Vibration source identification method based on superposition of vibration transmission paths of centrifugal pump
Technical Field
The invention belongs to the technical field of mechanical engineering, relates to the problems of vibration reduction and noise reduction of various pump bodies, and particularly relates to a vibration source identification method based on superposition of vibration transmission paths of a centrifugal pump.
Background
The vibration noise performance of the centrifugal pump is directly related to the concealment of important military equipment such as ships and submarines. The research on the vibration transmission path of the centrifugal pump has important practical significance for effectively reducing the vibration energy of the pump and realizing the low-noise design of national defense equipment. Transfer Path Analysis (TPA) is a very valuable engineering tool that can effectively analyze the source and transmission of vibration noise. The purpose of transmission path analysis is to reduce noise and vibration and to improve the comfort or privacy of the product. The method can be applied to the development of automobiles, and can also be applied to the fields of ships, aerospace, nuclear power engineering and the like. TPA involves active parts (such as engine, rotor system) and passive structures (structural parts connected with the active parts), and when the vibration mechanism of the active parts of the system is too complicated to model or measure, we can replace the vibration source with the force or vibration on the passive surface, and finally identify the vibration source.
In a conventional calculation method, one vibration source corresponds to one transmission path or a plurality of transmission paths, and when one vibration source uses the path, the path is occupied, that is, the condition that a plurality of vibration sources are not allowed to share the same path is avoided. When two or more vibration sources exist in one path, vibration coupling is caused certainly, and further the difference between the calculated value and the measured value of the target point is large, so that the contribution analysis cannot be accurately carried out. As in fig. 2, it is assumed that the vibration source 1 and the vibration sources 2 to r have partial overlap. The vibration of the vibration source 1 is transmitted to the vibration sources 2 to r, which causes the vibration amount of the vibration sources 2 to r to increase or decrease, and the signals of the vibration sources 2 to r are mixed with part of the signals of the vibration source 1, and finally, the accurate contribution amount of the vibration sources 1 to r cannot be analyzed. The excitation force of the vibration source is indirectly calculated through the response of the surrounding reference points, when the paths overlap, the response of the vibration source 1 affects the reference points surrounding the vibration sources 2 to r, namely the response of the reference points surrounding the vibration sources 2 to r includes the response caused by the vibration source 1, so that the interference caused by the vibration source 1 should be eliminated from the reference point signal when the excitation force of the vibration sources 2 to r is accurately calculated. In order to solve the interference between the vibration signals, a decoupling method for superposition of transmission paths is provided, the method can accurately calculate the excitation force of the vibration source on the superposed paths, and more accurately analyze the contribution of each path.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a vibration source identification method based on the coincidence of the vibration transmission paths of the centrifugal pump, which can realize the decoupling of the vibration transmission paths, accurately identify main vibration sources, accurately analyze the contribution degree of each vibration source to a target point, and has the characteristics of high identification precision and strong applicability.
The technical scheme of the invention is as follows:
the vibration source identification method based on the superposition of the vibration transmission paths of the centrifugal pump is characterized by comprising the following steps of: the method comprises the following steps:
step 1: acquisition and preprocessing of vibration signals:
collecting vibration noise signals of each position of the centrifugal pump by using an acceleration sensor; the test points are divided into reference points, excitation points and target points. In vibration source identification of a centrifugal pump, a point near the vibration source is an excitation point, and a point of interest is a target point. The choice of the reference point is related to the arrangement of the excitation points. And carrying out noise reduction processing on the vibration acceleration signal, and removing an interference signal in the signal. And calculating transfer functions of the excitation point-the reference point and the excitation point-the target point according to the acquired vibration signals.
Step 2: calculating and modeling the excitation force of the vibration source:
the excitation force at the vibration source is calculated using an inverse matrix method. In order to reduce the problems with the ill-conditioned system of equations, the number of reference points set must be greater than 2 times the number of excitation points. The excitation force at each vibration source can be obtained by inverting the transfer function of the excitation point with the reference point and then multiplying by the response of the reference point.
Wherein, FnRepresents the excitation force generated by the excitation point n, CmIndicating the response of the reference point, TnmRepresenting the transfer function of the excitation point n and the reference point m.
For a multi-input single-output system, a single target point and a plurality of excitation sources exist in the system, and the plurality of excitation sources are superposed through different transmission paths:
where Y is the output of the target point, X is the input of the actuation point, HnIs the transfer function from the excitation point to the target point.
And comparing the calculated value and the test value of the vibration signal of the target point, analyzing the difference degree of the calculated value and the test value, and performing decoupling calculation on the overlapped transmission path of the frequency segments with larger phase difference.
And step 3: decoupling of the coincidence of the vibration transmission paths:
the decoupling of the coincident path is divided into three stages of solving reference point net response, solving interface load force and calculating the response of a target point:
in the stage of solving the net response of the reference points, firstly, 2-r of the vibration sources are assumed to have r-1 reference points which are respectively C2,C3……CrThe net ambient response due to vibration sources 2-r is C'2,C′3……C′rThen the net response can be expressed as:
reference point C 'in the stage of solving interfacial load force'2,C′3……C′rThe net response due to the excitation force is represented, and the excitation force at the vibration points 2 to r can be obtained from the net response. Accurately calculating interface load force F'2 F′3 … F′mThe method is characterized in that the key of a transmission path decoupling technology is provided, and the calculation method is advanced in that the actual load force of each excitation point can be accurately calculated. Calculating the interface load force of the excitation points 2-r by a matrix inversion method:
in the phase of calculating the response of the target point, F is defined1RTHrThe response of the target point is the sum of the individual path response values minus the sum of the overlap responses of its system. The actual load force versus transfer function calculates the calculated value of the response point by the following formula.
And 4, step 4: path contribution analysis
And comparing the calculated values of the target points with the matching degree of the test values, and analyzing the calculated values of the vibration sources at the target points. Under the characteristic frequency, drawing a vibration vector diagram of each excitation source and the total contribution, wherein the judgment standard is as follows: the excitation source with the largest projection absolute value of each excitation source in the direction of the total contribution amount is the main vibration source.
The invention has the beneficial effects that: a transfer function between an excitation point-target point and an excitation point-reference point of the centrifugal pump is established by using a coincident transfer path decoupling method, a vibration transfer model of each vibration source and the base of the centrifugal pump is constructed, the vibration coupling condition is effectively avoided, and the dependence of the traditional vibration source identification technology on expert experience is eliminated. The method has multidimensional analysis capability, and improves the accuracy of vibration noise source identification.
Drawings
FIG. 1 is a computational flow diagram of a method of vibration source identification based on coincidence of the paths of the centrifugal pump vibration transmission;
FIG. 2 is a schematic illustration of the path coincidence problem
FIG. 3 is a schematic view of a vibration decoupling process;
FIG. 4 is a graph of the contribution of different excitation sources to a target point;
FIG. 5 is (a) a vibration vector diagram of each excitation source with 50Hz, (b) a vibration vector diagram of each excitation source with 100Hz, (c) a vibration vector diagram of each excitation source with 262Hz, (d) a vibration vector diagram of each excitation source with 300Hz, (e) a vibration vector diagram of each excitation source with 350Hz, under different frequencies;
fig. 6 is a transfer function of different excitation and target points.
Detailed Description
The following detailed description of the invention refers to the accompanying drawings.
In this embodiment, a vibration source identification method based on superposition of vibration transmission paths of a centrifugal pump is shown in fig. 1, which is a calculation flow chart of vibration transmission path analysis, and includes the following steps:
step 1: acquisition and preprocessing of vibration signals:
collecting vibration noise signals of each position of the centrifugal pump by using an acceleration sensor; the test points are divided into reference points, excitation points and target points. In vibration source identification of a centrifugal pump, a point near the vibration source is an excitation point, and a point of interest is a target point. The choice of the reference point is related to the arrangement of the excitation points. And carrying out noise reduction processing on the vibration acceleration signal, and removing an interference signal in the signal. And calculating transfer functions of the excitation point-the reference point and the excitation point-the target point according to the acquired vibration signals.
In particular, considering that there are three excitation points for the vibrations of the centrifugal pump, each excitation point needs to consider two vibration directions, for a total of 6 transmission paths. Two acceleration sensors are arranged at the motor, the bearing, the volute and the base respectively to test the X, Z-directional vibration response thereof. In order to ensure the correctness of the calculation of the excitation force, the reference point is arranged close to the excitation points and the number of the reference points is ensured to be not less than twice of the number of the excitation points, so that 3 acceleration sensors are respectively pasted near three excitation sources to be used as the output of the reference points.
Step 2: calculating and modeling the excitation force of the vibration source:
the excitation force at the vibration source is calculated using an inverse matrix method. In order to reduce the problems with the ill-conditioned system of equations, setting the number of reference points requires 2 times the number of excitation points. The excitation force at each vibration source can be obtained by inverting the transfer function of the excitation point with the reference point and multiplying by the response of the reference point.
Wherein, FnRepresents the excitation force generated by the excitation point n, CmIndicating the response of the reference point, TnmRepresenting the transfer function of the excitation point n and the reference point m.
For a multi-input single-output system, a single target point and a plurality of excitation sources exist in the system, and the plurality of excitation sources are superposed through different transmission paths:
where Y is the output of the target point, X is the input of the actuation point, HnIs the transfer function from the excitation point to the target point.
And comparing the calculated value and the test value of the vibration signal of the target point, analyzing the difference degree of the calculated value and the test value, and performing decoupling calculation on the overlapped transmission path of the frequency segments with larger phase difference.
Specifically, a calculation method of transfer path coincidence is applied to process data obtained by testing. And (4) setting the rotating speed of the motor at 3000r/min in an experiment, and calculating the synthesized base position acceleration as an output signal. Comparing the output signal synthesized by the traditional TPA model, the output signal synthesized by the improved TPA model and the actually measured output signal.
The coincidence degree of the output signal of the improved TPA model and the actual test value is greatly higher than that of the traditional TPA and the test value. At the characteristic frequencies of 50Hz, 100Hz, 262Hz and 300Hz, the fitting degree of the traditional TPA calculated value and the test value is poor, while the fitting degree of the improved TPA calculated value and the test value is good at the characteristic frequency, thereby verifying the scientificity of the improved method.
And step 3: the decoupling method of the superposition of the vibration transmission paths comprises the following steps:
the decoupling method for the coincident path comprises three stages of solving reference point net response, solving interface load force and calculating the response of a target point:
in the request ofIn the reference point solving net response stage, assuming that 2-r of vibration sources have r-1 reference points which are respectively C2,C3……CrThe net ambient response due to vibration sources 2-r is C'2,C′3……C′rThen the net response can be expressed as:
reference point C 'in the stage of solving interfacial load force'2,C′3……C′rThe net response due to the excitation force is represented, and the excitation force at the vibration points 2 to r can be obtained from the net response. Accurately calculating interface load force F'2 F′3 … F′mThe method is characterized in that the key of a transmission path decoupling technology is provided, and the calculation method is advanced in that the actual load force of each excitation point can be accurately calculated. Calculating the interface load force of the excitation points 2-r by a matrix inversion method:
in the phase of calculating the response of the target point, F is defined1RTHrThe response of the target point is the sum of the individual path response values minus the sum of the overlap responses of its system. The actual load force versus transfer function calculates the calculated value of the response point by the following formula.
And 4, step 4: path contribution analysis
And comparing the calculated values of the target points with the matching degree of the test values, and analyzing the calculated values of the vibration sources at the target points. Under the characteristic frequency, drawing a vibration vector diagram of each excitation source and the total contribution, wherein the judgment standard is as follows: the excitation source with the largest projection absolute value of each excitation source in the direction of the total contribution amount is the main vibration source.
Specifically, as can be seen from fig. 5, the Z-direction of the casing is dominant in the base contribution of the centrifugal pump in the frequency range of 200Hz to 500Hz, and is the main cause of the base vibrating violently. At a frequency of 50Hz, the X-direction contribution of the bearing is the largest, and at a frequency of 100Hz, the X-direction contribution of the motor is the largest. The calculation of the vibration total contribution is not simple amplitude addition subtraction, but vector calculation. The bearing X has the largest contribution to a target point at 50Hz, and the projection value of the bearing X is far larger than the projection values of other paths; the contribution amount of the motor X to a target point is maximum at 100Hz, and the projection value of the motor X is far larger than that of other paths; the contribution of the housing Z to the target point is greatest at 262Hz and the additive effect of the path and the total contribution is greater than the total contribution of the path. The vibration phase difference of the bearing X, the motor X and the total contribution amount is larger than 90 degrees, and the superposition effect on the total contribution amount is a negative value; the contribution of the Z direction of the housing to the target point is greatest at 300Hz from X, i.e., the frequency at which the housing is the dominant vibration source causing the base to vibrate. The additive effect of other paths on the total contribution of the paths is zero or negative.
Although the embodiments of the present invention have been shown and described, it is understood that the above embodiments are only for illustrating the technical solutions of the present invention and should not be construed as limiting the present invention, and those skilled in the art can make modifications and substitutions to the above embodiments within the scope of the present invention without departing from the principle and spirit of the present invention.