A method for measuring lateral excitation forces of a propeller

Abstract

The present application relates to the technical field of propeller hydrodynamic measurement method, and particularly relates to a propeller lateral excitation force measurement method, which converts the dynamic force signal measured by a sensor in a rotating coordinate system XOY into a propeller lateral excitation force signal in a fixed coordinate system X1OY1 in the form of equal-phase resampling, and can effectively evaluate the propeller lateral line spectrum excitation force. The main steps include test system calibration, signal synchronous acquisition, equal-phase resampling, coordinate transformation and Fourier transformation. The method has clear design process, clear operation and great engineering practical value.

Description

Technical Field

[0001] This invention relates to the technical field of propeller hydrodynamic measurement methods, and in particular to a method for measuring the lateral excitation force of a propeller. Background Technology

[0002] Due to the non-uniformity of the incoming airflow, the propeller generates excitation force during rotation. This excitation force not only directly radiates low-frequency noise, but also is transmitted to the hull through the shaft system, causing coupled vibrations at the stern and producing sound, which seriously affects the submarine's acoustic stealth performance.

[0003] Currently, existing technologies mainly focus on studying the axial excitation force of propellers in model tests, while the study of the lateral excitation force of propellers is mainly obtained through numerical calculations. There is no effective experimental measurement method to measure the lateral excitation force of propellers. Summary of the Invention

[0004] In response to the shortcomings of the existing production technology, the applicant provides a method for measuring the lateral excitation force of a propeller, which can effectively solve the problem of the lateral excitation force of the propeller and effectively evaluate the lateral line spectrum excitation force of the propeller.

[0005] The technical solution adopted in this invention is as follows:

[0006] A method for measuring the lateral excitation force of a propeller includes the following steps:

[0007] S1: Calibration of the measurement system;

[0008] S1.1: Fix a mass block with the same mass as the test propeller to the end face of the three-component force sensor;

[0009] S1.2: A standard piezoelectric single-component force sensor with a known sensitivity coefficient is bonded to the outer surface of the mass block and connected to the vibrator via a flexible connecting rod. The sensitivity coefficients k of the three-component force sensor in the X and Y directions are obtained by frequency sweep calibration. x k y And the system's lateral measurement frequency ω, k x =kv / v x k y =kv / v y Where k is the sensitivity coefficient of the standard single-component piezoelectric sensor, v is the output voltage of the standard single-component force sensor, and v x For the X-axis voltage output of the three-component force sensor, v y The Y-axis voltage output is for a three-component force sensor.

[0010] S2: Synchronous signal acquisition;

[0011] During testing, the mass block was replaced with a test propeller. When the propeller rotated, the three-component piezoelectric sensor output a lateral voltage signal V. x V y The internal incremental encoder of the power instrument synchronously outputs A-phase pulse signals and Z-phase zero-position pulse signals; after low-pass filtering of the voltage signals, they are processed by formula F. x =k x V x F y =k y V y The dynamic force signal of the sensor in the rotating coordinate system XOY can be obtained;

[0012] S3: Equal-phase resampling;

[0013] Starting with the encoder's Z-phase zero-position pulse signal, and using the A-phase pulse signal as the sampling point, the dynamic force signal F is... x F y Perform equal-phase resampling to obtain different phase angles β within the complete period. i Downward dynamic force signal F x1 F y1 ;

[0014] S4: Coordinate transformation;

[0015] The dynamic force signal F obtained after resampling with equal phase x1 F y1 The dynamic force signal F in a fixed coordinate system can be obtained by the following formula. x2 F y2 ;

[0016] F y2 =F y1 cos(α+β i )-F x1 sin(α+β i )

[0017] F x2 =F y1 sin(α+β i )+F x1 cos(α+β i )

[0018] S5: Fourier transform;

[0019] F x2 F y2 The lateral line spectrum excitation force during propeller rotation can be obtained by performing a Fourier transform on the time-domain signal.

[0020] Its further technical solution lies in:

[0021] The measurement system is structured as follows: it includes a rotational power instrument, a three-component force sensor is fixedly mounted on the end of the rotational shaft of the rotational power instrument, a mass block with the same mass as the test propeller is fixed to the end face of the three-component force sensor, a single-component force sensor is bonded to the outer surface of the mass block, and the single-component force sensor is connected to the exciter through a flexible connecting rod.

[0022] The outer surface of the mass block has reserved orthogonal planes, which are parallel to the coordinate axes X and Y, respectively.

[0023] The single-component force sensor is installed on a plane parallel to the X-axis or Y-axis.

[0024] The mass block has a frustum-shaped structure.

[0025] In S3, to obtain the dynamic force signal on the fixed coordinate system X1OY1, it is necessary to start with the encoder's Z-phase zero-position pulse signal and use the A-phase pulse signal as the sampling point to sample the dynamic force signal F. x F y Equal-phase resampling is performed, with each pulse signal corresponding to one sampling of the sensor signal, to obtain different phase angles β within the complete cycle. i The dynamic force signal F from the lower sensor x1 F y1 Phase angle β i This is based on the encoder's Z-phase zero-position pulse signal, which has a phase difference α with the fixed coordinate system X1OY1. When the rotating coordinate system XOY of the three-component force sensor coincides with the fixed coordinate system X1OY1, the sensor's Y-axis signal is at its minimum. Therefore, the phase difference α can be expressed as the phase difference between the A-phase pulse and the Z-phase zero-position pulse signal corresponding to the minimum Y-axis signal, i.e., α = n × 360 / N, where n is the number of pulse intervals between the A-phase pulse and the Z-phase zero-position pulse signal corresponding to the minimum Y-axis signal. Phase angle β i = i×360 / N, where i is the number of pulse intervals between the Z-phase zero-position pulse signal and the corresponding A-phase sampling point pulse.

[0026] In S4, the clockwise rotation of the propeller is the positive direction.

[0027] The beneficial effects of this invention are as follows:

[0028] This invention features a compact and rational structure, and is easy to operate. It converts the dynamic force signal measured by the sensor in the rotating coordinate system XOY into the propeller lateral excitation force signal in the fixed coordinate system X1OY1 through equal-phase resampling, effectively evaluating the propeller lateral line spectrum excitation force. The main steps include measurement system calibration, synchronous signal acquisition, equal-phase resampling, coordinate transformation, and Fourier transform. The overall design process is clear, the operation is straightforward, and it has significant engineering practical value. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the structure of the present invention.

[0030] Figure 2 This is a timing diagram of the sensor output signal and the encoder synchronization pulse signal of the present invention.

[0031] Figure 3 This is a phase difference diagram between the rotating coordinate system XOY and the fixed coordinate system X1OY1 of the sensor of the present invention.

[0032] Among them: 1. Vibration machine; 2. Mass block; 3. Three-component force sensor; 4. Dynamic instrument; 5. Single-component piezoelectric sensor. Detailed Implementation

[0033] The specific embodiments of the present invention will now be described with reference to the accompanying drawings.

[0034] The detailed working process of this invention is as follows:

[0035] like Figure 1 As shown, the three-component force sensor 3 is fixed to the end of the rotating shaft of the power instrument 4. Rotating the rotating shaft of the power instrument 4 causes the rotating coordinate system XOY of the three-component force sensor to coincide with the fixed coordinate system X1OY1, and then the rotating shaft is locked. The lateral force of the propeller corresponds to the force in the XY plane of the three-component force sensor 3.

[0036] Since the mass of the test propeller has a significant impact on the measurement frequency of the test system, a mass block 2 with the same mass as the test propeller needs to be fixed to the end face of the three-component piezoelectric sensor 3 during the calibration of the test system. At this time, the orthogonal planes reserved on the outer surface of the mass block 2 are parallel to either the X or Y axis of the coordinate system. This reduces interference caused by angular deviations between the force and the main axis direction of the three-component force sensor during calibration.

[0037] A standard single-component piezoelectric sensor 5 with a known sensitivity coefficient is bonded to the outer surface of the mass block 2 on a plane parallel to the X-axis, and connected to the exciter 1 via a flexible connecting rod. The measurement frequency ω is obtained through frequency sweep calibration. y The Y-axis sensitivity coefficient k of the lower three-component piezoelectric force sensor y k y =kv / v y Where k is the sensitivity coefficient of the standard single-component piezoelectric sensor, v is the output voltage of the standard single-component piezoelectric sensor, and v y This is the Y-axis voltage output of a three-component piezoelectric sensor.

[0038] A standard single-component piezoelectric sensor 5 with a known sensitivity coefficient is bonded to the outer surface of the mass block 2 on a plane parallel to the Y-axis, and connected to the exciter 1 via a flexible connecting rod. The measurement frequency ω is obtained through frequency sweep calibration. xThe Y-axis sensitivity coefficient k of the lower three-component force sensor x k x =kv / v x Where k is the sensitivity coefficient of the standard single-component force sensor, v is the output voltage of the standard single-component force sensor, and v x This is the Y-axis voltage output of a three-component force sensor.

[0039] During the test, the exciter 1 and standard sensor 5 were removed, and mass block 2 was replaced with the test propeller. The power instrument was started and its shaft rotated to the specified speed, and the lateral output voltage signal V from the three-component force sensor was simultaneously acquired. x V y The power unit's internal incremental encoder outputs A-phase pulse signals (N pulses per revolution) and Z-phase zero-position pulse signals (1 pulse per revolution). The voltage signals are low-pass filtered and then processed using formula F. x =k x V x F y =k y V y The dynamic force signal of the sensor in the rotating coordinate system XOY is obtained.

[0040] like Figure 2 As shown, in order to obtain the dynamic force signal on the fixed coordinate system X1OY1, it is necessary to start with the encoder's Z-phase zero-position pulse signal and use the A-phase pulse signal as the sampling point to sample the dynamic force signal F. x F y Equal-phase resampling is performed, with each pulse signal corresponding to one sampling of the sensor signal, to obtain different phase angles β within the complete cycle. i The dynamic force signal F from the lower sensor x1 F y1 Phase angle β i This is based on the encoder's Z-phase zero-position pulse signal, which has a phase difference α with the fixed coordinate system X1OY1. When the rotating coordinate system XOY of the three-component force sensor coincides with the fixed coordinate system X1OY1, the sensor's Y-axis signal is at its minimum. Therefore, the phase difference α can be expressed as the phase difference between the A-phase pulse and the Z-phase zero-position pulse signal corresponding to the minimum Y-axis signal, i.e., α = n × 360 / N, where n is the number of pulse intervals between the A-phase pulse and the Z-phase zero-position pulse signal corresponding to the minimum Y-axis signal. Phase angle β i = i×360 / N, where i is the number of pulse intervals between the Z-phase zero-position pulse signal and the corresponding A-phase sampling point pulse.

[0041] like Figure 3 As shown, taking the clockwise rotation of the propeller as the positive direction, the dynamic force signal F after equal-phase sampling is obtained using the following formula. x1 F y1Converted into a dynamic force signal F in a fixed coordinate system x2 F y2 .

[0042] F y2 =F y1 cos(α+β i )-F x1 sin(α+β i )

[0043] F x2 =F y1 sin(α+β i )+F x1 cos(α+β i )

[0044] F x2 F y2 The lateral line spectrum excitation force during propeller rotation can be obtained by performing a Fourier transform on the time-domain signal.

[0045] The above description is an explanation of the method of the present invention and not a limitation thereof. The scope of the method of the present invention is defined by the claims. Within the scope of protection of the present invention, any form of modification may be made, such as changing the installation angle of the piezoelectric force sensor or replacing the piezoelectric force sensor with a strain gauge force sensor.

Claims

1. A method for measuring the lateral excitation force of a propeller, characterized in that: The following steps are included: S1: Calibration of the measurement system; S1.1: Fix a mass block (2) with the same mass as the test propeller to the end face of the three-component force sensor (3); S1.2: A standard piezoelectric single-component force sensor (5) with a known sensitivity coefficient is bonded to the outer surface of the mass block (2) and connected to the exciter (1) via a flexible connecting rod. The sensitivity coefficients k of the three-component force sensor (3) in the X and Y directions are obtained by frequency sweep calibration. x k y And the system's lateral measurement frequency ω, k x =kv / v x k y =kv / v y Where k is the sensitivity coefficient of the standard single-component piezoelectric sensor, v is the output voltage of the standard single-component force sensor, and v x For the X-axis voltage output of the three-component force sensor, v y The Y-axis voltage output is provided by a three-component force sensor. S2: Synchronous signal acquisition; During the test, the mass block (2) was replaced with a test propeller. When the propeller rotated, the three-component force sensor (3) output a voltage signal V laterally. x V y The power instrument (4) uses an internal incremental encoder to synchronously output A-phase pulse signals and Z-phase zero-position pulse signals; after low-pass filtering of the voltage signal, it is processed by formula F. x =k x V x F y =k y V y The dynamic force signal of the sensor in the rotating coordinate system XOY can be obtained; S3: Equal-phase resampling; Starting with the encoder's Z-phase zero-position pulse signal, and using the A-phase pulse signal as the sampling point, the dynamic force signal F is... x F y Perform equal-phase resampling to obtain different phase angles β within the complete period. i Downward dynamic force signal F x1 F y1 ; S4: Coordinate transformation; The dynamic force signal F obtained after resampling with equal phase x1 F y1 The dynamic force signal F in a fixed coordinate system can be obtained by the following formula. x2 F y2 ; S5: Fourier transform; F x2 F y2 The lateral line spectrum excitation force during propeller rotation can be obtained by performing a Fourier transform on the time-domain signal. In S3, to obtain the dynamic force signal on the fixed coordinate system X1OY1, it is necessary to start with the encoder's Z-phase zero-position pulse signal and use the A-phase pulse signal as the sampling point to sample the dynamic force signal F. x F y Equal-phase resampling is performed, with each pulse signal corresponding to one sampling of the sensor signal, to obtain different phase angles β within the complete cycle. i The dynamic force signal F from the lower sensor x1 F y1 Phase angle β i This is based on the encoder's Z-phase zero-position pulse signal, which has a phase difference α with the fixed coordinate system X1OY1. When the rotating coordinate system XOY of the three-component force sensor coincides with the fixed coordinate system X1OY1, the sensor's Y-axis signal is at its minimum. Therefore, the phase difference α can be expressed as the phase difference between the A-phase pulse and the Z-phase zero-position pulse signal corresponding to the minimum Y-axis signal, i.e., α = n × 360 / N, where n is the number of pulse intervals between the A-phase pulse and the Z-phase zero-position pulse signal corresponding to the minimum Y-axis signal. The phase angle β... i =i×360 / N, where i is the number of pulse intervals between the Z-phase zero-position pulse signal and the corresponding A-phase sampling point pulse.

2. The method for measuring the lateral excitation force of a propeller as described in claim 1, characterized in that: The structure of the measurement system is as follows: it includes a rotational power instrument (4), a three-component force sensor (3) is fixedly installed on the end of the rotating shaft of the rotational power instrument (4), a mass block (2) with the same mass as the test propeller is fixed on the end face of the three-component force sensor (3), a single-component force sensor (5) is bonded to the outer surface of the mass block (2), and the single-component force sensor (5) is connected to the exciter (1) through a flexible connecting rod.

3. The method for measuring the lateral excitation force of a propeller as described in claim 2, characterized in that: The outer surface of the mass block (2) has an orthogonal plane reserved, which is parallel to the coordinate axes X and Y respectively.

4. The method for measuring the lateral excitation force of a propeller as described in claim 3, characterized in that: The single-component force sensor (5) is installed on a plane parallel to the X-axis or Y-axis.

5. The method for measuring the lateral excitation force of a propeller as described in claim 2, characterized in that: The mass block (2) has a frustum-shaped structure.

6. The method for measuring the lateral excitation force of a propeller as described in claim 1, characterized in that: In S4, the clockwise rotation of the propeller is the positive direction.

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