Fast calculation method and system for temperature change of brake shoe based on digital twin

Abstract

The present invention discloses a method and system for quickly calculating the temperature change of a brake shoe based on digital twin. In this application, real-time side temperature data of the brake shoe and historical side temperature data of the brake shoe are obtained; the historical side temperature data of the brake shoe is input into the constructed discretized brake shoe heat conduction model; the discretized brake shoe heat conduction model is used to calculate the temperature on the contact surface affecting the temperature of the side through heat conduction; simulation is performed based on the side temperature data in the historical data to calculate the contact surface temperature and calculate the temperature mapping matrix K; when solving the minimization objective function E(K), the corresponding optimal temperature mapping matrix K is obtained. The optimal temperature mapping matrix K obtained is used for reverse solution to calculate the contact surface temperature of the brake shoe in the digital twin corresponding to the real-time collected side temperature data of the brake shoe. By using digital twin technology, a small amount of data is measured by an indirect sensor to deduce the temperature change result, and the discretized brake shoe heat conduction model is used to realize the mapping of the temperature state of the traction machine brake shoe.

Description

Technical Field

[0001] The present invention relates to the technical field of elevator digital twins, and particularly to a method and system for quickly calculating the temperature change of a brake shoe based on digital twins. Background Art

[0002] With the rapid development of China's economic construction, high-rise buildings have been built rapidly. Elevators have become an indispensable facility in people's daily production and life. Digital twin technology integrates multiple physics, multiple disciplines, and multiple scales, and has the characteristics of ultra-realism, real-time synchronization, all elements, and uniqueness. It can realize the interactive integration of the physical world and the information world, thereby reflecting the entire life cycle process of the corresponding physical equipment. Therefore, by effectively integrating digital twins with key elevator components, the reliability, accuracy, and safety of elevators during their entire life cycle operation can be improved. Currently, the technical difficulties in installing sensors on brake shoes are high installation costs and incomplete coverage of local areas. Digital twin technology provides the ability to map the virtual and real of the brake, but how to efficiently use limited measurement data to deduce global results is the current technical bottleneck.

[0003] This paper conducts specific research on the brake shoes of key elevator components. Currently, the health monitoring of brake shoes depends on offline experimental data or high-complexity finite element simulations, and it is difficult to achieve real-time calculation and global temperature change field calculation. Therefore, a method for quickly calculating temperature change is needed to deduce the global temperature change result by measuring a small amount of data with an indirect sensor, thereby constructing a fast temperature change calculation model to realize the mapping relationship of the health state of the traction machine brake shoes. Summary of the Invention

[0004] Therefore, the purpose of the present invention is to provide a method for quickly calculating the temperature change of a brake shoe based on digital twins. By using digital twin technology, a small amount of data is measured with an indirect sensor to deduce the temperature change result, and a discretized brake shoe heat conduction model is constructed to realize the mapping of the temperature state of the traction machine brake shoes.

[0005] To achieve the above purpose, a method for quickly calculating the temperature change of a brake shoe based on digital twins of the present invention includes the following steps:

[0006] Obtain real-time side temperature data of the brake shoe and historical side temperature data of the brake shoe;

[0007] Input the historical side temperature data of the brake shoe into the constructed discretized brake shoe heat conduction model; use the discretized brake shoe heat conduction model to calculate the temperature on the contact surface affecting the temperature of the side through heat conduction;

[0008] Perform simulation based on the side temperature data in the historical data, calculate the contact surface temperature, and calculate the temperature mapping matrix ;

[0009] Solve the minimization of the objective function The corresponding optimal temperature mapping matrix .

[0010] Using the obtained optimal temperature mapping matrix Solve backward to calculate the contact surface temperature of the brake shoe in the digital twin corresponding to the temperature data of the brake shoe side surface collected in real time.

[0011] Further preferably, when constructing the discretized brake shoe heat conduction model, it includes constructing a discrete contact model of the brake shoe according to the following steps:

[0012] Define the contact area of the brake shoe as an approximate two-dimensional rectangular area, and the grid discretization size is ( , ) is the length of the brake shoe, is the thickness of the brake shoe;

[0013] Discretize the contact surface of the brake shoe and divide it into points through grid division; then, the grid step size is , ;

[0014] Further preferably, based on the discrete contact model of the brake shoe, construct a heat conduction model of the brake shoe according to the heat conduction characteristics of the brake shoe;

[0015] Define as the temperature at the th point in the grid; starting from the contact surface, when heat diffuses along the contact surface, the following two-dimensional heat conduction equation is satisfied:

[0016]

[0017] Where: are the density, specific heat capacity, and thermal conductivity of the material respectively; is the heat generated by friction, which depends on the frictional force and the relative sliding speed ; is the spatial diffusion term of the temperature on the contact surface;

[0018] Discretize the partial differential equation of to obtain the discrete equation of each grid point on the contact surface;

[0019] Construct a heat conduction model of the brake shoe according to the explicit finite difference method:

[0020] .

[0021] Further preferably, when discretizing the partial differential equation of , the following steps are adopted:

[0022] First, discretize the time derivative of the brake shoe temperature:

[0023] ; where: represents the temperature at the grid point at the n-th time step; is the time step.

[0024] Secondly, discretize the spatial derivative of the brake shoe temperature, and perform central differencing on the spatial derivatives and :

[0025] ;

[0026] ;

[0027] where: is the temperature at the grid points and at the n-th time step;

[0028] Further preferably, when constructing the heat conduction model of the brake shoe according to the explicit finite difference method, it includes:

[0029] Simplify the contact surface of the brake shoe into a two-dimensional rectangular region, update the brake shoe temperature through the discretized heat conduction equation, and substitute the discrete forms of the time derivative and the spatial derivative into the heat conduction equation based on the explicit finite difference method:

[0030]

[0031] For the rectangular region: the temperature of the brake shoe contact surface is defined on , and the temperature distribution is ; the temperature of the brake shoe side surface is defined on , and the temperature distribution is .

[0032] Further preferably, when simulating according to the side surface temperature data in the historical data, calculating the contact surface temperature, and calculating the temperature mapping matrix , the following steps are included;

[0033] S301. Initialize the temperature field, and set the initial contact surface temperature and side surface temperature;

[0034] S302. Use the explicit finite difference method to iteratively calculate the temperature on the contact surface and the influence of the heat conduction on the side surface temperature;

[0035] S303. Establish the mapping matrix according to the simulation results, ; where They are the vectorized forms of the side and contact surface temperatures, respectively; is a matrix of, representing the contact surface temperature matrix, which represents the temperature values of each grid point on the contact surface in all simulations: , where each column is the contact surface temperature vector obtained from the i-th simulation; the side temperature matrix is a matrix of, representing the temperature values of each grid point on the side in all simulations: , where each column is the side temperature vector obtained from the i-th simulation.

[0036] S304. By minimizing the error objective function , the optimal mapping matrix K is obtained.

[0037] Further preferably, in S304, the optimal mapping matrix K is obtained by minimizing the error objective function through the following steps:

[0038] The objective function is used to characterize the error between the side temperature of the model and the actual side temperature;

[0039]

[0040] Taking the derivative of with respect to K and setting the derivative equal to 0, we get:

[0041]

[0042] After simplification, we obtain: .

[0043] The present invention also provides a fast calculation system for the temperature change of the brake shoe based on digital twin. Based on the above fast calculation method for the temperature change of the brake shoe based on digital twin, the fast calculation of the temperature change of the brake shoe is carried out in the digital twin brake; it includes:

[0044] A data acquisition module for acquiring real-time brake shoe side temperature data and historical brake shoe side temperature data;

[0045] A discretized brake shoe heat conduction model for inputting the historical brake shoe side temperature data; using the discretized brake shoe heat conduction model, calculating the temperature on the contact surface affects the temperature on the side through heat conduction;

[0046] A simulation module for simulating according to the side temperature data in the historical data, calculating the contact surface temperature, and calculating the temperature mapping matrix ; solving the minimum objective function to obtain the corresponding optimal temperature mapping matrix .

[0047] Contact surface temperature calculation module, using the obtained optimal temperature mapping matrix Perform reverse solution to calculate the contact surface temperature of the brake shoe in the digital twin corresponding to the temperature data of the side of the brake shoe collected in real time.

[0048] The present invention also provides an electronic device, including:

[0049] A memory storing computer program instructions;

[0050] A processor, when the computer program instructions are executed by the processor, implementing the steps of the above-mentioned method for quickly calculating the temperature change of the brake shoe based on digital twin.

[0051] The present invention also provides a computer-readable storage medium, which is used to store instructions. When the stored instructions run on a computer, the computer is enabled to execute the steps of the above-mentioned method for quickly calculating the temperature change of the brake shoe based on digital twin.

[0052] The method and system for quickly calculating the temperature change of the brake shoe based on digital twin disclosed in this application deduce the global temperature change result by measuring a small amount of data through an indirect sensor, thereby constructing a fast temperature change calculation model to realize the mapping relationship of the health state of the traction machine brake shoe.

[0053] The present invention realizes the accurate inverse deduction of the contact surface temperature by combining historical and real-time data and using the discretized brake shoe heat conduction model and the optimization method of minimizing the objective function. Through the optimization of the temperature mapping matrix, the temperature change under different working conditions can be quickly calculated, significantly improving the accuracy and calculation efficiency of temperature prediction and avoiding the high cost and low efficiency problems in traditional methods. The system can adapt to complex working condition changes and accurately reflect the temperature state of the brake shoe.

[0054] Secondly, using digital twin technology, a brake shoe model in a virtual environment is established. By collecting a small amount of data through sensors and combining the digital twin model and calculation method to deduce the contact surface temperature, the number of sensors is reduced, and the hardware cost and installation difficulty are lowered. By not requiring multiple sensors to be arranged on the contact surface, the system not only simplifies the maintenance work but also greatly improves the reliability of the equipment. Description of the Drawings

[0055] Figure 1 It is a flowchart of the method for quickly calculating the temperature change of the brake shoe based on digital twin of the present invention. Detailed Embodiments

[0056] The present invention will be further described in detail below with reference to the drawings and specific embodiments.

[0057] Since the contact surfaces of the brake shoe and the brake wheel are in complete contact, it is impossible to directly arrange sensors on the brake shoe assembly for monitoring. Considering that during the braking process of the brake shoe, heat will be generated due to the friction between the brake shoe and the brake wheel, resulting in a local temperature rise of the brake shoe. Therefore, the indirect stress inversion method based on machine vision in this application is used to monitor the temperature distribution on the side of the brake shoe in real time.

[0058] As Figure 1 shown, the method for quickly calculating the temperature change of the brake shoe of a brake based on digital twin provided by an embodiment of the present invention on the one hand includes the following steps:

[0059] S1. Obtain real-time brake shoe side temperature data and historical brake shoe side temperature data; First, monitor the temperature field of the brake shoe, install a high-resolution online thermal imaging camera on the side of the traction machine brake shoe, and the acquisition range is -20°C to 650°C; Based on the infrared imaging method, the temperature distribution on the side of the brake shoe is monitored in real time.

[0060] First, collect the temperature data values of multiple key points on the side of the brake shoe , and analyze the rate of change of temperature with the braking time , so as to map the temperature data to the temperature change distribution of the contact surface.

[0061] S2. Input the historical brake shoe side temperature data into the constructed discretized brake shoe heat conduction model; Use the discretized brake shoe heat conduction model to calculate the influence of the temperature on the contact surface on the side temperature through heat conduction;

[0062] Among them, when constructing the discretized brake shoe heat conduction model, a brake shoe contact model is constructed based on the real-time dynamic data of the brake shoe and its surrounding related components collected. The brake shoe contact model includes a discrete contact model of the brake shoe constructed according to the contact characteristics of the brake shoe and a heat conduction model of the brake shoe constructed according to the heat conduction characteristics of the brake shoe;

[0063] Among them, when constructing the discrete contact model of the brake shoe, it is first necessary to define the geometric characteristics of the brake shoe: that is, define the contact area of the brake shoe as an approximate two-dimensional rectangular area (the contact surface is ), and the grid discretization size is:

[0064] is the length of the brake shoe (along the x direction); is the thickness of the brake shoe (along the y direction);

[0065] Subsequently, the contact surface of the brake shoe is discretized and divided into points through grid division; Then, the grid step size is , ;

[0066] When establishing the heat conduction model of the brake shoe, first define as the Temperature of the point;

[0067] On the contact surface between the brake shoe and the brake wheel, the frictional heat generation between the two is the main heat source, and the heat diffuses along the contact surface, satisfying the two-dimensional heat conduction equation:

[0068]

[0069] Where: Is the spatial diffusion term of the temperature on the contact surface;

[0070] Is the heat generated by friction, which depends on the frictional force And the relative sliding speed ;

[0071] Are the density, specific heat capacity, and thermal conductivity of the material, respectively.

[0072] Discretize the Partial differential equation to obtain the discrete equation for each grid point on the contact surface;

[0073] The specific discretization process is as follows:

[0074] First, discretize the time derivative of the brake shoe temperature:

[0075] Where: Represents the temperature of the grid point At the nth time step; Is the time step.

[0076] 2. Secondly, discretize the spatial derivative of the brake shoe temperature, and perform central differencing on the spatial derivatives And : ; .

[0077] Where: Is the temperature of the grid points And At the nth time step;

[0078] Construct the discrete heat conduction equation according to the explicit finite difference method:

[0079]

[0080] Where the heat diffusion term describes the diffusion of heat in the brake shoe along the x and y directions, which is determined by the temperatures of the surrounding grid points and the material thermal conductivity k; the heat source term describes the phenomenon of local temperature rise in the brake shoe caused by contact friction or other heat sources.

[0081] The contact surface of the brake shoe is simplified to a two-dimensional rectangular area, and the update of the brake shoe temperature is realized through the discretized heat conduction equation. Based on the explicit finite difference method, the discrete forms of the time derivative and the space derivative are substituted into the heat conduction equation:

[0082]

[0083] For the rectangular area: The temperature of the brake shoe contact surface is defined on , and the temperature distribution is ; The temperature of the brake shoe side surface is defined on , and the temperature distribution is .

[0084] S3. Perform simulation according to the side surface temperature data in the historical data, calculate the contact surface temperature, and calculate the temperature mapping matrix ;

[0085] Mapping relationship of the brake shoe: Since the heat conduction in the brake shoe is a diffusion process, the heat on the contact surface will be transferred along the material to the side surface. Using the discretized heat conduction equation, the mapping matrix can be generated by simulating the temperature change of the contact surface to express the influence relationship of the contact surface temperature on the side surface temperature:

[0086] The mapping matrix is a matrix, where is the number of side surface grid points, is the number of contact surface grid points; Each row of the matrix corresponds to the temperature of the side surface grid points, and each column corresponds to the influence of the contact surface grid point temperature on the side surface temperature.

[0087] By recursively calculating the grid points through the heat conduction equation, the process of heat conduction from the contact surface to the side surface can gradually update the temperature field of the entire region.

[0088] To inversely deduce the side surface temperature from the contact surface temperature obtained through multiple simulations, it is necessary to calculate the influence of the contact surface temperature on the side surface temperature through numerical simulation or analytical methods. The following steps can be taken:

[0089] The first step is to initialize the temperature field and set the initial contact surface temperature and side surface temperature;

[0090] The second step is to calculate heat conduction, and use the explicit finite difference method to iteratively calculate the temperature on the contact surface to affect the temperature of the side surface through heat conduction.

[0091] The third step is to construct the mapping relationship: Establish the mapping matrix according to the simulation results, ;

[0092] Where They are the vectorized forms of the side surface temperature and the contact surface temperature respectively.

[0093] Set N simulations. Each simulation solution has a contact surface temperature field and a side surface temperature field. Specifically:

[0094] Contact surface temperature matrix is a matrix, representing the temperature values of each grid point on the contact surface in all simulations: , and each column is the contact surface temperature vector obtained from the i-th simulation.

[0095] Side surface temperature matrix is a matrix, representing the temperature values of each grid point on the side surface in all simulations: , and each column is the side surface temperature vector obtained from the i-th simulation.

[0096] S4. Solve the minimized objective function When, the corresponding optimal temperature mapping matrix .

[0097] According to the relationship between the contact surface temperature and the side surface temperature, solve the mapping matrix , , by minimizing the error objective function , obtain the optimal mapping matrix.

[0098] Objective function measures the error between the side surface temperature of the model and the actual side surface temperature. It can be expressed as: ;

[0099] To simplify the solution, combine all simulation results into a matrix form: is ; is matrix.

[0100] Therefore, this objective function can be written as: , where represents the Frobenius norm (the square root of the sum of the squares of the elements of the matrix), that is:

[0101]

[0102] Solve the minimized objective function. To minimize , take the derivative of and set it to zero:

[0103]

[0104] After simplification, we get:

[0105] Wherein: is a square matrix representing the covariance matrix of the contact surface temperature, and its inverse matrix is used to stably solve the mapping matrix .

[0106] S5. Using the obtained optimal temperature mapping matrix to perform reverse solution and calculate the contact surface temperature of the brake shoe in the digital twin corresponding to the real-time collected side temperature data of the brake shoe.

[0107] When the side temperature is measured, the contact surface temperature is inversely deduced through an optimization method: that is, the measured value corresponds to a column vector, and the contact surface temperature is inversely solved ;

[0108] Wherein: is a square matrix representing the covariance matrix of the mapping matrix; is its inverse matrix to stably reverse-deduce the contact surface temperature; combines the relationship between the side temperature data and the mapping matrix to obtain the optimal solution of the contact surface temperature.

[0109] The present invention also provides a rapid calculation system for the temperature change of a brake shoe based on digital twin, which performs rapid calculation of the temperature change of the brake shoe in the digital twin brake based on the above-mentioned rapid calculation method for the temperature change of the brake shoe based on digital twin; including:

[0110] A data acquisition module for acquiring real-time side temperature data of the brake shoe and historical side temperature data of the brake shoe;

[0111] A discretized brake shoe heat conduction model for inputting the historical side temperature data of the brake shoe; using the discretized brake shoe heat conduction model, calculating the temperature on the contact surface affects the side temperature through heat conduction;

[0112] A simulation module for simulating according to the side temperature data in the historical data, calculating the contact surface temperature, and calculating the temperature mapping matrix ; solving the minimum objective function to obtain the corresponding optimal temperature mapping matrix .

[0113] A contact surface temperature calculation module for using the obtained optimal temperature mapping matrix to perform reverse solution and calculate the contact surface temperature of the brake shoe in the digital twin corresponding to the real-time collected side temperature data of the brake shoe.

[0114] The present invention can be applied to an electronic device, including:

[0115] A memory that stores computer program instructions;

[0116] A processor that, when the computer program instructions are executed by the processor, implements the steps of the method for quickly calculating the temperature change of the brake shoe based on digital twin as described above.

[0117] The present invention also provides a computer-readable storage medium, which is used to store instructions. When the stored instructions run on a computer, the computer is caused to execute the steps of the method for quickly calculating the temperature change of the brake shoe based on digital twin as described above.

[0118] Obviously, the above embodiments are only examples for clear illustration and are not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation manners here. And the obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A fast calculation method for brake shoe temperature change based on digital twin, characterized in that: The following steps are involved: Obtain real-time brake shoe side temperature data and historical brake shoe side temperature data; Inputting the historical brake shoe side temperature data into the constructed discretized brake shoe heat conduction model; using the discretized brake shoe heat conduction model, calculating how the temperature on the contact surface affects the temperature of the side through heat conduction; Simulate the side temperature data in the historical data, calculate the contact surface temperature, and calculate the temperature mapping matrix ;include: S301, initializing the temperature field, setting the initial contact surface temperature and the side surface temperature; S302, using an explicit finite difference method to iteratively calculate how the temperature on the contact surface affects the temperature on the side surface through heat conduction; S303, establishing a mapping matrix according to the simulation results , ;in , are the vectorized forms of the side and contact surface temperatures, respectively; for The matrix represents the contact surface temperature matrix, which represents the temperature values ​​of each grid point on the contact surface in all simulations: , each column is the contact surface temperature vector obtained from the i-th simulation; the side temperature matrix for , which represents the temperature values ​​of each grid point on the side in all simulations: , each column is the side temperature vector obtained from the i-th simulation; S304, by minimizing the error objective function , find the optimal mapping matrix K, Solve to minimize the objective function When the corresponding optimal temperature mapping matrix ; comprising the following steps: Using the objective function Characterizes the error between the side temperature of the model and the actual side temperature; Will right Take the derivative and set it equal to 0. After simplification, we get: ; The optimal temperature mapping matrix obtained Reverse solution is performed to calculate the contact surface temperature of the brake shoe in the digital twin corresponding to the real-time collected brake shoe side temperature data.

2. The method for rapid calculation of brake shoe temperature change based on digital twin according to claim 1 is characterized in that: The construction of the discretized brake shoe heat conduction model includes constructing a discrete contact model of the brake shoe according to the following steps: The contact area of ​​the brake shoe is defined as a two-dimensional rectangular area, and the mesh discretization size is ( , ) is the brake shoe length, is the brake shoe thickness; Discretize the contact surface of the brake shoe and divide it into points; then, the grid step size is , .

3. The method for rapid calculation of brake shoe temperature change based on digital twin according to claim 2 is characterized in that: Based on the brake shoe discrete contact model, a brake shoe heat conduction model is constructed according to the heat conduction characteristics of the brake shoe; definition For the grid The temperature of the point; starting from the contact surface, when the heat diffuses along the contact surface, the following two-dimensional heat conduction equation is satisfied: in: are the density, specific heat capacity and thermal conductivity of the material respectively; Heat generated by friction, depends on the friction force and relative sliding speed ; is the spatial diffusion term of the temperature on the contact surface; Will The partial differential equation is discretized to obtain the discrete equation for each grid point on the contact surface; The heat conduction model of the brake shoe is constructed according to the explicit finite difference method: , To represent the nth time step, the grid point The temperature, To indicate the At time steps, the grid points temperature.

4. The method for rapid calculation of brake shoe temperature change based on digital twin according to claim 3 is characterized in that: In the When discretizing the partial differential equation, the following steps are taken: First, the time derivative of the brake shoe temperature is discretized: ;in: To represent the nth time step, the grid point Temperature; is the time step; Indicates At time steps, the grid points Temperature; Secondly, the spatial derivative of the brake shoe temperature is discretized and the spatial derivative is and Perform central difference: ； ； in: , When it is the 𝑛th time step, the grid point and temperature.

5. The method for rapid calculation of brake shoe temperature change based on digital twin according to claim 3 is characterized in that: The heat conduction model of the brake shoe is constructed according to the explicit finite difference method, including: The contact surface of the brake shoe is simplified into a two-dimensional rectangular area, and the brake shoe temperature is updated through the discretized heat conduction equation. The discrete forms of the time derivative and space derivative are substituted into the heat conduction equation based on the explicit finite difference method: For rectangular areas: The brake shoe contact surface temperature is defined as , the temperature distribution is ; Brake shoe side temperature is defined as , the temperature distribution is ; When it is the 𝑛th time step, the grid point Friction generates heat.

6. A brake shoe temperature change rapid calculation system based on digital twin, characterized in that: Based on the method for rapid calculation of brake shoe temperature change based on digital twin according to any one of claims 1 to 5 above, rapid calculation of brake shoe temperature change is performed in the digital twin brake; comprising: A data acquisition module, which acquires real-time brake shoe side temperature data and historical brake shoe side temperature data; A discretized brake shoe heat conduction model is used to input the historical brake shoe side temperature data; using the discretized brake shoe heat conduction model, calculate how the temperature on the contact surface affects the temperature of the side through heat conduction; The simulation module simulates the side temperature data in the historical data, calculates the contact surface temperature, and calculates the temperature mapping matrix ; Solve to minimize the objective function When the corresponding optimal temperature mapping matrix ; Contact surface temperature calculation module, using the optimal temperature mapping matrix Reverse solution is performed to calculate the contact surface temperature of the brake shoe in the digital twin corresponding to the real-time collected brake shoe side temperature data.

7. An electronic device, characterized in that: include: a memory storing computer program instructions; A processor, when the computer program instructions are executed by the processor, implements the steps of the method for quickly calculating the temperature change of brake shoes based on digital twins as described in any one of claims 1 to 5.

8. A computer-readable storage medium, characterized in that: The computer-readable storage medium is used to store instructions. When the stored instructions are executed on a computer, the computer executes the steps of the method for rapid calculation of brake shoe temperature change based on digital twins as claimed in any one of claims 1 to 5.

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