Five-axis numerical control machine tool space attitude and position error real-time compensation method and device

Abstract

The invention belongs to the related technical field of five-axis numerical control machine tool space error compensation, and discloses a five-axis numerical control machine tool space attitude and position error real-time compensation method and device, and the method comprises the steps: S1, building a space error model of a numerical control machine tool; s2, separating and extracting a rotation error term from the comprehensive error term, and performing compensation instruction solution on the rotation error term through a pseudo-inverse matrix solving method to obtain a compensation instruction of the attitude error; s3, separating a singular part and a non-singular part of the compensation value of the attitude error, replacing a common reciprocal of a singular part parameter with a damping reciprocal, and further obtaining a new attitude error compensation instruction and performing compensation; and S4, subtracting the linear part of the translational axis error caused by the attitude error compensation from the linear part of the comprehensive error in the initial tool coordinate system, namely a translational axis error compensation instruction, and performing compensation. According to the method, the calculation efficiency is greatly improved, and meanwhile, the cutter posture error of the machine tool can be better compensated.

Description

Technical Field

[0001] The present invention belongs to the technical field related to spatial error compensation of five-axis CNC machine tools, and more specifically, relates to a method and device for real-time compensation of spatial posture and position errors of five-axis CNC machine tools. Background Art

[0002] Compared with traditional three-axis CNC machine tools, five-axis CNC machine tools can more flexibly change the position of the tool relative to the workpiece coordinate system by introducing two rotary axes, which has significant advantages in the processing of complex curved parts, but it also introduces more error terms. The main way to overcome this problem is to perform error compensation during the use phase of the five-axis CNC machine tool. The machine tool error terms are obtained by direct measurement or indirect identification, and these error terms are substituted into the error model to calculate the compensation value, thereby correcting the relative position of the tool and the workpiece. After years of development, the error compensation method has formed a complete theoretical system of error modeling, measurement identification, error compensation, and corresponding effect verification.

[0003] However, most of the current error compensation models are aimed at compensating for the tool spatial positioning error. But in side milling, cyclone milling and other machining processes, the tool posture error has a more significant impact on the machining accuracy. The commonly used homogeneous coordinate transformation method is complex and inefficient when solving the posture solution. Other methods, such as the compensation method based on screw theory, although they can obtain the analytical solution of the compensation value, require multiple iterative calculations in the actual compensation process and are not suitable for integration into the CNC system. The differential motion method can quickly obtain an approximate numerical solution, which is suitable for industrial application scenarios, but is not perfect in posture error compensation. Summary of the invention

[0004] In view of the above defects or improvement needs of the prior art, the present invention provides a real-time compensation method and device for spatial posture and position errors of a five-axis CNC machine tool, which aims to solve the problem of low computational efficiency of existing posture compensation methods.

[0005] To achieve the above object, according to one aspect of the present invention, a method for real-time compensation of spatial posture and position error of a five-axis CNC machine tool is provided, the method comprising the following steps:

[0006] S1, establish the spatial error model of CNC machine tools based on the differential motion relationship of each axis of the CNC machine tool and the forward kinematics model of the CNC machine tool;

[0007] S2, based on the spatial error model, firstly separate and extract the rotation error term from the comprehensive error term, and solve the compensation instruction of the rotation error term by the method of solving the pseudo-inverse matrix to obtain the compensation instruction of the attitude error;

[0008] S3, separating the singular part and the non-singular part of the compensation value of the attitude error, using the damped inverse to replace the ordinary inverse of the singular part parameter, and then obtaining a new attitude error compensation instruction to compensate the attitude error of the CNC machine tool;

[0009] S4, subtracting the linear part of the translation axis error caused by the posture error compensation from the linear part of the comprehensive error in the initial tool coordinate system, that is, obtaining the translation axis error compensation instruction that needs to be compensated, so as to compensate the position error of the CNC machine tool.

[0010] Furthermore, assuming that the command positions of the machine tool axes are x, y, z, a, and c, respectively, from the perspective of the tool side kinematic chain, the ideal homogeneous coordinate system transformation matrices of the Y axis relative to the machine tool coordinate system, the X axis relative to the Y axis, and the Z axis relative to the X axis coordinate system are:

[0011]

[0012] The homogeneous coordinate transformation of the A-axis relative to the machine tool coordinate system and the C-axis relative to the A-axis coordinate system is:

[0013]

[0014]

[0015] Furthermore, the ideal homogeneous transformation matrix of the tool coordinate system relative to the worktable coordinate system is:

[0016]

[0017] Based on the differential motion vector of each axis and the differential motion matrix relative to the tool coordinate system, the transfer relationship from the differential motion vector of each axis to the tool coordinate system can be obtained:

[0018]

[0019] in, Represents the differential motion matrix from the i-axis coordinate system to the tool coordinate system; ΔE i Represents the differential motion vector of the i-axis; i=X, Y, Z, A, C.

[0020] Furthermore, the comprehensive error of the tool in its own coordinate system can be expressed as the sum of the errors of each axis transferred to the tool coordinate system:

[0021]

[0022] in, Indicates the comprehensive error of the tool in its own coordinate system; Indicates the error of each axis of the machine tool transferred to the tool coordinate system; δ itRepresents the three position errors of the tool in its own coordinate system, ε it Indicates the three angular errors of the tool in its own coordinate system;

[0023] According to formula (6), the matrix representation of the tool comprehensive error in its own coordinate system is given as:

[0024]

[0025] Finally, the expression of the spatial error model is obtained as follows:

[0026]

[0027] Furthermore, the rotation error term is first separated and extracted from the comprehensive error term, and the compensation instruction of the rotation error term is solved by the method of finding the pseudo-inverse matrix to obtain the compensation values ​​of the A and C axes, so as to compensate the angle error using the compensation values:

[0028]

[0029] In the formula, S yz is the perpendicularity error between the Y-axis and the Z-axis, S xz is the perpendicularity error between the X-axis and the Z-axis, ε xx is the angular error of the X-axis around the X-axis, ε xy is the angular error of the Y axis around the X axis, ε xz is the angular error of the Z axis around the X axis, ε xa is the angular error of the A axis around the X axis, ε xc is the angular error of the C axis around the X axis, ε za is the angular error of the A axis around the Z axis, ε zc is the angular error of the C-axis around the Z-axis, ε yx is the angular error of the X-axis around the Y-axis, ε yy is the angular error of the Y axis around the Y axis, ε yz is the angular error of the Z axis around the Y axis, ε ya is the angular error of the A axis around the Y axis, ε yc is the angular error of the C-axis around the Y-axis.

[0030] Furthermore, taking λ 2 = A value near 0.1 is taken as the damping coefficient.

[0031] Furthermore, the translation axis error caused by the rotary axis error compensation can be calculated based on the differential motion relationship:

[0032]

[0033] Extract The linear error part in is recorded as Then we have:

[0034]

[0035] Furthermore, the linear part of the translation axis error caused by the rotary axis error compensation is subtracted from the linear part of the comprehensive error in the initial tool coordinate system to obtain the translation axis error compensation instruction that needs to be compensated:

[0036]

[0037] The present invention also provides a system for real-time compensation of spatial posture and position errors of a five-axis CNC machine tool. The system includes a memory and a processor. The memory stores a computer program. When the processor executes the computer program, it executes the method for real-time compensation of spatial posture and position errors of a five-axis CNC machine tool as described above.

[0038] The present invention also provides a computer-readable storage medium, which stores machine-executable instructions. When the machine-executable instructions are called and executed by a processor, the machine-executable instructions prompt the processor to implement the real-time compensation method for spatial posture and position errors of a five-axis CNC machine tool as described above.

[0039] In general, compared with the prior art, the above technical solution conceived by the present invention, the method and device for real-time compensation of spatial posture and position error of a five-axis CNC machine tool provided by the present invention mainly have the following beneficial effects:

[0040] 1. The present invention solves the posture error and position error compensation instructions step by step. Compared with the traditional compensation instruction solving method, it not only greatly improves the calculation efficiency, but also can better compensate for the tool posture error of the machine tool.

[0041] 2. Based on the differential motion relationship of each axis of the CNC machine tool and the forward kinematics model of the CNC machine tool, a spatial error model of the CNC machine tool is established to transfer the error terms of each axis as differential motion to the tool coordinate system.

[0042] 3. After the tool is compensated for posture error, a new position error will be generated due to the posture error compensation. Therefore, the final compensation amount includes the original position error and the new position error caused by the posture error compensation. When solving the compensation instruction, the compensation instruction should be solved step by step by first solving the posture error and then solving the linear error.

[0043] 4. Separate the singular part and the non-singular part of the compensation value of the attitude error, and use the damped inverse to replace the ordinary inverse of the singular part parameter, so that the compensation value can smoothly pass through the singular area.

[0044] 5. Take λ 2= 0.1 is used as the damping coefficient for subsequent calculations, because this value is a suitable intermediate value, which can not only coincide with the nearby non-singular interval compensation value quickly, but also pass through the singular interval relatively smoothly. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 It is a flow chart of a method for real-time compensation of spatial posture and position error of a five-axis CNC machine tool provided by the present invention;

[0046] Figure 2 It is a schematic diagram of error transmission of a five-axis machine tool involved in the present invention (taking a double-rotary table machine tool as an example);

[0047] Figure 3 It is a schematic diagram of the ideal and actual positions of the tool;

[0048] Figure 4 Schematic diagram of the effect of different damping coefficients on the singular interval, where (a), (b), (c), and (d) correspond to the damping coefficient λ 2 0.001, 0.01, 0.1 and 1;

[0049] Figure 5 It is a flow chart of the singular interval avoidance method based on the damping inverse;

[0050] Figure 6 is a schematic diagram of the PDGEs and PIGEs of a five-axis machine tool, where (a), (b), (c), and (d) correspond to the translational axis PDGEs, rotary axis PDGEs, translational axis perpendicularity error, and rotary axis PIGEs, respectively;

[0051] Figure 7 Schematic diagram of the working principle of the spatial error compensation system of a five-axis CNC machine tool according to an embodiment of the present invention;

[0052] Figure 8 Schematic diagram of the comparison of body diagonal errors before and after translation axis error compensation, where (a) and (b) correspond to the PPP body diagonal detection results and the NPP body diagonal detection results, respectively;

[0053] Fig. 9 It is a schematic diagram of the RTCP accuracy comparison before and after the rotary axis error compensation, where (a) and (b) correspond to the XYC axis linkage accuracy before and after compensation and the YZA axis linkage accuracy before and after compensation, respectively. DETAILED DESCRIPTION

[0054] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0055] See also Figure 1 The present invention provides a real-time compensation method for spatial posture and position errors of a five-axis CNC machine tool, and the compensation method mainly comprises the following steps:

[0056] S1, a spatial error model of the CNC machine tool is established based on the differential motion relationship of each axis of the CNC machine tool and the forward kinematics model of the CNC machine tool.

[0057] In this implementation, a dual-turret machine tool CAYXZ is taken as an example to establish a forward kinematic model of the machine tool. The ideal homogeneous coordinate transformation of each component of the machine tool represents its ideal motion relative to adjacent components. Assuming that the command positions of each axis of the machine tool are x, y, z, a, and c, respectively, from the perspective of the tool side kinematic chain, the ideal homogeneous coordinate transformation matrices of the Y axis relative to the machine tool coordinate system, the X axis relative to the Y axis, and the Z axis relative to the X axis coordinate system are:

[0058]

[0059] For the A-axis, the origin of the error analysis coordinate system does not coincide with the origin of the machine tool, which is determined by the RTCP (Rotation tool center point) parameter of the machine tool. Therefore, the rotation axis position offset matrix must be multiplied in the corresponding calculation. At the same time, since the rotation direction of the machine tool rotation axis is opposite to the rotation direction determined by the positive direction of the corresponding translation axis and the right-hand rule, the rotation angle in the ideal homogeneous transformation matrix takes a negative value; similarly, the origin of the C-axis coordinate system does not coincide with the origin of the A-axis coordinate system, and corresponding processing must also be performed.

[0060] Therefore, the homogeneous coordinate transformation of the A-axis relative to the machine tool coordinate system and the C-axis relative to the A-axis coordinate system is:

[0061]

[0062] Assuming that the worktable coordinate system coincides with the C-axis coordinate system, the transformation matrix between them is is the unit matrix, then the ideal homogeneous transformation matrix of the tool coordinate system relative to the worktable coordinate system is:

[0063]

[0064] At this point, the forward kinematics model of the machine tool has been established, so that the motion and error transmission paths of the machine tool can be known, such as Figure 2 shown.

[0065] The spatial error model of the machine tool is based on the motion transfer of forward kinematics, and the differential motion matrix can be calculated based on the homogeneous coordinate matrix. Differential motion includes micro-translation and micro-rotation, which is the motion of the error analysis coordinate system in six degrees of freedom. Corresponding to the basic error terms of each axis of the machine tool, the three position errors of the coordinate system can be regarded as micro-translation, and the three angular errors can be regarded as micro-rotation. Based on the differential motion vectors of each axis and the differential motion matrix relative to the tool coordinate system, the transfer relationship of the differential motion vectors of each axis to the tool coordinate system can be obtained:

[0066]

[0067] Among them, DJ[T t i ] represents the differential motion matrix from the i (i = X, Y, Z, A, C) axis coordinate system to the tool coordinate system; ΔE i Represents the differential motion vector of the i (i=X, Y, Z, A, C) axis.

[0068] The comprehensive error of the tool in its own coordinate system can be expressed as the sum of the errors of each axis transferred to the tool coordinate system:

[0069]

[0070] in, Indicates the comprehensive error of the tool in its own coordinate system; Indicates the error of each axis of the machine tool transferred to the tool coordinate system; δ it Represents the three position errors of the tool in its own coordinate system, ε it Indicates the three angular errors of the tool in its own coordinate system.

[0071] According to formula (6), the matrix representation of the tool comprehensive error in its own coordinate system can be given:

[0072]

[0073] Finally, the expression of tool position error and posture error in the worktable coordinate system can be obtained, that is, the expression of the spatial error model is:

[0074]

[0075] At this point, the spatial error model of the machine tool has been established based on the differential motion method.

[0076] S2, based on the spatial error model, first separate and extract the rotation error term from the comprehensive error term, and solve the compensation instruction for the rotation error term by using the pseudo-inverse matrix method to obtain the compensation instruction for the posture error.

[0077] Based on the established machine tool spatial error model, it is necessary to obtain the compensation instructions for each axis based on the inverse kinematic solution, so that the compensation instructions of each axis can compensate for the comprehensive tool posture error in the tool coordinate system after the differential motion transmission, so as to achieve the purpose of correcting the tool posture. When solving the compensation instructions, the commonly used method is: linearize the comprehensive tool error and compensation value based on the Jacobian matrix, and solve the compensation instructions through the pseudo-inverse matrix method. In practice, the compensation process can be optimized in terms of mechanism, and the compensation instructions can be solved step by step by solving the posture error first and then the linear error. For example Figure 3 The figure shows the principle diagram of tool position and attitude error. There is a position error between the ideal and actual posture of the tool. When the tool is compensated for the attitude error, a new position error caused by the attitude error compensation will be generated. Therefore, the final compensation amount includes the original position error and the new position error caused by the attitude error compensation. When solving the compensation instruction, the step-by-step compensation instruction should be solved by solving the attitude error first and then the linear error. Therefore, the rotation error term is first separated and extracted from the comprehensive error term, and the compensation instruction is solved for the rotation error term by solving the pseudo-inverse matrix method. The compensation values ​​of the A and C axes can be obtained, and the angle error can be compensated by using the compensation value.

[0078]

[0079] In the formula, S yz is the perpendicularity error between the Y-axis and the Z-axis, S xz is the perpendicularity error between the X-axis and the Z-axis, ε xx is the angular error of the X-axis around the X-axis, ε xy is the angular error of the Y axis around the X axis, ε xz is the angular error of the Z axis around the X axis, ε xa is the angular error of the A axis around the X axis, ε xc is the angular error of the C axis around the X axis, ε za is the angular error of the A axis around the Z axis, ε zc is the angular error of the C-axis around the Z-axis, ε yx is the angular error of the X-axis around the Y-axis, ε yy is the angular error of the Y axis around the Y axis, ε yz is the angular error of the Z axis around the Y axis, ε ya is the angular error of the A axis around the Y axis, ε yc is the angular error of the C-axis around the Y-axis.

[0080] S3, separates the singular part and the non-singular part of the compensation value of the attitude error, uses the damped inverse to replace the ordinary inverse of the singular part parameter, and then obtains a new attitude error compensation instruction to compensate for the attitude error of the CNC machine tool.

[0081] Based on step S2: posture error compensation instruction solution method, C-axis compensation value expression CE R2 There is a term 1 / sin(a), which will cause the machine tool compensation value to be uncontrollable when the A-axis command position a approaches 0°, that is, there is a singular point that makes the kinematic inverse solution unsolvable. Use S3: the damped inverse method described above to avoid the singular interval: separate the singular part from the non-singular part, and use the damped inverse method to replace the ordinary inverse of the singular part parameter, so that the compensation value can smoothly pass through the singular area. For the singular parameter k, if λ>0, then its damped inverse is k / (k 2 +λ 2 ), where λ is the damping coefficient of k. When the square of the damping inverse is 0.001, 0.01, 0.1, and 1, the simulation of the influence of the ordinary inverse and the damping inverse on the C-axis compensation value is performed respectively. At this time, each axis moves synchronously from its negative limit to the positive limit. The A-axis command position is the horizontal coordinate and the C-axis compensation value is the vertical coordinate. The simulation results are shown in Figure 4 As shown in the figure, it can be seen that the common feature of the damped inverse relative to the ordinary inverse is that when the singular parameter k increases continuously from a negative value to a positive value, in the singular interval (near the zero position of the A axis), the ordinary inverse simulation result tends to infinity, resulting in the planned axis compensation value being discontinuous and having a large mutation, while the damped inverse is less affected by the singular interval and can pass through the singular area more smoothly. Outside the singular area, the damped inverse simulation results are exactly the same as the ordinary inverse, indicating that it does not affect the motion compensation accuracy outside the singular area. As for the influence of the damping coefficient itself on the compensation value: when λ 2 The smaller the value, the faster the compensation value around the singular point can coincide with the non-singular interval, but the accuracy loss in the singular interval will be greater; when λ 2 When λ is larger, the speed at which the compensation value around the singular point coincides with the non-singular interval is slower, but the overall transition at the singular point is smoother. 2 = 0.1 is used as the damping coefficient for subsequent calculations, because this value is a suitable intermediate value, which can not only coincide with the nearby non-singular interval compensation value quickly, but also pass through the singular interval relatively smoothly. Figure 5 Shown is a flow chart of the singular interval avoidance method based on the damping inverse.

[0082] S4, subtracting the linear part of the translation axis error caused by the posture error compensation from the linear part of the comprehensive error in the initial tool coordinate system, that is, obtaining the translation axis error compensation instruction that needs to be compensated, so as to compensate the position error of the CNC machine tool.

[0083] The compensation value of the position error is divided into two parts: one is the translation axis error caused by the rotary axis error compensation, and the other is the original translation axis error. The translation axis error caused by the rotary axis error compensation can be calculated based on the differential motion relationship:

[0084]

[0085] Extract The linear error part in is recorded as Then we have:

[0086]

[0087] Subtract the linear part of the translation axis error caused by the rotary axis error compensation from the linear part of the comprehensive error in the initial tool coordinate system to obtain the translation axis error compensation instruction that needs to be compensated:

[0088]

[0089] According to the existing five-axis CNC machine tool geometric error measurement and identification scheme, 18 items of 6 position-related errors, 3 items of verticality errors, and 12 items of 6 position-related errors of each translation axis of the machine tool can be measured. Figure 6 The position-related error items among the 33 geometric error items obtained by measurement and identification are integrated into an error compensation table in the format of the axis command position in the first column and the error item value corresponding to the command position in the second column. The table is compatible with the output format of mainstream measuring instruments on the market and supports one-click import into the CNC system.

[0090] The specific calculation steps for the spatial error compensation value are as follows: Figure 7 As shown in the figure, after the user turns on the spatial error compensation function in the channel parameter interface of the CNC system and sets the starting position, spacing, number of points of the compensation table and the starting parameters stored in the spatial error compensation table, when the machine tool feed axis moves, the CNC system kernel can obtain the command position of each feed axis in the current interpolation cycle, and generate the error term of each axis at the current command position in a linear interpolation manner according to the error compensation table, and substitute it into the spatial error compensation calculation model for calculation. After obtaining the compensation value of each axis at a certain command position, the compensation value is stored in the interpolation output buffer, superimposed on the command position and output to the servo system, finally realizing the motion compensation of each axis.

[0091] The present invention also provides a system for real-time compensation of spatial posture and position errors of a five-axis CNC machine tool. The system includes a memory and a processor. The memory stores a computer program. When the processor executes the computer program, it executes the method for real-time compensation of spatial posture and position errors of a five-axis CNC machine tool as described above.

[0092] The present invention also provides a computer-readable storage medium, which stores machine-executable instructions. When the machine-executable instructions are called and executed by a processor, the machine-executable instructions prompt the processor to implement the real-time compensation method for spatial posture and position errors of a five-axis CNC machine tool as described above.

[0093] The present invention also provides a system for realizing the real-time compensation function of spatial posture and position error of the above-mentioned five-axis CNC machine tool, such as Figure 7 As shown, including:

[0094] Channel parameter import module: used to input the spatial error compensation function enable (the switching condition of the entire error compensation function), the machine tool mechanism chain (select the error compensation formula corresponding to the machine tool structure type according to this parameter), and the verticality error between the three translation axes.

[0095] Axis parameter import module: used to input the error compensation starting point coordinates (the system will output the compensation value only after this starting point coordinates), the number of error compensation points (corresponding to the number of measurement points in the compensation table, the command position error between nodes will be interpolated according to the error value at the node), the error compensation point spacing (representing the command spacing between compensation points), error compensation modulo enable (defines whether the compensation value is calculated according to the excess distance after exceeding the specified compensation range or directly outputs the compensation value of the nearest endpoint), error compensation multiplier (defines the output multiplier of the error compensation value), error compensation table starting parameter number (defines the offset of the starting position of the spatial error compensation table in the system, which is convenient for system addressing), compensation value output constraint related parameters (by constraining the compensation value by amplitude, change rate, etc., to ensure that the compensation value will not have unexpected sudden changes).

[0096] Error value import module: used to import the error compensation table, that is, the position-related error table of the machine tool. The data in the table can be used to parse out the error item name, compensation table starting point, compensation point number, compensation spacing and other information. These error compensation parameters can be filled into the corresponding parameter interface of the CNC system with one click.

[0097] Compensation value calculation module: Based on the geometric error terms obtained through measurement and identification, as well as the set channel parameter terms and axis parameter terms, the CNC system kernel obtains the command position of each feed axis in the current interpolation cycle, generates the error terms of each axis at the current command position through linear interpolation, and substitutes them into the compensation formula of the corresponding type of machine tool for calculation, and finally calculates the compensation value of each axis at the command position.

[0098] The compensation function module can be easily integrated into the existing CNC system without large-scale modification or upgrading of the CNC system. This feature significantly reduces the practical cost and avoids the additional economic cost and time delay caused by system upgrade. At the same time, since the interface used by the spatial error compensation is a universal interface of the CNC system, the present invention can be quickly applied to actual production, providing strong support for the spatial error compensation of machine tools.

[0099] The compensation function module takes the error compensation table parameters as input, calculates the compensation instructions of each axis in real time in the CNC system kernel and outputs them to the servo system. By automatically parsing the error compensation parameters according to the compensation table and other functions, the usability and work efficiency of the software are greatly improved, and the learning cost of users is also reduced. At the same time, for machine tools of different configurations, the corresponding error compensation formula can be selected through the input machine tool mechanism chain. This design enables the present invention to be applied to various mainstream CNC machine tools of various configurations on the market, greatly improving the competitiveness of the present invention.

[0100] Figure 8-9 The experimental results of the spatial posture and position error compensation method of a five-axis CNC machine tool according to an exemplary embodiment of the present invention are shown. Figure 8 As shown in the figure, the diagonal error measurement results of the translation axis body are performed three times when the translation axis compensation function is switched on and off. Fig. 9 As shown, the RTCP accuracy (characterized by the spherical center coordinate deviation data of the standard ball in the machine tool coordinate system) in the five-axis linkage process is obtained when the rotary axis compensation function is switched on and off.

[0101] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A real-time compensation method for spatial posture and position error of a five-axis CNC machine tool, characterized by: The method comprises the following steps: S1, establish the spatial error model of CNC machine tools based on the differential motion relationship of each axis of the CNC machine tool and the forward kinematics model of the CNC machine tool; S2, based on the spatial error model, firstly separate and extract the rotation error term from the comprehensive error term, and solve the compensation instruction of the rotation error term by the method of solving the pseudo-inverse matrix to obtain the compensation instruction of the attitude error; S3, separating the singular part and the non-singular part of the compensation value of the attitude error, using the damped inverse to replace the ordinary inverse of the singular part parameter, and then obtaining a new attitude error compensation instruction to compensate the attitude error of the CNC machine tool; S4, subtracting the linear part of the translation axis error caused by the posture error compensation from the linear part of the comprehensive error in the initial tool coordinate system, that is, obtaining the translation axis error compensation instruction that needs to be compensated, so as to compensate the position error of the CNC machine tool.

2. The method for real-time compensation of spatial posture and position error of a five-axis CNC machine tool according to claim 1, characterized in that: Assuming that the command positions of the machine tool axes are x, y, z, a, and c, respectively, from the perspective of the tool side kinematic chain, the ideal homogeneous coordinate system transformation matrices of the Y axis relative to the machine tool coordinate system, the X axis relative to the Y axis, and the Z axis relative to the X axis coordinate system are: The homogeneous coordinate transformation of the A-axis relative to the machine tool coordinate system and the C-axis relative to the A-axis coordinate system is:

3. The method for real-time compensation of spatial posture and position error of a five-axis CNC machine tool according to claim 2, characterized in that: The ideal homogeneous transformation matrix of the tool coordinate system relative to the worktable coordinate system is: Based on the differential motion vector of each axis and the differential motion matrix relative to the tool coordinate system, the transfer relationship from the differential motion vector of each axis to the tool coordinate system is obtained: Among them, DJ[T t i ] represents the differential motion matrix from the i-axis coordinate system to the tool coordinate system; ΔE i Represents the differential motion vector of the i-axis; i=X, Y, Z, A, C.

4. The method for real-time compensation of spatial posture and position error of a five-axis CNC machine tool according to claim 3, characterized in that: The comprehensive error of the tool in its own coordinate system is expressed as the sum of the errors of each axis transferred to the tool coordinate system: in, Indicates the comprehensive error of the tool in its own coordinate system; Indicates the error of each axis of the machine tool transferred to the tool coordinate system; δ it Represents the three position errors of the tool in its own coordinate system, ε it Indicates the three angular errors of the tool in its own coordinate system; According to formula (6), the matrix representation of the tool comprehensive error in its own coordinate system is given as: Finally, the expression of the spatial error model is obtained as follows:

5. The method for real-time compensation of spatial posture and position error of a five-axis CNC machine tool according to claim 1, characterized in that: First, the rotation error term is separated and extracted from the comprehensive error term, and the compensation instruction of the rotation error term is solved by the method of finding the pseudo-inverse matrix to obtain the compensation values ​​of the A and C axes, so as to compensate the angle error using the compensation values: In the formula, S yz is the perpendicularity error between the Y-axis and the Z-axis, S xz is the perpendicularity error between the X-axis and the Z-axis, ε xx is the angular error of the X-axis around the X-axis, ε xy is the angular error of the Y axis around the X axis, ε xz is the angular error of the Z axis around the X axis, ε xa is the angular error of the A axis around the X axis, ε xc is the angular error of the C axis around the X axis, ε za is the angular error of the A axis around the Z axis, ε zc is the angular error of the C-axis around the Z-axis, ε yx is the angular error of the X-axis around the Y-axis, ε yy is the angular error of the Y axis around the Y axis, ε yz is the angular error of the Z axis around the Y axis, ε ya is the angular error of the A axis around the Y axis, ε yc is the angular error of the C-axis around the Y-axis.

6. The method for real-time compensation of spatial posture and position error of a five-axis CNC machine tool according to claim 1, characterized in that: Take λ 2 = A value near 0.1 is taken as the damping coefficient.

7. The method for real-time compensation of spatial posture and position error of a five-axis CNC machine tool according to claim 3, characterized in that: The translation axis error caused by the rotary axis error compensation is calculated based on the differential motion relationship: Extract The linear error part in is recorded as Then we have:

8. The method for real-time compensation of spatial posture and position error of a five-axis CNC machine tool according to claim 7, characterized in that: Subtract the linear part of the translation axis error caused by the rotary axis error compensation from the linear part of the comprehensive error in the initial tool coordinate system to obtain the translation axis error compensation instruction that needs to be compensated:

9. A five-axis CNC machine tool spatial posture and position error real-time compensation system, characterized by: The system includes a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, the method for real-time compensation of spatial posture and position error of a five-axis CNC machine tool according to any one of claims 1 to 8 is executed.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores machine-executable instructions. When the machine-executable instructions are called and executed by the processor, the machine-executable instructions prompt the processor to implement the real-time compensation method for spatial posture and position errors of a five-axis CNC machine tool as described in any one of claims 1-8.

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