JP2005020830A - Yawing behavior of vehicle control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To rapidly correct a yaw rate change generated when one wheel slips on the low frictional road surface during straight running of an electric automobile adopting a four-wheel independent drive type, thereby the not intended yaw rate change arises on a vehicle body, by increasing a drive force of other wheels while avoiding a low frictional road surface. <P>SOLUTION: In the yawing behavior control device of the vehicle, a motor drive force controller 2 detects a slip detection starting time t1 and a slip detection ending time t2 based on the increase of a wheel speed Vw1; and estimates a road surface frictional coefficient μ of the low frictional road surface and an amount of a yaw rate change Δα of a vehicle body 8, when one front wheel W1 of four wheels slips on the low frictional road surface during passing, so that a drive force F2 cannot be transmitted to the road surface with the result that the front right wheel W1 races to increase the wheel speed Vw1. The motor drive force controller 2 estimates from a time t2 to a time t4 when a rear right wheel W4 at the same side with respect to a vehicle widthwise direction with the front right wheel W1 passes the low frictional road surface. The motor drive force controller 2 abolishes the amount of a yaw rate change estimation Δα by increasing the drive force command value F4 of the rear wheel W4 by avoiding from the time t2 to the time t4. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a yaw behavior control device for a vehicle that includes a plurality of drive wheels on the left and right sides, and that can independently control the drive force of all the drive wheels. The present invention relates to an improvement proposal of a yawing behavior control device that eliminates the yaw rate change by controlling the driving force distribution between the driving wheels.
[0002]
[Prior art]
Conventionally, a vehicle having four wheels and controlling the driving force of each of the four wheels independently is disclosed in, for example, Patent Document 1.
[0003]
[Patent Document 1]
Japanese Utility Model Publication No. 59-141405 [0004]
The electric vehicle described in Patent Document 1 includes a total of four or more wheels paired on the left and right of the vehicle body, a motor that is drivingly coupled to each of the wheels, and a control device that controls the motor. The apparatus controls the driving force of each wheel individually based on the operation of the driver and the rotational speed of each wheel.
[0005]
[Problems to be solved by the invention]
However, in the conventional drive motor control device, the driving force of the four wheels is controlled independently based on the rotational speed of the four wheels, and the wheel speed is determined based on the history of the rotational speed. Since the fluctuation cannot be obtained and the driving force cannot be controlled based on this, the following problem arises.
In other words, when one of the four wheels passes through a slippery, low-friction road surface portion such as a puddle or manhole, the possible driving force determined by the road surface friction coefficient is reduced, and the required driving force is reduced to the road surface. The driving force transmitted to the road surface by the slipping wheel is less than that of the other three wheels.
This difference in transmission driving force, particularly the difference in transmission driving force generated between the left and right driving wheels, causes an unintended yaw rate change in the vehicle body, resulting in a mismatch between the traveling direction and the vehicle body direction, thereby impairing running stability.
In particular, this problem occurs remarkably when a large driving force is required such as during acceleration traveling.
[0006]
In this case, for example, when the right front wheel becomes slipped and the yaw rate changes, if the drive power of the right front wheel is increased by utilizing the freedom of independent four-wheel drive, the rotational speed of the right front wheel further increases. The right front wheel slips further, the driving force transmitted to the road surface further decreases, the yaw rate change increases, and the running stability is further deteriorated.
[0007]
In view of such a problem, the present invention, when the yaw rate change due to the wheel slip as described above occurs, not only the wheel being slipped but also the wheel behind the running direction passes through the low friction road surface portion where the wheel is slippery. By eliminating the yaw rate change by controlling the driving force of each wheel during a period other than the period during which the vehicle is running, the yawing of the vehicle can solve the above-described problem that the running stability is further deteriorated due to the increase in the yaw rate change. A behavior control device is proposed.
[0008]
[Means for Solving the Problems]
For this purpose, the vehicle yawing behavior control device according to the present invention is based on a vehicle of the above type as described in claim 1,
When the drive wheel in the traveling direction slips while passing through the low friction road surface portion and the yaw rate changes, the driving wheel at the rear side in the traveling direction on the side where the slip occurs is other than the period in which the driving wheel passes through the low friction road surface portion. During the period, the driving force distribution between the driving wheels is determined so as to eliminate the yaw rate change.
[0009]
【The invention's effect】
According to the configuration of the present invention, the driving force distribution control between the driving wheels so as to eliminate the yaw rate change is performed in a period in which no driving wheel passes through the low friction road surface portion,
The drive force distribution control between the drive wheels is performed during the period when any of the drive wheels is passing through the low friction road surface portion, causing an increase in the yaw rate change, which causes the running stability to deteriorate. It is possible to solve the above-mentioned problem.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a diagrammatic plan view showing a wheel drive system of an electric vehicle including a yawing behavior control device according to an embodiment of the present invention, together with the drive force control device.
This electric vehicle has four wheels W1, W2, W3, and W4 on each side of the vehicle body, with a front wheel W1 and a rear wheel W4 on the right side, and a front wheel W2 and a rear wheel W3 on the left side. .
The right front wheel W1 and the right rear wheel W4, and the left front wheel W2 and the left rear wheel W3 are drive wheels that are individually driven by the individual motors M1 and M4, and the motors M2 and M3, and drive power is transmitted via these motors. Individual control is possible.
[0011]
A battery 1 is provided as a common power source for the motors M1, M2, M3, and M4, and the motors M1, M2, M3, and M4 are connected to the common battery 1 through inverters INV1, INV2, INV3, and INV4, respectively.
Inverters INV1, INV2, INV3 and INV4 receive driving force commands F1, F2, F3 and F4 from the motor driving force controller 2, respectively, and determine supply currents from the battery 1 to the corresponding motors M1, M2, M3 and M4. Thus, the driving force of the motors M1, M2, M3, and M4 (the driving force of the wheels W1, W2, W3, and W4) is made to coincide with the driving force commands F1, F2, F3, and F4.
[0012]
In order to determine the driving force commands F1, F2, F3, and F4, the motor driving force controller 2 receives signals relating to wheel speeds (rotational peripheral speeds) Vw1, Vw2, Vw3, and Vw4 of the wheels W1, W2, W3, and W4 ( Signals from the wheel speed sensors 3FR, 3FL, 3RL, 3RR for detecting the rotation speed signal) and signals from the accelerator opening sensor 4 for detecting the accelerator pedal depression amount (accelerator opening) APO. Enter.
[0013]
As shown by a block diagram in FIG. 2, the motor driving force controller 2 includes a reference driving force calculation unit 11, a driving force synthesis unit 12, a wheel speed calculation unit 13, a slip detection unit 14, and a road surface friction coefficient estimation unit. 15, a yaw rate change amount estimation unit 16, a rear wheel passage period estimation unit 17, a delay processing unit 18, a yaw rate correction driving force calculation unit 19, and a low friction road surface portion driving force decrease amount calculation unit 20. Based on the input information, driving force commands F1, F2, F3, and F4 to the inverters INV1, INV2, INV3, and INV4 are determined as follows.
[0014]
The reference driving force calculation part 11 calculates | requires the reference driving force F0 which the vehicle has requested | required based on accelerator opening APO.
The driving force synthesizing unit 12 distributes the reference driving force to each of the wheels W1, W2, W3, and W4 while considering the wheel load distribution and the like, and the reference driving force (hereinafter referred to as F0) of each of the wheels W1, W2, W3, and W4. / 4), and a yaw rate correction driving force command ΔF ′, which will be described later, is added to the reference driving force of each wheel as appropriate to determine the driving force commands F1, F2 of the wheels W1, W2, W3, and W4. , F3, F4, and these are supplied to the inverters INV1, INV2, INV3, INV4 to contribute to driving force control of the motors M1, M2, M3, M4.
[0015]
The wheel speed calculation unit 13 generates wheel speeds Vw1, Vw2, Vw3 of the wheels W1, W2, W3, W4 based on signals (rotational speed signals) from the wheel speed sensors 3FR, 3FL, 3RL, 3RR in FIG. Vw4 is calculated individually.
The slip detector 14 detects wheel slip based on the wheel speeds Vw1, Vw2, Vw3, and Vw4.
In the following, a case will be described in which the right front wheel W1 rides on the low friction road surface portion and causes an acceleration slip, whereby the vehicle is increased in the clockwise yaw rate as viewed from above.
In this case, since the wheel speed Vw1 of the right front wheel W1 becomes larger than the wheel speeds Vw2, Vw3, Vw4 of the other wheels as shown between the instants t1 and t2 in FIG. An acceleration slip of the right front wheel W1 can be detected, and a slip detection signal as shown in FIG. 3 can be output.
[0016]
When the wheel (right front wheel W1) slip detection signal is input, the road surface friction coefficient estimating unit 15 receives the actual acceleration that can be obtained from the wheel speed Vw1 of the relevant wheel and the driving force of the relevant wheel that is obtained by the driving force synthesizing unit 12. Estimate the friction coefficient μ of the low friction road surface portion on which the slipped wheel (right front wheel W1) rides by comparison (difference, etc.) with the maximum acceleration that should naturally be obtained under the command F1, as shown in FIG. Can do.
Instead of the above, the road surface friction coefficient estimating unit 15 can also estimate the road surface friction coefficient μ using a motion model representing the rotation of the corresponding wheel.
When the wheel (right front wheel W1) slip detection signal is input to the yaw rate change amount estimation unit 16, the yaw rate change amount Δφ of the vehicle generated by the slip of the corresponding wheel (right front wheel W1) from the road surface friction coefficient estimated value μ. Is estimated as shown in FIG.
[0017]
When the wheel (right front wheel W1) slip detection signal is not input, the rear wheel passage period estimation unit 17 slips at the instant t2 in FIG. 3 when the corresponding wheel has finished passing through the low friction road surface and the slip has converged. The convergence signal is output to the delay processing unit 18 and the instant t2 is used as a starting point until the rear wheel (right rear wheel) W4 on the same side as the slip generation wheel (right front wheel W1) reaches the low friction road surface portion. A time Δt1 and a time Δt2 required to pass through the low friction road surface portion are calculated from the wheel base and the corresponding wheel speed Vw4, and from these, the rear wheel (right rear wheel) W4 passes through the low friction road surface portion. As shown in FIG. 3, t5 is estimated and a rear wheel passage period estimation signal is output to the delay processing unit 18.
[0018]
The delay processing unit 18 receives the slip convergence signal from the rear wheel passage period estimation unit 17 and outputs a calculation start signal to the yaw rate correction driving force calculation unit 19.
The yaw rate correction driving force calculation unit 19 calculates the driving force distribution of the wheels W1, W2, W3, and W4 necessary for setting the yaw rate change estimated value Δφ to 0 and returning the yaw rate of the vehicle to the original value. Output as yaw rate correction driving force.
In determining the driving force distribution of the wheels W1, W2, W3, and W4 necessary for correcting the yaw rate, only the driving force command F4 for the right rear wheel W4 on the side where the wheel slip occurs (the vehicle right side) is operated. Is simple and advantageous.
In this case, as shown in FIGS. 2 and 3, the correction amount ΔF of the driving force command F4 necessary to eliminate the estimated yaw rate change value Δφ is output as the yaw rate correction driving force.
[0019]
The yaw rate correction driving force ΔF is obtained as follows.
The integral value P (t) = ∫ΔF (t) · dt of the yaw rate correction driving force ΔF (t) necessary to eliminate the yaw rate change estimated value Δφ is obtained, and the right rear wheel W4 passes through the low friction road surface portion. Assuming that the right rear wheel driving force control for yaw rate correction is performed equally before and after (before the moment t4 and after the instant t5 in FIG. 3), the yaw rate correction driving force ΔF is ΔF = P (t) / 2 / Δt1 can be calculated (Δt1 is the time until the right rear wheel reaches the low friction road surface portion as described above), and the yaw rate correction driving force ΔF can be obtained as shown in FIG.
[0020]
Based on the yaw rate correction driving force ΔF and the rear wheel passage period estimation signal from the rear wheel passage period estimation unit 17, the delay processing unit 18 performs before and after the right rear wheel W4 passes through the low friction road surface portion (FIG. 3). Yaw rate correction driving force ΔF is corrected from yaw rate correction driving force ΔF from instant t3 lagging from slip convergence instant t2 in FIG. 3 so that the right rear wheel driving force control for yaw rate correction is performed evenly before instant t4 and after instant t5. As shown in FIG. 3, the driving force command ΔF ′ starts to be output to the driving force combining unit 12 shown in FIG. 2, and the driving force command F4 for the right rear wheel W4 is increased by ΔF = ΔF ′ as shown in FIG.
[0021]
However, the delay processing unit 18 instead of outputting the yaw rate correction driving force ΔF as the yaw rate correction driving force command ΔF ′ during the instant t4 to t5 in FIG. 3 in which the right rear wheel W4 passes the low friction road surface portion. The yaw rate correction driving force command ΔF ′ is set to 0 as shown in FIG.
During this time, the delay processing unit 18 uses the low friction road surface portion driving force decrease amount calculation portion 20 as the following to obtain the low friction road surface portion driving force decrease amount ΔFd as the yaw rate correction driving force command ΔF ′ as shown in FIG. Output to the force synthesizer 12.
[0022]
The low-friction road surface portion driving force reduction amount calculation unit 20 receives the rear wheel passage period estimation signal and does not slip even during the instant t4 to t5 in FIG. 3 even if the right rear wheel W4 is on the low-friction road surface portion. As shown in FIG. 3, a low friction road surface portion driving force reduction amount ΔFd necessary for obtaining the right rear wheel driving force for achieving the above (preferably, the ideal slip ratio for obtaining the maximum driving force) is obtained.
Therefore, during the instant t4 to t5 of FIG. 3 in which the right rear wheel W4 passes through the low friction road surface portion, the driving force command F4 for the right rear wheel W4 is reduced by ΔF ′ = ΔFd as shown in FIG.
[0023]
After the instant t5 of FIG. 3 when the right rear wheel W4 has passed through the low friction road surface portion, the delay processing unit 18 again uses the yaw rate correction driving force ΔF as the yaw rate correction driving force command ΔF ′ as shown in FIG. The power is output to the force synthesizer 12 and the driving force command F4 for the right rear wheel W4 is raised again by ΔF = ΔF ′ as shown in FIG.
The raising is finished when the yaw rate correction driving force ΔF becomes 0 at the instant t6 in FIG. 3 when the above-described integrated value P (t) of the yaw rate correction driving force is achieved.
[0024]
According to the present embodiment, the yaw rate change Δφ associated with the slip of the wheel (right front wheel W1) during a period when no drive wheel passes through the low friction road surface portion (instantaneous t3 to t4 and t5 to t6 in FIG. 3). Because it performs the driving force distribution control between the driving wheels to eliminate
The driving force distribution control described above is performed during the period when any of the driving wheels is passing through the low friction road surface portion, causing an increase in yaw rate change, and this causes a deterioration in running stability. Can be solved.
[0025]
In addition, during the above-described driving force distribution control, only the driving force (F4) of the rear wheel (right rear wheel W4) on the side on which the front wheel (right front wheel W1) slips is controlled to drive for eliminating the yaw rate change. Because we decided to decide the power distribution,
The above-described effects can be achieved only by controlling the driving force of one wheel, and the control can be simplified.
[0026]
Also, the front wheel (right front wheel W1) before the rear wheel (right rear wheel W4) on the side where the slip occurs passes through the low friction road surface portion (before the moment t4 in FIG. 3) and after (after the moment t5 in FIG. 3). ) And the driving force control for eliminating the yaw rate change of the rear wheel (right rear wheel W4).
Even if the road surface friction coefficient is different before and after the rear wheel (right rear wheel W4) passes through the low-friction road surface portion, the correction of the yaw rate is compensated for at least one of the above effects. Can be ensured.
[0027]
Further, during the period when the rear wheel (right rear wheel W4) on the side where the front wheel (right front wheel W1) slips passes through the low friction road surface portion, the driving force F4 of the rear wheel (right rear wheel W4) is reduced. Because the slip is reduced to a value that does not cause slipping even on the friction road surface,
The rear wheel (the right rear wheel W4) is prevented from slipping on the low friction road surface portion, and it is possible to avoid the above-described effects from being impaired by this slip.
[0028]
The road surface friction coefficient μ is estimated by comparing the actual acceleration obtained from the wheel speed of the driving wheel with the maximum acceleration that should be obtained under the driving force command of the driving wheel, and this road surface friction coefficient estimated value μ Since the yaw rate change Δφ due to the front wheel (right front wheel W1) slip is estimated from
The estimation of the road surface friction coefficient μ and the yaw rate change Δφ can be easily performed without adding a sensor, which is very advantageous in terms of cost.
[0029]
In this embodiment, the yaw rate change of the vehicle body is eliminated by increasing the driving force of the rear wheels 3 or 4 on the same side as the left and right front wheels 1 or 2 where the slip has occurred. Of course, the same effect can be obtained by reducing the driving force of the front wheel 2 or 1 on the opposite side or the rear wheel 4 or 3. Alternatively, it is a matter of course that the same effect can be obtained even if the driving forces of a plurality of wheels are changed simultaneously, such as simultaneously increasing / decreasing the rear wheels 3 and 4 on both sides.
[Brief description of the drawings]
FIG. 1 is a diagrammatic plan view showing a wheel drive system of an electric vehicle including a yawing behavior control device according to an embodiment of the present invention together with the drive force control device.
FIG. 2 is a block diagram showing a configuration of a wheel drive system and a motor controller of the electric vehicle according to the embodiment.
FIG. 3 is a time chart showing wheel speeds, detection signals, estimation signals, driving force, and yaw rate change amount of the electric vehicle according to the embodiment;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Battery 2 Motor drive force controller 3FL, 3FR, 3RL, 3RR Wheel speed sensor 4 Accelerator opening degree sensor W1 Right front wheel W2 Left front wheel W3 Left rear wheel W4 Right rear wheel M1, M2, M3, M4 Motor INV1, INV2, INV3 INV4 Inverter 11 Reference driving force calculating unit 12 Driving force synthesizing unit 13 Wheel speed calculating unit 14 Slip detecting unit 15 Road surface friction coefficient estimating unit 16 Yaw rate change amount estimating unit 17 Rear wheel passage period estimating unit 18 Delay processing unit 19 Yaw rate correcting driving force Calculation unit 20 Low-friction road surface driving force reduction amount calculation unit

Claims (5)

In vehicles with multiple drive wheels on the left and right, and all drive wheels can control drive power independently,
When the drive wheel ahead in the running direction slips while passing through the low friction road surface portion, and the yaw rate change occurs in the vehicle body, the drive wheel behind the running direction on the side where the slip occurs causes the low friction road surface portion. A yawing behavior control apparatus for a vehicle, characterized in that the driving force distribution between the driving wheels is determined so as to eliminate the change in yaw rate during a period other than the period passing through the vehicle. In the yawing behavior control device according to claim 1,
The vehicle yawing is configured to determine the driving force distribution for eliminating the yaw rate change by controlling only the driving force of the driving wheel behind the running direction on the side where the slip occurs. Behavior control device. In the yawing behavior control device according to claim 2,
The drive wheels on the side where the slip is generated are configured to perform drive force control for canceling the yaw rate change of the drive wheels by dispersing the drive wheels behind the running direction before and after passing through the low friction road surface portion. A yawing behavior control device for a vehicle characterized by the above. In the yawing behavior control device according to claim 2 or 3,
During the period in which the driving wheel behind the running direction on the side where the slip occurs passes through the low friction road surface portion, the driving force of the driving wheel is set to a value at which no slip occurs even on the low friction road surface portion. A yawing behavior control device for a vehicle, characterized by being configured to decrease. In the yawing behavior control device according to any one of claims 1 to 4,
The road surface friction coefficient is estimated by comparing the actual acceleration of the driving wheel and the maximum acceleration that should be naturally obtained under the driving force command of the driving wheel, and the yaw rate change is estimated from the estimated value of the road surface friction coefficient. A yawing behavior control apparatus for a vehicle characterized by the above.

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