Same-frequency interference resisting algorithm for ultrasonic ranging

Abstract

The invention provides an anti-co-frequency interference algorithm for ultrasonic ranging, which comprises the following steps of: sending ultrasonic pulses to a space provided with a plurality of obstacles, and sampling echoes returned by the obstacles; obtaining obstacle data by calculating echoes, wherein the obstacle data comprises but is not limited to echo height, echo width and duty ratio thereof; according to the obstacle data, performing sectional filtering processing on interference variables in echoes; and adopting a plurality of prime number random arrays to carry out dislocation processing on the ultrasonic pulses and the echoes, adding random difference assignment, and repeating the steps. According to the invention, the interference variable in the echo signal is subjected to sectional filtering processing, the waveform is sent and received by using the prime number random array for dislocation processing, and the random difference value assignment is added; and the effect of effectively filtering ultrasonic co-frequency interference and external interference signals on the premise of not influencing the response speed of ultrasonic ranging to the greatest extent is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of ultrasonic radar ranging, and in particular to an anti-co-frequency interference algorithm for ultrasonic ranging. Background Art

[0002] Ultrasonic radar ranging is a technology that uses ultrasonic radar to measure distance. It is widely used in the fields of reversing, parking assistance and drone flight ranging. Its working principle is to calculate the distance of obstacles based on the echo time difference by emitting and receiving ultrasonic waves of specific frequencies, such as 40kHz, 48kHz or 58kHz. When the distance is too close, the ultrasonic radar will trigger the alarm device and sound an alarm to remind the driver to ensure safe operation. Therefore, the accuracy and response speed of ultrasonic ranging are crucial. However, in the application process of ultrasonic radar to measure distance, it is often easy to produce false alarms and unstable measurements due to the existence of co-frequency interference, which will have an adverse effect on the performance and quality of vehicles and other products.

[0003] Co-channel interference refers to the interference caused by the useless signal with the same carrier frequency as the useful signal to the reception of the useful signal with the same frequency. The usual solution to co-channel interference is to use a filtering algorithm to filter the co-channel interference. However, the existing filtering technology and algorithms often cannot filter out the co-channel interference cleanly; some will sacrifice the response speed in order to increase the filtering strength, which seriously affects the ranging performance of the product.

[0004] Therefore, an algorithm is needed that can effectively filter ultrasonic co-frequency interference and external interference signals without affecting the ultrasonic ranging response speed. Summary of the invention

[0005] The present invention provides an anti-co-frequency interference algorithm for ultrasonic ranging, which is mainly used to solve the problems that the existing filtering technology and algorithm cannot filter out the co-frequency interference cleanly, or sacrifice the reaction speed to increase the filtering strength, which affects the product performance, so as to achieve the effect of effectively filtering the ultrasonic co-frequency interference and external interference signals without affecting the ultrasonic ranging reaction speed to the greatest extent.

[0006] The present invention achieves the above-mentioned purpose through the following technical solutions:

[0007] An anti-co-frequency interference algorithm for ultrasonic ranging, comprising:

[0008] S1: Send ultrasonic pulses to a space with several obstacles, and sample the echoes returned by the obstacles.

[0009] S2: Obtain obstacle data by calculating the echo, wherein the obstacle data includes but is not limited to echo height, echo width and its duty cycle.

[0010] S3: Performing segmented filtering processing on the interference amount in the echo according to the obstacle data.

[0011] S4: Use multiple groups of prime number random arrays to perform dislocation processing on the ultrasonic pulse and echo, add random difference assignment, and repeat step S1.

[0012] A further solution is that the segmented filtering process in step S3 includes the following steps:

[0013] S31: Obtain an empirical value of the amount of interference existing in ultrasonic ranging in the space, and set segment intervals with the maximum and minimum values ​​of the empirical value as endpoints.

[0014] S32: Segment the segmented interval, and set different filtering algorithms according to the characteristics of the interference in different segments.

[0015] S33: Determine whether there is an interference signal in the echo according to the obstacle data, and if so, execute the next step; if not, execute step S4.

[0016] S34: Determine the segment to which the interference signal belongs, and perform filtering processing according to the filtering algorithm corresponding to the segment to which the interference signal belongs.

[0017] A further solution is that the empirical value of the interference amount is 2-31 dB, and the segment interval is [2, 31].

[0018] A further solution is to divide the segmented interval into a first interval segment, a second interval segment and a third interval segment, wherein the first interval segment is endpoint 31, the second interval segment is (5, 31), and the third interval segment is [2, 5].

[0019] A further solution is that the characteristics of the interference amount corresponding to the first interval segment include:

[0020] Characteristic 1: The interference amount overlaps with the echo of a relatively large obstacle.

[0021] Characteristic 2: The interference amount overlaps with the echo of an obstacle that is relatively close.

[0022] The characteristic of the interference amount corresponding to the second interval is:

[0023] Characteristic 3: The obstacle data exists in the interference amount.

[0024] The characteristic of the interference amount corresponding to the third interval is:

[0025] Characteristic 4: The interference quantity overlaps with the command signal and the unstable signal.

[0026] A further solution is that the filtering algorithm for the interference value of the first interval includes:

[0027] For the interference quantity with characteristic 1, the interference signal is determined by comparing the unstable characteristics of the interference quantity for multiple times, and the interference signal is filtered out.

[0028] For the interference quantity with characteristic 2, the unstable signal is filtered out by limiting the echo size of the obstacle.

[0029] A further solution is that the filtering algorithm for the interference value of the second interval is:

[0030] S321: Record the obstacle data and its timestamp calculated from two consecutive rounds of echoes.

[0031] S322: Calculate the distance change of the obstacle based on the obstacle data recorded in the front and rear rounds, and determine whether the obstacle has moved based on the distance change.

[0032] S323: If no displacement occurs, determine the interference signal according to the echo attenuation characteristic, and filter out the interference signal; if displacement occurs, execute step S324.

[0033] S324: Calculate the relative movement speed of the obstacle according to the distance change and the timestamp, determine the interference signal by judging whether the relative movement speed meets the obstacle movement condition, and filter out the interference signal.

[0034] A further solution is to further include S325: obtaining the directional characteristics of the obstacle, determining the interference signal by judging whether the directional characteristics of the two rounds of echoes are consistent, and filtering out the interference signal.

[0035] A further solution is that the filtering algorithm for the interference value in the third interval is:

[0036] For interference quantities with characteristic 4, all interference quantities are regarded as interference signals and filtered out.

[0037] A further solution is that when it is determined in step S33 that there is an interference signal in the echo, the following steps are further performed:

[0038] S331: Setting a field protection value, and using the field protection value to replace the disturbed echo signal value to protect the field cache data.

[0039] It can be seen that the present invention has the following beneficial effects:

[0040] 1. The present invention processes the co-frequency interference signal in a segmented manner and performs targeted and effective filtering on the interference signal according to the co-frequency interference characteristics shown in different ultrasonic ranging application scenarios, so as to achieve the goal of effectively filtering out the interference amount and optimizing the product performance without sacrificing the ultrasonic radar reaction speed while improving the stability of the ultrasonic ranging product.

[0041] 2. The present invention needs to shield the interference signal when it exists, and by setting a field protection value, the field protection value is used to replace the interfered signal value, thereby achieving the effect of stabilizing the interactive interface and data.

[0042] 3. The present invention uses multiple groups of prime random arrays to perform staggered processing on a complete round of ultrasonic pulse sending and receiving waveforms and adds random difference assignments, so as to maximize the random characteristics of the system operation and avoid the conflict of co-frequency interference characteristics.

[0043] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 The present invention is a flow chart of an anti-co-frequency interference algorithm for ultrasonic ranging.

[0045] Figure 2 It is a flow chart of the present invention for performing segmented filtering processing on echoes.

[0046] Figure 3-Figure 6 is the ranging data waveform under normal circumstances without using the anti-co-channel interference algorithm of the present invention, where: Figure 3 It is the obstacle distance data and interference waveform data waveform diagram outputted without obstacles and with co-frequency interference; Figure 4 It is the obstacle distance data and interference waveform data waveform diagram output when there are fixed obstacles and co-frequency interference; Figure 5 It is the obstacle distance data and interference waveform data waveform diagram output when there is a moving obstacle and co-frequency interference; Figure 6 It is a waveform diagram of obstacle distance data and interference waveform data output when there is a moving obstacle but no co-frequency interference.

[0047] Figure 7-Figure 10 It is the ranging data waveform obtained by using the anti-co-frequency interference algorithm of the present invention, wherein:

[0048] Figure 7 It is the obstacle distance data and interference waveform data waveform diagram outputted without obstacles and with co-frequency interference; Figure 8 It is the obstacle distance data and interference waveform data waveform diagram output when there are fixed obstacles and co-frequency interference; Fig. 9It is the obstacle distance data and interference waveform data waveform diagram output when there is a moving obstacle and co-frequency interference; Fig.10 It is a waveform diagram of obstacle distance data and interference waveform data output when there is a moving obstacle but no co-frequency interference. DETAILED DESCRIPTION

[0049] In order to make the purpose, technical solution and advantages of the embodiment of the present invention clearer, the technical solution of the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings of the embodiment of the present invention. Obviously, the described embodiment is a part of the embodiment of the present invention, not all of the embodiments. Based on the described embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0050] An embodiment of an anti-co-frequency interference algorithm for ultrasonic ranging

[0051] See also Figure 1 The present invention relates to an anti-co-frequency interference algorithm for ultrasonic ranging, comprising:

[0052] S1: Send ultrasonic pulses to a space with several obstacles, and sample the echoes returned by the obstacles.

[0053] S2: Obtain obstacle data by calculating the echo, wherein the obstacle data includes but is not limited to echo height, echo width and its duty cycle.

[0054] S3: Performing segmented filtering processing on the interference amount in the echo according to the obstacle data.

[0055] S4: Use multiple groups of prime number random arrays to perform dislocation processing on the ultrasonic pulse and echo, add random difference assignment, and repeat step S1.

[0056] Specifically, this embodiment uses two sets of prime number random arrays as follows:

[0057] {1,7,13,17,23,31,37,41}, {1,2,3,5,7,11,13,15}.

[0058] In this embodiment, the segmented filtering process in step S3 includes the following steps:

[0059] S31: Obtain an empirical value of the amount of interference existing in ultrasonic ranging in the space, and set segment intervals with the maximum and minimum values ​​of the empirical value as endpoints.

[0060] S32: Segment the segmented interval, and set different filtering algorithms according to the characteristics of the interference in different segments.

[0061] S33: Determine whether there is an interference signal in the echo according to the obstacle data, and if so, execute the next step; if not, execute step S4.

[0062] S34: Determine the segment to which the interference signal belongs, and perform filtering processing according to the filtering algorithm corresponding to the segment to which the interference signal belongs.

[0063] In this embodiment, the empirical value of the interference amount is 2-31 dB, and the segment interval is [2, 31].

[0064] In this embodiment, the segmented interval is divided into a first interval segment, a second interval segment and a third interval segment, the first interval segment is the endpoint 31, the second interval segment is (5, 31), and the third interval segment is [2, 5].

[0065] In this embodiment, the characteristics of the interference amount corresponding to the first interval include:

[0066] Characteristic 1: The interference amount overlaps with the echo of a relatively large obstacle.

[0067] Specifically, in this embodiment, the relatively large obstacle refers to an obstacle that is larger than the volume of the distance measuring product. For example, for a sweeping robot, walls, cabinets, etc. are large obstacles.

[0068] Characteristic 2: The interference amount overlaps with the echo of an obstacle that is relatively close.

[0069] Specifically, in this embodiment, the relatively close obstacle refers to an obstacle that is too close to the ranging product and interferes with the ranging of obstacles at a normal distance.

[0070] The characteristic of the interference amount corresponding to the second interval is:

[0071] Characteristic 3: The obstacle data exists in the interference amount.

[0072] The characteristic of the interference amount corresponding to the third interval is:

[0073] Characteristic 4: The interference quantity overlaps with the command signal and the unstable signal.

[0074] Specifically, when this embodiment is applied to ultrasonic ranging of a sweeping robot, the command signal is a sweeping signal, and the sweeping signal and the unstable signal are both regarded as interference signals and filtered out.

[0075] In this embodiment, the filtering algorithm for the first interval interference includes:

[0076] For the interference quantity with characteristic 1, the interference signal is determined by comparing the unstable characteristics of the interference quantity for multiple times, and the interference signal is filtered out.

[0077] For the interference quantity with characteristic 2, the unstable signal is filtered out by limiting the echo size of the obstacle.

[0078] See also Figure 2 In this embodiment, the filtering algorithm for the interference value of the second interval is:

[0079] S321: Record the obstacle data and its timestamp calculated from two consecutive rounds of echoes.

[0080] Specifically, step S321 in this embodiment further includes the following steps:

[0081] S3211: Determine the echo height, echo width and total echo duty cycle. If the echo height is less than 5 and the echo width is less than 150us, store the first echo width of two consecutive obstacles through FIFO.

[0082] Specifically, this embodiment updates obstacle data of echoes after the first round of obstacles according to a first-in-first-out queue, i.e., FIFO, and the obstacle data includes waveform information, number of echoes, echo width, echo height, obstacle distance, and polling time interval.

[0083] S3212: Determine whether the current obstacle exists stably. If not, update the field data cache, discard the current data, and return to the last saved field data; if stable, execute the next step.

[0084] S3213: Determine whether the echo height is greater than the maximum value, if so, execute the next step; if not, determine whether the echo height reaches the maximum value. If four consecutive cached echo heights reach the maximum value, FIF0 stores four rounds of obstacle echo widths, obstacle distances, and current timestamps, and executes the next step, otherwise discard the data and return to the last saved field data.

[0085] Specifically, when the embodiment determines that the duty cycle of the obstacle echo is greater than 30%, the echo is an echo of the obstacle being a wall.

[0086] S3214: Determine whether the height error of the two echoes is greater than the upper limit value. If so, discard the current data and return to the last saved field data; if not, execute step S322.

[0087] S322: Calculate the distance change of the obstacle based on the obstacle data recorded in the front and rear rounds, and determine whether the obstacle has moved based on the distance change.

[0088] Specifically, this embodiment can determine whether there is an obstacle and whether a relative displacement occurs by calculating the distance change of the obstacle twice before and after. If the change is 0, no displacement occurs; otherwise, displacement occurs.

[0089] S323: If no displacement occurs, determine the interference signal according to the echo attenuation characteristic, and filter out the interference signal; if displacement occurs, execute step S324.

[0090] Specifically, step S323 in this embodiment further includes the following steps:

[0091] S3231: Determine whether the subsequent obstacle echo is smaller than the current obstacle echo. If so, update the obstacle distance and update the on-site saved data; if not, execute the next step.

[0092] S3232: Determine whether the larger value echo is at a fixed position away from the obstacle. If so, update the obstacle distance and the on-site saved data; if not, discard the current data and return to the last saved on-site data.

[0093] Specifically, in this embodiment, the subsequent echo width D1 is compared with the current echo width D0 of the obstacle. If D1>D0, the error between the subsequent echo interval of the current round of obstacles and the subsequent echo interval of the previous round of obstacles must be less than 20us, otherwise it is determined as an interference signal and filtered out.

[0094] Specifically, in this embodiment, the first three rounds of distance data all execute step S3232. If no displacement occurs, the obstacle distance is updated and the on-site saved data is updated; otherwise, it is identified as an interference signal.

[0095] S324: Calculate the relative movement speed of the obstacle according to the distance change and the timestamp, determine the interference signal by judging whether the relative movement speed meets the obstacle movement condition, and filter out the interference signal.

[0096] Specifically, this embodiment uses a sensor to sense the relative movement direction of the obstacle, and the relative movement direction includes approaching and moving away.

[0097] Specifically, step S324 in this embodiment further includes the following steps:

[0098] S3241: Calculate the time difference t0 and distance change detaDis between the current round of echoes and the previous round using the timestamp stored in FOFO, and store their relative motion direction characteristics.

[0099] S3242: Calculate the first relative motion speed speed0=detaDis / t0 according to the formula. If speed0<15km / h, execute the next step. Otherwise, determine it as an interference signal and filter it out.

[0100] S3243: Calculate the time difference t1 and distance change detaDisl between the previous echo wave and the previous previous echo wave using the timestamp stored in FOFO.

[0101] S3244: Determine whether the directional characteristics of the current round of echoes are consistent with those of the previous round. If they are consistent, execute the next step; if they are inconsistent, determine that they are interference signals and filter them out;

[0102] S3245: Calculate the second relative motion speed speed1=detaDis1 / t1 according to the formula. If speed1<15km / h, execute the next step. Otherwise, determine it as an interference signal and filter it out.

[0103] S3246: Calculate the speed error Deta Speed ​​between the first relative motion speed speed0 and the second relative motion speed speed1. If Deta Speed<0.8 km / h, update the obstacle distance and the on-site saved data; otherwise, determine it as an interference signal and filter it out.

[0104] Specifically, this embodiment uses a free timing counter inside the chip to store and calculate time values ​​at different times to form a timestamp, and the timestamp is used to calculate the displacement characteristics and vector characteristics of the obstacle.

[0105] In this embodiment, the process further includes S325: obtaining the directional characteristics of the obstacle, determining the interference signal by judging whether the directional characteristics of the two rounds of echoes are consistent, and filtering out the interference signal.

[0106] In this embodiment, the filtering algorithm for the interference value of the third interval is:

[0107] For interference quantities with characteristic 4, all interference quantities are regarded as interference signals and filtered out.

[0108] In this embodiment, when it is determined in step S33 that there is an interference signal in the echo, the following steps are further performed:

[0109] S331: Setting a field protection value, and using the field protection value to replace the disturbed echo signal value to protect the field cache data.

[0110] See also Figure 3-10 Specifically, this embodiment verifies the anti-co-channel interference algorithm of the present invention through comparative experiments.

[0111] The experimental tools include a laptop computer, CANOE, a 12V regulated power supply, two sets of ultrasonic radars with the same working frequency, a test bench, and 75cm and 50cm diameter PVC pipes.

[0112] The experimental environment was an open space of 2-3 m at room temperature of 20-25 °C.

[0113] The experimental method is to use two sets of ultrasonic radars with the same working frequency, arranged on a stand with an interval of 1-2m, and the ultrasonic sensors work symmetrically with each other. Use CANOE to connect to the computer, output obstacle distance data and interference waveform data, and observe and record the results.

[0114] First, the same-frequency interference algorithm software of the present invention was burned into the ultrasonic radar for testing and the results were recorded. Figure 3-6 As shown, where: Figure 3 It is the obstacle distance data and interference waveform data waveform diagram outputted without obstacles and with co-frequency interference; Figure 4 It is the obstacle distance data and interference waveform data waveform diagram output when there are fixed obstacles and co-frequency interference; Figure 5 It is the obstacle distance data and interference waveform data waveform diagram output when there is a moving obstacle and co-frequency interference; Figure 6 It is a waveform diagram of obstacle distance data and interference waveform data output when there is a moving obstacle but no co-frequency interference.

[0115] Then, burn the same-frequency interference algorithm software of the present invention into the ultrasonic radar for testing and record the results. Figure 7-10 As shown, where: Figure 7 It is the obstacle distance data and interference waveform data waveform diagram outputted without obstacles and with co-frequency interference; Figure 8 It is the obstacle distance data and interference waveform data waveform diagram output when there are fixed obstacles and co-frequency interference; Fig. 9 It is the obstacle distance data and interference waveform data waveform diagram output when there is a moving obstacle and co-frequency interference; Fig.10 It is a waveform diagram of obstacle distance data and interference waveform data output when there is a moving obstacle but no co-frequency interference.

[0116] According to the results shown in the figure, in the ultrasonic radar ranging system, the reaction speed is the fastest without any filtering algorithm processing, but it is very unstable and easily interfered by the same frequency signal and external signal. Adding the same frequency interference filtering algorithm of the present invention can effectively improve the same frequency interference, and the reaction speed is not much different from the measurement data of the system without the filtering algorithm.

[0117] The above-mentioned embodiments are only preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and substitutions made by technicians in this field on the basis of the present invention shall fall within the scope of protection required by the present invention.

Claims

1. An anti-co-frequency interference algorithm for ultrasonic ranging, characterized in that: include: S1: Sending ultrasonic pulses to a space with several obstacles and sampling the echoes returned by the obstacles; S2: Obtain obstacle data by calculating the echo, wherein the obstacle data includes but is not limited to echo height, echo width and duty cycle; S3: performing segmented filtering processing on the interference amount in the echo according to the obstacle data; S4: Use multiple groups of prime number random arrays to perform dislocation processing on the ultrasonic pulse and echo, add random difference assignment, and repeat step S1.

2. The anti-co-frequency interference algorithm for ultrasonic ranging according to claim 1 is characterized in that: The segmented filtering process in step S3 includes the following steps: S31: obtaining an empirical value of the amount of interference existing in ultrasonic ranging in the space, and setting segment intervals with the maximum and minimum values ​​of the empirical value as endpoints; S32: segmenting the segmented interval, and setting different filtering algorithms according to the characteristics of the interference in different segments; S33: judging whether there is an interference signal in the echo according to the obstacle data, and if so, executing the next step; if not, executing step S4; S34: Determine the segment to which the interference signal belongs, and perform filtering processing according to the filtering algorithm corresponding to the segment to which the interference signal belongs.

3. The anti-co-frequency interference algorithm for ultrasonic ranging according to claim 2 is characterized in that: The empirical value of the interference amount is 2-31 dB, and the segment interval is [2, 31].

4. The anti-co-frequency interference algorithm for ultrasonic ranging according to claim 3 is characterized in that: The segmented interval is divided into a first interval segment, a second interval segment and a third interval segment, the first interval segment is the endpoint 31, the second interval segment is (5, 31), and the third interval segment is [2, 5].

5. The anti-co-frequency interference algorithm for ultrasonic ranging according to claim 4 is characterized in that: The characteristics of the interference amount corresponding to the first interval include: Characteristic 1: The interference quantity overlaps with the echo of a relatively large obstacle; Characteristic 2: The interference amount overlaps with the echo of an obstacle that is relatively close; The characteristic of the interference amount corresponding to the second interval is: Characteristic 3: the obstacle data exists in the interference amount; The characteristic of the interference amount corresponding to the third interval is: Characteristic 4: The interference quantity overlaps with the command signal and the unstable signal.

6. The anti-co-frequency interference algorithm for ultrasonic ranging according to claim 5 is characterized in that: The filtering algorithm for the interference value of the first interval includes: For the interference quantity with characteristic 1, the interference signal is determined by comparing the unstable characteristics of the interference quantity for many times, and the interference signal is filtered out; For the interference quantity with characteristic 2, the unstable signal is filtered out by limiting the echo size of the obstacle.

7. The anti-co-frequency interference algorithm for ultrasonic ranging according to claim 5 is characterized in that: The filtering algorithm for the interference value of the second interval is: S321: Record the obstacle data and its timestamp calculated from two consecutive rounds of echoes; S322: Calculate the distance change of the obstacle according to the obstacle data recorded in the front and rear rounds, and determine whether the obstacle has moved according to the distance change; S323: if no displacement occurs, determine the interference signal according to the echo attenuation characteristic, and filter out the interference signal; if displacement occurs, execute step S324; S324: Calculate the relative movement speed of the obstacle according to the distance change and the timestamp, determine the interference signal by judging whether the relative movement speed meets the obstacle movement condition, and filter out the interference signal.

8. The anti-co-frequency interference algorithm for ultrasonic ranging according to claim 7 is characterized in that: Also includes: S325: Obtain the directional characteristics of the obstacle, determine the interference signal by judging whether the directional characteristics of the two rounds of echoes are consistent, and filter out the interference signal.

9. The anti-co-frequency interference algorithm for ultrasonic ranging according to claim 5, characterized in that: The filtering algorithm for the interference value of the third interval is: For interference quantities with characteristic 4, all interference quantities are regarded as interference signals and filtered out.

10. The anti-co-frequency interference algorithm for ultrasonic ranging according to claim 2, characterized in that: When it is determined in step S33 that there is an interference signal in the echo, the following steps are further performed: S331: Setting a scene protection value, and using the scene protection value to replace the disturbed echo signal value to protect the scene cache data.

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