JPH0228045A - Method for estimating car body speed - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION A8 Object of the Invention (1) Industrial Application Field The present invention relates to a vehicle speed estimation method for estimating vehicle speed using the output of an acceleration sensor whose output is analog.

(2) Conventional technology Conventionally, for example, when estimating the vehicle speed required for anti-lock control, the acceleration and deceleration of the vehicle body detected by an acceleration sensor was used. Since the gravitational acceleration corresponding to the slope of the entire boarding path is already acting on the acceleration sensor, if acceleration and deceleration are equivalent to the slope, the output of the acceleration sensor will be zero.

(3) Problems to be Solved by the Invention The present invention has been made in view of the above circumstances, and eliminates the influence of the entire descent road and estimates the vehicle speed using approximately positive acceleration and deceleration. The object of the present invention is to provide a method for estimating vehicle speed.

B0 Structure of the Invention (1) Means for Solving the Problems The present invention provides a method for estimating vehicle speed using the output of an acceleration sensor whose output is analog. The first feature is that the vehicle speed is estimated based on a value obtained by adding a first set value corresponding to the slope of all the descending roads.

The present invention also provides a second method of determining whether the vehicle is in an acceleration state or a deceleration state by comparing the estimated vehicle speed and the wheel speed, and using the absolute value of the output of the acceleration sensor to estimate the vehicle speed. Features.

The third feature of the present invention is that the first set value is 0.2G.

A fourth feature of the present invention is that the second set value is equal to or less than the second set value of the absolute value of the output of the acceleration sensor.

Furthermore, the fifth feature of the present invention is that the second set value is set in a range of 0.5 to 0.8G.

(2) Effect According to the first feature, the force obtained by the acceleration sensor,
Since the deceleration is set to a positive value and the first set value is added to that value, the influence of the climbing slope on the acceleration sensor can be eliminated.

According to the second feature, by determining acceleration and deceleration states separately from the output from the acceleration sensor, the absolute value of the output from the acceleration sensor can be used to estimate the vehicle speed.

According to the third feature, by setting the first set value to 0.2 G, it becomes possible to cope with all the exit roads on which the vehicle may travel.

According to the fourth feature, since the lower limit of the absolute value of the output of the acceleration sensor becomes the second set value, when the acceleration sensor used for estimating the vehicle speed fails while its output is small, the estimated vehicle speed It becomes possible to maintain the level of

According to the fifth feature, an estimated vehicle speed level that does not cause any problem during normal running of the vehicle is ensured.

(3) Example Below, an example of the present invention will be explained with reference to the drawings. First, in FIG. controlled by an anti-lock brake control circuit l when the front wheels are about to lock;
The braking oil pressure of the rear wheel brakes installed on both rear wheels is controlled by an anti-lock brake control circuit when the corresponding rear wheel is about to lock up. That is, each anti-lock brake control circuit IF includes one control section I FL, one corresponding to each of the left and right wheels respectively.
11L and 1□, and their control units IFL, 1□1liL, and 1++++ determine that the slip rate has exceeded the allowable value when the corresponding wheel speed falls below the reference wheel speed and take appropriate action. anti-lock brake control for the wheel brakes.

The reference wheel speed is obtained by multiplying the vehicle speed by a constant slip ratio, and the anti-lock brake control circuit IF receives the vehicle speed v estimated based on the speeds of both front axles.
rv is input, and the anti-rotation brake control circuit 1.
l is the vehicle body speed VaV estimated based on both rear wheel speeds.
is input.

In order to estimate such vehicle speed ■FV+VIV,
Speed sensors 2 FLI 2 Fl are installed on both front axles, and speed sensors 21+L and 2 are installed on both rear wheels.
A and l are respectively attached. Speed sensor 2FL,
The front wheel speed VFL14 + ■FRW obtained from 2□ is input to the low select circuit 3, and is also input to the speed sensor 2.
Rear wheel speed obtained with RLI 2 +u+ H+
VIIIW is input to the low select circuit 4.

In the low select circuit 3, the input both front axle speeds Vrt
The lower wheel speed among w and V□ is selected as the front wheel speed vF,1, and the low select circuit 4 selects the input rear wheel speeds VIILIII and Vllllo.
Among them, the lower wheel speed is selected as the rear wheel speed ■1. Based on the wheel speeds V yH, V HH selected by such low select circuits 3 and 4 and the output of the acceleration sensor 5 mounted on the vehicle, the estimated front wheel side vehicle body speed V□ and the estimated rear wheel side vehicle body speed are determined. The speed ■□ is obtained by the front wheel side vehicle speed estimating means 6F and the rear wheel side vehicle speed estimating means 66, and these estimated vehicle speeds V, v, V□ are input to the corresponding anti-lock brake control circuits 1y, L, respectively. Ru.

The acceleration sensor 5 is an analog sensor having output characteristics as shown in FIG. The signal is input to the conversion circuit 8. Thus, the output IAI of the absolute value converting circuit 8 becomes as shown in FIG.

The output IAI of the absolute value converting circuit 8 is input to an adder circuit 9, and the adder circuit 9 performs the following calculation.

A’ = A + A.

Here, A+ is the first setting value corresponding to the acceleration and deceleration that acts on the vehicle body due to the slope of the entire exit road, for example, and is set to 0.2G, for example, in order to cope with the entire exit road on which the vehicle may travel. Set. As a result, the output from the adder circuit 9 is, as shown in FIG. 4, the output IAI of the absolute value conversion circuit 8 shown in FIG. 3, offset by A.

The output terminal of the adder circuit 9 is connected to the non-inverting input terminal of the comparator circuit 10 and one of the individual contacts 11 . connected to. Further, a signal corresponding to the second set value A2 is inputted from a terminal 12 to the inverting input terminal of the comparator circuit 10, and the terminal 12 is connected to the other individual contact 11. of the switch 11. It is also man-powered. The second set value A2 is determined in the range of 0.5 to 0.8 G as an acceleration that does not cause problems during normal driving even if the acceleration sensor 5 fails, and for example, a signal corresponding to 0.8 G. is input to terminal 12.

When the output of the comparison circuit 10 is at a high level, the comparison circuit 10 connects the common contact 11c of the switch 11 to the one individual contact 11. and one common contact when the output is low level. to the other individual contact 11. This is what connects it to.

Therefore, when the output of the adder circuit 9 exceeds the second set value A, the adder circuit 9
is output as is, and when the output of the adder circuit 9 is less than the second set value A2, the common contact 11C of the switch 11
Since the second set value A2 is outputted from the common contact 11. of the switch 11. The output is as shown in FIG. 5, and the lower limit value of acceleration and deceleration after being converted into absolute values becomes the second set value A2.

A common contact 11c of the switch 11 is connected to a non-inverting input terminal of the comparison circuit 13, and one individual contact 14. connected to. On the other hand, a terminal 15 is connected to the inverting input terminal of the comparison circuit 13, and this terminal 15 is also connected to the other individual contact 14k of the switch 14. A third set value A is inputted to the terminal 15, and this third set value A is set corresponding to the maximum acceleration and deceleration expected in a four-wheeled vehicle, for example, 1.4G.

The comparison circuit 13 is a common contact 11c in the switch 11.
When the output is equal to or less than the third set value A, a low level signal is output and the common contact 14c of the switch 14 is connected to one of the individual valve contacts 14. When the third set value A is exceeded, a high level signal is output and the common contact 14 is connected to the common contact 14.
c is connected to the other individual contact 141, and therefore acceleration and deceleration with positive signs are output from the common contact 14c of the switch 14 with the maximum value as the third set value A3.

The common contact 14c of the switch 14 is connected to a setting circuit 16, and the setting circuit 16 sets a speed difference ΔV over a certain period of time from acceleration and deceleration input with positive signs.

The front wheel side vehicle speed estimating means 6F includes a comparison circuit 17F, an addition circuit 181. Subtraction circuit 19. and switch 20. Equipped with Wheel speed output from low select circuit 3■,
is the comparison circuit 17. is input to the non-inverting input terminal of addition circuit 18 and subtraction circuit 19 . is input. Also, the output of the setting circuit I6, that is, the speed difference ΔV is an addition gate! 18 and a subtraction circuit 191 . Thus, the addition circuit 18F and the subtraction circuit 19. Then, the following addition and subtraction processing is performed.

VFV=Vyw+AV VFV=VFW-Δ■ Also, the switch 20 is connected to the addition@path 18. and subtraction circuit 1
9F and the front wheel side anti-lock brake control circuit IF7, and the comparison circuit 17. When the output of the comparator circuit 17. is at a high level, the adder port 1a18v is connected to the front wheel side anti-lock brake control circuit IF, and the comparator circuit 17. When the output of is low level, the subtraction circuit 19
Connect F to the front wheel side anti-lock brake control circuit l. Furthermore, the output signal of the switch 2°F, that is, the estimated vehicle speed vyv, is input to the inverting input terminal of the comparison circuit 17F. Therefore, the comparison circuit 17F calculates the estimated vehicle speed V
By comparing FV and wheel speed V1, it is determined whether the vehicle is in an acceleration state or a deceleration state, and in an acceleration state, the addition circuit 18. output, and in the deceleration state, the subtraction circuit 19
The output of F is output as the estimated vehicle speed vFv.

Rear wheel side vehicle speed estimation means 6. has basically the same structure as the front wheel side vehicle speed estimating means 6F and performs the same function, and includes a comparison circuit 17 and an addition port 1i1i8.
*, subtraction circuit 19 and switch 20. Equipped with

Next, the operation of this embodiment will be explained. By converting the output of the acceleration sensor 5 into an absolute value, acceleration and deceleration have positive values as shown in FIG. 3. Moreover, by adding the first set value A+ to the acceleration and deceleration converted into absolute values, it is possible to eliminate the influence on the acceleration sensor 5 on all descent routes, and the first set value A+ is set to 0.2.
By setting it to G, it is possible to cope with all the exit roads on which the vehicle may travel.

By the way, the vehicle speed is estimated based on the output of the acceleration sensor 5, and the anti-lock brake control is performed based on the estimated vehicle speed, so if the acceleration sensor 5 fails when its output is small, the anti-lock brake control is performed. This will cause problems. However, since the absolute minimum value of acceleration and deceleration is set as the second setting value A2, and the second setting value A2 is set to approximately 0.5 to 0.8G, even if the acceleration sensor 5 fails, the vehicle It is possible to secure an estimated vehicle speed level that does not cause problems during normal driving.

C3 Effects of the Invention As described above, according to the first feature of the present invention, the absolute value of the output of the acceleration sensor has a first value corresponding to the slope of the entire descent path.
Since the vehicle speed is estimated based on the sum of the set values, the vehicle speed can be estimated almost accurately by eliminating the influence on the acceleration sensors of all the exit roads.

According to the second feature of the present invention, it is determined whether the vehicle is in an acceleration state or a deceleration state by comparing the estimated vehicle speed and the wheel speed, and the absolute value of the output of the acceleration sensor is used to estimate the vehicle speed. Therefore, it is possible to determine acceleration and deceleration states separately from the acceleration sensor, and use the absolute value of the output of the acceleration sensor to estimate the vehicle speed.

According to the third feature of the present invention, since the first set value is set to 002G, it is possible to deal with all exit roads on which the vehicle may travel.

According to the fourth feature of the present invention, since the second set value or less of the absolute value of the output of the acceleration sensor is set as the second set value, the acceleration sensor used for estimating the vehicle speed may fail when its output is small. In some cases, it is possible to maintain the estimated vehicle speed above a certain level.

According to the fifth feature of the present invention, since the second set value is set in the range of 0.5 to 0.8G, an estimated vehicle speed level that does not cause any problems during normal vehicle running is ensured.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention. Fig. 1 is an overall block diagram, Fig. 2 is an output characteristic diagram of the acceleration sensor, Fig. 3 is an output characteristic diagram of the absolute value converting circuit, and Fig. 4 is an absolute value diagram. Fig. 5 is a characteristic diagram showing a state in which the acceleration and deceleration converted into absolute values are offset with the first set value, and Fig. 5 is a characteristic diagram showing a state in which the acceleration and deceleration converted into absolute values are canted off with the second set value. . 5... Acceleration sensor,

Claims (5)

[Claims] (1) In a vehicle speed estimation method that estimates vehicle speed using the output of an acceleration sensor whose output is analog,
A method for estimating a vehicle speed, comprising estimating the vehicle speed based on a value obtained by adding a first set value corresponding to an inclination of an uphill/downhill road to an absolute value of an output of an acceleration sensor. (2) By comparing the estimated vehicle speed and the wheel speed, it is determined whether the vehicle is in an acceleration state or a deceleration state, and the absolute value of the output of the acceleration sensor is used to estimate the vehicle speed. 1) Method for estimating vehicle speed described in section 1). (3) The vehicle speed estimation method according to item (1), wherein the first set value is 0.2G. (4) The method for estimating vehicle speed according to item (1) or item (2), characterized in that the second setting value is equal to or less than the second setting value of the absolute value of the output of the acceleration sensor. (5) The method for estimating vehicle speed according to item (4), wherein the second set value is set in a range of 0.5 to 0.8G.