CN101458205A

CN101458205A - Fixation joint part dynamics parameter identification method for machine tool

Info

Publication number: CN101458205A
Application number: CNA2008101968230A
Authority: CN
Inventors: 毛宽民; 李斌; 徐强
Original assignee: Huazhong University of Science and Technology
Current assignee: Huazhong University of Science and Technology
Priority date: 2008-08-29
Filing date: 2008-08-29
Publication date: 2009-06-17
Anticipated expiration: 2028-08-29
Also published as: CN101458205B

Abstract

The invention provides an identification method of dynamic parameters of a machine tool fixed joint part. The method comprises the following steps: taking a structural damping matrix of a joint part unit and a stiffness matrix of the joint part unit as parametric variables, setting the difference between the product of a displacement impedance matrix and a displacement frequency response function and a unit matrix to be minimum as an optimum design objective, and obtaining parameter variable values (i.e., the identified parameters of the joint part) through multiple iteration. The identification method takes damping and stiffness of multiple key freedom directions and the intercoupling relation into account to avoid a secondary error produced by matrix inversion, has high precision, and more accurately characterizes richer dynamic characteristics of the joint part.

Description

Method for identifying dynamic parameters of fixed joint of machine tool

Technical Field

The invention relates to a method for identifying dynamic parameters of a common fixed joint (bolt connection) of a machine tool, in particular to a method for identifying rigidity and damping parameters of the joint.

Background

Since the 20 th 60 s, the important influence of the joint in the machine tool structure on the overall machine structure was recognized, researchers made extensive and intensive studies on the dynamic characteristics of the joint and a parameter identification method, and obtained remarkable results. However, the property parameters of the joint cannot be precisely controlled, so that there are still many problems to be studied in depth.

Whatever the type of joint, the joint is a "flexible joint", which is a non-competing fact. By "flexible binding" is meant: when the joint part is acted by an external complex dynamic load, multi-freedom-degree damped micro-amplitude vibration (namely changed micro relative displacement or rotation) can be generated between the joint surfaces, so that the joint part shows the nature and the characteristics of flexible combination which has elasticity and damping, stores energy and dissipates energy. Therefore, of the dynamic characteristics of the joint portion, the stiffness characteristics and the damping characteristics significantly affect the dynamic performance of the machine tool structure, while the mass characteristics thereof have little influence on the dynamic characteristics of the machine tool structure. The dynamic characteristics of the joint are researched to identify the rigidity and the damping of the joint.

The most common method of modeling joint dynamics, 90 s ago, was to represent the joint as a series of isolated viscoelastic elements, as shown in fig. 1, i.e., to simulate the overall joint surface dynamics. However, this method has two disadvantages:

1) the parameters of the joint part modeled and identified by the method are only suitable for specific structures, and when the size and the shape of the joint part are changed, the joint surface parameters are difficult to transplant and have no universality.

2) In the model, only the stiffness characteristic and the damping characteristic of the normal direction of each degree of freedom are considered, the coupling characteristic between the degrees of freedom is neglected, and the mechanical characteristic of the tangential direction of the joint part is not considered.

The kingdom and the francium of Qingdao university are based on finite element thought, and a new ' ideal binding surface element ' model of an ' ideal binding part ' is provided, and a dynamic binding part model based on the ' binding surface element ' is further provided, as shown in fig. 2 (O-XYZ is a global coordinate system, and O ' -X ' Y ' is a unit local coordinate system). This model assumes the dynamic properties of the joint (including different materials, pre-tension, surface roughness, machining methods, media, etc.) under various conditions, and can be equated with the dynamic properties of an ideal joint. The term "ideal joint" refers to a joint in which the specific pressure between joints is constant over the entire joint, and points on the joint are in uniform contact with each other and have the same mechanical properties at all points of contact. And carrying out finite element division on the ideal joint to obtain an ideal joint limited unit. However, the conditions of the model are too severe, and the joint portion with a large contact surface size has a certain limitation. When the model parameters are determined, the specific pressure needs to be accurately determined, which is difficult.

After determining the equivalent dynamic model of the joint, the equivalent dynamic parameters of the spring and damper of each degree of freedom in the model also need to be determined.

Early researchers identified joint parameters by direct testing methods, i.e., directly testing the relationship between force and displacement (response) at the joint to study the stiffness characteristics of the joint; by repeated loading and unloading, the force and displacement (response) hysteresis loop of the joint is tested, and the damping characteristic at the joint is measured by the area size contained by the hysteresis loop. Although this identification method is straightforward and physically significant, the stiffness and damping characteristics of the joint are generally non-linear, which makes the identified parameters very different from the actual values, and does not simulate the complex dynamics of the joint well.

For the rigidity and damping characteristics of the plane connection joint, people such as Kilssatot doll, copahh, and Sorrill have conducted intensive research and propose a 'rigidity meter algorithm for the bolt joint part'. Assuming normal displacement λ and average contact pressure P on the contact surface_nThe exponential function of (a) is:

(α/m is a constant determined by the method and material of processing the bonding surface, etc., and can be found from an empirical data table), whereby the normal stiffness of the bonding surface is

Two-plane contact bonding surface under average shearing force F_τThe tangential displacement under influence δ can be expressed as: delta-k_τF_τ，k _τ1/k for shear flexibility of the joint surface_τI.e. the shear dynamic stiffness.

The study of machine tool joints by the filial piety, Ji Cunchun, university of Kyoto, Japan, showed that the dynamic performance data per unit area of the joints were the same as long as the average contact pressure of the joints was the same, despite the differences in the joint contact areas, and a table of the dynamic performance data per unit area of the joints was summarized. Once the structure is determined, the corresponding joint part is determined, and at this time, the corresponding characteristic data of the unit area is searched from the data table according to the condition of the joint surface, and the rigidity and the damping of the joint surface can be obtained by integrating the joint area, which is the 'Ji Cuniu Xiao integral method'.

Later researchers have proposed a frequency response function test identification method based on mechanical impedance. The basic idea is as follows: and (3) extracting dynamic parameters of the structure joint part by using Frequency Response Functions (FRFs) of the substructures and the overall structure, and considering the influence of test errors when testing the frequency response functions. However, when calculating the dynamic parameters of the joint portion, it is necessary to invert the frequency response function matrix of the substructure, and after matrix inversion operation, a very large recognition error is inevitably caused by a small measurement error introduced by noise interference. Although researchers hereafter have come to know about this problem, recognition accuracy is improved to some extent. However, in either method, when identifying the parameters of the joint, the frequency response function of each substructure is tested, and there is no characteristic parameter (such as normal preload, surface roughness, metal material, surface processing mode, etc.) related to the joint. Therefore, the identified parameters are again accurate and only applicable to the identified power system, and have no universality.

Disclosure of Invention

The invention aims to provide a method for identifying dynamic parameters of a fixed joint of a machine tool, which fully considers the damping and rigidity of a plurality of key freedom degrees and the mutual coupling relation of the key freedom degrees, avoids secondary errors brought by matrix inversion and has high precision.

A method for identifying dynamic parameters of a fixed joint of a machine tool specifically comprises the following steps: damping matrix C with joint unit structure₁And a joint unit stiffness matrix K₁For the parameter variables, the solution is such that (- ω)²M + i ω C + K) H (ω) approaches the optimal solution C of the identity matrix₁And K₁Wherein the mass matrix M is a substructure mass matrix M₀The damping matrix C is a combined part unit structure damping matrix C₁And substructure damping matrix C₀Assembled, the rigidity matrix K is formed by a combination part unit rigidity matrix K₁And substructure stiffness matrix K₀H (omega) is a frequency response function of angular frequency omega, and i is an imaginary number unit;

the combined part unit structure damping matrix C₁And a joint unit stiffness matrix K₁The damping and the rigidity of each node of the joint unit in the directions of three translational degrees of freedom are respectively considered in the set form of (A), and the requirement C is met₁＝igK₁And g is the structural loss factor.

A method for identifying dynamic parameters of a fixed joint of a machine tool specifically comprises the following steps: damping matrix C with joint unit structure₁And a joint unit stiffness matrix K₁For the parameter variables, the solution is such that (- ω)²M + C + K) H (omega) approaches the optimal solution C of the identity matrix₁And K₁Wherein the mass matrix M is a substructure mass matrix M₀The damping matrix C is a damping matrix C with a joint unit structure₁The stiffness matrix K is a combination unit stiffness matrix K₁And substructure stiffness matrix K₀H (omega) is a frequency response function of angular frequency omega, and i is an imaginary number unit;

The combined part unit structure damping matrix C₁And a joint unit stiffness matrix K₁All are (3 × n) × (3 × n) dimensional matrices, and n is the number of nodes of the joint unit. The number of nodes in the joint unit may be 8, 16 or 18, and as the number of nodes to be selected increases, the accuracy increases, but the computational complexity also increases, so 8 nodes are preferable.

The invention establishes a 'parameterized' dynamic model of the joint part on the basis of a finite element theory and a vibration mechanics theory, and the model fully considers various influencing factors of the joint part and the coupling relation among dynamic parameters; then, on the basis of the characteristic, the fundamental property of the reciprocity of the impedance matrix and the frequency response matrix of the multi-degree-of-freedom dynamic system is utilized, the method of combining theoretical modal calculation and experimental modal test is adopted to identify the rigidity and the damping of the joint part, the identification precision is high, and the richer dynamic characteristics of the joint part can be represented more accurately.

The method comprises the steps of firstly obtaining theoretical values (stiffness and damping matrix of an entity substructure) of finite element analysis and experimental values (frequency response function of an overall structure) obtained by experimental mode analysis, then utilizing an optimization design method, taking required joint parameters (stiffness matrix and damping matrix of the joint in research) as design variables, taking the minimum difference between the product of an impedance matrix and the frequency response function and a unit matrix as an optimization design target, and obtaining design variable values through multiple iterations as identified joint parameters.

Compared with the prior art, the error of the theoretical calculation result and the experiment comparison of the new dynamic model of the binding part established by the invention is not more than 7%, the precision is greatly improved, and the advancement of the established model and the solving method is explained.

Drawings

FIG. 1 is a schematic view of a joint spring damper model;

FIG. 2 is a schematic view of a rectangular ideal joint unit;

FIG. 3 is a schematic view of a bolt connection, where FIG. 3a is a "line" type and FIG. 3b is an "array" type;

FIG. 4 is a schematic view of a bolt coupling unit model of a joint, showing a "line form" coupling unit model of FIG. 4a, and showing an "array form" coupling unit model of FIG. 4 b;

FIG. 5 is a schematic diagram of a finite element model of a junction;

FIG. 6 is a diagram of a force model of the joint unit;

FIG. 7 is a schematic representation of a binding portion kinetic model;

FIG. 8 is a schematic view of an experimental apparatus;

fig. 9 is a schematic view of an experimental test piece.

Detailed Description

The method comprises the following specific implementation steps:

1) various forms of the common machine tool fixed joint part are investigated, a division rule of a fixed joint part finite element model is given, essential attributes of the fixed joint part finite element model are extracted, and a 'parameterized' joint part element dynamic model is established;

2) finite element analysis is carried out on the substructure, and a substructure quality matrix M is extracted₀And a stiffness matrix K₀The substructure is typically machined from steel, which itself has very little material damping, in which case 90% of the internal damping of the machine structure comes from the machine interface,damping matrix C of story structure₀And joint damping matrix C₁The contrast is negligible;

3) according to the node corresponding relation of the 'parameterized' combination part unit dynamic model, a finite element matrix assembly theory is utilized to combine the substructure rigidity matrix K₀And a stiffness matrix K of the joint unit₁Assembling to obtain a total steel K; the influence of the quality characteristics of the joint part on the dynamic characteristics of the machine tool structure is very negligible, so that the total mass M is M₀The damping matrix C is a damping matrix C with a joint structure₁The expansion is obtained, namely the block matrix corresponding to the node position of the combining part 8 in C is C₁And the other elements are zero; k₁And C₁Namely the kinetic parameters to be solved;

4) the method comprises the steps of carrying out modal experiments on a reduced model which is extracted from a real structure and comprises a joint part unit, measuring a frequency response function of the whole structure connected by bolts, assembling an impedance matrix containing parameters to be solved and obtained by finite element theory and the reciprocity of the actually measured frequency response function, and solving a design variable value through multiple iterations by utilizing a least square method.

5) The joint part can not be separated from a mechanical structure system to exist, the validity of the dynamic parameters of the joint part obtained by solving is verified, corresponding parameters are required to be brought into the whole structure system, theoretical modal analysis is carried out on the whole model, and comparison and verification are carried out on the theoretical modal analysis result and the experimental modal analysis result.

1. Investigation, analysis and modeling

The dynamic model of the binding part established by researchers at present does not fully reflect the specific properties of the binding part (material, surface appearance, pretightening force, existence of medium (lubricating oil and the like), size and geometric shape of the binding part), and the model is named as a non-parametric binding part model, which is also the main reason for limiting the universality of the research result of the binding part at present.

In view of this, we propose to build a "parameterized" binding site kinetic model that reflects the specific properties of the binding site. The expression of the joint stiffness K and the damping C established by the model includes the specific properties of the joint, and it is conceivable that the same joint dynamic parameter model can be used as long as the specific parameters of the joint are consistent. Therefore, the 'parameterized' model of the joint part has universality, and can provide uniform theoretical and data support for establishing the overall dynamic model of the machine tool structure.

The research shows that most of the machine tool fixing joint parts are in screw connection and are in two forms of a linear form and an array form, and the screw connection positions are called connection points, as shown in fig. 3. According to the elastic mechanics St.Venant local influence principle and the simulation calculation result of the stress of the fixed joint, the following assumptions are made on the dynamic characteristics of the joint. For "linear" connection forms: the dynamic characteristics of the joint between two adjacent screws are only controlled by the mechanical states of the two screws, and are not related to the mechanical states of other screws except the two screws (as shown in fig. 4 (a)); for "array" connections: the dynamic characteristics of the joints between the adjacent four screws are controlled only by the mechanical states of the four screws, and are not related to the mechanical states of the screws other than the four screws (as shown in fig. 4 (b)).

It can be seen that the joint unit model can be represented in the form shown in fig. 5, in which I, II are the upper and lower substructure units of the bolt connection, III is the imaginary joint unit, and 1-5, 2-6, 3-7, and 4-8 are the 8 nodes corresponding to the joint unit, regardless of the "line type" connection or the "array type" connection. Each joint unit has 8 nodes, each node has 3 degrees of freedom (three translational degrees of freedom), and each unit has 24 degrees of freedom. The movement of the joint unit will be represented by the relative movement between

nodes

1 and 5,

nodes

2 and 6,

nodes

3 and 7, and

nodes

4 and 8. As long as the relationship between the node displacement and the node stress can be accurately established, the dynamic model is established.

For a joint there are six different forms of dynamic force, sixGeneralized force of the individual degrees of freedom (as shown in fig. 6). Damping forces in six degrees of freedom can also be generated and have different damping loss factors. These dynamic forces are respectively: positive force F in Z direction_zX, Y shear force F_x，F_yBending moment M about axis X, Y_θx，M_θyAnd shear torque M about the Z axis_θz。

For a joint, its mass is negligible, and only its elastic and damping properties are taken into account when building its dynamic model.

Let each node displacement be d_ijEach node is subjected to a

force f

_ij1, 2, 7, 8; j is 1, 2, 3. A stiffness matrix of the joint finite element is first derived. As mentioned above, the motion characteristics of the joint are represented by the relative motion between

nodes

1 and 5, 2 and 6, 3 and 7, and 4 and 8, which can be expressed as: (d)_1j-d_5j)、(d_2j-d_6j)、(d_3j-d_7j)、(d_4j-d_8j) J is 1, 2, 3. According to the stiffness influence coefficient method without taking damping into account

Wherein,

for the stiffness influence coefficient, i, m is 1, 2, 3, 4, which represents a node; n, j is 1, 2, 3, and represents a degree of freedom direction;

the specific physical significance is as follows: the unit relative displacement is generated only in the n direction of the node m and the node (m +4), and the force required to be applied in the i node j direction is correspondingly generated.

Under equilibrium conditions, with f_1j＝-f_5j、f_2j＝-f_6j、f_3j＝-f_7j、f_4j＝-f_8j(j＝1，2，3)

Let the node displacement vector of the joint unit be:

[D₁]＝(d₁₁，d₁₂，d₁₃，d₂₁，d₂₂，d₂₃，...d₈₁，d₈₂，d₈₃)

the joint unit node elastic force vector is:

[F_k1]＝(f₁₁，f₁₂，f₁₃，f₂₁，f₂₂，f₂₃，...f₈₁，f₈₂，f₈₃)

thus, equation (1) is written in matrix form: [ K ]₁][D₁]＝[F_k1]

From the above derivation, the joint unit stiffness matrix [ K ]₁]Has symmetry and blocking; the blocking form is as follows:

where K' is the matrix of the unit stiffness of the joint [ K₁]The upper left corner matrix after "quartering" is performed, and by using this property, [ K ] can be simplified₁]The calculated amount of (c) is obtained by obtaining [ K']_12×12By utilizing this property, [ K ] can be obtained₁]_24×24. Matrix [ K']_12×12The specific arrangement of the elements in (A) is shown below.

The damping of the joint unit is usually a structural damping, the damping force f of which is the structural damping_dProportional to the vibration displacement x, the phase leads the displacement by 90 DEG, the structural damping coefficient eta, then f_dI η x. And η is proportional to the stiffness k, η ═ gk, and g is the structural loss factor (also known as the structural damping ratio, an empirical constant). Thus f_dI η x igkx. Imitating a unit stiffness matrix [ K ] of a joint part₁]Can obtain a structural damping force matrix [ F ] of the joint unit_d1]And vibration displacement [ D ]₁]The equilibrium equation between is:

[C₁][D₁]＝[F_d1]wherein [ C₁]＝ig[K₁]

Therefore, the structural damping matrix form of the combination unit is

According to the stress condition analysis of the joint unit, the joint unit can be represented as a model shown in fig. 7, the model is called as a "parameterized" dynamic model of the joint, the model unit is an eight-node hexahedron-shaped unit, namely the unit is an imaginary unit with a hexahedron space topological shape, and the eight nodes are 8 corner points shown in the figure. The stiffness and the coupling relation thereof in all directions are explicitly plotted in fig. 7, the damping is only indicated by C in the figure, and the damping coupling relation is similar to the stiffness.

2. Description of the principles of the identification method

For a multi-degree-of-freedom vibration system, the dynamic differential equation is as follows:

whereinIs an inertial force [ F_a]，Is damping force [ F_d]，K[D]Is an elastic force [ F_k]，[F]For applying an exciting force, [ D ]]Is the system displacement matrix.

The system impedance matrix (also called dynamic stiffness matrix) expressed by this equation is: - ω²M + i ω C + K, the inverse of which is the frequency response function matrix H (w) of the system.

So that it is possible to obtain: (-. omega.) W²M + i ω C + K) H (ω) ═ E, E is an identity matrix

The substructure is typically machined from steel, which itself has very little material damping, in which case 90% of the internal damping of the machine structure comes from the machine joints, and so the substructure

Damping matrix C₀And joint damping matrix C₁The comparison is negligible. System damping force matrix [ F ]_d]＝[C][D]Wherein [ C]For the system damping matrix, [ C ] since the system damping takes into account only the structural damping of the joints]Damping matrix C with only joint unit structure₁And (4) correlating.

So that the kinetic differential equation can be simplified to

The impedance matrix is: - ω²M + C + K, and making the product of M + C + K and frequency response function matrix H (w) collected by test approach to the optimum solution of unit matrix to obtain C₁And K₁. Formula-omega²The system damping matrix C in M + C + K is a damping matrix C with a combination part unit structure₁Expanding, if the serial numbers of 8 nodes of the joint part in the structural integral finite element model are still 1-8, the C matrix form can be expressed as

C = (\begin{matrix} C_{1} & 0 \\ 0 & 0 \end{matrix})

That is, the block matrix corresponding to the node position of the combining part 8 in C is C₁And the other elements are zero; stiffness matrix K is formed from substructure stiffness matrix K₀And a stiffness matrix K of the joint unit₁Assembling to obtain; quality matrix M ═ M₀. For each substructure, the quality matrix M₀Damping matrix (proportional damping, negligible), stiffness matrix K₀Can be obtained by finite element theory; for the joint, neglecting its mass matrix, its stiffness matrix K₁And a damping matrix C₁Kinetic parameters were determined for the present invention.

3. Experiment, solution and verification

The experimental system comprises a fixed joint part test piece (a substructure I, II and a joint part III), an acceleration sensor IV, a connecting screw, an exciting force hammer VI (including a force sensor V), a charge amplifier VII, an LMS-CADA-X signal acquisition and processing system VIII, a PC (personal computer) IX, a flexible suspension rope, a support frame, a cable shielding wire and other experimental equipment. And (3) freely suspending the joint test piece by using a flexible rope, and carrying out frequency response test on the joint model by adopting a single-point excitation multi-point test (SIMO) method, wherein the schematic diagram of the experimental device is shown as 8.

In the experiment, a joint part experiment test piece is suspended as shown in fig. 9 (a substructure I, II and a joint part III), is excited by a force hammer VI at a certain point, adopts a plurality of acceleration sensors IV to acquire response signals, is processed by an LMS signal acquisition and processing system VIII, extracts a frequency response function of the whole structure from a PC IX, can be assembled by using a finite element theory to obtain an impedance matrix, and can obtain unknown rigidity and damping parameters of the joint part by using the fundamental property of reciprocity of an impedance matrix and a frequency response matrix of a multi-degree-of-freedom dynamic system.

The basic parameters of the test piece shown in fig. 9 are as follows:

experimental materials: 45# steel;

size of the joint: 60mm × 31.5mm × 29 mm;

size of the structural part: 190mm × 190mm × 100 mm;

the pre-tightening torque is as follows: 45 N.m;

the number of nodes divided by the experiment is: 72 are provided;

two bolted connections, bolt: m10

The joint stiffness matrix K to be identified using the present invention₁Damping matrix C₁And substituting the model into the established dynamic model of the joint part, assembling the model and the finite element dynamic model of each substructure forming the joint part to obtain a structural overall dynamic model containing the joint part, and performing theoretical modal analysis on the overall model and comparing the theoretical modal analysis with the experimental result. The comparison results are shown in table 1.

Mode shape of each order	Experimental results (Hz)	Theoretical results (Hz)	Error of the measurement
Mode shape of each order	Experimental results (Hz)	Theoretical results (Hz)	Error of the measurement	1 yaw	409	409	0％
2 measuring turn over	471	451	4.2％	1 yaw	409	409	0％
2 measuring turn over	471	451	4.2％	3 pitching	871	853	2.1％
4 left-right translation	1673	1765	5.5％	3 pitching	871	853	2.1％
4 left-right translation	1673	1765	5.5％	5 forward and backward translation	2130	2278	6.95％
6 up and down translation	2568	2647	3.％	5 forward and backward translation	2130	2278	6.95％

TABLE 1 natural frequencies of the respective orders

As can be seen from the above table, the error between the theoretical and experimental calculation results does not exceed 7% at most. Therefore, the parameters of the joint part identified by the method have high precision and can well simulate the real characteristics of the joint part.

The results of the calculation were compared with the "calculation method of rigidity of bolt joint portion" and the "gigchun filial piety integration method", and the results are shown in table 2.

Modes of each order	Results of the experiment/Hz	Theoretical results/Hz	Jicungxiao	Calculation of bolt stiffness
Modes of each order	Results of the experiment/Hz	Theoretical results/Hz	Jicungxiao	Calculation of bolt stiffness	1 yaw	409	409	110	87
2 measuring turn over	471	451	385	456	1 yaw	409	409	110	87
2 measuring turn over	471	451	385	456	3 pitching	871	853	755	886
4 left and right are flat	1673	1765	391	309	3 pitching	871	853	755	886
4 left and right are flat	1673	1765	391	309	5 front and back are flat	2130	2278	394	310
6 is flat at the upper part and the lower part	2568	2647	1852	2430	5 front and back are flat	2130	2278	394	310

TABLE 2 comparison of modal natural frequencies of respective orders

Table 2 shows that the error between the theoretical calculation result and the experimental result of the dynamic model of the binding part in the prior art is relatively large, while the error between the theoretical calculation result and the experimental result of the dynamic model of the binding part built by us is not more than 7%, which illustrates the advancement of the model built by us and the solving method.

The method is also a research on the parameter identification technology of the joint part based on the frequency response function, but can well simulate the real structure of the joint part. This result occurs because the dynamic model of the joint is created by taking the stiffness and damping characteristics of the joint in all directions into consideration, and the joint model is not simulated by artificially specifying a specific type of structure, and the influence of the parameters and coupling relationship of the joint on the characteristics of the joint is fully taken into consideration.

If the characteristics and parameters of the joint are taken as an unknown box, a black box modeling method is adopted when a dynamic model of the joint is established, namely modeling is only carried out according to input and output data of the system, and even if the structure and parameters of the system are unknown, a good simulation can be carried out on a solution model. Compared with the predecessors who use the gray box modeling, the predecessors tend to have a certain deviation because they add a certain empirical assumption when building the model.

The innovation points in the invention are as follows:

● take full account of the coupling between the degrees of freedom of the joint.

● shows the partition criteria for the fixed junction finite element model: the "linear" form and the "array" form.

●, the modeling precision and the solving result precision are greatly improved.

●, the concept of the 'parametric' dynamic model of the joint part is provided, the universality of the 'parametric' dynamic model of the joint part provides a new idea for the dynamic research of the machine tool structure, and a brand new calculation method is provided for the dynamic optimization design of the machine tool structure.

Claims

1. A method for identifying dynamic parameters of a fixed joint of a machine tool specifically comprises the following steps: damping matrix C with joint unit structure₁And a joint unit stiffness matrix K₁For the parameter variables, the solution is such that (- ω)²M + i ω C + K) H (ω) approaches the optimal solution C of the identity matrix₁And K₁Wherein the mass matrix M is a substructure mass matrix M₀The damping matrix C is a combined part unit structure damping matrix C₁And substructure damping matrix C₀Assembled, the rigidity matrix K is formed by a combination part unit rigidity matrix K₁Rigidity of substructureMatrix K₀H (omega) is a frequency response function of angular frequency omega, and i is an imaginary number unit;

2. A method for identifying dynamic parameters of a fixed joint of a machine tool specifically comprises the following steps: damping matrix C with joint unit structure₁And a joint unit stiffness matrix K₁For the parameter variables, the solution is such that (- ω)²M + C + K) H (omega) approaches the optimal solution C of the identity matrix₁And K₁Wherein the mass matrix M is a substructure mass matrix M₀The damping matrix C is a damping matrix C with a joint unit structure₁The stiffness matrix K is a combination unit stiffness matrix K₁And substructure stiffness matrix K₀H (omega) is a frequency response function of angular frequency omega, and i is an imaginary number unit;

3. Method for identifying kinetic parameters of a fixed joint of a machine tool according to claim 1 or 2, characterized in that said joint unit structure damping matrix C₁And a joint unit stiffness matrix K₁All are (3 × n) × (3 × n) dimensional matrices, and n is the number of nodes of the joint unit.

4. The method of identifying kinetic parameters of a fixed joint of a machine tool according to claim 3, wherein said joint unit is an eight-node hexahedral unit.

5. The method for identifying the kinetic model parameters of a fixed joint of a machine tool according to claim 4, characterized in that the damping matrix C of the unit structure of the joint is₁And a joint unit stiffness matrix K₁Are all 24 x 24 dimensional matrices.

6. The method of claim 5, wherein the eight-node hexahedral unit comprises two adjacent junction points.

7. The method of claim 5, wherein the eight-node hexahedral unit comprises four adjacent junctions.