High-precision ultrasonic ranging method adaptive to high-speed movement of sound source and high wind environment

Abstract

A high-precision ultrasonic ranging method that is adaptive to high-speed movement of a sound source and environmental strong winds, wherein a base is set at the n corners of an n-gon base, an ultrasonic probe is set on the base, n is a natural number greater than or equal to 3, there is a height difference between the n ultrasonic probes, the n ultrasonic probes have different transmitting ultrasonic frequencies, the n ultrasonic probes respectively transmit ultrasonic waves of different frequencies and monitor the received reflected signals, according to the calculation formula of the time interval, an optimization objective function is set, and the Newton method is used to iteratively solve the optimization problem to obtain the measured distance. The present invention provides a high-precision ultrasonic ranging method that is adaptive to high-speed movement of a sound source and environmental strong winds.

Description

Technical Field

[0001] The invention relates to an ultrasonic distance measurement method. Background Art

[0002] The industry mostly uses temperature compensation algorithms to implement ultrasonic ranging. Although the propagation speed of ultrasound is related to the temperature and humidity, the speed of sound is also affected by wind speed. Sound propagates in the air in the form of longitudinal waves, and wind is the flow of air flow. Naturally, medium displacement will affect the speed of sound. When the sound source moves at high speed, such as when a car is driving at high speed, it will cause the surrounding air flow to flow rapidly to form a strong wind. Assuming the car speed is 120 kilometers per hour, the air flow close to the car shell is almost at the same speed as the car, reaching 33 meters per second, which is almost 10% of the speed of sound. Since wind speed affects the speed of sound, this is why ultrasonic radar is used in fields such as vehicle-mounted radar and autonomous driving, mainly when parking, when the car speed is low or stationary.

[0003] like Figure 1 Since ultrasound has good directional propagation characteristics in the air, when the wind speed is at a non-parallel angle to the ultrasonic propagation direction, the parallelogram law can be used for decomposition and superposition. If v is the sound speed and u is the wind speed component parallel to the ultrasonic propagation direction, the true sound speed is

[0004] Traditional ultrasonic radar or ultrasonic ranging does not take into account the impact of wind speed on measurement accuracy. Summary of the invention

[0005] In order to overcome the shortcomings of existing ultrasonic ranging methods that do not consider the influence of wind speed and have low accuracy, the present invention provides a high-precision ultrasonic ranging method that is adaptive to high-speed movement of sound sources and environmental strong winds.

[0006] The technical solution adopted by the present invention to solve the technical problem is:

[0007] A high-precision ultrasonic ranging method that is adaptive to high-speed movement of a sound source and environmental strong winds, wherein a base is set at the n corners of an n-gon base, an ultrasonic probe is set on the base, n is a natural number greater than or equal to 3, there is a height difference between the n ultrasonic probes, the n ultrasonic probes have different transmitting ultrasonic frequencies, the n ultrasonic probes respectively transmit ultrasonic waves of different frequencies and monitor the received reflected signals, an optimization objective function is set according to a calculation formula for a time interval, and the Newton method is used to iteratively solve the optimization problem to obtain the measured distance.

[0008] Furthermore, n transceiver-transmitter integrated ultrasonic probes of the same specifications are used, and each probe is padded with fillers of different heights.

[0009] Furthermore, n ultrasonic probes are respectively raised to 0 cm, c cm, 2c cm, ..., (n-1)c cm, where c is a unit interval, and the measured distance is the distance between the ultrasonic probe raised to 0 cm and the target object.

[0010] Furthermore, the n ultrasonic probes emit ultrasonic frequencies which have octave differences in frequency.

[0011] Each transceiver probe starts monitoring timing after emitting ultrasound of a certain frequency, and the timing is terminated only when an echo of the transmitted frequency is received.

[0012] n is 4, and ultrasonic probes are set on the four bases of the square base. There is a height difference between the four ultrasonic probes. The four ultrasonic probes are raised by 0 cm, 4 cm, 8 cm, and 12 cm respectively. The four ultrasonic probes have different transmitting ultrasonic frequencies. The four ultrasonic probes transmit ultrasonic waves of different frequencies and monitor the received reflected signals, which are respectively denoted as t 0 ,t 1 ,t 2 and t 3 , s is the distance from the ultrasonic probe to the surface of the object being measured, v is the speed of sound, and u is the wind speed;

[0013] List the following equation,

[0014]

[0015]

[0016]

[0017]

[0018] Find the optimal objective function

[0019] Use Newton's method to iteratively solve this optimization problem:

[0020] Iteration initial value Iteration direction The iteration step coefficient ρ = 0.01, and the iteration formula is The iteration termination condition is In this way, the required measurement distance s is obtained through iteration.

[0021] This solution is the preferred solution. n can also take other values ​​such as 3, 5, 6, etc. The larger the value, the higher the accuracy, but the more complicated the calculation process.

[0022] The four ultrasonic probes respectively emit ultrasound with different frequency specifications. The ultrasonic probe with a height of 0 cm emits 20K Hz, the ultrasonic probe with a height of 4 cm emits 40K Hz, the ultrasonic probe with a height of 8 cm emits 80K Hz, and the ultrasonic probe with a height of 12 cm emits 160K Hz.

[0023] The present invention designs a high-precision distance measurement method under the assumption that the wind speed and wind direction are relatively constant in a short-term stable environment. This short-term stable wind speed environment exists in high-speed driving of cars or in most meteorological environments. Moreover, the solution designed in this case does not rely on the temperature compensation mechanism. Its basic principle is as follows:

[0024]

[0025] In the above formula, s is the distance from the ultrasonic probe to the surface of the object being measured, v is the speed of sound, u is the wind speed, and T represents the total duration of ultrasonic emission and reflection reception. The short-term environment with stable wind speed mentioned above means that it is assumed that the wind speed remains unchanged during a loop time of ultrasonic emission and reflection reception. This assumption is valid when a car is driving at high speed or in most meteorological environments. In addition, it can also be assumed that the wind speed can be considered constant in a small-scale 3D space. In the above formula, s, v, and u are all unknown, and only T is measured by the system.

[0026] It is particularly emphasized that, under normal circumstances, the movement of the sound source itself does not affect the speed of sound. What affects the speed of sound is the wind formed by the movement of the airflow driven by the high-speed movement of the sound source.

[0027] The beneficial effects of the present invention are mainly manifested in: high precision. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a schematic diagram of the effect of wind speed on the speed of sound.

[0029] Figure 2 It is a schematic diagram of a square matrix consisting of four transceiver-transmitting ultrasound probes of the same specifications. DETAILED DESCRIPTION

[0030] The present invention will be further described below in conjunction with the accompanying drawings.

[0031] Reference Figure 1 and Figure 2A high-precision ultrasonic ranging method that is adaptive to high-speed movement of sound sources and environmental strong winds, a base is set at the n corners of an n-gon base, an ultrasonic probe is set on the base, n is a natural number greater than or equal to 3, there is a height difference between the n ultrasonic probes, the n ultrasonic probes have different transmitting ultrasonic frequencies, the n ultrasonic probes respectively transmit ultrasonic waves of different frequencies and monitor the received reflected signals, according to the calculation formula of the time interval, the optimization objective function is set, and the Newton method is used to iteratively solve this optimization problem to obtain the measured distance.

[0032] This embodiment uses 4 transceiver integrated ultrasonic probes of the same specifications, which are arranged at the four corners of a square base and are padded with fillers of different heights, 0 cm, 4 cm, 8 cm and 12 cm respectively. They transmit ultrasound of different frequency specifications, for example, 20K Hz is transmitted when the padded probe is 0 cm high, 40K Hz is transmitted when the padded probe is 4 cm high, 80K Hz is transmitted when the padded probe is 8 cm high, and 160K Hz is transmitted when the padded probe is 12 cm high.

[0033] After the probe with a height of 0 cm emits 20K Hz ultrasound, the time interval for monitoring and receiving the 20K Hz reflected signal is recorded as t 0 After the probe with a height of 4 cm emits 40K Hz ultrasound, the time interval of monitoring and receiving the 40K Hz reflected signal is recorded as t 1 After the probe with a height of 8 cm emits 80K Hz ultrasound, the time interval of monitoring and receiving the 80K Hz reflected signal is recorded as t 2 After the probe with a height of 12 cm emits 160K Hz ultrasound, the time interval for monitoring and receiving the 160K Hz reflected signal is recorded as t 3 .

[0034] List the following equation,

[0035]

[0036]

[0037]

[0038]

[0039] Find the optimal objective function

[0040] Use Newton's method to iteratively solve this optimization problem: Iteration initial value Iteration direction The iteration step coefficient ρ = 0.01, and the iteration formula is The iteration termination condition is

[0041] In this way, the required measurement distance s is obtained through iteration.

[0042] This embodiment is a preferred solution, and n may also be other values ​​such as 3, 5, 6, etc. The larger the value, the higher the accuracy, but the more complicated the calculation process.

[0043] In this embodiment, each transceiver probe starts monitoring timing after emitting ultrasound of a certain frequency, and the timing is terminated only when an echo of the transmitted frequency is received. Here, since it is adapted to various relative displacement motion states such as the movement of the sound source and the movement of the surface of the ranging object, the frequency of the recovered ultrasound of the specified frequency is offset from the emission frequency (this is the Doppler effect). Since the multiple probes designed in my case emit sound waves of multiple frequencies, the intervals between adjacent frequencies are uniformly at least one time different. According to the Doppler effect calculation, as long as the relative motion displacement speed is within half the speed of sound, there will be no confusion (for example, if a 40K Hz transmitter uses the echo of a 20K Hz transmitter as its own echo, this confusion will not occur). Half the speed of sound is equivalent to a car speed of 600 kilometers per hour, and this limit is naturally accommodated by most applications.

Claims

1. A high-precision ultrasonic ranging method that is adaptive to high-speed movement of sound sources and high winds in the environment. It is characterized in that A base is set at the n corners of the base of an n-gon, and an ultrasonic probe is set on the base, n is a natural number greater than or equal to 3, there is a height difference between the n ultrasonic probes, the n ultrasonic probes have different transmitting ultrasonic frequencies, the n ultrasonic probes respectively transmit ultrasonic waves of different frequencies and monitor the received reflected signals, according to the calculation formula of the time interval, the optimization objective function is set, and the Newton method is used to iteratively solve the optimization problem to obtain the measured distance s, and the measured distance s is the distance between the ultrasonic probe with a pad height of 0 cm and the target object; n is 4, and ultrasonic probes are set on the four bases of the square base. There is a height difference between the four ultrasonic probes. The four ultrasonic probes are raised by 0 cm, 4 cm, 8 cm, and 12 cm respectively. The four ultrasonic probes have different transmitting ultrasonic frequencies. The four ultrasonic probes transmit ultrasonic waves of different frequencies and monitor the received reflected signals, which are respectively denoted as t 0 ,t 1 ,t 2 and t 3 , v is the speed of sound, u is the wind speed; List the following equation, Find the optimal objective function Use Newton's method to iteratively solve this optimization problem: Iteration initial value Iteration direction The iteration step coefficient ρ = 0.01, and the iteration formula is k = 0, 1, 2, 3, ...; The iteration termination condition is In this way, the required measurement distance s is obtained through iteration.

2. The high-precision ultrasonic ranging method according to claim 1, which is adaptive to the high-speed movement of the sound source and the high wind in the environment. It is characterized in that N transceiver-transmitter ultrasonic probes of the same specifications are used, and are respectively raised with fillers of different heights.

3. The high-precision ultrasonic ranging method according to claim 1 or 2, which is adaptive to high-speed movement of the sound source and high wind in the environment. It is characterized in that The ultrasonic frequencies emitted by n ultrasonic probes have different ranges.

4. The high-precision ultrasonic ranging method according to claim 1 or 2, which is adaptive to high-speed movement of the sound source and high wind in the environment. It is characterized in that Each ultrasonic probe starts monitoring timing after emitting ultrasound of a certain frequency, and the timing is terminated only when an echo of the transmitted frequency is received.

5. The high-precision ultrasonic ranging method according to claim 1, which is adaptive to high-speed movement of the sound source and high wind in the environment. It is characterized in that The four ultrasonic probes respectively emit ultrasound with different frequency specifications. The ultrasonic probe with a height of 0 cm emits 20K Hz, the ultrasonic probe with a height of 4 cm emits 40K Hz, the ultrasonic probe with a height of 8 cm emits 80K Hz, and the ultrasonic probe with a height of 12 cm emits 160K Hz.

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