JPH07122641B2 - Vehicle speed determination method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a vehicle speed detection method, and more particularly to a method for determining a vehicle speed when wheels of a running vehicle are spun during acceleration or slipped or locked during braking. Is.

Prior Art and Problems In a vehicle with four wheels on the front, rear, left and right,
The vehicle speed is determined based on the rotation speed of the propeller shaft and the like. In such a vehicle, if a difference in rotational speed occurs in the drive wheels, such as a spin during acceleration or a slip or lock during braking, a vehicle speed greatly different from the actual vehicle speed is detected. In such a case, a normal control operation may not be performed in the vehicle that controls the steering angle of the rear wheels, the skid of the wheels, and the like based on the vehicle speed based on the relationship obtained in advance.

On the other hand, as described in Japanese Patent Laid-Open No. 57-147061, when the speeds of three or more kinds of wheels obtained from three or more wheels are not equal to each other, the wheel group with the maximum speed is obtained. A vehicle speed determination method has been proposed in which the vehicle speed is an average value of the speeds of the remaining wheel groups excluding the wheel group having the minimum speed. According to this, when the slip or lock of the wheel is occurring, the speed from the wheel where the slip or lock is occurring can be excluded, so that the vehicle speed is relatively accurately determined.

However, even with such a conventional vehicle speed determination method, there have been cases where sufficient accuracy cannot be obtained. That is, among a plurality of wheel speeds corresponding to each wheel, the vehicle speed is the average value of the speeds of the remaining wheel groups excluding the wheel group having the maximum speed and the wheel group having the minimum speed. In the vehicle speed determination method described in -147061 publication, the maximum value and the minimum value are uniformly removed and the rest is averaged. Therefore, the maximum value, which is the most reliable value during braking, is removed, and at the time of acceleration. In this case as well, the minimum value, which is the most reliable value, is removed, and sufficient accuracy cannot be obtained for the determined vehicle speed value. Further, in a braking operation state in which two or more wheels are slipped or locked, or in an acceleration operation state in which two or more wheels are slipped or spun, for example, the conventional vehicle speed determination method described above causes slippage or the like. The vehicle speed must be the average value of the wheel group speeds including the abnormal value, and sufficient accuracy cannot be obtained.

The present invention has been made in the background of the above circumstances,
It is an object of the invention to provide a vehicle speed determination method capable of obtaining a highly accurate vehicle speed.

Means for Solving the Problems The gist of the present invention for achieving such an object is a vehicle speed determination method for a vehicle having four wheels on the front, rear, left and right, and (i) At least three or more kinds of vehicle speeds are obtained based on the rotational speed of the wheels, and (ii) when there is a speed difference between the three or more kinds of vehicle speeds, slip or lock at the time of braking of the wheels, and acceleration of the wheels. It is determined whether or not the slip or spin at the time, and (iii) when it is determined that the slip or the lock at the time of braking of the wheel, the maximum value of the plurality of types of vehicle speeds,
When it is determined that the wheel is slipping or spinning during acceleration, the minimum value of the vehicle speeds of the plurality of types is determined as the vehicle speed of the vehicle.

By doing so, in the state where the wheel slips or locks occur during braking, the maximum value of the plurality of wheel speeds is determined as the vehicle speed, but the state where the wheel slips or spins occurs during acceleration Then, the minimum value of the wheel speeds of the plurality of types is determined as the vehicle speed. Therefore, an accurate vehicle speed can be obtained even when slips or the like occur on two or more wheels during the braking operation of the vehicle and during the acceleration operation of the vehicle. Since the braking device for a vehicle brakes the rotation of each wheel during its operation, in a braking operation state in which at least one or more wheels are slipped or locked, it is determined based on the rotation speed of each wheel. This is because it is estimated that the vehicle speed is the closest to the largest value among the plurality of types of vehicle speeds. Further, since a plurality of drive wheels are rotationally driven during the acceleration operation of the vehicle, in an acceleration operation state of the vehicle in which at least one or more wheels are slipped or spun, the rotational speed of each wheel is based on the rotational speed. This is because the smallest value of the obtained vehicle speeds of the plurality of types is estimated to be closest to the true vehicle speed.

Here, the lock when the wheel is braked is a state where the wheel is completely stopped by the braking, and the slip when the wheel is braked is the slip and the lock between the wheel and the road surface due to the braking or deceleration operation. The previous state, the spin during acceleration of the wheel, is the state in which the wheel is completely idle, and the slip during acceleration of the wheel, is the state before slipping and spinning between the wheel and the road surface. .

Therefore, according to the present invention, the maximum value of a plurality of types of wheel speeds is determined as the vehicle speed in the state where the wheel slips or locks occur during braking, but the wheel slips or spins are accelerated during acceleration. In such a state, the minimum value of the wheel speeds of the plurality of types is determined as the vehicle speed, so that the accurate vehicle speed can be obtained even if slips or the like occur on two or more wheels. At the same time, the reliability of the rear wheel steering angle control and the skid control based on the vehicle speed thus obtained can be improved.

Embodiment Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

A vehicle 10 shown in FIG. 1 is of a so-called four-wheel steering (4WS) type, and a pair of left and right wheels 12 and 14 that can be steered by a steering wheel (not shown) is provided at a front portion of the vehicle 10. The rear part of the vehicle is also provided with a pair of left and right rear wheels 16 and 18 which are automatically steered in association with the steering of the front wheels 12 and 14. In the present embodiment, the output of the transmission 20 is the output shaft 26, the propeller shaft 22, and the differential gear device.
It is transmitted to the rear wheels 16 and 18 via 24,
A rotation sensor 28 for detecting the rotation speed of the transmission 20 is disposed near the output shaft 26 of the transmission 20.

As shown in FIG. 2, the rotation sensor 28 detects the passage of many teeth formed on the outer peripheral portion of the speed detecting gear 30 fixed to the output shaft 26, and corresponds to the number of passing teeth per unit time. Outputs pulse signal PV _{0 of} frequency. As shown in FIG. 3, the pulse signal PV ₀ from the rotation sensor 28 is sent to the I / O port 36 of the arithmetic unit 34 for sequentially determining the vehicle speed V _n.
Supplied through 4. Further, the vehicle 10 is provided with rotation sensors 60 and 62 for directly detecting the rotational speeds of the left and right front wheels 12 and 14 that rotate freely, and the rotation signals PV ₁ and PV ₁ and PV ₂ is output to the I / O port 36 via the waveform shaper 44.

The arithmetic unit 24 is a so-called microcomputer, and usually also serves as a steering angle control unit for the rear wheels 16 and 18. Arithmetic device 3
4 is a CPU connected to each other via a data bus line,
A ROM, a RAM, etc. are provided, and the CPU processes the input signal according to a program stored in advance in the ROM while utilizing the storage function of the RAM, and calculates the vehicle speed V _n .

On the other hand, the vehicle 10 is provided with a front wheel steering angle detection device 46 for detecting the steering angle of the front wheels 12, 14.
Signal Esuderuta _f representing the steering angle [delta] _f of 12 and 14 is supplied to the I / O port 36 from the front wheel steering angle detecting apparatus 46. Also, vehicle 1
A brake pedal switch 48 for detecting the operation of the brake pedal is provided at 0, and the brake operation signal BR is transmitted from the brake pedal switch 48 to the I / O port 3
Supplied to 6. Further, the engine 50 is provided with an engine rotation sensor 52 for detecting the engine rotation speed and a throttle sensor 54 for detecting the throttle valve opening, and the engine rotation signal SE and the throttle signal TH are Supplied on / O port 36.

Since the CPU stores the actual vehicle speed V _n
And the front wheels of the rear wheels 16 and 18 based on the steering angle δ _f of the front wheels
The steering direction and steering angle with respect to 12 and 14 are determined, and the drive signal DD for operating the rear wheel steering actuator 38 is converted from the I / O port 36 to D / A so that the steering direction and steering angle are obtained. It is supplied to the hydraulic control device 42 through the device 39 and the rear wheel steering amplifier 40. As a result, the control valve provided in the hydraulic control device 42 is operated to supply operating hydraulic pressure to the rear wheel steering actuator 38, and the rear wheel steering actuator 38 changes the steering angles of the rear wheels 16 and 18. .

The operation of this embodiment will be described below with reference to the flow charts of FIGS. 4, 5, 6, and 7.

First, step SS1 is executed to determine whether it is the first cycle. If it is not the first time, step SS3 is executed without passing through step SS2, but if it is the first time, after step SS2 is executed and each counter and flag are cleared, in step SS3 the vehicle speed corresponding to the rotation speed of each wheel Data is calculated. In step SS3,
Based on the pulse signals PV ₀ , PV ₁ and PV ₂ , the vehicle speed v ₀ is calculated according to the following expression (1), and the vehicle dye v ₁ and v ₂ are calculated according to the following expression (2).

v ₀ = f · 2πr / G · H (1) where f is the frequency of the pulse signal PV ₀ , H is the number of teeth of the speed detecting gear 30, G is the gear ratio of the differential gear device, and r is The radius of the wheel.

v _i = f · 2πr / H (2) where f is the frequency of the pulse signal PV _i , H is the number of teeth of the speed detecting gear provided on the wheel, r is the wheel radius, and i is v The subscript is an integer of 1 to 2.

In step SS4, in order to detect the low speed running of the vehicle,
Vehicle speeds v ₀ (n · Δt) and v ₁ (n calculated in step SS3
・ Average value of Δt) and v ₂ (n · Δt) [= (2v ₀ + v ₁ +
v ₂ ) / 4] is a predetermined small constant value V _a , for example
It is judged whether it is larger than 5 km / h. Δt is a vehicle speed calculation cycle, and n is an integer indicating the current cycle. If the determination in step SS4 is negative, the seventh
Steps SS21 and thereafter shown in the figure are executed. That is, in step SS21, the value of the vehicle speed V _n is replaced with V _a , and
In step SS22, the rear wheel steering angle is changed based on this small vehicle speed V _a , and after waiting for time Δt in step SS23, the above-mentioned steps SS3 and thereafter are repeatedly executed. In the step SS22, for example, the relationship stored in advance in the ROM shown in FIG. 8 is used. First, from this relationship, the steering ratios of the rear wheels 16 and 18 with respect to the front wheels 12 and 14 are determined based on the vehicle speed V _n. with coefficient K shown is determined, then the input signal Sδ front wheel steering angle determined based on the _f [delta] _f
And the above coefficient K, the rear wheel steering angle δ is calculated according to the following equation (3).
_r is required. Then, the drive signal DD is supplied to the hydraulic control valve device 42 via the D / A converter 39 and the amplifier 40 so that the rear wheel steering angle δ _r can be obtained.

δ _r = K (V _n ) · δ _f (3) When the determination in step SS4 is affirmative, that is, the vehicle speed v ₀ (n · Δt) is lower than a predetermined constant small value V _a. If so, it is determined in step SS5 whether or not the vehicle is in a cornering state, that is, whether or not the vehicle is turning. This determination is the front wheel steering angle [delta] _f representing the signal Esuderuta _f is performed by whether exceeds a predetermined value [delta] ₀ determined in advance. This constant value δ _{0 is,} for example, the steering angle corresponding to the operation angle of 45 degrees of the steering wheel.
If it is determined in step SS5 that the vehicle is not cornering, the cornering flag Fc is reset in step SS6, and step SS7
Is executed and it is determined whether or not there is a slip or a spin during acceleration of the wheels. The slip or spin during acceleration of the wheels is the rotational acceleration of the rear wheels (driving wheels), that is, the difference between the vehicle speed obtained in this cycle and the vehicle speed obtained in the previous cycle and the previous cycle [v ₀ (n · Δt)- v ₀ {(n-
1) · Δt}] is larger than a predetermined constant value α ₀ . This value α ₀ is determined to be a rotational acceleration equal to or less than the maximum rotational acceleration in the range where the wheel and the road surface do not slip. Above slip SS7
When the slip or spin during acceleration of the wheel is not detected in step S8, step SS8 is executed to determine whether or not slip or lock during braking of the wheel is present. This judgment is based on the signal PV ₀ and the rotational acceleration [2v ₀ {(n-1) · Δ
t} −2v ₀ (n · Δt)], rotational acceleration based on the signal PV ₁ [v ₁ {(n−1) · Δt} −v ₁ (n · Δt)], signal PV
₂ based rotational acceleration [v ₂ {(n-1) · Δt} -v
₂ (n · Δt)] average value β is a predetermined constant value β
It is judged to be greater than _zero . This value β ₀ is determined to be a rotational acceleration equal to or higher than the minimum rotational acceleration in the range where the wheel and the road surface do not slip.

When slips or locks during wheel braking and slips or spins during acceleration are not detected in steps SS7 and SS8, step SS9 is executed and three types of vehicle speed data v ₀ (calculated in this cycle) n · Δt), v ₁ (n · Δt), v ₂ (n · Δt)
The intermediate value of is adopted as the provisional vehicle speed V _n ′. And
The three types of vehicle speed data are compared with each other, and one vehicle speed is judged to be an abnormal vehicle speed detection when it exceeds a tentative vehicle speed V _n ′, in other words, a predetermined constant ratio from the intermediate value of each vehicle speed. To be done. That is, after 1 is subtracted from the content of the register i in step SS10 shown in FIG. 6 and 1 is added to the content of the register i in step SS11,
Step SS12 is executed to judge whether the content of the register i reaches 3. Since it does not arrive at the beginning, step SS13 is executed to determine whether the vehicle speed detection is in an abnormal state.

The following equation (4) is used for this determination. However, r is 0.1
A value of (10%) is used.

| v _i −V _n ′ |> γ (4) Since the content of the register i is 0 at the beginning, v ₀ is used for the determination in step SS13. If this determination is negative, the flag F _Tb is reset in step SS14, then step SS11 is executed again and 1 is added to the content of the register i, and this time v ₁ is determined in the determination in step SS13.
Is used. If this judgment is denied, the contents of the register i is set to 2 as in the above, and v ₂ is used for the judgment in step SS13. In this way, when it is determined that the variation of the vehicle speed data with respect to the intermediate value is within a certain range, the content of the register i is set to 3 in step SS11, the determination in step SS12 is affirmative, and the register i is registered in step SS15. After 1 is subtracted from the content of i, step SS16 shown in FIG. 7 is executed.

In step SS16, the vehicle speed detection is abnormal, that is, the rotation sensor
Whether or not the flag F _Ta that indicates an abnormality such as 28 failure, speed detection gear 30 chipping, etc. is 1, that is, flag F _Ta
It is determined whether _Ta is set. If the vehicle speed detection is not abnormal, step SS17 is executed to determine the vehicle speed V _n . This vehicle speed V _n is determined by the provisional vehicle speed V _n ′ and the value obtained by adding the maximum vehicle speed change value αmax · Δt to the previous vehicle speed V _n−1 .
It is executed by selecting an intermediate value from three types of values consisting of the previous vehicle speed V _n-1 and the value obtained by adding the minimum change value α min · Δt of the vehicle speed, and the vehicle speed V _n is updated to a new selected value. .
The αmax and αmin are the maximum acceleration and the minimum acceleration of the vehicle in the range where the wheel and the road surface do not slip, and the maximum change value and the minimum change value of the vehicle speed are the time Δt in the state where the wheel and the road surface do not slip. It is the maximum change width and the minimum change width of the vehicle speed. As a result, even if the vehicle speed v ₀ (n · Δt) of an abnormally large value or an abnormally small value is input due to a failure of the rotation sensor 28 or the like, the vehicle speed V _n
Is limited to the maximum value or the minimum value that can actually be present, so that the abnormal operation of the control performed based on the vehicle speed V _n is prevented.

Then, by executing step SS18, the vehicle speed
V _n is is equal to or the same as the temporary vehicle speed V _n 'previously determined it is determined. If they are the same, it means a normal condition.
Step SS20 is executed to determine whether the vehicle speed V _n is lower than the V _a . If the determination is affirmative, the above-mentioned steps SS21 and below are executed, but if the determination is negative, the steps SS22 and below are executed, so that the rear wheels based on the vehicle speed V _n determined in step SS17. The steering angle of is determined.

However, in step SS18, if it is determined that the vehicle speed V _n determined in step SS17 is not the same as the temporary vehicle speed V _n ′ determined in step SS9, it is an abnormal state of vehicle speed detection, and therefore step SS19. Is executed and the vehicle speed V _n is limited. That is, the maximum vehicle speed (= V _n-1 + αmax · Δt), the minimum vehicle speed (= V _n-1 + αmin · Δt), and [V _n-1 + min _* (Δv ₀ , Δv)
₁ , Δv ₂ )] and the intermediate value is selected. This min
_* (Δv ₀ , Δv ₁ , Δv ₂ ) is the variation of each vehicle speed Δv ₀ , Δv ₁ , Δv ₂
Among the values of, the remaining minimum value is shown except for the one determined to be abnormal from the equation (4) in step SS13.

If the determination in step SS13 is positive,
Whether step SS24 is executed to add 1 to the coefficient content of the timer counter T ₂ and step SS25 is executed to determine whether or not the content of the timer counter T ₂ has reached a preset constant value T _b. To be judged. This constant value T _b is a value corresponding to 10 seconds, for example. Even if the abnormal value of car dyeing detection is determined in step SS13, the determination in step SS25 is denied while it does not continue for 10 seconds, so that step SS11 and subsequent steps are executed as in the normal case. If it continues for 10 seconds, the determination in step SS25 is affirmative, so step SS26 is executed and the flag F _Tb is set, and then it continued for 20 seconds after the abnormal value of vehicle speed detection is determined in step SS27. It is determined whether or not. If it does not continue for 20 seconds, the flag F _Ta is set in step SS28, and then step SS11 and the subsequent steps are executed as in the normal state. However, in this case, step SS as described above.
The vehicle speed V _n is determined in a state where the abnormal value is removed by executing 19 and the control of the rear wheel steering angle is executed at this vehicle speed V _n .

If the determination in step SS27 is affirmative, it is determined that the vehicle speed detection abnormality such as breakage of the rotation sensor occurs because the vehicle speed detection abnormality value has been maintained for 20 seconds after the determination. Therefore, step SS29 is executed, an alarm display indicating an abnormality in vehicle speed detection is displayed on a display (not shown), and the flag F _Ta indicating the abnormality is set.

In that case, since the determination in step SS16 is affirmative, step SS30 is executed to determine whether or not the vehicle 10 is cornering based on the cornering flag Fc. If the vehicle 10 is not cornering,
In step SS31, the vehicle speed V _n is replaced with a predetermined constant vehicle speed V ₀ . This constant vehicle speed V ₀ is, for example, 100 km / h
By doing so, the abnormal operation of the rear wheel steering angle control when the vehicle speed detection is abnormal is prevented. However, after the cornering flag Fc is set in step SS40 described later, the determination in step SS30 is affirmative, so step SS32 is executed to set the vehicle speed V _n to the vehicle speed V _n-1 adopted in the previous cycle. Fix it. That is, the update of the vehicle speed V _n is blocked. As a result, when the vehicle speed detection is abnormal, the change of the vehicle speed V _n used for the rear wheel steering angle control is prevented during the turning of the vehicle, and the rear wheel steering angle change contrary to the driver's intention is eliminated.

If a step or spin during wheel acceleration is detected in step SS7, step SS33 is executed to determine the provisional vehicle speed V _n ′ from the following equation (5), and then steps SS17 and thereafter are executed. To be done. In this way, by setting the provisional vehicle speed V _n ′ to the minimum value excluding abnormal values,
The vehicle speed is set to be close to the actual vehicle speed under a condition in which the wheel is likely to be detected high due to slip or spin during acceleration of the wheels. If a wheel slips or spins during acceleration,
Among the multiple types of vehicle speed calculated for each wheel, there is no slip or spin, or the degree of slip is small.The vehicle speed based on the rotation speed of the wheel is the closest to the actual vehicle speed. by adopting the minimum value among the plurality of types of vehicle speed which is a provisional vehicle speed V _n 'can be determined relatively accurate vehicle speed even rotation abnormality of such wheel.

V _n ′ = min _* [(v ₁ + v ₂ ) / 2, v ₀ ] ... (5) where min _* is the minimum value after removing the abnormal value from the value in []. .

If a step or lock during wheel braking is detected in step SS8, step SS34 is executed to determine the provisional vehicle speed V _n ′ from the following equation (6), and then in step SS35 the wheel braking is performed again. Time slip or lock is determined. In this way, the provisional vehicle speed V _n ′ is set to the maximum value excluding the abnormal value, so that the vehicle speed is approximated to the actual vehicle speed under a condition in which the vehicle speed V _n ′ is easily detected due to slip or lock during braking of the wheels. When a wheel slips or locks during braking, the speed of the wheel that has not slipped or locked or has a small degree of slip among the multiple vehicle speeds corresponding to the rotation speed of each wheel. Since it is the closest to the vehicle speed based on the actual vehicle speed or the actual vehicle speed, if the maximum value of the obtained vehicle speeds of multiple types is adopted as the temporary vehicle speed V _n ′, even if such wheel rotation abnormality occurs, it is relatively accurate. The vehicle speed can be determined.

V _n ′ = max _* [(v ₁ + v ₂ ) / 2, v ₀ ] ... (6) However, it shows the maximum value after removing the abnormal value from the value in max _* [] above. .

Different from the case of step SS8, the determination in step SS35 is made based on whether or not the adopted rate of change in temporary vehicle speed (V _n ′ −V _n−1 ) exceeds a predetermined constant value β ₀ . This determination is determined that a slip or lock during braking If an affirmative real wheel, the step SS22 following is performed after the lock flag F _L is set in step SS36. However, if the determination in step SS35 is negative, the content of the cornering flag Fc is determined in step SS37. The contents of the lock flag F _L is determined in step SS38, if a cornering of the vehicle 10, but the step SS17 below is executed when not in the slip and wheel lock, in a slip or lock of the wheel lock flag F _L is set in step SS36 in some cases. Further, when the determination in step SS37 is negative, in step SS39 is executed lock flag F _L is after being reset, the step SS17 below is executed.

As described above, even when the determination in step SS35 is denied, that is, even when the slip or lock at the time of braking the wheels is eliminated, the lock flag is set during the cornering of the vehicle 10.
Since F _L is not reset, the vehicle speed V _n is determined in the same manner as during slipping or locking, and the rear wheel steering angle is controlled based on this. Therefore, during cornering of the vehicle 10, the vehicle speed V _n is fixed to the value V _n-1 in the previous cycle as in the case where the vehicle speed detection is abnormal, and the change of the rear wheel steering angle against the driver's intention is prevented. Has been done.

When it is determined that the vehicle 10 is cornering in step SS5, the cornering flag Fc is set by executing step SS40, and step SS41 similar to step SS7 is executed to change the wheels. The slip or spin during acceleration is determined, and step SS42 similar to step SS8 is executed to determine the slip or lock during braking of the wheels. If neither slipping or spinning during acceleration of the wheels nor slipping or locking during braking of the wheels occurs, the temporary vehicle speed V _n ′ is determined according to the following equation (7) in step SS43, and then the above-mentioned step SS17. The following is done:

V _n ′ = [v ₀ + (v ₁ + v ₂ ) / 2] / 2 (7) As is apparent from the above equation, in step SS43, the average value of each vehicle speed data is obtained as the temporary vehicle speed. But,
When it is determined that the wheel is slipping or spinning during acceleration, step SS44 is executed to obtain the provisional vehicle speed V _n ′ according to the same formula as in step SS33, and then step SS17 and thereafter are executed. Further, if it is determined that the wheel slips or locks during braking, step SS45 is executed, and after the provisional vehicle speed V _n ′ is obtained according to the same equation as in step SS34, the steps SS35 and thereafter are executed. It

As described above, according to the present embodiment, when slips or locks occur during braking of the wheels while the vehicle 10 is traveling, a plurality of types of vehicle speeds obtained [(v ₁ + v ₂ ) / 2, v The maximum value of ₀ ] is determined as the temporary vehicle speed V _n ′, that is, the vehicle speed V _n after the limiter processing in step SS17, so that the vehicle speed close to the actual vehicle speed can be obtained. Further, when slipping or spinning occurs during acceleration of the wheels while the vehicle 10 is traveling, the minimum value of the vehicle speeds obtained from a plurality of types is the temporary vehicle speed V _n ′, that is, the vehicle speed after the limiter processing of step SS17. Since it is determined as V _n , the vehicle speed that is close to the actual vehicle speed can be obtained. Therefore, a relatively accurate vehicle speed can be obtained even if the rotational speed difference between the wheels occurs, so that the normal control operation of the rear wheel steering angle control can be maintained. Such an effect can be similarly obtained when the vehicle controls the skid or the like of the wheels based on the vehicle speed based on the relationship obtained in advance.

Although the vehicle 10 of the present embodiment is a rear wheel drive system, the present invention is also applicable to a front wheel drive system. In this case, rotation sensors 60 and 62 are provided to detect the rotation speed of the rear wheels 16 and 18.

Next, another embodiment of the present invention will be described. The same parts as those in the above-described embodiment are designated by the same reference numerals and the description thereof will be omitted.

In the present embodiment, as shown in FIG. 9 and FIG. 10, the vehicle 10 is replaced with the left and right rear wheels 1 instead of the rotation sensor 28.
Rotation sensor 6 for detecting the rotation speed of 6 and 18 respectively
4 and 66 are further provided, which are rotation sensors 64
And 66 provide signals PV ₃ and PV ₄ to I / O port 36.

In the arithmetic unit 34 of the present embodiment, FIG. 11, FIG. 12, FIG.
And the vehicle speed V _n according to the flowchart shown in FIG.
Is determined, and the rear wheel steering angle is controlled at the vehicle speed V _n . The step structure of the flow chart of this embodiment is similar to that of the flow chart shown in FIGS.
Since only some of the steps are different, the different steps will be described below.

In step ST3, vehicle speed data v ₁ (n · Δt), v ₂ (n · Δt), v ₃ corresponding to the signals PV ₁ , PV ₂ , PV ₃ and PV ₄
(NΔt) and v ₄ (nΔt) are the values in step SS
Each is calculated in the same manner as in the case of 3, and in step ST4 for detecting the low speed running of the vehicle, the calculated average value (= 1 / 4Σv _i ) of each vehicle speed is calculated from a predetermined constant value V _a . Is also large.

The determination of slip or spin during acceleration of the wheels in steps ST7 and ST41 is performed by determining the driving wheels (wheel 1 in this embodiment).
Change rate of average vehicle speed b of vehicle speeds v ₃ and v ₄ [= b (n · Δt) −b {(n−1) · Δ)
t}, where b = 1/2 (v ₃ + v ₄ )] exceeds a predetermined constant value α ₀ . If the vehicle is of the front-wheel drive type, the rate of change of the average vehicle speed a of the vehicle speeds v ₁ and v ₂ [= a (n · Δt) −a {(n−1) · Δ
t}, where a = 1/2 (v ₁ + v ₂ )] exceeds a predetermined constant value α ₀ . If the vehicle is a four-wheel drive system, the rate of change of the average vehicle speed of four types of vehicle speeds v _i [= 1/4 · Σv _i (n · Δt−1 / 4 · Σv _i {(n−
1) · Δt}, where i is a subscript and is an integer of 1 to 4]
Is exceeded when a predetermined constant value α ₀ is exceeded.

Further, in steps ST8 and ST42, determination of slip or lock during braking of the wheels is made by changing rate of average value of four kinds of vehicle speeds v _i [= 1/4 · Σv _i (n · Δt) -1 / 4 · Σv _i {(n-
1) .Δt}] exceeds a predetermined constant value β ₀ .

The provisional vehicle speed V _n ′ is determined as follows. First, the vehicle
When 10 is traveling straight and the wheels are rotating normally, as shown in step ST9, four calculated vehicle speeds v _i , that is, v ₁ , v ₂ , v ₃ , and v ₄ The average of the two intermediate values is used. If the vehicle 10 is traveling straight ahead and the wheels are accelerating in a slip or spin condition,
As shown in ST33, take the minimum value of the four vehicle speeds v ₁ , v ₂ , v ₃ , and v ₄ excluding the abnormal values. Further, in the slip or locked state when the vehicle 10 is traveling straight and braking the wheels, as shown in step ST34,
The maximum of the _four vehicle speeds v ₁ , v ₂ , v ₃ , and v ₄ excluding the abnormal values is taken. However, when the vehicle 10 is cornering and the wheels are normally rotating, as shown in step ST43, the vehicle turns left (δ _f <0).
Then, vehicle speed e [= 1/2 (v ₁ + v ₄ )], vehicle speed e ′ [= f × v
₁ / v ₂ , where f = 1/2 (v ₂ + v ₃ )], vehicle speed e ″ [= f × v ₃ /
v ₄ ] excluding outliers, the first one in the above order is prioritized. However, turning to the right (δ _f <
0), vehicle speed f [= 1/2 (v ₂ + v ₃ )], vehicle speed f ′ [=
e × v ₂ / v _1,], the vehicle speed f "[= e × v ₄ / v _3] of but excluding the outliers take the first of the above sequence preferentially.
Further, when the vehicle 10 is cornering and the wheel is in a slip or spin state when accelerating, as shown in step ST44, the minimum value of the above values e, f, a, and b excluding the abnormal value. Is taken. When the vehicle 10 is cornering and the wheel is in a slipping or locked state during braking, as shown in step ST45, the value e,
The maximum value of f, a, and b excluding the abnormal value is taken.

After the provisional vehicle speed V _n ′ is determined in step ST9,
Step ST10 is executed to clear the contents of register i to 0, and step ST11 is executed to add 1 to the contents of register i. And step ST12
At, it is determined whether the content of register i has reached 4. Since it does not reach the initial stage, step ST13 is executed, and step ST13 similar to step SS13 is executed to determine whether the vehicle speed v ₁ exceeds a predetermined ratio with respect to the temporary vehicle speed V _n ′. Since the detection is abnormal, it is judged sequentially. Then, through steps ST14, ST11 and ST12, the next vehicle speed v ₂ is judged again. When the determination of each vehicle speed v _i is completed, the content of the register i reaches 4, so that steps ST15 and thereafter are executed. However, if it is determined that the vehicle speed detection is abnormal in step ST13, it is determined in step ST27 whether the duration exceeds 20 seconds, as in the above embodiment, and if it exceeds, the abnormal value is dealt with. Flag as a failure of the rotation sensor etc.
While setting F _Ta , the same measures as in the above-described embodiment are taken.

As described above, also in the present embodiment, when slips or locks occur during braking of the wheels while the vehicle 10 is traveling, a plurality of types of vehicle speed data (v ₁ , v ₂ , v ₃ , v ₄ ,
Alternatively, the maximum value of e, f, a, b) is determined as the vehicle speed V _n ′, that is, the vehicle speed V _n after the limiter processing in step ST17, so that the vehicle speed that is close to the actual vehicle speed is obtained.
Further, when slipping or spinning occurs during acceleration of the wheels while the vehicle 10 is traveling, the minimum value of the vehicle speeds obtained from a plurality of types is the temporary vehicle speed V _n ′, that is, step ST.
After the limiter process of 17 is determined as the vehicle speed V _n ,
A vehicle speed that is close to the actual vehicle speed is obtained. Therefore,
Since a relatively accurate vehicle speed can be obtained even if the rotational speed difference between the wheels occurs, the normal control operation of the rear wheel steering angle control can be maintained. Such an effect can be similarly obtained when the vehicle controls the skid or the like of the wheels based on the vehicle speed based on the relationship obtained in advance.

The above description is merely one embodiment of the present invention, and the present invention can be variously modified without departing from the spirit thereof.

[Brief description of drawings]

FIG. 1 is a diagram for explaining a main part of a vehicle to which the present invention is applied. FIG. 2 is a view showing a mounting portion of a rotation sensor provided in the vehicle shown in FIG. FIG. 3 is a diagram showing a configuration of an electronic control circuit provided in the vehicle shown in FIG. Fourth
FIG. 5, FIG. 6, FIG. 6, and FIG. 7 are flowcharts for explaining the operation of the electronic control circuit of FIG. FIG. 8 shows a third embodiment for controlling the steering angle of the rear wheels of the vehicle shown in FIG.
It is a figure which shows the relationship stored beforehand in the electronic control circuit of the figure. 9 and 10 are views corresponding to FIGS. 1 and 3 in another embodiment of the present invention. Figure 11,
FIG. 12, FIG. 13, and FIG. 14 are flowcharts for explaining the operation of the embodiment shown in FIG. 9 and FIG. 10: Vehicle 12, 14: Wheel (front wheel) 16, 18: Wheel (rear wheel)

Claims (1)

[Claims] 1. A method for determining a vehicle speed of a vehicle having four wheels in front, rear, left and right, wherein at least three or more kinds of vehicle speeds are obtained based on rotation speeds of the four wheels. When there is a speed difference between the above vehicle speeds, it is determined whether the slip or lock occurs when the wheel is braked and whether the slip or spin occurs when the wheel is accelerated. If it is determined, the maximum value of the vehicle speeds of the plurality of types is determined, and if it is determined to be the slip or spin when the wheels are accelerated, the minimum value of the vehicle speeds of the plurality of types is determined as the vehicle speed of the vehicle. A vehicle speed determination method characterized by: