阅读说明：本技术 适用于激光在线测厚的振动补偿方法 (Vibration compensation method suitable for laser on-line thickness measurement ) 是由 周华民 宋华雄 杨志明 张云 周军 王云明 于 2020-05-08 设计创作，主要内容包括：本发明属于薄膜制造加工过程中的在线检测领域,更具体的,涉及一种适用于激光在线测厚的振动补偿方法。该方法包括以下内容：(1)运用激光在线测厚系统,在同一测量环境下,对待测带材和高精度铜箔进行在线扫描测量；(2)带材和铜箔测厚数据中均包含扫描测量时的振动误差,铜箔制造精度高,数据中的误差大部分是由振动导致,而待测带材也受到了相似的振动影响；(3)对测厚数据进行频谱分析,观察数据频率组成信息；(4)对比分析待测带材和铜箔频谱的相似性,对数据进行适当处理,很好地去除了振动对在线扫描测厚的影响,实现了测厚数据的振动补偿和精度优化。(The invention belongs to the field of online detection in a film manufacturing and processing process, and particularly relates to a vibration compensation method suitable for laser online thickness measurement. The method comprises the following steps: (1) performing online scanning measurement on the strip to be measured and the high-precision copper foil in the same measurement environment by using a laser online thickness measurement system; (2) the thickness measurement data of the strip and the copper foil comprise vibration errors in scanning measurement, the manufacturing precision of the copper foil is high, most of errors in the data are caused by vibration, and the strip to be measured is influenced by similar vibration; (3) carrying out spectrum analysis on the thickness measurement data, and observing data frequency composition information; (4) the similarity of the frequency spectrums of the strip to be measured and the copper foil is contrastively analyzed, data are properly processed, the influence of vibration on online scanning thickness measurement is well eliminated, and vibration compensation and precision optimization of the thickness measurement data are realized.)

1. A vibration compensation method suitable for laser online thickness measurement is characterized by comprising the following steps:

step 1: performing online scanning measurement on the strip to be measured and the high-precision copper foil in the same measurement environment by using a laser online thickness measurement system;

step 2: performing spectrum analysis on the obtained thickness measurement data, and observing data frequency composition information;

and step 3: and comparing and analyzing the frequency spectrum similarity of the strip to be measured and the copper foil, processing the data, removing the influence of vibration on-line scanning thickness measurement, and realizing the vibration compensation and precision optimization of the thickness measurement data.

2. The vibration compensation method suitable for laser online thickness measurement according to claim 1, wherein the step 1 specifically comprises the following steps:

1.1, after a thickness measuring system is initialized, setting a sampling frequency f, a tape-moving speed Vr and a scanning speed Vs;

1.2 respectively placing the strip to be measured and the copper foil on a thickness measuring system for scanning thickness measurement.

3. The vibration compensation method suitable for laser online thickness measurement according to claim 2, wherein the measurement process of the strip to be measured and the copper foil in step 1.2 is performed under the same parameters and environment.

4. The vibration compensation method suitable for laser online thickness measurement according to claim 1, 2 or 3, wherein the step 3 specifically comprises the following steps:

3.1 selecting an initial frequency value a and an end frequency value b, and calculating the cosine similarity C of the strip to be measured and the copper foil in the selected frequency interval by utilizing a cosine similarity calculation formula₀The cosine similarity calculation formula is as follows:

wherein X, Y is the frequency point of the strip and the copper foil, and n is the bandwidth, namely n is b-a;

3.2 expanding the frequency interval to the right L, namely the starting frequency value a, the ending frequency value b + L, and calculating the cosine similarity C of the strip to be measured and the copper foil in the new frequency interval by utilizing a cosine similarity calculation formula₁Simultaneously recording corresponding frequency intervals;

3.3 repeat step 3.2m times, each time the cosine similarity is C_mUntil the end frequency value b + m L reaches the boundary f of the range of the vibration frequency_v；

3.4 comparing the cosine similarity (C0-Cm) obtained by multiple calculations, and selecting an interval with the C >0.8 as a similar interval;

and 3.5, designing a filter, and filtering the signals of the frequency interval obtained in the step 3.4 to obtain a final result.

5. The vibration compensation method for on-line laser thickness measurement according to claim 4, wherein the starting frequency value a is greater than the band thickness fluctuation frequency value in step 3.1, and the ending frequency value b is less than the boundary value of the vibration frequency, and is considered similar when C > 0.8.

Technical Field

The invention belongs to the field of online detection in a film manufacturing and processing process, and particularly relates to a vibration compensation method suitable for laser online thickness measurement.

Background

The laser thickness measurement has the advantages of safety, reliability, high measurement precision, wide measurement range and the like, and is widely applied to thickness detection of materials such as paper, lithium ion battery pole pieces, organic battery films, fuel battery electrodes, functional films and the like. The film is mostly manufactured by a low-cost and high-efficiency roll-to-roll manufacturing process, in the processing and manufacturing process, the thickness measurement in the width direction of the strip needs to adopt a multi-sensor or scanning type measurement, the latter undoubtedly greatly reduces the cost, but the inevitable vibration introduced in the scanning process influences the measurement precision.

Regarding the control of vibration-induced errors, the existing vibration compensation and precision optimization methods mainly focus on the improvement of the thickness measurement system and the post-processing of the thickness measurement data. If the laser thickness gauge is subjected to modal analysis and vibration experiments, the structure of the scanning frame is improved; extra lasers and detectors are added to compensate the distance fluctuation between the upper laser displacement sensor and the lower laser displacement sensor; and (3) performing data processing on the laser thickness measurement data by using wavelet transformation and a sparse matrix solution. However, the methods have some problems, one is to add one to two sets of lasers and laser detectors, so that the cost is increased, and the requirement on installation accuracy is increased; secondly, the authenticity of the data can be lost in the data processing process.

Environmental noise, mechanical vibration, thickness fluctuation and other information can be focused in the frequency spectrum of thickness measurement data through frequency spectrum analysis, and as long as the frequency interval of vibration can be determined in the frequency spectrum, the influence of vibration on the measurement result can be well eliminated, and meanwhile, real thickness information is kept, so that vibration compensation and precision optimization are realized.

Disclosure of Invention

The invention mainly aims at the problem of errors caused by vibration to a measurement result in the current laser online thickness measurement process, and provides a vibration compensation and precision optimization method.

Based on this, the invention adopts the following technical scheme:

a vibration compensation method suitable for laser online thickness measurement comprises the following steps:

step 1, operating a thickness measuring system, and setting a sampling frequency f, a tape running speed Vr and a scanning speed Vs after the thickness measuring system is initialized;

step 2, respectively placing the strip to be measured and the copper foil on a thickness measuring system, and carrying out scanning thickness measurement;

and 3, comparing and analyzing the similarity of the frequency spectrums of the strip to be measured and the copper foil, processing the data, removing the influence of vibration on online scanning thickness measurement, and realizing vibration compensation and precision optimization of the thickness measurement data.

Further, the step 1 specifically includes the following steps:

1.1, after a thickness measuring system is initialized, setting a sampling frequency f, a tape-moving speed Vr and a scanning speed Vs;

1.2 respectively placing the strip to be measured and the copper foil on a thickness measuring system for scanning thickness measurement.

Further, the measurement process of the strip to be measured and the copper foil in the step 2 is carried out under the same parameters and environment.

And carrying out spectrum analysis on the obtained thickness measurement data, and observing data frequency composition information.

Selecting an initial frequency value a and an end frequency value b, and calculating the cosine similarity C of the strip to be tested and the copper foil in the selected frequency interval₀The cosine similarity calculation formula is as follows:

where X, Y is the frequency point of the tape and copper foil, and n is the bandwidth, i.e., n-b-a.

Furthermore, in step 5, the starting frequency value a should be greater than the band thickness fluctuation frequency value, and the ending frequency value b should be less than the boundary value of the vibration frequency.

Further, the cosine similarity C >0.8 in step 5 can be regarded as similar.

Further, expanding L the frequency interval to the right, namely the starting frequency value a and the ending frequency value b + L, calculating the cosine similarity C of the strip to be measured and the copper foil in the new frequency interval₁And simultaneously recording the corresponding frequency interval.

Further, repeating the step 7m times, wherein the cosine similarity calculated each time is C_mUntil the end frequency value b + m L reaches the boundary f of the range of the vibration frequency_v。

Further, cosine similarity (C) obtained by multiple calculations is compared₀～C_m) Selecting C>The interval of 0.8 is taken as the similar interval.

Further, a filter is designed to filter the signals of the frequency interval obtained in the step 9, and a final result is obtained.

The invention can analyze the embodiment of vibration in a data frequency spectrum from thickness measurement data, better separate out vibration signals and realize vibration compensation and precision optimization of measurement results on the premise of keeping real thickness fluctuation information.

Drawings

Fig. 1 is a flow chart of a vibration compensation method suitable for laser online thickness measurement according to the invention.

FIG. 2 is a flow chart of determining the similar interval of the frequency spectrum of the strip to be tested and the copper foil through cosine similarity.

Fig. 3 is a frequency spectrum diagram of electrode thickness measurement and copper foil thickness measurement by taking online scanning measurement of a lithium ion battery pole piece as an example.

FIG. 4 is a comparison graph of thickness measurement data of electrodes and copper foils before and after vibration compensation by taking online scanning measurement of a lithium ion battery pole piece as an example.

Detailed Description

In order to make the objects, aspects and advantages of the present invention clearer, the following examples are given to illustrate the present invention in further detail with reference to the accompanying drawings. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without making any creative effort, shall fall within the protection scope of the present invention.

FIG. 1 is a flow chart of a vibration compensation method suitable for laser on-line thickness measurement according to the present invention; FIG. 2 is a flow chart of determining the frequency spectrum similarity interval of the strip to be detected and the copper foil through cosine similarity.

The invention takes the on-line scanning thickness measurement in the rolling process and the whole line manufacturing process of the lithium ion battery pole piece as an example, and the invention is explained in detail in the invention, the thickness measurement system is a double-laser displacement sensor up-down differential thickness measurement system, the model of the laser displacement sensor is Kenzhi L K-H025, and the measurement materials are 180.5 mu m thick battery pole piece and 15 mu m thick copper foil.

Specifically, the method comprises the following steps:

1. and (3) operating the thickness measuring system, and setting the sampling frequency f to be 100Hz, the tape transport speed Vr to be 1m/min and the scanning speed Vs to be 55mm/s after the thickness measuring system is initialized.

2. And respectively placing the battery pole piece and the copper foil on a thickness measuring system, and carrying out scanning thickness measurement under the same parameters and environment, wherein the measurement result is shown as Raw Data point in the attached figure 4.

3. And performing spectrum analysis on the obtained thickness measurement data, and observing data frequency composition information, wherein electrode and copper foil spectrograms are shown in an attached figure 3, wherein the upper three are electrode spectrums, and the lower three are copper foil spectrums. The thickness measurement data of the electrode and the copper foil comprise vibration errors in scanning measurement, the manufacturing precision of the copper foil is high, most of errors in the data are caused by vibration, and when the measurement is carried out under the same condition, the electrode is influenced by similar vibration. Therefore, the representation of the vibration in the two frequency spectrums is similar, and the frequency spectrum difference is mostly represented by the thickness fluctuation information of the vibration.

As can be seen from FIG. 3, the spectral amplitude is already small around 125Hz, which can be considered as the vibration cut-off frequency. In addition, the thickness fluctuation of the electrode and the copper foil is low-frequency signals: (<2 Hz). The initial frequency value a should be largeAnd in the frequency value of the fluctuation of the thickness of the strip material of 2Hz, the termination frequency value b is less than the vibration frequency of 130 Hz. Based on the frequency range, selecting an initial frequency value a of 10Hz and an end frequency value b of 40Hz, and calculating the cosine similarity C of the strip to be measured and the copper foil in the selected frequency range₀When the similarity is larger than 0.876, the similarity is considered to be similar. The cosine similarity calculation formula is as follows:

wherein X, Y is the frequency point of the strip and the copper foil, and n is the bandwidth, i.e. n-b-a-90 Hz.

After the initial cosine similarity is calculated, the frequency interval is expanded to the right by L to 1Hz, namely the initial frequency value a is 10Hz, the termination frequency value b + L is 41Hz, and the cosine similarity C of the strip to be measured and the copper foil in the new frequency interval is calculated₁＝0.882>0.8, the electrode and the copper foil have similar frequency spectrums in a new frequency interval (10 Hz-41 Hz), and the corresponding frequency interval of 10 Hz-41 Hz is recorded.

Repeating the step 7m times, wherein the cosine similarity calculated each time is C_mUntil the end frequency value b + mX reaches the oscillation cut-off frequency of 125 Hz.

The cosine similarity is calculated in a circulating way, and is found to show a decreasing trend after 103Hz and is less than 0.8. In this case, a frequency range of 10Hz to 103Hz is selected as a vibration characterization range.

And (3) designing a filter, and filtering the signals in the frequency interval (10-103 Hz) obtained in the step (7) to obtain a final result as shown in the Processed Data point of the attached figure 4.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and the above embodiment is only illustrative and not restrictive, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention.