Test method and test bench for evaluating brake noise of a friction brake

Abstract

The application discloses a test method and test bench for evaluating brake noise of a friction brake, comprising: carrying out brake noise test according to a set working condition, collecting brake torque, working speed and noise signal; obtaining speed-torque mean value characteristics and fluctuation characteristics based on the brake torque and the working speed, obtaining sound pressure level and noise growth rate based on the noise signal; and performing vibration noise performance evaluation based on the speed-torque mean value characteristics, the fluctuation characteristics, the sound pressure level and the noise growth rate. The application realizes collection of brake vibration noise related signals under different working conditions, and can also increase evaluation dimensions of vibration noise behavior based on vibration noise signals in test results, so as to fully reflect current noise performance and vibration stability characteristics of the brake.

Description

Technical Field

[0001] This invention belongs to the field of brake noise performance monitoring, evaluation and testing technology, and particularly relates to a test method and test bench for evaluating the braking noise of a friction brake. Background Technology

[0002] Friction brakes rely on the friction between the friction disc and the friction pad to provide braking force for vehicles and are widely used in the braking systems of vehicles and engineering machinery. However, friction vibration noise may be generated during the braking process, which not only causes noise pollution and affects passenger comfort, but also affects the working accuracy and service life of the equipment, reducing its reliability. Therefore, studying the generation mechanism and development law of brake noise using experimental methods has strong engineering value. Existing research methods on friction noise mainly include the following: 1. Mechanistic research based on small friction and wear testing machines. This method uses small samples with point contact, line contact, or surface contact to study the friction contact behavior under different materials or surface morphologies, revealing the generation mechanism of friction self-excited vibration and noise. 2. Using disc brakes to build test benches for testing. This method is more consistent with the actual structure of automotive brakes than small bench tests. At the same time, compared with actual vehicle tests, the sensor arrangement and operating parameter control are more flexible, and the collected signals have less interference. It is a commonly used research method. 3. Identify and evaluate braking noise data collected from actual vehicles. Based on relevant data collected during vehicle operation from the driver or brake position, identify the brake vibration and noise state and evaluate its performance in terms of braking noise. Several patents already describe related technologies for friction vibration and noise testing. Existing technologies disclose a friction noise research device using a friction and wear testing machine, enabling the characterization, measurement, and analysis of friction vibration and noise of components such as bearings. Existing technologies disclose a disc brake friction noise testing device incorporating braking inertia, using a soundproof chamber to isolate external noise. Existing technologies disclose methods for classifying and evaluating braking noise using machine learning and deep learning, quantifying the evaluation indicators of braking noise. These technical solutions enrich the research on braking noise of friction brakes, but also have some drawbacks. For example, due to structural differences, small test benches still cannot adequately reflect the friction vibration and noise behavior of brakes; simply using signals such as sound pressure level to evaluate noise behavior ignores the evaluation methods for the dynamic response characteristics of the brake. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention proposes a test method and test bench for evaluating the braking noise of a friction brake. This method enables the acquisition of vibration and noise-related signals of the brake under different operating conditions. Furthermore, based on the vibration and noise signals in the test results, it can add evaluation dimensions of vibration and noise behavior, fully reflecting the current noise performance and vibration stability characteristics of the brake.

[0004] To achieve the above objectives, the present invention provides a test method for evaluating the braking noise of a friction brake, comprising: conducting a braking noise test according to a set operating condition, and collecting braking torque, operating speed and noise signals;

[0005] Based on the braking torque and the operating speed, the mean characteristics and fluctuation characteristics of the speed torque are obtained, and the sound pressure level and noise growth rate are obtained based on the noise signal;

[0006] Vibration and noise performance is evaluated based on the mean characteristics of the rotational speed and torque, the fluctuation characteristics, the sound pressure level, and the noise growth rate.

[0007] According to the test method for evaluating the braking noise of a friction brake provided by the present invention, the method for obtaining the noise growth rate includes:

[0008] The frequency components of the noise signal are obtained by performing a fast Fourier transform on the noise signal, the frequency of the screaming noise is located, and it is determined as the center frequency of the filter.

[0009] The noise signal is processed using a zero-phase digital filtering method to obtain a noise signal containing only the howling frequency;

[0010] The filtered signal is divided into frames based on the sampling frequency and the length of the fitting interval. The sound pressure amplitude of each frame is then calculated to obtain the upper envelope signal.

[0011] The noise growth rate is obtained by exponentially fitting the rising edge of the upper envelope signal.

[0012] According to the test method for evaluating braking noise of a friction brake provided by the present invention, the method for obtaining the upper envelope signal is as follows:

[0013]

[0014] Where pa is the upper envelope signal, x i denoted as the audio signal amplitude, and N as the number of data points contained in each frame.

[0015] According to the test method for evaluating the braking noise of a friction brake provided by the present invention, the method for obtaining the noise growth rate is as follows:

[0016]

[0017] Where δ is the noise growth rate, t sp and t ep p represents the times at the start and end points of the fitted interval, respectively. e_sp and p e_ep These represent the effective sound pressure values ​​corresponding to the start and end points, respectively.

[0018] On the other hand, to achieve the above objectives, the present invention also provides a test bench for evaluating the braking noise of a friction brake, comprising: a power module, a hydraulic module, a control module, and a signal acquisition module; the power module is used for rigid connection via a shaft system and a flange, and is driven by a drive motor to rotate the friction disc of the friction brake;

[0019] The hydraulic module is used to provide oil circuits to the friction brake;

[0020] The control module is used to control the speed of the drive motor via a motor control console;

[0021] The signal acquisition module is used to acquire the braking torque and rotational speed information of the friction disc, as well as friction noise signals.

[0022] According to the test bench for evaluating braking noise of a friction brake provided by the present invention, the power module includes a drive motor, a reducer, a speed and torque sensor, and a friction brake. The motor control console is electrically connected to the drive motor, and the drive motor is mechanically connected to the reducer, the speed and torque sensor, and the friction brake in sequence. The friction brake includes a caliper assembly, a fixed base, friction pads, and a friction disc. The caliper assembly includes a caliper and a piston. The friction pads are placed inside the caliper. The caliper assembly is fixed to the fixed base with bolts. The friction disc is connected to the output end of the speed and torque sensor via a flange and is driven to rotate by the drive motor. When the caliper assembly provides normal pressure, friction is generated between the friction disc and the friction pads, providing braking torque.

[0023] According to the test bench for evaluating the braking noise of a friction brake provided by the present invention, the hydraulic module is mechanically connected to the friction brake in the power module. The hydraulic module includes an oil inlet circuit and an oil return circuit, and is controlled by a two-position three-way valve with the caliper piston cylinder. When the caliper piston cylinder is connected to the oil inlet circuit, the friction pad is pressurized, and the normal pressure of the friction brake is controlled by adjusting the displacement of the gear metering pump. When the caliper piston cylinder is connected to the oil return circuit, the friction brake is depressurized, and the braking torque disappears.

[0024] According to the test bench for evaluating braking noise of a friction brake provided by the present invention, the signal acquisition module is electrically connected to the speed and torque sensor and also electrically connected to the friction brake. The signal acquisition module includes a data acquisition control unit, a sound card, and a microphone. The data acquisition control unit is electrically connected to the speed and torque sensor, the microphone is electrically connected to the sound card, and the sound card is electrically connected to the data acquisition unit.

[0025] Technical advantages of this invention: This invention discloses a test method and test bench for evaluating braking noise of friction brakes. The test bench features flexible sensor arrangement and utilizes a planetary reducer, facilitating low-speed testing where braking noise is more likely to occur. Simultaneously, it quantifies the dynamic vibration stability characteristics of the brake using the noise growth rate, and measures the fitting effect through heuristic boundary conditions and root mean square error to obtain the optimal noise growth rate, thereby determining the vibration and noise tendency during braking in real time. By employing signals such as torque, speed, and noise, the evolution law of braking noise is comprehensively evaluated, enriching the research on the development history of braking noise. Attached Figure Description

[0026] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0027] Figure 1 This is a schematic flowchart of a test method for evaluating braking noise of a friction brake according to an embodiment of the present invention;

[0028] Figure 2 This is a flowchart illustrating the noise growth rate calculation method in an embodiment of the present invention;

[0029] Figure 3 This is a schematic diagram of a noise growth rate calculation example according to an embodiment of the present invention, wherein (a) is the noise signal before filtering, (b) is the noise signal after filtering, (c) is the frequency component of the signal before and after filtering, (d) is the range of start and end points, (e) is the noise growth rate fitting method, and (f) is the root mean square error set.

[0030] Figure 4 This is a schematic diagram of the structure of a test bench for evaluating the braking noise of a friction brake according to an embodiment of the present invention. Detailed Implementation

[0031] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0032] It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.

[0033] like Figure 1-3 As shown, this embodiment provides a test method for evaluating the braking noise of a friction brake, including: setting up a test bench;

[0034] Braking noise tests were conducted according to the set operating conditions, and sensors were used to collect data such as braking torque, operating speed, and noise signals.

[0035] Process the test data to obtain the average value and fluctuation of braking torque and operating speed;

[0036] This paper analyzes noise signals and presents a method for calculating the noise growth rate. The specific calculation process is as follows: Figure 2 As shown: ① The frequency components of the signal are obtained by performing a Fast Fourier Transform (FFT) on the original signal, the frequency of the screaming noise is located, and it is determined as the center frequency of the filter.

[0037] ② The original signal was processed using a zero-phase digital filtering method to obtain a noise signal containing only the howling frequency.

[0038] ③ The filtered signal is divided into frames according to the sampling frequency and the length of the fitting interval. The sound pressure amplitude of each frame is then calculated as the upper envelope signal for noise growth rate calculation.

[0039] ④ The noise growth rate is calculated by performing exponential fitting on the rising edge of the upper envelope signal. Since the choice of the start and end points of the fitting interval significantly affects the final fitting result, the optimal growth rate exponent is found by changing the start and end point positions within the heuristic boundary. Each pair of start and end points corresponds to a growth rate exponent, thus generating a growth rate dataset for a single acoustic emission phenomenon. In the final data evaluation, the root mean square error (RMSE) is used to measure the fitting effect, and the noise growth rate fitting result with the smallest error in the dataset is selected as the final noise growth rate calculation result.

[0040] The noise growth rate is obtained by exponentially fitting the rising edge of the upper envelope signal (i.e., the sound pressure signal). The selection of the start and end points is related to the definition of the start and end states of the noise development process. For example, in this embodiment, in Figure 3 In the noise signal shown in (a), the noise signal appears when the instantaneous sound pressure reaches 10% to 20% of the maximum sound pressure throughout the process, and the rapid development phase of the noise signal ends when the instantaneous sound pressure reaches 70% to 85% of the maximum sound pressure, at which point the noise sound pressure approaches stability. In addition, for multi-peak noise signals, the sound pressure of a certain peak can be selected as a reference value, and the proportion of the reference value corresponding to the start and end point range can be dynamically adjusted according to the background noise intensity and the sound pressure curve.

[0041] The root mean square error measures the error within the fitting interval, such as... Figure 3 As shown in (e), the root mean square error (RMSE) within the interval of 0.03s to 0.038s is used to evaluate the fitting result. Then, considering the error changes at different start and end points, the combination of start and end points with the smallest RMSE is selected as the noise growth rate of this noise signal segment. Figure 3As shown in (f).

[0042] The evaluation method is as follows: From the perspective of energy, the energy input from the drive shaft to the friction disc during braking can be dissipated through friction and vibration. When the average braking torque decreases, it indicates that the energy dissipated through friction is reduced and the energy dissipated through vibration is increased, which affects the braking efficiency of the brake. Therefore, the average value of the braking torque is used to assist in the evaluation of braking noise.

[0043] Braking noise is often accompanied by fluctuations in braking torque and speed, and these fluctuations are characterized by variance.

[0044]

[0045] In the formula, x i For signal value, Here, is the signal mean, and N is the total data volume. When the variances of braking torque and speed increase significantly, it indicates that high-intensity vibration noise is very likely generated during braking.

[0046] The noise growth rate is obtained by exponentially fitting the rising edge of the upper envelope signal (i.e., the sound pressure signal). The selection of the start and end points is related to the definition of the start and end states of the noise development process. For example, in this embodiment, it is considered that at... Figure 3 In the noise signal shown in (a), the noise signal appears when the instantaneous sound pressure reaches 10%–20% of the maximum sound pressure throughout the process, and the rapid development phase of the noise signal ends when the instantaneous sound pressure reaches 70%–85% of the maximum sound pressure, at which point the noise sound pressure approaches stability. In addition, for multi-peak noise signals, the sound pressure of a certain peak can be selected as a reference value, and the proportion of the reference value corresponding to the start and end point range can be dynamically adjusted according to the background noise intensity and sound pressure curve. The root mean square error measures the error within the fitting interval, such as… Figure 3 As shown in (e), the root mean square error (RMSE) within the interval of 0.03s to 0.038s is used to evaluate the fitting result. Then, considering the error changes at different start and end points, the combination of start and end points with the smallest RMSE is selected as the noise growth rate of this noise signal segment. Figure 3 As shown in (f).

[0047] Sound pressure level directly reflects the noise performance of the system. When a sound pressure level of 70dB or higher appears in the collected noise signal, it is considered that high-intensity noise has occurred during the braking process.

[0048] The above indicators all reflect the vibration and noise characteristics of the brake during the current braking process, measuring the current braking noise situation, but they do not have predictive power. The noise growth rate, on the other hand, reflects the development trend of the noise. When the noise growth rate increases, even if high-intensity braking noise is not currently detected, it indicates that the system has a high tendency for unstable vibration and there is a high probability that high-intensity braking noise will develop in a short period of time.

[0049] In the final evaluation of brake vibration and noise performance, the contribution of all the above parameters needs to be considered comprehensively. When any one of them is abnormal, it indicates that the vibration and noise performance has declined.

[0050] like Figure 3 The following is an example of how to calculate the noise growth rate:

[0051] ① By performing a Fast Fourier Transform (FFT) on the original signal to obtain the frequency components of the signal, it can be seen that the high-frequency noise in the original signal mainly comes from the component with frequency f1 = 2780Hz and its higher harmonics.

[0052] ② Using the fundamental frequency as the filter center frequency and the passband interval as the region with a width of Δf = 200Hz on both sides of the center frequency, a bandpass filter is designed using the Blackman window function. The filtering effect is as follows: Figure 3 As shown in (a), the filtered signal contains only frequency components around f1 = 2780Hz.

[0053] ③ The filtered signal is divided into frames of 0.2ms length, and the sound pressure amplitude of each frame is calculated. This is used as the upper envelope signal for noise growth rate calculation. The effective sound pressure is calculated as follows:

[0054]

[0055] In the formula, x i Where is the amplitude of the audio signal, and N is the number of data points per frame. After this processing step, a smoother upper envelope signal is obtained. The original signal before and after filtering, as well as the upper envelope signal, are shown below. Figure 3 As shown in (b) and 3(c).

[0056] ④ The maximum effective sound pressure p in a single acoustic emission phenomenon e_max The starting and ending points are defined as reference values, and their variation ranges are specified. The effective sound pressure ranges at the starting and ending points are respectively p e_max 0.1–0.2 times and 0.7–0.85 times, see Figure 3 (d)

[0057] ⑤ Each pair of start and end points corresponds to a growth rate index. For a specific fitting interval, the corresponding noise growth rate can be calculated by the following formula, and the calculation results are shown in [the table below]. Figure 3 (e):

[0058]

[0059] In the formula, t sp and t ep p represents the times at the start (SP) and end (EP) points of the fitted interval, respectively. e_sp and p e_ep These represent the effective sound pressure values ​​corresponding to the start and end points, respectively, which can then generate a set of growth rate indices for a single acoustic emission phenomenon.

[0060] ⑥ The root mean square error values ​​corresponding to different start and end points are as follows: Figure 3 As shown in (f), when p e_sp =0.146p e_max p e_ep =0.7p e_max The root mean square error is minimized, and the noise growth rate value corresponding to the start and end points is taken as the final fitting result.

[0061] like Figure 4 As shown, this embodiment also provides a test bench for evaluating the braking noise of a friction brake, including: a power module, a hydraulic module, a control module, and a signal acquisition module.

[0062] The power module includes a drive motor, a reducer, a speed and torque sensor, and a friction brake. All components of the power system are rigidly connected via shafts and flanges, with the friction disc rotated by the drive motor. Because the friction disc operates at a low speed, within the motor's low-efficiency range, a reducer is used to reduce speed and increase torque, allowing the motor to operate in its high-efficiency range, to avoid fluctuations in output speed and torque and excessive motor temperature rise. The brake mainly consists of a caliper assembly (including a caliper and piston), a mounting base, friction pads, and a friction disc. The friction pads are housed inside the caliper. The caliper assembly is bolted to the base, and the friction disc is connected to the output of the speed and torque sensor via a flange, driven by the motor. When the caliper provides normal pressure, friction is generated between the friction disc and the friction pads, providing braking torque.

[0063] The hydraulic module provides an inlet oil path and a return oil path to the friction brake. It is controlled by a two-position three-way valve with the caliper piston cylinder. When the piston cylinder is connected to the inlet oil path, the friction pads are pressurized, and the normal pressure of the brake is controlled by adjusting the displacement of the gear metering pump. When the piston cylinder is connected to the return oil path, the brake is depressurized, and the braking torque disappears.

[0064] The control module mainly refers to the control equipment and program for the drive motor and hydraulic pump, which are used to regulate the speed and pressure conditions of the brake, respectively.

[0065] The signal acquisition module includes a speed and torque sensor, a microphone, and a data acquisition control unit. Other sensors, such as an acceleration sensor, can be added if needed. The speed and torque sensor is connected to the friction disc and can acquire the braking torque and speed information of the friction disc in real time. The microphone is placed near the friction contact interface between the friction disc and the friction pads to collect friction noise signals. The brake and microphone can be covered with a soundproof cover to isolate external noise, reduce the influence of background noise, and improve the signal-to-noise ratio.

[0066] This invention discloses an experimental method and test bench for evaluating braking noise in friction brakes. The test bench features flexible sensor arrangement and utilizes a planetary reducer, facilitating low-speed testing where braking noise is more likely to occur. Simultaneously, the dynamic vibration stability characteristics of the brake are quantified using the noise growth rate. The fitting effect is measured using heuristic boundary conditions and root mean square error to obtain the optimal noise growth rate, allowing for real-time determination of vibration and noise tendencies during braking. By employing signals such as torque, speed, and noise, the evolution of braking noise is comprehensively evaluated, enriching the research on the development history of braking noise.

[0067] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A test method for evaluating braking noise of a friction brake, characterized in that, include: Braking noise tests were conducted under the set operating conditions, and braking torque, operating speed and noise signals were collected. Based on the braking torque and the operating speed, the mean characteristics and fluctuation characteristics of the speed torque are obtained, and the sound pressure level and noise growth rate are obtained based on the noise signal; Vibration and noise performance is evaluated based on the mean characteristics of the rotational speed and torque, the fluctuation characteristics, the sound pressure level, and the noise growth rate. In the evaluation of vibration and noise performance, the contributions of the mean characteristics of the rotational speed and torque, the fluctuation characteristics, the sound pressure level, and the noise growth rate need to be considered comprehensively. When any one of them is abnormal, it indicates that the vibration and noise performance has deteriorated. Methods for obtaining the noise growth rate include: The frequency components of the noise signal are obtained by performing a fast Fourier transform on the noise signal, the frequency of the screaming noise is located, and it is determined as the center frequency of the filter. The noise signal is processed using a zero-phase digital filtering method to obtain a noise signal containing only the howling frequency; The filtered signal is divided into frames based on the sampling frequency and the length of the fitting interval. The sound pressure amplitude of each frame is then calculated to obtain the upper envelope signal. The noise growth rate is obtained by exponentially fitting the rising edge of the upper envelope signal; The method for obtaining the upper envelope signal is as follows: in, For the upper envelope signal, x i The amplitude of the audio signal. N The number of data points contained in each frame; The method for obtaining the noise growth rate is as follows: in, For noise growth rate, t sp and t ep These represent the times at the start and end points of the fitted interval, respectively. p e_sp and p e_ep These represent the effective sound pressure values ​​corresponding to the start and end points, respectively.

2. A test bench for the test method of evaluating braking noise of a friction brake according to claim 1, characterized in that, include: The system includes a power module, a hydraulic module, a control module, and a signal acquisition module. The power module is used for rigid connection via a shaft system and a flange, and is driven by a drive motor to rotate the friction disc of the friction brake. The hydraulic module is used to provide oil circuits to the friction brake; The control module is used to control the speed of the drive motor via a motor control console; The signal acquisition module is used to acquire the braking torque and rotational speed information of the friction disc, as well as friction noise signals.

3. The test bench for evaluating braking noise of a friction brake as described in claim 2, characterized in that, The power module includes a drive motor, a reducer, a speed and torque sensor, and a friction brake. The motor control console is electrically connected to the drive motor, and the drive motor is mechanically connected to the reducer, the speed and torque sensor, and the friction brake in sequence. The friction brake includes a caliper assembly, a fixed base, friction pads, and a friction disc. The caliper assembly includes a caliper and a piston. The friction pads are placed inside the caliper. The caliper assembly is bolted to the fixed base. The friction disc is connected to the output end of the speed and torque sensor via a flange and is driven to rotate by the drive motor. When the caliper assembly provides normal pressure, friction is generated between the friction disc and the friction pads, providing braking torque.

4. The test bench for evaluating braking noise of a friction brake as described in claim 3, characterized in that, The hydraulic module is mechanically connected to the friction brake in the power module. The hydraulic module includes an oil inlet circuit and an oil return circuit, and is controlled by a two-position three-way valve with the caliper piston cylinder. When the caliper piston cylinder is connected to the oil inlet circuit, it pressurizes the friction pads and controls the normal pressure of the friction brake by adjusting the displacement of the gear metering pump. When the caliper piston cylinder is connected to the oil return circuit, it depressurizes the friction brake and the braking torque disappears.

5. The test bench for evaluating braking noise of a friction brake as described in claim 3, characterized in that, The signal acquisition module is electrically connected to the speed and torque sensor and also electrically connected to the friction brake. The signal acquisition module includes a data acquisition control unit, a sound card, and a microphone. The data acquisition control unit is electrically connected to the speed and torque sensor, the microphone is electrically connected to the sound card, and the sound card is electrically connected to the data acquisition control unit.

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