An ultrasonic radar detection method and system for an irregular cylindrical obstacle

Abstract

The present invention discloses a method and system for detecting an ultrasonic radar of a heterogeneous columnar obstacle, including step S1: setting a first threshold and a second threshold based on the ultrasonic echo intensity; step S2: if the ultrasonic echo intensity is between the first threshold and the second threshold, then execute step S3; step S3: selecting a base point on the obstacle to construct a spherical model, the base point being the center of the sphere of the spherical model, presetting a plurality of feature points on the surface of the spherical model, obtaining the actual echo time when the ultrasonic wave reaches each feature point, calculating the initial distance between the ultrasonic radar and the feature point based on the actual echo time, and correcting the spherical model based on the initial distance to obtain the initial obstacle shape; step S4: correcting the initial distance between the ultrasonic radar and the feature point to obtain the final distance; through the present invention, columnar obstacles can be identified, the risk of collision between the vehicle and the heterogeneous obstacle is reduced, and the safety of the vehicle and pedestrians is ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of ultrasonic ranging, and particularly relates to a method and system for detecting an ultrasonic radar for an irregular cylindrical obstacle. Background Art

[0002] The reverse radar system is a safety assistance device for a vehicle when parking or reversing, and can inform the driver of the situation of surrounding obstacles by means of sound or a more intuitive display; in the existing reverse radar system, a plurality of ultrasonic radars are arranged around the vehicle body. After receiving the ultrasonic echoes emitted by itself and other radars, the ultrasonic radar comprehensively judges the position of the real obstacle by calculation.

[0003] However, for all current reverse radar system solutions when dealing with irregular-shaped or spherical obstacles, although the volume of the irregular-shaped obstacle is large enough to be detected by the ultrasonic radar, for example, a round rod-shaped obstacle, the effective reflection surface size of the obstacle is too small, resulting in the ultrasonic echo being too small to be filtered by the ultrasonic radar, or due to its shape, the reflection direction of the ultrasonic wave is changed, as Figure 1 shown, so that the signal cannot be received by any ultrasonic radar, thus affecting the recognition accuracy of the ultrasonic radar; if the sensitivity of the ultrasonic radar probe is increased or the filtering echo threshold is decreased, the ultrasonic waves reflected by the ground or the environment will surely be recognized, resulting in false alarms and affecting the normal driving of the driver; therefore, how to improve the recognition accuracy of the ultrasonic radar for obstacles has become an urgent technical problem to be solved. Summary of the Invention

[0004] To solve the above problems, the present invention provides a method and system for detecting an ultrasonic radar for an irregular cylindrical obstacle to solve the problems existing in the prior art.

[0005] To achieve the above object, the technical solution of a method for detecting an ultrasonic radar for an irregular cylindrical obstacle according to the present invention includes:

[0006] Step S1: Set a first threshold and a second threshold based on the ultrasonic echo intensity, and the first threshold is greater than the second threshold;

[0007] Step S2: The ultrasonic radar emits ultrasonic waves and receives the ultrasonic echoes generated after the ultrasonic waves encounter an obstacle. If the ultrasonic echo intensity is between the first threshold and the second threshold, then execute Step S3;

[0008] Step S3: Select a base point on the obstacle to construct a spherical model, where the base point is the center of the sphere of the spherical model. Preset a plurality of feature points on the surface of the spherical model, obtain the actual echo time when the ultrasonic wave reaches each feature point, calculate the initial distance between the ultrasonic radar and the feature point based on the actual echo time, and correct the spherical model based on the initial distance to obtain the initial shape of the obstacle.

[0009] Step S4: Correct the initial distance between the ultrasonic radar and the feature points to obtain the final distance.

[0010] Further, in the step S3, obtaining the initial obstacle shape includes the following steps:

[0011] Step S31: A plurality of feature points are arranged on the hemispherical side of the spherical model facing the ultrasonic radar;

[0012] Step S32: Based on the theoretical distances between the ultrasonic radar and each feature point, calculate the theoretical echo time after the ultrasonic wave reaches each feature point;

[0013] Step S33: Obtain the actual echo time after the ultrasonic wave reaches each feature point. If the actual echo time is less than the theoretical echo time, it indicates that the actual position of this feature point is closer to the ultrasonic radar. If the actual echo time is greater than the theoretical echo time, it indicates that the actual position of this feature point is farther from the ultrasonic radar;

[0014] Step S34: Calculate the actual positions of the feature points based on the actual echo time, and adjust the shape of the spherical model based on the actual positions of each feature point to complete the construction of the initial obstacle shape.

[0015] Further, in the step S3, sort and number each feature point based on the actual echo time of each feature point. Each feature point samples three signal cycles continuously to obtain three sampling distances of each feature point. The average value of the three sampling distances is used as the initial distance between the ultrasonic radar and the feature point.

[0016] Further, in the step S4, correcting the initial distance between the ultrasonic radar and the feature points includes the following steps:

[0017] Step S51: Establish a three-dimensional coordinate system and obtain the three-dimensional coordinates of three ultrasonic radars;

[0018] Step S52: Construct a coordinate equation of the actual coordinates of the feature points based on the initial distances between each ultrasonic radar and the feature points where a, b, and c are the three-dimensional coordinates of the feature points respectively, and λ1, λ2, k1, and k2 are preset constants respectively;

[0019] Step S53: Set an error threshold, and gradually change the value of c based on a preset gradient to solve the coordinate equation to obtain the coordinates of the feature points. If the distances between this coordinate and each ultrasonic radar are all less than the error threshold, then set this coordinate point as the coordinate point of the feature point.

[0020] Further, in step S33, a theoretical upper limit of the echo time is set. If the actual echo time of a feature point is greater than the theoretical upper limit of the echo time, the position of this feature point is not adjusted.

[0021] Further, the ultrasonic radar collects the first sampling value of the sine wave in the transmitted ultrasonic wave and the second sampling value of the sine wave in the ultrasonic echo, and calculates the accurate time difference between the ultrasonic wave emission and reception based on the first sampling value and the second sampling value.

[0022] Further, in step S4, after obtaining the initial distances between the ultrasonic radar and each feature point, the interval distances between each feature point are calculated continuously, and the shape of the obstacle is further specified based on the interval distances.

[0023] Further, in step S33, a plurality of feature points are arranged at the edge of the spherical model, and when the actual echo time of the ultrasonic wave reaching one of these feature points is less than the theoretical echo time, the positions of these feature points are not adjusted.

[0024] Further, in step S53, the initial value of c is 0, and the preset gradient is 0.01.

[0025] On the other hand, the present invention also provides a detection system for an ultrasonic radar of a heterogeneous cylindrical obstacle, which is used to implement a detection method for an ultrasonic radar of a heterogeneous cylindrical obstacle in the above technical solution. The system includes:

[0026] At least three ultrasonic radars, which are used to transmit ultrasonic waves and receive ultrasonic echoes generated after the ultrasonic waves encounter obstacles;

[0027] A construction module for constructing the spherical model;

[0028] A calculation module for calculating the actual distance between the ultrasonic radar and the obstacle based on the time difference between the ultrasonic wave emission time and the ultrasonic echo time.

[0029] Compared with the prior art, the beneficial effects of the present invention are at least as follows:

[0030] 1. In the present invention, after receiving the ultrasonic echo and determining the initial position of the obstacle, the ultrasonic radar constructs a spherical model based on the initial position, and then selects multiple virtual points on the spherical model as feature points. The ultrasonic radar verifies the actual positions of these feature points. If the ultrasonic radar receives the ultrasonic echo of the virtual feature point, it means that the virtual feature point exists. The shape of the spherical model is changed according to the actual position of the virtual feature point, thereby constructing the initial shape of the obstacle; finally, the distance between the ultrasonic radar and the feature point is corrected by the algorithm model to obtain the final distance; the present invention can identify cylindrical obstacles, reduce the risk of collision between vehicles and heterogeneous obstacles, and ensure the safety of vehicles and pedestrians.

[0031] 2. The spherical model is used as the preset model, so that ultrasonic waves in all directions can be assumed to be vertically incident, and the actual obstacle configuration can be obtained by simply changing the spherical surface, which has the advantages of fewer changes and low complexity. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is the reflection diagram of ultrasonic wave on the cylindrical obstacle;

[0033] Figure 2 This is a flow chart of a method for detecting an irregular column-shaped obstacle using ultrasonic radar according to the present invention;

[0034] Figure 3 Schematic diagram of constructing characteristic points of the present invention. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0036] It is understood that the terms "first", "second", etc. used in this application may be used herein to describe various elements, but unless otherwise specified, these elements are not limited by these terms. These terms are only used to distinguish a first element from another element. For example, without departing from the scope of this application, a first xx script may be referred to as a second xx script, and similarly, a second xx script may be referred to as a first xx script.

[0037] like Figure 2 As shown, a method for detecting an ultrasonic radar of a columnar obstacle comprises:

[0038] Step S1: setting a first threshold and a second threshold based on the ultrasonic echo intensity, wherein the first threshold is greater than the second threshold;

[0039] Specifically, the first threshold is set to The second threshold is set to where \(m_t\) is the time of \(m\) signal cycles of the ultrasonic wave, and the values of \(A\) and \(B\) can be set according to the actual situation.

[0040] Step S2: The ultrasonic radar emits ultrasonic waves and receives the ultrasonic echo generated after the ultrasonic waves encounter an obstacle. If the intensity of the ultrasonic echo is between the first threshold and the second threshold, then step S3 is executed;

[0041] Step S3: Select a base point on the obstacle to construct a spherical model. The base point is the center of the sphere of the spherical model. Preset multiple feature points on the surface of the spherical model, obtain the actual echo time when the ultrasonic wave reaches each feature point, calculate the initial distance between the ultrasonic radar and the feature point based on the actual echo time, and correct the spherical model based on the initial distance to obtain the initial obstacle shape;

[0042] Taking the spherical model as the preset model, it can be assumed that the ultrasonic waves in all directions are vertically incident, and the actual obstacle configuration can be obtained by simply changing the sphere, which has the advantages of few change times and low complexity.

[0043] Step S4: Correct the initial distance between the ultrasonic radar and the feature point to obtain the final distance.

[0044] In the present invention, after the ultrasonic radar receives the ultrasonic echo and determines the initial position of the obstacle, a spherical model is constructed based on this initial position, and then multiple virtual points are selected on the spherical model as feature points. The ultrasonic radar verifies the actual positions of these feature points. If the ultrasonic radar receives the ultrasonic echo of the virtual feature point, it means that the virtual feature point exists, and the shape of the spherical model is changed according to the actual position of the virtual feature point, so as to construct the initial shape of the obstacle; finally, the distance between the ultrasonic radar and the feature point is corrected through the algorithm model to obtain the final distance; through the present invention, cylindrical obstacles can be recognized, the risk of collision between the vehicle and the same-shaped obstacles is reduced, and the safety of the vehicle and pedestrians is ensured.

[0045] In step S3, obtaining the initial obstacle shape includes the following steps:

[0046] Step S31: A plurality of feature points are arranged on the hemispherical side of the spherical model facing the ultrasonic radar;

[0047] Step S32: Based on the theoretical distance between the ultrasonic radar and each feature point, calculate the theoretical echo time when the ultrasonic wave reaches each feature point;

[0048] Step S33: Obtain the actual echo time after the ultrasonic wave reaches each feature point. If the actual echo time is less than the theoretical echo time, it indicates that the actual position of this feature point is closer to the ultrasonic radar; if the actual echo time is greater than the theoretical echo time, it indicates that the actual position of this feature point is farther from the ultrasonic radar.

[0049] Step S34: Calculate the actual position of the feature point based on the actual echo time, and adjust the shape of the spherical model based on the actual positions of each feature point to complete the construction of the initial obstacle shape.

[0050] As Figure 3 shown, select multiple feature points on the side of the spherical model facing the ultrasonic radar, and sort and number each feature point based on the actual echo time. Before step S33, construct a feature point set G = [α1, α2,... α n , where α n is the nth feature point. If the ultrasonic echo intensity of the feature point is between the first threshold and the second threshold, set the value of the corresponding feature point to 1, otherwise set it to 0; after completing step S33, read the feature points with a value of 1, and then construct the specific shape of the obstacle according to the actual echo time.

[0051] In step S3, sort and number each feature point based on the actual echo time of each feature point. Each feature point samples three signal cycles continuously to obtain three sampling distances of each feature point Take the average of the three sampling distances as the initial distance between the ultrasonic radar and the feature point. By sampling multiple signal cycles and taking the average, a more accurate ranging result can be obtained.

[0052] In step S4, the correction of the initial distance between the ultrasonic radar and the feature point includes the following steps:

[0053] Step S51: Establish a three-dimensional coordinate system and obtain the three-dimensional coordinates of the three ultrasonic radars;

[0054] Step S52: Construct a coordinate equation of the actual coordinates of the feature point based on the initial distances between each ultrasonic radar and the feature point where a, b, and c are the three-dimensional coordinates of the feature point, and λ1, λ2, k1, and k2 are preset constants respectively;

[0055] Step S53: Set an error threshold, and gradually change the value of c based on the preset gradient to solve the coordinate equation to obtain the coordinates of the feature point. If the distances between this coordinate and each ultrasonic radar are all less than the error threshold, set this coordinate point as the coordinate point of the feature point.

[0056] Specifically, a three-dimensional rectangular coordinate system is established with the center of the spherical model as the origin. Assuming the feature point is P with coordinates P(a, b, c), and the coordinates of the three ultrasonic radars are S1(x1, y1, z1), S2(x2, y2, z2), and S3(x3, y3, z3) respectively. The distances of the three ultrasonic radars from the origin are all R, the radius of the spherical model is r, θ1 is the angle between point P and the origin on the horizontal plane, and θ2 is the angle between point P and the origin on the vertical plane. Then the coordinates of point P are (rcosθ1cosθ2, rsinθ1cosθ2, rsinθ2); First, each ultrasonic radar obtains the distances d1, d2, and d3 from point P. According to the coordinate distance formula in the coordinate system:

[0057] After transforming this formula, we get

[0058] Further transformation gives:

[0059] Then let

[0060] Simplification gives

[0061] Then the values of λ1, λ2, k1, and k2 can be determined by this formula; When the value of c is 0, calculate the values of a and b, and then obtain the coordinates of point P. Then calculate the distances d1', d2', and d3' from point P to each ultrasonic radar based on the coordinates of point P. If |d1 - d1'| ≤ 0.01, |d2 - d2'| ≤ 0.01, and |d3 - d3'| ≤ 0.01 are satisfied simultaneously, then set these coordinates as the coordinates of point P. Otherwise, increase the value of c and continue the calculation until the coordinates that meet the conditions are obtained.

[0062] In step S33, set the upper limit of the theoretical echo time. If the actual echo time of the feature point is greater than the upper limit of the theoretical echo time, then do not adjust the position of the feature point. If the ultrasonic wave reaching this position is still detected by the ultrasonic radar after being deflected, but the echo time is long, resulting in the ultrasonic radar misjudging the actual position of the feature point and causing a collision risk for the vehicle, this setting can avoid the occurrence of this problem.

[0063] The ultrasonic radar collects the first sampling value of the sine wave in the transmitted ultrasonic wave and the second sampling value of the sine wave in the ultrasonic echo, and calculates the accurate time difference between the ultrasonic wave transmission and reception based on the first sampling value and the second sampling value.

[0064] For example, at time t0, the frequency of the ultrasonic wave emitted by this vehicle model is 40KHZ, such as emitting 10 square wave strings with a period of 25us. If 5 data are sampled in one cycle wave, the sampling period is τ = 50us, then 50 data are sampled for 10 cycles.

[0065] Let the distance range between the ultrasonic radar and the obstacle be (R + R min , R + R max ), the ultrasonic speed is 346.7m / s, and let The ultrasonic echo is sampled φ1 - φ = φ' times starting from t0. Let the array R i [φ'] be the sampling value of the data received in the first sampling period S i , the array R j [φ'] be the sampling value of the data received in the second sampling period S j , the array R j [φ'] be the sampling value of the data received in the third sampling period S j . The peak value φ i , φ j , φ k of each sampling period is obtained from the above sampling value and the received sampling value, and the accurate time difference of each sampling period is calculated by (φ i + φ)τ = t i , (φ j + φ)τ = t j , (φ k + φ)τ = t k .

[0066] In step S4, after obtaining the initial distance between the ultrasonic radar and each feature point, continue to calculate the interval distance between each feature point, and further specify the shape of the obstacle based on the interval distance.

[0067] In step S33, a plurality of feature points are arranged at the edge of the spherical model. When the actual echo time of the ultrasonic wave reaching one of the feature points in this part is less than the theoretical echo time, the position of the feature points in this part is not adjusted. For example, for the feature point numbered 32 in the figure, when the value of one of the feature points numbered 32 is 1, the values of all the feature points numbered 32 are set to 1, so as to ensure the safety of reversing.

[0068] In step S53, the initial value of c is 0, and the preset gradient is 0.01.

[0069] On the other hand, the present invention also provides a detection system for an ultrasonic radar of a non-cylindrical obstacle, which is used to implement a detection method for an ultrasonic radar of a non-cylindrical obstacle in the above technical solution. The system includes:

[0070] At least three ultrasonic radars are provided. The ultrasonic radars are used to emit ultrasonic waves and receive the ultrasonic echoes generated after the ultrasonic waves encounter obstacles.

[0071] A construction module for constructing a spherical model.

[0072] A calculation module for calculating the actual distance between the ultrasonic radar and the obstacle based on the time difference between the ultrasonic wave emission time and the ultrasonic echo time.

[0073] The slave feature group contains multiple slave feature points. The master feature point is located at the point on the spherical model with the shortest distance towards the ultrasonic radar. The slave feature points within the same feature group are located on the same circle and are all centered on the master feature point.

[0074] Sort and number each feature point based on the actual echo time, and construct an array G = [α1, α2, … α n , where if the actual echo time of the feature point is greater than or equal to the theoretical echo time, the value of the feature point in the array is set to 1, otherwise it is set to 0.

[0075] Those of ordinary skill in the art can understand that all or part of the processes in the methods of the above embodiments can be completed by instructing relevant hardware through a computer program. The above program can be stored in a non-volatile computer-readable storage medium. When the program is executed, it can include the processes of the embodiments of the above methods. Among them, any reference to a memory, storage, database, or other medium used in the various embodiments provided in the present application can include non-volatile and / or volatile memories. Non-volatile memories can include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), or flash memory. Volatile memories can include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in various forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDR SDRAM), enhanced SDRAM (ESDRAM), synchronous link (Synchlink) DRAM (SLDRAM), memory bus (Rambus) direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM), etc.

[0076] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0077] The above-mentioned embodiments only represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the patent for the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several deformations and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent for the present invention shall be subject to the appended claims.

[0078] The above is only the preferred embodiment of the present invention and is not used to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An ultrasonic radar detection method for an irregular columnar obstacle, characterized in that Including: Step S1: Set a first threshold and a second threshold based on the ultrasonic echo intensity, where the first threshold is greater than the second threshold; Step S2: The ultrasonic radar emits ultrasonic waves and receives the ultrasonic echoes generated after the ultrasonic waves encounter an obstacle. If the ultrasonic echo intensity is between the first threshold and the second threshold, then execute Step S3; Step S3: Select a base point on the obstacle to construct a spherical model. The base point is the center of the sphere of the spherical model. Preset multiple feature points on the surface of the spherical model. Obtain the actual echo time when the ultrasonic wave reaches each feature point. Calculate the initial distance between the ultrasonic radar and the feature point based on the actual echo time. Modify the spherical model based on the initial distance to obtain the initial obstacle shape; Step S4: Modify the initial distance between the ultrasonic radar and the feature point to obtain the final distance.

2. The ultrasonic radar detection method for a heterogeneous columnar obstacle according to claim 1, wherein In the said Step S3, obtaining the initial obstacle shape includes the following steps: Step S31: Set multiple feature points on the hemispherical side of the spherical model facing the ultrasonic radar; Step S32: Calculate the theoretical echo time when the ultrasonic wave reaches each feature point based on the theoretical distance between the ultrasonic radar and each feature point; Step S33: Obtain the actual echo time when the ultrasonic wave reaches each feature point. If the actual echo time is less than the theoretical echo time, it indicates that the actual position of this feature point is closer to the ultrasonic radar. If the actual echo time is greater than the theoretical echo time, it indicates that the actual position of this feature point is farther from the ultrasonic radar; Step S34: Calculate the actual position of the feature point based on the actual echo time. Adjust the shape of the spherical model based on the actual positions of each feature point to complete the construction of the initial obstacle shape.

3. A method for detecting an ultrasonic radar of a heterogeneous columnar obstacle according to claim 1, characterized in that, In the step S3, each feature point is sorted and numbered based on the actual echo time of each feature point, and three signal cycles are continuously sampled for each feature point to obtain three sampling distances of each feature point. The average value of the three sampling distances is used as the initial distance between the ultrasonic radar and the feature point.

4. A method for detecting an ultrasonic radar of a heterogeneous columnar obstacle according to claim 1, characterized in that, In the said Step S4, modifying the initial distance between the ultrasonic radar and the feature point includes the following steps: Step S51: Establish a three-dimensional coordinate system and obtain the three-dimensional coordinates of three ultrasonic radars; Step S52: Construct a coordinate equation of the actual coordinates of the feature points based on the initial distances between each ultrasonic radar and the feature points where a, b, and c are the three-dimensional coordinates of the feature points, and λ1, λ2, k1, and k2 are preset constants respectively; Step S53: Set an error threshold, and gradually change the value of c based on a preset gradient to solve the coordinate equation to obtain the coordinates of the feature point. If the distance between this coordinate and each ultrasonic radar is less than the error threshold, then set this coordinate point as the coordinate point of the feature point.

5. A method for detecting an ultrasonic radar of an irregular columnar obstacle according to claim 2, characterized in that, In the said Step S33, set an upper limit for the theoretical echo time. If the actual echo time of the feature point is greater than the upper limit of the theoretical echo time, then do not adjust the position of this feature point.

6. The method for detecting an ultrasonic radar of an irregular columnar obstacle according to claim 3, wherein The ultrasonic radar collects the first sampling value of the sine wave in the emitted ultrasonic wave and the second sampling value of the sine wave in the ultrasonic echo, and calculates the accurate time difference between the ultrasonic wave emission and reception based on the first sampling value and the second sampling value.

7. A method for detecting an ultrasonic radar of an irregular columnar obstacle according to claim 1, characterized in that In the said Step S3, after obtaining the initial distance between the ultrasonic radar and each feature point, continue to calculate the interval distance between each feature point, and further specify the obstacle shape based on the interval distance.

8. A method for detecting an ultrasonic radar of a heterogeneous columnar obstacle according to claim 2, characterized in that, In the said Step S33, multiple feature points are set at the edge of the spherical model, and when the actual echo time when the ultrasonic wave reaches one of the multiple feature points is less than the theoretical echo time, do not adjust the positions of the multiple feature points.

9. A method for detecting an ultrasonic radar of an irregular columnar obstacle according to claim 4, characterized in that In step S53, the initial value of c is 0, and the preset gradient is 0.

01.

10. An ultrasonic radar detection system for heterogeneous cylindrical obstacles, which is used to implement an ultrasonic radar detection method for heterogeneous cylindrical obstacles according to any one of claims 1 to 9, characterized in that Including: At least three ultrasonic radars, which are used to emit ultrasonic waves and receive the ultrasonic echoes generated after the ultrasonic waves encounter obstacles; A construction module for constructing a spherical model; A calculation module for calculating the actual distance between the ultrasonic radar and the obstacle based on the time difference between the ultrasonic wave emission time and the ultrasonic echo time.

Images