Multi-model-based machining path interpolation CNC system and machine tool

Abstract

The present invention discloses a multi-model-based machining path interpolation numerical control system and a machine tool, including: a memory for acquiring and storing machining path information and interpolated stepping information; an interpolator for performing iterative interpolation of geometry and machining speed by reading the machining path information from the memory based on a selected interpolation strategy; wherein the interpolation strategy includes: performing interpolation on the host computer, performing interpolation on the slave computer, and performing rough interpolation on the host computer and fine interpolation on the slave computer; an inverse solver for inversely solving and calculating the position information of each physical axis from the tool point position and tool axis vector direction of the interpolated tool point and storing it; a driver for generating and outputting motion control and / or IO control commands to drive each axis of the machine tool and supporting equipment to work. Through accurate tool point trajectory models, tool axis point trajectory models, and correlation functions between tool points and tool axis points, high-precision machining path control can be achieved based on different interpolation strategies, thereby improving the machining accuracy of machined parts.

Description

Technical Field

[0001] The present invention belongs to the technical field of machining, and particularly relates to a multi-model-based machining path interpolation numerical control system and a machine tool. Background Art

[0002] Machining equipment in the machining field usually adopts a numerical control system. After the machining path and process planning are carried out in CAM software, the generated machining program is usually input into the numerical control system in the format of G and M codes. The machining of complex mechanical parts usually needs to be machined on a machining center through multi-axis machining processes such as turning, milling, and drilling. The engine impeller is a typical complex part, and impellers are widely used in the fields of energy, aviation, and navigation.

[0003] A five-axis machining program usually includes linear motion (G1) and circular motion (G2) of the tool center point in three-dimensional space. Here, the linear motion or circular motion refers to the motion trajectory of the tool center point, and the direction of the tool axis is expressed in the NC program in the following two ways. One way is to adopt the three components of the tool axis vector. Another way is to adopt the angles of the two rotating axes of a five-axis machine tool.

[0004] Before interpolation of an NC program expressed by the rotation axis angles, it generally needs to be converted into an NC program expressed by the tool axis vector by using a kinematic algorithm. After the NC program expressed by the tool axis vector is imported into the numerical control system, interpolation calculation needs to be performed on the program in the interpolator of the numerical control system. Because the interpolator of the numerical control system only has the mathematical model parameters of the tool center point line segment (such as the radius and direction of an arc line segment) and the information of the tool axis vector at the starting point and the ending point of the line segment. When the interpolator performs interpolation calculation on the line segment model, there is a lack of a reasonable method for interpolating the tool axis vector. An approximate method is to find a point on each of the tool axis vectors at the starting point and the ending point of the line segment, and then perform dense interpolation on the connection line of these two points. The number of interpolation points is the same as that of the tool center point trajectory line segment, and the connection line direction of the corresponding interpolation points of the two is used as the interpolated tool axis vector. See Figure 5 Obviously, there is a bow height error between the shape of the workpiece machined in this way and the original conical surface, and for workpieces with higher precision requirements, the existing methods are difficult to meet the requirements. Summary of the Invention

[0005] To solve the above problems, the purpose of the present invention is to provide a multi-model-based machining path interpolation numerical control system and a machine tool, which can achieve high-precision machining path control based on different interpolation strategies through an accurate tool center point trajectory model, a tool axis point trajectory model, and a correlation function between the tool center point and the tool axis point, thereby improving the machining accuracy of the machined part.

[0006] The technical solution provided by the present invention is: A multi-model-based machining path interpolation numerical control system, comprising:

[0007] A memory that acquires and stores machining path information and interpolated stepping information, where the machining path information at least includes a tool point locus model, a tool axis point locus model, and a correlation function between the tool point and the tool axis point; wherein, the tool point locus curve is associated with the curve along the machining surface, and the tool axis point locus curve is associated with the curve along the lower edge of the machining surface;

[0008] An interpolator that performs iterative interpolation of geometry and machining speed by reading the machining path information from the memory based on a selected interpolation strategy. The geometric interpolation densifies and decomposes each segment of the machining path on the machining path into interpolation steps according to the tool point locus model, the tool axis point locus model, and the correlation function, arranges the data of all interpolation steps into a tool point list in the machining order, and then sets the machining speed, and sets the machining speed based on the interpolated tool points after geometric interpolation; wherein the interpolation strategy includes: performing interpolation on the host computer, performing interpolation on the slave computer, and performing rough interpolation on the host computer and fine interpolation on the slave computer;

[0009] An inverse solver that inversely calculates and stores the position information of each physical axis from the tool point position and the tool axis vector direction of the interpolated tool points;

[0010] A driver that generates and outputs motion control and / or IO control commands to drive each axis of the machine tool and supporting equipment to work.

[0011] Preferably, the interpolation strategy of performing interpolation on the host computer further includes the host computer performing the following steps:

[0012] The interpolation module of the host computer obtains the machining path information, including the tool point locus model, the tool axis point locus model, and the correlation function between the tool point and the tool axis point, by sharing memory with the CAM module; or transfers the modeling parameters of the above models from the CAM module to the interpolation module in a data interaction manner, and then restores the modeling parameters to a mathematical model; the above data interaction manner can adopt a text file interaction manner;

[0013] Determine the interpolation step size according to the interpolation period and / or control accuracy and / or theoretical machining speed;

[0014] Divide the tool point locus curve of the machining path segment by using the interpolation step size to obtain interpolated tool points;

[0015] Determine the corresponding interpolation points on the tool axis point locus model based on the correlation function between the tool point and the tool axis point, and obtain the interpolated tool axis point coordinates and tool axis vector information corresponding to the interpolated tool points;

[0016] Store the interpolated tool point coordinates and tool axis vector data information into an interpolation step list.

[0017] Preferably, the interpolation strategy for interpolation on the host computer further includes the host computer performing the following steps:

[0018] Based on the acceleration limit and / or the acceleration / deceleration model, with the theoretical machining speed on the tool point path segment as the maximum value, starting from the theoretical machining speed at the end points of the path segment, and aiming to obtain a continuous and smooth machining speed, gradually adjust the theoretical machining speed corresponding to each interpolation tool point in both directions towards the midpoint of the path segment;

[0019] And / or, add zero-length line segments at the end points of the path segment to set the changes in the theoretical machining speed and the tool axis vector at the end points of the path segment; where the theoretical machining speed of the zero-length line segment is used for the above-mentioned adjustment of the machining speed.

[0020] Preferably, the interpolation strategy for interpolation on the slave computer further includes the slave computer performing the following steps:

[0021] The machining path segment is stored in the memory of the slave computer in the form of code, and the code contains the machining path model modeling parameter information. Each time the code parser of the slave computer fetches N lines of code from the memory and converts them into a machining path segment array, and inputs the array into the interpolator module. At the same time, the interpolator module obtains the interpolation cycle and the acceleration / deceleration model;

[0022] Restore the modeling parameter information of each machining path segment code to the tool point trajectory mathematical model, the tool axis point trajectory mathematical model, and the correlation function between the tool point and the tool axis point;

[0023] Determine the interpolation step size, and divide the tool point trajectory model of the machining path segment according to the interpolation step size to obtain interpolation tool points, where for the zero-length line segment, divide the arc angle of the tool axis direction change;

[0024] Determine the corresponding interpolation points on the tool axis point trajectory model through the correlation function between the tool point and the tool axis point, obtain the interpolation tool axis point coordinates and the tool axis vector information, and store the interpolation tool point coordinates and the tool axis vector data information in an interpolation step list.

[0025] Preferably, the interpolation strategy for interpolation on the slave computer further includes the slave computer performing the following steps:

[0026] Based on the acceleration / deceleration mode, the interpolator uses the theoretical machining speed on the tool point path segment as the maximum value, starts from the theoretical machining speed at the end points of the path segment, and aims to obtain a continuous and smooth machining speed, and gradually adjusts the theoretical machining speed corresponding to each interpolation tool point in both directions towards the midpoint of the path segment.

[0027] Preferably, for rough interpolation on the host computer and fine interpolation on the slave computer, it further includes the host computer performing the following steps:

[0028] The rough interpolation module of the host computer obtains the machining path information by sharing memory with the CAM module, including the tool point trajectory model, the tool axis point trajectory model, and the correlation function between the tool point and the tool axis point; or transfers the modeling parameters of the above models from the CAM module to the rough interpolation module by means of data interaction, and then restores the modeling parameters to a mathematical model; the above data interaction method can adopt the text file interaction method;

[0029] Determine the theoretical rough interpolation step length according to the rough interpolation accuracy, divide the arc length of each line segment in the machining path line segment list by the theoretical rough interpolation step length, and round up to N, and divide the arc length of the line segment by N to obtain the actual rough interpolation step length L;

[0030] Use the actual interpolation step length L to divide the line segment, first equally divide the tool point trajectory model to obtain the interpolated tool points;

[0031] Find the interpolation points on the tool axis point trajectory model through the correlation function between the tool point and the tool axis point, and obtain the tool axis vector information corresponding to the interpolated tool points;

[0032] Store the sub-list of N line segments generated after rough interpolation of a single path line segment into the machining path line segment list to replace the line segment before interpolation; where the speed of each line segment in the sub-list is the same as the speed of the line segment before interpolation;

[0033] And / or, at the places where the speed of adjacent line segments changes suddenly and the movement direction changes suddenly, adjust the speed of the adjacent line segments with the goal of speed smoothing.

[0034] Preferably, the rough interpolation on the host computer and the fine interpolation on the lower computer further include the following steps executed on the lower computer:

[0035] The fine interpolation module of the lower computer obtains the information of the machining path line segment list after rough interpolation by sharing memory with the rough interpolation module of the host computer, including the tool point trajectory model, the tool axis point trajectory model, and the correlation function information between the tool point and the tool axis point; or transfers the modeling parameters of the above models from the rough interpolation module to the fine interpolation module by means of data interaction, and then restores the modeling parameters to a mathematical model; the above data interaction method can adopt the text file interaction method;

[0036] Wherein, if the modeling parameters of the above models are transferred from the rough interpolation module to the fine interpolation module by means of data interaction, the machining path line segments are stored in the memory of the lower computer in the form of codes, the codes contain the machining path model modeling parameter information, the code parser of the lower computer takes out N lines of codes from the memory each time and converts them into a machining path line segment array, and inputs the array into the fine interpolator module, and at the same time the fine interpolator module obtains the interpolation period and the acceleration and deceleration model;

[0037] Restore the modeling parameter information of each machining path segment code to the tool point trajectory mathematical model, the tool axis point trajectory mathematical model, and the correlation function between the tool point and the tool axis point;

[0038] Determine the fine interpolation step size, and segment the tool point trajectory model of the machining path according to the fine interpolation step size to obtain the fine interpolation tool points. For zero-length line segments, segment the arc angle of the tool axis direction change;

[0039] Determine the corresponding interpolation points on the tool axis point trajectory model through the correlation function between the tool point and the tool axis point, obtain the interpolation tool axis point coordinates and tool axis vector information, and store the interpolation tool point coordinates and tool axis vector data information in an interpolation step array.

[0040] Preferably, the rough interpolation on the host computer and the fine interpolation on the slave computer further include:

[0041] The host computer performs the following steps:

[0042] The host computer generates and outputs a machining program for the list data obtained after rough interpolation, and sends it to the slave computer;

[0043] The slave computer performs the following steps:

[0044] Obtain the machining program and perform the fine interpolation operation. After fine interpolation, perform speed smoothing processing;

[0045] Import the inverse solver. The inverse solver calculates the position information of each physical axis from the tool point coordinates and tool axis vector information of the interpolation tool points according to the machine tool inverse kinematics algorithm.

[0046] Preferably, add zero-length line segments at the endpoints of the path segments to set the theoretical machining speed and the change information of the tool axis vector at the endpoints of the path segments; the theoretical machining speed of the zero-length line segment is used for the above-mentioned machining speed adjustment.

[0047] Preferably, when performing interpolation control for a flexible tool, calculate the offset amount that needs to be compensated in reverse based on the prediction mathematical model and the preset process parameters, and optimize the offset initial tool axis vector according to the offset amount to effectively compensate for the errors brought during the machining process:

[0048] Call the first prediction mathematical model, calculate the trailing amount generated by cutting the workpiece according to the target parameter information of the current position point, and then calculate the first angle that needs to swing along the cutting feed direction for reverse compensation;

[0049] Obtain the first component of the initial tool axis vector along the cutting feed direction, and perform the first optimization according to the first angle to obtain the second component result of the optimized tool axis vector along the cutting feed direction;

[0050] Call the second prediction mathematical model, calculate the lateral taper generated by cutting the workpiece according to the target parameter information of the current position point, and then calculate the second angle that needs to swing in the vertical direction along the cutting feed direction for reverse compensation;

[0051] Obtain the third component of the initial tool axis vector in the vertical direction along the cutting feed direction, and perform a second optimization according to the second angle to obtain the result of the fourth component of the optimized tool axis vector perpendicular to the cutting feed direction;

[0052] Synthesize the final optimized tool axis vector according to the values of the second component and the fourth component.

[0053] Preferably, when performing interpolation control for a rigid tool, it is judged whether the initial tool axis vector is deformed by force during the process of generating a machining path according to the initial tool axis vector and the workpiece model and performing machining. When the initial tool axis vector is deformed by force during the machining path, calculate the tool force deformation amount that needs to be compensated in reverse according to the machining feature data collected in real time, obtain the tool diameter, the force applied to the tool, and the tool protrusion length, and calculate the tool force deformation amount δ according to the tool force deformation amount formula;

[0054] Optimize the deformed initial tool axis vector according to the tool force deformation amount of the reverse compensation to effectively compensate the errors brought during the machining process, and obtain the optimal tool axis vector;

[0055] Among them, the machining feature data of the rigid tool includes three cutting elements, the surface morphology features of the machined surface, machine tool errors, and data related to the machining process.

[0056] Based on the same concept, the present invention also provides a machine tool, including the multi-model-based machining path interpolation numerical control system described in any one of the above.

[0057] Due to the adoption of the above technical solutions, the present invention has the following advantages and positive effects compared with the prior art:

[0058] 1. The present invention can achieve high-precision machining path control through an accurate tool point locus model, a tool axis point locus model, and a correlation function between the tool point and the tool axis point, thereby improving the dimensional accuracy and surface quality of the machined part. The interpolator can perform iterative interpolation of geometry and machining speed based on the machining path information, optimize the machining path, reduce unnecessary movements, and improve machining efficiency. The interpolator provides a variety of interpolation strategies, including interpolation on the host computer, interpolation on the slave computer, and rough interpolation on the host computer and fine interpolation on the slave computer, which can adapt to different machining requirements and machine tool performance, and improve the flexibility and applicability of machining. Setting the machining speed based on the interpolated tool points after geometric interpolation can dynamically adjust the speed according to the geometric characteristics and process requirements of the machining path, and optimize the machining process. The inverse solver can calculate the position information of each physical axis based on the position of the interpolated tool point and the direction of the tool axis vector, ensuring the coordinated movement of each axis during the machining process and improving machining accuracy.

[0059] 2. The present invention obtains accurate machining path information through shared memory or data interaction methods, ensuring accurate control of the tool point and the tool axis point. At the same time, the use of the correlation function between the tool point and the tool axis point ensures their coordinated movement during the machining process, which is particularly important for complex machining tasks. When adopting the interpolation strategy on the host computer, the interpolation calculation can be implemented in the CAM module. In this way, a three-dimensional model of the workpiece can be obtained during interpolation, and non-linear errors will not occur due to the lack of a three-dimensional model of the workpiece during interpolation. The correlation function can also be easily obtained; the interpolation calculation can also be implemented outside the CAM module, but some model data will be missing, such as the correlation function, etc.; due to the non-real-time nature of the interpolation calculation on the host computer, very complex calculations can be performed without worrying about being limited by the interpolation cycle due to a large amount of calculations. The look-ahead in traditional numerical control is infinitely magnified. The look-ahead of the N-line program in traditional numerical control can be extended to the look-ahead of the entire machining program, and reverse look-ahead can also be performed, which is beneficial to ensuring the continuity and smooth change of speed, acceleration, and process parameters within the global scope. The slave computer does not need to perform interpolation calculations (except for necessary real-time interpolation). The algorithm module of the slave computer can be relatively simple, reducing hardware costs, improving reliability and stability, and even not requiring an industrial control computer. The interpolation algorithm is placed in the software of the host computer, which is beneficial to debugging, updating, upgrading, and maintenance.

[0060] 3. When adopting the strategy of rough interpolation by the host computer and fine interpolation by the slave computer, through rough interpolation on the host computer, the present invention can reduce the computational burden of fine interpolation by the slave computer. The rough interpolation algorithm is placed in the software of the host computer, which is easy to debug, update, upgrade, and maintain. The amount of data after rough interpolation is much smaller than that of interpolation on the host computer, and the requirement for the stability of data transmission between the host computer and the slave computer is low. For the processing technology that requires real-time acquisition of various feedback signals and adjustment of processing data, it has good real-time performance and is relatively easy to meet the requirements of high-speed and high-precision. The fine interpolation performed by the slave computer is based on the rough interpolation result of the host computer, further refining the processing path. By restoring the modeling parameter information to a mathematical model and considering the association between the tool position point and the tool axis point in fine interpolation, more accurate trajectory planning is achieved. The fine interpolation module of the slave computer can efficiently process the data after rough interpolation, reducing the data processing time and improving the processing efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] The following further elaborates on the specific implementation manners of the present invention in conjunction with the drawings, where:

[0062] Figure 1 is a schematic diagram of the composition of the numerical control system for machining path interpolation based on multiple models of the present invention;

[0063] Figure 2 is a schematic diagram of the interpolation process of the host computer of the present invention;

[0064] Figure 3 is a schematic diagram of the interpolation process of the slave computer of the present invention;

[0065] Figure 4 is a schematic diagram of the process of rough interpolation on the host computer and fine interpolation on the slave computer of the present invention;

[0066] Figure 5 is a schematic diagram of the bow height error generated by a two-axis swing head of a five-axis water jet cutting machine tool in the prior art;

[0067] Figure 6 is an example of the tool position point path and the theoretical machining speed;

[0068] Figure 7 is an example of the speed distribution after interpolation. DETAILED DESCRIPTION OF THE INVENTION

[0069] The present invention will be further described in detail below in conjunction with the drawings and specific embodiments. According to the following description and the claims, the advantages and features of the present invention will be clearer. It should be noted that the drawings are all in a very simplified form and use non-precise ratios, only for the purpose of facilitating and clearly assisting in explaining the objectives of the embodiments of the present invention.

[0070] It should be noted that all the directional indications (such as up, down, left, right, front, back...) in the embodiments of the present invention are only used to explain the relative positional relationship and movement conditions between components in a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indications will also change accordingly.

[0071] The first embodiment

[0072] See Figure 1 , this embodiment provides a multi-model-based machining path interpolation numerical control system, including:

[0073] A memory that acquires and stores machining path information and interpolated stepping information. The machining path information at least includes a tool point trajectory model, a tool axis point trajectory model, and a correlation function between the tool point and the tool axis point. Among them, the tool point trajectory curve is associated with the curve along the machining surface, and the tool axis point trajectory curve is associated with the curve along the lower edge of the machining surface;

[0074] An interpolator that reads the machining path information from the memory based on a selected interpolation strategy for iterative interpolation of geometry and machining speed. The geometric interpolation densifies and decomposes each section of the machining path on the machining path into interpolation steps according to the tool point trajectory model, the tool axis point trajectory model, and the correlation function, arranges the data of all interpolation steps into a tool point list in the machining order, and then sets the machining speed, and sets the machining speed based on the interpolated tool points after geometric interpolation. The interpolation strategies include: interpolation on the host computer, interpolation on the slave computer, and rough interpolation on the host computer and fine interpolation on the slave computer;

[0075] An inverse solver that inversely calculates and stores the position information of each physical axis from the tool point position and the tool axis vector direction of the interpolated tool points;

[0076] A driver that generates and outputs motion control and / or IO control commands to drive each axis of the machine tool and supporting equipment to work.

[0077] The technical solution of this embodiment can achieve high-precision machining path control through an accurate tool point trajectory model, a tool axis point trajectory model, and a correlation function between the tool point and the tool axis point, thereby improving the dimensional accuracy and surface quality of the machined part. The interpolator can perform iterative interpolation of geometry and machining speed according to the machining path information, optimize the machining path, reduce unnecessary movements, and improve machining efficiency. The interpolator provides a variety of interpolation strategies, including interpolation on the host computer, interpolation on the slave computer, and a strategy of rough interpolation on the host computer and fine interpolation on the slave computer, which can adapt to different machining requirements and machine tool performance, and improve the flexibility and applicability of machining. The machining speed is set based on the interpolated tool point after geometric interpolation, and the speed can be dynamically adjusted according to the geometric characteristics and process requirements of the machining path to optimize the machining process. The inverse solver can calculate the position information of each physical axis based on the position of the interpolated tool point and the direction of the tool axis vector to ensure the coordinated movement of each axis during the machining process and improve machining accuracy.

[0078] Preferably, referring to Figure 2 , the interpolation strategy of interpolating on the host computer further includes the following steps executed on the host computer:

[0079] The interpolation module of the host computer obtains the machining path information, including the tool point trajectory model, the tool axis point trajectory model, and the correlation function between the tool point and the tool axis point, by sharing memory with the CAM module; or transfers the modeling parameters of the above models from the CAM module to the interpolation module in the form of data interaction, and then restores the modeling parameters to a mathematical model; the above data interaction method can adopt a text file interaction method;

[0080] Determine the interpolation step according to the interpolation period and / or control accuracy and / or theoretical machining speed;

[0081] Divide the tool point trajectory curve of the machining path segment by using the interpolation step to obtain the interpolated tool points;

[0082] Based on the correlation function between the tool point and the tool axis point, determine the corresponding interpolation points on the tool axis point trajectory model, and obtain the interpolated tool axis point coordinates and tool axis vector information corresponding to the interpolated tool points;

[0083] Store the interpolated tool point coordinates and tool axis vector data information in an interpolation step list.

[0084] The technical solution of this embodiment obtains accurate machining path information through shared memory or data interaction methods, ensuring accurate control of the tool point and tool axis point. At the same time, the use of the correlation function between the tool point and the tool axis point guarantees the coordinated movement of the two during the machining process, which is particularly important for complex machining tasks. When adopting the strategy of host computer interpolation, the interpolation calculation can be implemented in the CAM module. In this way, the three-dimensional model of the workpiece can be obtained during interpolation, and non-linear errors will not be caused due to the lack of the three-dimensional model of the workpiece during interpolation. Moreover, the correlation function can be easily obtained. The interpolation calculation can also be implemented outside the CAM module, but some model data will be missing in this case, such as the correlation function, etc. Due to the non-real-time nature of the interpolation calculation by the host computer, very complex calculations can be carried out without worrying about being limited by the interpolation cycle due to a large amount of calculation. The look-ahead in traditional numerical control is infinitely amplified. The look-ahead of the N-line program in traditional numerical control can be extended to the look-ahead of the entire machining program, and backward look-ahead is also possible, which is beneficial to ensuring the continuity and smooth change of speed, acceleration, and process parameters within the global scope. The lower computer does not need to perform interpolation calculations (except for necessary real-time interpolation). The algorithm module of the lower computer can be relatively simple, reducing the hardware cost, improving the reliability and stability, and even eliminating the need for an industrial control computer. The interpolation algorithm is placed in the software of the host computer, which is beneficial to debugging, updating, upgrading, and maintenance.

[0085] Inside the CAM software, each segment of the generated machining path can be expressed by a C++ class Entity, and the entire machining path can be represented by a list of Entity objects in C++. <entity>It can be expressed. The machining line, the cutting-in and cutting-out lines, the rapid approach line, etc. can be distinguished by the class member machining quality level m_dQuality. For example, 1 - 5 represents the 5th level of machining quality, 9 represents cutting-in and cutting-out, 10 represents rapid approach during idle stroke, and 13 represents the transition line during idle stroke. If the interpolation module is placed inside the CAM software, the interpolation module can directly obtain the above path information. An example of the class Entity is as follows:

[0086]

[0087]

[0088]

[0089] Specifically, if the interpolation module is placed outside the CAM software but on the same computer, the interpolation module can obtain the above path information through shared memory. If not on the same computer, the machining path information can be expressed using a text file. For example, the following example uses three lines (which can also be combined into one line, and the three lines are for convenient reading and viewing) in a text file to express the information of a machining path segment. The entire machining path is a combination of the information of the above single-segment machining path segments.

[0090] The first line: m_nEntityNo, m_dQuality, m_dThickness, m_nOffset

[0091] The second line: m_nEntityType_TCP, m_EPt_TCP_X, m_EPt_TCP_Y, m_EPt_TCP_Z, m_dRadius_TCP, m_dLength_TCP, {P; K, X, Y, Z, R; K, X, Y, Z, R; K, X, Y, Z, R;...; K, X, Y, Z, R}

[0092] The third line: m_nEntityType_Axis, m_EPt_Axis_X, m_EPt_Axis_Y, m_EPt_Axis_Z, m_dRadius_Axis, m_dLength_Axis, {P; K, X, Y, Z, R; K, X, Y, Z, R; K, X, Y, Z, R;...; K, X, Y, Z, R}

[0093] The parameters in the first line are the general parameters of this path segment, and the definition can be referred to the example of the above Entity class.

[0094] The parameters in the second line, except for those within {}, can also refer to the definition in the above example of the Entity class. There are only parameters within {} when m_nEntityType_TCP is 4. The parameters within {} represent the parameters of the tool point NURBS spline curve (P is the degree of the NURBS spline curve, K is the knot vector parameter, X / Y / Z are the coordinates of the control points, R is the weight of the control point, and the number of knot vector parameters should be equal to the number of control points plus the degree P).

[0095] The parameters in the third line, except for those within {}, can also refer to the definition in the above example of the Entity class. There are only parameters within {} when m_nEntityType_Axis is 4. The parameters within {} represent the parameters of the tool axis point NURBS spline curve (P is the degree of the NURBS spline curve, K is the knot vector parameter, X / Y / Z are the coordinates of the control points, R is the weight of the control point, and the number of knot vectors should be equal to the number of control points plus the degree P).

[0096] The first line of the text file should give the tool point and tool axis point information at the origin of the machining path: m_StartPt_TCP_X, m_StartPt_TCP_Y, m_StartPt_TCP_Z, m_StartPt_Axis_X, m_StartPt_Axis_Y, m_StartPt_Axis_Z.

[0097] Passed to the interpolation module through the above text file, the interpolation module should first import the path information in the text file into a list of Entities list <entity>and restore the modeling parameters representing straight lines, arcs, and spline curves to a mathematical model.

[0098] Preferably, the interpolation strategy for performing interpolation on the host computer further includes the host computer executing the following steps:

[0099] Based on the acceleration limit and / or the acceleration-deceleration model, with the theoretical machining speed on the tool path segment as the maximum value, starting from the theoretical machining speed at the end points of the path segment, and aiming to obtain a continuous and smooth machining speed, gradually adjust the theoretical machining speed corresponding to each interpolation tool position point in both directions towards the midpoint of the path segment;

[0100] and / or, add a zero-length segment at the end points of the path segment to set the changes in the theoretical machining speed and the tool axis vector at the end points of the path segment; where the theoretical machining speed of this zero-length segment is used for the above-mentioned adjustment of the machining speed.

[0101] The technical solution of this embodiment can achieve continuous and smooth changes in the machining speed by adjusting the theoretical machining speed based on the acceleration limit and the acceleration-deceleration model, reduce the impact and vibration during the machining process, and improve the machining quality. The smooth speed change reduces the wear of the machine tool and the tool, and extends the service life of the equipment. By gradually adjusting the theoretical machining speed in both directions towards the midpoint of the path segment, the ideal machining speed can be reached faster, improving the machining efficiency. Adding a zero-length segment at the end points of the path segment to set the theoretical machining speed makes it convenient to set the acceleration and deceleration near this point during interpolation.

[0102] During speed interpolation, according to the acceleration limit of the machine, the acceleration limit of a specific process, and the acceleration-deceleration model, with the theoretical machining speed on the tool path as the target, starting from the theoretical machining speed at the path end points, gradually adjust the theoretical machining speed corresponding to each interpolation tool position point in both directions towards the midpoint of the path to obtain a continuous and smooth machining speed.

[0103] The acceleration-deceleration model such as trapezoidal acceleration-deceleration, trigonometric function acceleration-deceleration, exponential acceleration-deceleration, S-shaped curve acceleration-deceleration, cubic polynomial acceleration-deceleration, etc., Figure 6 is an example of a tool path of a tool position point, with different theoretical machining speeds in different path segments. Figure 7 is an example of the speed distribution after interpolation. Here, the simplest trapezoidal acceleration-deceleration is adopted. Adopting the S-shaped curve acceleration-deceleration or other acceleration-deceleration models can improve its speed smoothness. Since acceleration and deceleration require time, for a relatively short path segment, the theoretical machining speed may not necessarily be reached. In this step of speed interpolation, the interpolation information is saved in (m_dSpeed, m_bDelay, m_sDelay), where the delay amount Delay is calculated from m_dSpeed and m_dLength.

[0104] The present invention adopts an iterative interpolation method, that is, based on the introduced tool point locus curve, tool axis point locus curve, the correlation function between tool point and tool axis point, process parameter model, etc., geometric interpolation is first performed, and then the speed is set for the short line segments after interpolation. Here, a speed model that can adapt to the continuous change of line segment characteristics (such as the change of motion direction) is required. When performing the next process parameter interpolation, a set of process parameter models (such as cutting seam taper model, trailing amount model, etc.) that can adapt to the change of line segment characteristics and the continuous change of speed are required. Therefore, in the whole machining program, the process parameters can follow the actual working conditions, and the interpolation accuracy is higher.

[0105] Preferably, before performing speed interpolation, geometric interpolation is also performed. Each section of the machining path is densified and decomposed into interpolation steps, and the data of all interpolation steps are arranged in a list according to the machining order. The steps are as follows:

[0106] a. Determine the interpolation step size. The first method: calculate the interpolation step size according to an interpolation cycle and the theoretical machining speed; the second method: determine the interpolation step size according to the control accuracy, and then calculate the number of interpolation cycles required for this interpolation step size according to the interpolation cycle and the theoretical machining speed; for a zero-length line segment (joint point), the interpolation step size refers to the arc angle of the tool axis direction change within an interpolation cycle or the arc angle determined according to the arc angle control accuracy.

[0107] b. Use the interpolation step size to divide the tool point (TCP) locus curve of the machining path to obtain the interpolated tool points. For a zero-length line segment (joint point), the arc angle of the tool axis direction change can also be divided.

[0108] c. Find the interpolation points on the tool axis point locus curve through the correlation function between tool point and tool axis point, and obtain the tool axis point coordinates and tool axis vector information corresponding to the interpolated tool points. For the case of interpolation inside CAM, the correlation function can be obtained from the Entity class. For the case of interpolation outside CAM, the correlation function can be limited to the equal division case. For a zero-length tool point line segment (joint point), the correlation function is not required, and the tool axis point can be determined through the arc angle interpolation step size, regardless of the tool point. For the case where the tool axis point locus curve degenerates into a point, the tool axis point can also be determined without the correlation function.

[0109] d. Store the interpolation point data into the list list <pathstep>。

[0110] Here, PathStep is a C++ class that aggregates interpolation information for each interpolated point after interpolation. The following is an example of the PathStep class:

[0111]

[0112] In the geometric interpolation step, the interpolation information is mainly the geometric information of the interpolated points

[0113] (m_StepPtS, m_StepPtE, m_nEntityNo, m_dOrientAngle, m_dLength, m_bDrive, m_sDrive).

[0114] For a specific machining process, a step of interpolating process parameters can be added to calculate process-related parameters at the interpolated tool position. When necessary, adjust the tool position and tool axis vector, or adjust the process parameters. For example: for waterjet cutting, according to the kerf taper model, the trailing angle model, and the speed of the current interpolation step, calculate the current jet taper (m_dTE) and the jet trailing angle (m_dJL) at the interpolated tool position. If the tool axis inclination causes a substantial change in the actual cutting thickness, the cutting speed (m_dSpeed) also needs to be adjusted.

[0115] According to the inverse kinematic algorithm of the machine tool, calculate the position information of each physical axis from the tool axis vector of the interpolated tool position. The position information can be incremental or absolute, and the interpolation information is saved in (m_StepPtS, m_StepPtE, m_bDrive, m_sDrive).

[0116] To reduce the data volume, a data compression step can be added here to find adjacent interpolated steps with the same data in the interpolated step data list generated in the above steps and merge these interpolated steps into an interpolated step repeated multiple times. The repetition information is saved in (m_bRepeat, m_sRepeat).

[0117] Arrange the above interpolation information (m_bIO, m_bDrive, m_bDelay, m_bRepeat) into a list of command control words. The command control word consists of 4 WORDS, 64 bits, or 8 bytes in total, and the format is as follows:

[0118] "IO|Drive|Delay|Repeat”

[0119] The "IO" field occupies 16 bits, one WORD

[0120] The "Drive" field occupies 16 bits, one WORD.

[0121] The "Delay" field occupies 16 bits, one WORD.

[0122] The "Repeat" field occupies 16 bits, one WORD.

[0123] In the case of interpolation on the host computer, the above command control word list is sent to the lower computer of the numerical control system. Since the amount of data after interpolation is relatively large, the method of sending data in batches can be adopted to send data to the lower computer. The function of the lower computer is to cache the interpolated data and execute the motion commands and IO commands of each physical axis in the data in sequence. If interpolation is performed on the lower computer, the interpolation information is directly stored in the memory of the lower computer.

[0124] For some motion commands and IO commands that need to be generated in real time, such as the function of the cutting head height following in water jet cutting, the lower computer needs to generate commands for the compensation motion steps of the motion axis according to the height information fed back by the height following sensor, and insert and execute the commands for the compensation motion steps in real time during the execution of the original interpolated data.

[0125] Second Embodiment

[0126] In some solutions of the first embodiment, the specific method of the interpolation strategy on the host computer is specifically disclosed. For the technical solution provided in this embodiment, see Figure 3 , the interpolation strategy for interpolation on the lower computer further includes the following steps executed on the lower computer:

[0127] The machining path segments are stored in the memory of the lower computer in the form of codes. The codes contain the modeling parameter information of the machining path model. Each time, the code parser of the lower computer takes out N lines of codes from the memory and converts them into an array of machining path segments, and inputs the array into the interpolator module. At the same time, the interpolator module obtains the interpolation period and the acceleration / deceleration model;

[0128] Restore the modeling parameter information of each machining path segment code to the tool point locus mathematical model, the tool axis point locus mathematical model, and the correlation function between the tool point and the tool axis point;

[0129] Determine the interpolation step size, and divide the tool point locus model of the machining path segment according to the interpolation step size to obtain the interpolated tool points. For zero-length line segments, the arc angle of the tool axis direction change is divided;

[0130] Determine the corresponding interpolation points on the tool axis point locus model through the correlation function between the tool point and the tool axis point, obtain the interpolated tool axis point coordinates and the tool axis vector information, and store the interpolated tool point coordinates and the tool axis vector data information in an interpolation step list.

[0131] The technical solution of this embodiment is local path interpolation. After interpolation, the amount of data is relatively small (regardless of the total machining path length), and the stability requirements for the data transmission between the upper and lower computers are not high; the data processing after suspension is simple and the response is rapid; for the machining processes that require real-time acquisition of a lot of feedback signals and adjustment of machining data, the real-time performance is good, and it is relatively easy to meet the requirements of high speed and high precision. The strategy framework for interpolation in the lower computer is relatively close to the products on the market, and only the interfaces between the lower computer and the upper computer need to be customized and developed (such as the G-code program format and the program interpreter).

[0132] Preferably, the interpolation strategy for interpolation in the lower computer further includes the following steps executed in the lower computer:

[0133] Based on the acceleration and deceleration mode, the interpolator takes the theoretical machining speed on the tool point path segment as the maximum value, takes the theoretical machining speed at the end point of the path segment as the starting point, and aims to obtain a continuous and smooth machining speed, and gradually adjusts the theoretical machining speed corresponding to each interpolation tool point in both directions towards the midpoint of the path segment.

[0134] The technical solution of this embodiment precisely adjusts the theoretical machining speed through the acceleration and deceleration mode, ensuring the stability of the tool during the machining process. The continuous and smooth machining speed reduces the vibration and impact during the machining process, which helps to improve the quality of the machined surface. By performing interpolation in the lower computer, the computational burden on the upper computer can be reduced, making the machining path more optimized and improving the machining efficiency. The lower computer is usually closer to the control link of the machine tool, which can achieve a faster response speed and reduce the waiting time during machining. The application of the acceleration and deceleration mode ensures the smoothness of the speed change during the machining process, avoiding system instability caused by sudden speed changes. By gradually adjusting the machining speed, the overshoot and oscillation phenomena during the acceleration or deceleration process of the system can be reduced.

[0135] This embodiment also has processes such as expressing the machining path, geometric interpolation, IO interpolation, inverse solution operation, etc. The specific methods / processes are basically the same as those in the first embodiment, except that in this embodiment, interpolation is performed in the lower computer.

[0136] Third Embodiment

[0137] In some solutions of the first embodiment, the specific methods of the interpolation strategy for interpolation in the upper computer are specifically disclosed. In some solutions of the second embodiment, the specific methods of the interpolation strategy for interpolation in the lower computer are specifically disclosed. For the technical solution provided in this embodiment, see Figure 4 , the rough interpolation in the upper computer and the fine interpolation in the lower computer further include the following steps executed in the upper computer:

[0138] The rough interpolation module of the host computer obtains the machining path information by sharing memory with the CAM module, including the tool point locus model, the tool axis point locus model, and the correlation function between the tool point and the tool axis point; or transfers the modeling parameters of the above models from the CAM module to the rough interpolation module by means of data interaction, and then restores the modeling parameters to a mathematical model; the above data interaction method can adopt the text file interaction method;

[0139] Determine the theoretical rough interpolation step size according to the rough interpolation accuracy, divide the arc length of each line segment in the machining path line segment list by the theoretical rough interpolation step size, and round it to N, and divide the arc length of the line segment by N to obtain the actual rough interpolation step size L;

[0140] Use the actual interpolation step size L to divide the line segment. First, equally divide the tool point locus model to obtain the interpolated tool points;

[0141] Find the interpolation points on the tool axis point locus model through the correlation function between the tool point and the tool axis point, and obtain the tool axis vector information corresponding to the interpolated tool points;

[0142] Store the sub-list of N line segments generated after rough interpolation of a single path line segment into the machining path line segment list to replace the line segment before interpolation; the speed of each line segment in the sub-list is the same as the speed of the line segment before interpolation;

[0143] And / or, at the places where the speed of adjacent line segments changes suddenly and the movement direction changes suddenly, adjust the speed of the adjacent line segments with the goal of speed smoothing.

[0144] When adopting the strategy of rough interpolation by the host computer and fine interpolation by the slave computer, the technical solution of this embodiment can reduce the calculation burden of fine interpolation by the slave computer through rough interpolation on the host computer. The rough interpolation algorithm is placed in the software of the host computer, which is easy to debug, update, upgrade and maintain. The amount of data after rough interpolation is much smaller than that of interpolation on the host computer, and the requirement for the stability of data transmission between the host computer and the slave computer is low. For the machining process that needs to collect various feedback signals in real time and adjust the machining data, it has good real-time performance and is relatively easy to meet the requirements of high speed and high precision. The rough interpolation calculation can be implemented in the CAM module. The three-dimensional model of the workpiece can be obtained during interpolation, and non-linear errors will not be caused due to the lack of the three-dimensional model of the workpiece. The fine interpolation calculation cannot be implemented in the CAM module. The three-dimensional model of the workpiece cannot be obtained during interpolation, and non-linear errors will be caused due to the lack of the three-dimensional model of the workpiece during interpolation. However, because of the rough interpolation, this non-linear error is much smaller than the way of directly performing interpolation on the slave computer. And the data processing after suspension is simple and the response is rapid. For the machining process that needs to collect a lot of feedback signals in real time and adjust the machining data, it has good real-time performance and is relatively easy to meet the requirements of high speed and high precision. The rough interpolation shares the complex calculation, and the fine interpolation does not need to perform very complex calculations, and the problem that the calculation amount is limited by the interpolation cycle is alleviated. In addition, this embodiment provides ways such as text file interaction, which increases the compatibility and flexibility of the system with other software (such as CAM system). The interpolation tasks of the host computer and the slave computer are separated, so that it can be adjusted according to different machining requirements and machine tool performance.

[0145] Preferably, the rough interpolation on the host computer and the fine interpolation on the slave computer further include the following steps performed on the slave computer:

[0146] The fine interpolation module of the slave computer obtains the list information of the processed path line segments after rough interpolation by sharing the memory with the rough interpolation module of the host computer, including the tool point trajectory model, the tool axis point trajectory model, and the information of the correlation function between the tool point and the tool axis point; or the modeling parameters of the above models are transferred from the rough interpolation module to the fine interpolation module by means of data interaction, and then the modeling parameters are restored to a mathematical model; the above data interaction method can adopt the text file interaction method;

[0147] Among them, if the modeling parameters of the above models are transferred from the rough interpolation module to the fine interpolation module by means of data interaction, the processed path line segments are stored in the memory of the slave computer in the form of codes, and the codes contain the processed path model modeling parameter information. The code parser of the slave computer takes out N lines of codes from the memory each time and converts them into an array of processed path line segments, and inputs the array into the fine interpolator module. At the same time, the fine interpolator module obtains the interpolation cycle and the acceleration / deceleration model;

[0148] Restore the modeling parameter information of each machining path segment code to the tool point trajectory mathematical model, the tool axis point trajectory mathematical model, and the correlation function between the tool point and the tool axis point;

[0149] Determine the interpolation step size, and divide the tool point trajectory model of the machining path according to the interpolation step size to obtain the interpolated tool points. For line segments with zero length, divide the arc angle of the tool axis direction change;

[0150] Determine the corresponding interpolation points on the tool axis point trajectory model through the correlation function between the tool point and the tool axis point, obtain the interpolated tool axis point coordinates and tool axis vector information, and store the interpolated tool point coordinates and tool axis vector data information in an interpolation step array.

[0151] In this embodiment, the fine interpolation performed by the lower computer is based on the rough interpolation result of the upper computer, further refining the machining path. By restoring the modeling parameter information to a mathematical model and considering the correlation between the tool point and the tool axis point in the fine interpolation, more accurate trajectory planning is achieved. The fine interpolation module of the lower computer can efficiently process the data after rough interpolation, reducing the data processing time and improving the machining efficiency. The code parser is used to quickly convert the machining path segment array, improving the response speed and machining efficiency of the lower computer. This embodiment also ensures the stability of data interaction between the upper and lower computers and reduces data transmission errors through the shared memory or text file interaction method. The smooth correlation between the tool point and the tool axis point in the fine interpolation makes the tool movement smoother and improves the surface finish of the machining. The fine interpolation strategy can be adjusted according to different machining requirements, increasing the flexibility of the system. The fine interpolation module can be optimized according to the computing power of the lower computer and the performance of the machine tool to adapt to different machining environments. The processing of line segments with zero length during the fine interpolation ensures the continuity of the machining path and avoids possible machining interruptions.

[0152] Preferably, the rough interpolation performed by the upper computer and the fine interpolation performed by the lower computer further include:

[0153] The upper computer performs the following steps:

[0154] The upper computer generates and outputs a machining program for the list data obtained after rough interpolation and sends it to the lower computer;

[0155] The lower computer performs the following steps:

[0156] Obtain the machining program and perform the fine interpolation operation. After fine interpolation, perform speed smoothing processing;

[0157] Import an inverse solver, and the inverse solver calculates the position information of each physical axis from the tool point coordinates and tool axis vector information of the interpolated tool points according to the inverse kinematic algorithm of the machine tool.

[0158] In this embodiment, the machining program generated by the host computer is based on the result of rough interpolation, ensuring the accuracy of the tool path. The slave computer performs fine interpolation on this basis, further refining the machining path and improving the machining accuracy. The speed smoothing process after fine interpolation reduces the impact and vibration during machining and improves the quality of the machined surface. The combined action of the rough interpolation of the host computer and the fine interpolation of the slave computer optimizes the machining path, reduces unnecessary movements, and improves the machining efficiency.

[0159] In some embodiments, zero-length line segments are added at the endpoints of the path segments to set the theoretical machining speed and the change information of the tool axis vector at the endpoints of the path segments; the theoretical machining speed of the zero-length line segments is used for the adjustment of the above-mentioned machining speed.

[0160] By adding zero-length line segments at the endpoints of the path segments, the theoretical machining speed can be accurately set and controlled, so that the speed change of the tool during machining is smoother, reducing the machining error caused by sudden speed changes and improving the machining accuracy. The smooth speed change reduces the vibration and impact during machining, thus improving the quality of the machined surface.

[0161] This embodiment also has processes such as expressing the machining path, geometric interpolation, IO interpolation, inverse solution operation, etc. The specific methods / processes are basically the same as those in the first embodiment, except that in this embodiment, rough interpolation is performed on the host computer and further fine interpolation is performed on the slave computer.

[0162] Fourth Embodiment

[0163] This embodiment is applicable to the first to third embodiments. When performing interpolation control for a flexible tool, an offset amount that needs to be compensated backward is calculated based on a prediction mathematical model and preset process parameters, and the initial tool axis vector after offset is optimized according to the offset amount compensated backward to effectively compensate for the errors brought during machining:

[0164] Call the first prediction mathematical model, calculate the trailing amount generated by cutting the workpiece according to the target parameter information of the current position point, and then calculate the first angle that needs to swing along the cutting feed direction for backward compensation;

[0165] Obtain the first component of the initial tool axis vector along the cutting feed direction, and perform the first optimization according to the first angle to obtain the result of the second component of the optimized tool axis vector along the cutting feed direction;

[0166] Call the second prediction mathematical model, calculate the lateral taper generated by cutting the workpiece according to the target parameter information of the current position point, and then calculate the second angle that needs to swing along the vertical direction of the cutting feed direction for backward compensation;

[0167] Obtain the third component of the initial tool axis vector in the direction perpendicular to the cutting feed direction, and perform a second optimization according to the second angle to obtain the result of the fourth component of the optimized tool axis vector perpendicular to the cutting feed direction;

[0168] Synthesize the final optimized tool axis vector according to the values of the second component and the fourth component.

[0169] Before the call to the prediction mathematical model for prediction, it includes:

[0170] Determine the current cutting speed in the water jet cutting scenario;

[0171] Calculate the cutting speed at each point on the cutting path according to the mathematical model corresponding to the ruled surface and the preset machining process parameters

[0172] where, v is the cutting speed, Nm is the material machinability parameter, Pw is the water pressure, is the water flow rate, is the abrasive flow rate, Cs is the scale factor, q is the cutting quality grade, H is the material thickness, and D is the jet beam diameter. In the embodiments of the present application, Pw, the specific values corresponding to the D superscript can be determined in advance according to requirements or tests, etc. The embodiments of the present application do not limit this, and the specific values in the above formula are only examples.

[0173] The call to the first prediction mathematical model to calculate the trailing amount generated by the cutting workpiece according to the target parameter information of the current position point includes:

[0174] Obtain the current cutting speed, and combine the material thickness, material type, and process parameter information of the current position point to calculate the formula for the trailing amount generated by water jet cutting as follows:

[0175]

[0176] where, J(h) is the trailing amount, P is the water pressure, is the abrasive flow rate, h is the cutting depth, and v is the cutting speed. In the embodiments of the present application, the fixed values of each parameter can be determined in advance according to requirements or tests, etc. The embodiments of the present application do not limit this, and the specific values in the above formula are only examples.

[0177] The call to the second prediction mathematical model to calculate the lateral taper generated by the cutting workpiece according to the target parameter information of the current position point includes:

[0178] Obtain the current cutting speed and material thickness, and calculate the current lateral taper angle:

[0179]

[0180] Wherein, TA is the lateral taper generated by cutting, V is the cutting speed, and H is the thickness of the material to be cut at the current cutting point. In the embodiments of the present application, the fixed values of each parameter can be determined in advance according to requirements or tests, etc., and the embodiments of the present application do not limit this. The specific values in the above formula are only examples.

[0181] In one embodiment, the determining the initial tool axis vector according to the generatrix of the to-be-machined ruled surface or the preset cutting direction includes: If the upper edge curve and the lower edge curve of the ruled machining surface are simple geometric curves, offset the upper edge curve and the lower edge curve outward perpendicular to the machining surface by a tool radius; If the upper edge curve and the lower edge curve of the ruled machining surface are non-simple geometric curves, discretize each ruled machining surface into a combination of straight generatrices; Offset the straight generatrix group outward perpendicular to the machining surface by a tool radius, fit the upper points of the offset straight generatrix group into the upper edge curve as the locus curve of the tool point, and fit the lower points of the straight generatrix group into the lower edge curve as the locus curve of the tool axis point. If the upper edge curve or the lower edge curve is a simple geometric curve, the parameter equation thereof may not need to be determined by using the curve fitting method, but the parameters can be directly determined by using the existing function expression as its mathematical model. Among them, a special case of the mathematical model of a simple geometric curve is a circular arc, and the parameter equation of the circular arc is x(u) = cos(u), y(u) = sin(u). If the upper edge curve or the lower edge curve is not a simple geometric curve but a complex curve, curve fitting is required. Specifically, any available method can be used to perform curve fitting on the upper edge curve and the lower edge curve, and then its mathematical model can be obtained. The embodiments of the present application do not limit this. A special case of the mathematical model of a complex curve is the parameter equation of a NonUniform Rational B-Splines (NURBS) curve. From the above analysis, it can be seen that in the embodiments of the present application, the mathematical model of the upper edge curve and the mathematical model of the lower edge curve can both correspond to a straight line, a circular arc, or a spline curve, or can also correspond to other one or a group of complex functions, or correspond to a database, etc. Moreover, in practical applications, the upper edge curve and the lower edge curve corresponding to the same ruled surface can be the same or different, and the embodiments of the present application do not limit this either.

[0182] In one embodiment, determining the initial tool axis vector according to the generatrix of the ruled surface to be machined or a preset cutting direction includes: If the upper edge curve and the lower edge curve of the ruled machining surface are simple geometric curves, offset the upper edge curve and the lower edge curve outward perpendicular to the machining surface by a tool radius; If the upper edge curve and the lower edge curve of the ruled machining surface are non-simple geometric curves, discretize each ruled machining surface into a combination of straight generatrices; Offset the straight generatrix group outward perpendicular to the machining surface by a tool radius, fit the upper points of the offset straight generatrix group into the upper edge curve as the locus curve of the tool point, and fit the lower points of the straight generatrix group into the lower edge curve as the locus curve of the tool axis point. If the upper edge curve or the lower edge curve is a simple geometric curve, it is not necessary to use the curve fitting method to determine its parametric equation, and the existing function expression can be directly used to determine its parameters as its mathematical model. Among them, a special case of the mathematical model of a simple geometric curve is a circular arc, and the parametric equation of the circular arc is x(u)=cos(u), y(u)=sin(u). If the upper edge curve or the lower edge curve is not a simple geometric curve but a complex curve, curve fitting is required. Specifically, any available method can be used to perform curve fitting on the upper edge curve and the lower edge curve to obtain its mathematical model, which is not limited in the embodiments of the present application. A special case of the mathematical model of a complex curve is the parametric equation of a Non-Uniform Rational B-Splines (NURBS) curve. From the above analysis, it can be seen that in the embodiments of the present application, the mathematical models of the upper edge curve and the lower edge curve can both correspond to a straight line, a circular arc or a spline curve, or can also correspond to other one or a group of complex functions, or correspond to a database, etc. Moreover, in practical applications, the upper edge curve and the lower edge curve corresponding to the same ruled surface can be the same or different, which is not limited in the embodiments of the present application.

[0183] Preferably, when performing interpolation control for a rigid tool, it is judged whether the initial tool axis vector is deformed by force during the process of generating a machining path and performing machining according to the initial tool axis vector and the workpiece model. When the initial tool axis vector is deformed by force during the machining path, calculate the tool force deformation amount that needs to be compensated in reverse according to the machining feature data collected in real time, obtain the tool diameter, the force applied to the tool, and the tool protrusion length, and calculate the tool force deformation amount δ according to the tool force deformation amount formula:

[0184]

[0185] where D is the tool diameter, P is the force applied to the tool, L is the tool protrusion length, and E is the natural constant with a value of 2.718;

[0186] Optimize the deformed initial tool axis vector according to the tool force deformation amount of the reverse compensation to effectively compensate for the errors brought during the machining process, and obtain the optimal tool axis vector;

[0187] Among them, the machining feature data includes three cutting elements, the morphological features of the machined surface, machine tool errors, and data related to the machining process.

[0188] Calculate the tool withdrawal amount according to the three cutting elements, and the reverse compensation can also be carried out by the same method to reduce errors. Overcome the defects of common tool axis vector determination methods such as normal machining method, preset tool axis method, and interpolation method.

[0189] The core idea of the present invention is to interpolate and optimize the machining path of the machining surface based on multiple interpolation strategies considering multiple models. Based on three interpolation strategies, and on the basis of the tool point trajectory curve model, the tool axis point trajectory curve model, and the correlation function between the tool point and the tool axis point, it also comprehensively considers the iterative interpolation of the geometric model and the speed model, the optimization and adjustment of the tool axis amount by the process model, etc. Optimize through the above multiple models to improve the control accuracy of interpolation and reduce machining errors.

[0190] Based on the same concept, the present invention also provides a machine tool, including the multi-model-based machining path interpolation numerical control system described in any one of the above.

[0191] If it is implemented in the form of program instructions and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on such an understanding, the technical solution of this embodiment, in essence, or the part that contributes to the prior art, or all or part of this technical solution, can be embodied in the form of software. This computer software is stored in a storage medium, including several instructions to enable a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in various embodiments of the present disclosure. And the aforementioned storage medium includes: USB flash drive, mobile hard disk, read-only memory (ROM), random access memory (RAM), magnetic disk, or optical disc and other various media that can store program codes.

[0192] Those skilled in the art can clearly understand that for the sake of convenient and concise description, the specific identification content executed by the above-described system and device can refer to the corresponding process in the foregoing method embodiments.

[0193] The embodiments of the present invention have been described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above embodiments. Even if various changes are made to the present invention, provided that these changes fall within the scope of the claims of the present invention and their equivalent technologies, they still fall within the protection scope of the present invention.< / pathstep> < / entity> < / entity>

Claims

1. A multi-model-based machining path interpolation numerical control system, characterized in that, Comprising: A memory that acquires and stores machining path information and interpolated stepping information, where the machining path information includes a cutter location point trajectory model, a cutter axis point trajectory model, and a correlation function between the cutter location point and the cutter axis point; An interpolator that performs iterative interpolation of geometry and machining speed by reading the machining path information from the memory based on a selected interpolation strategy. The geometry interpolation densifies and decomposes each segment of the machining path into interpolation steps according to the cutter location point trajectory model, the cutter axis point trajectory model, and the correlation function, arranges the data of all interpolation steps in a cutter location point list according to the machining order, and then sets the machining speed, setting the machining speed based on the interpolated cutter location points after geometry interpolation; Where the interpolation strategies include: performing interpolation on the host computer, performing interpolation on the slave computer, and performing rough interpolation on the host computer and fine interpolation on the slave computer; An inverse solver that inversely calculates and stores the position information of each physical axis from the cutter location point and the cutter axis vector direction of the interpolated cutter location point; A driver that generates and outputs motion control and / or IO control commands to drive the various axes of the machine tool and supporting equipment to work.

2. The multi-model based machining path interpolation numerical control system according to claim 1, characterized in that, The interpolation strategy of performing interpolation on the host computer further includes the following steps performed on the host computer: The interpolation module of the host computer obtains the machining path information, including the cutter location point trajectory model, the cutter axis point trajectory model, and the correlation function between the cutter location point and the cutter axis point, by sharing memory with the CAM module; or transfers the modeling parameters of the above cutter location point trajectory model, cutter axis point trajectory model, and the correlation function between the cutter location point and the cutter axis point from the CAM module to the interpolation module through data interaction, and then restores the modeling parameters to a mathematical model; the above data interaction method can adopt a text file interaction method; Determine the interpolation step size according to the interpolation period and / or control accuracy and / or theoretical machining speed; Divide the cutter location point trajectory curve of the machining path segment by the interpolation step size to obtain interpolated cutter location points; Determine the corresponding interpolation points on the cutter axis point trajectory model based on the correlation function between the cutter location point and the cutter axis point, and obtain the coordinate and cutter axis vector information of the interpolated cutter axis point corresponding to the interpolated cutter location point; Store the coordinate and cutter axis vector data information of the interpolated cutter location points into an interpolation step list.

3. The multi-model-based machining path interpolation numerical control system according to claim 2, characterized in that The interpolation strategy of performing interpolation on the host computer further further includes the following steps performed on the host computer: Based on the acceleration limit and / or acceleration / deceleration model, with the theoretical machining speed on the cutter location point path segment as the maximum value, the theoretical machining speed at the end point of the path segment as the starting point, and with the goal of obtaining continuous and smooth machining speed, gradually adjust the theoretical machining speed corresponding to each interpolated cutter location point in both directions towards the midpoint of the path segment; And / or, add a zero-length segment at the end point of the path segment to set the change of the theoretical machining speed and the cutter axis vector at the end point of the path segment; where the theoretical machining speed of this zero-length segment is used for the above adjustment of the machining speed.

4. The multi-model-based machining path interpolation numerical control system according to claim 1, characterized in that, The interpolation strategy of performing interpolation on the slave computer further includes the following steps performed on the slave computer: The machining path segments are stored in the memory of the lower computer in the form of codes. The codes contain the modeling parameter information of the machining path model. Each time, the code parser of the lower computer fetches N lines of codes from the memory, converts them into an array of machining path segments, and inputs the array into the interpolation module. At the same time, the interpolation module obtains the interpolation cycle and the acceleration / deceleration model; Restore the modeling parameter information of each machining path segment code to the mathematical model of the tool point trajectory, the mathematical model of the tool axis point trajectory, and the correlation function between the tool point and the tool axis point; Determine the interpolation step size, and divide the tool point trajectory model of the machining path segment according to the interpolation step size to obtain the interpolated tool points. For a segment with zero length, divide the arc angle of the tool axis direction change; Determine the corresponding interpolation points on the tool axis point trajectory model through the correlation function between the tool point and the tool axis point, obtain the interpolated tool axis point coordinates and the tool axis vector information, and store the interpolated tool point coordinates and the tool axis vector data information in an interpolation step list.

5. The multi-model based machining path interpolation numerical control system according to claim 4, characterized in that The interpolation strategy for interpolation on the lower computer further includes the following steps executed on the lower computer: Based on the acceleration / deceleration mode, the interpolation module takes the theoretical machining speed on the tool point path segment as the maximum value, takes the theoretical machining speed at the end point of the path segment as the starting point, and aims to obtain a continuous and smooth machining speed, and gradually adjusts the theoretical machining speed corresponding to each interpolated tool point in both directions towards the midpoint of the path segment.

6. The multi-model-based machining path interpolation numerical control system according to claim 1, wherein The rough interpolation on the upper computer and the fine interpolation on the lower computer further includes the following steps executed on the upper computer: The rough interpolation module of the upper computer obtains the machining path information, including the tool point trajectory model, the tool axis point trajectory model, and the correlation function between the tool point and the tool axis point, by sharing the memory with the CAM module; or transfers the modeling parameters of the above tool point trajectory model, tool axis point trajectory model, and the correlation function between the tool point and the tool axis point from the CAM module to the rough interpolation module through data interaction, and then restores the modeling parameters to the mathematical model; the above data interaction method can adopt the text file interaction method; Determine the theoretical rough interpolation step size according to the rough interpolation accuracy, divide the arc length of each segment in the machining path segment list by the theoretical rough interpolation step size, and round it to N, and divide the arc length of the segment by N to obtain the actual rough interpolation step size L; Use the actual interpolation step size L to divide the segment. First, equally divide the tool point trajectory model to obtain the interpolated tool points; Find the interpolation points on the tool axis point trajectory model through the correlation function between the tool point and the tool axis point, and obtain the tool axis vector information corresponding to the interpolated tool points; Store the sub-list of N segments generated after rough interpolation of a single path segment in the machining path segment list to replace the segment before interpolation; The speed of each segment in the sub-list is the same as the speed of the segment before interpolation; And / or, at the places where the speed of adjacent segments changes suddenly and the movement direction changes suddenly, adjust the speed of the adjacent segments with the goal of speed smoothing.

7. The multi-model-based machining path interpolation numerical control system according to claim 6, wherein The rough interpolation on the upper computer and the fine interpolation on the lower computer further includes the following steps executed on the lower computer: The fine interpolation module of the lower computer obtains the processed path segment list information after rough interpolation by sharing memory with the rough interpolation module of the upper computer, including the tool point trajectory model, the tool axis point trajectory model, and the correlation function information between the tool point and the tool axis point; or transfers the above modeling parameters of the tool point trajectory model, the tool axis point trajectory model, and the correlation function between the tool point and the tool axis point from the rough interpolation module to the fine interpolation module through data interaction, and then restores the modeling parameters to a mathematical model; the above data interaction method can adopt the text file interaction method; Among them, if the modeling parameters of the above tool point trajectory model, tool axis point trajectory model, and the correlation function between the tool point and the tool axis point are transferred from the rough interpolation module to the fine interpolation module through data interaction, the processed path segments are stored in the memory of the lower computer in the form of codes, and the codes contain the processed path model modeling parameter information. The code parser of the lower computer takes out N lines of codes from the memory each time and converts them into a processed path segment array, and inputs the array into the fine interpolation module. At the same time, the fine interpolation module obtains the interpolation cycle and the acceleration and deceleration model; Restore the modeling parameter information of each processed path segment code to the tool point trajectory mathematical model, the tool axis point trajectory mathematical model, and the correlation function between the tool point and the tool axis point; Determine the fine interpolation step length, and divide the tool point trajectory model of the processed path according to the fine interpolation step length to obtain the fine interpolation tool points. Among them, for the zero-length line segment, the arc angle of the tool axis direction change is divided; Determine the corresponding interpolation points on the tool axis point trajectory model through the correlation function between the tool point and the tool axis point, obtain the interpolation tool axis point coordinates and the tool axis vector information, and store the interpolation tool point coordinates and the tool axis vector data information in an interpolation step array.

8. The multi-model-based machining path interpolation numerical control system according to claim 6, wherein, The rough interpolation on the upper computer and the fine interpolation on the lower computer further include: The upper computer executes the following steps: The upper computer generates and outputs a processing program for the list data obtained after rough interpolation, and sends it to the lower computer; The lower computer executes the following steps: Obtain the processing program and execute the fine interpolation operation, and perform speed smoothing processing after fine interpolation; Import the inverse solver, and the inverse solver calculates the position information of each physical axis from the tool point coordinates and the tool axis vector information of the interpolation tool points according to the machine tool inverse kinematics algorithm.

9. The multi-model-based machining path interpolation numerical control system according to claim 1, wherein Add zero-length line segments at the endpoints of the path segments to set the theoretical processing speed and the change information of the tool axis vector at the endpoints of the path segments; among them, the theoretical processing speed of the zero-length line segment is used for the adjustment of the above processing speed.

10. The multi-model-based machining path interpolation numerical control system according to claim 1, characterized in that When performing interpolation control for a flexible tool, calculate the offset amount that needs to be compensated backward based on the prediction mathematical model and the preset process parameters, and optimize the offset initial tool axis vector according to the offset amount that needs to be compensated backward to effectively compensate the errors brought during the processing: Call the first prediction mathematical model, calculate the trailing amount generated by cutting the workpiece according to the target parameter information of the current position point, and then calculate the first angle that needs to swing along the cutting feed direction for backward compensation; Obtain the first component of the initial tool axis vector along the cutting feed direction, and perform the first optimization according to the first angle to obtain the result of the second component of the optimized tool axis vector along the cutting feed direction; Call the second prediction mathematical model, calculate the lateral taper generated by the cutting workpiece according to the target parameter information of the current position point, and then calculate the second angle that needs to swing in the vertical direction along the cutting feed direction for reverse compensation; Obtain the third component of the initial tool axis vector in the vertical direction along the cutting feed direction, and perform the second optimization according to the second angle to obtain the result of the fourth component of the optimized tool axis vector perpendicular to the cutting feed direction; According to the values of the second component and the fourth component, synthesize the finally optimized tool axis vector.

11. The multi-model-based machining path interpolation numerical control system according to claim 1, wherein When performing interpolation control for a rigid tool, judge whether the initial tool axis vector is deformed by force during the machining process when generating a machining path according to the initial tool axis vector and the workpiece model and executing the machining process. When the initial tool axis vector is deformed by force during the machining path, calculate the tool force deformation amount that needs to be reverse-compensated according to the machining feature data of the machined surface collected in real time, obtain the tool diameter, the force applied to the tool, and the tool protrusion length, and calculate the tool force deformation amount δ according to the tool force deformation amount formula; Optimize the deformed initial tool axis vector according to the reverse-compensated tool force deformation amount to effectively compensate for the errors brought during the machining process, and obtain the optimal tool axis vector; Wherein, the machining feature data of the rigid tool includes the three cutting elements, the surface morphology features of the machined surface, the machine tool error, and the data related to the machining process.

12. A machine tool, characterized in that, Including the multi-model-based machining path interpolation numerical control system according to any one of claims 1 to 11.

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