Plywood internal quality detection auxiliary device based on acoustic emission

Abstract

The utility model provides an acoustic emission-based plywood internal quality detection auxiliary device, which comprises a sound production device and a sound pickup device, and is characterized in that the sound production device comprises a PLC (Programmable Logic Controller) control box, an array cylinder, a hammer, a bracket, a sliding device and a material rack; the pickup device comprises a piezoelectric ceramic sensor, an amplifying circuit and an analog-to-digital conversion element; the piezoelectric ceramic sensor is mounted below the material rack; the piezoelectric ceramic sensor is connected with the amplifying circuit, and the amplifying circuit is connected with the analog-to-digital conversion element; the plywood sorting device solves the problems that traditional manual grading is large in error, low in efficiency and high in cost, automation, standardization and large-scale plywood sorting are achieved, and the plywood sorting device has wide market application prospects.

Description

Technical Field

[0001] This utility model belongs to the field of wood processing technology, specifically relating to an auxiliary device for internal quality detection of plywood based on acoustic emission. Background Technology

[0002] Plywood boasts advantages such as high wood utilization, high strength, and strong durability, making it suitable for various applications including aircraft, ships, trains, automobiles, home decoration, construction, and containers. In recent years, with the improvement of living standards and the development of customized home furnishings and fully furnished residences, the quality requirements for plywood products have been increasing. During the production process, factors such as uneven glue application, wood chip cracking, and surface knots can lead to internal defects in plywood, such as delamination, bubbling, and separation. These defects not only affect the mechanical properties of the plywood but also its service life. Therefore, designing a method to accurately detect internal defects in plywood is of great significance in ensuring the quality and performance of plywood products.

[0003] Currently, the traditional method for detecting internal defects in plywood mainly relies on manually tapping the plywood and listening to the sound produced by the vibrations to identify the internal defects and their distribution patterns. For example, a dull sound indicates the presence of voids; a low and short sound often indicates insufficient internal density and potential localized loosening; and irregular, abnormal noises may indicate internal cracks or foreign objects. However, this method has many significant drawbacks. In practice, variations in tapping force and worker concentration can lead to misjudgments or missed detections of plywood quality.

[0004] For defect detection methods in plywood, existing technologies document methods that use computer vision to identify surface defects in eucalyptus chips. This method can identify and sort defects such as pits and cracks on the surface of eucalyptus chips. However, computer vision technology focuses on image acquisition and analysis of the plywood's appearance. It acquires images of the board using high-definition cameras and uses image processing algorithms to extract features such as color, texture, and shape. This method can only identify surface defects in eucalyptus chips, such as knots, wormholes, and cracks. It is ineffective in identifying internal defects in plywood, such as delamination, separation, and bulging. Utility Model Content

[0005] Therefore, the purpose of this utility model is to provide an auxiliary device for detecting the internal quality of plywood based on acoustic emission, so as to comprehensively detect the defects existing inside the plywood and realize the grading of plywood of different qualities.

[0006] The technical solution of this utility model is: an auxiliary device for internal quality detection of plywood based on acoustic emission, comprising: a sound-generating device and a sound-collecting device, wherein the sound-generating device comprises: a PLC control box, an array cylinder, a hammer, a bracket, a sliding device, and a material rack;

[0007] The pickup device includes a piezoelectric ceramic sensor, an amplifier circuit, and an analog-to-digital converter; the piezoelectric ceramic sensor is installed below the material rack.

[0008] The piezoelectric ceramic sensor is connected to the amplifier circuit, and the amplifier circuit is connected to the analog-to-digital converter.

[0009] The support has a double-layer structure, with the sliding device located on the upper layer and the material rack on the lower layer; the cylinder is installed below the sliding device; the hammer is installed at the end of the piston rod of the cylinder; the PLC control box is connected to the sliding device and the array cylinder respectively.

[0010] Preferably, the sliding device includes a slide table, a cylinder bracket, a slide rail, a timing belt, a slide table motor, a motor bracket, a slide table slider, a coupling, a driving wheel, and a driven wheel;

[0011] The slide table is installed on both sides of the upper layer of the bracket, the slide rail is set on the slide table on both sides, the slide table slider is installed on the slide rail, the driving wheel and the driven wheel are respectively installed at both ends of the slide rail, the timing belt is fixed to the slide table slider, and the two ends of the timing belt (13) are respectively connected to the driving wheel and the driven wheel, one end of the coupling is fixed to the rotating shaft of the driving wheel, and the other end of the coupling is fixed to the rotating shaft of the slide table motor; the two ends of the cylinder bracket are fixed on the slide table slider on both sides.

[0012] The slide block is arranged in three parallel groups, and there are nine array cylinders. Each group of slide block drives three array cylinders to move.

[0013] The present invention provides a plywood internal quality detection device based on acoustic emission. The device uses an array of cylinders to strike the plywood to make it produce sound, and a sound pickup device collects the sound wave signal. The sound acquisition device consists of a sound-generating, sound-pickup, and control device. With the assistance of this device in collecting sound, internal defects of the plywood can be comprehensively detected.

[0014] This invention solves the problems of large errors, low efficiency and high cost of traditional manual grading, enabling plywood sorting to be automated, standardized and scaled up, and has broad market application prospects. Attached Figure Description

[0015] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the present invention and, together with the description, serve to explain the principles of the present invention.

[0016] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 A schematic diagram of the overall structure of the sound acquisition component provided by this utility model;

[0018] Figure 2 A partial structural diagram of the sound-generating device provided by this utility model;

[0019] Figure 3 A schematic diagram of the overall structure of the sound-generating device provided by this utility model. Detailed Implementation

[0020] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this invention. Rather, they are merely examples of systems consistent with some aspects of this invention as detailed in the appended claims.

[0021] In-depth research on plywood revealed significant differences in its natural frequencies depending on the bonding performance. Plywood with good internal bonding exhibits higher natural frequencies, while plywood with internal defects such as delamination, bulges, and separation has relatively lower natural frequencies. The natural frequency of a material directly affects its response to external vibrations. Well-bonded plywood produces a higher concentration of high-frequency components in its vibration spectrum, while poorly bonded plywood produces a lower concentration of high-frequency components. Based on this, a method for identifying internal defects in plywood using characteristic sound was designed. This method utilizes an array of cylinders to strike the plywood, generating sound. Sound waves are collected using a pickup device, and Fourier transform and deep neural networks are employed to identify the state and distribution patterns of defects within the plywood.

[0022] The acoustic emission-based plywood internal quality inspection device uses hammers 9 mounted on array cylinders 23 to strike plywood 8, causing it to vibrate and generate sound. Sound wave signals are collected by a sound pickup device. Then, through Fourier transform and deep neural network analysis, the device identifies internal defects and their distribution patterns within the plywood, achieving automatic and efficient identification of cracked, hollow, and bulging plywood. Specifically, it achieves automatic plywood grading through the following three steps: (1) sound acquisition from the plywood, (2) sound feature extraction from the plywood, and (3) efficient identification of internal defects in the plywood. This solves the problems of large errors, low efficiency, and high costs associated with traditional manual grading, enabling automated, standardized, and large-scale plywood sorting, and has broad market application prospects.

[0023] The sound acquisition system consists of a sound-generating device, a sound-collecting device, and a control device. The sound-generating device comprises an array cylinder 23, a hammer 9, a support 6, a sliding device, and a material rack 6. The support 21 has a double-layer structure, with the sliding device located on the upper layer and the material rack 6 located on the lower layer.

[0024] Furthermore, the sliding device comprises a slide table 2, a slide rail 14, a synchronous belt 13, a slide table motor 17, a motor bracket 19, a slide table slider 12, a coupling 18, a driving wheel 11, and a driven wheel 15; the cylinder bracket 3 is fixed at both ends to the slide table slider 12, and the cylinder 23 is installed below the cylinder bracket 3; the hammer 9 is installed at the piston rod end connection of the cylinder. The slide table slider has three sets, each set driving three array cylinders to move, and the nine array cylinders achieve complete coverage of the plywood being inspected.

[0025] The pickup device uses a piezoelectric ceramic sensor 7. The electrical signal collected by the piezoelectric ceramic sensor 7 is amplified by an amplifier circuit, converted from analog to digital by an analog-to-digital converter, and transmitted to the industrial control computer 5 through a signal acquisition card.

[0026] The control device mainly consists of a PLC control box 1. The box contains a CPU, memory, and input / output interfaces. The CPU executes preset programs, and the memory stores relevant data. The input interfaces receive instructions and signals, and the output interfaces control the slide motor, cylinders, etc. Parameters such as slide speed and cylinder striking frequency can be flexibly set, and the operating status can be monitored, with timely alarms and protection in case of abnormalities.

[0027] By controlling the cylinder to drive the hammer to strike the plywood and produce sound, the slide rail can move the cylinder to different positions to strike the plywood, comprehensively detect the defects inside the plywood, and realize the grading of plywood of different qualities.

[0028] Specifically, the sound acquisition from plywood includes the following steps:

[0029] Place the plywood in a stable environment free from significant external interference, ensuring there are no strong airflows, vibration sources, or excessive noise to create favorable conditions for accurate sound wave signal acquisition. Use an array of nine cylinders and hammers positioned above the plywood to strike it in a predetermined sequence and with varying force. Activate a high-sensitivity piezoelectric ceramic sensor positioned directly beneath the plywood to acquire the sound wave signal generated during the strikes. The piezoelectric ceramic generates an electrical charge signal when subjected to the mechanical stress of sound vibrations. This signal is typically weak and requires amplification before further processing. Connect the two electrodes of the piezoelectric ceramic to the circuit and select a suitable operational amplifier chip, such as the LM358. It has two independent amplifiers, allowing you to choose one for single-ended amplification or use both amplifiers for differential amplification as needed. Connect the inverting input of the operational amplifier to the output through a resistor, forming a voltage follower or amplifier. The amplifier gain can be set by adjusting the value of the feedback resistor. The gain calculation formula is: Gain = 1 + Rf / Rin, where Rf is the feedback resistor and Rin is the input resistance. The signal amplifier employs specialized electronic amplification circuitry to amplify weak acoustic signals. The acquired signal is first transmitted to the signal amplifier, which amplifies the weak acoustic signal to enhance its strength and stability. The acquired signal is then transmitted to the analog-to-digital converter (ADC). The ADC converts the analog signal into a digital signal, a process involving sampling and quantization. Sampling involves taking values ​​from the analog signal at specific time intervals to obtain a series of discrete sample points. Quantization converts the amplitude of each sample point into a digital code, typically using binary encoding. Through ADC conversion, digital sound signals from nine areas of the plywood are obtained. These digital signals can be transmitted to a computer via data transmission lines (such as serial communication cables or Ethernet). Signal acquisition software is installed on the computer. This software receives and processes the digital signals from the ADC and displays the waveform, spectrum, and other information in a clear and intuitive manner in real time. Technicians can clearly observe signal changes and characteristics through the software interface, and further analyze and process the signal, calculating characteristic parameters, performing pattern recognition, etc., to gain a deeper understanding of the acoustic characteristics and quality of the plywood.

[0030] The above description is only a preferred embodiment of the present utility model. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present utility model, and these changes and modifications should also be considered within the protection scope of the present utility model.

Claims

1. An auxiliary device for detecting the internal quality of plywood based on acoustic emission, characterized in that, include: A sound-generating device and a sound-collecting device, wherein the sound-generating device includes: a PLC control box (1), an array cylinder (23), a hammer (9), a bracket (21), a sliding device, and a material rack (6); the sound-collecting device includes a piezoelectric ceramic sensor (7), an amplifier circuit, and an analog-to-digital converter; the piezoelectric ceramic sensor (7) is installed below the material rack (6); the piezoelectric ceramic sensor (7) is connected to the amplifier circuit, and the amplifier circuit is connected to the analog-to-digital converter; the bracket (21) has a double-layer structure, the sliding device is set on the upper layer of the bracket (21), and the material rack (6) is set on the lower layer of the bracket (21); the array cylinder (23) is installed on the lower part of the sliding device; the hammer (9) is installed on the piston rod end of the cylinder; the PLC control box (1) is connected to the sliding device and the array cylinder (23) respectively.

2. The auxiliary device for detecting the internal quality of plywood based on acoustic emission according to claim 1, characterized in that, The sliding device includes a slide table (2), a cylinder bracket (3), a slide rail (14), a timing belt (13), a slide table motor (17), a motor bracket (19), a slide table slider (12), a coupling (18), a drive wheel (11), and a driven wheel (15). The slide table (2) is installed on both sides of the upper layer of the bracket (21). The slide rail (14) is set on the slide table (2) on both sides. The slide table slider (12) is installed on the slide rail. The drive wheel (11) and the driven wheel (15) are respectively installed at both ends of the slide rail (14). The timing belt (13) is fixed to the slide table slider (12), and both ends of the timing belt (13) are connected to the drive wheel (11) and the driven wheel (15) respectively. One end of the coupling (18) is fixed to the rotating shaft of the drive wheel (11), and the other end of the coupling (18) is fixed to the rotating shaft of the slide table motor (17). The cylinder bracket (3) is fixed at both ends on the slide table slider (12) on both sides.

3. The auxiliary device for detecting the internal quality of plywood based on acoustic emission according to claim 2, characterized in that, The slide block (12) is arranged in three parallel groups, and there are nine array cylinders. Each group of slide block (12) drives three array cylinders to move.

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