of the slip wheel and to quickly converge the target slip ratio within the range.
In addition, it becomes easy to maintain the linearity of the minute section, and the TCS control amount becomes dense near the optimum driving force, so that more appropriate driving force control can be performed.

(Application examples)
In each of the above embodiments, a case where a so-called in-wheel motor designed integrally with a wheel is installed on a driving wheel independently has been described. However, the driving force of each driving wheel is independently applied without applying the in-wheel motor. Controllable motors can also be installed respectively. Also in this case, since the driving force applied to the left and right sides of the vehicle body can be controlled independently, the present invention can be applied.

  Further, in each of the above embodiments, the case where the present invention is applied to a rear wheel drive vehicle having the rear two wheels as drive wheels has been described, but the present invention can also be applied to a front wheel drive vehicle and a four wheel drive vehicle.

It is a block diagram which shows the function structure of the driving force control apparatus of the electric vehicle which concerns on this invention. 1 is a schematic configuration diagram of a vehicle in an embodiment of the present invention. It is a control block diagram which shows the detail of a driving force difference control. It is a flowchart which shows the driving force control process in 1st Embodiment. It is a control block diagram explaining the calculation concept of the driving force transmitted from a wheel to a road surface. It is a figure explaining the driving force transmitted to a vehicle body from a driving wheel. It is a figure which shows a road surface characteristic. It is a figure which shows an equilibrium characteristic. It is a figure which shows the relationship between a road surface characteristic and an equilibrium characteristic. It is a figure explaining the specific calculation method of feedforward correction amount. It is a figure explaining the subject of this invention. It is a figure explaining the effect of this embodiment. It is a flowchart which shows the driving force control process in 2nd Embodiment. It is a figure for demonstrating the setting method of the sampling time which calculates a driving force transmission characteristic. It is a flowchart which shows the driving force control process in 3rd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vehicle 2RL, 2RR Drive wheel 3RL, 3RR Electric motor 4RL, 4RR Motor inverter 10 Steering wheel 11 Steering angle sensor 12 Accelerator pedal sensor 13 Brake pedal sensor 14 Vehicle behavior sensor 20 Control unit 21 Power supply unit

Claims (5)

  Left and right electric motors for independently driving the left and right drive wheels, operation amount detection means for detecting the amount of driving operation by the driver, slip ratio calculation means for calculating the slip ratio of the drive wheels, and slip of the drive wheels In a driving force control device for an electric vehicle comprising driving force control means for controlling the output driving force of each electric motor according to the detection result of the operation amount detection means so that the rate falls within a predetermined range,
  Based on the motor operation detection means for detecting the operation state of the electric motor and the operation state of the electric motor detected by the motor operation detection means, the driving force transmitted from the left and right drive wheels to the road surface is calculated. The control amount of the driving force control by the driving force control unit is corrected so that the difference between the driving force of the driving force calculation unit and the driving force of the left and right driving wheels calculated by the driving force calculation unit becomes a predetermined target driving force difference. Control amount correction means,
  The control amount correction means performs a feedback control based on the current driving force transmitted from the driving wheel to the road surface, and calculates a first correction amount for correcting the control amount of the driving force control. Calculation means and second correction amount calculation means for calculating a second correction amount for correcting the control amount of the driving force control by performing feedforward control based on a future driving force transmitted from the driving wheel to the road surface The second correction amount calculating means includes a change in the output driving force of the electric motor in a predetermined past reference period, and a change in the driving force transmitted from the driving wheel to the road surface in the reference period. The driving force control device for an electric vehicle is characterized in that a future driving force transmitted from the driving wheel to the road surface is estimated based on a driving force transmission characteristic obtained from the following and a control amount of the next driving force control. .   The reference period setting means for setting the reference period according to a change amount of the driving force transmitted from the driving wheel to the road surface with respect to a change amount of the output driving force of the electric motor. The drive force control apparatus of the described electric vehicle.   3. The electric vehicle according to claim 1, further comprising: a maximum control amount setting unit that sets a maximum control amount corresponding to an upper limit of the control amount of the driving force control according to the driving force transmission characteristic. Driving force control device.   A driving force control device for an electric vehicle having driving force control means for controlling an electric motor that is a driving source of the driving wheel so that a slip ratio of the driving wheel of the vehicle generated by the driver's accelerator operation is within a predetermined range. A car equipped with
  Based on the motor operation detection means for detecting the operation state of the electric motor and the operation state of the electric motor detected by the motor operation detection means, the driving force transmitted from the left and right drive wheels to the road surface is calculated. The control amount of the driving force control by the driving force control unit is corrected so that the difference between the driving force of the driving force calculation unit and the driving force of the left and right driving wheels calculated by the driving force calculation unit becomes a predetermined target driving force difference. Control amount correction means,
  The control amount correction means performs a feedback control based on the current driving force transmitted from the driving wheel to the road surface, and calculates a first correction amount for correcting the control amount of the driving force control. Calculation means and second correction amount calculation means for calculating a second correction amount for correcting the control amount of the driving force control by performing feedforward control based on a future driving force transmitted from the driving wheel to the road surface The second correction amount calculating means includes a change in the output driving force of the electric motor in a predetermined past reference period, and a change in the driving force transmitted from the driving wheel to the road surface in the reference period. A future driving force transmitted from the driving wheel to a road surface is estimated based on a driving force transmission characteristic obtained from the following and a control amount of the next driving force control.   A drive force control method for an electric vehicle that performs drive force control for controlling an electric motor that is a drive source of the drive wheels so that a slip ratio of the left and right drive wheels is within a predetermined range,
  The driving force transmitted from the left and right driving wheels to the road surface is calculated based on the operating state of the electric motor, and the driving force is set so that the difference between the driving forces of the left and right driving wheels becomes a predetermined target driving force difference. When correcting the control amount of force control,
  Feedback control is performed based on the current driving force transmitted from the driving wheel to the road surface, a first correction amount for correcting the control amount of the driving force control is calculated, and the electric motor in a past predetermined reference period Based on a driving force transmission characteristic obtained from a change in the output driving force of the driving force, a change in driving force transmitted from the driving wheel to the road surface during the reference period, and a control amount of the next driving force control. A second driving force that estimates the future driving force transmitted from the wheel to the road surface, performs feedforward control based on the future driving force transmitted from the driving wheel to the road surface, and corrects the control amount of the driving force control. A driving force control method for an electric vehicle characterized by calculating a correction amount.

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