JP2711740B2 - Target slip rate estimation device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a target slip ratio estimating apparatus for estimating a target slip ratio for antilock brake control, traction control, and the like, and particularly to a target slip ratio estimating device when a vehicle turns. The present invention relates to a target slip ratio estimating device that sets a target slip ratio based on a friction coefficient between a wheel and a road surface obtained from a motion state.

[Prior Art] For antilock brake control, traction control, and the like, it is necessary to obtain a slip ratio between a target tire and a road surface. For example, when starting on a slippery road surface or accelerating during running, the torque transmitted to the drive wheels is controlled.However, in this type of torque control, idling of the drive wheels is detected and the torque generated by the engine is detected. By reducing this, the slip ratio is made to converge to the target slip ratio set in advance. This target slip ratio is calculated based on snowy roads (low friction roads)
It is set to be suitable for a certain road surface.

[Problem to be Solved by the Invention] By the way, the above-mentioned one is set to be suitable for one road surface having a target slip ratio. However, the target slip ratio with the highest efficiency differs depending on the road surface conditions such as a road surface having a high friction coefficient and a road surface having a low friction coefficient. Therefore, if the target slip ratio is set to be suitable for a certain road surface, there is a problem that the target slip ratio is not suitable for another road surface.

Also, Japanese Patent Application Laid-Open No. 60-248466, "Vehicle braking force control device"
Discloses a device that calculates a reference yaw rate from a vehicle speed and a steering angle, determines whether the vehicle is understeer or oversteer from the reference yaw rate and the actual yaw rate, and uses the determination result in antilock brake control. However, this control simply variably controls the braking force on the rear wheel or the front wheel in accordance with the sign of the difference between the reference yaw rate and the actual yaw rate or the threshold value determination result. The slip ratio is calculated on the basis of the above, and the slip ratio is not used for estimating the friction coefficient of the road surface or estimating the optimum target slip ratio. Further, even if the side slip ratio is calculated, it is apparent that the friction coefficient of the road surface or the optimum target slip ratio cannot be accurately estimated unless the magnitude of the lateral stress generated in the vehicle body due to the steering is determined.

Japanese Patent Application Laid-Open No. 64-16460 discloses an apparatus for calculating a vehicle speed from a driven wheel speed. However, this method only responds to the target slip ratio at which the optimum value changes according to the friction coefficient of the road surface, etc., by simply increasing the target slip ratio as the maximum acceleration increases, and corresponding to the road surface condition. It has problems such as difficulty in fine-grained slip control.

Japanese Utility Model Application Laid-Open No. 63-126818 discloses a device for calculating a yaw rate from left and right wheel speeds. However, this method only calculates a running state quantity such as a yaw rate and a centripetal acceleration based on a calculated value of a turning radius of the vehicle.However, the calculated yaw rate and the centripetal acceleration are used for antilock brake control and traction control. There is no disclosure of how to utilize the technology, and there is little technology or suggestion that can be diverted to vehicle running control adapted to the friction coefficient of the road surface.

Japanese Unexamined Patent Publication No. Hei 1-103564 discloses a "vehicle travel stabilization control device" which determines the stability of a vehicle based on a side slip angle (an angle between a center axis of the vehicle in the front-rear direction and a traveling direction of the vehicle). An apparatus is disclosed. This one is
Although the side slip angle is calculated as the value obtained by multiplying the square of the vehicle speed by the yaw rate, the friction coefficient between the road surface and the wheels is estimated as a function of the longitudinal acceleration obtained by time-differentiating the vehicle speed. Therefore, there is no direct relationship between the sideslip angle and the estimated friction coefficient, and there is a problem that these parameters cannot be effectively used for antilock brake control and traction control.

Japanese Unexamined Patent Publication No. Hei 2-3511 "Active suspension" includes a device which can perform suspension control according to a road surface friction coefficient by determining a threshold value of an output of a sensor for detecting a lateral acceleration of a vehicle body. Is disclosed.
However, when the lateral acceleration is 0.2 to 0.3 G or less, it is determined that the vehicle is traveling on a low friction coefficient road,
The proportional gain setting means for the pressure control valve that varies the operating pressure of the fluid pressure cylinder acts to reduce the ratio of the roll moment of the rear wheel to the roll moment of the front wheel. However, it does not estimate the friction coefficient of the road surface from the sideslip rate according to a predetermined calculation formula, and it is difficult to apply it directly to antilock brake control and traction control. It was something to hold.

The present invention provides a target slip ratio estimating device that estimates a friction coefficient by focusing on a motion state of a vehicle at the time of turning, and is capable of obtaining an efficient target slip ratio corresponding to a road surface in different states of the friction coefficient or various states. It is something to offer.

Means for Solving the Problems In order to achieve the above object, the present invention calculates a vehicle speed from a rotational speed of a pair of right and left driven wheels and a rotational speed of the pair of left and right driven wheels. Driven yaw rate calculating means for obtaining a yaw rate of the vehicle body from the rotational speed of the driven wheel; a steering angle sensor for detecting a steering angle of the vehicle body; and a norm for obtaining a standard yaw rate from the steering angle and the vehicle body speed. A yaw rate calculating means, a skid rate calculating means for subtracting a value obtained by dividing the yaw rate by the reference yaw rate from 1 to obtain a skid rate, an acceleration sensor for detecting acceleration in a center direction when the vehicle turns, and an acceleration sensor in the center direction. Friction coefficient calculating means for dividing the acceleration of the side by the side slip rate, to determine the friction coefficient between the wheel and the road surface,
Target slip ratio calculating means for calculating an optimum target slip ratio from the friction coefficient.

Example The present invention will be described based on an example shown in the drawings. FIG. 1 is a block diagram showing a circuit configuration and an explanatory diagram of acceleration detection during turning of a vehicle.

First, the principle of the present invention will be described with reference to FIG. Normally, when the vehicle C is making a steady circular turn with a speed V and a radius R, the vehicle C is subjected to a central acceleration having a magnitude of κ · V / R (κ is a constant). Coincides with the detection value of the lateral G sensor 4 mounted on the camera. However, when the road surface has a low coefficient of friction, the trajectory T of the vehicle C swells and the lateral force becomes small, so that the two do not coincide with each other. In the present invention, the ratio of the deviation of the yaw rate and the acceleration αG obtained from the lateral G sensor 4 are described.
The friction coefficient μ is estimated from the above equation, and the target slip ratio TS is to be obtained based on the friction coefficient μ.

Now, the vehicle is provided with wheel speed sensors 1, 1, 2, and 2 for the driving wheels and the driven wheels, respectively. Further, the steering device is provided with a steering angle sensor 3 for detecting a steering angle θ (THTA). A lateral G sensor 4 for detecting a lateral acceleration αG of the vehicle body is provided at an appropriate position on the vehicle body.

Data F1 (VWR, VWL) obtained by the wheel speed sensors 1 and 1 provided on the drive wheels are input to the drive wheel speed calculation circuit 6 via LPFs 5 and 5. The drive wheel speed calculation circuit 6 calculates the drive wheel speed VW from the input data F1 (VWR, VWL). The data of the driving wheel speed VW obtained here is output to the slip ratio calculation circuit 7.

Data F2 (VVR, VVL) and F3 (VVR, VVL) obtained by the wheel speed sensors 2, 2 provided on the driven wheels are LP.
The signals are input to the vehicle speed calculation circuit 8 and the yaw rate calculation circuit 9 via F5 and F5. The vehicle speed calculation circuit 8 calculates the vehicle speed VV from the input data F2 (VVR-VVL), and outputs the data of the vehicle speed VV to the slip ratio calculation circuit 7 and the reference yaw rate calculation circuit 10. The yaw rate calculation circuit 9 calculates the yaw rate Y from the input data F2 (VVR, VVL) and outputs the calculated yaw rate Y to the sideslip rate calculation circuit 11.

In the slip ratio calculation circuit 7, the equation (VW
−VV) / VW is used to calculate the slip ratio S, and the calculation result is output to the driving force controller 12.

In the reference yaw rate calculation circuit 10, the data F3 (VV, TV) input from the vehicle speed calculation circuit 8 and the steering angle sensor 3 are input.
HTA), and calculates the reference yaw rate W, and outputs the calculation result to the side slip rate calculation circuit 11.

Data (Y, W) input from the yaw rate calculation circuit 9 and the reference yaw rate calculation circuit 10 in the sideslip ratio calculation circuit 11
The side slip ratio β is calculated based on the equation (1−Y / W), and the calculation result is output to the friction coefficient calculation circuit 13.

Data αG from the lateral G sensor 4 is input to the friction coefficient calculation circuit 13 via the LPF 4a and the A / D converter 4b. The friction coefficient calculation circuit 13 calculates the friction coefficient μ using the formula k · αG / β (k is a constant) based on the data (αG, β) from the lateral G sensor 4 and the side slip rate calculation circuit 11,
The calculation result is output to the target slip ratio calculation circuit 14. The target slip ratio calculation circuit 14 calculates a target slip ratio TS based on the data F4 (μ) from the friction coefficient calculation circuit 13 and outputs the target slip ratio TS to the driving force controller 12.

In such a configuration, the rotational speed data F1 (VWR, VWL) of the drive wheels detected by the drive wheel speed sensors 1 and 1 is input to the drive wheel speed calculation circuit 6 to calculate the drive wheel speed VW, and the calculation result VW Is input to the slip ratio calculation circuit 7.
The rotation speed data F2 (VVR, VVL) of the driven wheels detected by the driven wheel speed sensors 2 and 2 are output from a vehicle speed calculation circuit 8
And the yaw rate calculation circuit 9.

The rotation speed data F2 of the driven wheels described above is calculated by the vehicle speed calculation circuit 8.
Is output to the slip rate calculation circuit 7 and the reference yaw rate calculation circuit 10. The yaw rate Y obtained by the yaw rate calculation circuit 9 based on the rotational speed data F2 of the driven wheel is output to the side slip rate calculation circuit 11.

In addition to the vehicle speed VV from the vehicle speed calculation circuit 8 described above, data θ, that is, THTA from the steering angle sensor 3 is also supplied to the reference yaw rate calculation circuit 10, and F4 (VV, THTA)
, The reference yaw rate W is obtained.

In the slip ratio calculating circuit 7 to which the data from the driving wheel speed calculating circuit 6 and the vehicle speed calculating circuit 8 are inputted, the slip ratio S is calculated, and the calculation result is obtained by the driving force controller.
On the other hand, the reference yaw rate W is output to F4 (VV, THTA) in the reference yaw rate calculation circuit 10 which receives the data F3 (VV, THTA) from the vehicle speed calculation circuit 8 and the steering angle sensor 3 while outputting the data to the reference yaw rate W.
And is output to the skid ratio calculating circuit 11.

The sideslip ratio calculation circuit 11 calculates the sideslip ratio β using the equation (1-Y / W), and outputs the calculation result to the friction coefficient calculation circuit 13.
Output to The data αG from the lateral G sensor 4 is also input to the friction coefficient computing circuit 13, and the data αG from the lateral G sensor 4 and the data β from the lateral slip ratio computing circuit 11 are used to calculate the tire and tire by the formula k · αG / β. The friction coefficient μ of the road surface is calculated, and the calculation result is output to the target slip ratio calculation circuit 14. In the target slip ratio calculation circuit 14, the input data F5
The target slip ratio TS is calculated from (μ), and the calculation result is output to the driving force controller 12. Driving force controller
At 12, control is performed based on the data TS from the target slip ratio calculation circuit 14 and the data S from the slip ratio calculation circuit 7 so that the slip ratio S converges on the target slip ratio TS. As a result, the starting and acceleration performance can be improved particularly on a road surface having a small friction coefficient such as an icy road. In addition. The control of the driving force includes reduction of the fuel injection amount, adjustment of the ignition timing, and the like.

As described above, according to the target slip rate estimating device, the yaw rate Y obtained from the rotational speeds VVL and VVR of the pair of left and right driven wheels is divided by the reference yaw rate W obtained from the steering angle θ and the vehicle speed VV. , The obtained value Y / W is subtracted from 1 to obtain the skid ratio β ｛= 1− (Y / W)｝, and further, the acceleration αG toward the center that appears when the vehicle turns is divided by the skid ratio β to obtain a coefficient. multiplied by k, the friction coefficient μ between the wheel and the road surface is determined as k · αG / β, and the optimum target slip ratio TS is calculated based on the friction coefficient μ. Is determined as μ = k · αG / β = k · αG / {1− (Y / W)}, whereby the ratio of the deviation between the yaw rate Y and the reference yaw rate W in the motion state during turning of the vehicle is calculated. 1 / ｛1-
(Y / W)} and an output αG of an acceleration sensor called a lateral G sensor or the like can be estimated.

For this reason, αG and 1 / {1- (Y / W)}, which are dominant factors in estimating the friction coefficient μ between the wheel and the road surface,
Regardless of the physical specifications of the vehicle structural parts, detection is performed based only on the physical quantity observed on the vehicle, and the empirical value is adopted as the coefficient k according to the substance, so that the friction coefficient μ with extremely high precision Estimation is possible, and by estimating the target slip ratio ST based on the accurate friction coefficient μ, the most efficient target slip ratio suitable for the road surface condition can be set.

[Effects of the Invention] As is apparent from the above description, according to the present invention, the yaw rate Y obtained from the rotation speeds VVL and VVR of the pair of left and right driven wheels is calculated based on the steering angle θ and the vehicle speed VV. The value is divided by the yaw rate W, and the obtained value Y / W is subtracted from 1 to obtain the skid rate β ｛= 1− (Y / W)｝. Multiplied by a coefficient k to obtain a friction coefficient μ between the wheel and the road surface as k · αG / β, and an optimal target slip ratio TS is calculated based on the friction coefficient μ. The coefficient of friction μ between the vehicle and the road surface is determined as μ = k · αG / β = k · αG / {1- (Y / W)}, so that the yaw rate Y and the reference yaw rate W in the motion state during turning of the vehicle are obtained. 1 / ｛1-
(Y / W)｝ and the output αG of an acceleration sensor called a lateral G sensor or the like, which is a dominant factor in estimating the friction coefficient μ between the wheel and the road surface.
G and 1 / {1- (Y / W)} are detected based on only the physical quantities observed on the vehicle, regardless of the physical specifications of the vehicle structural parts, and experienced as a coefficient k that matches the substance. By adopting the value, it is possible to estimate the friction coefficient μ with extremely high accuracy, and the target slip ratio ST is calculated based on the accurate friction coefficient μ.
By estimating, the most effective target slip ratio suitable for the road surface condition can be set, and so on.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a circuit configuration of an embodiment of a target slip ratio estimating apparatus according to the present invention, and FIG. 2 is an explanatory diagram of acceleration detection during turning of the vehicle. (Description of reference numerals in drawings showing main parts) 1, 1, 2, 2 ... wheel sensor 3 ... steering angle sensor 4 ... lateral G sensor 6 ... drive wheel speed calculation circuit 7 ... slip ratio calculation circuit 8 Body speed calculation circuit 9 Yaw rate calculation circuit 10 Standard yaw rate calculation circuit 11 Side slip rate calculation circuit 12 Driving force controller 13 Friction coefficient calculation circuit 14 Target slip rate titration circuit

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical display location B60T 8/66 B60T 8/66 B F02D 29/02 311 F02D 29/02 311A

Claims (1)

(57) [Claims] A driven wheel sensor for detecting a rotational speed of a pair of left and right driven wheels; a driven wheel calculating means for calculating a vehicle speed from the rotational speeds of the pair of left and right driven wheels; A yaw rate calculating means for obtaining a yaw rate of the vehicle, a steering angle sensor for detecting a steering angle of the vehicle body, a reference yaw rate calculating means for obtaining a standard yaw rate from the steering angle and the vehicle body speed, and a value obtained by dividing the yaw rate by the standard yaw rate. Is subtracted from 1 to obtain a side slip ratio, an acceleration sensor that detects acceleration in the center direction when the vehicle turns, and an acceleration in the center direction divided by the side slip ratio to obtain a wheel and road surface. Friction coefficient calculating means for calculating a friction coefficient between the two, and target slip rate calculating means for calculating an optimum target slip rate from the friction coefficient. Target slip rate estimating apparatus.