Dynamic adjustable seven-axis table and method for eliminating nonlinear errors in cambering

Abstract

The application discloses a dynamic adjustable seven-axis worktable and method capable of eliminating nonlinear errors in curved surface machining. The application comprises a two-degree-of-freedom center positioning worktable, a three-degree-of-freedom reverse adjustment worktable and a two-degree-of-freedom workpiece posture adjustment worktable. The application is suitable for machining complex curved surface parts. Firstly, a tool position file of a curved surface workpiece, i.e. a space curve, is discretized into a tiny plane curve, and then the plane curve is discretized into a plurality of plane circular arcs. The workpiece posture adjustment worktable is adjusted to rotate the plane curve to a horizontal plane, the center positioning worktable is adjusted according to the center position of a to-be-machined plane circular arc to realize center positioning of the plane circular arc, and the tool position point position of a gantry five-axis linkage machine tool is adjusted according to the radius of the to-be-machined plane circular arc. The application uses circular arcs to fit curves, improves machining precision, and the tool position point of a tool is unchanged in the machining process, so that nonlinear errors generated by double-rotation shaft movement are eliminated in principle.

Description

TECHNICAL FIELD

[0001] The present application relates to a machine tool worktable, in particular to a dynamic adjustable seven-axis worktable capable of eliminating nonlinear errors in curved surface machining and a method thereof. BACKGROUND

[0002] The existing machine tool adopts an interpolation method for curved surface and curve machining. The interpolation method is a process of determining the trajectory of the tool contact point on the numerical control machine tool according to a certain method. According to the given speed and trajectory, some new intermediate points are added between the known points of the trajectory, and the workpiece table and the tool pass through these intermediate points, thereby completing the entire movement. In a more popular way, the tool uses a polyline method to process the desired curve in small segments, which is equivalent to using a large number of small line segments and circular arcs to approximate the curve to be machined.

[0003] The interpolation method includes linear interpolation, circular interpolation, and spline interpolation. Linear interpolation is a straight line between two points. Circular interpolation is to calculate a point group approximating the actual circular arc according to the interpolation digital information between the end points, control the tool to move along these points, and process the circular curve. However, the essence is still to use a large number of small straight lines to process the circular curve.

[0004] Because of the approximation fitting, there is a machining error in theory, and the linear interpolation will produce nonlinear system errors. A three-axis machine tool does not have a rotating shaft and cannot perform rotation machining. A four-axis machine tool has a rotating shaft and can perform rotation machining. However, since the rotating shaft and the workpiece are fixedly connected, the workpiece can only rotate around a fixed rotating shaft and can only process a circular arc with a fixed center. A five-axis machine tool has two rotating shafts and can process a circular arc with a certain shape. However, due to the structural limitations of the five-axis machine tool, it cannot process a circular arc with an arbitrary center and an arbitrary radius on a plane. SUMMARY

[0005] The present application aims to overcome the shortcomings of the prior art and provide a dynamic adjustable seven-axis worktable capable of eliminating nonlinear errors in curved surface machining. The worktable of the present application comprises a center positioning worktable with two degrees of freedom (translational axes X1 and Y1), a reverse adjustment worktable with three degrees of freedom (translational axes X2 and Y2 and a rotating shaft C1), and a workpiece posture adjustment worktable with two degrees of freedom (rotating shafts C2 and A2). The present application is particularly suitable for machining complex curved surface parts with complex shapes and high surface quality requirements. First, the tool position file of the curved surface workpiece, i.e., the spatial curve, is discretized into small plane curves, and then the plane curves are discretized into multiple plane circular arcs. The workpiece posture adjustment worktable is adjusted to rotate the plane curve to the horizontal plane, the center positioning worktable is adjusted to realize the center positioning of the plane circular arc, and the tool of the gantry five-axis machine tool is adjusted to determine the machining radius.

[0006] The technical scheme of the present application is as follows:

[0007] One kind is dynamically adjustable seven-axis worktable for eliminating nonlinear error of curved surface processing

[0008] The dynamically adjustable seven-axis worktable comprises a center positioning worktable, a reverse adjustment worktable and a workpiece posture adjustment worktable, the center positioning worktable is fixedly installed on a machine tool frame, the reverse adjustment worktable is rotatably installed on the center positioning worktable, the workpiece posture adjustment worktable is rotatably installed on the reverse adjustment worktable, and a workpiece to be processed is fixedly installed on the workpiece posture adjustment worktable.

[0009] The center positioning worktable comprises a center positioning worktable lower table, a center positioning worktable middle table and a center positioning worktable upper table; the center positioning worktable lower table is fixedly installed on the machine tool frame, the center positioning worktable middle table is slidably installed on the center positioning worktable lower table, the center positioning worktable upper table is slidably installed on the center positioning worktable middle table, the sliding direction of the center positioning worktable middle table on the center positioning worktable lower table is perpendicular to the sliding direction of the center positioning worktable upper table on the center positioning worktable middle table, and the reverse adjustment worktable is rotatably installed on the center positioning worktable upper table.

[0010] The reverse adjustment worktable comprises a reverse adjustment worktable lower table, a reverse adjustment worktable middle table and a reverse adjustment worktable upper table; the reverse adjustment worktable lower table is rotatably installed on the center positioning worktable, the reverse adjustment worktable middle table is slidably installed on the reverse adjustment worktable lower table, the reverse adjustment worktable upper table is slidably installed on the reverse adjustment worktable middle table, the sliding direction of the reverse adjustment worktable middle table on the reverse adjustment worktable lower table is perpendicular to the sliding direction of the reverse adjustment worktable upper table on the reverse adjustment worktable middle table, and the workpiece posture adjustment worktable is rotatably installed on the reverse adjustment worktable upper table.

[0011] The workpiece posture adjustment worktable comprises a workpiece posture adjustment worktable lower table and a workpiece posture adjustment worktable upper table.

[0012] The reverse adjustment worktable is provided with an upwardly extending mounting bracket, the workpiece posture adjustment worktable lower table is rotatably installed in the mounting bracket of the reverse adjustment worktable upper table, the workpiece posture adjustment worktable upper table is rotatably installed on the workpiece posture adjustment worktable lower table, the rotation axis of the reverse adjustment worktable lower table is perpendicular to the rotation axis of the workpiece posture adjustment worktable lower table, and the rotation axis of the workpiece posture adjustment worktable lower table is perpendicular to and intersects with the rotation axis of the workpiece posture adjustment worktable upper table.

[0013] In the initial position, the rotation axis of the reverse adjustment worktable is coaxial with the rotation axis of the workpiece posture adjustment worktable upper table.

[0014] Two, a method for using a dynamic adjustable seven-axis worktable capable of eliminating nonlinear errors of curved surface machining,

[0015] 1) Discretize all tool path space curves in a workpiece space curved surface into corresponding multiple tool path plane curves respectively; determine multiple approximate circular arcs corresponding to each tool path plane curve, and then calculate the center and radius of the multiple approximate circular arcs; determine an initial tool path space curve and a corresponding initial tool path plane curve;

[0016] 2) Fix and install the workpiece to be machined on a workpiece posture adjustment worktable, fix and install the dynamic adjustable seven-axis worktable on a gantry five-axis linkage machine tool and restore it to the initial position, and adjust the workpiece posture adjustment worktable so that the plane in which the current tool path plane curve is located coincides with the machining plane of the dynamic adjustable seven-axis worktable;

[0017] 3) According to the center position and radius of each approximate circular arc, adjust the center positioning worktable and the tool of the gantry five-axis linkage machine tool, and through reverse adjustment of the rotational motion between the worktable and the center positioning worktable, relative motion is generated between the tool and the workpiece to be machined, and the current approximate circular arc is machined on the workpiece to be machined. During the current machining process, the tool position remains unchanged, and the tool axis vector also remains unchanged, and the machining of the current approximate circular arc is completed;

[0018] 4) Reverse adjust the reverse adjustment worktable according to the translational motion of the center positioning worktable, so that the position of the workpiece to be machined and the position of the tool do not change, and then drive the reverse adjustment worktable to rotate on the center positioning worktable, independently change the tool position and the tool axis vector, and make the tool work to the next tool position;

[0019] 5) According to the center and radius of the next approximate circular arc in the current tool path plane curve, repeat steps 3) to 4), machine the corresponding approximate circular arc and drive the tool to work to the next tool position, until all approximate circular arcs in the current tool path plane curve are machined;

[0020] 6) Adjust the posture of the workpiece to be machined by adjusting the workpiece posture adjustment worktable, so that the machining surface of the dynamic adjustable seven-axis worktable coincides with the plane in which the next tool path plane curve is located, and then move the tool position to the position of the first tool position of the current tool path plane curve;

[0021] 7) Repeat steps 3) to 6), machine the corresponding tool path plane curve according to the center and radius of all approximate circular arcs of the remaining tool path plane curves in the current tool path space curve, until the current tool path space curve is machined;

[0022] 8) repeating 7), traversing the remaining tool path space curve, until the actual space surface is machined, thereby obtaining the target workpiece.

[0023] In the workpiece space surface, each tool path space curve is discretized into a plurality of tool path plane curves by the following method:

[0024] Each tool path space curve is composed of a plurality of discrete tool position points, and whether adjacent tool position points are located on the same plane and the turning point between the adjacent two planes are sequentially judged, so as to determine each plane, and the tool position points in each plane form each tool path plane curve.

[0025] In the 4), the reverse adjustment workbench is driven to rotate on the center positioning workbench to independently change the tool position point and the tool axis vector of the tool, so that the tool works to the next tool position point, and specifically:

[0026] The tool axis vector of the tool at the last tool position point position is unchanged, the reverse adjustment workbench is driven to rotate on the center positioning workbench, so that the tool moves to the next tool position point position, and then the tool axis vector of the tool at the next tool position point position is changed; or, the tool axis vector of the tool at the last tool position point position is changed, and then the reverse adjustment workbench is driven to rotate on the center positioning workbench under the premise of keeping the tool axis vector unchanged, so that the tool moves to the next tool position point position.

[0027] In the 2), the workpiece to be machined is a workpiece machined by a gantry five-axis linkage machine tool.

[0028] In the 3), the position of the center positioning workbench axis is adjusted according to the center position of each approximate circular arc, so that the axis of the center positioning workbench coincides with the center of the approximate circular arc, the position of the tool position point of the gantry five-axis linkage machine tool is adjusted according to the radius corresponding to each approximate circular arc, so that the position of the tool contact point is on the arc line of the approximate circular arc, and the relative movement between the tool and the workpiece to be machined is generated through the rotation movement between the reverse adjustment workbench and the center positioning workbench, and the current approximate circular arc is machined on the workpiece to be machined.

[0029] The beneficial effects of the present application are:

[0030] Using the present application, circular arcs with any center position and any radius on a plane within a certain range (the center position and the radius depend on the actual size of the workbench) can be machined, and space curves and space surfaces can be machined, overcoming the limitation of five-axis linkage machine tools that can only machine straight lines and circular arcs with certain center positions.

[0031] The workbench eliminates the nonlinear error caused by the interpolation algorithm of the five-axis linkage machine tool in theory, reduces the machining error, improves the machining precision, meets the demand of modern production, and is especially suitable for machining complex curved surface with large curvature and small curvature radius. BRIEF DESCRIPTION OF DRAWINGS

[0032] The application will be further described below in combination with the drawings and embodiments.

[0033] Figure 1 It is a whole schematic diagram of the dynamic adjustable seven-axis workbench for eliminating nonlinear error in curved surface machining.

[0034] Figure 2 It is a schematic diagram of the workpiece posture adjustment workbench.

[0035] Figure 3 It is a schematic diagram of the reverse adjustment workbench.

[0036] Figure 4 It is a schematic diagram of the center positioning workbench.

[0037] Figure 5 It is a schematic diagram of the principle of generating nonlinear error.

[0038] Figure 6 It is a schematic diagram of eliminating nonlinear error.

[0039] Figure 7 It is a method flow chart of the dynamic adjustable seven-axis workbench for eliminating nonlinear error in curved surface machining.

[0040] Figure 8 It is a use method flow chart of the dynamic adjustable seven-axis workbench for eliminating nonlinear error in curved surface machining.

[0041] In the drawings: the upper table 1 of the workpiece posture adjustment workbench, the lower table 2 of the workpiece posture adjustment workbench, the upper table 3 of the reverse adjustment workbench, the middle table 4 of the reverse adjustment workbench, the lower table 5 of the reverse adjustment workbench, the upper table 6 of the center positioning workbench, the middle table 7 of the center positioning workbench, and the lower table 8 of the center positioning workbench. DETAILED DESCRIPTION

[0042] The application will be further described below in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to illustrate and explain the application, and are not used to limit the application.

[0043] As Figure 1As shown, the dynamic adjustable seven-axis workbench includes a center positioning workbench, a reverse adjustment workbench, and a workpiece posture adjustment workbench. The center positioning workbench, the reverse adjustment workbench, and the workpiece posture adjustment workbench are coaxially arranged and sequentially stacked from bottom to top. The center positioning workbench is fixedly installed on the machine tool frame. The reverse adjustment workbench and the components above it are rotatably installed on the center positioning workbench. The workpiece posture adjustment workbench and the components above it are rotatably installed on the reverse adjustment workbench. The workpiece to be machined is fixedly installed on the workpiece posture adjustment workbench.

[0044] As shown in Figure 4 The center positioning workbench includes a center positioning workbench lower table 8, a center positioning workbench middle table 7, and a center positioning workbench upper table 6. The center positioning workbench lower table 8 is fixedly installed on the machine tool frame. The center positioning workbench middle table 7 is slidably installed on the center positioning workbench lower table 8. The center positioning workbench upper table 6 is slidably installed on the center positioning workbench middle table 7. The sliding direction of the center positioning workbench middle table 7 on the center positioning workbench lower table 8 (denoted as Y1 direction) is perpendicular to the sliding direction of the center positioning workbench upper table 6 on the center positioning workbench middle table 7 (denoted as X1 direction). The reverse adjustment workbench lower table 5 of the reverse adjustment workbench is rotatably installed on the center positioning workbench upper table 6.

[0045] As shown in Figure 3 The reverse adjustment workbench includes a reverse adjustment workbench lower table 5, a reverse adjustment workbench middle table 4, and a reverse adjustment workbench upper table 3. The reverse adjustment workbench lower table 5 is rotatably installed on the center positioning workbench upper table 6 of the center positioning workbench. The reverse adjustment workbench middle table 4 is slidably installed on the reverse adjustment workbench lower table 5. The reverse adjustment workbench upper table 3 is slidably installed on the reverse adjustment workbench middle table 4. The sliding direction of the reverse adjustment workbench middle table 4 on the reverse adjustment workbench lower table 5 (denoted as Y2 direction) is perpendicular to the sliding direction of the reverse adjustment workbench upper table 3 on the reverse adjustment workbench middle table 4 (denoted as X2 direction). The workpiece posture adjustment workbench lower table 2 of the workpiece posture adjustment workbench is rotatably installed on the reverse adjustment workbench upper table 3. In the initial position, the Y1 direction and the Y2 direction are in the same direction, and the X1 direction and the X2 direction are in the same direction.

[0046] As shown in Figure 2As shown, the workpiece posture adjustment workbench comprises a workpiece posture adjustment workbench lower table 2 and a workpiece posture adjustment workbench upper table 1; the reverse adjustment workbench upper table 3 of the reverse adjustment workbench is provided with an upwardly extending mounting rack, the workpiece posture adjustment workbench lower table 2 is rotatably mounted in the mounting rack on the reverse adjustment workbench upper table 3 of the reverse adjustment workbench, the workpiece posture adjustment workbench upper table 1 is rotatably mounted on the workpiece posture adjustment workbench lower table 2, the rotation axis C1 of the reverse adjustment workbench lower table 5 of the reverse adjustment workbench is perpendicular to the rotation axis A2 of the workpiece posture adjustment workbench lower table 2, the rotation axis A2 of the workpiece posture adjustment workbench lower table 2 is perpendicular to and intersects with the rotation axis C2 of the workpiece posture adjustment workbench upper table 1. In the initial position, the rotation axis C1 of the reverse adjustment workbench lower table 5 of the reverse adjustment workbench is coaxial with the rotation axis C2 of the workpiece posture adjustment workbench upper table 1.

[0047] In the embodiment, the linear motion between the two workbenches adopts screw transmission, and the rotary motion between the two workbenches adopts worm and gear transmission, but is not limited to the two transmission modes given.

[0048] As shown in Figure 7 and Figure 8 The method comprises the following steps:

[0049] 1) Discretize all tool path space curves in the workpiece space surface generated by the UG software into corresponding multiple tool path plane curves respectively; determine multiple approximate circular arcs corresponding to each tool path plane curve (composed of multiple discrete curves), and then calculate the center and radius of the multiple approximate circular arcs; determine the initial tool path space curve and the corresponding initial tool path plane curve;

[0050] In the workpiece space surface, each tool path space curve is discretized into multiple tool path plane curves by the following method:

[0051] Each tool path spatial curve is composed of a plurality of discrete tool position points, whether the adjacent tool position points are located on the same plane is judged in sequence and the turning point between the adjacent two planes is determined, so as to determine each plane, and each tool path plane curve is composed of the tool position points in each plane. For example, three points not on the same straight line can uniquely determine a plane, the adjacent two planes share a middle point, if the adjacent two planes are parallel, the two planes determined by the adjacent five tool position points are the same plane, and the five points are on the same plane, if the adjacent two planes are not parallel, the adjacent five points are not on the same plane, and the third tool position point (the middle point) is the turning point of the two planes. Specifically, a tool position point vector is composed of two adjacent tool position points, a normal vector of the plane composed of three points is obtained from the two adjacent tool position point vectors, and then whether the five tool position points are on the same plane is determined by the normal vectors of the two planes composed of the five tool position points.

[0052] 2) The dynamic adjustable seven-axis worktable is fixedly installed on the gantry five-axis linkage machine tool, the workpiece to be machined is clamped on the workpiece posture adjustment worktable by a clamp, that is, the workpiece to be machined is fixedly installed on the workpiece posture adjustment worktable on the upper table 1 of the workpiece posture adjustment worktable, the dynamic adjustable seven-axis worktable is adjusted to return to the initial position, that is, the axis of the lower table 8 of the center positioning worktable is concentric with the axes of the upper table 6 of the center positioning worktable, the upper table 3 of the reverse adjustment worktable and the upper table 1 of the workpiece posture adjustment worktable, and the workpiece is vertically placed upward, at this time, the position of the workpiece is the initial position (as shown in Figure 1 The plane where the current tool path plane curve is located is adjusted to coincide with the machining surface (horizontal plane) of the dynamic adjustable seven-axis worktable.

[0053] In this embodiment, the workpiece to be machined is a workpiece machined by the gantry five-axis linkage machine tool.

[0054] 3) The position of the axis of the center positioning worktable is adjusted according to the center position corresponding to each approximate circular arc, so that the axis of the center positioning worktable coincides with the center of the approximate circular arc, and the specific method is that the axis of the center positioning worktable moves relative to the workpiece while the workpiece remains stationary by adjusting the center positioning worktable and the reverse adjustment worktable, the position of the tool position point of the gantry five-axis linkage machine tool is adjusted according to the radius corresponding to each approximate circular arc, so that the position of the tool contact point is on the arc of the approximate circular arc, and the relative movement between the tool and the workpiece to be machined is generated by the rotational movement between the reverse adjustment worktable and the center positioning worktable (because the center positioning worktable can only machine a circular arc with a certain range of center positions and radii in the horizontal plane), and the current approximate circular arc is machined on the workpiece to be machined. The tool position point of the tool remains unchanged during the current machining process, and the tool shaft vector also remains unchanged, and the machining of the current approximate circular arc is completed.

[0055] 4) According to the translation movement of the center positioning workbench middle table 7 and the center positioning workbench upper table 6, the corresponding reverse adjustment workbench middle table 4 and the reverse adjustment workbench upper table 3 are adjusted reversely, so that the position of the workpiece to be machined and the position of the tool do not change, avoiding the error caused by repeated positioning. Then, the reverse adjustment workbench is driven to rotate on the center positioning workbench, independently changing the tool position and tool axis vector of the tool, so that the tool works to the next tool position;

[0056] 4) In the fourth aspect, the reverse adjustment workbench is driven to rotate on the center positioning workbench, independently changing the tool position and tool axis vector of the tool, so that the tool works to the next tool position, specifically:

[0057] The tool axis vector of the tool at the last tool position i is unchanged, the reverse adjustment workbench is driven to rotate on the center positioning workbench, so that the tool moves to the next tool position i+1, then the tool position is unchanged at the next tool position i+1, and the tool axis vector of the tool is changed; or, the tool position is unchanged at the last tool position i, and the tool axis vector of the tool is changed, then the reverse adjustment workbench is driven to rotate on the center positioning workbench under the premise of keeping the tool axis vector unchanged, so that the tool moves to the next tool position i+1.

[0058] In a linear interpolation system, the theoretical interpolation trajectory is a straight line motion. When a rotary motion is added, such as:

[0059] In a five-axis linkage numerical control system, the tool swings or the workbench rotates, then in the actual machining process, due to the inconsistency between the nonlinear motion of the five-axis linkage and the linear interpolation of the five-axis linkage numerical control system, the actual machining trajectory is a spatial curve, the deviation between this curve and the theoretical interpolation trajectory is called nonlinear error. As shown in the following figure, the theoretical interpolation trajectory is a spatial straight line, but the actual machining trajectory is an irregular spatial curve. Figure 5

[0060] ​When the tool of the five-axis machine tool moves from one tool position to another tool position, the tool position and the tool axis vector of the tool will change, so the translational axis and the rotational axis need to move simultaneously, but the coupling movement of the translational axis and the rotational axis will produce nonlinear errors. In the processing of the worktable to process the approximate circular arc, the rotational movement of the worktable is adjusted in the opposite direction to make the workpiece and the tool have relative rotational movement, and only the tool position needs to be changed relative to the workpiece when a single approximate circular arc is processed, so nonlinear errors will not be produced. When multiple approximate circular arcs are processed, the tool position and the tool axis vector of the tool are changed independently, for example, the tool axis vector of the tool is kept unchanged when the tool position i is kept unchanged, the center positioning worktable is rotated to move the tool to the position of the tool position i+1, then the tool axis vector of the tool is changed when the tool position i+1 is kept unchanged, or the tool axis vector of the tool is changed when the tool position i is kept unchanged, and then the center positioning worktable is rotated to move the tool to the tool position i+1 when the tool axis vector is kept unchanged. In summary, in order to prevent nonlinear errors, the tool position and the tool axis vector of the tool cannot be changed simultaneously, as shown in Figure 6 .

[0061] 5) According to the center and the radius of the next approximate circular arc in the current tool trajectory plane curve, repeat 3)-4), process the corresponding approximate circular arc and drive the tool to work to the next tool position, until all the approximate circular arcs in the current tool trajectory plane curve are processed;

[0062] 6) Adjust the posture of the workpiece by adjusting the workpiece posture adjustment worktable lower table 2 and the workpiece posture adjustment worktable upper table 1, so that the machining surface of the dynamically adjustable seven-axis worktable coincides with the plane where the next tool trajectory plane curve is located, at this time the tool position on the workpiece will change, if the tool position of the gantry five-axis machine tool changes simultaneously with the change of the tool position of the workpiece, at this time nonlinear errors will be produced, so the tool position of the gantry five-axis machine tool needs to be changed first to exit the machining and cannot interfere with the rotation of the workpiece. When the workpiece posture adjustment is completed, the tool position is moved to the position of the first tool position of the current tool trajectory plane curve;

[0063] 7) Repeat 3)-6), process the corresponding tool trajectory plane curve according to the center and the radius of all the approximate circular arcs of the remaining tool trajectory plane curves in the current tool trajectory space curve, until the current tool trajectory space curve is processed;

[0064] 8) Repeat 7), process the remaining tool trajectory space curve, until the actual space surface is processed to realize the finishing machining of the workpiece, so as to obtain the target workpiece.

[0065] Therefore, the worktable needs to work together with the gantry type five-axis linkage machine tool, and the gantry type five-axis linkage machine tool first performs rough machining and then combines the worktable to perform final finishing machining.

[0066] The above examples are used to explain and illustrate the present application, but not to limit the present application, and any modification and change made to the present application within the spirit and protection scope of the claims falls into the protection scope of the present application.

Claims

1. A method for using a dynamically adjustable seven-axis workbench capable of eliminating nonlinear errors in curved surface machining, characterized in that: The dynamically adjustable seven-axis workbench capable of eliminating nonlinear errors in curved surface machining comprises a center positioning workbench, a reverse adjustment workbench, and a workpiece posture adjustment workbench, wherein the center positioning workbench is fixedly mounted on a machine tool frame, the reverse adjustment workbench is rotatably mounted on the center positioning workbench, the workpiece posture adjustment workbench is rotatably mounted on the reverse adjustment workbench, and the workpiece to be machined is fixedly mounted on the workpiece posture adjustment workbench; The center positioning workbench comprises a center positioning workbench lower platform (8), a center positioning workbench middle platform (7) and a center positioning workbench upper platform (6); the center positioning workbench lower platform (8) is fixedly mounted on the machine tool frame, the center positioning workbench middle platform (7) is slidably mounted on the center positioning workbench lower platform (8), the center positioning workbench upper platform (6) is slidably mounted on the center positioning workbench middle platform (7), the sliding direction of the center positioning workbench middle platform (7) on the center positioning workbench lower platform (8) is perpendicular to the sliding direction of the center positioning workbench upper platform (6) on the center positioning workbench middle platform (7), and the reverse adjustment workbench is rotatably mounted on the center positioning workbench upper platform (6); The reverse adjustment workbench comprises a reverse adjustment workbench lower platform (5), a reverse adjustment workbench middle platform (4) and a reverse adjustment workbench upper platform (3); the reverse adjustment workbench lower platform (5) is rotatably mounted on the center positioning workbench, the reverse adjustment workbench middle platform (4) is slidably mounted on the reverse adjustment workbench lower platform (5), the reverse adjustment workbench upper platform (3) is slidably mounted on the reverse adjustment workbench middle platform (4), the sliding direction of the reverse adjustment workbench middle platform (4) on the reverse adjustment workbench lower platform (5) is perpendicular to the sliding direction of the reverse adjustment workbench upper platform (3) on the reverse adjustment workbench middle platform (4), and the workpiece posture adjustment workbench is rotatably mounted on the reverse adjustment workbench upper platform (3); The workpiece posture adjustment workbench comprises a workpiece posture adjustment workbench lower platform (2) and a workpiece posture adjustment workbench upper platform (1); an upwardly extending mounting frame is provided on the reverse adjustment workbench, the workpiece posture adjustment workbench lower platform (2) is rotatably mounted in the mounting frame on the reverse adjustment workbench, the workpiece posture adjustment workbench upper platform (1) is rotatably mounted on the workpiece posture adjustment workbench lower platform (2), the rotation axis of the reverse adjustment workbench lower platform (5) is perpendicular to the rotation axis of the workpiece posture adjustment workbench lower platform (2), and the rotation axis of the workpiece posture adjustment workbench lower platform (2) is perpendicular to and intersects with the rotation axis of the workpiece posture adjustment workbench upper platform (1); The method comprises the following steps: 1) Discretize all tool path spatial curves on the workpiece spatial surface into corresponding multiple tool path plane curves; determine multiple approximate arcs corresponding to each tool path plane curve, and then calculate the center and radius of the multiple approximate arcs; determine the initial tool path spatial curve and the corresponding initial tool path plane curve; 2) The workpiece to be machined is fixedly mounted on the workpiece posture adjustment table, the dynamically adjustable seven-axis table is fixedly mounted on the gantry-type five-axis linkage machine tool and restored to its initial position, and the workpiece posture adjustment table is adjusted so that the plane of the current tool path plane curve coincides with the machining plane of the dynamically adjustable seven-axis table; 3) Based on the center position and radius of each approximate arc, the center positioning table and the tool of the gantry-type five-axis linkage machine tool are adjusted. By reversely adjusting the rotational motion between the table and the center positioning table, relative motion is generated between the tool and the workpiece to be machined, and the current approximate arc is machined on the workpiece to be machined. During the current machining process, the tool position and tool axis vector remain unchanged, completing the machining of the current approximate arc. 4) The reverse adjustment table is adjusted in the opposite direction according to the translational motion of the center positioning table, so that the position of the workpiece to be processed and the position of the tool do not change. Then, the reverse adjustment table is driven to rotate on the center positioning table, and the tool position point and tool axis vector of the tool are independently changed, so that the tool moves to the next tool position point. 5) According to the center and radius of the next approximate arc in the current tool path plane curve, repeat 3)-4) to process the corresponding approximate arc and drive the tool to the next tool position until all approximate arcs in the current tool path plane curve are traversed and processed; 6) Adjust the posture of the workpiece to be processed by adjusting the workpiece posture adjustment table so that the processing surface of the dynamically adjustable seven-axis table coincides with the plane of the next tool path plane curve, and then move the tool position point to the position of the first tool position point of the current tool path plane curve; 7) Repeat 3)-6) to process the corresponding tool path plane curve according to the center and radius of all approximate arcs of the remaining tool path plane curves in the current tool path space curve until the current tool path space curve is processed; 8) Repeat step 7) to traverse the remaining tool path space curves until the actual space surface is obtained, thereby obtaining the target workpiece.

2. The method for using a dynamically adjustable seven-axis workbench capable of eliminating nonlinear errors in curved surface machining according to claim 1, characterized in that: In the workpiece space surface, each tool path space curve is discretized into multiple tool path plane curves by the following method: Each tool path space curve is composed of multiple discrete tool position points. It is determined in turn whether adjacent tool position points are located on the same plane and the turning point between two adjacent planes is determined, so as to determine each plane. Each tool path plane curve is composed of the tool position points in each plane.

3. The method for using a dynamically adjustable seven-axis workbench capable of eliminating nonlinear errors in curved surface machining according to claim 1, characterized in that: In the above 4), by driving the reverse adjustment table to rotate on the center positioning table, the tool position point and tool axis vector of the tool are changed independently, so that the tool moves to the next tool position point, specifically: The tool axis vector remains unchanged at the previous tool position location, and the reverse adjustment table is driven to rotate on the circle center positioning table so that the tool moves to the next tool position location. Then, the tool axis vector of the tool position location is changed while the tool remains at the next tool position location. Alternatively, the tool axis vector of the tool position location is changed while the previous tool position location remains unchanged. Then, the reverse adjustment table is driven to rotate on the circle center positioning table while the tool axis vector remains unchanged so that the tool moves to the next tool position location.

4. The method for using a dynamically adjustable seven-axis workbench capable of eliminating nonlinear errors in curved surface machining according to claim 1, characterized in that: In the above 2), the workpiece to be machined is a workpiece that has been rough-machined by a gantry-type five-axis linkage machine tool.

5. The method for using a dynamically adjustable seven-axis workbench capable of eliminating nonlinear errors in curved surface machining according to claim 1, characterized in that: In the above 3), the position of the axis of the center positioning worktable is adjusted according to the position of the center of each approximate arc, so that the axis of the center positioning worktable and the center of the approximate arc coincide with each other, and the position of the tool position point of the gantry-type five-axis linkage machine tool is adjusted according to the radius corresponding to each approximate arc, so that the position of the tool contact point is on the arc line of the approximate arc, and the rotational motion between the worktable and the center positioning worktable is reversely adjusted to make the tool and the workpiece to be processed move relative to each other and process the current approximate arc on the workpiece to be processed.

6. The method for using a dynamically adjustable seven-axis workbench capable of eliminating nonlinear errors in curved surface machining according to claim 1, characterized in that: At the initial position, the rotation axis of the reverse adjustment table is coaxial with the rotation axis of the upper table (1) of the workpiece posture adjustment table.

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