CN115560898A - Method and device for measuring axial thrust of ship propeller - Google Patents

Abstract

The invention discloses a method for measuring thrust of an axial line of a ship propeller. Obtaining two strain gage readings epsilon ₁ ,ε ₂ And two laser sensor readings d ₁ ,d ₂ (ii) a According to strain gauge reading epsilon ₁ ,ε ₂ Establishing propeller thrust F _T A first relational expression; according to laser sensor reading d ₁ ,d ₂ Establishing propeller thrust F _T A second relational expression; respectively deriving the first relational expression and the second relational expression, and dispersing according to time steps; converting the discrete relation into a Kalman filtering state transition equation, and constructing a Kalman filtering observation equation; and performing Kalman filtering based on a state transition equation and an observation equation to obtain the propeller axis thrust value after noise reduction. The invention not only utilizes the strain gauge to measure the strain of the shafting under the thrust, but also utilizes the laser displacement sensor to measure the deformation displacement of the rotating shaft, and fuses the measured strain and displacement data through Kalman filteringAnd the combined processing can effectively filter the thermal deformation interference caused by the measurement noise and the ambient temperature, improve the data processing precision and ensure that the thrust of the ship propeller can be measured on line and in real time.

Description

Method and device for measuring axial thrust of ship propeller

technical field

The invention belongs to the field of ship machinery and power, and in particular relates to a method and device for measuring the axial thrust of a ship propeller.

Background technique

After a long-term voyage, a large number of attachments will accumulate on the bottom of the ship, which will increase the navigation resistance and reduce the ship's navigation speed. At this time, it is necessary to accurately monitor the thrust of the ship's propeller, so as to provide guidance for the maintenance of the ship's dirty bottom and propeller according to the situation. In addition, online, real-time, and high-precision monitoring of propeller thrust can provide data support for navigation status monitoring, ship-engine-propeller optimization matching, and ship rapidity prediction. At present, the commonly used ship propeller thrust measurement methods include two categories. The first type is to arrange strain gauges on the shafting to obtain thrust by measuring the longitudinal strain of the shafting; the second is to arrange displacement sensors on the shafting. Propel the longitudinal displacement of the shafting to obtain thrust. The strain-based method has the advantages of high sensitivity and sensitivity to small thrusts, but has the disadvantages of zero drift, large temperature influence, and susceptibility to interference noise. The method based on displacement measurement has disadvantages such as low sensitivity and insensitivity to small thrusts, but the measurement data is stable, has no zero drift, and is less affected by interference noise. In a word, the advantages and disadvantages of the two types of measurement methods complement each other,

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

In the existing technology, a method for analyzing the stress state of the shaft of the hydro-generator is proposed. 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 , 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, and realize the purpose of directly evaluating the life and safety status of the rotating shaft from the on-site stress test results.

There is also proposed a model drive and thrust and torque testing system for an underwater pod or rudder propulsion device. 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.

In addition, a commercial vehicle thrust rod axial force testing device is proposed. 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.

In addition, a high-resolution angular displacement measuring device and method for micro-thrust measurement are proposed. The patent includes a laser displacement sensor, a bracket for installing and adjusting the height and horizontal position of the laser sensor, an Archimedes measuring block, and a data acquisition instrument for collecting and recording the output signal of the laser sensor. Thrust is monitored by measuring displacement.

Contents of the invention

The technical purpose of the present invention is to provide a method and device for measuring the axial thrust of a ship's propeller, so as to solve the defects of low measurement accuracy and inability to track thrust changes in real time in the propeller thrust measured by existing methods or measuring devices.

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

A method for measuring the axial thrust of a ship's propeller, comprising the steps of:

Obtain the readings ε ₁ , ε ₂ of the two strain gauges, and the readings d ₁ , d ₂ of the two laser sensors;

According to the readings ε ₁ and ε ₂ of the strain gauges, establish the first relational expression with the axial thrust _FT of the propeller;

According to the readings d ₁ and d ₂ of the laser sensor, the second relational expression with the propeller axial thrust _FT is established;

Deriving the first relational expression and the second relational expression respectively, and discretizing according to the time step to obtain the discrete relational expression;

The discrete relational expression is transformed into the state transition equation of the Kalman filter, and the observation equation of the Kalman filter is constructed. Based on the state transition equation and the observation equation, the Kalman filter is performed to obtain the thrust value of the propeller axis of the ship after noise reduction.

Specifically, the readings ε ₁ and ε ₂ of the two strain gauges satisfy the following formula

ε ₁ ＝ε _F -ε _M +α·(TT ₀ )

ε ₂ ＝ε _F +ε _M +α·(TT ₀ )

Among them, ε ₁ and ε ₂ are the strains generated by two strain gauges R ₁ and R ₂ attached to the axis of the propeller of the ship respectively, and the strain gauge R ₁ and R ₂ are installed oppositely on the axis of the propeller of the ship, ε _F is the strain caused by pure thrust, ε _M is the strain caused by pure bending moment, α is the thermal expansion coefficient of the shaft system, T ₀ is the initial temperature of the environment, and T is the ambient temperature during measurement;

The readings d ₁ and d ₂ of the two laser sensors satisfy the following formula

d ₁ ＝d _F -d _M +α·(L ₂ −L ₁ )·(TT ₀ )

d ₂ ＝d _F +d _M +α·(L ₂ −L ₁ )·(TT ₀ )

Wherein, L ₂ -L ₁ is the distance from the laser sensor to the corresponding sensing reflective block.

Among them, according to the readings ε ₁ and ε ₂ of the strain gauges, the first relational expression with the axial thrust _FT of the propeller is specifically expressed as

Based on the readings ε ₁ and ε ₂ of the strain gauge, the reading ε of the strain _gauge is obtained, and the calculation formula is:

_εmeter ＝ε ₁ +ε ₂ ＝2ε _F +2α·(TT ₀ )

Propeller axis thrust F _T and strain instrument reading ε _instrument satisfy the following formula

Among them, E is the elastic modulus of the shaft section at the measuring point where the strain gauge is located, and A is the sum of the cross-sectional area of the shaft section at the measuring point where the strain gauge is located and the cross-sectional area of the installation component where the strain gauge is installed.

Specifically, according to the readings d ₁ and d ₂ of the laser sensor, the second relational expression with the axial thrust _FT of the propeller is specifically:

计算公式为The average displacement is obtained based on the readings d ₁ , d ₂ of the two laser sensors

The calculation formula is

满足以下公式Propeller axis thrust F _T and average displacement

satisfy the following formula

Among them, L2 is the distance between the mounting components on _both sides of the strain gauge.

Among them, the first relational expression and the second relational expression are derived respectively, and the discrete relational expression is obtained by discretizing according to the time step, and the discrete relational expression is:

Among them, _εmeter (k+1) is the strain instrument reading at the k+1th time step, _εmeter (k) is the strain instrument 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.

Specifically, the state transition equation that transforms the discrete relational expression into Kalman filter is specifically:

则状态转移方程表示为如下：make

Then the state transition equation is expressed as follows:

X _k+1 ＝ΦX _k +w _k

Among them, w _k is the model noise, Φ is the state transition matrix;

The observation equation is expressed as:

y _k ＝H·X _k +v _k

Among them, y _k is the measured strain and measured temperature change, H is the observation matrix, and v _k is the measurement noise.

Among them, data fusion and completion of Kalman filtering based on the state transition equation and observation equation are as follows:

At the kth time step, the one-step prediction of the state is completed, and its calculation formula is:

P _k|k-1 ＝Φ·P _k-1|k-1 ·Φ ^T +Q

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，P_k|k-1为

的估计误差协方差矩阵，P_k-1|k-1为

的估计误差协方差矩阵，Q为模型噪声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, P _k|k-1 is

The estimated error covariance matrix of P _k-1|k-1 is

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

完成状态估计，其计算公式为：At the kth time step, use the prior estimate

The state estimation is completed, and its calculation formula is:

K _k ＝P _k|k-1 · ^HT ·(H·P _k|k-1 · ^HT +R) ^-1

P _k|k ＝(1-K _k ·H)·P _k|k-1

Among them, K _k is the Kalman filter gain, 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 the k+1th time step, and repeat the above steps.

A measuring device for the axial thrust of a ship's propeller, using any one of the methods for measuring the axial thrust of a ship's propeller, including

The installation component is ring-shaped and sleeved on the axis of the ship's propeller;

The strain gauge is provided with at least two strain gauges, and the adjacent strain gauges are fixed on the mounting assembly at the same angular interval,

The laser displacement sensor and the sensing reflective block are provided with at least two laser displacement sensors and two sensing reflective blocks. The connection line between the laser displacement sensor and the corresponding sensing reflective block is parallel to the axial direction of the propeller of the ship, and the adjacent laser displacement sensor They are fixed on the mounting assembly at the same angular interval, and the adjacent sensing reflective blocks are fixed on the mounting assembly at the same angular interval.

Specifically, the installation assembly includes two installation parts, and the two installation parts are connected by bolts, fixed on the propeller shaft of the ship, and locked with the propeller shaft of the ship;

The mounting part includes a first arc-shaped part, a second arc-shaped part, a first beam and a second beam;

The first arc-shaped piece and the second arc-shaped piece are located on both sides of the mounting piece, and the openings are set in the same direction;

Both ends of the first beam are respectively fixedly connected to the midpoints of the sides of the first arc-shaped member and the second arc-shaped member;

One end of the second beam is fixedly connected to the side of the first arc, the other end of the second beam is not fixedly connected to the side of the second arc, and the second beam and the first beam are arranged parallel to each other and are not connected.

Wherein, the strain gauge is fixed on the middle part of the first beam and is located on the outside;

The laser displacement sensor is fixed on the end of the second crossbeam close to the second arc-shaped part, and is located on the outside;

The sensing reflective block is fixed on the second arc part and is located on the outer arc surface of the second arc part.

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

The invention not only uses the strain gauge to measure the strain of the shafting under the thrust, but also uses the laser displacement sensor to measure the deformation displacement of the rotating shaft, and uses the Kalman filter method to fuse and process these measurement data and filter out the influence of measurement noise, thereby proposing a high-precision, A device for online and real-time measurement of ship propeller thrust and a noise reduction method.

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 flow chart of the measurement method of a kind of ship propeller axis thrust of the present invention;

Fig. 2 is the structural diagram of a kind of measuring device of ship propeller axis thrust of the present invention;

Fig. 3 is the installation, assembly drawing of a kind of measuring device of ship propeller axis thrust of the present invention;

Fig. 4 is the installation schematic diagram of laser displacement sensor and strain gauge of the present invention;

Fig. 5 is the result of thrust identification under different signal-to-noise ratios (SNR) by the method of the present invention.

Explanation of reference signs

1: The first arc; 2: The second arc; 3: The first beam; 4: The second beam; 5: Sensing reflective block; 6: Strain gauge; 7: Laser displacement sensor.

detailed description

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".

A method and device for measuring the axial thrust of a ship's propeller 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

Referring to Fig. 1 to Fig. 5, the present embodiment provides a method and device for measuring the axial thrust of a ship's propeller, which measures strain and displacement at the same time, and utilizes Kalman filtering to fuse and process the measurement data of the strain gauge 6 and the measurement data of the displacement sensor. The advantage of the high sensitivity of the strain gauge 6 also utilizes the advantage of the good stability of the displacement sensor. At the same time, the Kalman filter method is based on the state transition equation and measurement equation, which can perform minimum variance unbiased estimation on the data, has excellent noise reduction effect, and can further improve the propeller thrust measurement accuracy.

Referring to Figures 2 to 4, in this implementation, for the convenience of understanding and explanation, a device for measuring the axial thrust of a ship's propeller is described first. The device includes a mounting assembly, a strain gauge 6, a laser displacement sensor 7 and a sensing reflective block 5 .

The mounting assembly includes two mounting pieces, preferably two. The two installation parts are connected by bolts and nuts to form a ring structure, which is sleeved and fixed on the propeller shaft of the ship, so that the installation component and the propeller shaft of the ship are locked. Ensure that there is no relative slippage between the mounting assembly and the shaft section when the shaft is thrust. In addition, each part of the installation component needs to be processed with the same material as the rotating shaft, so as to ensure that the measuring device and the rotating shaft have the same coefficient of thermal expansion.

Subdivided, the installation part further includes a first arc-shaped part 1 , a second arc-shaped part 2 , and a first beam 3 and a second beam 4 . Wherein, the first arc-shaped piece 1 and the second arc-shaped piece 2 are located on both sides of the installation piece, and the openings are set in the same direction. When the installation parts are connected, the two ends of the first arc-shaped part 1 will be connected with the two ends of the first arc-shaped part 1 of another installation part, and the same is true for the second arc-shaped part 2 . Both ends of the first crossbeam 3 are fixedly connected to the midpoints of the sides of the first arc-shaped member 1 and the second arc-shaped member 2 respectively, specifically by welding. One end of the second beam 4 is fixedly connected to the side of the first arc-shaped member 1, and about a quarter of the connection is selected in the figure, and the other end of the second beam 4 is free, that is, it is not fixed to the side of the second arc-shaped member 2 connect. In terms of arrangement, the second beam 4 and the first beam 3 are arranged parallel to each other and are not connected together.

The strain gauges 6 are provided with at least two strain gauges 6, the number of the strain gauges 6 is set corresponding to the number of the first beam 3, and the adjacent strain gauges 6 are pasted on the middle part of the first beam 3 at the same angular interval , and facing outward. Taking two strain gauges 6 as an example, the two strain gauges 6 are arranged at intervals of 180°.

The laser displacement sensor 7 and the sensing reflective block 5 are provided with at least two laser displacement sensors 7 and two sensing reflective blocks 5 , and the number of the laser displacement sensor 7 and the sensing reflective block 5 corresponds to the number of the second beam 4 . The connection line between the laser displacement sensor 7 and the corresponding sensing reflective block 5 is arranged parallel to the axial direction of the ship propeller, and the adjacent laser displacement sensors 7 are fixed on the installation assembly at the same angular interval, and the adjacent sensing reflective blocks 5 are fixed on the mounting assembly at the same angular interval. It can be understood that, when two laser displacement sensors 7 are provided, the two laser displacement sensors 7 are arranged at an interval of 180°, and the sensing reflective block 5 is also arranged in the same way.

Specifically, the laser displacement sensor 7 is fixed to the free end of the second beam 4 by bolts, and is located on the outside, and the distance between the laser displacement sensor 7 and the second arc-shaped member 2 is related to its focal length. The sensing reflective block 5 is welded and fixed on the second arc-shaped member 2 and is located on the outer arc-shaped surface of the second arc-shaped member 2 .

Preferably, a plurality of strain gauges 6 can be arranged on the first beam 3, and the data of these strain gauges 6 can be averaged, thereby eliminating the influence of random errors. At the same time, a plurality of first beams 3 can be symmetrically designed in the measuring device, and one or more strain gauges 6 can be pasted on each first beam 3 . In addition, multiple second beams 4 can be symmetrically designed in the measuring device, and a laser displacement sensor 7 can be fixed on each beam. Finally, the laser displacement sensor 7 in this device can be replaced with other displacement sensors, such as eddy current displacement sensors and the like.

Referring to Fig. 4, when the two mounting parts are fastened on the rotating shaft by bolts, it is necessary to ensure that the angle between the two strain gauges 6 and the two laser displacement sensors 7 is 180 degrees, which can ensure that the two strain gauges 6 ( Or when the signals of two laser displacement sensors 7) are added, the influence of shafting bending can be eliminated. In addition, the entire test device also includes a slip ring fixed on the rotating shaft, a data acquisition system and a test computer. There are mature products on the market, so no detailed description will be given. The slip ring has two functions, one is to provide working voltage for the strain gauge 6 and the laser displacement sensor 7, the other is to transmit the strain signal and displacement signal to the data acquisition system, and finally the test data is transmitted to the test computer through the data acquisition system for processing.

In this embodiment, after the mounting assembly is installed on the rotating shaft, when the rotating shaft deforms under the thrust of the propeller, the two mounting parts will have a longitudinal relative displacement, which can be obtained from the distance between the laser displacement sensor 7 and the sensing reflective block 5 . At the same time, the first beam 3 between the two mounting parts will generate strain, which can be obtained by the strain gauge 6 on the first beam 3 . Through the fusion processing of displacement and strain measurement data, propeller thrust can be finally obtained.

Referring to FIG. 1 , this embodiment also provides a method for measuring the axial thrust of a ship's propeller using the above-mentioned device.

Before the measurement, first select a suitable measuring point position on the propulsion shafting, and measure the diameter of the shaft section at the measuring point. Process the measuring device shown in Figure 2 and Figure 3 according to the diameter of the shaft section, and the material used must be consistent with the shaft. Paste the strain gauge 6 on the first crossbeam 3 of the measuring device, and the two strain gauges 6 adopt the half-bridge line as shown in Figure 4 to eliminate the influence of the bending deformation of the rotating shaft, and check the sensitivity coefficient of the strain gauge 6 in the laboratory. A laser displacement sensor 7 is fixed on the second beam 4 . Fasten the measuring device to the shaft with a bolt-nut. Install the slip ring device on the rotating shaft, connect the data acquisition system, and debug the test system. Collect the strain and displacement signals, and transmit the data to the computer through the slip ring, and measure the ambient temperature change at the same time.

When the shafting is subjected to the joint action of propeller thrust and bending moment, the readings ε ₁ , ε ₂ of the two strain gauges 6 and the readings d ₁ , d ₂ of the two laser sensors are obtained.

Specifically, the readings ε ₁ and ε ₂ of the two strain gauges 6 satisfy the following formula

ε ₁ ＝ε _F -ε _M +α·(TT ₀ )

ε ₂ ＝ε _F +ε _M +α·(TT ₀ )

Among them, ε ₁ and ε ₂ are the strains generated by two strain gauges 6r ₁ and r ₂ attached to the axis of the propeller of the ship, respectively, and the strain gauge 6R ₁ and strain gage 6r ₂ are oppositely installed on the axis of the propeller of the ship, ε _F is the strain caused by pure thrust, ε _M is the strain caused by pure bending moment, α is the thermal expansion coefficient of the shaft system, T ₀ is the initial temperature of the environment, and T is the ambient temperature during measurement;

The readings d ₁ and d ₂ of the two laser sensors satisfy the following formula

d ₁ ＝d _F -d _M +α·(L ₂ −L ₁ )·(TT ₀ )

d ₂ ＝d _F +d _M +α·(L ₂ −L ₁ )·(TT ₀ )

Wherein, L ₂ is the distance between the first arc 1 and the second arc 2 , L ₁ is the length of the second beam 4 , and L ₂ −L ₁ is the distance from the laser sensor to the sensing reflective block 5 .

Then, according to the readings ε ₁ and ε ₂ of the strain gauge 6, the first relational expression with the axial thrust _FT of the propeller is specifically expressed as

First, based on the readings ε ₁ and ε ₂ of the strain gauge 6, the reading ε of the strain _gauge is obtained, and the calculation formula is:

_εmeter ＝ε ₁ +ε ₂ ＝2ε _F +2α·(TT ₀ )

The axial thrust F _T of the propeller and the strain gauge reading ε _gauge satisfy the following first relationship

Among them, E is the elastic modulus of the axial section at the measuring point where the strain gauge 6 is located (the strain gauge 6), and A is the cross-sectional area of the axial section at the measuring point where the strain gauge 6 is located and the installation component, that is, the section of the first beam 3 mentioned above. sum of areas. In the above formula, the influence of thermal deformation error caused by the change of ambient temperature is considered.

计算公式为Then, the average displacement is obtained based on the readings d ₁ , d ₂ of the two laser sensors

The calculation formula is

满足以下第二关系式Propeller axis thrust F _T and average displacement

Satisfy the following second relation

The above formula also takes into account the influence of thermal deformation errors caused by ambient temperature changes.

Next, derivate the first relational expression and the second relational expression respectively, and discretize according to the time step to obtain the discrete relational expression, the discrete relational expression is:

Among them, _εmeter (k+1) is the strain instrument reading at the k+1th time step, _εmeter (k) is the strain instrument 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.

则将离散关系式转换为状态转移方程，表示为如下：Furthermore, let the state vector

Then convert the discrete relational expression into a state transition equation, which is expressed as follows:

X _k+1 ＝ΦX _k +w _k

In the formula, w _k is the model noise, which reflects the influence of modeling errors on the results, and Φ is the state transition matrix;

The constructed observation equation is expressed as:

y _k ＝H·X _k +v _k

In the formula, y _k is the measured strain and measured temperature change, H is the observation matrix, and v _k is the measurement noise.

Based on the state transition equation and observation equation, the Kalman filtering process is as follows:

A1. At the kth time step, one-step prediction of the state is completed, and the calculation formula is:

P _k|k-1 ＝Φ·P _k-1|k-1 ·Φ ^T +Q

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，P_k|k-1为

的估计误差协方差矩阵，P_k-1|k-1为

的估计误差协方差矩阵，Q为模型噪声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, P _k|k-1 is

The estimated error covariance matrix of P _k-1|k-1 is

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

完成状态估计，其计算公式为：A2. At the kth time step, use a priori estimation

The state estimation is completed, and its calculation formula is:

k _k ＝P _k|k-1 · ^HT ·(H·P _k|k-1 · ^HT +R) ^-1

P _k|k ＝(1-K _k ·H)·P _k|k-1

Among them, K _k is the Kalman filter gain, 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 .

A3. Recursively advance the time to the k+1th time step, and repeat steps A1 and A2. In this way, the Kalman filter is implemented on the collected strain, displacement and temperature reading data, thereby improving the accuracy of propeller thrust identification. Since the state variable X _k+1 contains the thrust change value ΔF _T (k+1) at the k+1th time step, after obtaining the state variable X _k+1 at all time steps, the thrust change can be obtained from it The real-time change process of the value ΔF _T. Figure 5 is an example of thrust identification results under different signal-to-noise ratios (SNR) using the method of this embodiment.

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 (10)

1. a method for measuring ship propeller axis thrust, is characterized in that, comprises the steps: Obtain the readings ε ₁ , ε ₂ of the two strain gauges, and the readings d ₁ , d ₂ of the two laser sensors; According to the readings ε ₁ and ε ₂ of the strain gauges, establish the first relational expression with the propeller axial thrust _FT ; According to the readings d ₁ and d ₂ of the laser sensor, the second relational expression with the axial thrust _FT of the propeller is established; Deriving the first relational expression and the second relational expression respectively, and discretizing according to time steps to obtain the discrete relational expression; Converting the discrete relational expression into the state transition equation of the Kalman filter, and constructing the observation equation of the Kalman filter, performing the Kalman filter based on the state transition equation and the observation equation, so as to obtain the noise reduction of the ship propeller axis Thrust value. 2. the measuring method of ship propeller axis thrust according to claim 1, is characterized in that, the reading ε ₁ of two strain gauges, ε ₂ satisfies the following formula ε ₁ ＝ε _F -ε _M +α·(TT ₀ ) ε ₂ ＝ε _F +ε _M +α·(TT ₀ ) Among them, ε ₁ and ε ₂ are the strains generated by two strain gauges R ₁ and R ₂ attached to the axis of the ship propeller respectively, and the strain gauge R ₁ and the strain gauge R ₂ are installed opposite to the axis of the ship propeller ε _F is the strain caused by pure thrust, ε _M is the strain caused by pure bending moment, α is the thermal expansion coefficient of the shafting, T ₀ is the initial temperature of the environment, and T is the ambient temperature during measurement; The readings d ₁ and d ₂ of the two laser sensors satisfy the following formula d ₁ ＝d _F -d _M +α·(L ₂ −L ₁ )·(TT ₀ ) d ₂ ＝d _F +d _M +α·(L ₂ −L ₁ )·(TT ₀ ) Wherein, L ₂ -L ₁ is the distance from the laser sensor to the corresponding sensing reflective block. 3. the measuring method of ship's propeller axis thrust according to claim 2, is characterized in that, described reading ε ₁ according to strain gauge, ε ₂ establishes the first relational expression with propeller axis thrust _FT specifically as Based on the readings ε ₁ and ε ₂ of the strain gauge, the reading ε _meter of the strain gauge is obtained, and the calculation formula is: _εmeter ＝ε ₁ +ε ₂ ＝2ε _F +2α·(TT ₀ ) Propeller axis thrust F _T and strain instrument reading ε _instrument satisfy the following formula

Among them, E is the elastic modulus of the shaft section at the measuring point where the strain gauge is located, and A is the sum of the cross-sectional area of the shaft section at the measuring point where the strain gauge is located and the cross-sectional area of the installation component where the strain gauge is installed. 4. The measuring method of ship propeller axis thrust according to claim 2, characterized in that, according to the readings d ₁ of the laser sensor, d ₂ establishes the second relational expression with the propeller axis thrust _FT specifically as follows: The average displacement is obtained based on the readings d ₁ , d ₂ of the two laser sensors

The calculation formula is

Propeller axis thrust F _T and average displacement

satisfy the following formula

Among them, L2 is the distance between the mounting components on _both sides of the strain gauge. 5. according to the measuring method of ship propeller axis thrust described in claim 3 and 4, it is characterized in that, described respectively to described first relational expression and described second relational expression derivation, and obtain discretization by time step discretization Relational expression, the discrete relational expression is:

Among them, _εmeter (k+1) is the strain instrument reading at the k+1th time step, _εmeter (k) is the strain instrument 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. 6. the measuring method of ship's propeller axis thrust according to claim 5, is characterized in that, described discrete relational expression is converted into the state transition equation of Kalman filter specifically as: make

Then the state transition equation is expressed as follows: X _k+1 ＝ΦX _k +w _k Among them, w _k is the model noise, Φ is the state transition matrix;

The observation equation is expressed as: y _k ＝H·X _k +v _k Among them, y _k is the measured strain and measured temperature change, H is the observation matrix, and v _k is the measurement noise. 7. The method for measuring the thrust of the ship's propeller axis according to claim 6, wherein said data fusion is carried out based on said state transition equation and said observation equation and Kalman filtering is completed, specifically: At the kth time step, the one-step prediction of the state is completed, and its calculation formula is:

P _k|k-1 ＝Φ·P _k-1|k-1 ·Φ ^T +Q in,

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

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

The estimated error covariance matrix of P _k-1|k-1 is

The estimated error covariance matrix of Q is the covariance matrix of the model noise w _k ; At the kth time step, use the prior estimate

The state estimation is completed, and its calculation formula is: K _k ＝P _k|k-1 · ^HT ·(H·P _k|k-1 · ^HT +R) ^-1

P _k|k ＝(1-K _k ·H)·P _k|k-1 Among them, K _k is the Kalman filter gain, 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 the k+1th time step, and repeat the above steps. 8. A measuring device for the thrust of the ship's propeller axis, using the method for measuring the thrust of the ship's propeller axis as claimed in any one of claims 1 to 7, characterized in that it comprises The installation component is ring-shaped and sleeved on the axis of the ship's propeller; Strain gauges are provided with at least two strain gauges, and adjacent strain gauges are fixed on the mounting assembly at the same angular interval, The laser displacement sensor and the sensing reflective block are provided with at least two said laser displacement sensors and two said sensing reflective blocks. Parallel, the adjacent laser displacement sensors are fixed on the installation assembly at the same angular interval, and the adjacent sensing reflective blocks are fixed on the installation assembly at the same angular interval. 9. The measuring device of ship propeller axis thrust according to claim 8, characterized in that, The installation assembly includes two installation parts, and the two installation parts are connected by bolts, fixed on the propeller shaft of the ship, and locked with the propeller shaft of the ship; The mounting part includes a first arc, a second arc, and a first crossbeam and a second crossbeam; The first arc-shaped piece and the second arc-shaped piece are located on both sides of the mounting piece, and the openings are facing the same direction; The two ends of the first beam are respectively fixedly connected to the midpoints of the sides of the first arc-shaped member and the second arc-shaped member; One end of the second beam is fixedly connected to the side of the first arc, the other end of the second beam is not fixedly connected to the side of the second arc, and the second beam is connected to the side of the first arc. The first beams are arranged parallel to each other and are not connected. 10. The device for measuring the thrust of the propeller axis of a ship according to claim 9, wherein the strain gauge is fixed to the middle of the first beam and is located on the outside; The laser displacement sensor is fixed on one end of the second crossbeam close to the second arc, and is located on the outside; The sensing reflective block is fixed on the second arc-shaped member and is located on the outer arc-shaped surface of the second arc-shaped member.

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