Brake disc dynamic balance detection system based on laser Doppler vibration measurement

Abstract

The invention relates to the technical field of dynamic balance detection of rotating parts, and discloses a brake disc dynamic balance detection system based on laser Doppler vibration measurement, which comprises the following steps that: the system acquires a complete operation deformation vibration mode of a brake disc to be detected, and performs orthogonal projection on the complete operation deformation vibration mode to a pre-stored theoretical rigid body modal vector; according to the method, the dynamic balance of the flexible disc can be accurately tested by separating out pure rigid body vibration components and carrying out unbalance calculation, and meanwhile, the system verifies the matching degree of a model according to which the projection process is based online, so that the technical problem that the dynamic balance of the flexible disc cannot be separated due to the same frequency of structural modal vibration and unbalance vibration is solved, and the dynamic balance of the flexible disc can be accurately tested; and the online diagnosis mechanism can synchronously identify the model mismatch problem caused by the structural defect of the workpiece or the wrong clamping state in the testing process.

Description

TECHNICAL FIELD

[0001] The application relates to a brake disc dynamic balance detection system based on laser Doppler vibration measurement. BACKGROUND

[0002] Currently, dynamic balance testing of components is a basic quality control process. Mass imbalance on a rotating body will generate a synchronous vibration response with rotation speed. The size and angular position of the imbalance mass can be calculated reversely through measurement of the vibration amplitude and phase, and correction can be made accordingly. With the requirements of lightweight and high performance of the automobile industry, the structure of disc-shaped rotating parts such as brake discs tends to be thin-walled and complex, which makes it impossible to accurately describe the real physical behavior of the parts under dynamic working conditions by regarding the parts as quasi-rigid bodies. When such a brake disc with flexible characteristics rotates at high speed on a balancing machine, in addition to the centrifugal force excitation caused by mass imbalance, other factors such as aerodynamic load will also excite the structural bending or torsional modes of the part itself, generating a synchronous structural modal vibration with rotation speed. This vibration and the rigid body vibration caused by mass imbalance are superimposed on each other in the signal collected by the sensor, forming a composite vibration mode.

[0003] The conventional technical idea is usually to seek more advanced signal filtering algorithms. However, since the quality imbalance vibration and the structural modal vibration are same-frequency signals at the rotating frequency, they are not noise and signals in the traditional sense, and therefore it is difficult to separate them based on the frequency domain characteristics. In addition to the above fundamental defects in the dynamic balance calculation model, the detection methods for other physical properties of the brake disc also have limitations in the measurement principle and control logic level, and cannot solve the key dynamic performance evaluation problem. For example, the Chinese utility model patent with the publication number CN210625579U discloses a kind of airplane brake dynamic disc polishing detection device, which detects the disc surface reflection area by a photosensitive sensor array to evaluate whether the polishing amount reaches 30% to 50% required by the manual. However, this scheme is essentially a static geometric quantity evaluation based on surface optical characteristics, which focuses on the completion of grinding work, rather than the dynamic performance of the brake disc core. This method completely ignores the complex vibration form of the component under rotating conditions, and cannot effectively identify the quality imbalance and structural modal coupled vibration affecting the vehicle NVH (Noise, Vibration and Harshness) performance. The detection logic starting from the apparent characteristics does not touch the fundamental technical problem that the precision is limited due to the inseparability of the same frequency vibration sources in the dynamic balance test of the flexible disc. This phenomenon causes a fundamental technical problem, that is, the classical dynamic balance calculation algorithm, whose physical model is based on the rigid body assumption, will include the structural modal vibration component in the response caused by the quality imbalance when receiving a composite signal, and calculate an imbalance vector deviating from the true mass distribution. The accuracy of the correction result based on this vector will be affected.

[0004] Specifically, the existing technology mainly has the following deficiencies: 1. Mismatch of calculation model. The rigid body theory premise relied on by the existing dynamic balance calculation method does not match the actual dynamic characteristics of modern flexible brake discs, causing applicability problems of the calculation model; 2. Difficulty in separating same-frequency vibration sources. The rigid body vibration caused by mass imbalance and the structural modal vibration caused by other factors are same-frequency signals at the measurement end, which are difficult to distinguish using conventional signal processing methods; 3. Accuracy of balance result is limited. The vibration signal input to the calculation model contains vibration components generated by non-mass imbalance factors, resulting in distortion of the calculated imbalance vector and limiting the precision of the balance correction work. Therefore, how to identify and separate the vibration component generated only by mass imbalance from a composite vibration signal containing multiple physical sources to obtain accurate dynamic balance test results has become a technical problem to be solved by the present invention. SUMMARY

[0005] The application provides a brake disc dynamic balance detection system based on laser Doppler vibration measurement, which mainly aims to solve the problem that in the prior art, the physical model for dynamic balance calculation cannot match the actual dynamic characteristics of the measured member due to the inability to effectively distinguish between mass imbalance vibration and structural modal vibration of the same frequency, thereby affecting the accuracy of the test results.

[0006] To achieve the above-mentioned purpose, the application provides a brake disc dynamic balance detection system based on laser Doppler vibration measurement, which comprises: a rotating drive module configured to clamp and drive the measured brake disc to rotate at a preset rotating speed; a vibration signal acquisition module configured to: when the measured brake disc generates composite vibration including rigid body vibration and structural modal vibration due to rotation, acquire vibration signals of multiple preset measurement points on the surface of the measured brake disc by using a laser Doppler vibration measurement method, and construct a measured running deformation mode vector according to the acquired vibration signals and a phase reference. a controller, which internally stores a modal base library matched with the model of the measured brake disc, and at least contains a theoretical rigid body modal vector, and is configured to: orthogonally project the measured running deformation mode vector onto the theoretical rigid body modal vector stored in the modal base library, thereby obtaining a purified rigid body vibration vector; and calculate a mass imbalance vector of the measured brake disc only by taking the purified rigid body vibration vector as input; and calculate a residual vector between the measured running deformation mode vector and the modal base library, and when the norm of the residual vector exceeds a preset threshold, generate and output a diagnostic alarm signal indicating model mismatch.

[0007] Preferably, the controller is configured to obtain the purified rigid body vibration vector by performing the following calculation formula: wherein, is the purified rigid body vibration vector, is the measured running deformation mode vector, is the theoretical rigid body modal vector, and · is a vector dot product operation, is the norm of the theoretical rigid body modal vector.

[0008] Preferably, the specific operation of the vibration signal acquisition module configured to construct the measured running deformation mode vector comprises: acquiring vibration velocity time domain signals of each of the multiple preset measurement points; the controller performs Fourier transform on each vibration velocity time domain signal according to the phase reference to extract complex amplitudes at the rotating frequency synchronized with the preset rotating speed; and the controller combines the complex amplitudes of all measurement points at the rotating frequency according to a preset spatial order, thereby constructing the measured running deformation mode vector.

[0009] Preferably, the modal basis library further comprises a plurality of theoretical flexible modal vectors corresponding to the structural characteristics of the brake disc to be measured; the theoretical rigid modal vectors and the theoretical flexible modal vectors are both obtained and stored in advance by performing finite element analysis on a digital model of the brake disc to be measured or by performing experimental modal testing on a physical brake disc.

[0010] Preferably, the diagnostic alarm signal indicates that the physical cause leading to the model mismatch is one of the following three: an error exists in the clamping state of the brake disc to be measured, the model of the brake disc to be measured does not match the modal basis library currently loaded by the controller, or the brake disc to be measured itself has a structural defect.

[0011] Preferably, the controller is configured to calculate the mass imbalance vector based on the influence coefficient method and based on the purified rigid vibration vector, the mass imbalance vector comprising information about the magnitude and angular position of the imbalance.

[0012] Preferably, the specific operation of the controller to calculate the residual vector comprises: projecting the measured operating deformation mode shape vector onto the theoretical rigid modal vectors and all the theoretical flexible modal vectors stored in the modal basis library respectively to obtain a set of modal participation coefficients; using the set of modal participation coefficients and all the theoretical modal vectors in the modal basis library to linearly superimpose and reconstruct a theoretical operating deformation mode shape vector; and calculating the vector difference between the measured operating deformation mode shape vector and the theoretical operating deformation mode shape vector to obtain the residual vector.

[0013] Preferably, the controller is further configured to: receive an input brake disc model information before the dynamic balance detection starts; and select and load the modal basis library that is unique to the model of the brake disc to be measured from the stored modal basis libraries of a plurality of brake discs of different models according to the model information.

[0014] Preferably, the controller is further configured to: when the diagnostic alarm signal is not generated, output the final mass imbalance vector; and when the diagnostic alarm signal is generated, prohibit the output of the mass imbalance vector and output the diagnostic alarm signal to an external system.

[0015] Preferably, the diagnostic alarm signal output by the controller further comprises the norm value of the residual vector and the value of the preset threshold, which are used to quantitatively evaluate the degree of model mismatch.

[0016] Compared with the prior art, the present application has the following beneficial effects: 1. By acquiring the complete operational deformation vibration mode of the brake disc under test online and mathematically projecting it onto the pre-stored rigid body modal vector corresponding to the physical properties of the test component, a novel information processing method for dynamic balancing testing is established. This method directly locks the basis for calculating the unbalance quantity onto the component in the vibration information that uniquely matches the rigid body motion pattern. In principle, this process separates the basis for calculating the balance value from the deformation vibration component of the brake disc caused by structural flexibility or aerodynamic loads that is not directly related to the mass distribution. Thus, the calculation distortion problem introduced by model mismatch in traditional methods no longer becomes an interference factor that needs to be preprocessed within the logical framework of this method.

[0017] 2. While separating the rigid body vibration components using a projection method, a pre-stored complete modal basis library, including both rigid and flexible modes, is used to reconstruct the measured original vibration deformation modes, and the residual between the measured and reconstructed modes is calculated. The introduction of this residual establishes a real-time self-verification mechanism for model matching for each measurement, ensuring that each output of unbalance is accompanied by a synchronous confirmation of the validity of its calculation premises. This integrated approach of purification and premise verification within a single measurement process ensures that test results are accurate even with unavoidable clamping variations or other issues encountered on the production line. The reliability of product individual tolerances, and the calculation and monitoring of residuals, extend the measurement process of dynamic balancing test from a single objective to a process that also has the ability to monitor the structural state of the tested part online. When the residual exceeds the preset threshold, the system indicates not only the deviation of the balance test conditions, but also the presence of abnormal vibration components in the measured vibration that cannot be explained by the normal physical model. This abnormality directly points to possible crack damage or structural defects such as material inhomogeneity in the brake disc itself, which elevates the vibration measurement data, which originally only served to determine the mass balance, to the function of preliminary screening of structural integrity. Attached Figure Description

[0018] Fig. 1 This is a flowchart of the dual-path processing of unbalanced solution and model diagnosis in this invention; Fig. 2 This is a graph showing the variation of the residual vector norm in the model mismatch diagnosis of this invention. Fig. 3 This is a block diagram showing the hardware structure and core signal interaction of the system of the present invention. Detailed Implementation

[0019] In order to make the objects, technical solutions and advantages of the present application clearer, the present application will be further described in detail below. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments; based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0020] The disclosed brake disc dynamic balance detection system based on laser Doppler vibration measurement comprises a rotating drive module, a vibration signal acquisition module and a controller. When performing dynamic balance detection, the rotating drive module is used to clamp the brake disc to be measured and provide a stable and accurate rotating speed for the brake disc to be measured, the vibration signal acquisition module is used to non-contactly acquire complete vibration shape information of the brake disc in a rotating state, and the vibration data is transmitted to the controller. The controller analyzes and separates the composite signal containing multiple vibration sources according to the data processing method in the controller, finally outputs a physical quantity related only to mass imbalance, and simultaneously checks the matching degree of the model relied on by the analysis process. In the quality detection station of the automobile brake disc production line, due to the thin-walled structure of the brake disc, when rotating at high speed, not only the centrifugal force caused by the mass imbalance of the brake disc will cause the rigid body vibration of the disc body, but also the disc body will be excited to vibrate in the structural bending or torsional mode due to the factors such as main shaft runout or pneumatic load. The structural modal vibration and the rigid body vibration caused by the imbalance are the same frequency signals in the rotating frequency, and the conventional filtering method is difficult to separate the two, which leads to the error of the structural modal vibration to the imbalance response in the subsequent balance calculation algorithm, thereby causing the deviation of the calculation result. In order to solve this problem, the controller of the present application is configured to execute a data processing procedure based on modal projection, and the procedure processes the collected vibration signal as a spatial mode corresponding to the physical shape of the brake disc.

[0021] The specific implementation of the data processing procedure is as follows. Before detection, the controller loads a modal base library matched with the brake disc to be measured from the internal memory according to the external input brake disc model information. The modal base library is a digital model of the brake disc, which is pre-established by finite element analysis or experimental modal test, and the data structure of the modal base library is a matrix, which at least contains a theoretical rigid body modal vector , which describes the theoretical vibration shape of the brake disc when the brake disc is purely rigidly inclined due to mass imbalance. In addition, the modal base library can also contain one or more theoretical flexible modal vectors , to describe the main structure of the brake disc vibration mode; then, the rotating drive module drives the brake disc to be tested to a preset rotating speed, for example, 900 RPM; after the rotating speed is stable, the vibration signal acquisition module starts, and the scanning laser Doppler vibration meter in the module scans the surface of the brake disc at M preset measuring points and collects the vibration speed signal of each measuring point in the time domain. At the same time, a phase reference sensor synchronized with the main shaft of the rotating drive module provides a real-time rotating angle reference signal; the controller receives the M vibration speed time domain signals and the phase reference signal, performs Fourier transform on the time domain signal of each measuring point, and extracts the complex amplitude at the rotating frequency synchronized with the preset rotating speed. The complex amplitude contains the vibration amplitude and phase of the point; finally, the controller combines the complex amplitudes of all M measuring points at the rotating frequency according to the preset spatial order, thereby constructing an M-dimensional complex vector, which is the measured running deformation mode vector . It is necessary to point out that before the controller constructs the measured running deformation mode vector according to the collected M vibration speed time domain signals, a signal quality pre-checking procedure is also performed. The procedure first calculates the signal-to-noise ratio of each time domain signal at the rotating frequency, that is, the ratio of the narrow-band energy centered on the rotating frequency to the average noise energy in the adjacent frequency band, and confirms that the signal-to-noise ratio is not less than a preset signal-to-noise ratio threshold, for example, 20 dB. At the same time, the procedure also performs full-spectrum analysis on the signal to extract the amplitude at the rotating frequency and the amplitude at twice the frequency of the rotating frequency , and confirms that the amplitude of the rotating frequency is at least one order of magnitude higher than the amplitude of the rotating frequency and all other harmonic or noise peaks. Only when all M signals pass the above signal-to-noise ratio and main frequency purity check, the controller calls these signals for subsequent mode vector construction and modal projection calculation. If any signal fails the check, the system will output a prompt indicating that there is excessive synchronous interference or signal acquisition link abnormality at the current rotating speed, and pause the subsequent calculation.

[0022] In addition, in order to ensure the long-term stability and data effectiveness of the entire measurement chain, the system is configured to automatically perform a measurement system state self-calibration procedure once before starting each batch of production tasks or after accumulating running for more than a preset time, for example, 4 hours. In the procedure, the rotating drive module does not install any brake disc to be tested, and the vibration signal acquisition module performs a vibration measurement on the surface of the clamped tooling in a stationary state. The controller collects the background vibration signal at this moment and calculates the vibration speed root mean square value in the entire effective frequency band ; then, the controller compares the real-time measured a value of the device background noise baseline representing the electronic noise inherent to the measuring chain and the environmental background vibration, calibrated and stored when the system is first installed and commissioned comparing the value of the device background noise baseline with the value of the measured background vibration if the value of the measured background vibration does not exceed 1.2 times the value of the device background noise baseline, it is determined that the current measuring system is in a normal state and the subsequent dynamic balancing detection is permitted to start, otherwise, if the value of the measured background vibration exceeds the limit value the system prohibits the execution of the dynamic balancing detection task and outputs a maintenance instruction to an external system indicating that the measuring device needs to be checked or the environmental vibration is excessive; then, the controller performs the core separation operation, i.e. orthogonally projects the measured running deformation mode vector onto the theoretical rigid body modal vector stored in the modal base library previously loaded, thereby obtaining a purified rigid body vibration vector The projection operation is completed by performing the following calculation formula: wherein is the purified rigid body vibration vector, is the measured running deformation mode vector, is the theoretical rigid body modal vector, and · is the vector dot product operation, is the norm of the theoretical rigid body modal vector; the projection operation separates the component in the spatial form consistent with the pure rigid body imbalance vibration form from the measured running deformation mode vector, and all structural flexible deformation vibration components orthogonal to the rigid body modal in the spatial form are filtered out; the controller calls the influence coefficient method and other dynamic balancing calculation algorithms with the purified rigid body vibration vector as the input, and calculates the mass imbalance vector of the brake disc to be measured, which contains the size and angular position information of the correction mass.

[0023] It should be noted that the effectiveness of the above processing flow is based on the premise that the pre-stored theoretical modal base library can accurately describe the actual physical characteristics of the brake disc to be measured; in the production process, the manufacturing tolerance of the brake disc individual, the variation of the clamping state, or the structural defects such as cracks in the disc body, may cause a mismatch between the theoretical model and the actual physical behavior; to cope with this situation, the controller is also configured to perform an online verification mechanism of the model matching degree while completing the projection separation; the specific operation of the mechanism is that the controller calculates the residual vector between the measured running deformation mode vector and the modal base library; in a specific embodiment, the calculation includes projecting the measured running deformation mode vector , respectively, to the theoretical rigid modal vector and all the theoretical flexible modal vectors stored in the modal base library, a set of modal participation coefficients is obtained, and then the set of coefficients and all the theoretical modal vectors in the modal base library are used to linearly superimpose and reconstruct a theoretical running deformation mode vector, and the vector difference between the measured running deformation mode vector and the theoretical running deformation mode vector is calculated to obtain a residual vector; then, the controller calculates the norm of the residual vector and compares it with a preset threshold; if the norm does not exceed the threshold, it indicates that the current model matching degree is within the allowable range, and the current detection is valid, and the controller outputs the finally calculated mass imbalance vector; otherwise, if the norm exceeds the threshold, the controller determines that the model mismatch occurs, at this time, the possible inaccurate mass imbalance vector is not output, and a diagnostic alarm signal indicating the model mismatch is generated, which is used to indicate process abnormalities such as clamping errors, inconsistent workpiece models or structural defects of the workpiece.

[0024] Embodiment 1: In a brake disc automatic production line for high-performance electric vehicles, the dynamic balance detection system of the application is deployed in the quality control link; a large-diameter thin-walled brake disc produced by the production line has a large structural flexibility, and the balance result repeatability is poor in the traditional dynamic balance test, and some of the balanced workpieces still have shaking problems in the subsequent vehicle noise, vibration and sound roughness, i.e. NVH test, resulting in a production bottleneck; when one of the brake discs to be tested is sent into the detection system of the application by the automatic tooling and is clamped, the system controller loads the corresponding modal base library according to the received workpiece model, and the rotating drive module drives the brake disc to a preset speed; after the speed stabilizes, the system constructs a measured running deformation mode vector containing rigid vibration and structural modal vibration through the vibration signal acquisition module ; the controller performs two core data processing operations in parallel, one of which is to orthogonally project to the theoretical rigid modal vector , to obtain a purified rigid vibration vector , and based on this, an initial mass imbalance vector is calculated; the other is to calculate the residual vector between and the entire modal base library, and to calculate its norm; in this specific measurement, the residual vector norm value calculated by the controller exceeds the preset threshold, and the system determines that the theoretical model on which the current measurement is based and the actual vibration behavior of the workpiece are mismatched, therefore, the system executes the preset response procedure, i.e. prohibits output of the initial mass imbalance vector, and sends a diagnostic alarm signal indicating model mismatch to the central control system of the production line.

[0025] The line maintenance personnel receives the alarm signal, checks the automatic clamping mechanism of the station, and finds that a positioning pin is worn out, causing a slight tilt in the clamping posture of the brake disc to be tested. This tilt changes the dynamic boundary conditions when the disc rotates, causing the true vibration pattern to deviate from the theoretical model. This deviation is captured by the change in the norm of the residual vector. After replacing the positioning pin and re-clamping and testing the brake disc, the system performs a complete measurement and data processing process again. This time, the calculated norm of the residual vector is within the preset threshold, and the system determines that the model matching is effective. Based on this, the system outputs the calculated mass imbalance vector based on the second measurement as the final effective result. After correcting the imbalance of the brake disc, it successfully passes the subsequent NVH test. This process shows that combining mass imbalance calculation with online model matching degree verification makes dynamic balancing detection no longer a standalone numerical measurement process, but a process diagnostic link that can monitor the effectiveness of the measurement precondition in real time. The system verifies each measurement behavior, providing a precondition confirmation for the physical meaning of each imbalance correction value output.

[0026] Example 2: To quantitatively verify the effectiveness of the identification of the mass imbalance vector in the presence of structural modal vibration interference at the same frequency, a comparative verification test is constructed. The test is conducted on a standard dynamic balancing test platform, which consists of a servo motor driving system with a rotational speed control accuracy of ±1 RPM, a high-repeatability clamping tool, and a vibration signal acquisition system composed of a scanning laser Doppler vibration meter and a synchronous acquisition controller. The vibration speed measurement resolution of the vibration meter is 0.1 µm / s. The test object is a known thin-walled brake disc that is prone to excite a first-order umbrella-shaped structural modal at a specific speed. Before the test, the brake disc is precisely dynamically balanced to make its initial imbalance less than 1 g·cm. Then, a 5.0 g test weight is installed on the specified position (radius 120 mm, angle ) of the disc to apply a mass imbalance vector to be tested. To simulate structural modal vibration interference, a micro piezoelectric ceramic sheet is attached to the non-measurement area of the brake disc and driven by a function generator that is phase-locked with the main shaft rotation encoder signal to produce a continuous excitation force at the same frequency (1x) as the main shaft rotation frequency. The amplitude and phase of the excitation force are adjusted to be sufficient to excite a first-order umbrella-shaped structural modal vibration, and the amplitude of the vibration at the measurement point is in the same order of magnitude as the imbalance vibration amplitude produced by the aforementioned 5.0 g test weight.

[0027] ​Two treatment groups are set in the test, namely a control group and a test group; the control group adopts a conventional dynamic balance test method, which only collects the vibration signal at the bearing seat supported by the tool shaft, and performs Fourier transform on the signal to extract the complex amplitude at the rotation frequency for imbalance calculation; the test group adopts the complete technical solution of the application, that is, the vibration signals of multiple measuring points on the disc surface are collected to construct the measured running deformation mode vector , and subsequent modal orthogonal projection separation and model matching degree online verification are performed; the brake disc in the above state with test weight and under structural excitation is tested at the same speed of 900 RPM, and the mass imbalance vector results calculated by the two methods are recorded in Table 1; referring to Table 1, the table presents the measurement results of the known imbalance amount by the two methods.

[0028] Table 1: Comparison table of measurement results of known imbalance amount by different test methods.

[0029]

[0030] The data in Table 1 shows that in the presence of the same frequency structural modal vibration interference, the measurement results of the control group have large deviations in the amplitude and phase of the imbalance amount, and the amplitude measurement error reaches 58.3%, which shows that the conventional single-point measurement method cannot distinguish the two sources of the same frequency vibration, and incorrectly counts the structural modal vibration into the imbalance response; in contrast, the measurement results of the test group are highly consistent with the known true imbalance amount, and the amplitude measurement error is only 2.8%, which benefits from the modal orthogonal projection processing method used, which separates the structural modal vibration component that does not conform to the rigid body motion mode in space by analyzing the spatial form characteristics of the vibration, thereby obtaining the vibration information caused only by the mass imbalance; the test result confirms that the technical solution of the application can identify and separate the vibration component caused only by the mass imbalance in a composite vibration signal containing multiple physical sources, thereby obtaining accurate dynamic balance test results; in order to further verify the necessity and superiority of the modal orthogonal projection processing method used in the application compared with other conventional signal processing methods in the art which are also based on multi-point measurement but have different technical paths, a following comparative example is added.

[0031] Comparative Example 1: To verify the superiority of the technical solution of the present application compared with a conventional method which is technically more complex, the comparative example constructs an experimental environment which is completely identical with Example 2 in terms of hardware configuration, test object, known unbalance amount application mode and structural modal excitation mode. The only difference between the comparative example and the test group of Example 2 is that the data processing algorithm executed by the controller is different: the comparative example uses a multi-point vibration signal space vector average method to replace the modal orthogonal projection separation step in the technical solution of the present application; the specific processing process of the multi-point vibration signal space vector average method is as follows: first, the vibration signals of M preset measurement points on the brake disc surface are collected, and the Fourier transform is performed on each signal to extract the complex amplitude at the rotation frequency; then, the method performs vector summation on the complex amplitudes obtained by all M measurement points in the complex plane, and calculates the arithmetic mean value to obtain a single space average vibration vector; finally, the method takes the space average vibration vector as input, calls the influence coefficient method which is completely identical with Example 2, to calculate the mass unbalance vector. Under the same 900 RPM speed, the same brake disc with a 5.0 g test weight and subjected to the same frequency structural excitation is tested, and the mass unbalance vector calculated by the method is recorded in Table 2.

[0032] Table 2: Comparison table of measurement results of known unbalance amount by the comparative example and Example 2 of the present application.

[0033]

[0034] The test results of Comparative Example 1 show that under the condition of the presence of the same frequency structural modal vibration interference, the measurement results obtained by the multi-point vibration signal space vector average method have deviations in amplitude and phase, and the amplitude measurement error reaches 34.2%. The results confirm that although the conventional method also uses the vibration information of multiple points on the disc surface, the space vector average processing method cannot effectively distinguish the rigid body vibration with different spatial forms from the structural modal vibration in terms of physical principle, and the calculated space average vibration vector is still a composite quantity seriously contaminated by the structural modal vibration, so it cannot obtain accurate dynamic balancing test results. This result indirectly proves that the technical path of the present application based on the physical model (theoretical rigid body modal vector) for orthogonal projection to separate the vibration components has technical advantages and necessity for solving the same frequency vibration interference problem of flexible disc parts.

[0035] Example 3: This example combines Figs. 1 to 3 the description of the brake disc dynamic balancing detection system based on laser Doppler vibration measurement, as Fig. 1As shown, it shows the complete information path from obtaining the original vibration to outputting the final result, a brake disc to be tested produces physical vibration when rotating, the vibration velocity time domain signal is obtained through the vibration signal acquisition link, and the mode shape vector is constructed accordingly, the mode shape vector is sent to two parallel processing paths, one path retrieves the theoretical modal vector from A1: modal base library, performs rigid body vibration separation operation on the input mode shape vector to obtain the purified rigid body vibration, and calculates the unbalance based on the purified rigid body vibration, and finally outputs the mass unbalance for the line control system / user to use, the other parallel path also retrieves the theoretical modal vector from A1: modal base library, performs model matching degree operation on the input mode shape vector to obtain the residual vector norm, and generates a diagnosis result based on the norm, and outputs a diagnosis alarm signal to the line control system / user when the model is mismatched.

[0036] As shown in Fig. 2 The horizontal coordinate of the graph is the test sequence number, and the vertical coordinate is the residual vector norm. A dashed line in the graph represents a preset threshold value as a judgment basis, which is constant at 0.20. Another point-splined line with data points represents the actual value of the residual vector norm calculated in the previous tests. The value is lower than the preset threshold value in most test sequence numbers, but a peak value with a maximum value exceeding 0.30 appears near test sequence number 24. This clearly shows that when the system detects abnormalities such as workpiece clamping errors, the residual vector norm will suddenly change and exceed the preset threshold value, thereby triggering the working state of the diagnosis alarm signal.

[0037] As shown in Fig. 3 The core is a rotating drive module that drives the brake disc to be tested. The module includes a servo motor and a precision spindle, and fixes the brake disc through a clamping tool. A laser Doppler vibrometer projects a laser vibration beam to a preset measurement point on the surface of the brake disc and performs scanning measurement. The collected vibration signal is sent to the controller through data transmission. A phase reference sensor provides a rotation reference for the system through phase detection, and sends this information to the controller through a phase synchronization link. The controller integrates modal base library storage, data processing unit and unbalance calculation function, and sends control signals to the rotating drive module according to the processing result.

[0038] Embodiment 4: Before the dynamic balance detection system of the application is put into a batch detection task of a new type brake disc, a standardized offline calibration procedure needs to be performed to establish a modal base library matched with the workpiece of this type and set a residual norm threshold value for model mismatch diagnosis. This procedure aims to ensure that the accuracy of subsequent online detection and the reliability of the diagnosis function are based on an experimentally verified and reproducible engineering reference. The initial step of this procedure is to construct a preliminary modal base library. For the new type brake disc, first, the theoretical rigid body modal vector is calculated through finite element analysis method and a plurality of low-order theoretical flexible modal vectors ; subsequently, to verify and correct the performance of the theoretical model under the actual clamping condition, a batch (for example, 20 pieces) of the brake disc of this model confirmed to have no structural defects and the size within the tolerance center range is selected as the reference sample, each reference sample is installed one by one on the actual tooling of the dynamic balance detection system, and the experimental modal test is carried out through the small force value hammering or acoustic excitation and the like, combined with the vibration signal acquisition module, to obtain the actual modal parameters under the real constraint boundary condition; the controller performs correlation analysis on the measured modal shape and the theoretical modal shape obtained by the finite element analysis, if the correlation degree is higher than the preset standard, the effectiveness of the theoretical model is confirmed, if there is a slight deviation caused by clamping stress and the like, the theoretical modal vector is appropriately corrected according to the measured data, so as to form a final modal base library verified and matched with the actual working condition and stored in the controller.

[0039] After the modal base library is established, the next step of the procedure is to set a quantitative criterion for model mismatch diagnosis, that is, the norm threshold of the residual vector; the operator repeatedly carries out normal clamping and unloading on the 20 reference samples on the test tooling, and performs a standard dynamic balance test process on each normal clamping state, for example, repeatedly tests each sample 5 times, and a total of 100 groups of measured running deformation modal vectors under normal working conditions are obtained ; for each of the 100 groups of data, the controller calculates the norm of the residual vector according to the final modal base library stored; after all the tests are completed, the controller performs statistical analysis on the 100 residual norm values, and calculates the mean value and the standard deviation ; in order to ensure the detection sensitivity of the abnormal state and avoid false alarms of normal production fluctuations, the preset threshold of the residual norm is set according to the statistical process control theory, which is the sum of the mean value and several times of the standard deviation, for example, the threshold is determined as ; at this time, the modal base library establishment and diagnosis threshold setting for the new type of brake disc are completed, and the system can enter the online automatic detection mode; this calibration procedure changes the determination of the diagnosis threshold from a fuzzy setting depending on experience to a quantitative parameter with clear physical meaning and statistical basis obtained after statistical learning of the batch of workpieces and process state.

[0040] Embodiment 5: The influence coefficient for balance solving in the dynamic balance detection system controller of the application is determined by the following calibration procedure: a reference brake disc that has been precisely balanced is selected, installed on the test station and rotated at a preset speed, the system collects its vibration signals and calculates to obtain the initial purified rigid body vibration vector ; subsequently, the influence coefficient of the reference brake disc In the angular position, the test mass of known mass is added, and the system is rotated again at the same speed. The new purified rigid body vibration vector is calculated The controller calculates the vector difference between the two measurements of the purified rigid body vibration vector The vibration response change caused by the test mass is obtained, and the ratio of the vibration response change to the applied test mass vector is calculated as the influence coefficient of the test system at this speed, which is stored in the controller and used as the basis for subsequent imbalance calculation.

[0041] To cope with the modal drift of the brake disc structure caused by environmental temperature changes, the dynamic balance detection system of the application also configures a modal base library adaptive updating procedure; the system workstation integrates a temperature sensor to monitor the environmental temperature. When the monitoring temperature deviates from the reference temperature at the initial calibration by more than a preset range, such as ±10 When the monitoring temperature deviates from the reference temperature at the initial calibration by more than a preset range, such as ±10

[0042] Before applying the dynamic balance detection system of the application to batch detection of a new model brake disc, a set of pre-test parameter optimization procedures need to be performed to determine the specific configuration of the preset speed and multiple preset measurement points; the purpose of this procedure is to determine a set of engineering parameters that can obtain effective vibration mode information with the highest signal-to-noise ratio in the shortest test time for subsequent online detection; the procedure first determines the test speed, the steps are as follows: select a reference sample, after clamping on the test station, the rotating drive module drives it to slowly increase from a lower speed (such as 100 RPM) to a higher speed (such as 2000 RPM), during this speed-up process, the vibration signal acquisition module continuously monitors the vibration response of specific points on the brake disc surface, and the controller synchronously draws the vibration frequency vs. speed relationship map; by analyzing the map, the structural modal resonance regions of the brake disc can be identified, i.e. the speed range where the vibration amplitude peaks with speed; to avoid exciting excessive structural modal vibrations during conventional testing and thereby interfering with the measurement of unbalanced vibrations, the preset speed is selected at a speed between two adjacent main resonance regions, which can produce sufficient amplitude of unbalanced response signal and is far away from each order resonance peak.

[0043] After the test speed is determined, the procedure continues to optimize the number and spatial distribution of the measurement points for the laser Doppler vibrometry: still using the aforementioned reference specimen, at the determined test speed, it is driven in rotation and an artificial excitation of a known modal is applied, so that it simultaneously generates a rigid body modal vibration and a low order flexible modal vibration; the system first performs a scan with an ultra-high density (e.g. 500) of measurement points, far exceeding the conventional number, to construct a high-fidelity reference operating deformation mode shape vector; subsequently, the controller performs an iterative down-sampling analysis, i.e. from the high-density data, data subsets are extracted with different numbers (e.g. from 100 to 20) and different spatial distribution patterns (e.g. along 2, 4 or 8 diameters), and a low-density measured operating deformation mode shape vector is constructed for each data subset; by calculating the modal confidence criterion correlation between each low-density mode shape vector and the aforementioned high-fidelity reference mode shape vector, the ability of the measurement point configuration to reproduce the key modes (rigid body and low order flexible) is evaluated; finally, the number and spatial distribution of measurement points that are able to reproduce all key modes with a correlation higher than a pre-set threshold (e.g. 0.98) are determined, i.e. the multiple pre-set measurement points for the batch detection of the model brake disc are determined.

[0044] It is apparent for a person skilled in the art that the present application is not limited to the details of the above-described exemplary embodiments, but can be implemented in other concrete forms without departing from the spirit or essential characteristics of the present application.

[0045] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application but not to limit the present application, and although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced equivalently without departing from the spirit and scope of the present application.

Claims

1. A brake disc dynamic balance detection system based on laser Doppler vibration measurement, characterized in that, The system includes: A rotary drive module is configured to clamp and drive the brake disc under test to rotate at a preset speed. A vibration signal acquisition module is configured to: when the brake disc under test generates a composite vibration including rigid body vibration and structural modal vibration due to rotation, use laser Doppler vibration measurement method to acquire vibration signals at multiple preset measurement points on its surface, and construct a measured operating deformation mode vector based on the acquired vibration signals and a phase reference. A controller internally stores a modal basis library that matches the model of the brake disc under test and contains at least one theoretical rigid body modal vector. The controller is configured to: orthogonally project the measured operating deformation mode vector onto the theoretical rigid body modal vector stored in the modal basis library to obtain a cleaned rigid body vibration vector; calculate a mass imbalance vector of the brake disc under test using only the cleaned rigid body vibration vector as input; and calculate the residual vector between the measured operating deformation mode vector and the modal basis library. When the norm of the residual vector exceeds a preset threshold, a diagnostic alarm signal indicating model mismatch is generated and output.

2. The brake disc dynamic balance detection system based on laser Doppler vibration measurement according to claim 1, characterized in that, The controller is configured to obtain the vibration vector of the purified rigid body by performing the following calculation: in, To purify the rigid body vibration vector, The measured deformation mode vector during operation. For theoretical rigid body modal vectors, For vector dot product operation, Let be the norm of the theoretical rigid body modal vector.

3. The brake disc dynamic balance detection system based on laser Doppler vibration measurement according to claim 1, characterized in that, The vibration signal acquisition module is configured to construct the measured deformation mode vector. The specific operations include: acquiring the vibration velocity time-domain signals of multiple preset measurement points; the controller performs a Fourier transform on each vibration velocity time-domain signal based on the phase reference; and the controller combines the complex amplitudes of all measurement points at the rotational frequency in a preset spatial order.

4. The brake disc dynamic balance detection system based on laser Doppler vibration measurement according to claim 1, characterized in that, The modal base library also contains multiple theoretical flexible modal vectors corresponding to the structural characteristics of the brake disc under test; the theoretical rigid modal vectors and the theoretical flexible modal vectors are all obtained and stored in advance after finite element analysis of the digital model of the brake disc under test or after experimental modal testing of the physical brake disc.

5. The brake disc dynamic balance detection system based on laser Doppler vibration measurement according to claim 1, characterized in that, The diagnostic alarm signal indicates that the physical cause of the model mismatch is one of the following three: the clamping status of the brake disc under test is incorrect, the model of the brake disc under test does not match the modal base library currently loaded by the controller, or the brake disc under test itself has a structural defect.

6. The brake disc dynamic balance detection system based on laser Doppler vibration measurement according to claim 1, characterized in that, The controller is configured to calculate the mass imbalance vector based on the influence coefficient method and the vibration vector of the purified rigid body. The mass imbalance vector contains information on the magnitude and angular position of the imbalance.

7. The brake disc dynamic balance detection system based on laser Doppler vibration measurement according to claim 4, characterized in that, The controller is configured to perform the following operations to calculate the residual vector: project the measured operating deformation mode shape vector onto the theoretical rigid body mode vector and all theoretical flexible mode vectors stored in the mode basis library to obtain a set of modal participation coefficients; reconstruct a theoretical operating deformation mode shape vector by linear superposition using the set of modal participation coefficients and all theoretical mode vectors in the mode basis library; and calculate the vector difference between the measured operating deformation mode shape vector and the theoretical operating deformation mode shape vector to obtain the residual vector.

8. The brake disc dynamic balance detection system based on laser Doppler vibration measurement according to claim 1, characterized in that, The controller is further configured to: receive an input brake disc model information before the dynamic balancing test begins; and, based on the model information, select and load the unique modal base library that matches the current brake disc model from a storage of multiple different brake disc model modal base libraries.

9. A brake disc dynamic balance detection system based on laser Doppler vibration measurement according to claim 1, characterized in that, The controller is further configured to output the final mass imbalance vector when no diagnostic alarm signal is generated; and to prohibit the output of the mass imbalance vector and output the diagnostic alarm signal to an external system when a diagnostic alarm signal is generated.

10. A brake disc dynamic balance detection system based on laser Doppler vibration measurement according to claim 1, characterized in that, The diagnostic alarm signal output by the controller also includes the norm value of the residual vector and the value of the preset threshold.

Images