A method and device for high-precision real-time identification of ship propeller shaft thrust

Abstract

This invention discloses a high-precision real-time identification method and device for ship propeller shaft thrust, comprising the following steps: processing a measuring device and installing it on the rotating shaft; acquiring the longitudinal strain and ambient temperature of the measuring device, and constructing a first equation relating thrust, temperature, and strain; differentiating the first equation and discretizing it over time to obtain a second equation; obtaining the system matrix equation and observation equation based on the second equation; predicting the thrust state at the k-th time step based on the matrix equation, and estimating the thrust state based on the observation equation; recursively pushing the time to the (k+1)-th time step, repeating the state prediction and state estimation, and finally obtaining the dynamic process of thrust. This invention has strong anti-interference capabilities, can compensate for thermal deformation errors caused by changes in ambient temperature, and can maintain high measurement accuracy even in strong interference noise. Furthermore, in this invention, strain gauges are attached to the measuring device, allowing for the calibration of strain gauge sensitivity coefficients in the laboratory, thereby eliminating the influence of external factors such as strain gauge attachment method and adhesive type.

Description

Technical Field

[0001] The invention belongs to the field of ship power, and in particular relates to a method and a device for high-precision real-time identification of ship propeller shaft thrust. Background Art

[0002] Online, real-time and accurate monitoring of the thrust of the ship propulsion system at various speeds can provide accurate data requirements for ship rapidity prediction, navigation status monitoring, ship-engine-propeller optimization matching, etc., which has important engineering significance. However, the current technical bottleneck is that it is difficult to accurately and real-time monitor the propeller thrust in the actual ship interference environment. The main reason is that the weak deformation signal generated by the thrust on the shafting is easily submerged by the temperature thermal deformation, mechanical noise, electromagnetic noise, shafting vibration and other noises in the engine room, making it difficult to identify the weak thrust signal from the measured deformation signal.

[0003] Currently, there are some patents proposed related to thrust testing, including method and device types.

[0004] Method: A method for analyzing the stress state of a turbine generator shaft. The patent includes the following steps: S1. Establish a finite element calculation model based on the test shaft; S2. Verify the correctness of the finite element model through theoretical calculation; S3. Arrange strain gauges on the shaft to test the axial stress of the shaft; S4. Apply boundary conditions in the finite element model to make the calculated stress equal to the test stress; S5. Establish the relationship between the maximum stress value of the shaft and the on-site stress test value by analyzing the calculation results of the finite element calculation model and the on-site stress test results, so as to achieve the purpose of directly evaluating the life and safety status of the shaft by the on-site stress test results.

[0005] Device type: underwater pod or propeller propulsion device model drive and thrust, torque test system. The patent includes a drive module, a measurement module and a transmission module. The drive module uses a DC motor, the motor rotating shaft is connected to the measurement module, and the other end of the measurement module is connected to the propeller. The strain gauge on the measurement module can measure the strain generated by the thrust. The transmission module transmits the signal and the input voltage of the strain gauge through non-contact coupling.

[0006] Commercial vehicle thrust rod axial force test device. The patent includes a thrust rod, a strain gauge, and a data acquisition instrument. The thrust rod and the strain gauge are fixedly installed, and the strain gauge is fixedly installed on the thrust rod surface parallel to the thrust rod axis through an adhesive layer; the strain gauge is electrically connected to the data acquisition instrument; and the data acquisition instrument collects data from the strain gauge.

[0007] However, the above patents all have the major defect of low anti-interference ability and the technical problem of low test accuracy in temperature changes and strong interference noise environments. Summary of the invention

[0008] The technical purpose of the present invention is to provide a method and device for high-precision real-time identification of ship propeller shaft thrust, so as to solve the technical problem of low measurement accuracy caused by ambient temperature changes and strong interference noise.

[0009] To solve the above problems, the technical solution of the present invention is:

[0010] A method for high-precision real-time identification of ship propeller shaft thrust comprises the following steps:

[0011] Obtain strain signals of at least two strain gauges installed on the ship's propeller shaft, and the ambient temperature of the ship's propeller shaft;

[0012] According to the strain signal and the ambient temperature, a first equation of the thrust of the ship propeller shaft and its longitudinal strain is constructed; the first equation is derived and discretized according to the time step to obtain a second equation; based on the second equation, it is expressed as a matrix equation and an observation equation;

[0013] Based on the matrix equation and observation equation, the state prediction is completed and the The prior estimate corresponding to the time step; based on the prior estimate, complete the The state estimation at the time step is obtained The estimated variables corresponding to the time steps; recursively extend the time to The state prediction and state estimation are repeated for a time step to obtain new estimated variables, and the shafting thrust of the ship's propeller shaft is calculated based on the new estimated variables and the first equation.

[0014] Among them, the specific steps of constructing the first equation of the ship propeller shaft thrust and its longitudinal strain according to the strain signal and ambient temperature are as follows:

[0015] The strain signals of different strain gauges are read respectively, and their values ​​satisfy the following formula:

[0016]

[0017] in, Strain gauge The strain generated, is the longitudinal strain caused by the thrust of the ship's propeller shaft, is the strain caused by the bending moment, is the thermal expansion coefficient of the shaft system, is the initial ambient temperature, is the ambient temperature;

[0018] The readings of strain gauges connected to different strain gauges The formula is:

[0019]

[0020] Ship propeller shaft thrust With longitudinal strain The relationship satisfies the following first equation:

[0021]

[0022] in, and are the elastic modulus and cross-sectional area of ​​the shaft section where the strain gauge is installed.

[0023] Among them, the first equation is derived and discretized according to the time step to obtain the second equation. The specific formula is:

[0024]

[0025] in, For the The strain gauge readings at each time step are For the The strain gauge readings at each time step are For the The thrust change value at each time step is: For the The change of ambient temperature in a time step.

[0026] Among them, the matrix equation based on the second equation is specifically:

[0027] make , then the matrix equation is

[0028]

[0029] in, is the state transfer matrix, is the model error of the simulated noise;

[0030] Based on the second equation, the observation equation is expressed as

[0031]

[0032] in, is the change in measured strain and measured temperature, is the observation equation, To measure noise.

[0033] Among them, in time step, and get The a priori estimate corresponding to each time step is:

[0034]

[0035]

[0036] in, for In the The prior estimate of time steps is for In the The posterior estimate of time steps is for The estimated error covariance matrix is for The estimated error covariance matrix is is the model error The covariance matrix of

[0037] In the time step, and get The estimated variables corresponding to each time step are:

[0038]

[0039]

[0040]

[0041]

[0042] in, is the gain matrix, is the deviation sequence between the measured signal and the prior estimate, To measure noise The covariance matrix of

[0043] Covariance matrix With the covariance matrix The formulas are:

[0044]

[0045]

[0046]

[0047] .

[0048] Further preferably, before obtaining the strain signals of at least two strain gauges installed on the propeller shaft of the ship and the ambient temperature of the propeller shaft of the ship, the following steps are also included:

[0049] Select the measuring point on the propeller shaft of the ship and measure the shaft diameter at the measuring point to obtain the cross-sectional area ;

[0050] Arrange the mounting ring at the measuring point to stick two strain gauges, and check the sensitivity coefficient of the strain gauges;

[0051] The two strain gauges are connected using a half-bridge connection.

[0052] A high-precision real-time identification device for ship propeller shaft thrust is provided with the above-mentioned high-precision real-time identification method for ship propeller shaft thrust.

[0053] It includes an installation component and a test piece; the installation component is installed at a test point on the propeller shaft of the ship; and the test piece is attached to the installation component;

[0054] The mounting assembly includes a first mounting member and a second mounting member;

[0055] The first mounting member and the second mounting member have the same structure, and both include a first arc-shaped member, a second arc-shaped member and at least one connecting rod;

[0056] The first arc-shaped member and the second arc-shaped member are both semicircular, and two ends of the connecting rod are respectively connected to one side of the first arc-shaped member and one side of the second arc-shaped member, and the first arc-shaped member and the second arc-shaped member are symmetrically arranged; at least one test piece is installed on the connecting rod;

[0057] Both ends of the first arc-shaped member and the second arc-shaped member are provided with connecting holes, the opening direction of the connecting holes is perpendicular to the connecting rod, and the first mounting member and the second mounting member cooperate with bolts and nuts through the connecting holes to achieve bolt connection.

[0058] Specifically, the first mounting member and the second mounting member are each provided with two connecting rods;

[0059] Both ends of the two connecting rods are respectively connected to one side of the first arc-shaped member and one side of the second arc-shaped member, and the connection positions of the two connecting rods divide the first arc-shaped member or the second arc-shaped member into three arc sections; each connecting rod is provided with at least one test piece.

[0060] The test piece is a strain gauge, and two oppositely arranged strain gauges are electrically connected using a half-bridge connection.

[0061] Due to the adoption of the above technical solution, the present invention has the following advantages and positive effects compared with the prior art:

[0062] On the one hand, the present invention uses the estimated-corrected weighted recursive least squares estimation to identify propeller thrust from the strain signal with noise interference, which has strong anti-interference ability and can maintain high measurement accuracy in a strong interference noise environment. On the other hand, a functional relationship between ambient temperature and thermal deformation is established in the recursive equation, so that the thermal deformation error caused by temperature can be compensated in the variable recursive process. Finally, the strain gauge of the present invention is attached to the mounting assembly, and the sensitivity coefficient of the strain gauge after attachment can be calibrated and checked in the laboratory, thereby eliminating the influence of external factors such as the strain gauge attachment method and glue type. The two strain gauges use a half-bridge connection to eliminate the influence of the bending deformation of the rotating shaft. The strain gauge directly transmits the data to the computer for subsequent processing through slip rings or wireless transmission. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the following detailed description of the preferred embodiment.The drawings are only for the purpose of illustrating the preferred embodiments and are not to be construed as limiting the invention.

[0064] Figure 1 is a structural diagram of the installation assembly of the present invention;

[0065] Figure 2 A structural diagram of another embodiment of the mounting assembly of the present invention;

[0066] Figure 3 This is a structural diagram of a high-precision real-time identification device for ship propeller shaft thrust of the present invention;

[0067] Figure 4 This is a schematic diagram of the strain gauge half-bridge connection of the present invention;

[0068] Figure 5 A high-precision real-time identification method for ship propeller shaft thrust of the present invention;

[0069] Figure 6 This is a comparison diagram of the strain and thrust identification effects of the present invention.

[0070] Description of Reference Numerals

[0071] 1: Ship propeller shaft; 2: Mounting assembly; 3: Connection hole; 4: Strain gauge. DETAILED DESCRIPTION

[0072] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the specific implementation methods of the present invention will be described below with reference to the accompanying drawings. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings and other implementation methods can be obtained based on these drawings without creative work.

[0073] In order to simplify the drawings, only the parts related to the present invention are schematically shown in each figure, and they do not represent the actual structure of the product. In addition, in order to simplify the drawings and facilitate understanding, in some figures, only one of the parts with the same structure or function is schematically drawn or marked. In this article, "one" not only means "only one", but also means "more than one".

[0074] The following is a further detailed description of a method and device for high-precision real-time identification of the thrust of a ship propeller shaft 1 proposed by the present invention in conjunction with the accompanying drawings and specific embodiments. The advantages and features of the present invention will become more apparent from the following description and claims.

[0075] See also Figure 5 , this embodiment provides a high-precision real-time identification method for the thrust of a ship propeller shaft 1.

[0076] Before implementing this embodiment, it is necessary to select a measuring point on the ship propeller shaft 1. Usually, the measuring point is selected near the propeller of the ship propeller shaft 1, and the shaft diameter at the measuring point is measured to obtain the cross-sectional area. .

[0077] According to the diameter of the propeller shaft 1 of the ship, a mounting ring is installed at the measuring point, such as Figure 1 , Figure 2 See Figures 2 to 4 At least two strain gauges 4 are attached to the mounting ring, and the two strain gauges 4 are installed on both sides of the mounting ring, that is, they are arranged opposite to each other. After the installation is completed, the sensitivity coefficient of the strain gauge 4 is calibrated in the laboratory (the mounting ring has not been installed on the ship propeller shaft 1 during the calibration). The mounting ring is fixed to the shaft with bolts and nuts, such as Figure 3 The two strain gauges 4 on the mounting ring are connected in a half-bridge connection mode to eliminate the bending deformation caused by the bending of the rotating shaft, thus completing the preparation stage.

[0078] See also Figure 5 In this embodiment, first, it is necessary to obtain the strain signals of at least two strain gauges 4 installed on the ship propeller shaft 1 and the ambient temperature of the ship propeller shaft 1. Then, the first equation of the thrust of the ship propeller shaft 1 and its longitudinal strain is constructed according to the strain signal and the ambient temperature.

[0079] When the ship propeller shaft 1 is subjected to propeller thrust and bending moment, the degrees of the two different strain gauges 4 are:

[0080]

[0081] in, Strain gauge 4 The strain generated, is the longitudinal strain caused by the thrust of the ship's propeller shaft 1, is the strain caused by the bending moment, is the thermal expansion coefficient of the shaft system, is the initial ambient temperature, is the ambient temperature.

[0082] The strain gauges are electrically connected to different strain gauges 4, and their readings Satisfaction:

[0083] .

[0084] Thus, the thrust of the ship propeller shaft 1 is obtained With longitudinal strain The relationship between satisfies the following first equation:

[0085]

[0086] in, and They are respectively the elastic modulus and cross-sectional area of ​​the shaft section where the strain gauge 4 is installed.

[0087] Then, the first equation is differentiated and discretized by time step to obtain the second equation, which is as follows:

[0088]

[0089] in, For the The strain gauge readings at each time step are For the The strain gauge readings at each time step are For the The thrust change value at each time step is: For the The change of ambient temperature in a time step.

[0090] Furthermore, based on the second equation, it is expressed as a matrix equation and an observation equation.

[0091] make , it can be expressed as the following matrix equation:

[0092]

[0093] in, is the state transfer matrix, It is the model error of the simulated noise, reflecting the impact of the modeling error on the results.

[0094] The observation equation can be expressed as

[0095]

[0096] in, is the change in measured strain and measured temperature, is the observation equation, It is the measurement noise, which reflects the impact of measurement error on the result.

[0097] The above two equations constitute the matrix equation and observation equation of the prediction-correction weighted recursive least squares estimation respectively. The recursive calculation process is as follows:

[0098] In the time step, complete the state one-step prediction, and get the The a priori estimate corresponding to the time step is as follows:

[0099]

[0100]

[0101] in, for In the The prior estimate of time steps is for In the The posterior estimate of time steps is for The estimated error covariance matrix is for The estimated error covariance matrix is is the model error The covariance matrix of .

[0102] Then, in the time steps, using the prior estimate Complete state estimation, the specific formula is:

[0103]

[0104]

[0105]

[0106]

[0107] in, is the gain matrix, is the deviation sequence between the measured signal and the prior estimate, To measure noise The covariance matrix of .

[0108] Push the time to The state prediction and state estimation are repeated for each time step to obtain new estimated variables. The shaft system thrust of the ship propeller shaft 1 is calculated based on the new estimated variables and the first equation. In the recursive calculation, it is necessary to estimate the covariance matrix caused by the modeling error and the covariance matrix caused by the measurement noise. However, in practical applications, these two matrices are not easy to determine and need to be adjusted according to the shaft system and the on-site environment. This embodiment provides a method for determining the covariance matrix With the covariance matrix The formula is:

[0109]

[0110]

[0111]

[0112] .

[0113] Figure 6 The strain and thrust identification effect of this method is as low as 20dB when the signal-to-noise ratio (SNR) is low, and the maximum relative error of thrust identification is only 4.8%.

[0114] See also Figures 1 to 4 This embodiment provides a high-precision real-time identification device for ship propeller shaft thrust, which is equipped with the high-precision real-time identification method for ship propeller shaft thrust of embodiment 1. It includes a mounting component 2 and a test piece. The mounting component 2 is used to be installed at a test point on the ship propeller shaft 1, and the test piece is attached to the mounting component 2.

[0115] See also Figure 1 and Figure 2 In the present embodiment, specifically, the mounting assembly 2 can be split into a first mounting member and a second mounting member for description. The first mounting member and the second mounting member have the same structure, and both include a first arc-shaped member, a second arc-shaped member and at least one connecting rod. The first arc-shaped member and the second arc-shaped member are both semicircular structures, and the two ends of the connecting rod are respectively connected to one side of the first arc-shaped member and one side of the second arc-shaped member. When there is only one connecting rod, the two ends of the connecting rod are respectively connected to the middle of the first arc-shaped member and the middle of the second arc-shaped member. When there are two connecting rods, the two ends of the connecting rod divide the first arc-shaped member and the second arc-shaped member into three sections, and the connection point is the division point of the three sections. The first arc-shaped member and the second arc-shaped member are symmetrically arranged, and the opening direction is exactly the same, that is, the second arc-shaped member can be obtained after the first arc-shaped member is translated.

[0116] At least one test piece is installed at the center of the connecting rod, and only one or more test pieces can be set. The use of multiple strain gauges 4 can eliminate the influence of random errors. Similarly, when there is only one connecting rod, one or more test pieces are correspondingly arranged on the connecting rod; when there are multiple connecting rods, one or more test pieces are correspondingly arranged on each connecting rod.

[0117] Both ends of the first arc-shaped member and the second arc-shaped member are provided with connection holes 3, and the opening direction of the connection holes 3 is perpendicular to the connecting rod. The first arc-shaped member of the first mounting member and the first arc-shaped member of the second mounting member are bolted together by passing bolts and nuts through the connection holes 3 of the two, and the second arc-shaped member is connected in the same way. Thus, the first mounting member and the second mounting member are connected to each other, thereby forming a ring-shaped mounting assembly 2, which is arranged around the propeller shaft 1 of the ship, such as Figure 3 shown.

[0118] In addition, see Figure 4 The test piece is a strain gauge 4, and two strain gauges 4 arranged opposite to each other are electrically connected, using a half-bridge connection to eliminate the influence of the bending deformation of the rotating shaft.

[0119] The embodiments of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above embodiments. Even if various changes are made to the present invention, if these changes fall within the scope of the claims of the present invention and their equivalents, they still fall within the protection scope of the present invention.

Claims

1. A high-precision real-time identification method for ship propeller shaft thrust, characterized in that: The steps include: Obtain strain signals of at least two strain gauges installed on the ship's propeller shaft, and the ambient temperature of the ship's propeller shaft; The first equation of the propeller shaft thrust and its longitudinal strain is constructed according to the strain signal and the ambient temperature: in, is the ship propeller shaft thrust, is the longitudinal strain, is the strain gauge reading, is the thermal expansion coefficient of the shaft system, is the initial ambient temperature, is the ambient temperature, and are the elastic modulus and cross-sectional area of ​​the shaft section where the strain gauge is installed; The second equation is obtained by differentiating the first equation and discretizing it by time step: in, For the The thrust change value at each time step is: For the The strain gauge readings at each time step are For the The strain gauge readings at each time step are For the The change value of ambient temperature in the time step; Based on the second equation, it is expressed as a matrix equation and an observation equation; The matrix equation is specifically: make , then the matrix equation is in, is the state transfer matrix, is the model error of the simulated noise; For the The change value of ambient temperature in the time step; The observation equation is specifically: in, is the change in measured strain and measured temperature, is the observation matrix, To measure noise; Based on the matrix equation and the observation equation, the state prediction is completed and the first The prior estimate corresponding to the time step , the calculation formula is: in, for In the The prior estimate of time steps, for In the The posterior estimate of time steps is for The estimated error covariance matrix is for The estimated error covariance matrix is is the model error The covariance matrix of Based on the a priori estimate Complete The state estimation at the time step is obtained The posterior estimate corresponding to the time step , the calculation formula is: in, is the gain matrix, For the The posterior estimate of time steps is, is the deviation sequence between the measured signal and the a priori estimate, To measure noise The covariance matrix of for The estimated error covariance matrix of ; Push the time to time step, repeat the state prediction and state estimation to get the Prior estimates at time steps and the posterior estimate , based on The shafting thrust of the ship's propeller shaft is calculated by using the corresponding prior estimates and a posteriori estimates and the first equation.

2. The method for high-precision real-time identification of ship propeller shaft thrust according to claim 1, characterized in that: Longitudinal strain The calculation of includes the following steps: Read the strain signals of different strain gauges respectively, and their values ​​satisfy the following formula: in, Strain gauge The strain generated, is the longitudinal strain caused by the thrust of the ship's propeller shaft, is the strain caused by the bending moment, is the thermal expansion coefficient of the shaft system, is the initial ambient temperature, is the ambient temperature; The readings of strain gauges connected to different strain gauges The formula is: 。 3. The method for high-precision real-time identification of ship propeller shaft thrust according to claim 1, characterized in that: The covariance matrix With the covariance matrix The formulas are: 。 4. The method for high-precision real-time identification of ship propeller shaft thrust according to any one of claims 1 to 3, characterized in that: Before obtaining the strain signals of at least two strain gauges installed on the ship propeller shaft and the ambient temperature of the ship propeller shaft, the following steps are also included: Select the measuring point on the propeller shaft of the ship and measure the shaft diameter at the measuring point to obtain the cross-sectional area. ; Arrange a mounting ring at the measuring point to stick two strain gauges, and check the sensitivity coefficient of the strain gauges; The two strain gauges are connected using a half-bridge connection.

5. A high-precision real-time identification device for ship propeller shaft thrust, equipped with a high-precision real-time identification method for ship propeller shaft thrust as claimed in claim 4, characterized in that: It includes a mounting assembly and a test piece; the mounting assembly is mounted at a test point on a propeller shaft of a ship; the test piece is attached to the mounting assembly; The mounting assembly includes a first mounting member and a second mounting member; The first mounting member and the second mounting member have the same structure, and both include a first arc-shaped member, a second arc-shaped member and at least one connecting rod; The first arc-shaped member and the second arc-shaped member are both semicircular, the two ends of the connecting rod are respectively connected to one side of the first arc-shaped member and one side of the second arc-shaped member, and the first arc-shaped member and the second arc-shaped member are symmetrically arranged; at least one test piece is installed on the connecting rod; Both ends of the first arc-shaped member and the second arc-shaped member are provided with connecting holes, the opening direction of the connecting holes is perpendicular to the connecting rod, and the first mounting member and the second mounting member cooperate with bolts and nuts through the connecting holes to achieve bolt connection.

6. The high-precision real-time identification device for ship propeller shaft thrust according to claim 5, characterized in that: The first mounting member and the second mounting member are each provided with two connecting rods; Both ends of the two connecting rods are respectively connected to one side of the first arc-shaped member and one side of the second arc-shaped member, and the connecting positions of the two connecting rods divide the first arc-shaped member or the second arc-shaped member into three arc sections; each connecting rod is provided with at least one test piece.

7. The high-precision real-time identification device for ship propeller shaft thrust according to claim 5 or 6, characterized in that: The test piece is a strain gauge, and two strain gauges arranged opposite to each other are electrically connected and adopt a half-bridge connection.

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