JP3275320B2 - Wheel slip condition evaluation device - Google Patents

Abstract

PURPOSE:To correctly evaluate the slip state of a vehicle. CONSTITUTION:The first evaluation value indicating the longitudinal slip quantity of wheels is calculated based on the rotating speed difference of the wheels detected by wheel speed sensors 44a-44d. The reference lateral acceleration of a vehicle is calculated based on the vehicle speed calculated based on rotating speeds of the wheels and the yaw rate detected by a yaw rate sensor 45, and the second evaluation value indicating the lateral slip quantity of the wheels is calculated based on the difference between the reference lateral acceleration and the lateral acceleration detected by a lateral acceleration sensor 47. The reference yaw rate of the vehicle is calculated based on the calculated vehicle speed and the steering angle detected by a front wheel steering angle sensor 43, and the third evaluation value indicating the slip quantity of the wheels around the vertical axis is calculated in response to the difference between the reference yaw rate and the detected yaw rate. The maximum value of the first through third evaluation values is extracted as the value indicating the final slip state of the wheels.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for evaluating the slip state of a wheel for evaluating the slip state of a wheel, and more particularly to a method for evaluating the slip state of a wheel by enabling the slip state to be output numerically. The present invention relates to a wheel slip state evaluation device that can be used for a warning device for notifying a vehicle, or a vehicle various control device that controls a steering characteristic, a driving characteristic, and the like of the vehicle.

[0002]

2. Description of the Related Art Conventionally, a slip of a wheel has been detected, and in response to this detection, a brake hydraulic pressure applied to the wheel at the time of vehicle braking has been controlled, and acceleration during a vehicle turning has been limited. It is well known that the vehicle can run stably by controlling the steering characteristic of the vehicle. In this case, when detecting the slip state of the wheel, the wheel idling (slip) is detected based on the rotational speed of the wheel. (See, for example, JP-A-62-146762)

[0003]

However, in the above-mentioned conventional apparatus, the slip state of the wheel is detected based only on the rotational speed of the wheel, that is, the slip in the front-back direction. However, even if the wheel slips or the wheel slips around the vertical axis, the slip cannot be accurately detected, and the slip state of the wheel cannot be accurately evaluated. SUMMARY OF THE INVENTION The present invention has been made to address the above-described problem, and an object of the present invention is to provide a wheel slip state evaluation device that accurately evaluates a wheel slip state.

[0004]

In order to achieve the above object, a first structural feature of the present invention is a wheel speed detecting means (wheel speed detecting means for detecting the rotational speed of each of a plurality of wheels). Sensors 44a to 44d) and vehicle speed detecting means for detecting the vehicle speed (the wheel speed sensors 44a to 44d of the embodiment,
The yaw rate sensor 45, the longitudinal acceleration sensor 46, and the processing of steps 106 to 112), lateral acceleration detecting means (corresponding to the lateral acceleration sensor 47 of the embodiment) for detecting the lateral acceleration of the vehicle, and detecting the yaw rate of the vehicle. Yaw rate detecting means (corresponding to the yaw rate sensor 45 of the embodiment)
And a first evaluation value calculating means for calculating a first evaluation value representing the amount of wheel slip in the front-rear direction substantially in proportion to a difference between the detected rotation speeds based on the detected rotation speeds (step 1 of the embodiment).
Reference lateral acceleration calculation means (step 118 in the embodiment) which calculates an ideal lateral acceleration for the turning vehicle as a reference lateral acceleration based on the detected vehicle speed and the detected yaw rate. with the corresponding) to the processing, the detected to the difference between the two lateral acceleration based on the difference of the lateral acceleration and the calculated reference lateral acceleration substantially in proportion second evaluation value representing the slip in the lateral direction of the wheel The second to calculate
Evaluation value calculating means (corresponding to the processing of step 120 and 122 in the embodiment), first and second evaluation values the calculated
Slip state evaluation value deriving means (Step 13 in the embodiment ) for deriving the maximum value as the evaluation value of the wheel slip state.
2). Further, a second structural feature of the present invention is that a wheel speed detecting means (corresponding to the wheel speed sensors 44a to 44d of the embodiment) for detecting each rotational speed of each of the plurality of wheels, and a vehicle speed detecting device for detecting the vehicle speed are provided. Means (wheel speed sensors 44a to 44d, yaw rate sensor 45, longitudinal acceleration sensor 46, and step 106 in the embodiment)
To 112) and a steering angle detecting means for detecting a front wheel steering angle (corresponding to the front wheel steering angle sensor 43 of the embodiment).
A yaw rate detecting means (corresponding to the yaw rate sensor 45 of the embodiment) for detecting the yaw rate of the vehicle; First evaluation value calculating means (steps 114 and 116 in the embodiment) for calculating a first evaluation value representing
) And reference yaw rate calculating means for calculating an ideal yaw rate for the turning vehicle as a reference yaw rate based on the detected vehicle speed and the detected steering angle (in the processing of steps 124 and 126 in the embodiment). Correspondence)
And a second evaluation value for calculating a second evaluation value representing a slip amount of the wheel around the vertical axis in substantially proportion to the difference between the detected yaw rate and the calculated reference yaw rate. Calculation means (steps 128 and 13 in the embodiment)
0) and a slip state evaluation value deriving means (step of the embodiment) for deriving a maximum value of the calculated first and second evaluation values as an evaluation value of a wheel slip state. 132 (corresponding to the process 132). Also,
The third feature of the configuration of the present invention includes a wheel speed detecting means for detecting the respective rotational speeds of the wheels of the multiple respectively (corresponding to the wheel speed sensor 44a~44d embodiment), the vehicle speed detecting means for detecting a vehicle speed (Corresponding to the wheel speed sensors 44a to 44d, the yaw rate sensor 45, the longitudinal acceleration sensor 46, and the processing of steps 106 to 112 of the embodiment), and a steering angle detecting means for detecting the steering angle of the front wheel (the front wheel steering angle sensor of the embodiment) 43), lateral acceleration detecting means for detecting the lateral acceleration of the vehicle (corresponding to the lateral acceleration sensor 47 in the embodiment), and yaw rate detecting means for detecting the yaw rate of the vehicle (corresponding to the yaw rate sensor 45 in the embodiment). A first evaluation value calculating means for calculating a first evaluation value representing the amount of wheel slip in the front-rear direction substantially in proportion to a difference between the detected rotation speeds based on the detected rotation speeds (step in the embodiment); Corresponds to the processing of-flops 114, 116)
A reference lateral acceleration calculating means (corresponding to the processing in step 118 of the embodiment) for calculating an ideal lateral acceleration for the turning vehicle as a reference lateral acceleration based on the detected vehicle speed and the detected yaw rate; A second evaluation value calculation for calculating a second evaluation value representing a lateral sliding amount of the wheel based on a difference between the detected lateral acceleration and the calculated reference lateral acceleration in substantially proportion to a difference between the two lateral accelerations; Means (corresponding to the processing of steps 120 and 122 in the embodiment) and reference yaw rate calculating means (implementation) for calculating an ideal yaw rate for the turning vehicle as a reference yaw rate based on the detected vehicle speed and the detected steering angle. Example steps 124, 1
26) and a third evaluation value representing the amount of slip of the wheel around the vertical axis substantially in proportion to the difference between the detected yaw rate and the calculated reference yaw rate. A third evaluation value calculating means for calculating (corresponding to the processing of steps 128 and 130 in the embodiment), and a maximum value among the calculated first to third evaluation values is calculated as a wheel slip.
There is provided a slip state evaluation value deriving unit (corresponding to the processing of step 132 in the embodiment) which derives as a state evaluation value .

[0005]

According to the first feature of the present invention having the above-described structure, when a slip occurs between the wheels and the road surface in the traveling direction (front-back direction) between the wheels and the road when the vehicle is accelerated or decelerated, a plurality of wheels are provided. A difference corresponding to the amount of slip occurs between the rotational speeds of the wheels, and the amount of slip of the wheel in the front-rear direction is determined by the first evaluation value calculating means by each of the wheels detected by the wheel speed detecting means. Based on the rotation speed, it is calculated as a first evaluation value substantially proportional to the difference between the rotation speeds. If the vehicle is turning in an ideal state (a state in which the amount of wheel slip in the lateral direction is small), the ideal lateral acceleration for the vehicle is determined by the vehicle speed and the yaw rate. The reference lateral acceleration calculation means calculates the reference lateral acceleration based on the vehicle speed detected by the vehicle speed detection means and the yaw rate detected by the yaw rate detection means. On the other hand, during the turning of the vehicle, if a lateral slippage occurs between the wheels and the road surface,
A difference corresponding to the slip amount is generated between the actual lateral acceleration of the vehicle and the reference lateral acceleration, and the slip amount of the wheel in the lateral direction is calculated by the second evaluation value calculating means. Based on the difference between the lateral acceleration detected by the detecting means and the calculated reference lateral acceleration, a second evaluation value is calculated which is substantially proportional to the difference between the two lateral accelerations. Then, the first and second calculated first and second values are calculated by the slip state evaluation value deriving means .
The maximum value among the evaluation values is derived as the evaluation value of the slip state . Further, in the second feature of the present invention configured as described above, the calculation of the first evaluation value is the same, but the calculation of the second evaluation value in the first configuration feature is different. That is, if the vehicle is turning in an ideal state (a state in which the amount of wheel slip in the lateral direction is small), the ideal yaw rate for the vehicle is determined by the vehicle speed and the steering angle of the front wheels. Is calculated as a reference yaw rate by the reference yaw rate calculation means based on the vehicle speed detected by the vehicle speed detection means and the steering angle of the front wheel detected by the steering angle detection means. On the other hand, during turning of the vehicle, if a slip occurs around the vertical axis between the wheel and the road surface,
A difference corresponding to the slip amount occurs between the actual yaw rate of the vehicle and the reference yaw rate, and the slip amount of the wheel about the vertical axis is calculated by the second evaluation value calculating means.
Based on the yaw rate detected by the yaw rate detecting means and the calculated reference yaw rate, the second evaluation value is calculated as a second evaluation value substantially proportional to the difference between the two yaw rates. Also in this second feature, the slip state evaluation value deriving means also calculates the calculated first and second evaluation values.
The maximum value is derived as the evaluation value of the slip state .
Further, in the third aspect of the present invention configured as described above, the first and second evaluation value each said first features of good Unishi are calculated, first of the second feature 2 The evaluation value is calculated as a third evaluation value, and the slip state evaluation value deriving means is used to calculate one of the calculated first to third evaluation values.
Is derived as the evaluation value of the slip state .

[0006]

As described above, according to the first structural feature of the present invention, the amount of wheel slip in the front-rear direction is the first.
Together is calculated as an evaluation value, slippage of car wheels in the lateral direction is calculated as the second evaluation value, these first and second
The maximum value among the evaluation values is derived as the final evaluation value of the wheel slip state . Therefore, first of the present invention
According to a feature on one of the configuration, not only the front-rear direction of the slip on the road surface of the wheels, will be evaluated values slip was also considered against sideways direction is calculated, the slip state of the wheel is a numerical value It can be used to evaluate accurately and easily. Ma
According to the second structural characteristic of the present invention,
The slip amount of the wheel is calculated as a first evaluation value,
The amount of wheel slip around the vertical axis is calculated as the second evaluation value.
The maximum of these first and second evaluation values is
Is derived as a final evaluation value of the slip state. I
Therefore, according to the second structural feature of the present invention,
Not only does the wheel slip on the road surface in the front-rear direction, but also
The evaluation value is calculated taking into account slippage
The wheel slip condition is accurate and simple using numerical values
Can be evaluated. According to the third structural feature of the present invention, the amount of wheel slippage in the front-rear direction, the lateral direction, and the vertical axis is calculated as the first to third evaluation values, and the first to third evaluation values are calculated . The maximum value of the three evaluation values is derived as the final evaluation value of the wheel slip state . The <br/> Therefore, according to a feature of the third configuration of the present invention, will be evaluated value slip is considered for all directions on the road surface of the wheels is calculated, the wheels Can be evaluated more accurately and easily using numerical values.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings . FIG. 1 schematically shows an entire four-wheel steering vehicle to which a wheel slip condition evaluation apparatus according to the present invention is applied.
The four-wheel steering vehicle includes a front wheel steering device 20 for steering left and right front wheels FW1 and FW2, a rear wheel steering device 30 for steering left and right rear wheels RW1 and RW2, and an electric control for electrically controlling the rear wheel steering device 30. Device 40.

The front wheel steering device 20 has a steering shaft 22 having a handle 21 fixed to the upper end. The lower end of the steering shaft 22 is connected to a rack bar 24 supported in the steering gear box 23 so as to be axially displaceable. The bar 24 is axially displaced in accordance with the rotation of the handle 21. At both ends of the rack bar 24, tie rods 25a, 25
b and the left and right front wheels FW1, FW2 are connected via knuckle arms 26a, 26b.
W2 is steered according to the axial displacement of the rack bar 24.

The rear wheel steering device 30 includes an actuator 31 that is electrically controlled. The actuator 31 drives an axially displaceable relay rod 32 provided in the axial direction. A tie rod 33a is provided at both ends of the relay rod 32.
The left and right rear wheels RW1 and RW2 are connected via the knuckle arms 34a and 34b.
1, RW2 is steered according to the axial displacement of the relay rod 32.

The electric control unit 40 has microcomputers 41 and 42. Microcomputer 41
Stores a program corresponding to the flowcharts of FIGS. 2 and 3 and executes each of the wheels FW by executing the program.
1, FW2, RW1, and RW2 are evaluated. Further, this microcomputer 41 has R
It has a table composed of OM, and includes various coefficients and evaluation values GB0, GB1, Tr, LX, LY, γ0, a, b, LZ ( FIGS. 4 to 12 ) .
Reference) is stored.

The inputs of the microcomputer 41 are connected to a front wheel steering angle sensor 43, wheel speed sensors 44a to 44d, a yaw rate sensor 45, a longitudinal acceleration sensor 46, and a lateral acceleration sensor 47. Front wheel steering angle sensor 43
Is mounted on the steering shaft 22, detects the front wheel steering angle θ by detecting the rotation angle of the coaxial 22, and outputs a detection signal representing the steering angle θ. The wheel speed sensors 44a to 44d are provided near each of the wheels FW1, FW2, RW1, and RW2, and the rotational speed V of each of the wheels FW1, FW2, RW1, and RW2.
FL, VFR, VRL, VRR are detected, and the rotation speeds VFL, VFR,
It outputs detection signals representing VRL and VRR, respectively. The yaw rate sensor 45 is fixed at the position of the center of gravity of the vehicle body, detects the yaw rate γ by detecting the rotational angular velocity of the vehicle body about the vertical axis, and outputs a detection signal representing the yaw rate γ. The longitudinal acceleration sensor 46 is also fixed to the vehicle body, detects the longitudinal acceleration GX of the vehicle, and outputs a detection signal representing the acceleration GX. The lateral acceleration sensor 47 is also fixed to the vehicle body, detects the lateral acceleration GY of the vehicle, and detects the same acceleration GY.
Is output. A display control circuit 48 and a lamp 49 are connected to the output of the microcomputer 41. The lamp 49 is capable of displaying green, yellow, and red, and the display color is controlled by the display control circuit 48.

The microcomputer 42 stores a program corresponding to the flowchart of FIG. 13 , and controls the steering of the left and right rear wheels RW1, RW2 by executing the program. The microcomputer 42 has a table constituted by a ROM, and stores a coefficient KY (see FIG. 14 ) in the table. The microcomputer 41 is connected to the microcomputer 41 and the yaw rate sensor 45, and also connected to the rear wheel steering angle sensor 51. The rear wheel steering angle sensor 51 is provided in the vicinity of the relay rod 32, and detects the amount of displacement of the rod 32 to obtain a rear wheel steering angle δr.
And outputs a detection signal representing the steering angle δr.
A drive circuit 52 is connected to the output of the microcomputer 42, and the circuit 52 controls the drive of the actuator 31.

Next, the operation of the embodiment configured as described above will be described. When an ignition switch (not shown) is turned on, the microcomputer 41 starts executing the program in step 100 of FIG. 2 and executes an initial setting process of setting various variables to initial values in step 102. , A circulation process consisting of steps 104 to 136 is repeatedly executed.

In this circulation processing, step 104
, Front wheel steering angle sensor 43, wheel speed sensors 44a-44
d, front wheel steering angle θ, wheel rotation speed V from yaw rate sensor 45, longitudinal acceleration sensor 46, and lateral acceleration sensor 47
FL, VFR, VRL, VRR, yaw rate γ, longitudinal acceleration GX, and lateral acceleration GY are respectively inputted, and coefficients GB0, GB0,
GB1, Tr are read from the table (see FIGS. 4 to 6 ).
In this case, as the vehicle speed V, the value “0” initially set in step 102 is used, but thereafter, the value calculated in step 112 of the previous circulation process is used. Next, in step 108, using the read coefficients GB0, GB1, Tr and the input yaw rate γ, a calculation based on the following equation 1 is executed to calculate the slip angle β of the vehicle.

(Equation 1) In the above formula 1, s is a Laplace operator, and F (s) is a transfer function representing the relationship between the yaw rate γ and the slip angle β of the vehicle.

Next, at step 110, the calculation of the following equation (2) based on the inputted wheel rotational speeds VFL, VFR, VRL, VRR, the yaw rate γ and the calculated slip angle β is performed, and the turning trajectory difference is calculated. Each wheel FW1, FW2, R
Each wheel FW from which wheel rotation speed components of W1 and RW2 have been removed
1, FW2, RW1, RW2 corrected wheel rotation speed V1, V
2. Calculate V3 and V4.

V1 = VFL + t ・ γ / 2 V2 = VFR-t ・ γ / 2 V3 = VRL + t ・ γ / 2 + L ・ β ・ γ V4 = VRR-t ・ γ / 2 + LＶβ ・ γ , T is the tread and L is the wheelbase. With respect to the equation (2), if a little explanation is added with reference to FIG. 15 , the corrected wheel rotational speeds V1, V2, V3, V4
The left and right front wheels FW are calculated using the wheel rotation speeds VFL, VFR, VRL, and VRR of the wheels FW1, FW2, RW1, and RW2 using the yaw rate γ around the center of gravity CC of the vehicle and the slip angle β of the vehicle.
1, the wheel rotation speed at the center position CF of FW2. Thereby, each wheel FW1, due to the difference in turning locus,
The rotation speed difference component of FW2, RW1, RW2 is removed.

Next, at step 112, the vehicle speed V is determined based on the input longitudinal acceleration GX according to the following conditions. A positive predetermined value G0 having a longitudinal acceleration GX of "0" or more and a small absolute value (for example, about 1.0 m / s
² to about 5.0 m / s ² ) (0 ≦ GX ≦ G
0), the vehicle speed V is set to the minimum value MIN (V1, V2, V3, V4) of the corrected wheel rotation speeds V1, V2, V3, V4. Small negative predetermined value of the longitudinal acceleration GX is the absolute value -G0 (e.g., about -5.0m / s ² ~- about 1.0 m / s ²⁾ or more and "0"
When (−G0 ≦ GX ≦ 0), the vehicle speed V is the maximum value MAX (V1, V2, V3, V3) of the corrected wheel rotation speeds V1, V2, V3, V4.
V4). When the longitudinal acceleration GX is less than the negative predetermined value -G0 or larger than the positive predetermined value G0 (G
X <-G0 or GX> -G0), and the vehicle speed V is calculated by executing the following equation (3).

V = V0 + ∫GXdt In Equation 3, the integration constant V0 is determined by the above condition (G
X <−G0 or GX> −G0).

Thus, if the vehicle is in a constant speed traveling state, a slightly increased or decelerated traveling state, that is, each wheel FW1,
When FW2, RW1 and RW2 hardly slip, the corrected wheel rotational speeds V1, V2, V3 and V4 of the wheel having the lowest slip ratio are determined as the vehicle speed V. Also,
If the vehicle is in a speed-up or deceleration running state, that is, each wheel F
When W1, FW2, RW1, and RW2 are slipping, the vehicle speed V is determined by the integral calculation using the longitudinal acceleration GX of the vehicle body. As a result, the vehicle speed V is set to an accurate value that does not include the turning trajectory error and the slip error.

Next, at step 114, the maximum slip ratio X of each wheel FW1, FW2, RW1, RW2 is calculated by executing the calculation of the following equation 4 using the corrected wheel rotational speeds V1, V2, V3, V4. calculate.

(Equation 4) In the above equation (4), the operator AVE represents each corrected wheel rotation speed V
It means to calculate the average value of 1, V2, V3, V4. After the processing in step 114, the first evaluation value LX is read from the table (see FIG. 7 ) based on the maximum slip ratio X calculated in step 116. In this case, since the maximum slip ratio X represents the maximum amount of slip in the traveling direction between each wheel FW1, FW2, RW1, RW2 and the road surface, that is, the front-back direction, the first evaluation value LX is normalized to the maximum value of "1". Represents the amount of slip in the front-rear direction of the wheel.

Next, at step 118, the following equation (5) based on the input yaw rate γ and the calculated vehicle speed V is used.
, The reference lateral acceleration GY * is calculated.

GY * = γ · V Equation (5) represents the lateral acceleration during turning of the vehicle.
This corresponds to the case where dt is “0”, whereby the reference lateral acceleration GY * becomes the lateral direction of the wheels FW1, FW2, RW1, RW2 with respect to the road surface when the vehicle is turning in an ideal state. Represents the lateral acceleration of the vehicle when the slip amount of the vehicle is close to “0”.

GY = [γ + (dβ / dt)] · V

After the processing in step 118, step 1
At 20, the lateral slippage amount Y of the wheel with respect to the road surface is calculated by executing the calculation of the following equation 7 based on the calculated reference lateral acceleration GY * and the input lateral acceleration GY. The second based on the calculated slip amount Y
The evaluation value LY is read from the table (see FIG. 8 ).

[Mathematical formula-see original document] Y = │GY * -GY│ Thus, the lateral slip amount of the wheel with the maximum value normalized to "1" has been calculated as the second evaluation value LY.

Next, at step 124, the coefficients Tr, γ0, a, b are read from the table (see FIGS. 6, 9-11 ) based on the vehicle speed V, and at step 126, the read coefficients Tr, γ0, a are read. , b and the input front wheel steering angle θ, the reference yaw rate γ * is calculated by executing the calculation based on the following equation (8).

(Equation 8) In Equation 8, G (s) is a transfer function representing the relationship between the front wheel steering angle and the yaw rate when the vehicle is turning in an ideal state, and s is a Laplace operator. As a result, the yaw rate of the vehicle in a state where the slip amount of each wheel FW1, FW2, RW1, RW2 around the vertical axis with respect to the road surface is close to “0” is calculated as the reference yaw rate γ *.

After the processing of step 126, step 1
At 28, the slip amount Z about the vertical axis of the center of gravity of the wheel with respect to the road surface is obtained by executing the calculation of the following equation 9 based on the calculated reference yaw rate γ * and the input yaw rate γ.
Is calculated, and the third evaluation value LZ is read from the table (see FIG. 12 ) based on the slip amount Z calculated in step 130.

[Mathematical formula-see original document] Z = │γ * -γ│ Thus, the slip amount about the vertical axis of the center of gravity of the wheel, with the maximum value normalized to "1", is calculated as the third evaluation value LZ.

Next, at step 132, the maximum value LM of the evaluation values LX, LY, LZ is calculated by executing the operation of the following equation 10 based on the calculated first to third evaluation values LX, LY, LZ.
Calculate AX.

LMAX = MAX (LX, LY, LZ)

Next, at step 134, the calculated maximum value LMAX and the first and second reference values (for example, "0.5"
And "0.8"), whether the maximum value LMAX is less than the first reference value, whether the maximum value LMAX is not less than the first reference value and less than the second reference value, or whether the maximum value LMAX is The display control circuit 48 outputs a display control signal indicating whether the value is equal to or more than the second reference value to the display control circuit 48. If the maximum value LMAX is less than the first reference value based on the display control signal,
The lamp 49 is turned on in green. If the maximum value LMAX is equal to or more than the first reference value and less than the second reference value, the lamp 49 is lit yellow, and if the maximum value LMAX is equal to or more than the second reference value, the lamp 49 is lit red. As a result, the driver can visually recognize the slip state of the wheels and reflect the slip state on the driving of the vehicle.

Next, at step 136, a signal representing the calculated maximum value LMAX is output to the microcomputer 42. On the other hand, when the ignition switch is turned on, the microcomputer 42 executes step 20 in FIG.
At 0, the execution of the program is started, and after the initial setting process of step 202, the cyclic process including steps 204 to 210 is repeatedly executed.

In this circulation processing, step 204
At the same time, a signal indicating the maximum value LMAX output from the microcomputer 41 is input, and a detection signal indicating the yaw rate γ and the rear wheel steering angle δr from the yaw rate sensor 45 and the rear wheel steering angle sensor 51 is input. Next, in step 206, the yaw rate coefficient KY is read from the table (see FIG. 14 ) based on the maximum value LMAX, and in step 208, the following equation 11 based on the yaw rate coefficient KY and the yaw rate γ is executed to obtain Calculate the wheel steering angle δr *.

Δr * = KY · γ

After the calculation of the target yaw rate δr *, a control signal representing the difference δr * −δr between the target rear wheel steering angle δr * and the input rear wheel steering angle δr is output to the actuator 31 at step 210. . The actuator 31 displaces the relay rod 32 right and left by an amount corresponding to the difference δr * −δr based on the control signal. This relay rod 32
, The right and left rear wheels RW1 and RW2 are steered to the target rear wheel steering angle δr *. In this case, the yaw rate coefficient KY is set so as to increase as the maximum value LMAX representing the slip amount of the wheel increases, so that the left and right rear wheels RW1 and RW2 become the left and right front wheels FW1 as the slip amount of the wheel increases. , FW2 is largely steered in phase with respect to FW2, and the vehicle is controlled in a stable tendency.

In the above-described embodiment, the slip state of the wheel is displayed by the difference in the lighting color of the lamp 49. However, the slip state is displayed in accordance with the off, blinking and lighting states of the lamp 49. You may make it.
In this case, the display control circuit 48 turns off the lamp 49 when the maximum value LMAX is less than the first reference value, and blinks the lamp 49 when the maximum value LMAX is not less than the first reference value and less than the second reference value, If the maximum value LMAX is greater than or equal to the second reference value, ramp 4
9 may be turned on.

In the above embodiment, the vehicle speed V is detected by using the detected wheel rotational speeds VFL, VFR, VRL, VRR, the yaw rate γ, and the longitudinal acceleration GX (steps 104 to 112). Alternatively, the detection may be performed based on the rotation speed of the output shaft of the transmission.

Further, in the above-described embodiment, only the example in which the wheel slip condition evaluation device according to the present invention is applied to the rear wheel steering device 30 has been described. However, the present invention relates to a vehicle such as a suspension device and an anti-lock brake device. It is clear that the present invention can be used for various kinds of control.

[Brief description of the drawings]

FIG. 1 is an overall schematic view of a vehicle showing one embodiment of the present invention.

FIG. 2 is a part of a flowchart corresponding to a program executed by one microcomputer of FIG. 1;

FIG. 3 is another part of the flowchart corresponding to the program.

FIG. 4 is a characteristic graph of a coefficient GB0 stored in one microcomputer of FIG. 1 and used for calculation.

FIG. 5 is a characteristic graph of a coefficient GB1 stored in one microcomputer of FIG. 1 and used for calculation.

FIG. 6 is a characteristic graph of a coefficient Tr stored in one microcomputer of FIG. 1 and used for calculation.

FIG. 7 is a graph showing a change characteristic of a first evaluation value LX with respect to a maximum slip ratio X stored in one microcomputer of FIG. 1;

FIG. 8 is a graph showing a change characteristic of a second evaluation value LY with respect to a lateral slip amount Y stored in one microcomputer of FIG. 1;

9 is a characteristic graph of a coefficient γ0 stored in one microcomputer of FIG. 1 and used for calculation.

FIG. 10 is a characteristic graph of a coefficient a stored in one microcomputer of FIG. 1 and used for calculation.

11 is a characteristic graph of a coefficient b stored in one microcomputer of FIG. 1 and used for calculation.

FIG. 12 is a graph showing a change characteristic of a third evaluation value LZ with respect to a slip amount Z about a vertical axis of a vehicle center of gravity stored in one microcomputer of FIG. 1;

FIG. 13 is a flowchart corresponding to a program executed by the other microcomputer of FIG. 1;

14 is a characteristic graph of a coefficient KY stored in the other microcomputer of FIG. 1 and used for calculation.

FIG. 15 is an explanatory diagram showing a relationship among wheel rotation speeds VFL, VFR, VRL, VRR, corrected wheel rotation speeds V1 to V4, yaw rate γ, and slip angle β.

[Explanation of symbols]

FW1, FW2: front wheel, RW1, RW2: rear wheel, 20 ...
Front wheel steering device, 30: rear wheel steering device, 40: electric control device, 41, 42: microcomputer, 43: front wheel steering angle sensor, 44a to 44d: wheel speed sensor, 45: yaw rate sensor, 46: longitudinal acceleration sensor, 47: lateral acceleration sensor; 49: ramp; 51: rear wheel steering angle sensor.

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) B60T 8/00 B60T 8/24 B60T 8/58 B60K 28/16 B62D 6/00

Claims (3)

(57) [Claims] An apparatus for evaluating a slip state of a wheel, comprising: a wheel speed detecting means for detecting a rotational speed of each of a plurality of wheels; a vehicle speed detecting means for detecting a vehicle speed; and detecting a lateral acceleration of the vehicle. Lateral acceleration detecting means; yaw rate detecting means for detecting a yaw rate of the vehicle; and a first evaluation value representing a slip amount of a front-rear direction wheel substantially in proportion to a difference between the detected rotational speeds based on the detected rotational speeds. A first evaluation value calculation unit that calculates a lateral acceleration ideal for a turning vehicle based on the detected vehicle speed and the detected yaw rate as a reference lateral acceleration; the difference between the two lateral acceleration based on the difference of the lateral acceleration and the calculated reference lateral acceleration substantially in proportion to the second evaluation value calculation means for calculating a second evaluation value representing the slip in the lateral direction of the wheel was , The maximum value of the calculated first and second evaluation values is
And a slip state evaluation value deriving unit that derives as an evaluation value of the wheel slip state. 2. An apparatus for evaluating a slip state of a wheel, comprising: wheel speed detecting means for detecting a rotational speed of each of a plurality of wheels; vehicle speed detecting means for detecting a vehicle speed; and detecting a steering angle of a front wheel. Steering angle detection means, yaw rate detection means for detecting a yaw rate of the vehicle, and a first evaluation value representing a slip amount of a front-rear direction wheel substantially in proportion to a difference between the detected rotation speeds based on the detected rotation speeds. First yaw rate calculating means for calculating a yaw rate ideal for the turning vehicle based on the detected vehicle speed and the detected steering angle as a reference yaw rate; and the detected yaw rate Calculating a second evaluation value representing a slip amount of a wheel around a vertical axis in substantially proportion to the difference between the calculated yaw rate and the calculated reference yaw rate. Means, and calculating the maximum value of the calculated first and second evaluation values.
And a slip state evaluation value deriving unit that derives as an evaluation value of the wheel slip state. 3. An apparatus for evaluating a wheel slip condition.
Te, wheel speed detection for detecting a plurality of the respective rotational speeds of the wheels respectively
Means, vehicle speed detecting means for detecting a vehicle speed, a steering angle detecting means for detecting a front wheel steering angle, and lateral acceleration detecting means for detecting a lateral acceleration of the vehicle, the yaw rate detecting means for detecting a yaw rate of the vehicle, the Based on the detected rotational speeds, the difference between the rotational speeds
The first evaluation value representing the amount of wheel slip in the front-rear direction in approximately proportion
First evaluation value calculating means for calculating , based on the detected vehicle speed and the detected yaw rate.
The ideal lateral acceleration for a turning vehicle
Reference lateral acceleration calculating means for calculating the detected lateral acceleration and the calculated reference lateral acceleration
And the side of the wheel is approximately proportional to the difference between the two lateral accelerations.
Second evaluation value meter for calculating a second evaluation value representing the amount of slip in the direction
Calculating means , based on the detected vehicle speed and the detected steering angle.
Reference yaw rate based on the ideal yaw rate for turning vehicles
Reference yaw rate calculating means for calculating the detected yaw rate and the calculated reference yaw rate
Of the yaw rate of the vehicle.
Calculating a third evaluation value representing the amount of slip of the wheel about the straight axis;
Third evaluation value calculating means, and calculating the maximum value of the calculated first to third evaluation values
Slip state derived as evaluation value of wheel slip state
A wheel slip state evaluation device comprising: an evaluation value deriving unit .