JP2546458B2 - Ground speed detector - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ground vehicle speed detecting device, and more particularly to a technique for improving its detection accuracy.

[0002]

2. Description of the Related Art A ground vehicle speed sensor for detecting a ground vehicle speed, which is a traveling speed of a vehicle with respect to a road surface, is already known. For example, as described in Japanese Patent Laid-Open No. 63-46961, a Doppler type vehicle speed sensor utilizing the Doppler effect of waves, a road surface pattern (surface unevenness) such as an asphalt road, a sandy road, etc. It is a spatial filter type ground vehicle speed sensor to be used.

Further, the applicant of the present invention has previously developed the following ground speed detecting device. This is (a) ground speed sensor,
(b) The sample vehicle speed, which is a sample of the ground vehicle speed, is determined by sequentially acquiring the output signal from the ground vehicle speed sensor, and the current sample vehicle speed is estimated from the multiple sample vehicle speeds from the previous time to the past multiple times. If the vehicle speed or the allowable range around the estimated vehicle speed estimated from the wheel speed of at least one of the plurality of wheels of the vehicle is in the allowable range, it is estimated that the variation in the output signal of the ground vehicle speed sensor is small, While setting the sample vehicle speed this time to the ground vehicle speed this time, if the sample vehicle speed this time is not within the allowable range, it is estimated that the variation in the output signal of the ground vehicle speed sensor is large, and the sample vehicle speed this time is corrected. It is a ground vehicle speed detection device including a signal processing means for acquiring the current ground vehicle speed.

In the method of estimating the ground vehicle speed from the wheel speed of at least one of the plurality of wheels of the vehicle, for example, when the average value of the left and right non-driving wheels or the driving wheels of the vehicle represents the ground vehicle speed. Estimate method and when braking the vehicle, estimate that the wheel speed of the fastest wheel among the multiple wheels of the vehicle that has the highest wheel speed represents the ground vehicle speed, and sequentially determine the estimated vehicle speed, and determine the deceleration of the fastest wheel. After exceeding the predetermined upper limit value, it is possible to adopt a method of fixing the deceleration to the upper limit value and sequentially determining the estimated vehicle speed.

[0005]

In the developed device, the allowable range for determining whether the variation in the sample vehicle speed at this time is small, that is, whether the sample vehicle speed at this time is a reliable value or not. The width, that is, the range of the ground vehicle speed this time, which can be accurately estimated from the estimated vehicle speed this time, has been unchanged. However, the accuracy of the estimated vehicle speed is not always constant. For example, when the estimated vehicle speed is determined based on the wheel speed of the fastest wheel during vehicle braking as described above, the accuracy of the estimated vehicle speed decreases as the slip ratio of the fastest wheel increases. Therefore, in this development device,
There is a problem that the ground vehicle speed cannot be detected with sufficiently high accuracy. The present invention has been made to solve this problem.

[0006]

The gist of the present invention is, in the ground vehicle speed detecting device including the ground vehicle speed sensor and the signal processing means, the signal processing means sequentially fetches output signals from the ground vehicle speed sensor. A sample vehicle speed, which is a sample of the ground vehicle speed, is determined, and the sample vehicle speed this time is an estimated vehicle speed estimated from a plurality of sample vehicle speeds from the last time to the past multiple times or at least one wheel of the plurality of wheels of the vehicle. When the estimated vehicle speed estimated from the speed is within the allowable range, the sample vehicle speed this time is set as the vehicle speed to ground this time, while when the sample vehicle speed this time is not within the allowable range, the sample vehicle speed this time is set. Is corrected to obtain the vehicle speed to the ground this time, and the allowable range is made wider when the accuracy of the current estimated vehicle speed is low than when it is high.

In the "method for estimating the ground vehicle speed from a plurality of sample vehicle speeds from the last time to the past several times", for example, the extraction of the past sample vehicle speed and the current sample vehicle speed considers the vehicle deceleration to be 0. Assuming that it was done under the circumstances to obtain, estimate the vehicle speed to ground by taking into account the method that the average value of the past multiple sample vehicle speeds represents the estimated vehicle speed and the actual vehicle deceleration during sample vehicle speed extraction A method etc. can be adopted.

Further, in the "method for estimating the ground vehicle speed from the wheel speed of at least one of the plurality of wheels of the vehicle", for example, as described above, the average of the left and right non-driving wheels or the driving wheels is averaged. A method of estimating that the value represents the ground vehicle speed, a method of estimating that the wheel speed of the fastest wheel represents the ground vehicle speed during vehicle braking, and the like can be adopted.

When the estimated vehicle speed of this time is estimated from a plurality of sample vehicle speeds from the last time to a plurality of past times, for example, "when the accuracy of the estimated vehicle speed of this time is high".
In addition, it is possible to select a case where the sum of the deviations of each of the past sample vehicle speeds from the ground vehicle speed is small, and a case where the sum of the deviations is large when "the accuracy of the estimated vehicle speed this time is low".

The estimated vehicle speed this time is
Determine the estimated vehicle speed by estimating that the wheel speed of the fastest wheel that has the highest wheel speed among the plurality of wheels of the vehicle represents the ground vehicle speed, and after the deceleration of the fastest wheel exceeds a predetermined upper limit value. Is based on the method of determining the estimated vehicle speed by fixing the deceleration to its upper limit value, for example, when the accuracy of the estimated vehicle speed of this time is high, the estimated vehicle speed of this time is less than or equal to the fastest wheel. Yes, and a second reference vehicle speed estimated from a plurality of estimated vehicle speeds from the previous time to a plurality of past times and a second reference vehicle speed estimated from a plurality of sample vehicle speeds from the previous time to a plurality of past times
Select when the vehicle speed difference from the reference vehicle speed of is less than or equal to the reference value,
In "When the accuracy of the current estimated vehicle speed is low", select the case where the current estimated vehicle speed is less than or equal to the fastest wheel and the vehicle speed difference is greater than the reference value, or the current estimated vehicle speed is greater than the fastest wheel. You can

The "first reference vehicle speed" and the "second reference vehicle speed" here can be determined in the same manner as the "estimated vehicle speed".

The signal processing means may correct the sample vehicle speed this time, for example, by replacing the sample vehicle speed this time with the previous ground vehicle speed or by replacing the sample vehicle speed this time with the second reference vehicle speed. A method or a method of replacing the sample vehicle speed this time with an upper limit value or a lower limit value of the above-mentioned allowable range can be adopted.

[0013]

In the ground vehicle speed detecting device according to the present invention, the sample vehicle speed of this time based on the output signal from the ground vehicle speed sensor is not always set to the ground vehicle speed of this time, but the sample vehicle speed of this time is the past plural times. If the estimated vehicle speed estimated from multiple sample vehicle speeds up to the number of times or the estimated vehicle speed estimated from the wheel speed of at least one of the multiple wheels of the vehicle is in the allowable range, The sample vehicle speed of is set as the ground vehicle speed of this time, and when the sample vehicle speed of this time is not within the allowable range, the sample vehicle speed of this time is corrected and the ground vehicle speed of this time is acquired. Further, the allowable range is narrowed when the accuracy of the estimated vehicle speed this time is high, and widened when the accuracy is low.

[0014]

As described above, according to the present invention, the width of the permissible range for determining whether the sample vehicle speed at this time is a reliable value is proper in relation to the accuracy of the estimated vehicle speed at this time. Therefore, the effect that the detection accuracy of the ground vehicle speed is improved is obtained.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A ground vehicle speed detecting device having an ultrasonic Doppler type ground vehicle speed sensor according to an embodiment of the present invention will be described in detail below with reference to the drawings. This ground vehicle speed detection device is shown in FIG.
As shown in FIG. 3, the ground vehicle speed sensor 14 including the transmitter 10 and the receiver 12 and the signal processing means 16 are provided.
The ground speed sensor 14 is fixed to the bottom surface of the vehicle body (not shown). Both the transmission unit 10 and the reception unit 12 are fixed in a state of diagonally facing the road surface. The transmitter 10 transmits ultrasonic waves toward the road surface. The receiving unit 12 receives the ultrasonic wave whose transmitted wave is reflected on the road surface and outputs a signal corresponding to the frequency of the received wave.

On the other hand, the signal processing means 16 includes a CPU and RO.
The main component is a computer including M, RAM and a bus, and the receiving unit 12 is connected to the bus. The bus is further provided with a brake switch 30 which is turned on when a driver's brake operation is detected, and is turned off when a driver does not detect the brake operation, and four wheel speeds VW of the left and right front wheels and the left and right rear wheels of the vehicle. The wheel speed sensor 40 and the antilock control device 50 are connected. The antilock control device 50 includes the signal processing means 16
The vehicle ground speed U is sequentially read from the RAM, the slip state of each wheel is estimated with reference to the ground vehicle speed U, and the brake pressure of each wheel is controlled so that each wheel does not fall into the locked state during vehicle braking. is there.

The ROM stores a ground vehicle speed calculation routine represented by the flowchart of FIG. 1, and the ground vehicle speed calculation routine is periodically executed by the CPU.

In each execution of the ground vehicle speed calculation routine, first, in step S1 (hereinafter referred to simply as S1; the same applies to other steps), the ultrasonic wave transmission frequency and reception frequency, and the vehicle traveling speed of the ground vehicle speed sensor 14 are advanced. Based on the inclination angle with respect to the direction, the sample vehicle speed U, which is the current sample of the ground vehicle speed, is used by using the Doppler effect of ultrasonic waves.
SMP is calculated.

Subsequently, in S2, it is determined whether or not the vehicle is currently being braked, that is, whether or not the brake switch 30 is in the ON state. If it is assumed that the vehicle is not being braked this time, the determination is NO, and in S3, the current sample vehicle speed USMP is determined as the current ground vehicle speed U. Thus, one execution of this routine is completed.

On the other hand, assuming that the vehicle is currently being braked, the determination in S2 is YES, and in S4,
The wheel speed VW of each wheel is calculated based on the output signals from each of the four wheel speed sensors 40, and the wheel speed VMAX (hereinafter, wheel speed VMAX of the fastest wheel having the maximum wheel speed VW among the four wheels is calculated. Simply called the fastest wheel speed VMAX)
Is determined. Then, in S5, the current ground vehicle speed U is estimated from the four wheel speeds VW. In particular,
The estimated vehicle speed VSO is determined by estimating that the fastest wheel speed VW represents the ground vehicle speed U, and after the deceleration of the fastest wheel exceeds a predetermined upper limit value, the deceleration is fixed to the upper limit value and estimated. The vehicle speed VSO is determined.

Thereafter, the current vehicle speed U to ground is calculated using the current sample vehicle speed USMP, the estimated vehicle speed VSO, the fastest wheel speed VMAX, etc. First, some assumptions used in the calculation will be described. .

The vehicle braking state is such that the estimated vehicle speed VSO is higher than the fastest wheel speed VMAX and the fastest wheel speed VMA.
The slip state of the fastest wheel in the former state is larger than that in the latter state, and the estimated vehicle speed VS is
Assume that the accuracy of O is low. Therefore, in the former state, the allowable range width β around the current estimated vehicle speed VSO for determining whether or not the sample vehicle speed USMP is a reliable value is β ₁ , and in the latter state the allowable range is β ₁ . Range width β
Is defined as β ₂ (<β ₁ ). The tolerance of the former condition is wider than that of the latter condition.

However, in the latter state, that is, in the state where the estimated vehicle speed VSO is equal to or lower than the maximum wheel speed VMAX, the width β of the allowable range is set to β _{2 in} principle, and there are exceptions. That is, in this state, the difference between the average value VSOM of the plurality of estimated vehicle speeds VSO from the previous time to the past multiple times and the average value USMPM of the plurality of sample vehicle speeds USMP from the previous time to the past multiple times is smaller than the reference value γ _1. When divided into a first state, a second state that is more than that and is less than or equal to the reference value γ ₂ (> γ ₁ ), and a third state that is greater than the reference value γ ₂ , in principle, the first state is As described above, the width β of the allowable range is set to β ₂ , but in the second state, the estimated vehicle speed VS
As in the case where O is greater than the fastest wheel speed VMAX, the width β of the permissible range is set to β _1, and in the third state, the sample vehicle speed USMP of this time is set to the vehicle speed U to this ground as it is.

In the first and second states, the estimated vehicle speed VSO and the true ground vehicle speed U are substantially equal to each other, and the difference between the estimated vehicle speed VSO and the sample vehicle speed USMP is mainly the ground vehicle speed sensor 14.
Of the output signal of, i.e., an error of the sample vehicle speed USMP, and the allowable range of the second state where the signal variation is large is made wider than the allowable range of the first state where the signal variation is small. Of. On the other hand, in the third state, the estimated vehicle speed VSO largely deviates from the true ground vehicle speed U, and it is assumed that the difference between the estimated vehicle speed VSO and the sample vehicle speed USMP is mainly an error of the estimated vehicle speed VSO. The sample vehicle speed USMP of this time is directly used as the vehicle speed U to the ground.

The above will be described with reference to the flowchart of FIG. 1. First, at S6, the estimated vehicle speed VSO
Is determined to be greater than the fastest wheel speed VMAX,
Assuming this is the case this time, the determination is YES,
In S7, the width β of the allowable range is set to β ₁ . On the other hand, assuming that the estimated vehicle speed VSO is equal to or lower than the fastest wheel speed VMAX, the determination in S6 is NO, and in S8, the average value VSOM of the estimated vehicle speed VSO and the sample vehicle speed US.
It is determined whether or not the difference between the average value USMPM of MP and the reference value γ _{1 is} larger than the reference value γ ₁ . If this is not the case this time, the determination is NO (corresponding to the first state described above),
In S9, the allowable range width β is set to β ₂ , but if this is the case this time, the determination in S8 is YES, and in S10, the average value VSOM of the estimated vehicle speed VSO.
It is determined whether the difference between the average value USMPM of the sample vehicle speed USMP and the reference value γ _{2 is} larger than the reference value γ ₂ . If this is not the case this time, the determination is NO (corresponding to the above-mentioned second state), and the width β of the allowable range is set to β _{1 in} S7, but this time is assumed to be the case. If so, the determination in S10 is YES (corresponding to the third state described above), and S11
At this time, this sample vehicle speed USMP is this ground vehicle speed U
Is stored in the RAM.

The estimated vehicle speed VSO and the fastest wheel speed VM
Relationship between AX and below, average value VS of estimated vehicle speed VSO
The relationship between the difference between the OM and the average value USMPM of the sample vehicle speed USMP and each of the reference values γ ₁ and γ ₂ is not always kept constant during vehicle braking. It changes depending on the operation.

When S11 is executed, one execution of this routine ends, but when S7 or S9 is executed, subsequently, at S12, the sample vehicle speed U at this time is obtained.
Is above the upper limit value (= VSO + β ₁ or β ₂ ) of the allowable range centered on the estimated vehicle speed VSO at this time, and if this is not the case this time, the determination becomes NO, and S13 In this case, the sample vehicle speed U this time is the lower limit value (=) of the allowable range centered on the estimated vehicle speed VSO this time.
VSO-β ₁ or β ₂ ) is determined, and if this is not the case this time, the determination becomes NO, and in S14, the current sample vehicle speed USMP is stored in RAM as the current ground vehicle speed U. Remembered. Thus, one execution of this routine is completed.

On the other hand, if the sample vehicle speed U this time is higher than the upper limit value of the allowable range or lower than the lower limit value of the allowable range, the determination in S12 or S13 becomes YES, and S15 is determined. In, the previous ground vehicle speed U is stored in the RAM as the current ground vehicle speed U. Thus, one execution of this routine is completed.

Therefore, in this embodiment, the width β of the allowable range for determining whether or not the sample vehicle speed USMP of this time is a reliable value is the estimated vehicle speed VSO of this time (this is the "estimated vehicle speed" in the present invention). Therefore, the effect of improving the detection accuracy of the ground vehicle speed U can be obtained.

In the present embodiment, the determination in S2 of FIG. 1 is NO, that is, when the vehicle is not braked, the sample vehicle speed USMP of this time is immediately set to the ground vehicle speed U of this time. , The sample vehicle speed of this time USMP
However, multiple sample vehicle speeds USMP from last time to past times
If the estimated vehicle speed (eg, the average value of the past sampled vehicle speeds USMP) is within the allowable range, the sampled vehicle speed USMP at this time is set as the vehicle speed to ground U at this time. If the USMP is not within the allowable range, the current sample vehicle speed USMP can be corrected to obtain the current ground vehicle speed U. Current sample vehicle speed USM
As a method of correcting P, a method of using the current sample vehicle speed USMP as the previous vehicle speed to ground U, a method of using the above average value,
A method of setting the upper limit value or the lower limit value of the above allowable range can be adopted.

Although one embodiment of the present invention has been described in detail with reference to the drawings, various modifications and improvements can be made based on the knowledge of those skilled in the art without departing from the scope of the claims. Of course, the present invention can be carried out in the manner in which it is applied.

[Brief description of drawings]

FIG. 1 is a flowchart showing a ground vehicle speed calculation routine used by a computer of a ground vehicle speed detection device according to an embodiment of the present invention.

FIG. 2 is a system diagram showing the ground vehicle speed detection device.

[Explanation of symbols]

 14 Ground Vehicle Speed Sensor 16 Signal Processing Means

Claims (1)

(57) [Claims] 1. A ground vehicle speed sensor for detecting a ground vehicle speed, which is a traveling speed of a vehicle with respect to a road surface, and a sample vehicle speed, which is a sample of the ground vehicle speed, is determined by successively capturing output signals from the ground vehicle speed sensor. Of the sample vehicle speed is an estimated vehicle speed estimated from a plurality of sample vehicle speeds from the previous time to the past several times or an estimated vehicle speed estimated from a wheel speed of at least one wheel of the plurality of wheels of the vehicle. If it is within the range, the current sample vehicle speed is set as the current ground vehicle speed.On the other hand, if the current sample vehicle speed is not within the allowable range, the current sample vehicle speed is corrected to obtain the current ground vehicle speed. And a signal processing means for making the allowable range wider when the accuracy of the estimated vehicle speed at this time is low than when it is high.