CN115636063A - High-precision real-time identification method and device for thrust of ship propeller shaft - Google Patents

Abstract

The invention discloses a method and device for high-precision real-time identification of propeller shaft thrust of a ship, comprising the following steps: processing a measuring device and installing it on a rotating shaft; Formula; deriving the first equation and discretizing it according to time to obtain the second equation, based on the second equation, the system matrix equation and observation equation are obtained; based on the matrix equation, the thrust state prediction of the kth time step is completed, and the thrust state is completed based on the observation equation State estimation: recursively advance the time to the k+1th time step, repeat the state prediction and state estimation, and finally obtain the thrust dynamic process. The invention has strong anti-interference ability, can compensate thermal deformation error caused by ambient temperature change, and can maintain high measurement accuracy in strong interference noise. In addition, in the present invention, the strain gauge is pasted on the measuring device, and the sensitivity coefficient of the strain gauge can be calibrated in the laboratory, thereby eliminating the influence of external factors such as the sticking method of the strain gauge and the type of glue.

Description

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

technical field

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

Background technique

Online, real-time, and accurate monitoring of the thrust of the ship's propulsion system at various speeds can provide accurate data requirements for rapid ship prediction, navigation status monitoring, ship-engine-propeller optimization matching, etc., which is of great engineering significance. However, the current technical bottleneck is that it is difficult to monitor the propeller thrust accurately and in real time under the interference environment of the real ship. Noise such as noise and shafting vibration is submerged, and it is difficult to identify weak thrust signals from the measured deformation signals.

At present, some patents have proposed patents related to thrust testing, including methods and devices.

Method category: a method for analyzing the stress state of the shaft of a hydroelectric generator. 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 calculations; S3. Arrange strain gauges on the shaft to test the axial stress of the shaft; S4 1. Apply boundary conditions in the finite model to make the calculated stress equal to the test stress; S5. By analyzing the calculation results of the finite element calculation model and the on-site stress test results, establish the relationship between the maximum stress value of the rotating shaft and the on-site stress test value, The purpose of directly evaluating the life and safety state of the rotating shaft from the results of the field stress test is realized.

Device category: underwater pod or rudder propulsion device model drive and thrust and torque test system. The patent includes a drive module, a measurement module and a transmission module. The driving module adopts a DC motor, the rotating shaft of the motor is connected to the measuring module, and the other end of the measuring module is connected to the propeller. Strain gauges on the measurement module measure the strain induced by the thrust. The transmission module transmits the signal and the input voltage of the strain gauge through non-contact coupling.

Commercial vehicle thrust rod axial force test device. The patent includes thrust rods, strain gauges, and data acquisition instruments. Among them, the thrust rod and the strain gauge are fixedly installed, and the strain gauge is fixedly installed on the surface of the thrust rod parallel to the axis of the thrust rod through the adhesive layer; the strain gauge is electrically connected to the data acquisition instrument; the data acquisition instrument collects the data of the strain gauge.

However, the above-mentioned patents all have the main defect of low anti-interference ability, and the technical problem of low test accuracy in the environment of temperature changes and strong interference noise.

Contents of the invention

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

In order to solve the above problems, the technical solution of the present invention is:

A high-precision real-time identification method for ship propeller shaft thrust, comprising the following steps:

Obtain 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;

Construct the first equation of the propeller shaft thrust and its longitudinal strain according to the strain signal and the ambient temperature; derivate the first equation and discretize it according to time steps to obtain the second equation; based on the second equation, express it as a matrix equation and observation equation;

The state prediction is completed based on the matrix equation and the observation equation, and the prior estimation corresponding to the k-th time step is obtained; the state estimation at the k-th time step is completed based on the prior estimation, and the estimated variable corresponding to the k-th time step is obtained; Recurse the time to k+1 time steps, repeat the state prediction and state estimation, so as to obtain new estimated variables, and calculate the shafting thrust of the ship propeller shaft based on the new estimated variables and the first equation.

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

Read the strain signals of different strain gauges respectively, and the magnitudes satisfy the following formula:

ε ₁ =ε _F -ε _M +a·(TT ₀ ); ε ₂ =ε _F +ε _M +a·(TT ₀ )

Among them, ε ₁ and ε ₂ are the strains produced by the strain gauges R ₁ and R ₂ respectively, ε _F is the longitudinal strain produced by the shaft thrust of the propeller of the ship, ε _M is the strain produced by the bending moment, a is the coefficient of thermal expansion of the shaft system, T ₀ is the initial temperature of the environment, T is the ambient temperature;

The formula of the reading ε _meter of the strain gauge connected with different strain gauges is:

_εmeter ＝ε ₁ +ε ₂ ＝2ε _F +2a·(TT ₀ )

The relationship between ship propeller shaft thrust F _T and longitudinal strain ε _F satisfies the following first equation:

Among them, E and A are the elastic modulus and cross-sectional area of the shaft section where the strain gauge is installed, respectively.

Among them, deriving the first equation and discretizing it according to time steps to obtain the second equation, the specific formula is:

Among them, _εmeter (k+1) is the strain gauge reading at the k+1th time step, _εmeter (k) is the strain gauge reading at the kth time step, and ΔF _T (k) is the kth time The change value of the thrust at the next step, ΔT(k) is the change value of the ambient temperature at the kth time step.

Among them, based on the second equation, it is expressed as a matrix equation, specifically as

Let X _k+1 ＝[ε_直(k+1)ΔF _T (k)ΔT(k+1)] ^T , then the matrix equation is

X _k+1 ＝Φ·X _k +w _k

为状态转移矩阵，w_k为模拟噪声的模型误差；in,

is the state transition matrix, w _k is the model error of the simulated noise;

Based on the second equation, the observation equation is expressed as

y _k ＝H·X _k +v _k

为观测方程，v_k为测量噪声。where _yk is the change in measured strain versus measured temperature,

is the observation equation, and v _k is the measurement noise.

Among them, at the kth time step, the prior estimate corresponding to the kth time step is specifically:

为X在第k个时间步的先验估计，

为X在第k-1个时间步的后验估计，

为

的估计误差协方差矩阵，

为

的估计误差协方差矩阵，Q为模型误差w_k的协方差矩阵；in,

is the prior estimate of X at the kth time step,

is the posterior estimate of X at the k-1th time step,

for

The estimated error covariance matrix of ,

for

The estimated error covariance matrix of , Q is the covariance matrix of the model error w _k ;

At the kth time step, the estimated variables corresponding to the kth time step are specifically:

K _k ＝P _k|k-1 H ^T (HP _k|k-1 H ^T +R) ^-1

P _k|k ＝(1-K _k H)P _k|k-1

Among them, K _k is the gain matrix, Z _k is the deviation sequence between the measurement signal and the prior estimate, and R is the covariance matrix of the measurement noise v _k ;

The formulas of covariance matrix Q and covariance matrix R are respectively:

R＝C _k -HP _k|k-1 H ^T

Further preferably, the following steps are also included before obtaining the strain signals of at least 2 strain gauges installed on the ship's propeller shaft and the ambient temperature of the ship's propeller shaft

Select the position of the measuring point on the propeller shaft of the ship, and measure the diameter of the shaft section at the measuring point to obtain the cross-sectional area A;

Arrange the mounting ring at the measuring point to paste 2 strain gauges, and check the sensitivity coefficient of the strain gauges;

The two strain gauges are connected by a half-bridge connection.

A high-precision real-time identification device for ship propeller shaft thrust, configured with the above-mentioned high-precision real-time identification method for ship propeller shaft thrust,

Including installation components and test pieces; the installation components are installed at the test points on the propeller shaft of the ship; the test pieces are attached to the installation components;

The mounting assembly includes a first mounting part and a second mounting part;

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

Both the first arc and the second arc are semicircular, and the two ends of the connecting rod are respectively connected to one side of the first arc and one side of the second arc, and the first arc and the second The arc parts are arranged symmetrically; at least one test piece is installed on the connecting rod;

Both ends of the first arc-shaped piece and the second arc-shaped piece are provided with connecting holes, and the opening direction of the connecting holes is perpendicular to the connecting rod. The first mounting part and the second mounting part cooperate with bolts and nuts through the connecting holes to realize bolt connection .

Specifically, both the first mounting part and the second mounting part are provided with two connecting rods;

And both ends of the two connecting rods are respectively connected to one side of the first arc-shaped piece and one side of the second arc-shaped piece, and the connecting positions of the two connecting rods divide the first arc-shaped piece or the second arc-shaped piece Three arcs; each connecting rod is provided with at least one test piece.

Wherein, the test piece is a strain gauge, and two oppositely arranged strain gauges are electrically connected by using a half-bridge connection.

Compared with the prior art, the present invention has the following advantages and positive effects due to the adoption of the above technical scheme:

On the one hand, the present invention adopts the weighted recursive least square estimation of estimation-correction to identify the propeller thrust from the strain signal with noise interference, which has strong anti-interference ability and can still maintain a high level in the environment of strong interference noise. measurement accuracy. On the other hand, the functional relationship between ambient temperature and thermal deformation is established in the recurrence equation, so that the thermal deformation error caused by temperature can be compensated during the variable recurrence process. Finally, the strain gauge of the present invention is pasted on the installation assembly, and the sensitivity coefficient of the pasted strain gauge can be calibrated and checked in the laboratory, thereby eliminating the influence of external factors such as the pasting method of the strain gauge and the type of glue. The two strain gauges adopt half-bridge connection, which can eliminate the influence of the bending deformation of the shaft. The strain gauges directly transmit the data to the computer through slip rings or wireless transmission for subsequent processing.

Description of drawings

Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiment. The drawings are only for the purpose of illustrating a preferred embodiment and are not to be considered as limiting the invention.

Fig. 1 is the structural diagram of mounting assembly of the present invention;

Fig. 2 is a structural diagram of another embodiment of the mounting assembly of the present invention;

Fig. 3 is the structural diagram of the ship propeller shaft thrust high-precision real-time identification device of the present invention;

Fig. 4 is the schematic diagram of strain gauge half-bridge wiring of the present invention;

Fig. 5 is a kind of ship propeller shaft thrust high-precision real-time identification method of the present invention;

Fig. 6 is a comparative diagram of strain and thrust identification effects of the present invention.

Explanation of reference signs

1: Ship propeller shaft; 2: Mounting component; 3: Connection hole; 4: Strain gauge.

Detailed ways

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the specific implementation manners of the present invention will be described below with reference to the accompanying drawings. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention, and those skilled in the art can obtain other accompanying drawings based on these drawings and obtain other implementations.

In order to make the drawing concise, each drawing only schematically shows the parts related to the present invention, and they do not represent the actual structure of the product. In addition, to make the drawings concise and easy to understand, in some drawings, only one of the components having the same structure or function is schematically shown, or only one of them is marked. Herein, "a" not only means "only one", but also means "more than one".

The method and device for high-precision real-time identification of the propeller shaft 1 thrust of a ship proposed by the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. Advantages and features of the present invention will be apparent from the following description and claims.

Example 1

Referring to FIG. 5 , this embodiment provides a high-precision real-time identification method for the propeller shaft 1 thrust of a ship. Before implementing this embodiment, it is necessary to select a measuring point on the propeller shaft 1 of the ship. Usually, the measuring point is selected near the propeller shaft 1 of the ship, and the diameter of the shaft section at the measuring point is measured to obtain the cross-sectional area A.

According to the diameter of the shaft section of the propeller shaft 1 of the ship, install a mounting ring at the position of the measuring point, as shown in Fig. 1 and Fig. 2 . Referring to FIGS. 2 to 4 , at least two strain gauges 4 are pasted on the mounting ring, and the two strain gauges 4 are installed on both sides of the mounting ring respectively, that is, oppositely arranged. After the installation is completed, check the sensitivity coefficient of the strain gauge 4 in the laboratory (the installation ring has not been installed on the propeller shaft 1 of the ship when checking). The mounting ring is secured to the shaft with bolt-nuts, as shown in Figure 3. The two strain gauges 4 on the mounting ring are connected by a half-bridge connection, so as to eliminate the influence of bending deformation caused by the bending of the rotating shaft, and the preparatory stage is completed so far.

Referring to FIG. 5 , in this embodiment, first, the strain signals of at least two strain gauges 4 installed on the propeller shaft 1 of the ship and the ambient temperature of the propeller shaft 1 of the ship need to be acquired. Then the first equation of the thrust of the propeller shaft 1 of the ship and its longitudinal strain is constructed according to the strain signal and the ambient temperature.

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

ε ₁ =ε _F -ε _M +a·(TT ₀ ); ε ₂ =ε _F +ε _M +a·(TT ₀ )

Among them, ε ₁ and ε ₂ are the strains produced by the strain gauges 4R ₁ and R ₂ respectively, ε _F is the longitudinal strain produced by the thrust of the propeller shaft 1 of the ship, ε _M is the strain produced by the bending moment, a is the thermal expansion coefficient of the shaft system, T ₀ is the initial temperature of the environment, and T is the ambient temperature.

The strain gauges are electrically connected to different strain gauges 4 respectively, and the readings of the ε _gauges meet:

_εmeter =ε ₁ +ε ₂ =2ε _F +2a·(TT ₀ ).

Thus, the relationship between the thrust _{FT of the propeller shaft 1 of the ship and the longitudinal strain ε F satisfies} the following first equation:

Wherein, E and A are respectively the elastic modulus and cross-sectional area of the axial section where the strain gauge 4 is installed.

Then, deriving the first equation and discretizing it according to time steps to obtain the second equation, the specific formula is:

Among them, _εmeter (k+1) is the strain gauge reading at the k+1th time step, _εmeter (k) is the strain gauge reading at the kth time step, and ΔF _T (k) is the kth time The change value of the thrust at the next step, ΔT(k) is the change value of the ambient temperature at the kth time step.

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

Let X _k+1 ＝[ε_直(k+1)ΔF _T (k)ΔT(k+1)] ^T , it can be expressed as the following matrix equation:

X _k+1 ＝Φ·X _k +w _k

为状态转移矩阵，w_k为模拟噪声的模型误差，反映建模误差对结果影响。in,

is the state transition matrix, w _k is the model error of the simulated noise, reflecting the influence of the modeling error on the result.

The observation equation can be expressed as

y _k ＝H·X _k +v _k

为观测方程，v_k为测量噪声，反映测量误差对结果影响。where _yk is the change in measured strain versus measured temperature,

is the observation equation, and v _k is the measurement noise, which reflects the influence of measurement errors on the results.

The above two equations compose the state equation and the observation equation of the predictor-correction weighted recursive least squares estimation respectively. The recursive calculation process is as follows:

At the kth time step, the one-step prediction of the state is completed, and the prior estimate corresponding to the kth time step is obtained. The specific formula is:

为X在第k个时间步的先验估计，

为X在第k-1个时间步的后验估计，

为

的估计误差协方差矩阵，

为

的估计误差协方差矩阵，Q为模型误差w_k的协方差矩阵。in,

is the prior estimate of X at the kth time step,

is the posterior estimate of X at the k-1th time step,

for

The estimated error covariance matrix of ,

for

The estimated error covariance matrix of Q is the covariance matrix of the model error w _k .

完成状态估计，具体公式为：Then, at the kth time step, use the prior estimate

Complete the state estimation, the specific formula is:

K _k ＝P _k|k-1 H ^T (HP _k|k-1 H ^T +R) ^-1

P _k|k ＝(1-K _k H)P _k|k-1

Among them, K _k is the gain matrix, Z _k is the deviation sequence between the measurement signal and the prior estimate, and R is the covariance matrix of the measurement noise v _k .

Recurse the time to k+1 time steps, repeat the state prediction and state estimation, so as to obtain new estimated variables, and calculate the shafting thrust of ship propeller shaft 1 based on the new estimated variables and the first equation. In the recursive calculation, the covariance matrix caused by modeling error and the covariance matrix caused by measurement noise need to be estimated. However, in practical applications, these two matrices are not easy to determine and need to be adjusted according to the shafting and site environment. This embodiment provides a formula that can determine the covariance matrix Q and the covariance matrix R, specifically:

R＝C _k -HP _k|k-1 H ^T

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

Example 2

Referring to FIGS. 1 to 4 , this embodiment provides a device for high-precision real-time identification of 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 the mounting assembly 2 and the test piece. The installation assembly 2 is used to be installed at the test point on the propeller shaft 1 of the ship, and the test piece is attached to the installation assembly 2 .

Referring to FIG. 1 and FIG. 2 , in this embodiment, specifically, the mounting assembly 2 can be divided into a first mounting part and a second mounting part for description. The first mounting part and the second mounting part have the same structure, and both include a first arc-shaped part, a second arc-shaped part and at least one connecting rod. Both the first arc-shaped piece and the second arc-shaped piece have a semicircular structure, and the two ends of the connecting rod are respectively connected to one side of the first arc-shaped piece and one side of the second arc-shaped piece. When there is only one connecting rod, the two ends of the connecting rod are respectively connected with the middle of the first arc-shaped piece and the middle of the second arc-shaped piece; when there are two connecting rods, the two ends of the connecting rod connect the first arc-shaped piece and the second arc are divided into three sections, and the connection point is the division of the three sections. The first arc-shaped part and the second arc-shaped part are arranged symmetrically, and the openings have the same orientation, that is, the second arc-shaped part can be obtained after the first arc-shaped part is translated.

At least one test piece is installed in the center of the connecting rod, and there may be only one or more than one test piece, and the use of multiple strain gauges 4 can eliminate the influence of random errors. Similarly, when there is one connecting rod, one or more test pieces are correspondingly provided on the connecting rod; when multiple connecting rods are provided, one or more test pieces are correspondingly provided on each connecting rod. pieces.

Both ends of the first arc-shaped piece and the second arc-shaped piece are provided with connecting holes 3, and the opening direction of the connecting holes 3 is perpendicular to the connecting rod. The first arc-shaped part of the first mounting part and the first arc-shaped part of the second mounting part pass through the connection holes 3 of the two through bolts and nuts, so as to realize bolt connection, and the same is true for the second arc-shaped part. In this way, the first mounting part and the second mounting part are connected to each other, thereby forming a ring-shaped mounting assembly 2, which is fitted around the propeller shaft 1 of the ship, as shown in FIG. 3 .

In addition, referring to Fig. 4, the test piece is a strain gauge 4, and two opposite strain gauges 4 are electrically connected, and a half-bridge line is used to eliminate the influence of the bending deformation of the rotating shaft.

The embodiments of the present invention have been described in detail above with reference to 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 equivalent technologies, they still fall within the protection scope of the present invention.

Claims (9)

1. A high-precision real-time identification method for thrust of a ship propeller shaft is characterized by comprising the following steps:

acquiring strain signals of at least 2 strain gauges arranged on a propeller shaft of a ship and the ambient temperature of the propeller shaft of the ship;

constructing a first equation of the thrust of the propeller shaft of the ship and the longitudinal strain of the propeller shaft of the ship according to the strain signal and the environment temperature; carrying out derivation on the first equation and dispersing the first equation according to time steps to obtain a second equation; expressing into a matrix equation and an observation equation based on the second equation;

state prediction is completed based on the matrix equation and the observation equation, and prior estimation corresponding to the kth time step is obtained; completing state estimation at the kth time step based on the prior estimation to obtain an estimation variable corresponding to the kth time step; and (4) recursion is carried out on the time to k +1 time steps, state prediction and state estimation are repeated, so that a new estimation variable is obtained, and shafting thrust of the ship propeller shaft is obtained through calculation based on the new estimation variable and the first equation.

2. The method for identifying the thrust force of the ship propeller shaft in high precision in real time according to claim 1, wherein the specific steps of constructing the first equation of the thrust force of the ship propeller shaft and the longitudinal strain of the ship propeller shaft according to the strain signal and the environment temperature comprise

Respectively reading the strain signals of different strain gauges, wherein the degree of the strain signals satisfies the following formula:

ε ₁ ＝ε _F -ε _M +a·(T-T ₀ )；ε ₂ ＝ε _F +ε _M +a·(T-T ₀ )

wherein epsilon ₁ 、ε ₂ Are respectively strain gauges R ₁ 、R ₂ Strain generated, epsilon _F Longitudinal strain, epsilon, generated by thrust of propeller shaft of ship _M A is the coefficient of thermal expansion of the shafting, T ₀ Is an ambient initial temperature, T is the ambient temperature;

readings epsilon of strain gauges respectively connected with different strain gauges _{Instrument for measuring the shape of a human body} The formula of (1) is:

ε _{instrument for measuring the shape of a human body} ＝ε ₁ +ε ₂ ＝2ε _F +2a·(T-T ₀ )

Propeller shaft thrust F of ship _T With longitudinal strain epsilon _F The relationship satisfies the first equation:

wherein E and A are respectively the elastic modulus and the sectional area of the shaft section at the mounting position of the strain gauge.

3. The method for identifying the thrust of the propeller shaft of the ship in real time with high precision as claimed in claim 2, wherein the first equation is derived and dispersed in time steps to obtain a second equation, and the specific formula is as follows:

wherein epsilon _{Instrument for measuring the shape of a human body} (k + 1) is the strain gauge reading at time step k +1, ε _{Instrument for measuring the shape of a human body} (k) For strain gauge readings at the kth time step, Δ F _T (k) The thrust variation value at the kth time step is shown, and Δ T (k) is the ambient temperature variation value at the kth time step.

4. The method for high-precision real-time identification of thrust of a propeller shaft of a marine vessel as claimed in claim 3, wherein said expression into a matrix equation based on said second equation is specifically

Let X _k+1 ＝[ε _{Instrument for measuring the shape of a human body} (k+1)ΔF _T (k) ΔT(k+1)] ^T Then the matrix equation is

X _k+1 ＝Φ·X _k +w _k

Wherein,

is a state transition matrix, wk isSimulating a model error of the noise;

expressing an observation equation based on the second equation specifically is

y _k ＝H·X _k +v _k

Wherein, y _k For changes in measured strain and measured temperature,

to observe the equation, v _k To measure noise.

5. The method for identifying the thrust of the propeller shaft of the ship in high precision in real time according to claim 4, wherein at the kth time step, the obtaining of the prior estimate corresponding to the kth time step specifically comprises:

wherein,

for the a priori estimate of X at the kth time step,

for the a posteriori estimate of X at the k-1 time step,

is composed of

The covariance matrix of the estimated error of (a),

is composed of

Q is the model error w _k The covariance matrix of (a);

at the kth time step, the obtaining of the estimated variable corresponding to the kth time step specifically includes:

K _k ＝P _k|k-1 H ^T (HP _k|k-1 H ^T +R) ^-1

P _k|k ＝(1-K _k H)P _k|k-1

wherein, K _k Is a gain matrix, Z _k For a sequence of deviations of the measurement signal from said a priori estimate, R is the measurement noise v _k The covariance matrix of (a);

the covariance matrix Q and the covariance matrix R have the respective formulae:

R＝C _k -HP _k|k-1 H ^T

6. the method for identifying the thrust of the propeller shaft of the ship in real time according to any one of claims 1 to 5, wherein the method further comprises the following steps before acquiring the strain signals of at least 2 strain gauges installed on the propeller shaft of the ship and the ambient temperature of the propeller shaft of the ship

Selecting a measuring point position on a propeller shaft of the ship, and measuring the diameter of a shaft section at the measuring point position to obtain the sectional area A;

arranging a mounting ring at the measuring point position to paste 2 strain gauges and checking the sensitivity coefficient of the strain gauge;

and connecting the two strain gauges by adopting a half-bridge connection line mode.

7. A high-precision real-time identification device for the thrust of a ship propeller shaft, which is configured with the high-precision real-time identification method for the thrust of the ship propeller shaft as claimed in claims 1 to 6,

the device comprises a mounting assembly and a test piece; the mounting assembly is mounted at a test point on a propeller shaft of the ship; the test piece is attached to the mounting assembly;

the mounting assembly comprises a first mount and a second mount;

the first mounting part and the second mounting part are same in structure and respectively comprise a first arc-shaped part, a second arc-shaped part and at least one connecting rod;

the first arc-shaped part and the second arc-shaped part are both semicircular, two ends of the connecting rod are respectively connected with one side of the first arc-shaped part and one side of the second arc-shaped part, and the first arc-shaped part and the second arc-shaped part are symmetrically arranged; at least one test piece is arranged on the connecting rod;

the two ends of the first arc-shaped part and the second arc-shaped part are provided with connecting holes, the opening directions of the connecting holes are perpendicular to the connecting rod, and the first mounting part and the second mounting part are matched with a bolt and a nut through the connecting holes to realize bolt connection.

8. The device for identifying the thrust of the propeller shaft of the ship in real time according to claim 7, wherein the first mounting piece and the second mounting piece are provided with two connecting rods;

two ends of the two connecting rods are respectively connected with one side of the first arc-shaped part and one side of the second arc-shaped part, and the connecting positions of the two connecting rods divide the first arc-shaped part or the second arc-shaped part into three sections of arcs; each connecting rod is provided with at least one test piece.

9. The device for identifying the thrust of the propeller shaft of the ship in real time according to claim 7 or 8, wherein the test piece is a strain gauge, and the two strain gauges arranged oppositely are electrically connected and adopt a half-bridge connection.

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