Noise detection method

Abstract

This invention provides a noise detection method that can identify the noise source of a unit in which a motor and inverter are integrated. [Solution] The noise discrimination method involves acquiring the frequency characteristics of the sound pressure level of noise generated from a unit that integrates a motor and an inverter that drives the motor at multiple operating points of the motor. If the sound pressure level increases as the noise frequency approaches the resonance frequency of the motor's 0th-order circular mode in the frequency characteristics of the multiple operating points, the motor is identified as the source of the noise among the motor and the inverter.

Description

Technical Field

[0001] The present invention relates to a noise discrimination method.

Background Art

[0002] Regarding noise discrimination methods, for example, Patent Document 1 describes estimating the sound source of abnormal noise from the order of the frequency of the maximum sound generated by the rotation in a rotating device and the order of each component related to the sound associated with the rotation.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a unit in which a motor and an inverter are integrated by mechatronics technology, due to the switching operation of the switching elements of the inverter, carrier noise caused by the vibration of the motor components and switching noise caused by the vibration of the inverter components may occur at substantially the same position, order, and frequency. The noise source of this type of unit cannot be discriminated by the technology described in Patent Document 1.

[0005] Therefore, the present invention has been made in view of the above problems, and an object thereof is to provide a noise discrimination method capable of discriminating the noise source of a unit in which a motor and an inverter are integrated.

Means for Solving the Problems

[0006] The noise discrimination method of the present invention involves acquiring the frequency characteristics of the sound pressure level of noise generated from a unit integrating a motor and an inverter that drives the motor at multiple operating points of the motor, and determining that the motor is the source of the noise if, in the frequency characteristics of the multiple operating points, the sound pressure level increases as the frequency of the noise approaches the resonance frequency of the motor's annular zero-order mode. [Effects of the Invention]

[0007] According to the present invention, it is possible to identify the noise source of a unit in which a motor and an inverter are integrated. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a diagram showing an example of a noise analysis system. [Figure 2] Figure 2(a) shows an example of the frequency characteristics of the sound pressure level of the switching noise of an inverter, and Figure 2(b) shows an example of the frequency characteristics of the sound pressure level of the carrier noise of a motor. [Figure 3] Figure 3 is a flowchart showing an example of a noise discrimination method. [Modes for carrying out the invention]

[0009] (Configuration of the noise analysis system) Figure 1 is a configuration diagram showing an example of a noise analysis system S. The noise analysis system S includes a terminal 1 such as a tablet or personal computer, and a noise analysis server 2. The noise analysis system S is installed, for example, in a service center for a vehicle V such as a hybrid vehicle or an electric vehicle, and analyzes noise generated from the vehicle V according to the user's request.

[0010] Vehicle V includes an ECU (Electronic Control Unit) 3, a power supply unit 4, and a transaxle 5. The transaxle 5 is an example of a unit that integrates a motor M, which is the drive source of vehicle V, and an inverter 50 that drives the motor M. Alternatively, instead of the transaxle 5, an E-axle that integrates not only the motor M and inverter 50 but also a reduction gear, or a transmission, may be provided as a unit.

[0011] The motor M and inverter 50 are configured as a single electromechanical unit. The motor M is equipped with a resolver 51 that detects its rotational speed. The resolver 51 outputs the rotational speed to the ECU 3. The power supply unit 4 includes a lithium-ion battery and a boost converter, and boosts the output of the lithium-ion battery to output a DC current to the inverter 50. The inverter 50 converts the DC current into a three-phase AC current and outputs it to the motor M. The ECU 3 controls the switching elements of the inverter 50 by using a PWM (Pulse Width Modulation) signal. The ECU 3 also controls the switching elements of the boost converter in the power supply unit 4.

[0012] Terminal 1 is an example of a computer and includes a CPU (Central Processing Unit) 10, memory 11 such as ROM (Read Only Memory) and RAM (Random Access Memory), and a microphone 12. The CPU 10 executes a series of processes in a predetermined sequence according to a program stored in memory 11.

[0013] The microphone 12 acquires sound generated from the transaxle 5 and outputs it to the CPU 10. As described later, the CPU 10 generates noise data by analyzing the sound and determines from the noise data whether the motor M or the inverter 50 is the source of the noise.

[0014] The noise analysis server 2 maintains a resonance frequency database (DB) 21 in memory (not shown) in which the resonance frequencies of the 0th order annular mode of the motor M are registered. The motor M has resonance frequencies for each of its eigenmodes of the Nth order annular mode (N=0,1,2,...) based on its structure. The resonance of the 0th order annular mode is due to the expansion and contraction of the stator (not shown) of the motor M in the radial and circumferential directions, and has a significant impact on the Nise Vibration (NV) performance of the motor M. The resonance frequency of the 0th order annular mode is calculated in advance based on, for example, prior experimental results, simulation results, and design values, but is not limited to this, and may also be estimated from the 6th or 12th order electrical noise waveforms, taking into account individual differences in the motor M and temperature-dependent errors.

[0015] During noise analysis, terminal 1 refers to the resonant frequency DB21 corresponding to the motor M via the communication network. From the sound data acquired by microphone 12, terminal 1 analyzes the frequency characteristics of the sound pressure level of the noise from the transaxle 5 at multiple operating points (rotational speeds) of the motor M. As a result of the analysis, terminal 1 determines that the noise source is the motor M if a change characteristic is obtained at each operating point where the sound pressure level increases as the frequency approaches the resonant frequency of the 0th order annular mode, and otherwise determines that the noise source is the inverter 50. Details are described below.

[0016] (Noise characteristics of motors and inverters) Figure 2(a) shows an example of the frequency characteristics of the sound pressure level of the switching noise of the inverter 50. Switching noise is generated when the switching elements in the inverter 50 are turned on and off in accordance with the input of the PWM signal.

[0017] Figure 2(b) shows an example of the frequency characteristics of the sound pressure level of the carrier noise of motor M. The carrier noise is generated from the stator and other components due to the carrier wave used to generate the PWM signal.

[0018] In the frequency characteristics of switching noise, the higher the frequency of the noise, the lower the sound pressure level (see arrow Da). On the other hand, in the frequency characteristics of carrier noise, the closer the frequency of the noise is to the resonance frequency F0 of the annular zero-order mode, the higher the sound pressure level (see arrow Db). At the resonance frequency F0, the sound pressure level shows the peak P in the annular zero-order mode.

[0019] The CPU 10 acquires the frequency characteristics of the sound pressure level of the noise at a plurality of operating points of the motor M. When, in the frequency characteristics of each operating point, the sound pressure level increases as the frequency of the noise approaches the resonance frequency F0, among the motor M and the inverter 50, the motor M is determined as the noise source. Here, the CPU 10 acquires the rotational speed from the ECU 3 as the operating point of the motor M.

[0020] In this way, the terminal 1 can determine the noise source by detecting the characteristics of the above carrier noise from the frequency characteristics of the noise at a plurality of operating points of the motor M.

[0021] (Noise discrimination method) FIG. 3 is a flowchart showing an example of the noise discrimination method. This method is executed, for example, when the terminal 1 starts a noise analysis application according to a user's operation.

[0022] First, the CPU 10 acquires sound data of the transaxle 5 from the microphone 12 (St1). Next, the CPU 10 determines whether the sound data matches one of the above switching noise and carrier noise by analyzing the sound data, for example, by order tracking or offset tracking (St2). At this time, the CPU 10 performs order analysis of the sound from the rotational speed of the motor M acquired from the ECU 3, for example, and determines whether the frequency region of the sound with a sound pressure level of a certain level or higher matches the patterns of the switching noise and the carrier noise. If the sound data does not match any of the above switching noise and carrier noise (No in St2), the execution of this method ends.

[0023] Furthermore, if the sound data matches either the switching noise or the carrier noise mentioned above (Yes in St2), the CPU 10 determines that the sound data is the noise and obtains the resonance frequency F0 of the 0th order annular mode of the motor M from the resonance frequency DB21 of the noise analysis server 2 (St3).

[0024] Next, the CPU 10 acquires noise data from the microphone 12 that shows the change in sound pressure level within a predetermined frequency range at multiple operating points of the motor M (St4). In other words, the CPU 10 acquires the frequency characteristics of the noise sound pressure level at multiple operating points. At this time, the CPU 10 may instruct the ECU 3 to use a predetermined operating point, instruct the user to drive the motor M at a predetermined operating point, or acquire previously acquired data. Furthermore, it is preferable to acquire the noise data at each operating point when the output torque of the motor M is the same in order to improve the accuracy of the data.

[0025] Next, the CPU 10 determines whether the conditions for distinguishing between switching noise and carrier noise are met (St5). These conditions include, but are not limited to, that at least two sound pressure levels in the frequency domain below the coaxial frequency F0 are included in the noise data of each operating point. If the above conditions are not met (No in St5), the execution of this method is terminated.

[0026] Furthermore, if the above conditions are met (Yes in St5), the CPU 10 determines from the noise data whether the sound pressure level increases as the noise frequency approaches the resonant frequency F0 in the frequency characteristics of each operating point (St6). If the sound pressure level increases as the noise frequency approaches the resonant frequency F0 (Yes in St6), the CPU 10 identifies the noise as carrier noise from the motor M (St7). Also, if the sound pressure level does not increase even when the noise frequency approaches the resonant frequency F0 (No in St6), the CPU 10 identifies the noise as switching noise from the inverter 50 (St8). In this way, the CPU 10 can determine whether the noise source is the motor M or the inverter 50.

[0027] The embodiments described above are preferred examples of the present invention. However, the invention is not limited thereto, and various modifications are possible without departing from the spirit of the invention. [Explanation of Symbols]

[0028] 1 terminal, 2 noise analysis servers, 5 transaxles (units), 10 CPUs, 50 inverters, M motors

Claims

[Claim 1] The frequency characteristics of the sound pressure level of noise generated from a unit integrating a motor and an inverter that drives the motor are acquired at multiple operating points of the motor. In the frequency characteristics of the plurality of operating points, if the sound pressure level increases as the frequency of the noise approaches the resonance frequency of the motor's annular zero-order mode, then the motor is identified as the source of the noise among the motor and the inverter. Noise detection method.

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