CN-121977484-A - Dynamic monitoring and analyzing method for deformation degree of tennis racket frame

CN121977484ACN 121977484 ACN121977484 ACN 121977484ACN-121977484-A

Abstract

The application provides a dynamic monitoring and analyzing method of deformation degree of a tennis racket frame, which comprises the steps of capturing real-time vibration signals of the tennis racket frame through a piezoelectric vibration acquisition unit, obtaining original vibration data of different orders of natural frequencies of the frame, recording modal amplitude distribution of vibration modes of each order to obtain an initial vibration signal set, identifying drift amount of each order of natural frequency to a low frequency band according to a frame vibration analysis result, identifying the drift amount as high drift amount or low drift amount through a drift amount threshold value to obtain a frequency drift grade, integrating a plastic deformation evaluation conclusion and a brittle deformation evaluation conclusion, combining the frequency drift grade, identifying frame damage as mild damage, moderate damage or severe damage through a deformation severity threshold value to obtain a frame damage grade, combining the plastic deformation evaluation conclusion or the brittle deformation evaluation conclusion according to the frame damage grade, and outputting classification results of the frame deformation type and the damage degree to complete dynamic monitoring and analyzing treatment of the frame deformation.

Inventors

Liu Chuze
HU YINGKUN
Lin Xiongbo
DAI QIBING

Assignees

广东工贸职业技术学院

Dates

Publication Date: 20260505
Application Date: 20260115

Claims (8)

1. A dynamic monitoring and analyzing method for deformation degree of a tennis racket frame, which is characterized by comprising the following steps: Capturing real-time vibration signals of the tennis racket frame through a piezoelectric vibration acquisition unit, acquiring original vibration data of different orders of natural frequencies of the frame, and recording modal amplitude distribution of each order of vibration modes to obtain an initial vibration signal set; carrying out frequency domain decomposition on the initial vibration signal set, extracting specific frequency values and vibration damping ratios of natural frequencies of different orders, and simultaneously identifying the lifting direction of the vibration damping ratios to obtain a frame vibration analysis result; According to the frame vibration analysis result, identifying the drift amount of the natural frequency of each order to a low frequency band, and dividing the drift amount into a high drift amount or a low drift amount according to the drift amount to obtain a frequency drift level; Aiming at the frequency drift level, when the frequency drift level is identified as high drift amount, carrying out deformation type analysis in combination with the lifting direction of the vibration damping ratio, and when the vibration damping ratio is in the lifting direction, evaluating the relaxation degree of the internal structure of the frame material, and identifying the frame material as plastic deformation to obtain a plastic deformation evaluation conclusion; When the vibration damping ratio is in a descending direction, analyzing a local amplitude concentration area in the mode amplitude distribution of each order of vibration mode, identifying the position of a stress point concentrated on the frame, and when the local concentration of the amplitude is detected, evaluating the local cracking degree of the frame, identifying the frame as brittle deformation, and obtaining a brittle deformation evaluation conclusion; Combining the plastic deformation evaluation conclusion and the brittle deformation evaluation conclusion, and combining the frequency drift grade, and classifying the frame damage into mild damage, moderate damage or severe damage according to a deformation severity classification rule to obtain a frame damage grade; And outputting classification results of the frame deformation type and the damage degree according to the frame damage grade and combining the plastic deformation evaluation conclusion or the brittle deformation evaluation conclusion to finish the dynamic monitoring and analysis processing of the frame deformation.
2. The method for dynamically monitoring and analyzing the deformation degree of a tennis racket frame according to claim 1, wherein the capturing of real-time vibration signals of the tennis racket frame by the piezoelectric vibration acquisition unit, obtaining original vibration data of different orders of natural frequencies of the frame, recording modal amplitude distribution of each order of vibration modes, and obtaining an initial vibration signal set, comprises the following steps: Vibration monitoring is carried out on different positions of the tennis racket frame by adopting a piezoelectric sensor array, a charge signal is converted into a voltage signal by a charge amplifier, and the voltage signal is collected at a frequency higher than a preset sampling frequency, so that frame time domain vibration response data are obtained; Performing time-frequency conversion on the frame time domain vibration response data, identifying the inherent frequency values of a first-order bending mode, a second-order torsion mode and a third-order composite mode, determining the damping ratio of each-order mode, recording the amplitude peak value of each position, and constructing the mode amplitude distribution; and judging the category of the current vibration mode according to the relative ratio and the phase relation of the amplitudes at different positions in the modal amplitude distribution, and synthesizing the time domain vibration response data, the inherent frequency values of each order, the damping ratio and the modal amplitude distribution to obtain an initial vibration signal set.
3. The dynamic monitoring and analyzing method of the deformation degree of a tennis racket frame according to claim 1, wherein the frequency domain decomposition is performed on the initial vibration signal set, specific frequency values and vibration damping ratios of different order natural frequencies are extracted, and the lifting direction of the vibration damping ratio is identified at the same time, so as to obtain a frame vibration analysis result, and the method comprises the following steps: performing time-frequency transformation after windowing on time domain data in the initial vibration signal set to obtain frequency domain spectral line distribution, and extracting inherent frequency values, amplitude values and phase information of each order of modes from the frequency domain spectral line distribution; calculating the damping ratio of each order mode according to the frequency domain spectral line distribution, comparing the values of the damping ratios before and after use, and identifying the rising direction or the falling direction of the damping ratio to obtain a damping change trend; and constructing a multidimensional vibration characteristic matrix by integrating the inherent frequency value, the damping ratio, the damping change trend and the correlation characteristics among all the orders of modes to obtain a frame vibration analysis result.
4. The dynamic monitoring and analyzing method for the deformation degree of a tennis racket frame according to claim 1, wherein the steps of identifying the drift amount of the natural frequency of each order to the low frequency band according to the frame vibration analysis result, and dividing the drift amount into a high drift amount or a low drift amount according to the drift amount, and obtaining the frequency drift level comprises the steps of: Extracting the reference frequency of each order mode in the initial state of the frame, comparing the current natural frequency with the reference frequency, and calculating to obtain the frequency drift quantity of each order; Classifying the frequency drift amount according to a preset drift amount classification rule, judging that the frequency drift amount is high when the absolute value of the drift amount exceeds a corresponding threshold value, and judging that the frequency drift amount is low if the absolute value of the drift amount exceeds the corresponding threshold value; and further combining the relative proportion relation of the modal drift amounts of each order and the difference characteristics of the lower-order and higher-order drift amounts, and correcting the classification result to obtain the frequency drift level.
5. The dynamic monitoring and analyzing method of the deformation degree of the tennis racket frame according to claim 1, wherein for the frequency drift level, when the frequency drift level is identified as a high drift amount, the deformation type analysis is performed in combination with the lifting direction of the vibration damping ratio, when the vibration damping ratio is in the lifting direction, the relaxation degree of the internal structure of the frame material is evaluated, and the frequency drift level is identified as plastic deformation, so as to obtain a plastic deformation evaluation conclusion, including: When the frequency drift level is high drift amount, reading a time sequence change sequence of the vibration damping ratio, calculating damping ratio difference values of adjacent measuring points, and judging that the damping ratio is in the rising direction when the continuous positive difference value reaches the set times; Under the condition that the damping ratio is in the rising direction, extracting strain accumulation characteristics of the frame material under cyclic load, and judging that the interface sliding and the structure loosening of the fiber and the matrix occur in the frame material when the accumulated strain exceeds the yield strain range of the material but does not reach the fracture strain range; And identifying the frame deformation type as plastic deformation according to the structure relaxation characteristics and the existence of the unrecoverable permanent deformation, and obtaining a plastic deformation evaluation conclusion.
6. The dynamic monitoring and analyzing method for the deformation degree of a tennis racket frame according to claim 1, wherein when the vibration damping ratio is in a descending direction, analyzing a local amplitude concentration region in the modal amplitude distribution of each order of vibration modes, identifying the positions of stress points concentrated on the frame, and when the local concentration of the amplitude is detected, evaluating the local cracking degree of the frame, identifying as brittle deformation, and obtaining a brittle deformation evaluation conclusion, comprising: When the vibration damping ratio is in a descending direction, calculating the ratio of the amplitude of each measuring point to the overall average amplitude from the modal amplitude distribution of each order of vibration mode, and when the amplitude ratio of a certain area exceeds a set level and the amplitude gradient of the adjacent measuring point is changed drastically, judging the area as an amplitude concentration area and positioning the area as a stress concentration position; Aiming at the stress concentration position, analyzing the change characteristics of high-frequency components of corresponding vibration signals, judging nonlinear vibration response caused by microcracks in the material when the energy of high-frequency harmonic components is obviously increased and the fundamental frequency energy is transferred to high frequency, and determining the high-frequency energy duty ratio; and according to the continuous descending trend of the high-frequency energy ratio and the damping ratio, evaluating the local cracking degree, and recognizing the frame damage type as brittle deformation to obtain a brittle deformation evaluation conclusion.
7. The dynamic monitoring and analyzing method of the deformation degree of the tennis racket frame according to claim 1, wherein the combining of the plastic deformation evaluation conclusion and the brittle deformation evaluation conclusion, the classifying of the frame damage into the light damage, the moderate damage or the heavy damage according to the deformation severity classification rule, the obtaining of the frame damage grade, includes: determining damage type identification including single plastic damage, single brittle damage or composite damage according to the existence state of the plastic deformation evaluation conclusion and the brittle deformation evaluation conclusion; Numerically combining the frequency drift level with the damage type identifier, wherein a high drift amount is combined with brittle damage to give a higher comprehensive damage index, and a low drift amount is combined with plastic damage to give a lower comprehensive damage index; And comparing the comprehensive damage index with a preset multi-stage deformation severity demarcation value, and determining that the frame damage grade is mild damage, moderate damage or severe damage.
8. The dynamic monitoring and analyzing method for the deformation degree of a tennis racket frame according to claim 1, wherein the dynamic monitoring and analyzing process for the deformation of the frame is completed by outputting the classification result of the deformation type and the degree of damage of the frame according to the damage level of the frame in combination with the plastic deformation evaluation conclusion or the brittle deformation evaluation conclusion, and comprises the following steps: According to the damage level of the frame and the corresponding plastic deformation evaluation conclusion or brittle deformation evaluation conclusion, integrating to form a comprehensive state identifier containing the damage level and the deformation type; And outputting a classification result corresponding to the comprehensive state identifier, wherein the classification result comprises specific categories of mild plastic damage, moderate plastic damage, severe plastic damage, mild brittle damage, moderate brittle damage, severe brittle damage and composite damage, and finishing dynamic monitoring and analysis treatment of frame deformation.

Description

Dynamic monitoring and analyzing method for deformation degree of tennis racket frame Technical Field The invention relates to the technical field of information, in particular to a dynamic monitoring and analyzing method for the deformation degree of a tennis racket frame. Background The tennis racket frame can bear repeated impact when being used in a high-strength match, so that the frame is gradually deformed or even damaged, the batting force transmission, the sweet zone position and the whole service life are directly influenced, and therefore dynamic monitoring and analysis of the deformation degree of the frame become an important research field for guaranteeing equipment reliability and athlete performance. The current monitoring method mainly evaluates the deformation degree by observing the change of the vibration frequency of the frame, and generally considers that the more the fundamental frequency shifts to the low frequency, the more serious the deformation. However, the judging mode has obvious defects, because the frequency reduction is probably caused by different damage mechanisms, the frequency reduction is treated uniformly, misjudgment is easy to cause, and especially the actual reasons behind deformation cannot be distinguished in actual use, so that the deviation between an evaluation result and the actual state of the frame is larger. A further problem is that the variation of the frame vibration frequency is affected by the damping ratio, which varies in the opposite direction with the type of damage. When the frame is subjected to plastic deformation due to relaxation of the internal structure of the material, the damping ratio is often increased, the vibration energy is dissipated faster, and conversely, when the frame is subjected to brittle deformation due to local cracking, the damping ratio is reduced, and the vibration duration is prolonged. Under the condition of the same frequency reduction amplitude, the integral softening of the material is reflected when the damping ratio is larger, the structural integrity is destroyed when the damping ratio is smaller, and the deformation severity and the subsequent risk corresponding to the two conditions are completely different, but are difficult to distinguish accurately because only single index of the frequency is concerned. For example, in a long-time match, if the base frequency of the frame is gradually reduced, and the monitoring system only judges that the deformation is serious according to the drift amplitude, but ignores the phenomenon that the damping ratio is reduced at the same time, brittle injuries which have originally occurred local cracking can be misjudged as lighter plastic deformation, so that timely replacement or maintenance of the beat is delayed, and the fracture risk is increased. Therefore, how to dynamically adjust the judging standard of the deformation type and degree by combining the lifting direction of the damping ratio on the basis of frequency change becomes a key problem for realizing accurate classification of frame damage. Disclosure of Invention The invention provides a dynamic monitoring and analyzing method for the deformation degree of a tennis racket frame, which comprises the following steps: Capturing real-time vibration signals of the tennis racket frame through a piezoelectric vibration acquisition unit, acquiring original vibration data of different orders of natural frequencies of the frame, and recording modal amplitude distribution of each order of vibration modes to obtain an initial vibration signal set; carrying out frequency domain decomposition on the initial vibration signal set, extracting specific frequency values and vibration damping ratios of natural frequencies of different orders, and simultaneously identifying the lifting direction of the vibration damping ratios to obtain a frame vibration analysis result; According to the frame vibration analysis result, identifying the drift amount of the natural frequency of each order to a low frequency band, and dividing the drift amount into a high drift amount or a low drift amount according to the drift amount to obtain a frequency drift level; Aiming at the frequency drift level, when the frequency drift level is identified as high drift amount, carrying out deformation type analysis in combination with the lifting direction of the vibration damping ratio, and when the vibration damping ratio is in the lifting direction, evaluating the relaxation degree of the internal structure of the frame material, and identifying the frame material as plastic deformation to obtain a plastic deformation evaluation conclusion; When the vibration damping ratio is in a descending direction, analyzing a local amplitude concentration area in the mode amplitude distribution of each order of vibration mode, identifying the position of a stress point concentrated on the frame, and when the local concentration of the amplitude is detected, evalua