CN102208951B - Method for eliminating acoustic radiation interferences in ultrasonic positioning - Google Patents

Abstract

The invention provides a method for eliminating acoustic radiation interference in ultrasonic positioning. The method has the following characteristics: firstly, the ultrasonic receiving signal is preprocessed by digital filtering, and then the peak envelope of the ultrasonic receiving signal is extracted by first-order difference; secondly, the second-order difference quotient is performed on the peak envelope of the ultrasonic receiving signal, and based on the second-order The maximum value of the difference quotient obtains the breakpoint position of the ultrasonic received signal; again, the breakpoint position is mapped onto the reference signal to obtain the "false breakpoint" position on the reference signal and based on the "false breakpoint" position of the reference signal. Taylor series expansion; finally, replace the waveform before the breakpoint with the waveform obtained by Taylor series expansion. The invention has the advantages of low cost and high flexibility, can accurately restore ultrasonic signals suitable for positioning under the condition of noise or non-radiation interference, has strong applicability, and the calculation amount of the algorithm is small, and can be applied to real-time High ultrasonic positioning system.

Description

A Method for Eliminating Acoustic Radiation Interference in Ultrasonic Positioning

technical field

The invention relates to a method for eliminating acoustic radiation interference, in particular to a method for eliminating acoustic radiation interference in ultrasonic positioning to obtain ultrasonic signals suitable for positioning.

Background technique

In practical applications, such as the typical system of ultrasonic positioning—ultrasonic electronic whiteboard system, there will be a kind of acoustic radiation interference in the writing board. , its radiation is non-directional and strong, and the existing filtering technology is difficult to filter it out, which will seriously affect the system positioning performance, and even lead to the failure of the system positioning function, which seriously restricts the application field of the ultrasonic positioning system. In 2008, the American ebeam company proposed an anti-jamming solution based on multi-receiver partition positioning for the problem of acoustic interference caused by ultrasonic refraction and reflection under uneven temperature conditions. It has a large positioning area and uneven ambient temperature changes It is effective to solve the acoustic interference at the time, but there are disadvantages such as high cost and insufficient flexibility. In 2009, the company proposed an adaptive interference elimination scheme for unknown interference. Although the least mean square algorithm can suppress this type of interference well, its convergence speed is slow and its real-time performance is poor, so it is difficult to implement it in the embedded ultrasonic positioning system. application.

Contents of the invention

Based on the above analysis, innovating on the basis of the existing ultrasonic anti-interference technology, aiming at the influence of acoustic radiation interference on the positioning function in ultrasonic positioning, it is the main goal of the present invention to seek a sound radiation interference elimination method with high real-time performance.

The invention provides an effective method for eliminating acoustic radiation interference in ultrasonic positioning, comprising the following steps:

(1) Ultrasonic received signal preprocessing;

(2) Extract the peak envelope of the ultrasonic received signal, and determine the maximum point or sub-maximum point or minimum point on the peak envelope of the ultrasonic received signal as the feature point;

(3) Determine the location of the breakpoint;

(4) According to the breakpoint position obtained in step (3), by selecting the characteristic points of the peak envelope of the ultrasonic received signal obtained in step (2), calculate the relative position of the breakpoint on the ultrasonic received signal and map it to the reference signal Obtain the position of the "pseudo-breakpoint" of the reference signal, and perform Taylor series expansion based on the "pseudo-breakpoint";

(5) Waveform replacement.

The ultrasonic receiving signal preprocessing process described in the step (1) of the present invention refers to performing digital filtering on the ultrasonic receiving signal, filtering out high-frequency components and removing DC components.

The process of extracting the peak envelope of the ultrasonic received signal described in step (2) of the present invention refers to performing a first-order difference operation on the preprocessed ultrasonic received signal to determine the sign change, thereby extracting the peak envelope of the ultrasonic received signal .

The process of determining the position of the breakpoint described in the step (3) of the present invention refers to carrying out the second-order difference quotient to the peak envelope of the ultrasonic received signal obtained in the step (2), and obtaining the maximum value of the second-order difference quotient to obtain The position of the breakpoint of the ultrasonic received signal.

The step (4) of the present invention is based on the process of Taylor series expansion based on "false breakpoints", wherein the reference signal can be a mixed exponential model signal, a double exponential model signal or a Gaussian model signal.

The waveform replacement process in step (5) of the present invention 6 refers to using the waveform obtained by Taylor series expansion in step (4) to replace the waveform before the breakpoint in step (3).

By obtaining the position of the breakpoint of the measured ultrasonic receiving signal, and then obtaining the position of the "pseudo-breakpoint" on the reference signal through the mapping relationship, the waveform obtained by Taylor series expansion at the "pseudo-breakpoint" is further used to replace the breakpoint of the measured ultrasonic receiving signal before the breakpoint Waveform, and finally eliminate the sound radiation interference. Through the above steps, the purpose of eliminating acoustic radiation interference is achieved.

Advantage of the present invention has following advantage:

1. Compared with the existing filtering technology, the method proposed by the present invention effectively eliminates the acoustic radiation interference of the ultrasonic positioning system.

2. Using the Taylor series expansion at the "false breakpoint" of the reference signal to replace the waveform before the breakpoint of the ultrasonic receiving signal can effectively reduce the computational load of the algorithm while ensuring the elimination of acoustic radiation interference, which is beneficial to embedding with high real-time requirements application in ultrasonic positioning systems.

Description of drawings

Fig. 1 is the overall flowchart of the method for eliminating acoustic radiation interference in ultrasonic positioning of the present invention;

Fig. 2 is a block diagram of the ultrasonic receiving signal preprocessing of the present invention;

Fig. 3A is the preprocessed waveform diagram of the ultrasonic receiving signal carrying acoustic radiation interference of the present invention;

Fig. 3B is a specific embodiment of the acoustic radiation interference generated by the ultrasonic electronic whiteboard system of the present invention;

Fig. 4 is the peak envelope figure after preprocessing of the ultrasonic signal with acoustic radiation interference of the present invention;

Fig. 5A is a flow chart of determining the position of the breakpoint of the ultrasonic received signal of the present invention;

Fig. 5B is a waveform diagram for determining the breakpoint position of the ultrasonic received signal according to the present invention;

Fig. 6 is a schematic diagram of the mapping relationship of breakpoint positions in the present invention;

Fig. 7 is the implementation process of replacing the signal waveform before the breakpoint of the ultrasonic received signal by using the waveform obtained by Taylor series expansion corresponding to the position of the "false breakpoint" on the reference signal in the present invention;

8A-1 , 8A-2 , 8B-1 , 8B-2 , 8C-1 , and 8C-2 are diagrams of simulation experiment results of the present invention.

Detailed ways

Including the following steps:

(1) Ultrasonic received signal preprocessing;

Fig. 1 is a general flowchart illustrating a method for eliminating acoustic radiation interference in ultrasonic positioning according to the present invention. Specifically include the following steps:

[101]—the ultrasonic received signal is preprocessed to obtain signal data with high signal-to-noise ratio and low data error rate;

[102]—extract the peak envelope of the ultrasonic received signal, so as to utilize it to carry out algorithm processing;

[103]—determine the position of breakpoint, so that mapping transformation is carried out;

[104]—Taylor series expansion based on "false breakpoint" to extract ideal ultrasonic signal envelope;

[105]—Waveform replacement in order to obtain ultrasonic signals suitable for localization after eliminating acoustic radiation interference.

Fig. 2 is a block diagram showing the preprocessing of ultrasonic received signals according to the present invention. The signal received by the ultrasonic receiving sensor is a very weak analog signal, and the signal still carries certain high-frequency noise after the signal amplifier circuit and the A/D conversion circuit. For this reason, in a specific embodiment of the present invention, a digital FIR is selected. The filter preprocesses the ultrasonic received signal, and filters out high-frequency components and DC components through time-domain convolution operations to obtain signal data with high signal-to-noise ratio and low data error rate;

FIG. 3A is a waveform diagram showing preprocessed ultrasonic received signals carrying acoustic radiation interference according to the present invention. As shown in the figure, [301] is an ultrasonic signal, and [302] is an acoustic radiation signal. In the specific embodiment where the ultrasonic electronic whiteboard system of the present invention produces acoustic radiation interference, as shown in Figure 3B, due to the excitation of the signal pen [303], an acoustic radiation source [305] will be formed on the writing board surface [304], which The radiation frequency is related to the bending stiffness of the board surface and the thickness of the board surface. The radiation directivity is weak directivity and the radiation intensity is high. After receiving by the ultrasonic receiver [306], the ultrasonic receiving signal waveform with acoustic radiation interference will be obtained. Existence will seriously affect the system positioning performance, and even cause the system positioning function to fail.

(2) Extract the peak envelope of the ultrasonic received signal, and determine the maximum point or sub-maximum point or minimum point on the peak envelope of the ultrasonic received signal as the feature point;

Fig. 4 is a peak envelope diagram showing the preprocessed ultrasonic signal with acoustic radiation interference according to the present invention. As shown in Figure 4, [401] represents the maximum peak point of the signal, and [402] represents the first breakpoint calculated forward from the maximum peak point, and performs a first-order difference operation on the preprocessed ultrasonic received signal to perform sign change Judgment, so as to extract the peak envelope of the ultrasonic receiving signal, which is convenient for algorithm processing.

(3) Determine the location of the breakpoint;

5A and 5B show the specific implementation process of determining the breakpoint position of the ultrasonic received signal according to the present invention. The specific positioning process is as follows:

[501] - search for the maximum magnitude max1 [505] in the stored data;

[502] - search for direct signal max2 [506] and save its address max2ad [507];

[503]—in the first 200 points of [506], calculate the second-order difference quotient of the peak value of the signal;

[504]—Search for the maximum value of the second-order difference quotient to obtain the signal breakpoint [402].

(4) According to the breakpoint position obtained in step (3), by selecting the characteristic points of the peak envelope of the ultrasonic received signal obtained in step (2), calculate the relative position of the breakpoint on the ultrasonic received signal and map it to the reference signal Obtain the position of the "pseudo-breakpoint" of the reference signal, and perform Taylor series expansion based on the "pseudo-breakpoint";

[602]。 Fig. 6 is a schematic diagram showing the mapping relationship of breakpoint positions according to the present invention. Extract breakpoint [402] position and eigenvalue point [401] in the peak envelope of ultrasonic received signal (in this embodiment, eigenvalue point is the maximum point on the peak envelope of ultrasonic received signal, but not limited to Therefore, according to the actual situation, the sub-maximum point or minimum point on the peak envelope of the ultrasonic received signal can also be used as the eigenvalue point), and then correspondingly mapped to the reference signal to obtain the "pseudo-breakpoint" of the reference signal [ 602] and the position of the maximum peak point [601], the mapping relationship is [401] [601], [402]

[602].

是信号的幅度，m为正整数，取值范围为1~3，

是超声信号的中心频率，

为初相位，h为衰减因子。信号的包络为

。 It should be further explained that in this embodiment, the reference signal may be a mixed exponential model signal, a double exponential model signal or a Gaussian model signal. Taking the mixed exponential model signal as an example, the signal expression is ,in,

is the amplitude of the signal, m is a positive integer, the value range is 1~3,

is the center frequency of the ultrasonic signal,

is the initial phase, h is the attenuation factor. The envelope of the signal is

.

(5) Waveform replacement.

Fig. 7 shows the implementation process of replacing the signal waveform before the breakpoint of the ultrasonic received signal by using the waveform obtained by Taylor series expansion corresponding to the position of the "false breakpoint" on the reference signal according to the present invention. Its specific implementation process is as follows:

[701]—do Taylor series expansion at the reference signal "false breakpoint" and keep the first three terms;

[702]—use the waveform obtained by Taylor series expansion to replace the signal waveform before the ultrasonic receiving signal breakpoint;

[703]—eliminate radiation interference, and obtain an ultrasonic signal that removes acoustic radiation interference.

The process of extracting the peak envelope of the ultrasonic received signal described in step (2) of the present invention refers to performing a first-order difference operation on the preprocessed ultrasonic received signal to determine the sign change, thereby extracting the peak envelope of the ultrasonic received signal .

The process of determining the position of the breakpoint described in the step (3) of the present invention refers to carrying out the second-order difference quotient to the peak envelope of the ultrasonic received signal obtained in the step (2), and obtaining the maximum value of the second-order difference quotient to obtain The position of the breakpoint of the ultrasonic received signal.

The step (4) of the present invention is based on the process of Taylor series expansion based on "false breakpoints", wherein the reference signal can be a mixed exponential model signal, a double exponential model signal or a Gaussian model signal.

The waveform replacement process in step (5) of the present invention 6 refers to using the waveform obtained by Taylor series expansion in step (4) to replace the waveform before the breakpoint in step (3).

In particular, it should be pointed out that the Taylor series expansion method used in the embodiment of the present invention uses polynomials to simplify the mathematical model of the reference signal. When calculating the function value at a certain point, only a limited number of multiplication and addition operations are required. It greatly reduces the amount of calculation and ensures the real-time requirements of the ultrasonic positioning system.

The effect of the method for eliminating acoustic radiation interference in ultrasonic positioning according to the present invention will be described below from the results of simulation experiments.

In a specific embodiment of the present invention, the set experimental conditions are as follows: taking the typical system of ultrasonic positioning—ultrasonic electronic whiteboard system as the experimental platform, using The method provided by the invention eliminates the acoustic radiation interference experiment.

Fig. 8A-1, 8A-2, 8B-1, 8B-2, 8C-1, 8C-2 respectively show that the thickness is 0.25mm, 0.45mm and 0.65mm iron homogeneous plates are restored by the method of the present invention The rendering of the ultrasonic signal. It can be seen from the figure that the method for eliminating acoustic radiation interference in ultrasonic positioning provided by the present invention can accurately recover ultrasonic signals suitable for positioning under the condition of presence or absence of acoustic radiation interference, and has strong applicability.

Claims (6)

1. eliminate the method that acoustic radiation is disturbed in the localization by ultrasonic for one kind, it is characterized in that comprising the steps:

(1) ultrasonic reception Signal Pretreatment;

(2) extract ultrasonic reception signal peak envelope, determine that maximum of points on the ultrasonic reception signal peak envelope or inferior maximum of points or minimum point are characteristic point;

(3) determine the position of breakpoint;

(4) according to the breakpoint location that obtains in the step 3, by choosing the characteristic point of the ultrasonic reception signal peak envelope that obtains in the step 2, calculate breakpoint on ultrasonic reception signal relative position and be mapped on the reference signal to obtain " pseudo-breakpoint " position of reference signal, make Taylor series expansion based on " pseudo-breakpoint ";

(5) waveform is replaced.

2. a kind of method that acoustic radiation in the localization by ultrasonic is disturbed of eliminating according to claim 1, it is characterized in that the ultrasonic reception Signal Pretreatment process of describing in the wherein said step 1 refers to ultrasonic reception signal is carried out digital filtering, filtering high fdrequency component and removal DC component.

3. a kind of method that acoustic radiation in the localization by ultrasonic is disturbed of eliminating according to claim 1, it is characterized in that the ultrasonic reception signal peak of the extraction envelope process of describing in the wherein said step 2 refers to that pretreated ultrasonic reception signal is carried out the first-order difference computing to be judged to carry out sign change, thereby extract the peak envelope of ultrasonic reception signal.

4. a kind of method that acoustic radiation in the localization by ultrasonic is disturbed of eliminating according to claim 1, the process that it is characterized in that in the wherein said step 3 position of definite breakpoint of describing refers to the ultrasonic reception signal peak envelope that obtains in the step 2 is carried out the second order difference coefficient, and obtains the position of ultrasonic reception signal breakpoint by obtaining second order difference coefficient maximum.

5. a kind of method that acoustic radiation in the localization by ultrasonic is disturbed of eliminating according to claim 1, it is characterized in that wherein said step 4 makes the process of Taylor series expansion based on " pseudo-breakpoint ", wherein said reference signal is blended index model signals, biexponential model signal or Gauss model signal.

6. a kind of method that acoustic radiation is disturbed in the localization by ultrasonic of eliminating according to claim 1 is characterized in that the waveform replacement process in the wherein said step 5 refers to utilize the waveform before the breakpoint described in the waveform replacement step 3 that Taylor series expansion obtains in the step 4.

Images