Automatic belt tensioning system and method based on vibration frequency analysis

Abstract

The invention relates to the technical field of mechanical transmission control, in particular to an automatic belt tensioning system and method based on vibration frequency analysis, and the system comprises an excitation device which is used for applying transient mechanical excitation to a belt so as to excite the free vibration of the belt; the non-contact sensor is used for collecting a vibration signal generated by free vibration; the control unit is connected with the excitation device and the non-contact sensor and is configured to control the excitation device and the non-contact sensor; controlling the excitation device to act; spectral analysis is conducted on the collected vibration signals to extract the vibration fundamental frequency of the belt; calculating a real-time tension value of the belt according to the vibration fundamental frequency and pre-stored belt parameters; the real-time tension value is compared with a target tension value, and when the deviation exceeds a preset dead zone threshold value, a control signal is generated based on a control algorithm; and the executing mechanism is connected with the control unit and is used for adjusting the center distance between two wheels for driving the belt according to the control signal so as to adjust the tension of the belt. And stable power output of a press transmission system is guaranteed.

Description

Technical Field

[0001] This application relates to the field of mechanical transmission control technology, specifically to an automatic belt tensioning system and method based on vibration frequency analysis. Background Technology

[0002] High-speed and efficient CNC fully automated stamping lines have been widely used in automobile manufacturing and other fields. As the core equipment of the production line, the press's transmission system must have high reliability and stability. As a key component for transmitting power, the precise control of the transmission belt's tension directly affects the equipment's operating efficiency and lifespan.

[0003] Currently, the industry primarily employs two technical approaches to control the belt tension between the press motor and flywheel. One approach relies on periodic manual inspection and adjustment. This method suffers from significant lag, cannot achieve real-time response, and its adjustment accuracy is affected by the operator's experience, making it difficult to meet the high tension stability requirements of modern automated production lines. The other approach uses an automatic tensioning system based on tension sensors. While this system achieves automatic adjustment, the tension sensors typically employ a contact measurement principle. Under the harsh operating conditions of high vibration and dust associated with press operation, these sensors are prone to wear, drift, and even damage, leading to decreased measurement reliability, increased maintenance costs, and difficulty in guaranteeing long-term stability.

[0004] Therefore, existing technical solutions still face challenges in achieving long-term stable, economical, reliable, and precise automatic control of press belt tension. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides an automatic belt tensioning system and method based on vibration frequency analysis, which solves the problems of poor reliability and short lifespan of traditional contact tension sensors under this working condition.

[0006] In a first aspect, the present invention provides an automatic belt tensioning system based on vibration frequency analysis, comprising: An excitation device is used to apply transient mechanical excitation to the belt to induce its free vibration; Non-contact sensors are used to collect vibration signals generated by free vibrations; The control unit, connected to the excitation device and the non-contact sensor, is configured to; Control the operation of the excitation device; The acquired vibration signal is subjected to spectrum analysis to extract the fundamental frequency of the belt vibration; the real-time tension value of the belt is calculated based on the fundamental frequency of vibration and the pre-stored belt parameters; the real-time tension value is compared with the target tension value, and when the deviation exceeds the preset dead zone threshold, a control signal is generated based on the control algorithm. An actuator, connected to the control unit, is used to adjust the belt tension by adjusting the center distance between the two pulleys driving the belt according to the control signal.

[0007] As a further limitation of the technical solution of the present invention, the excitation device includes a pneumatic hammer, an air supply unit, and a pressure control unit; Air supply unit, used to provide compressed air; The pressure control unit includes a pressure regulating valve and a high-speed solenoid valve; The pressure regulating valve has its inlet connected to the air supply unit via a pipeline, and its outlet connected to the air inlet of the high-speed solenoid valve via a pipeline. The working port of the high-speed solenoid valve is connected to the air inlet of the pneumatic hammer via a pipeline. The pressure regulating valve is used to set and stably deliver the working pressure to the pneumatic hammer. The high-speed solenoid valve is controlled by the control unit and is used to control the on / off of compressed air to trigger the action of the pneumatic hammer. The hammerhead of the pneumatic hammer is aligned with the slack side of the belt, and its striking direction is perpendicular to the belt plane.

[0008] The air supply unit, in conjunction with the pressure control unit, can precisely set and stabilize the working pressure of the pneumatic hammer, ensuring consistent striking force each time and avoiding the impact of excitation intensity fluctuations on the effectiveness of the vibration signal, thus improving the repeatability and accuracy of tension measurement. The high-speed solenoid valve has a fast response speed and can be precisely controlled by the control unit to achieve rapid on / off switching of compressed air, enabling the pneumatic hammer to produce transient, short striking motions, efficiently stimulating free vibration of the belt without causing continuous damage to the belt. In this application, the high-speed solenoid valve refers to a solenoid valve with a switching time of less than 10ms.

[0009] The pneumatic hammer head is aligned with the slack side of the belt, and the striking direction is perpendicular to the belt plane. This maximizes the conversion of kinetic energy into lateral vibration of the belt, preventing slippage or tangential force, ensuring sufficient vibration signal strength and minimal interference, and further improving the reliability of sensor detection. A high-speed solenoid valve is installed close to the pneumatic hammer to reduce airflow delay, balancing response speed with environmental friendliness, and meeting the noise reduction requirements of industrial sites.

[0010] As a further limitation of the technical solution of the present invention, the control unit is configured to extract the fundamental frequency of vibration through the following steps: Windowing and detrending term preprocessing are applied to the vibration signal; The preprocessed signal is subjected to FFT to obtain the spectrum, and then converted into amplitude spectrum or power spectral density; Local maxima are identified within a preset effective frequency range, and the peak frequency with the largest amplitude and a signal-to-noise ratio higher than the threshold is selected as the candidate fundamental frequency. The final fundamental frequency of vibration is confirmed by verifying whether there are harmonic components that are integer multiples of the candidate fundamental frequency value in the spectrum.

[0011] Windowing in the vibration signal preprocessing stage effectively reduces spectral leakage, and detrending eliminates the interference of linear trends on low-frequency components, providing a clean signal foundation for subsequent spectral analysis and improving the accuracy of fundamental frequency identification. After FFT transformation, amplitude or power spectral density is generated, facilitating intuitive identification of spectral peaks. Combining this with filtering local maxima within a preset effective frequency range allows for rapid elimination of irrelevant interference such as environmental noise, improving fundamental frequency identification efficiency. A dual verification mechanism is established, using both maximum amplitude and acceptable signal-to-noise ratio as fundamental frequency candidates, followed by harmonic verification to avoid misidentification based on a single peak value, significantly improving the reliability and stability of vibration fundamental frequency extraction.

[0012] As a further limitation of the technical solution of the present invention, the actuator includes a servo motor, a ball screw pair, and a linear guide pair; the output shaft of the servo motor is connected to the screw of the ball screw pair through an elastic coupling; the nut of the ball screw pair is fixedly connected to a sliding plate, the sliding plate is used to install one of the drive motor or flywheel, and is supported and guided by the linear guide pair.

[0013] A servo motor, in conjunction with a ball screw pair, converts rotary motion into linear motion, enabling displacement control of the sliding plate and precise adjustment of belt tension, thus solving the problem of insufficient precision in traditional adjustment methods. The flexible coupling buffers the impact load during servo motor startup, compensates for minor alignment errors during installation, protects the servo motor and ball screw pair, and extends the overall service life of the actuator.

[0014] The linear guide pair provides stable support and guidance for the sliding plate, ensuring smooth and offset movement and preventing the center distance adjustment accuracy from being affected by mechanism jamming or wobbling, thus guaranteeing precise tension adjustment. The sliding plate is used to mount the drive motor or flywheel. Its flexible structural design allows for adaptability to existing equipment layouts without requiring reconstruction of the transmission system, reducing equipment modification costs and improving the engineering applicability of the solution.

[0015] As a further limitation of the technical solution of the present invention, the actuator changes the center distance through the following process: The control unit controls the servo motor to rotate in a set direction and angle; The torque of the servo motor is transmitted through the flexible coupling, driving the ball screw pair to rotate. The rotation of the lead screw drives the nut it meshes with to produce linear motion; The nut drives the sliding plate, which is fixedly connected to it, to move linearly along the linear guide pair. The movement of the sliding plate causes the drive motor or flywheel mounted on it to move, thereby changing the center distance between the drive motor and the flywheel.

[0016] The control unit precisely controls the rotation direction and angle of the servo motor, and combined with the motion conversion characteristics of the ball screw pair, achieves quantitative adjustment of the center distance, ensuring that the tension adjustment range accurately matches the deviation requirements. The power transmission path is servo motor → flexible coupling → ball screw → nut → sliding plate, with low power loss and rapid response to control commands, enabling rapid adjustment of the center distance and improving the response speed of tension control.

[0017] The sliding plate moves smoothly along the linear guide pair, driving the drive motor or flywheel to move synchronously. The center distance adjustment process is smooth and will not cause instantaneous impact on the belt, avoiding belt damage or transmission fluctuations caused by sudden tension changes, and ensuring stable system operation.

[0018] As a further limitation of the technical solution of the present invention, the control algorithm is a PID control algorithm, and the control unit is configured to execute the PID control algorithm only when the absolute value of the deviation exceeds the preset dead zone threshold.

[0019] The PID control algorithm features coordinated proportional, integral, and derivative regulation. The proportional term responds quickly to deviations, the integral term eliminates steady-state errors, and the derivative term suppresses overshoot. The combination of these three terms enables precise and rapid tension correction, ensuring tension stability near the target value. PID operation is only initiated when the absolute value of the deviation exceeds a preset dead-zone threshold, effectively filtering out minor tension fluctuations and preventing unnecessary frequent starts, stops, and oscillations of the actuator. This reduces mechanical wear and extends the service life of core components such as servo motors and ball screws. The coordinated design of the dead-zone threshold and the PID algorithm balances system stability and control accuracy, preventing tension fluctuations caused by over-adjustment while enabling rapid adjustment when tension deviations exceed the limit.

[0020] As a further limitation of the technical solution of the present invention, the control unit pre-stores the belt linear density. and effective vibration length And configured according to the formula Calculate the real-time tension value, where The fundamental frequency of the vibration is denoted as .

[0021] Secondly, the present invention also provides an automatic belt tensioning method based on vibration frequency analysis, applied to the system described in the first aspect, the method comprising the following steps: A transient mechanical excitation is applied to the belt by an excitation device to induce free vibration in the belt; The vibration signal generated by the free vibration is acquired by a non-contact sensor; The vibration signal is subjected to spectral analysis to extract the fundamental frequency of the belt vibration, and the real-time tension value of the belt is calculated based on the fundamental frequency of the vibration and the pre-stored belt parameters. The real-time tension value is compared with the target tension value. When the deviation exceeds the preset dead zone threshold, a control command is generated based on the control algorithm, and the actuator is driven to change the belt tension by adjusting the center distance between the two pulleys driving the belt.

[0022] As a further limitation of the technical solution of the present invention, the steps of performing spectrum analysis on the vibration signal, extracting the fundamental frequency of the belt vibration, and calculating the real-time tension value of the belt based on the fundamental frequency of the vibration and the pre-stored belt parameters include: The vibration signal is preprocessed by windowing and detrending term removal; Perform a Fast Fourier Transform on the preprocessed signal to obtain the spectrum; Within the spectrum, candidate fundamental frequencies are identified within a preset effective frequency range, and the final fundamental frequency of vibration is confirmed by verifying the presence of harmonic components at their integer multiples. Using formula Calculate the real-time tension value; in, The linear density of the belt. For the effective vibration length, This is the fundamental frequency of vibration.

[0023] As a further limitation of the technical solution of the present invention, in the step of changing the belt tension by adjusting the center distance between the two pulleys of the drive belt, a servo motor is controlled to drive the ball screw pair to convert the rotational motion into linear motion, thereby pushing the sliding plate of the bearing motor or flywheel to move along the linear guide rail to change the center distance.

[0024] As can be seen from the above technical solutions, this application has the following advantages: by adopting the indirect measurement method of transient mechanical excitation, non-contact sensing and spectrum analysis, it completely avoids the defects of traditional contact tension sensors that are prone to wear, have poor reliability and short life under the harsh working conditions of presses, and realizes long-term stable monitoring of belt tension, which is suitable for complex industrial operating environments.

[0025] By extracting the fundamental frequency of vibration through spectrum analysis and calculating the tension in combination with belt parameters, the measurement accuracy is high, solving the problem of inaccurate control in traditional solutions and ensuring stable power output of the press transmission system.

[0026] By introducing a closed-loop control logic that combines a preset dead zone threshold with a control algorithm, we can avoid frequent actuator movements caused by minor deviations, extend component life, and improve system stability. At the same time, we can quickly respond and adjust when the tension deviation exceeds the limit, thus achieving fully automatic and precise tension control.

[0027] By adjusting the tension of the two wheels by adjusting the center distance, the structure is highly adaptable and can be directly applied to the transmission belt between the motor and flywheel of a high-power press without requiring major modifications to existing equipment. Attached Figure Description

[0028] To more clearly illustrate the technical solution of this application, the accompanying drawings used in the description will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a connection diagram of the system provided in an embodiment of the present invention.

[0030] Figure 2 This is a schematic diagram of the implementing mechanism.

[0031] Figure 3 This is an enlarged schematic diagram of part A in the actuator.

[0032] Figure 4 This is a flowchart illustrating the method provided in an embodiment of the present invention.

[0033] In the diagram, 1 is an air compressor, 2 is a pressure regulating valve, 3 is a two-position three-way solenoid valve, 4 is a pneumatic hammer, 5 is a drive motor, 6 is a flexible coupling, 7 is a support device, 8 is a ball screw pair, 9 is a tensioning position, 10 is a servo motor, 11 is a flywheel, 12 is a sliding plate, and 13 is a linear guide pair. Detailed Implementation

[0034] To make the purpose, features, and advantages of this application more apparent and understandable, specific embodiments and accompanying drawings will be used to clearly and completely describe the technical solution protected by this application. Obviously, the embodiments described below are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0035] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this application and in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0036] like Figure 1 , Figure 2 and Figure 3 As shown, this embodiment of the invention provides an automatic belt tensioning system based on vibration frequency analysis, comprising: An excitation device is used to apply transient mechanical excitation to the belt to induce its free vibration; Non-contact sensors are used to collect vibration signals generated by free vibrations; The control unit, connected to the excitation device and the non-contact sensor, is configured to; Control the operation of the excitation device; The acquired vibration signal is subjected to spectrum analysis to extract the fundamental frequency of the belt vibration; the real-time tension value of the belt is calculated based on the fundamental frequency of vibration and the pre-stored belt parameters; the real-time tension value is compared with the target tension value, and when the deviation exceeds the preset dead zone threshold, a control signal is generated based on the control algorithm. An actuator, connected to the control unit, is used to adjust the belt tension by adjusting the center distance between the two pulleys driving the belt according to the control signal.

[0037] In this embodiment of the invention, the excitation device includes a pneumatic hammer, an air supply unit, and a pressure control unit: The air supply unit is used to provide compressed air; the core component of the air supply unit is the air compressor 1. The pressure control unit includes a pressure regulating valve 2 and a high-speed solenoid valve, namely a two-position three-way solenoid valve 3; The pressure regulating valve 2 is connected to the air compressor 1 via a pipeline, and its outlet is connected to the air inlet of the two-position three-way solenoid valve 3 via a pipeline. The working port of the two-position three-way solenoid valve 3 is connected to the air inlet of the pneumatic hammer 4 via a pipeline. The pressure regulating valve 2 is used to set and stably deliver the working pressure to the pneumatic hammer 4. The two-position three-way solenoid valve 3 is controlled by the control unit and is used to control the on / off of compressed air to trigger the action of the pneumatic hammer 4. The hammer head of the pneumatic hammer 4 is aligned with the slack side of the belt, and its striking direction is perpendicular to the belt plane.

[0038] The excitation device uses a pneumatic impact unit. It consists of a factory air compressor; airflow passes through a precision pressure regulating valve, a two-position three-way solenoid valve, and finally connects to the air hammer body, aligning the hammerhead with the non-working surface of the middle section of the belt, with the impact direction perpendicular to the belt plane. An acoustic sensor is mounted near the air hammer via a bracket to ensure clear detection of belt vibration. The air compressor serves as the system's power source, providing a stable supply of compressed air. This air compressor can be a standalone small air compressor for this system or connected to the factory's existing centralized air supply network. Its output interface is connected to the subsequent pressure regulating unit via the main air supply line. A precision pressure regulating valve is installed on the main air supply line, downstream of the air compressor. Its function is to precisely set and stably deliver the working pressure to the pneumatic hammer. By rotating its adjustment knob, the pressure can be set to a specific value to ensure consistent and adjustable impact force for each strike. Its outlet is connected to the inlet of the high-speed solenoid valve via a pipeline.

[0039] The two-position three-way high-speed solenoid valve serves as the core electronic control switch in the pneumatic circuit. Its installation position should be close to the pneumatic hammer body to minimize airflow delay. Its air inlet is connected to the outlet of the pressure regulating valve via a pipeline; its working port is directly connected to the air inlet of the pneumatic hammer via a high-pressure hose; and its exhaust port is typically equipped with a silencer. The solenoid coil of the high-speed solenoid valve is connected to the digital output terminal of the control unit via an electrical connection wire. The pneumatic hammer is the final kinetic energy output component. The pneumatic hammer is securely fixed to the press frame using a rigid mounting bracket. Its installation position must meet the following requirements: Strike point: The hammer head (end of the piston rod) should be aligned with the middle section of the slack side of the belt.

[0040] Strike direction: The movement trajectory of the hammer head should be perpendicular to the plane of the belt at that point to ensure that the energy is converted into the lateral vibration of the belt most effectively, avoiding slippage or the generation of tangential force.

[0041] In this embodiment of the invention, the specific implementation process of the transient tapping excitation is as follows: Step 1: Preparation Once the system is powered on, the air compressor continues to run, maintaining the air source pressure.

[0042] The pressure regulating valve stabilizes the system working pressure at a preset value; the high-speed solenoid valve is in a normally closed, de-energized state. Its air inlet is closed, while the working port and exhaust port are connected. Residual air in the pneumatic hammer cylinder is vented through the solenoid valve, and the hammer head, under the action of the internal return spring, is in its fully retracted initial position.

[0043] Step 2: Trigger signal output When the internal timer of the control unit reaches the preset sampling period, the PLC CPU sends a high-level pulse signal to the designated digital output point. The width of this pulse (i.e., the solenoid valve opening time) is precisely set, typically from 50ms to 200ms.

[0044] Step 3: Solenoid valve operation and air supply The high-level pulse signal is sent to the coil of the high-speed solenoid valve. The coil is energized, generating a magnetic field that drives the valve core to complete the switching in a very short time.

[0045] The valve core actuates to connect the air inlet and the working port, while simultaneously closing the exhaust port. Pre-pressurized compressed air instantly flows through the high-pressure hose into the rear chamber of the pneumatic hammer.

[0046] Step Four: Hammer Acceleration and Striking Compressed air acts on the piston end face of the pneumatic hammer, generating a powerful thrust that is much greater than the preload of the return spring. Under this thrust, the piston (along with the hammer head) accelerates at high speed along the cylinder guide tube, gaining maximum kinetic energy within a very short stroke (usually 10-50mm).

[0047] The hammer strikes the pre-aligned belt surface at extremely high speed. This impact is a single, brief, transient process, lasting only a few milliseconds, effectively transferring energy to the belt and exciting it to produce a free vibration with a large amplitude and rapid decay. This vibration is the effective signal required for subsequent measurements.

[0048] Step 5: Cut off the air supply and reset the hammer. When the pulse signal output by the control unit ends, the high-speed solenoid valve coil is de-energized.

[0049] Under the action of its own return spring, the valve core quickly returns to its initial normally closed state. That is, the connection between the air inlet and the working port is cut off, while the working port is reconnected to the exhaust port. The compressed air in the rear chamber of the pneumatic hammer cylinder is quickly discharged into the atmosphere through the exhaust port of the solenoid valve and the muffler, and the pressure inside the chamber drops sharply.

[0050] Under the action of the return spring and with the assistance of the negative pressure inside the cylinder, the hammer head quickly retracts to its initial position, preparing for the next strike.

[0051] Step Six: Loop and Wait After one tapping excitation is completed, the system enters a waiting state for the next sampling cycle. The control unit then processes the signals acquired by the non-contact sensor and executes the tension calculation and adjustment logic.

[0052] Through the above-mentioned precise control, the periodic, non-contact automatic monitoring and adjustment of belt tension is achieved, ensuring the long-term, stable and efficient operation of the press transmission system.

[0053] In this embodiment of the invention, the non-contact sensor is an acoustic sensor.

[0054] In this embodiment of the invention, the actuator includes a servo motor 10, a ball screw assembly 8, and a linear guide assembly 13; the output shaft of the servo motor 10 is connected to the screw of the ball screw assembly 8 via an elastic coupling 6; the nut of the ball screw assembly 8 is fixedly connected to a sliding plate, the sliding plate being used to mount one of the drive motor or flywheel, and is supported and guided by the linear guide assembly 13.

[0055] The actuator changes the center distance through the following process: The control unit controls the servo motor 10 to rotate in a set direction and angle; The torque of the servo motor 10 is transmitted through the elastic coupling 6, driving the lead screw of the ball screw pair 8 to rotate; the rotation of the lead screw drives the nut meshing with it to produce linear motion; the nut drives the sliding plate 12 fixedly connected to it to move linearly along the linear guide pair 13. The movement of the sliding plate 12 causes the drive motor 5 or flywheel 11 mounted on it to move, thereby changing the center distance between the drive motor 5 and the flywheel 11.

[0056] In the automatic belt tensioning system, tension position 9 is a functional position used to identify the key section where the belt tension has actually changed. The core objective of the tensioning system is to adjust the belt tension between the pulley of the drive motor 5 and the pulley of the flywheel 11. The belt tension is closely related to the center distance between the drive motor 5 and the flywheel 11. When the center distance changes, the belt will be tightened or loosened accordingly, thereby adjusting the tension. The servo motor 10 serves as the power source for the entire actuator. Its function is to drive the components related to the drive motor 5 or the flywheel 11 through a series of transmission components (elastic coupling 6, ball screw pair 8, etc.), thereby changing the center distance between the drive motor 5 and the flywheel 11. Structurally, the sliding plate 12 is used to mount one of the drive motor 5 or the flywheel 11. When the servo motor 10 rotates according to the command of the control unit, the power is transmitted sequentially to the ball screw pair 8 through the elastic coupling 6, causing the ball screw pair 8 to rotate. The nut of the ball screw pair 8 drives the sliding plate 12, which is fixedly connected to it, to move along the linear guide pair 13. The movement of the sliding plate 12 directly drives the drive motor 5 or flywheel 11 mounted on it to move, thereby changing the distance between the drive motor 5 and the flywheel 11, that is, the center distance between them. The correct path of power transmission is as follows: the servo motor 10 outputs rotational power, which is transmitted to the shaft of the ball screw assembly 8 through the flexible coupling 6, driving the ball screw assembly 8 to rotate. The nut of the ball screw assembly 8 is fixedly connected to the sliding plate 12. When the screw rotates, the nut makes linear motion, thereby driving the sliding plate 12 to move along the linear guide assembly 13. If the drive motor 5 is mounted on the sliding plate 12, then the drive motor 5 will move; if the flywheel 11 is mounted on it, then the flywheel 11 will move, ultimately changing the center distance between the drive motor 5 and the flywheel 11.

[0057] Under the command of the control unit, the aforementioned actuator achieves belt tensioning and loosening by changing the center distance between the motor and the flywheel. The specific coordination process is as follows: 1. Tensioning process (when the measured tension is lower than the target value): Control commands: The PID algorithm of the control unit calculates the angle and direction that the servo motor needs to rotate.

[0058] Motor drive: The PLC sends the corresponding pulse sequence and direction signal to the servo driver. The servo motor rotates precisely clockwise by the set angle according to the instructions.

[0059] Torque transmission: The output torque of the servo motor is smoothly transmitted to the lead screw shaft of the ball screw pair through a flexible coupling. The elastic element of the coupling effectively buffers the impact during startup and compensates for minor alignment errors.

[0060] Motion conversion: The lead screw shaft of the ball screw pair begins to rotate. Since the nut of the lead screw is fixed to the motor sliding plate through the connecting piece, and the sliding plate is constrained by the linear guide pair and can only move linearly, the rotating lead screw drives the nut to move linearly.

[0061] Center distance adjustment: The linear movement of the nut pushes or pulls the motor sliding plate fixed to it, causing the entire slide to move along the linear guide rail away from the flywheel. This increases the center distance between the drive motor pulley and the flywheel pulley, gradually tightening the belt and increasing its tension.

[0062] 2. Relaxation process (when the measured tension is higher than or equal to the target value): The process is the reverse of the tensioning process. The control unit commands the servo motor to rotate in the opposite direction (counterclockwise). Power is also transmitted to the ball screw pair via the coupling. The nut of the ball screw pair drives the motor sliding plate to move towards the flywheel, thereby reducing the center distance between the drive motor and the flywheel, loosening the belt, and its tension decreases accordingly. Through this precise electronic control method, the system can achieve accurate adjustment of belt tension, and by utilizing the inherent self-locking characteristic of the ball screw pair, it can maintain its position for a long time without power supply after adjustment, thus maintaining stable tension.

[0063] Servo motors themselves have extremely high position, speed and torque control precision. When combined with ball screw pairs, they convert rotary motion into linear displacement, enabling extremely precise control of the position of the motor sliding plate. This allows for accurate and fine-tuning of belt tension, avoiding under- or over-adjustment.

[0064] The ball screw pair, through a small lead angle amplification, can convert the relatively small output torque of the servo motor into a huge linear thrust, sufficient to overcome the inertial static friction of the heavy motor and flywheel, propelling it to move smoothly. The entire transmission chain is rigidly connected, with a robust structure, small backlash, and rapid response.

[0065] Ball screw assemblies possess excellent self-locking properties. Once properly adjusted, even under the immense impact and vibration of a press, the screw nut will not easily move due to external forces. It can reliably maintain its adjusted position for a long time without continuous power consumption, ensuring sustained tension stability.

[0066] In this embodiment of the invention, the control unit is configured to extract the fundamental vibration frequency through the following steps: Windowing preprocessing is applied to the vibration signal; The original time-domain signalx ( t Multiply by a window function w ( t The window function uses the commonly used Hanning window; The preprocessed signal is subjected to FFT to obtain the spectrum, and then converted into amplitude spectrum or power spectral density;

[0067] in, The spectrum is in complex form. N This represents the number of sampling points; Amplitude spectrum

[0068] Power spectral density , The sampling frequency.

[0069] Local maxima are identified within a preset effective frequency range, and the peak frequency with the largest amplitude and a signal-to-noise ratio higher than the threshold is selected as the candidate fundamental frequency. For power spectral density or amplitude spectrum Scan the array, for the first... k At frequency points, if the following conditions are met:

[0070] at this time, k It is a local maximum point, and its corresponding frequency is This leads to a list of candidate peaks. In the list Find the power in the middle. The maximum peak value, and the required frequency of that peak value. It must be within the preset effective frequency range Within this range, the estimate is based on parameters such as belt length and material. The signal-to-noise ratio of this peak value must be higher than an empirical threshold.

[0071] Fundamental frequency candidate value The frequency corresponding to the peak value that satisfies the following conditions:

[0072] in, It is the signal-to-noise ratio threshold.

[0073] The final fundamental frequency of vibration is confirmed by verifying whether there are harmonic components that are integer multiples of the candidate fundamental frequency value in the spectrum.

[0074] The control unit has a pre-stored belt linear density. and effective vibration length And configured according to the formula Calculate the real-time tension value, where The fundamental frequency of the vibration is denoted as .

[0075] The derivation process is as follows: Establish the wave equation for string vibration: for a length of... Linear density is The wave equation for the transverse vibration of a string with its two ends fixed is:

[0076] in, Let the coordinates of a point on the chord be... At that moment Lateral displacement, The axial tension of the string. Let be the linear density of the chord, i.e., the mass per unit length.

[0077] Solving the eigensols of the wave equation: Solve the above partial differential equation using the method of separation of variables, combined with the boundary conditions where both ends are fixed ( and hour, The natural frequency of the string can be obtained as: ( ) in, The frequency corresponding to time That is, the fundamental frequency; The frequency is the harmonic frequency.

[0078] Derivation of the tension calculation formula: For the fundamental frequency formula ( By performing a displacement deformation, the tension can be obtained. The expression for tension. It is the actual tension of the transmission belt between the press motor and the flywheel, which is the target physical quantity to be measured in this application.

[0079] In some embodiments, the control algorithm is a PID control algorithm, and the control unit is configured to execute the PID control algorithm only when the absolute value of the deviation exceeds the preset dead zone threshold.

[0080] In fact, the control objective of this application is to control the real-time tension of the belt. Stabilize at the preset target value .

[0081] Calculate the tension deviation for the current control cycle:

[0082] This deviation This indicates the difference between the current tension and the target value. A positive value indicates insufficient tension, which needs to be tightened; a negative value indicates excessive tension, which needs to be relaxed.

[0083] if Then let =0, keep the actuator in its original position. For the first The controller output calculated over each control cycle This is the dead zone threshold, a preset positive value.

[0084] if If so, then continue with the subsequent PID calculations.

[0085] The positional digital PID algorithm is used to calculate the control quantity. Its discretization calculation formula is as follows:

[0086] To control the cycle, , , These are the proportional, integral, and derivative coefficients, and are the pre-tuned controller parameters.

[0087] Proportional Term It generates a control effect proportional to the current deviation. It responds quickly to deviations and reduces static error. Excessive values ​​may cause system overshoot or oscillation.

[0088] Integral term The integral term sums (integrates) all historical deviations to eliminate the steady-state error (static error) of the system. As long as the deviation exists, the integral term will continue to accumulate until the output is sufficient to correct the deviation to zero. It affects the speed of eliminating steady-state error, but too large an error may cause integral saturation and system instability.

[0089] Differential term It is proportional to the rate of change of the deviation (the difference between the deviation of the current period and the previous period). It predicts the future trend of the deviation and applies a damping effect in advance. It can suppress overshoot, improve system stability, and make the response process smoother. It is sensitive to measurement noise and usually needs to be used in conjunction with signal filtering.

[0090] Will Converted into pulse commands and sent to the motor servo driver, then saved. As for the next cycle .

[0091] like Figure 4As shown, this embodiment of the invention also provides an automatic belt tensioning method based on vibration frequency analysis, applied to the system described in the above embodiment. The method includes the following steps: S1. A transient mechanical excitation is applied to the belt through an excitation device to induce the belt to vibrate freely; S2. Acquire the vibration signal generated by the free vibration using a non-contact sensor; S3. Perform spectrum analysis on the vibration signal, extract the fundamental frequency of the belt vibration, and calculate the real-time tension value of the belt based on the fundamental frequency of the vibration and the pre-stored belt parameters. S4. Compare the real-time tension value with the target tension value. When the deviation exceeds the preset dead zone threshold, generate a control command based on the control algorithm and drive the actuator to change the belt tension by adjusting the center distance between the two pulleys driving the belt.

[0092] In this embodiment of the invention, in the step of applying transient mechanical excitation to the belt through an excitation device to induce the belt to vibrate freely, a pneumatic striking unit is controlled to perform a transient strike perpendicular to the plane of the belt on the slack side.

[0093] In this embodiment of the invention, the steps of performing spectral analysis on the vibration signal, extracting the fundamental frequency of the belt vibration, and calculating the real-time tension value of the belt based on the fundamental frequency and pre-stored belt parameters include: The vibration signal is preprocessed by windowing and detrending term removal; Perform a Fast Fourier Transform on the preprocessed signal to obtain the spectrum; Within the spectrum, candidate fundamental frequencies are identified within a preset effective frequency range, and the final fundamental frequency of vibration is confirmed by verifying the presence of harmonic components at their integer multiples. Using formula Calculate the real-time tension value; in, The linear density of the belt. For the effective vibration length, This is the fundamental frequency of vibration.

[0094] In this embodiment of the invention, a PID control algorithm is employed, and the PID control algorithm is only executed to generate the control command when the absolute value of the deviation exceeds the preset dead zone threshold.

[0095] In this embodiment of the invention, in the step of changing the belt tension by adjusting the center distance between the two pulleys driving the belt, a servo motor is controlled to drive the ball screw pair to convert the rotational motion into linear motion, thereby pushing the sliding plate of the carrying motor or flywheel to move along the linear guide rail to change the center distance.

[0096] Those skilled in the art will clearly understand that the techniques in the embodiments of the present invention can be implemented using software plus necessary general-purpose hardware platforms. Based on this understanding, the technical solutions in the embodiments of the present invention, or the parts that contribute to the prior art, can be embodied in the form of a software product. This computer software product is stored in a storage medium such as a USB flash drive, mobile hard drive, read-only memory (ROM), random access memory (RAM), magnetic disk, or optical disk, or other media capable of storing program code. It includes several instructions to cause a computer terminal (which may be a personal computer, server, or a second terminal, network terminal, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention.

[0097] In the embodiments provided by this invention, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between devices or units may be electrical, mechanical, or other forms.

[0098] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0099] In addition, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0100] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An automatic belt tensioning system based on vibration frequency analysis, characterized in that, include: An excitation device is used to apply transient mechanical excitation to the belt to induce its free vibration; Non-contact sensors are used to collect vibration signals generated by free vibration. The control unit is connected to the excitation device and the non-contact sensor, and is configured to; Control the operation of the excitation device; The collected vibration signal is subjected to spectrum analysis to extract the fundamental frequency of the belt vibration; the real-time tension value of the belt is calculated based on the fundamental frequency of vibration and the pre-stored belt parameters. The real-time tension value is compared with the target tension value, and a control signal is generated based on the control algorithm when the deviation exceeds the preset dead zone threshold. An actuator, connected to the control unit, is used to adjust the belt tension by adjusting the center distance between the two pulleys driving the belt according to the control signal.

2. The automatic belt tensioning system based on vibration frequency analysis according to claim 1, characterized in that, The excitation device includes a pneumatic hammer, an air supply unit, and a pressure control unit. Air supply unit, used to provide compressed air; The pressure control unit includes a pressure regulating valve and a high-speed solenoid valve; The pressure regulating valve has its inlet connected to the air supply unit via a pipeline, and its outlet connected to the air inlet of the high-speed solenoid valve via a pipeline. The working port of the high-speed solenoid valve is connected to the air inlet of the pneumatic hammer via a pipeline. The pressure regulating valve is used to set and stably deliver the working pressure to the pneumatic hammer. The high-speed solenoid valve is controlled by the control unit and is used to control the on / off of compressed air to trigger the action of the pneumatic hammer. The hammerhead of the pneumatic hammer is aligned with the slack side of the belt, and its striking direction is perpendicular to the belt plane.

3. The automatic belt tensioning system based on vibration frequency analysis according to claim 1, characterized in that, The control unit is configured to extract the fundamental frequency of vibration by the following steps: Windowing preprocessing is applied to the vibration signal; The preprocessed signal is subjected to FFT to obtain the spectrum, and then converted into amplitude spectrum or power spectral density; Local maxima are identified within a preset effective frequency range, and the peak frequency with the largest amplitude and a signal-to-noise ratio higher than the threshold is selected as the candidate fundamental frequency.

4. The automatic belt tensioning system based on vibration frequency analysis according to claim 1, characterized in that, The actuator includes a servo motor, a ball screw pair, and a linear guide pair; the output shaft of the servo motor is connected to the lead screw of the ball screw pair via a flexible coupling; the nut of the ball screw pair is fixedly connected to a sliding plate, which is used to mount one of the drive motors or flywheels and is supported and guided by the linear guide pair.

5. The automatic belt tensioning system based on vibration frequency analysis according to claim 4, characterized in that, The actuator changes the center distance through the following process: The control unit controls the servo motor to rotate in a set direction and angle; The torque of the servo motor is transmitted through the flexible coupling, driving the ball screw pair to rotate. The rotation of the lead screw drives the nut it meshes with to produce linear motion; The nut drives the sliding plate, which is fixedly connected to it, to move linearly along the linear guide pair. The movement of the sliding plate causes the drive motor or flywheel mounted on it to move, thereby changing the center distance between the drive motor and the flywheel.

6. The automatic belt tensioning system based on vibration frequency analysis according to claim 1, characterized in that, The control algorithm is a PID control algorithm, and the control unit is configured to execute the PID control algorithm only when the absolute value of the deviation exceeds the preset dead zone threshold.

7. The automatic belt tensioning system based on vibration frequency analysis according to claim 1, characterized in that, The control unit has a pre-stored belt linear density. and effective vibration length And configured according to the formula Calculate the real-time tension value, where The fundamental frequency of the vibration is denoted as .

8. A method for automatic belt tensioning based on vibration frequency analysis, characterized in that, Includes the following steps: A transient mechanical excitation is applied to the belt by an excitation device to induce free vibration in the belt; The vibration signal generated by the free vibration is acquired by a non-contact sensor; The vibration signal is subjected to spectral analysis to extract the fundamental frequency of the belt vibration, and the real-time tension value of the belt is calculated based on the fundamental frequency of the vibration and the pre-stored belt parameters. The real-time tension value is compared with the target tension value. When the deviation exceeds the preset dead zone threshold, a control command is generated based on the control algorithm, and the actuator is driven to change the belt tension by adjusting the center distance between the two pulleys driving the belt.

9. The automatic belt tensioning method based on vibration frequency analysis according to claim 8, characterized in that, The steps of performing spectral analysis on the vibration signal, extracting the fundamental frequency of the belt vibration, and calculating the real-time tension value of the belt based on the fundamental frequency and pre-stored belt parameters include: The vibration signal is preprocessed by windowing and detrending term removal; Perform a Fast Fourier Transform on the preprocessed signal to obtain the spectrum; Within the spectrum, candidate fundamental frequencies are identified within a preset effective frequency range, and the final fundamental frequency of vibration is confirmed by verifying the presence of harmonic components at their integer multiples. Using formula Calculate the real-time tension value; in, The linear density of the belt. For the effective vibration length, It is the fundamental frequency of vibration.

10. The automatic belt tensioning method based on vibration frequency analysis according to claim 8, characterized in that, In the step of changing belt tension by adjusting the center distance between the two pulleys of the drive belt, the drive actuator controls a servo motor to drive the ball screw pair, converting the rotational motion into linear motion, which in turn pushes the sliding plate of the carrying motor or flywheel to move along the linear guide rail to change the center distance.

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