JP2587762Y2 - Wheel speed measurement device - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to wheel speed measurement of a vehicle, and more particularly to a wheel speed measurement device capable of measuring wheel speed with high accuracy even at a sudden stop and at a low speed.

[0002]

2. Description of the Related Art As a method of measuring a wheel speed, for example, a wheel speed sensor that outputs a speed pulse each time the wheel rotates a predetermined amount is attached to the wheel, and the count value of a self-propelled counter that counts a clock of a period τ is calculated by: Synchronized with the output speed pulse of the wheel speed sensor in which the cycle of the pulse train changes according to the wheel speed, the cycle T (= τm) of the wheel speed pulse is obtained from the count difference m from the previous count value. The distance K traveled during the constant rotation is divided by the cycle T to obtain the wheel speed Vw (= K /
A method of obtaining the value as T) is known. Incidentally, when a speed pulse is output each time the wheel makes one rotation, the distance K is a value obtained by multiplying the outer diameter D of the wheel by the pi (π).
D). Accordingly, the wheel speed Vw in this case is Vw = πD / τm, and if the constant πD / τ is set to k, Vw = k / m.

However, in the above-described wheel speed measurement method, the count value of the self-propelled counter is increased several times while the speed pulse and the next speed pulse are obtained, such as during low-speed running or sudden braking, and the upper limit count value is increased. In such a case, there is a problem that sufficient counting accuracy cannot be obtained. Therefore, an improvement of the above technology is disclosed in, for example,
Is described in 96467 JP, this is an overflow flag that is generated when the count value of the self-propelled counter for counting the clock pulses reaches the full count (upper count), while counting overflow flag counter The normal wheel speed calculation is performed, and the overflow flag counter is reset every time the normal wheel speed calculation is performed. When the overflow flag counter value becomes 2 or more, the calculated value is set to a fixed value. That is, when the wheel speed is lower than a certain speed, the wheel speed is fixed to the minimum speed. Therefore, for example, the temporal change of the wheel speed output at the time of sudden braking, as shown by the dotted line in FIG. The speed suddenly drops to zero.

[0004]

The present invention is to provide a above-mentioned JP-A-59-19
In the prior art described in Japanese Patent No. 6467, a certain time is required until the value of the overflow flag counter becomes 2 before the judgment of the sudden stop and the sudden deceleration is performed, and during this time, the wheel speed calculation is performed at all. Therefore, the responsiveness to the wheel speed calculation at the time of sudden stop and sudden deceleration deteriorates.
In addition, if two or more overflow flags are raised before one wheel speed calculation is completed, the wheel speed is fixed to zero, so that such a method may not be able to perform the calculation with low accuracy or responsiveness. It was clear.

Further, Japanese Patent Application Laid-Open No. 64-26165 describes this.
In the "speed detection device" described above, when the pulse signal generation interval becomes longer during low-speed running, the output of the second counter (overflow counter) increases the frequency division ratio of the count clock of the first counter. The switching and the measurable range in the low-speed rotation range are expanded. However, in addition to the first and second two counters, an encoder and a data selector for switching the dividing ratio are required. The configuration is very complicated and the production cost is high.

On the other hand, when the pulse signal generation interval becomes longer during low-speed running and the next pulse signal is not input forever, the wheel speed calculation is executed at a predetermined calculation timing to measure the wheel speed finely. A method and a device therefor have also been proposed.

For example, Japanese Unexamined Patent Publication No. 63-221251 discloses that the wheel speed calculation is performed at both edges without sticking to one edge of the output pulse signal of the wheel speed sensor, so that the sensor output at the time of sensor output disappearance is obtained. A method for improving the response of the virtual operation is disclosed . In this method, the previous operation timing (T _CLn ) is used.
And the reference timing (T _CLn )
The time difference (ΔTn) between each calculation timing and the virtual performance
And the margin time (To ') that determines the calculation timing
Even if the reference elapsed time (ΔTn + To ') has passed,
Virtual operation starts when no sensor signal is output
(From page 14, lower left column, line 14 to last line,
(See the timing chart in FIG. 1). Therefore virtual operation
Is the variable corresponding to the previous wheel speed.
Becomes floating based on the time difference (ΔTn).
Therefore, in a high speed range where the time difference (ΔTn) is relatively short,
The reference elapsed time (ΔTn + To ′) is lower than that in the low speed range.
The conditions for entering virtual operations became relatively short,
As a result, the count value of the self-propelled counter overflows.
No original fear of over (hence without relying on virtual computing
Is also calculated by the normal calculation based on the output count value of the sensor signal.
Is the speed range in which the wheel speed can be measured accurately)
Regardless, it entered useless virtual calculation, and that much wheel
There is a possibility that the calculation accuracy of the speed may decrease.

Further, Japanese Patent Application Laid-Open No. 63-238563, “FV
The conversion method ", when the interval of the pulse input is not performed exceeds the reference elapsed time, the method which is adapted to convert the pulse count at that time for each the reference elapsed time measured value is disclosed However, even with this method, the previous (n-th)
Between the pulse and the (n-1) th pulse before
Because the tarball time is the reference elapsed time,
There is the same problem as in JP-A-63-221251. Further
In this device, the conversion of the pulse count value to the measured value is performed by an arithmetic operation on the total accumulated value of the pulse count value until the predetermined time comes, and the total accumulated value becomes closer to a very low speed range. In order to be bulky, the operation of converting the count value into the measured value by division with a value of several tens of times the normal measurement area as a numerator is a calculation for imagining the measured value, but large-scale division is required. Therefore, there is a problem that the load on the arithmetic software increases.

Further, when it is found that the measurement cycle is longer than the previous time, the actual vehicle count is output without waiting for the measurement of the cycle when the actual vehicle speed detection apparatus is disclosed in Japanese Utility Model Laid-Open No. 63-50064. gradually brought close to the current period measurement values from the previous cycle measuring values, and device which can correspond to reducing the change in the vehicle speed is disclosed, also the ones, opens the virtual operation
The reference elapsed time as the starting condition
Is determined based on the time difference of the
This is also the same as in JP-A-63-221251.
There's a problem. Further, in this device, when it is found that the measurement cycle is longer than the previous cycle, the count value output without waiting for the cycle measurement is the count value accumulated from the previous cycle measurement time. This count value itself becomes bulky as it approaches, and the count value must be converted to speed by division with a value of several tens times the normal speed range as a numerator,
Since a large-scale division is required in spite of the virtual speed calculation, there is a problem that the load on the calculation software increases.

Therefore, an object of the present invention is to improve the responsiveness of the wheel speed calculation in a low speed range in which the self-propelled counter overflows due to a sudden stop or a sudden deceleration, and to provide high accuracy from a low speed to a high speed. This is for calculating a wheel speed calculation value.

[0011]

SUMMARY OF THE INVENTION The present invention provides a wheel speed sensor for outputting a speed pulse each time a wheel rotates a fixed amount, and a self-propelled counter for cyclically counting a clock of a predetermined period from a zero value to a limit value. And the counter value overflows
In the normal speed range where the wheel speed sensor does not go low, the count output of the self-propelled counter is taken in synchronization with the speed pulse output by the wheel speed sensor, and a value obtained by multiplying the count difference from the previously taken count output by the predetermined period. A wheel speed calculator that converts the distance traveled while the wheel rotates by the predetermined amount into a wheel speed.
And a wheel speed calculating means for controlling the wheel speed.
In the low-speed range where the count value of the data counter overflows, an interrupt is issued with an interrupt cycle shorter than the cycle of the speed pulse, and each time an interrupt is made until the next speed pulse is obtained, the self-propelled counter is interrupted. The count output is taken in, and the wheel speed conversion value Vwb of the count integrated value of the self-propelled counter up to the last interrupt is stored and stored.
The wheel speed Vw is calculated as 1 / {(1 / Vwb) + (1 / Vwn)} from the calculated wheel speed converted value Vwb and the wheel speed converted value Vwn of the count difference from the previous interrupt to the current interrupt. and wherein and Turkey sought.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a diagram showing the configuration of an embodiment of the present invention, FIG. 2 is an explanatory diagram showing a comparison between the present invention and the conventional technology, FIG. 3 is a state diagram of a pulse signal and a counter value in a normal speed range, and FIG. FIG. 5 is a state diagram of a pulse signal and a counter value in a low speed range, and FIG. 5 is a flowchart showing an operation of one embodiment of the present invention.

In FIG. 3, the wheel speed Vw in the normal speed range is shown.
Is calculated, the count difference m between the count value of the self-propelled counter when the speed pulse is input from the wheel speed sensor 1 and the count value of the self-propelled counter when the previous speed pulse is input is Ask for. The period T of the speed pulse during this period is
When the clock cycle of the self-running counter is τ, T =
τm, the distance K traveled while the wheel rotates a fixed amount
Is divided by the period T to obtain Vw = K / τm. That is, the count difference m is converted into the wheel speed Vw by dividing the distance K traveled while the wheel rotates by the predetermined amount by a value obtained by multiplying the count difference m from the previously taken count output by the clock cycle τ. . Note that K / τ is a constant k
Therefore, the wheel speed Vw is calculated as Vw = k / m.

However, as shown in FIG. 4, since the number of count bits of the self-propelled counter is finite and the upper limit count value is also finite, if the wheel speed falls below the normal speed range, Not only does the count value of the self-propelled counter overflow, but also because the next wheel speed pulse is not input for a long time, the wheel speed calculation is not executed, and especially whether the wheel stops rotating or not In the ultra-low speed range, the wheel speed could not be calculated.

FIG. 1 shows the configuration of an embodiment for solving this problem.

In FIG. 1, the output signal of the wheel speed sensor 1 is input to a self-propelled counter 4 after being shaped into a pulse waveform by a waveform shaping means 2. The self-propelled counter 4 is connected to flag setting means 6 for setting a flag (hereinafter referred to as an overflow change flag) for monitoring a change in the overflow of the count value. 7 is connected to determine the overflow change flag set by the flag setting means 6 and output the determination result to the wheel speed calculating means 5 which calculates the wheel speed from the output of the self-propelled counter 4. The wheel speed calculating means 5 outputs the final wheel speed based on the output of the counter 4 and the result of the flag determining means 7.

Next, the operation of the present invention will be described with reference to the flowchart of FIG.

Here, the overflow change flag is set when an overflow occurs, and is reset when a normal wheel speed calculation is performed. Therefore, the overflow change flag remains set during the operation in the low speed range below the normal speed range described below.

In FIG. 5, it is first determined whether or not an overflow change flag is set (step 1).
01). When the overflow change flag is set, it can be said that the wheel is rotating at a low speed and the interrupt cycle is shorter than the cycle of the speed pulse. Therefore, when the first interrupt occurs,
The wheel speed conversion value Vwn of the count value from the previous calculation to the present is read, and the current wheel speed Vw is calculated using the previous wheel speed conversion value Vwb (step 102).

That is, in the low speed range less than the normal speed range, an interrupt is generated with an interrupt cycle shorter than the cycle of the speed pulse. The count output of the running counter is taken in, and the wheel speed Vw is calculated as K / τΣm from the count integrated value Σm and the distance K from the count output taken in synchronization with the immediately preceding speed pulse. Specifically, assuming that the count integrated value of the self-propelled counter up to the previous interrupt is M, and the count difference from the previous interrupt to the current interrupt is n, the wheel corresponding to the count difference n Since the speed conversion value is Vwn and the wheel speed conversion value at the time of the previous interrupt is Vwb, the following expression is obtained: Σm = M + n Vwn = k / n Vwb = k / M, and the wheel speed Vw is eventually Is calculated as

On the other hand, if the overflow change flag has not been set, it is determined whether an overflow has occurred (103). If an overflow has occurred, it is known that the overflow change flag has not been set in the immediately preceding step (101), so it is considered that the first overflow has occurred. Therefore, the wheel speed Vw reads the count value m from the previous calculation to the present, and becomes Vw = k / m (step 1).
04). This wheel speed Vw is stored and used for the next calculation.

If the overflow change flag is not set and no overflow occurs, the overflow change flag is reset (step 10).
5). In this case, the expression of resetting the overflow change flag in step 101 merely assumes that the overflow change flag is not set in the first place. It should be interpreted as meaning.

FIG. 2 shows the wheel speed measurement results in the low speed range.
It can be seen from this figure that the accuracy of the wheel speed measurement at the time of low speed or sudden stop is greatly improved. That is, according to the wheel speed measuring device of the present invention, even if the count value of the self-propelled counter overflows and the next wheel speed pulse is not input for a long time, the wheel speed calculation is performed with the interrupt period. Is executed, for example, when traveling at an extremely low speed of stopping or not stopping, for example, from 2 km / h per hour, 1.0 (= 1 / ｛1/2 + 1 /
2｝), 0.67 (= 1 / {1 / + 1 +｝}), 0.
5 (= 1 / {3/2 + 1/2}). . . As in the case of Km / h, the wheel speed gradually decreases in each interruption cycle, and the wheel speed can be finely measured. In this case, the wheel speed calculation executed at the interrupt cycle is based on the wheel speed conversion value Vwb of the count integrated value of the self-propelled counter up to the previous interrupt and the wheel difference of the count difference from the previous interrupt to the current interrupt. Since the calculation is performed based on the speed conversion value Vwn, a substantial change in the arithmetic expression is the wheel speed conversion value Vwn of the count difference from the previous interrupt to the current interrupt, and is necessary for the conversion. Since the division scale is small, the load on the calculation software can be reduced.

[0024]

[Effects of the Invention] As described above, according to the present invention,
Cyclic counting of a clock of a predetermined period from zero value to the limit value
The self-propelled counter does not overflow (immediate
Value In the Chi does not reach the limit value) normal speed range, which takes in the count output of the counter in synchronism with the speed pulse wheel speed sensor outputs, and the count difference from the count output taken last predetermined period doubling The distance traveled while the wheel rotates a certain amount is converted to the wheel speed by
In the overflowed (ie, when the limit value is reached) low speed range, an interrupt is generated with an interrupt cycle shorter than the cycle of the speed pulse, and the count of the counter for each interrupt performed until the next speed pulse is obtained. The output is fetched, and the wheel speed conversion value Vwb of the count integration value of the counter up to the previous interrupt and the wheel speed conversion value Vwn of the count difference from the previous interrupt to the current interrupt are obtained.
Since w is calculated as 1 / {(1 / Vwb) + (1 / Vwn)}, the wheel may suddenly decelerate or stop.
Count value of self-propelled counter due to wheel speed decrease in the process
Overflowed (ie, the limit was reached)
Then, even if the situation where the next wheel speed pulse is not input for a long time continues, the virtual calculation of the wheel speed can be executed with a relatively short interrupt cycle. From 2 km / h to 1.0
(= 1 / {1/2 + 1/2}), 0.67 (= 1 / {1
/ 1/2 + 1/2), 0.5 (= 1 / {3/2 + 1 /
2｝). . . The wheel speed is gradually reduced at every interruption cycle, such as Km / h, so that the wheel speed can be finely imagined even in an extremely low speed range where the wheel stops rotating or not.
Can be calculated. Moreover, the execution of such virtual operations
In this case, the count value of the self-propelled counter
(That is, the limit has been reached)
That virtual operation is
Execute accurately only during the counter overflow period
And the counter overflows
Until the last minute, normal calculation based on wheel speed pulse is accurate
As a result, responsiveness and detection accuracy when measuring wheel speed during sudden deceleration or sudden stop can be effectively increased , and all speeds from low speed to high speed
The accuracy of measuring the wheel speed can be improved over the range .
In addition, the wheel speed calculation executed with the above-mentioned interrupt cycle is based on the wheel speed conversion value Vwb of the count integrated value of the self-propelled counter up to the previous interrupt and the wheel speed of the count difference from the previous interrupt to the current interrupt. Since the calculation is performed based on the converted value Vwn, the actual change in the arithmetic expression is the wheel speed converted value Vwn of the count difference from the previous interrupt to the current interrupt, and the division required for the conversion is calculated. Since the scale is small, the load on the arithmetic software can be reduced.

In the above virtual operation, the previous
Wheel speed conversion value Vwb of the integrated value of the counter until the
Is stored, and the stored wheel speed conversion value Vwb,
Count difference from the previous interrupt to the current interrupt
From the wheel speed conversion value Vwn, the wheel speed Vw is calculated as 1 / ｛(1 /
Vwb) + (1 / Vwn)｝
Previous wheel speed conversion value saved at the previous interrupt
Vwb is set to a value other than the wheel speed
It can be used as it is for calculation (for example, calculation of acceleration).
And convenience is high.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an embodiment of the present invention.

FIG. 2 is a diagram illustrating a comparison between the present invention and a conventional technique.

FIG. 3 is a state diagram of a pulse signal and a counter value in a normal speed range.

FIG. 4 is a state diagram of a pulse signal and a counter value in a low speed range.

FIG. 5 is a flowchart showing the operation of the embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 wheel speed sensor 2 waveform shaping means 3 pulse signal of wheel speed sensor 4 counter 5 wheel speed calculating means 6 flag setting means 7 flag determining means

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-59-196467 (JP, A) JP-A-64-26165 (JP, A) JP-A-63-221251 (JP, A) JP-A-63-221 238563 (JP, A) Fully open sho 63-50064 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) G01P 3/00-3/80

Claims (1)

(57) [Scope of request for utility model registration] And 1. A wheel speed sensor wheel that outputs a speed pulse each time a certain amount of rotation, the self-propelled counter for counting cyclically from zero value a clock having a predetermined period to the limit value, the
In the normal speed range where the count value of the counter does not overflow, the count output of the self-propelled counter is captured in synchronization with the speed pulse output by the wheel speed sensor, and the count difference from the previously captured count output is calculated. it and a wheel speed calculation means for converting the wheel speed by dividing the distance traveled between the wheel in a predetermined cycle multiplied by a value to rotate the predetermined amount, the wheel speed calculating means, the count value of the counter is over
In the flowed low speed range, an interrupt is issued with an interrupt cycle shorter than the cycle of the speed pulse, and the count output of the self-propelled counter is taken in every interrupt made until the next speed pulse is obtained, The wheel speed conversion value Vwb of the count integrated value of the self-propelled counter up to the previous interruption is stored, and the stored wheel speed conversion value Vwb is stored.
From the wheel speed conversion value Vwn of the count difference from the previous interrupt to the current interrupt, the wheel speed Vw is calculated as 1 /
(1 / Vwb) + (1 / Vwn)}.