Vibration characteristics analysis method of direct-drive dual-axis turntable based on finite element analysis software

Abstract

The present invention discloses a vibration characteristic analysis method of a direct-drive dual-axis turntable based on finite element analysis software. By analyzing the heat transfer process of the direct-drive dual-axis turntable and the heat exchange type between the turntable surface and the air, the convective heat transfer coefficient between each key part and the air is determined according to the turntable structure. The contact surface of the oil film and the turntable is set as a coupling surface in the finite element analysis software solver to reflect the heat transfer between the oil and the turntable. At the same time, the heat exchange coefficient of the turntable surface is corrected using the test analysis results, thereby improving the accuracy of the numerical analysis results of the thermal characteristics of the direct-drive dual-axis turntable. The thermal deformation of the turntable and the thermal characteristics of the oil film are analyzed to obtain the vibration characteristics of the direct-drive dual-axis turntable, including the vibration frequency, the main vibration mode and the corresponding critical speed. The present invention is simple to operate, fast, efficient and low in cost, greatly saves the analysis time of the vibration characteristics of the direct-drive dual-axis turntable, and has great guiding significance for the structural design and optimization of the direct-drive dual-axis turntable.

Description

Technical Field

[0001] The invention relates to a vibration characteristic analysis method of a direct-drive dual-axis turntable, in particular to a vibration characteristic analysis method of a direct-drive dual-axis turntable based on finite element analysis software. Background Art

[0002] The dual-axis rotary table is a key component of the five-axis linkage CNC machine tool, and its characteristics affect the performance of the whole machine. With the demand for intelligent, high-precision, and high-dynamic response of CNC machine tools, the direct-drive dual-axis rotary table has become a must-have key functional component for multi-axis machine tools. In the development and optimization process of the direct-drive dual-axis rotary table, it is necessary to analyze its vibration characteristics, so as to optimize the structure and select accessories to shorten the development cycle and ensure the performance of the rotary table.

[0003] The existing method for analyzing the vibration characteristics of a direct-drive dual-axis turntable is to use instruments for detecting temperature and deformation to directly measure the temperature field and vibration deformation field of key parts of a machine tool under various operating conditions, and analyze and summarize the influence and laws of various factors on the temperature field and vibration deformation field of a direct-drive dual-axis turntable based on the measurement results. The analysis process is not only time-consuming and labor-intensive, but also costly, and the analysis results are inaccurate.

[0004] Finite element analysis software is a software that uses mathematical approximation methods to simulate real physical systems (including geometric structures and load conditions). This type of software uses simple but interactive units, that is, a finite number of unknown quantities are used to approximate real systems with infinite unknown quantities, thereby gaining a deep understanding of complex systems and structures. It can be used for analysis in multiple fields such as structure, heat, fluid, and electromagnetics. However, at present, due to the relative independence of the processors of each module of this type of software, there is no simple and direct analysis method for complex structures such as direct-drive dual-axis turntables. Summary of the invention

[0005] The present invention aims to solve the above problems existing in the prior art and provides a vibration characteristic analysis method of a direct-drive dual-axis turntable based on finite element analysis software.

[0006] The technical solution of the present invention is: a vibration characteristic analysis method of a direct-drive dual-axis turntable based on finite element analysis software, which is carried out in the following steps:

[0007] Step 1. Create a 3D model of the direct-drive dual-axis turntable and perform preprocessing

[0008] Step 1.1 Establish a three-dimensional model of the direct-drive dual-axis turntable according to the structural design scheme of the direct-drive dual-axis turntable;

[0009] Step 1.2: Remove small and medium-sized accessories, chamfers with a side length of less than or equal to 5 mm, and fillets with a radius of less than or equal to 5 mm in the three-dimensional model of the direct-drive dual-axis turntable, and process the interference fit structure and the fixed joint surface using a shared topology method;

[0010] Step 2. Solve the thermal load of the cooling pipe of the direct-drive dual-axis turntable

[0011] Step 2.1 Use 3D software to extract the fluid equivalent 3D model of the cooling oil circuit of the direct-drive dual-axis turntable, input it into the fluid pre-processing module of the finite element analysis software, and mesh the fluid equivalent 3D model;

[0012] Step 2.2 Determine the coolant volume flow rate and flow rate

[0013] According to the torque motor selection, the rated power is obtained respectively P , power loss , cooling oil specific heat , cooling oil inlet and outlet temperature , get the cooling oil volume flow and flow rate as follows:

[0014] , flow rate , A is the cross-sectional area of ​​the cooling oil channel;

[0015] Step 2.3 Determine the convection heat transfer coefficient between the motor stator and the cooling oil channel

[0016] Determine the convection heat transfer coefficient between the motor stator and the cooling oil channel according to the following formula: ;

[0017] In the formula is the Nusselt number, is the thermal conductivity of the cooling oil, D is the cooling pipe diameter;

[0018] Said , where is the Reynolds number, is the Plandall dimension, L is the geometric characteristic length of the cooling channel;

[0019] Reynolds number , is the kinematic viscosity of the cooling oil, is the cooling oil density;

[0020] Planck dimension ;

[0021] Step 2.4 Determine the torque motor rotor heat transfer coefficient ;

[0022] ;in is the rotor speed;

[0023] Step 2.5: Set each port according to the cooling oil circuit distribution of the direct-drive dual-axis turntable, and set the inlet to pressure inlet or velocity inlet, and the outlet to pressure outlet;

[0024] Step 2.6 In the FLUID FLOW module of the finite element analysis software, set the surface of the direct-drive dual-axis turntable in contact with the air to the convection heat transfer type, and input the inlet temperature, ambient temperature and the results obtained in 2.1-2.5 according to the actual working conditions of the direct-drive dual-axis turntable, set the contact surface between the cooling pipeline oil circuit of the direct-drive dual-axis turntable and the cradle casting as the coupling surface, and use the SIMPLE algorithm to solve the thermal load of the cooling oil circuit;

[0025] Step 3. Solve the deformation field of the direct-drive dual-axis turntable under thermal influence

[0026] Step 3.1 Assign materials to each part according to the direct-drive dual-axis turntable structure, divide all parts with hexahedral structured grids, refine the grids for the coupling surface positions by virtual surface cutting methods, and divide the cross-sectional gradient changes of all part structures into at least 3 layers;

[0027] Step 3.2: Input the density, Poisson's ratio and mass of the main components of the direct-drive dual-axis turntable, wherein the main components are the pneumatic clamp, the worktable, the torque motor, the protective cover, the circular grating, the turntable bearing, the C-axis cradle casting and the A-axis fixing seat;

[0028] Step 3.3 applies the heat load calculated in step 2 to the cooling pipe of the direct drive dual shaft;

[0029] Step 3.4 Apply the gravity load and cutting force load of the part to be processed to the C-axis worktable surface, constrain the outer cylindrical end surface of the A-axis fixed seat, and constrain the bolt holes with a diameter greater than 10 mm in an equivalent spring manner;

[0030] The equivalent spring fixed constraint is to couple the boundary circle of the upper section of the bolt hole to the center position A, and the boundary circle of the lower section of the bolt hole to the center position B, add a spring connection between the two points AB, input the spring stiffness value, and set the fixed constraint of the two points AB;

[0031] Step 3.5 Input the gravity acceleration of 9.8m / s on the overall structure of the direct-drive dual-axis turntable 2 ;

[0032] Step 3.6 Use the DIRECT algorithm of the static structural module of the finite element analysis software to solve the deformation field of the direct-drive dual-axis turntable under the influence of heat;

[0033] Step 3.7: Evaluate the correctness of the deformation field according to the accuracy requirements of the direct-drive dual-axis turntable. If the accuracy requirements are met, proceed to step 4; otherwise, proceed to step 3.8.

[0034] Step 3.8: Determine whether any major components are missing. If yes, return to step 1; otherwise, return to step 2.

[0035] Step 4. Vibration characteristics analysis of direct-drive dual-axis turntable

[0036] Step 4.1 Input the deformation field of the direct-drive dual-axis turntable under the influence of heat obtained in step 3 into the modal module of the finite element analysis software, set the frequency analysis step, set the vibration frequency order to 10, use the Lanczos iteration method to solve the extreme eigenvalues ​​of the matrix, and obtain the first 10 vibration frequencies and main vibration modes;

[0037] Each critical speed RPM is equal to the corresponding natural frequency HZ multiplied by 60;

[0038] Step 4.2 Evaluate the vibration characteristics of the direct-drive dual-axis turntable

[0039] Compare each critical speed with the maximum operating speed of the direct-drive dual-axis turntable. If the two are not equal, the vibration characteristics of the direct-drive dual-axis turntable are excellent, otherwise, the vibration characteristics are poor.

[0040] The present invention analyzes the heat transfer process of the direct-drive dual-axis turntable and the type of heat exchange between the turntable surface and the air, determines the convective heat transfer coefficient between each key part and the air according to the turntable structure, sets the contact surface between the oil film and the turntable as a coupling surface in the finite element analysis software solver to reflect the heat transfer between the oil and the turntable; at the same time, the heat exchange coefficient of the turntable surface is corrected using the test analysis results, thereby improving the accuracy of the numerical analysis results of the thermal characteristics of the direct-drive dual-axis turntable. The present invention uses the finite element analysis software to establish a structured model of the thermo-solid coupling between the oil film and the turntable, analyzes the thermal deformation of the turntable and the thermal characteristics of the oil film, sets the frequency analysis step, and uses the LANCOS iteration method to obtain the vibration characteristics of the direct-drive dual-axis turntable, including the vibration frequency, the main vibration mode and the corresponding critical speed. The present invention is simple to operate, fast, efficient, and low in cost, greatly saves the analysis time of the vibration characteristics of the direct-drive dual-axis turntable, and has great guiding significance for the structural design and optimization of the direct-drive dual-axis turntable. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a flowchart of an embodiment of the present invention.

[0042] Figure 2 It is a schematic diagram of a three-dimensional model of a direct-drive dual-axis turntable established and preprocessed according to an embodiment of the present invention.

[0043] Figure 3It is a schematic diagram of a fluid equivalent three-dimensional model of an embodiment of the present invention.

[0044] Figure 4 It is a schematic diagram of setting ports of a fluid equivalent three-dimensional model according to an embodiment of the present invention.

[0045] Figure 5 It is a schematic diagram of an equivalent spring constraint method in an embodiment of the present invention. DETAILED DESCRIPTION

[0046] The present invention provides a vibration characteristic analysis method of a direct-drive dual-axis turntable based on finite element analysis software (ANSYS), such as Figure 1 As shown, follow the steps below:

[0047] Step 1. Create a 3D model of the direct-drive dual-axis turntable and perform preprocessing

[0048] Step 1.1 Establish a three-dimensional model of the direct-drive dual-axis turntable according to the structural design scheme of the direct-drive dual-axis turntable;

[0049] Step 1.2 Remove small accessories such as gaskets, screws, and hoses, chamfers with a side length of less than or equal to 5 mm, and fillets with a radius of less than or equal to 5 mm from the three-dimensional model of the direct-drive dual-axis turntable, and process the interference fit structure and fixed joint surface using a shared topology method;

[0050] The pre-processed 3D model of the direct-drive dual-axis turntable is as follows Figure 2 As shown, it is composed of pneumatic clamps, worktable, torque motor, protective cover, circular grating, turntable bearing, C-axis cradle casting, A-axis fixed seat and sealing structure;

[0051] There is one torque motor on each side of the A-axis (horizontal axis). The stator of the A-axis torque motor and the A-axis fixing seat form a cooling oil circuit, and the protective cover is installed and fixed on the A-axis fixing seat;

[0052] The bottom of the A-axis fixed seat is installed on the bed by bolts, and the circular grating is installed on the outside of the inner rotor of the torque motor. The rotation of the inner rotor of the A-axis torque motor drives the C-axis to swing;

[0053] The lower table of the C-axis workbench is connected and installed with pneumatic clamps, turntable bearings, and torque motor rotors in sequence. The C-axis torque motor stator and the C-axis cradle casting form a cooling oil circuit;

[0054] Step 2. Solve the thermal load of the cooling pipe of the direct-drive dual-axis turntable

[0055] Step 2.1 Use 3D software to extract Figure 3 The fluid equivalent three-dimensional model of the cooling oil circuit of the direct-drive dual-axis turntable shown is input into the fluid pre-processing module of the finite element analysis software, and the fluid equivalent three-dimensional model is meshed;

[0056] Step 2.2 Determine the coolant volume flow rate and flow rate

[0057] According to the torque motor selection, the rated power is obtained respectively P , power loss , cooling oil specific heat , cooling oil inlet and outlet temperature , get the cooling oil volume flow and flow rate as follows:

[0058] , flow rate , A is the cross-sectional area of ​​the cooling oil channel;

[0059] Step 2.3 Determine the convection heat transfer coefficient between the motor stator and the cooling oil channel

[0060] Determine the convection heat transfer coefficient between the motor stator and the cooling oil channel according to the following formula: ;

[0061] In the formula is the Nusselt number, is the thermal conductivity of the cooling oil, D is the cooling pipe diameter;

[0062] Said , where is the Reynolds number, is the Plandall dimension, L is the geometric characteristic length of the cooling channel;

[0063] Reynolds number , is the kinematic viscosity of the cooling oil, is the cooling oil density;

[0064] Planck dimension ; The Plandall dimension calculated by the embodiment of the present invention is 367;

[0065] Step 2.4 Determine the torque motor rotor heat transfer coefficient ;

[0066] ;in is the rotor speed;

[0067] Step 2.5 Set each port according to the cooling oil circuit distribution of the direct-drive dual-axis turntable, such as Figure 4 As shown, the inward arrow port is the inlet port, and the outward arrow port is the outlet port. At the same time, the inlet is set as a pressure inlet or a velocity inlet, and the outlet is set as a pressure outlet.

[0068] Step 2.6 In the FLUID FLOW module of the finite element analysis software, set the surface of the direct-drive dual-axis turntable in contact with the air to the convection heat transfer type, and input the inlet temperature, ambient temperature and the results obtained in 2.1-2.5 according to the actual working conditions of the direct-drive dual-axis turntable, set the contact surface between the cooling pipeline oil circuit of the direct-drive dual-axis turntable and the cradle casting as the coupling surface, and use the SIMPLE algorithm to solve the thermal load of the cooling oil circuit;

[0069] Step 3. Solve the deformation field of the direct-drive dual-axis turntable under the influence of heat. Perform the following operations in the finite element analysis software:

[0070] Step 3.1 Assign materials to each part according to the direct-drive dual-axis turntable structure, divide all parts with hexahedral structured grids, refine the grids for the coupling surface positions by virtual surface cutting methods, and divide the cross-sectional gradient changes of all part structures into at least 3 layers;

[0071] Step 3.2: Input the density, Poisson's ratio and mass of the main components of the direct-drive dual-axis turntable, wherein the main components are the clamp, worktable, motor, protective cover, circular grating, bearing, cradle casting and A-axis fixing seat;

[0072] Step 3.3 applies the heat load calculated in step 2 to the cooling pipe of the direct drive dual shaft;

[0073] Step 3.4 Apply the gravity load and cutting force load of the part to be processed to the C-axis worktable surface, constrain the outer cylindrical end surface of the A-axis fixed seat, and constrain the bolt holes with a diameter greater than 10 mm in an equivalent spring manner;

[0074] The equivalent spring method fixes the constraint as Figure 5 As shown: the boundary circle of the upper section of the bolt hole is coupled to the center position A, the boundary circle of the lower section of the bolt hole is coupled to the center position B, a spring connection is added between points AB, the spring stiffness value is input, and fixed constraints are set for points AB;

[0075] Step 3.5 Input the gravity acceleration of 9.8m / s on the overall structure of the direct-drive dual-axis turntable 2 ;

[0076] Step 3.6 Use the DIRECT algorithm of the static structural module of the finite element analysis software to solve the deformation field of the direct-drive dual-axis turntable under the influence of heat;

[0077] Step 3.7: Evaluate the correctness of the deformation field according to the accuracy requirements of the direct-drive dual-axis turntable. If the accuracy requirements are met, proceed to step 4; otherwise, proceed to step 3.8.

[0078] Step 3.8: Determine whether any major components are missing. If yes, return to step 1; otherwise, return to step 2.

[0079] Step 4. Vibration characteristics analysis of direct-drive dual-axis turntable

[0080] Step 4.1 Input the deformation field of the direct-drive dual-axis turntable under the influence of heat obtained in step 3 into the modal module of the finite element analysis software, set the frequency analysis step, set the vibration frequency order to 10, use the Lanczos iteration method to solve the extreme eigenvalues ​​of the matrix, and obtain the first 10 vibration frequencies and main vibration modes;

[0081] Each critical speed RPM is equal to the corresponding natural frequency HZ multiplied by 60:

[0082] 1st order critical speed (RPM) = 1st order natural frequency (HZ) multiplied by 60;

[0083] 2nd order critical speed (RPM) = 2nd order natural frequency (HZ) multiplied by 60; ...

[0085] 10th critical speed (RPM) = 10th natural frequency (HZ) multiplied by 60;

[0086] Step 4.2 Evaluate the vibration characteristics of the direct-drive dual-axis turntable

[0087] Compare each critical speed with the maximum operating speed of the direct-drive dual-axis turntable. If the two are not equal, the vibration characteristics of the direct-drive dual-axis turntable are excellent. Otherwise, the vibration characteristics are poor, and the rigidity of the turntable needs to be changed so that the operating speed is away from the critical speed.

Claims

1. A vibration characteristic analysis method of a direct-drive dual-axis turntable based on finite element analysis software, characterized in that Follow the steps below: Step 1. Create a 3D model of the direct-drive dual-axis turntable and perform preprocessing Step 1.1 Establish a three-dimensional model of the direct-drive dual-axis turntable according to the structural design scheme of the direct-drive dual-axis turntable; Step 1.2: Remove small and medium-sized accessories, chamfers with a side length of less than or equal to 5 mm, and fillets with a radius of less than or equal to 5 mm in the three-dimensional model of the direct-drive dual-axis turntable, and process the interference fit structure and the fixed joint surface using a shared topology method; Step 2. Solve the thermal load of the cooling pipe of the direct-drive dual-axis turntable Step 2.1 Use 3D software to extract the fluid equivalent 3D model of the cooling oil circuit of the direct-drive dual-axis turntable, input it into the fluid pre-processing module of the finite element analysis software, and mesh the fluid equivalent 3D model; Step 2.2 Determine the coolant volume flow rate and flow rate ; According to the torque motor selection, the rated power is obtained respectively P , power loss , cooling oil specific heat , cooling oil inlet and outlet temperature , get the cooling oil volume flow and flow rate as follows: , flow rate , A is the cross-sectional area of ​​the cooling oil channel; Step 2.3 Determine the convection heat transfer coefficient between the motor stator and the cooling oil channel Determine the convection heat transfer coefficient between the motor stator and the cooling oil channel according to the following formula: ; In the formula is the Nusselt number, is the thermal conductivity of the cooling oil, D is the cooling pipe diameter; Said , where is the Reynolds number, is the Plandall dimension, L is the geometric characteristic length of the cooling channel; Reynolds number , is the kinematic viscosity of the cooling oil, is the cooling oil density; Planck dimension ; Step 2.4 Determine the torque motor rotor heat transfer coefficient ; ;in is the rotor speed; Step 2.5: Set each port according to the cooling oil circuit distribution of the direct-drive dual-axis turntable, and set the inlet to pressure inlet or velocity inlet, and the outlet to pressure outlet; Step 2.6 In the FLUID FLOW module of the finite element analysis software, set the surface of the direct-drive dual-axis turntable in contact with the air to the convection heat transfer type, and input the inlet temperature, ambient temperature and the results obtained in 2.1-2.5 according to the actual working conditions of the direct-drive dual-axis turntable, set the contact surface between the cooling pipeline oil circuit of the direct-drive dual-axis turntable and the cradle casting as the coupling surface, and use the SIMPLE algorithm to solve the thermal load of the cooling oil circuit; Step 3. Solve the deformation field of the direct-drive dual-axis turntable under thermal influence Step 3.1 Assign materials to each part according to the direct-drive dual-axis turntable structure, divide all parts with hexahedral structured grids, refine the grids for the coupling surface positions by virtual surface cutting methods, and divide the cross-sectional gradient changes of all part structures into at least 3 layers; Step 3.2: Input the density, Poisson's ratio and mass of the main components of the direct-drive dual-axis turntable, wherein the main components are the clamp, worktable, motor, protective cover, circular grating, bearing, cradle casting and A-axis fixing seat; Step 3.3 applies the heat load calculated in step 2 to the cooling pipe of the direct drive dual shaft; Step 3.4 Apply the gravity load and cutting force load of the part to be processed to the C-axis worktable surface, constrain the outer cylindrical end surface of the A-axis fixed seat, and constrain the bolt holes with a diameter greater than 10 mm in an equivalent spring manner; The equivalent spring fixed constraint is to couple the boundary circle of the upper section of the bolt hole to the center position A, and the boundary circle of the lower section of the bolt hole to the center position B, add a spring connection between the two points AB, input the spring stiffness value, and set the fixed constraint of the two points AB; Step 3.5 Input the gravity acceleration of 9.8m / s on the overall structure of the direct-drive dual-axis turntable 2 ; Step 3.6 Use the DIRECT algorithm of the static structural module of the finite element analysis software to solve the deformation field of the direct-drive dual-axis turntable under the influence of heat; Step 3.7: Evaluate the correctness of the deformation field according to the accuracy requirements of the direct-drive dual-axis turntable. If the accuracy requirements are met, proceed to step 4; otherwise, proceed to step 3.

8. Step 3.8: Determine whether any major components are missing. If yes, return to step 1; otherwise, return to step 2. Step 4. Vibration characteristics analysis of direct-drive dual-axis turntable Step 4.1 Input the deformation field of the direct-drive dual-axis turntable under the influence of heat obtained in step 3 into the modal module of the finite element analysis software, set the frequency analysis step, set the vibration frequency order to 10, use the Lanczos iteration method to solve the extreme eigenvalues ​​of the matrix, and obtain the first 10 vibration frequencies and main vibration modes; Each critical speed RPM is equal to the corresponding natural frequency HZ multiplied by 60; Step 4.2 Evaluate the vibration characteristics of the direct-drive dual-axis turntable Compare each critical speed with the maximum operating speed of the direct-drive dual-axis turntable. If the two are not equal, the vibration characteristics of the direct-drive dual-axis turntable are excellent, otherwise, the vibration characteristics are poor.

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