KR100312211B1 - Method of acquiring vehicle information using ultrasonic traffic volume detector - Google Patents

Abstract

The present invention relates to a method of acquiring vehicle information using an ultrasonic vehicle detector, comprising: (a) installing two ultrasonic sensors synchronized with ultrasonic transmission time in one lane; (B) detecting a reflected wave signal of the vehicle sensed by the two ultrasonic sensors installed in the step (a); T ₁ = t ₂ -t ₁ , t ₂ = t ₄ -t ₃ , t ₃ = t ₃ -t ₁ , t ₄ = t ₄ -t ₂ and t ₁ is the output of the ultrasonic sensor time at which the "1" from "0", t ₃ is the time the output from the ultrasonic sensor that the vehicle is passing through first to be '0' at '1', t ₂ is the output from the ultrasonic sensor that the vehicle passes later 0 '' 1 'this time, t ₄ the vehicle from the output of the ultrasonic sensor to pass later, when that time interval which is a time-zero ", from" 1, t _stat calculates the share, And the vehicle occupancy rate P _oc (C); Let l _{d be} the distance between the two ultrasonic sensors, , The speed v of the individual vehicle is defined as (D); And the length of the detection area of the sensor is defined as l _s , and the length of the individual vehicle is defined as l _car by using the t _oc obtained in the step (c) and the value obtained in the step (d), l _car = υ × t _oc (e) of calculating the value of the second parameter by -l _s . In the method according to the present invention, two ultrasonic sensors are provided in one lane, and the reflected wave output form of the two ultrasonic sensors is analyzed to obtain not only the vehicle count and occupancy but also the information about the speed of the vehicle and the length of the vehicle Can be obtained.

Description

Method of acquiring vehicle information using ultrasonic traffic volume detector

The present invention relates to a method of acquiring vehicle information using an ultrasonic traffic volume detector, and more particularly, it is possible to specify not only the occupancy rate of road, which is statistical vehicle information, but also the vehicle speed and length, which are individual vehicle information.

The traffic volume detector is the lowest level equipment of the traffic management system and it is the basic element for building the urgent Intelligent Transportation System (ITS) to solve the traffic congestion.

Vehicle detectors and traffic information gathering equipment using ultrasonic sensors are non-burdensible and can be installed at a lower cost than other equipments and the life span is also semi-permanent so that maintenance is easy.

First, the principle of the ultrasonic traffic volume detecting apparatus will be described.

An ultrasonic sensor including a transmitting unit and a receiving unit is installed at a predetermined height from the road surface, a transmission wave is periodically emitted from the ultrasonic sensor, and the passage of the vehicle is detected by sensing reflected waves.

1 is a view for explaining the principle of an ultrasonic traffic volume detecting apparatus.

For example, when the ultrasonic sensor is installed at a height of 6 m from the road surface, the time taken for the transmission wave emitted from the ultrasonic sensor to be reflected from the ground free from the vehicle returns to the sound velocity of 340 m / s, to be. Considering this, the transmitter of the ultrasonic sensor periodically emits a transmission wave every 35 ms. During this period, the gate signal is activated as shown in FIG. 1. When the vehicle passes through this time, the reflected wave caused by the vehicle passing through the vehicle is reflected by the ground after the transmission wave is fired. It is detected within a short time. That is, when a reflected wave is detected in a section in which the gate signal is active, it means that the vehicle passes.

Conventionally, such ultrasonic vehicle detectors have been used to measure only the occupancy rate of the road, which is statistical vehicle data.

In particular, a vehicle detection signal can be detected by two vehicles depending on the shape of the vehicle. In this case, it is necessary to judge whether the detection signal is due to one vehicle or two vehicles in consideration of the speed and the distance between the vehicles. For this purpose, it is necessary to obtain individual vehicle information by using an ultrasonic vehicle detector.

SUMMARY OF THE INVENTION The present invention has been made to overcome the limitations of the prior art as described above, and it is an object of the present invention to provide a method and apparatus for measuring vehicle speed and vehicle length, I want to give you a way.

FIG. 1 is a view for explaining the principle of an ultrasonic traffic volume detector. FIG.

FIG. 2 is a view showing a state in which two ultrasonic sensors are installed in the method according to the present invention. FIG.

FIG. 3 is a diagram showing output signals from two ultrasonic sensors in the present invention. FIG.

FIG. 4 is an example in which the output of the ultrasonic sensor is supplemented to prevent counting of one vehicle in the vehicle counting mode.

Figure 5 is an example of supplementing the values required for vehicle speed calculation.

A method for acquiring a vehicle information using an ultrasonic vehicle detector according to the present invention comprises the steps of: (a) installing two ultrasonic sensors synchronized with ultrasonic transmission time in one lane; (B) detecting a reflected wave signal of the vehicle sensed by the two ultrasonic sensors installed in the step (a); T ₁ = t ₂ -t ₁ , t ₂ = t ₄ -t ₃ , t ₃ = t ₃ -t ₁ , t ₄ = t ₄ -t ₂ and t ₁ is the output of the ultrasonic sensor time at which the "1" from "0", t ₃ is the time the output from the ultrasonic sensor that the vehicle is passing through first to be '0' at '1', t ₂ is the output from the ultrasonic sensor that the vehicle passes later 0 '' 1 'this time, t ₄ the vehicle from the output of the ultrasonic sensor to pass later, when that time interval which is a time-zero ", from" 1, t _stat calculates the share, And the vehicle occupancy rate P _oc (C); Let l _{d be} the distance between the two ultrasonic sensors, , The speed v of the individual vehicle is defined as (D); And the length of the detection area of the sensor is defined as l _s , and the length of the individual vehicle is defined as l _car by using the t _oc obtained in the step (c) and the value obtained in the step (d), l _car = υ × t _oc (e) of calculating the value of the second parameter by -l _s .

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method of acquiring vehicle information using an ultrasonic vehicle detector according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 2 shows a state in which two ultrasonic sensors are installed in a lane in the vehicle information acquiring method according to the present invention. In Fig. 2, ℓ _s represents the length of the detection region by one ultrasonic sensor, and ℓ _d represents the distance between the ultrasonic sensors.

In FIG. 2, the sensor through which the vehicle first passes is referred to as a first sensor, and the sensor that passes through next is referred to as a second sensor. When two sensors as shown in FIG. 2 are installed, the output of the ultrasonic wave detector generally has a shape as shown in FIG.

3, the first output corresponds to the first sensor, and the second output corresponds to the second sensor. The time at which the first output becomes 0 to 1 is t ₁ , the time at which the first output becomes 0 at t ₃ , the time at which the second output becomes 0 to 1 is t ₂ , and the time when 0 is 1 becomes t ₄ do.

In this case, the _{Δt 1, Δt 2, Δt 3} , Δt 4 respectively defined as shown in Equation 1 below.

Since the transmission time of two ultrasonic sensor in synchronization _{Δt 1, Δt 2, Δt 3} , Δt 4 is an integer multiple of the ultrasound transmission period. Assuming that the transmission period is T _s , the method of obtaining the vehicle information from the generated output is as follows.

If the first sensor detects the vehicle and the second sensor detects the vehicle, it can be said that one vehicle has normally passed the road on which the sensor is installed. In this case, vehicle speed, occupancy, and individual vehicle information, such as vehicle speed and length, can be calculated. When the vehicle changes the lane at the place where the sensor is installed, only either the first sensor or the second sensor detects the vehicle depending on the situation. In this case, it is impossible to calculate the speed and length of the individual vehicle information, and only the vehicle count and the occupancy rate can be calculated.

First, the calculation of the vehicle coefficient will be described.

The number of vehicles having passed through the road may be counted as the number of output forms as shown in FIG. When only one of the sensors of the first sensor and the second sensor detects the vehicle, the vehicle is counted only when the first sensor detects it. This is to count vehicles only in one of two lanes when changing lanes of the vehicle.

The following describes the calculation of the share.

The occupancy rate is a value indicating how much the vehicles occupied the road. In the present invention, the sleeping rate is defined as a value obtained by dividing the sum of the time when the vehicle is in the detection area of the ultrasonic sensor for a predetermined time by a predetermined time. The larger the share of the road on which the sensor is installed, the more crowded the road.

Let t _stat be the time interval at which the statistical information is calculated. Let t _{oc, k} be the time occupied by the vehicle under the sensor at the kth time in the past n vehicles. From this, the _occupation rate P _oc can be expressed by the following equation (3).

Now, we explain how to find the speed and length, which are individual vehicle information.

And the distance between the sensor ℓ _d, if defined as the time t _p passes through the distance, two using the sensors, so t _p is calculated as in the following equation (4), the vehicle speed v is the following equation (5) with the And so on.

The length l _car of the vehicle can be obtained as shown in Equation (6) using the occupation time t _oc and the sensing area length l _s of the sensor.

The vehicle type can be classified according to the vehicle length using the vehicle length information obtained in the above.

In the above, the method of measuring the vehicle count, the occupancy rate, the speed of the individual vehicle, and the vehicle length using the ultrasonic vehicle detector has been described. Ultrasonic sensors sometimes fail to receive reflected waves during passage of the vehicle due to various causes. In order to maximize the functions of the ultrasonic traffic volume detector, the reflected waves that can not be received should be restored. Next, a method of restoring the reflected wave that can not be received by the method of measuring the vehicle count, the speed of the individual vehicle, and the vehicle length using the ultrasonic vehicle detector will be described.

In order to prevent counting of one vehicle at the time of vehicle counting, if the time between two vehicle detection signals is sufficiently small, it is regarded as one. The range of time for detecting two vehicle detection signals should be set so that different vehicles are not regarded as one. However, these two top conditions contradict each other. Considering this, the implemented sensor output should be supplemented. An example thereof is shown in Fig. As a result, if the distance between the two vehicles is small, it is detected as one, which is the limit of the vehicle coefficient of the ultrasonic traffic volume detector. Table 1 below shows the limit of the vehicle count by speed of the ultrasonic traffic volume detector.

As shown in Table 1, as the speed increases, the limit distance becomes longer. However, as the speed increases, the distance between the vehicles becomes larger.

Describe the compensation of the vehicle speed measured by the ultrasonic vehicle detector.

If the sensitivities of the two sensors installed in one lane are adjusted to be the same, the passing time of the sensor detecting area of the vehicle traveling along the lane at a constant speed is the same. If the time that the T _s, and the transmission period as t _b t _b satisfies the following equation (7) with respect to any natural number k.

In this case, Δt ₃ and Δt ₄ in Fig. 3 have one of kT _s or (k + 1) T _s . Therefore, the following equation (8) is established, and using this equation (8), the following equation (9) can be obtained.

When the output of the sensor does not satisfy Equations (8) and (9), since the front of most of the vehicles has a slope, there is a high possibility that the reflected wave of the vehicle can not be received from the rear. Therefore, It complements the values required for speed calculation.

In other words, _{If, Δt 4 = Δ t 3 -T} s, Δt 1 = Δt 2 + T s, If, as a complement _{Δt 3 = Δ t 4 -T s} , Δt 1 = Δt 2 + T s.

Since the ultrasonic sensor can not detect the slope of the vehicle well, the length of the vehicle is shorter than the actual length. In order to compensate for this, the length is supplemented by statistical information of the length of the vehicle.

As described above, in the method according to the present invention, two ultrasonic sensors are installed in one lane, and the reflected wave output style of the two ultrasonic sensors is analyzed. Accordingly, not only the vehicle coefficient and the occupancy rate, Information on the length of the vehicle can be obtained.

Claims (3)

(A) installing two ultrasonic sensors synchronized with the ultrasonic transmission time in one lane; (B) detecting a reflected wave signal of the vehicle sensed by the two ultrasonic sensors installed in the step (a); T ₁ = t ₂ -t ₁ , t ₂ = t ₄ -t ₃ , t ₃ = t ₃ -t ₁ , t ₄ = t ₄ -t ₂ and t ₁ is the output of the ultrasonic sensor time at which the "1" from "0", t ₃ is the time the output from the ultrasonic sensor that the vehicle is passing through first to be '0' at '1', t ₂ is the output from the ultrasonic sensor that the vehicle passes later 0 '' 1 'this time, t ₄ the vehicle from the output of the ultrasonic sensor to pass later, when that time interval which is a time-zero ", from" 1, t _stat calculates the share, And the vehicle occupancy rate P _oc (C); Let l _{d be} the distance between the two ultrasonic sensors, , The speed v of the individual vehicle is defined as (D); And the length of the detection area of the sensor is defined as l _s , and the length l _car of the individual vehicle is defined as l _car = υ × t _oc - 1 by using t _oc obtained in the step (c) and υ obtained in the step (d) wherein the step (e) comprises the step (e) of calculating the vehicle information using l _s . 2. The method according to claim 1, wherein when both the ultrasonic sensors detect the vehicle from the output signals of the two ultrasonic sensors for vehicle counting, the passing vehicles are counted as one, and when only one of the two ultrasonic sensors detects Wherein when the vehicle is detected by only one of the two ultrasonic sensors for each lane in which the two ultrasonic sensors are installed, the passing vehicle is counted as one. The method of claim 1, wherein, in order to compensate for the speed of the individual vehicle measured, _{If, Δt 4 = Δt 3 -T s} , Δt 1 = Δt 2 + T s, Wherein T ₃ is Δt ₄ -T _s , Δt ₁ = Δt ₂ -T _s , where T _s is an ultrasonic transmission period.