TWI440876B - Radar detectors detect the speed of the method - Google Patents

Description

Radar detector detecting method of vehicle speed

The present invention relates to a technique for detecting a vehicle speed, and more particularly to a method for detecting a vehicle speed by detecting a vehicle position and quickly calculating a vehicle speed.

According to the general roadside radar vehicle detector, the speed detection system is equipped with a radar that transmits and receives signals on the roadside, and detects from the side of the vehicle. The principle is to use the radar to measure the distance between the target vehicle and the radar, the time difference between the vehicle entering and leaving the radar detection area or the Doppler effect, and calculate the speed of the target vehicle. The hardware may comprise a combination of a transmitter-receiver, a transmitter two receiver or a two-transmitter two receiver.

Wherein, in a transmitter-receiver detection method, the receiver needs to perform a single loop algorithm for the distance between the target vehicle and the receiver at multiple time points, and after dividing the length of the detection area by using the length of the vehicle, The speed can be obtained, but since the length of the car is not fixed, it needs to be replaced by the average length of the car, so there will be errors; the speed is also detected by the Doppler effect, but the lateral detection Tuller effect is weak, the detection error The value is quite high.

Furthermore, there is a detection method using a two-transmitter two receiver. The algorithm is to set up two parallel antennas. The distance between the two receivers is divided by the time difference between the target vehicles and the two receivers. The speed is simple, but the disadvantage is that the distance between the two receivers is enough. Large (large), if the distance is shortened for the small size of the radar, the speed detection is not accurate enough.

A transmitter speed detector with a transmitter and a receiver is a practical method that can simultaneously take care of small size and accurate speed. The existing algorithm uses the calculation target to the receiver frequency difference to calculate the target vehicle speed. However, the disadvantage is that the lateral detection, the frequency difference detection requires a longer detection time, and longer During the time, the radar cross-sectional area of the target vehicle may have undergone drastic changes within the antenna detection range, resulting in a significant decrease in speed accuracy.

Therefore, the present invention provides a method for detecting a vehicle speed by a radar detector, which effectively overcomes the above problems by a method for detecting a transmitter and a receiver without requiring a large amount of calculation, and the specific architecture and implementation manner thereof will be detailed. Below.

The main object of the present invention is to provide a method for detecting a vehicle speed by a radar detector, which calculates the vehicle speed of the target by using the phase difference of the wavefront angle of the reflected wave received by the two receivers.

Another object of the present invention is to provide a radar detector for detecting a vehicle speed, which uses at least one transmitter and two receivers to take positions of two time points on a moving object of a target to calculate a target and a receiver. The distance, and the two phase angle difference between the target and the two receivers at the two time points, and calculating the vehicle speed of the target by using the distance between the two receivers and the wavelength of the emitted wave, without taking multiple time points The position is calculated multiple times.

In order to achieve the above object, the present invention provides a method for detecting a vehicle speed by a radar detector, which uses at least one transmitter to send a complex detection signal, and the second receiver receives a reflected wave reflected by the target, and thus, when the target When the object enters the detection area of the second receiver and senses the reflected wave of the detection signal, the two time points of the movement of the object and the position of the center point of the receiver are taken as two first distances, divided by the first distance. Obtaining a first speed of the target with a time difference; then substituting a trigonometric function to calculate a second distance of the target from one of the receivers at one of the time points; and finally, substituting the second distance into the first speed In the formula, the first speed is converted into the speed of the target to a receiver, that is, the actual vehicle speed of the target.

The purpose, technical content, features and effects achieved by the present invention will be more readily understood by the detailed description of the embodiments.

The invention provides a method for detecting a vehicle speed by a radar detector. The architecture of a transmitter and two receivers, or two transmitters and two receivers is used to quickly calculate the speed of the target vehicle in the simplest formula.

1 is a schematic diagram of detecting a vehicle speed in the present invention, including a transmitter 10 and two receivers 12a and 12b. The transmitter and receiver may be radars, and the transmitter 10 transmits a plurality of detection signals when there is a target object. Upon entering the detection area of the two receivers 12a, 12b, the receivers 12a, 12b receive the reflected waves reflected by the target. First, the phase angle difference of the reflected waves reflected by the receivers 12a, 12b on the target 14 is calculated. The calculation formula of the phase angle difference is Where λ is the wavelength of the transmitted wave of the receivers 12a, 12b, d is the horizontal distance between the receivers 12a, 12b, and θ is the angle of the wavefront of the reflected wave.

Next, as shown in FIG. 2, the position at two time points t _m and t _n in the linear motion trajectory of the object 14 is taken, which is a similar time point, and the center point of the two receivers 12a, 12b and t _m , t _n time point target 14 position to calculate the first center distance, including the distance from the target to the center point when R _m is t _m , R _n is the distance from the target to the center point when t _n , and then according to the time Point t _m , t _n the distance from the object to the vertical line of the intermediate point S _m , S _n , the estimated first speed is the following formula (1):

Then, by substituting the trigonometric function, the center point in the formula (1) is replaced with the position of the receiver, and the first distance of the object at one of the time points and one of the two receivers is calculated, as shown in FIG. , it is assumed to calculate the time point t _m, the distance to the target 14 of the receiver 12a to R _m1, the distance of the receiver 12b is R _m2, the angle 12a, 12b to a center point of the target wave front two receivers For θ _m , the relationship between R _m and R _{m1 is} calculated as in the following equation (2): Similarly, .

Then, the formula (2) is substituted into the formula (1) for calculating the first speed, and the first speed is converted into the speed of the target to the receiver, that is, the actual vehicle speed of the target, and the phase angle difference of the receiver is respectively multiplied. After the respective transmitted wave wavelength, the first distance and the phase angle difference are obtained by two products, the product is subtracted and multiplied by the wavelength of the emitted wave, and divided by the time difference and the second distance, as shown in the following equation (3):

When λ is much smaller than R _m or R _n , the above equation (3) can be omitted, and the phase angle difference of the receiver is multiplied by the respective first distance and then subtracted, and then the wavelength of the emitted wave is multiplied. And divide by the time difference and the second distance, so that the actual vehicle speed V is as follows (4):

Moreover, if the wavefront angle θ is extremely small, let R _m1 ≒R _n1 ≒R, R be the distance between the linear motion trajectory of the target 14 and the receiver, that is, the shortest distance of the receiver target, since R _m1 ≒R _n1 ≒ R, so formula (4) can be omitted again, the phase angle difference of the receiver is subtracted, multiplied by the vertical distance between the linear motion trajectory of the target and the center point of the receiver, multiplied by the wavelength of the transmitted wave, and divided Taking the time difference and the second distance, as shown in the following equation (5):

In view of the fact that the distance R _m of the target from the receiver is much larger than the distance d between the two receivers, the wavefront angle θ _m or θ _n is generally extremely small, and the formula of the formula (5) can be used to detect the vehicle speed. The difference between the speed of the vehicle and the speed of the unoptimized vehicle is negligible.

In summary, the method for detecting a vehicle speed by a radar detector is to calculate a phase difference between a target reflected wave and a second receiver by using a wavefront angle of the target, and instantaneously obtain two short time points. The position of the target, the time difference, the phase difference and the distance between the target and the receiver center point calculate the approximate vehicle speed, and then replace the center point with the receiver position, calculate the distance from the target to the receiver, and substitute the formula for calculating the approximate vehicle speed. In the middle, the actual vehicle speed is obtained, and the formula of the actual vehicle speed can be optimized to obtain the simplest formula, and the difference between the calculated result and the unoptimized is extremely small and negligible, so the radar can be used in the target vehicle. The cross-sectional area is within the range of the antenna detection, and the speed of the target is quickly calculated in a very short time without change, which has higher speed accuracy than the prior art.

The above is only the preferred embodiment of the present invention and is not intended to limit the scope of the present invention. Therefore, any changes or modifications of the features and spirits of the present invention should be included in the scope of the present invention.

10‧‧‧transmitter

12a, 12b‧‧‧ Receiver

14‧‧‧ Targets

FIG. 1 is a schematic diagram showing the phase difference in the method for detecting the vehicle speed by the radar detector of the present invention.

FIG. 2 is a schematic diagram of the second time point target to the center of the second receiver in the method for detecting the vehicle speed by the radar detector of the present invention.

FIG. 3 is a schematic diagram showing the distance from the target object to the two receivers in a method for detecting the vehicle speed by the radar detector of the present invention.

10. . . launcher

12a, 12b. . . receiver

14. . . Target

Claims (5)

A method for detecting a vehicle speed by a radar detector includes the following steps: at least one transmitter sends a transmission wave of a plurality of detection signals; a target enters a detection area of the second receiver, and senses a reflection of the detection signal The wave time, taking two first distances between the target and the receivers at two time points, and then calculating a phase angle difference by using the distance difference of the target from a long distance to the receivers, wherein The first distance is obtained by the first center distance of the target and the center point of the receivers at the time points plus the product of the phase angle difference and the wavelength of the emitted wave of one of the receivers; a second distance between the receivers, a time difference of the ones of the time points, the phase angle difference, and the wavelength of the emitted waves to obtain a velocity of the target; and when the second distance between the receivers is much smaller than When the target reaches the first distance of the receivers, the wavefront angle of the reflected wave is close to zero, and the calculation formula for calculating the velocity of the target can be optimized. The method for detecting a vehicle speed by the radar detector according to claim 1, further comprising: taking the two first center distances of the target point and a center point of the receivers at the two time points, and the first Multiplying the center distance by the phase angle difference and the wavelength of the emitted waves, and dividing by the time difference between the two time points and the second distance, a first speed is obtained, and the first center is replaced by the first distance. The distance is converted to the speed of the target for the receivers. The method for detecting a vehicle speed by the radar detector according to claim 1, wherein the calculation formula of the speed of the target is Where λ is the wavelength of the emitted wave of the receivers, d is the second distance between the receivers, and t _m and t _{n are} the two time points, and R _m1 and R _n1 are respectively a time point The first distances between the target and the receivers, Δψ _m , Δψ _n are the phase angle differences of the receivers, respectively. The method for detecting a vehicle speed by the radar detector according to claim 3, further comprising: when the angle of the wavefront of the reflected wave is close to zero, the formula for calculating the velocity of the target is optimized to The method for detecting a vehicle speed by the radar detector according to claim 3, further comprising: when a wavefront angle of the reflected wave is extremely small, and the first distance of the target object to the receiver is approximately equal to the target object. The shortest distance to the receivers, the formula for calculating the speed of the target can be optimized for the second time to Where R is the vertical distance of the linear motion trajectory of the target from one of the centers of the receivers.