JPH03138588A - Method for outputting measured distance of vehicle - Google Patents

Abstract

PURPOSE:To securely detect a precedent vehicle and to prevent a distance display from being interrupted by comparing the absolute values of the speed and acceleration of a body at the front which are calculated from the distance to the body at the front and the speed of the vehicle on this side with absolute values. CONSTITUTION:The distance (r) to the body at the front which is measured by a distance meter 1 and the speed (u) of the vehicle on this side which is measured by a vehicle speed sensor 2 are inputted to a computer 3. Then when the absolute value of the acceleration of the body at the front exceeds the specific value or when the speed of the body at the front is less than the specific value, it is decided that the body at the front is the precedent vehicle and the distance display 4 is started. If a distance measuring beam deviates from the precedent vehicle in this state owing to the pitching vibration of the vehicle on this side, the absolute value of the acceleration exceeds the specific value. In this case, a distance which is predicted from a distance which is a certain period before and the relative speed with the body at the front is outputted until the precedent vehicle is caught within a specific time and the difference between the detected distance and predicted distance decreases below a constant error, thereby evading the interruption of the display 4.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for outputting a measured distance of a vehicle, and more particularly to a method for outputting a measured distance suitable for use in displaying inter-vehicle distance, etc.

[Conventional technology] It is desired to display the distance between the vehicle in front and issue a warning if necessary to prevent falling asleep and avoid rear-end collisions due to distracted driving. Consideration is being given to installing a meter in a vehicle.

[Problems to be Solved by the Invention] In this case, for example, when driving on a curved road, there is a risk that the distance detection beam may catch the reflector array on the guardrail or an oncoming vehicle, causing it to be mistakenly detected as a preceding vehicle. On undulating roads, the distance detection beam often deviates from the vehicle in front due to vibrations caused by the pitching of one's own troops, causing a problem in which the distance display is interrupted.

Therefore, an object of the present invention is to provide a method for outputting a measured distance of a vehicle that can reliably detect only the preceding vehicle and that does not interrupt the distance display even if the distance detection beam is temporarily deviated. The purpose is to provide.

[Means for Solving the Problems] The method of the present invention detects the distance to the object in front of the vehicle at regular intervals, detects the vehicle speed of the own vehicle, and calculates the speed of the object in front of the vehicle based on the detected distance and vehicle speed. and acceleration, and if the absolute value of the acceleration of the forward object exceeds a predetermined value or the speed of the forward object is less than another predetermined value, the output of the detection distance is stopped; When the absolute value of the acceleration of the forward object is below the predetermined value and the speed of the forward object is above the other predetermined value, the output of the detected distance is started, and after the output starts, the absolute value of the acceleration of the forward object is started. exceeds the predetermined value, outputs an expected distance calculated from the distance displayed one cycle ago and the relative speed of the object ahead calculated one cycle ago, instead of the detected distance, Thereafter, if the difference between the detected distance and the predicted distance falls within a certain error range within a predetermined time, the detected distance is output again.

[Operation] In the above method, the acceleration value obtained from an object such as a reflector array of a guardrail is generally very large, and in such a case, the distance output is stopped. Further, since the speed obtained from an object such as an oncoming vehicle is a negative value, the distance output stops in this case as well.

The absolute value of the acceleration of the forward object is a predetermined value (for example) - ~ 5 m
/s2) and the speed is at another predetermined value (e.g. 10~
(20 km/h) or more, it is assumed that the vehicle is in front and starts displaying the distance.

In this state, if the distance measuring beam deviates from the preceding vehicle due to pitching vibration or the like, the absolute value of the acceleration exceeds the predetermined value. In this case, the predicted distance is output until the preceding vehicle is again detected within a predetermined time and the difference between the detected distance and the predicted distance falls within a certain error range, thereby avoiding interruption of the display, etc.

[First Embodiment] FIG. 1 shows the equipment configuration for realizing the method of the present invention, and numeral 1 in the figure is a distance meter. The distance meter 1 is a radar device that uses ultrasonic waves or laser light, and measures the distance to an object in front of the vehicle, and inputs the measured value r to the computer 3. In addition,
If no object is detected, the value of distance r is infinite (ω
).

The computer 3 also inputs the speed (speed of own troops) of the own vehicle measured by the vehicle speed sensor 2, and the computer 3 processes the distance r and speed U, and if necessary, calculates statistics such as averaging. It performs processing and stores the latest values so that they can be referenced by other programs. and,
A radar program (described later) is executed at a constant period T, and the latest distance r is calculated. , or the predicted distance r, is output to a display device 4 composed of a light emitting diode or the like.

The processing contents of the radar program will be explained below.

In Fig. 2, when the program is started at a cycle T (1/8 second), the own vehicle speed U and distance r are input, and the past Tbu
The values of speed U and distance r for ff seconds are added as r□ and u□ to the ring buffer (step 101). This ring buffer also stores the velocity V of the forward object, which is determined by differential calculation from the velocity U and the distance r.

If the measured distance r is ω, then the count variable k
Clear v and set the acceleration absolute value A obtained by the calculation described later as ω (steps 102 and 104). If the distance r is not ω, the count variable kv is counted up (Stella 1103.106).

If a predetermined number N of distances r that are not ω are obtained, the velocity V of the forward object is calculated and recorded as V□, and the absolute value A is calculated (step 103.
105). This calculation is performed using the following difference formula% formula%)) Here, max □ is the maximum value, A(i, j) is the absolute value of acceleration when the time interval of difference calculation is iT, and A(
i,j>−lα(i,j)l−”N.

13H/i (i=1.2.4>.

αN0ISE is a constant determined by taking into consideration the dispersion of distance data, and if the standard deviation of r is σ, it needs to be equal to or greater than rτσ/T2.

α(i, j) is the acceleration at time j when the time interval is iT, and α(i, j>=(V(i.

It is calculated as j) -V H, ji))/(iT>).

Here, V(i, j> is the speed at time jT of time interval iT, and V(i, j> −= (r −−r,
・)J-1/(iT)+uj.

As described above, the absolute value of acceleration is calculated for multiple time intervals (sampling intervals), the noise amount α /i corresponding to each time interval is subtracted, and the maximum value of these values is calculated after each time interval. This is because when the time interval is long, the accuracy of acceleration calculation is good and even small accelerations can be detected, whereas when the time interval is long, high frequency components where the distance changes drastically may be missed.

Conversely, if the time interval is made smaller, high frequency components will not be missed, but the accuracy will deteriorate significantly (in proportion to the square of the interval). From step 107 onward in Figure 2, in order for the value of A to be not ω, N pieces of data that are not ω must be measured continuously.
x Must be defined. Also, if A is not ω,
A is given the maximum acceleration (taking into account noise) among the past N pieces of data.

The reason why I specifically explained the acceleration calculation in detail is that although the resolution of currently available inexpensive rangefinders is about 1 m, the acceleration calculation result is 1 m / 1 m / 1 m in measurement time of 1 second.
This is because accuracy on the order of S2 is required. In addition, V(4
, 0) is also V. recorded in the ring buffer.

Next, in step 107, one of the subroutines S1 to S3 is executed depending on the value of the state variable S.

At the start of program execution, the state variable S is S1, and from step 107 the subroutine S1 in FIG. 3 is executed unconditionally. That is, in step 201,
If the absolute acceleration value A of the forward object is larger than the predetermined value αmax or if the speed V of the forward object is smaller than the predetermined value vmin, it is assumed that the forward object is not the preceding vehicle, and ω is displayed as the distance r in step 202. It is output to bag W4 and the display is stopped.

On the other hand, in step 201, if the forward object is moving forward at a low acceleration and a speed above a certain level, it is determined that it is a preceding vehicle, and the state variable S is set to S2.
Step 203>, the distance r at this time is output to the display device.

As mentioned above, since the state variable S becomes S2 when the preceding vehicle is detected, the subroutine S2 of FIG. 4 is executed in the next program execution cycle.

As long as the calculated absolute acceleration value A is less than or equal to the predetermined value αmax, the measured distance r is displayed on the display device (steps 301 and 302).

If the absolute value A exceeds the predetermined value αmax, the process proceeds to step 303. In this step, the preceding vehicle speed v-1 obtained one cycle ago is set as the latest speed V□, and this is set as the expected speed V.

Then, an expected distance r is calculated from the speed V-1, the own speed u-1 obtained one cycle earlier, and the distance r-1, and this is set as the latest distance r. shall be. Also, clear the count variable kE used in subroutine S3, which will be described later, and set the state variable S to 83.
shall be. Subsequently, the predicted distance rE is displayed on the display device 4 (step 304).

In this way, if the distance measuring beam deviates from the preceding vehicle due to pitching vibration or the like after detecting the preceding vehicle, the predicted distance is output, and interruption of the display can be avoided.

In the subroutine S3 of FIG. 5, which is executed in the next program cycle, in step 401, the count variable kE is counted up, and the predicted distance r, predicted speed VE, and own vehicle speed obtained one cycle ago are counted up. A new expected distance rE is calculated from U and period T. Then, it is checked whether the difference between this expected distance rE and the actual measured distance r is within a certain error Δγ (Step 402), and furthermore, the absolute value of acceleration 0A is less than or equal to a predetermined value αmax and the forward object velocity V is a predetermined value. After confirming that the count variable kt is not greater than or equal to the value vmin and that the count variable kt has not reached the upper limit NEmax, outputting the predicted distance rE is continued (steps 403 to 405).
).

In step 402, if the difference between the expected distance rE and the measured distance r falls within the fixed error Δγ, it is determined that the measurement beam has been able to guide the preceding vehicle again, and the process proceeds to step 406 and subsequent steps. In step 406, the previous rF and v are set so that the acceleration absolute value A does not become ω in the next program cycle.
Interpolate the value of E into the ring buffer. Then, the state variable S is set to 82 (step 407), and the measured pressure 'far is outputted to the display device 4 again.

In step 403, if the acceleration absolute value A is less than or equal to the predetermined value αmax and the forward object velocity V is greater than or equal to the predetermined value vmin, it is assumed that another vehicle in front can be urged, and the state variable S is changed to 82 (step 409). , and output the measured distance r (step 410).

1 In step 404, if the count variable kE does not reach the upper limit NEmax without rediscovering the preceding vehicle, the state variable S is set to 81, ω is output, and the display is stopped (steps 411 and 412). .

An example of the distance output operation by executing the above program is shown in the sixth section.
This will be explained with a diagram.

When the measuring beam of the range finder 1 is approaching the reflector array of the guide rail periodically (A region in the figure), the subroutine S1 is executed and the display is stopped.

If you can prompt the preceding vehicle with low acceleration and above a certain speed,
After a time Ty max (this is the time during which the count variable ky is equal to or greater than Nymax in step 103) for measuring the number of distances r and velocities U required for acceleration calculation, the measured distance r is output and displayed. Start. Thereafter, subroutine s2 is executed (area B in the figure).

When the measurement beam deviates from the preceding vehicle due to pitching vibration of the vehicle (region C in the figure), the expected distance rE2 is calculated and subroutine S3 is executed, and thereafter the expected distance rE is displayed. In this state, if the preceding vehicle is prompted again within a predetermined time, the measured distance r is displayed again in place of the predicted distance r[, and subroutine S2 is executed (area D in the figure).

In this state, when another vehicle intervenes between the preceding vehicle and the preceding vehicle (region E in the figure), the absolute acceleration value A rapidly increases, and thereafter the predicted distance r is displayed for a while by subroutine S3. Then, when the number of distances r for which the acceleration can be calculated with respect to the new preceding vehicle is measured, the calculated absolute acceleration value A becomes smaller, the process moves to subroutine S2, and the measured distance r is output again (step 409.410).

If the preceding vehicle disappears (region F in the figure), the expected distance rE continues to be output for a while in subroutine S3, but for a certain period of time TE max (this is the time when the count variable kE exceeds NFmax in step 404). ), the process returns to subroutine S1 and the display stops.

In the above embodiment, if the value of the minimum speed vmin, which is a condition for recognizing a preceding vehicle, is set to zero, it becomes possible to detect stopped vehicles on the road.

Furthermore, from a fail-safe perspective, it is possible to prevent the expected distance rE from increasing. That is, step 303
In, as the value of VE used in step 401,
When V -1> u-1, use u-1, and when V -1<
If V-1 is used only when Ll-1, the expected distance rE will not increase as long as the speed of the own army remains constant.

[Effects of the Invention] As described above, according to the measured distance output method of the present invention, there is no possibility that a vehicle other than the preceding vehicle, such as a guardrail reflector array, will be mistakenly detected as the preceding vehicle and output, and the distance will not be output due to pitching vibration or the like. Even if the measurement beam temporarily deviates from the preceding vehicle, the problem of output interruption does not occur. Thus, it can be suitably used for displaying inter-vehicle distance and for warning purposes.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an apparatus for implementing the method of the present invention, FIGS. 2 to 5 are program flowcharts, and FIG. 6 is a diagram showing an example of distance output operation. 1...Distance meter 2...Vehicle speed sensor 3...Convenience monitor 4...Display device-5 Fig. 2 JP-A-3-138588 (6) Fig. 3 Fig. 4

Claims (1)

[Claims] The distance to the object in front of the vehicle is detected at regular intervals, and the vehicle speed of the own vehicle is detected, and the speed and acceleration of the object in front of the vehicle are calculated from the detected distance and vehicle speed, and the absolute value of the acceleration of the object in front of the vehicle is calculated. If the speed of the forward object exceeds a predetermined value or falls below another predetermined value, the output of the detected distance is stopped; on the other hand, if the absolute value of the acceleration of the forward object is less than or equal to the predetermined value, And when the speed of the forward object is equal to or higher than the other predetermined value, output of the detected distance is started, and if the absolute value of the acceleration of the forward object exceeds the predetermined value after the start of output, the detected distance is Instead, the expected distance calculated from the distance displayed one cycle ago and the relative speed of the object ahead calculated one cycle ago is output, and then the detected distance and the above predicted distance become constant within a predetermined time. A method for outputting a measured distance of a vehicle, characterized in that the detected distance is outputted again if the detected distance falls within the error range.