Control device, control method, and control program

Abstract

To enable accurate and efficient machining.SOLUTION: A control device includes a posture information generation unit that, in position posture control of a tool in a five-axis machine, specifies a posture by an azimuth angle and a zenith angle at a position of a point on a curve generated on a unit spherical surface, and outputs posture data for continuously controlling a posture change of a tool axis. For machining position data regarding a movement path based on a position and a posture of a center of a tool tip obtained from a shape of a to-be-machined object, the posture information generation unit generates a curve on a unit spherical surface as an input point in which an angle in a normal direction is inclined according to a path movement direction to each point sampled from the machining position data, adds posture information to each point of the machining position data in accordance with the input point on the curve, and outputs the result as posture data.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present disclosure relates to a control device, a control method, and a control program for controlling a five-axis machine tool.

Background Art

[0002] Conventionally, there has been a technology related to the control of a five-axis machine tool. In recent years, due to the development of micro-nano technology, manufacturing has become more complex and sophisticated, and there is a strong demand for higher precision and higher efficiency of industrial five-axis machine tools. Here, the five-axis machine tool includes a machine tool that performs removal / machining or addition / machining using a rotary cutting tool such as a ball end mill, and a 3D printer having a printer nozzle.

[0003] For example, there is a technology for shortening the machining time by realizing machining considering the error of the rotating axis (see Patent Document 1). In this technology, the rotation angle around the first axis and the rotation angle around the second axis when moving the posture are calculated.

[0004] Also, there is a technology for reducing machining errors due to the inclination and shaft runout of the rotating axis of a five-axis machine tool (see Patent Document 2). In this technology, the correction rotation angle of each rotating axis for correcting the posture error of the tool is calculated, and around the axis, the tilt table is rotated by the correction rotation angle to perform five-axis control.

[0005] Also, there is a technology for creating NC data that suppresses sudden changes in the tool angle and tool position with respect to a NC machine tool (see Patent Document 3). In this technology, it is determined whether the tool spindle direction vector at each point of the tool tip position coincides with the second rotation axis, and if it coincides, the angle at the surrounding points that do not coincide with the second rotation axis is taken out and curve interpolation is performed to create the angle at that point.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

[0007] [Non-Patent Document 1] S. Tajima, B. Sencer, “Accurate real-time interpolation of 5-axis tool-paths with local corner smoothing,” International Journal of Machine Tools and Manufacture, 142(2019) 1-15. [Non-Patent Document 2] Z. Yan, S. Schiller, G. Wilensky, N. Carr, S. Schaefer, κ-Curves: Interpolation at Local Maximum Curvature, TOG, 36(4), 129, 2017. [Overview of the project] [Problems that the invention aims to solve]

[0008] However, controlling tools in 5-axis machining centers is extremely complex due to their high degree of freedom. Therefore, CAM and NC (numerical control) software for tool axis control requires advanced mathematical techniques. For example, to ensure constant speed rotation of the tool axis, there is a technique that uses a real-time trajectory generation algorithm with spherical linear interpolation to interpolate the synchronization of translational and rotational tool motion (see Non-Patent Literature 1). However, the mathematical techniques used in the development of 5-axis machining center software have not been sufficiently refined from the standpoint of machining accuracy and efficiency. In particular, there is a problem with the proper control of the orientation data (tool axis angle) associated with the machining position data (CL path) of the tool tip being controlled. As a result, the transmission of rotational power to the machining surface is inefficient, leading to longer machining times and insufficient machining accuracy.

[0009] The object of this disclosure is to provide a control device, a control method, and a control program that enable accurate and efficient processing. [Means for solving the problem]

[0010] The control device of this disclosure is a control device that, in the position and orientation control of a tool in a 5-axis machining center, specifies the orientation by the azimuth angle and zenith angle at the position of a point on a curve generated on a unit sphere and outputs orientation data for continuously controlling the orientation change of the tool axis, wherein the orientation information generation unit generates a curve on a unit sphere as input points with an angle in the normal direction tilted according to the path movement direction at each point sampled from the machining position data, with respect to machining position data relating to the position and orientation of the tool tip center obtained from the shape of the workpiece, and adds orientation information to each point of the machining position data according to the input points on the curve and outputs it as orientation data.

[0011] Furthermore, the control device of this disclosure may be configured such that the attitude information generation unit converts the normal data of each point in the path of the processing position data into polar coordinates of the azimuth angle and zenith angle and smooths it, divides each point from which the normal data has been smoothed into segments corresponding to the path of the processing position data, generates a partial curve for each of the divided segments using the sampled input points, sets parameters for each point between the input points, determines the normal of each point, determines whether the normal data is inside the movable range data that determines the movable range of the path of the processing position data, adds a point inside if it is not inside, and updates the generated curve. This makes it possible to create attitude data that enables high-precision control from the generated curve on a sphere.

[0012] Furthermore, in the control device of this disclosure, the determination of whether the movable range data is inside may be made according to the safety factor defined for the 5-axis machining center. This makes it possible to create posture data while taking safety during machining into consideration.

[0013] In the control device of this disclosure, the movable range data may be defined as cone data, and the determination of the movable range may be made by determining whether or not the normal data lies inside the cone data. This makes it possible to create posture data while taking safety during processing into consideration.

[0014] Furthermore, in the control device of this disclosure, the attitude information generation unit may, with respect to the generation of a partial curve, set the input points as control points for generating the curve and for the initial curve, set a first parameter to determine the endpoint of each partial curve between two points connecting the input points so that it is the midpoint of two adjacent input points, set a second parameter for the curve at each point where the curvature extremum takes place in the segment of each partial curve, and generate the curve by updating the position of the input points while updating the first and second parameters until the point where the curvature extremum converges to the input point. This makes it possible to optimize the curve for attitude control.

[0015] Furthermore, in the control device of this disclosure, the attitude information generation unit may generate the curve as a spherical curve that satisfies at least one of the following characteristics: it is a curve that passes through all the input points, all input points are points of maximum geodetic curvature, and curvature continuity is guaranteed. This makes it possible to reflect the characteristics of spherical curves such as spherical κ-curves, spherical B-spline curves, spherical Bézier curves, and spherical NURBS curves in attitude control.

[0016] Furthermore, the control method disclosed herein is a control method for controlling the position and orientation of a tool in a 5-axis machining center, in which the orientation is specified by the azimuth angle and zenith angle at the position of a point on a curve generated on a unit sphere, and orientation data is output for continuously controlling the orientation change of the tool axis, wherein a computer performs the following processing: a processor generates a curve on a unit sphere as input points with an angle in the normal direction tilted according to the path movement direction at each point sampled from the machining position data relating to the movement path due to the position and orientation of the center of the tool tip obtained from the shape of the workpiece, and adds orientation information to each point of the machining position data according to the input points on the curve, and outputs it as orientation data.

[0017] Furthermore, the control program disclosed herein is a control program for controlling the position and orientation of a tool in a 5-axis machining center, which specifies the orientation by the azimuth angle and zenith angle at the position of a point on a curve generated on a unit sphere, and outputs orientation data for continuously controlling the orientation change of the tool axis. The processor causes the computer to perform the following processing: generating a curve on a unit sphere as input points with an angle in the normal direction tilted according to the path movement direction at each point sampled from the machining position data, which is machining position data relating to the movement path due to the position and orientation of the center of the tool tip obtained from the shape of the workpiece; adding orientation information to each point of the machining position data according to the input points on the curve; and outputting it as orientation data. [Effects of the Invention]

[0018] According to the control device, control method, and control program of the present disclosure, an effect of enabling accurate and efficient machining can be obtained.

Brief Description of the Drawings

[0019] [Figure 1] An example of a drill with a cutting edge, which is a tool of a 5-axis machining center. [Figure 2] An example of specifying the posture of a tool. [Figure 3] This is a schematic block diagram of a computer that functions as the control device of the present embodiment. <000A098> [Figure 4] This is a block diagram showing an example of the functional configuration of the control of the present embodiment. [Figure 5] An example of machining position data when the machining target is one tooth. [Figure 6] This is an example of conical data showing the range of postures that do not interfere with each point. [Figure 7] This is an example showing the tool posture generated for a short, single closed machining position data as a path. [Figure 8] An example of the generated spherical κ-curve. [Figure 9] This is a graph showing that the spherical κ-curve becomes a maximum point of geodesic curvature at all input points and the curvature continuity is guaranteed. [Figure 10] This is a diagram showing an example of a path of machining position data to which posture information is assigned. [Figure 11] This is a diagram showing machining position data (posture data) to which posture information is assigned. [Figure 12] This is a flowchart showing the flow of control processing by the control device. [Figure 13] This is a flowchart of curve generation processing.

Mode for Carrying Out the Invention

[0020] An example of an embodiment of the disclosed technology will be described below with reference to the drawings. In each drawing, identical or equivalent components and parts are given the same reference numerals. Furthermore, the dimensional ratios in the drawings are exaggerated for illustrative purposes and may differ from actual ratios.

[0021] An overview of the embodiments of this disclosure will be described. The technology of this embodiment aims to dramatically improve machining efficiency, machining accuracy, and machining speed by using a method to precisely control and optimize the orientation of the tool axis using a new mathematical method. In particular, by using a newly defined spherical κ-curve as a mathematical method for controlling the orientation of the tool and nozzle, it becomes possible to increase the precision and speed of 5-axis removal machining and 5-axis additive machining. The spherical κ-curve is composed of quadratic spherical Bézier curves (curve segments), which are connected so that the geodetic curvature is continuous, and is generated so that the "points of passage" coincide with the extreme values ​​of the geodetic curvature of each segment. In this embodiment, the κ-curve is described as a representative example, but any curve that can be applied to a sphere is acceptable, and various spherical curves such as spherical B-spline curves, spherical Bézier curves, and spherical NURBS curves can also be used.

[0022] The planar kappa curve (see Non-Patent Literature 2), which forms the basis of the kappa curve idea, is a curve composed of a series of quadratic Bézier curves. The advantages of the kappa curve are as follows: (1) The input points for generating the curve are the curvature extrema. (2) The curvature is continuous between segments except at inflection points. (3) Each segment has at most one curvature extremum. (4) It has a smooth curvature distribution due to its low degree of 2. However, because it is a quadratic curve, it does not have enough degrees of freedom, and the curvature extrema cannot be increased or decreased.

[0023] Furthermore, previous extensions of Bézier curves have primarily focused on connecting multiple segments; for example, defining the curve with four control points to independently guarantee tangents and curvature continuity at the start and end points has been the mainstream approach. Contrary to this research trend, the kappa curve uses a quadratic Bézier curve defined by three input points (control points) to control the position of the curvature extremum at a specific point on the curve, rather than at the endpoints.

[0024] In this embodiment, a spherical κ-curve is used for attitude control of a 5-axis machining center to achieve (1) the ability to control the magnitude of the curvature extrema, and (2) the ability to efficiently optimize attitude control due to its low order, thereby enabling higher precision and reduced machining time.

[0025] This section explains the advantages of the spherical κ-curve. Free curves on a sphere, such as spherical Bézier curves, are used in Non-Patent Literature 1, etc., concerning 5-axis machining. While Non-Patent Literature 1 uses methods for spherical curves, research on free curves on a unit sphere has not progressed. However, mathematically, research on the properties of surfaces on an n-dimensional sphere Sn is progressing, and theoretical development continues. The κ-curve was proposed relatively recently, in 2017, and no κ-curves on a unit sphere based on its method have been proposed. Table 1 shows the correspondence between methods used for attitude control, ease of specification, presence or absence of singularities, controllability of velocity and acceleration, and characteristics. In the absence of singularities, the generation of control noise can be suppressed. [Table 1]

[0026] Table 1 lists the following methods used for attitude control: 1. rotation angle due to the machine mechanism, 2. Euler angle, 3. unit quaternion, and 4. spherical κ-curve proposed in this embodiment. Among these methods, the spherical κ-curve is suitable for controlling geodetic curvature, and by optimizing velocity and acceleration using this curve, attitude can be accurately controlled.

[0027] Regarding 5-axis machining centers, progress is being seen in the 5-axis additive machining field, compared to the 5-axis subtractive machining field, with the spread of 3D printers. In the 5-axis additive machining field, there is a method called FDM (Fused Deposition Modeling) that melts plastic with heat and adds it to a three-dimensional object to create it. In this method, high rigidity is achieved by controlling the direction of filament extrusion by 5-axis FDM by controlling the position and orientation of the base using a robotic arm. It has been pointed out that three points are important for high-precision molding: continuity of nozzle position, continuity of orientation, and continuity of robotic arm pose. However, efforts to develop a mathematical framework for orientation control have not yet been considered. The spherical κ-curve for orientation control proposed in this embodiment is effective for both 5-axis subtractive machining and 5-axis additive machining.

[0028] (Principles of attitude control) This section explains the principle of attitude control for 5-axis machining centers. In a 5-axis machining center, for example, in ball end milling of drilling tools, a drill with a cutting edge as shown in Figure 1 is used as the tool. There are 3 degrees of freedom in attitude control, and rotation around the x, y, and z axes can be considered. The tool tip is hemispherical, and in machining, it is necessary to offset the center of the tool tip from the machining surface by the radius r of the hemisphere, and specify the position of the center of the tool tip and the direction of the tool axis. Three degrees of freedom are required to specify the attitude, but the tool rotates at high speed around the tool axis, so it is not necessary to control this degree of freedom. Therefore, the degrees of freedom for rotation around the axis are 2. Similarly, in nozzle control of a 3D printer, even if the nozzle rotates around its axis, the filament is melted and soft, so the filament hardly rotates, and therefore the degrees of freedom for rotation around the axis are 2.

[0029] Therefore, as shown in Figure 2, the orientation around the two axes is specified by the angles θ and φ, with r fixed as 1 in polar coordinates. Hereinafter, r is the radial radius, θ is the azimuth angle, and φ is the zenith angle. The upper part of Figure 2 shows the relationship between r, θ, and φ in coordinate space, and the lower part of Figure 2 shows the tool orientation specified by the angles θ and φ. In the orientation representation of this embodiment, a curve, i.e., a spherical κ-curve, is generated on a unit sphere, and the orientation of the tool axis is specified by the angle (azimuth angle θ and zenith angle φ) based on the position of a point on this curve. In this way, in the position and orientation control of the tool in a 5-axis machining center, the orientation is specified by the azimuth angle and zenith angle at the position of a point on a curve generated on a unit sphere, and orientation data is output to continuously control the change in the orientation of the tool axis. By moving the center of the machining position along the curve in accordance with the change in the position of the tool tip and gradually changing it, the change in the orientation of the tool axis can be continuously controlled.

[0030] Methods using spherical κ-curves enable mechanically superior attitude control by generating a curve by specifying the geodetic curvature maxima. A spherical κ-curve is defined as follows: (1) it is a curve that passes through all input points, (2) all input points are geodetic curvature maxima (positions with the greatest acceleration and load), and (3) curvature continuity (G2 continuity) is guaranteed. Details of the spherical κ-curve generation method and the method for adding attitude data to the spherical κ-curve will be described later.

[0031] The point where geodetic curvature is maximum corresponds to the point where the mechanism's acceleration is maximum in attitude control. By controlling the position of this point, it is possible to control points of large attitude changes. With a 5-axis machining center, this contributes to the formation of high-quality machined surfaces and reduces the time required for machining. With a 3D printer, the time required for shape generation is reduced, and the nozzle attitude can be controlled more smoothly, contributing to improved accuracy of the created shape.

[0032] Figure 3 is a block diagram showing the hardware configuration of the control device 100.

[0033] As shown in Figure 3, the control device 100 includes a CPU (Central Processing Unit) 11, a ROM (Read Only Memory) 12, a RAM (Random Access Memory) 13, storage 14, an input unit 15, a display unit 16, and a communication interface (I / F) 17. Each component is connected to the others via a bus 19 so as to be able to communicate with each other. The CPU is the processor of this disclosure.

[0034] The CPU 11 is a central processing unit that executes various programs and controls various components. Specifically, the CPU 11 reads a program from the ROM 12 or storage 14 and executes the program using the RAM 13 as a working area. The CPU 11 controls each of the above components and performs various calculations according to the program stored in the ROM 12 or storage 14. In this embodiment, a prediction program is stored in the ROM 12 or storage 14.

[0035] ROM12 stores various programs and data. RAM13 temporarily stores programs or data as a working area. Storage14 consists of a storage device such as an HDD (Hard Disk Drive) or SSD (Solid State Drive) and stores various programs, including the operating system, and various data.

[0036] The input unit 15 includes a pointing device such as a mouse and a keyboard, and is used for various types of input.

[0037] The display unit 16 is, for example, a liquid crystal display and displays various information. The display unit 16 may also function as an input unit 15 by employing a touch panel system.

[0038] The communication interface 17 is an interface for communicating with other devices such as terminals. For such communication, a wired communication standard such as Ethernet (registered trademark) or FDDI, or a wireless communication standard such as 4G, 5G, or Wi-Fi (registered trademark) may be used.

[0039] The functional configurations of the control device 100 will now be described. Figure 4 is a block diagram showing the configuration of the control device 100 in this embodiment. The control device 100 communicates with the 5-axis machining center 130 via the communication interface 17 and outputs attitude data for control to the 5-axis machining center 130. Each functional configuration is realized by the CPU 11 reading a control program stored in the ROM 12 or storage 14, expanding it into the RAM 13, and executing it. The 5-axis machining center 130 controls the tool based on the received attitude data and performs machining on the workpiece.

[0040] As shown in Figure 4, the control device 100 functionally comprises a storage unit 102 and a posture information generation unit 104. The posture information generation unit 104 comprises a preprocessing unit 110, a curve generation unit 112, and an allocation unit 114.

[0041] The memory unit 102 stores pre-generated machining position data (CL data). The machining position data may be received from a CAM (not shown) as an external device, or from a calculation unit with CAM calculation capabilities located inside the control device 100. The machining position data is data relating to the movement path based on the position and orientation of the tool tip center obtained from the shape of the workpiece, and is generated as a set of "each closed machining position data path (CL path)". Note that the processing of each part below is performed by obtaining the machining position data from the memory unit 102.

[0042] Figure 5 shows an example of machining position data when the workpiece is a single tooth. The tooth in Figure 5 is drawn as a set of points of machining position data plotted in 3D space. Note that each axis in 3D space is represented by X, Y, and Z coordinates. As shown in Figure 6, it is assumed that the generated machining position data has been preprocessed to include a range of non-interference orientations for each point, represented as a cone, to prevent interference with the workpiece or jig. The cone has a risk factor (1 / safety factor) = θ for the azimuth angle θ. R / θ C The range is defined. The safety factor is assumed to be 0.9, for example. Figure 7 is an example showing the tool orientation as a path generated for a short, closed machining position data. In the three-dimensional space of Figure 7, each axis is represented by X, Y, and Z coordinates. A single closed machining position data is a path of movement trajectory connecting each point of the movement position, and is an example of a path containing about 30 points. Note that in the example in Figure 7, a small number of points is shown for illustrative purposes, but many more points (hundreds of points, etc.) are expected. A vector of the orientation direction (normal direction) of the axis corresponding to each point of the machining position data is shown.

[0043] The posture information generation unit 104 generates a spherical κ-curve on a unit sphere as input points, with each point sampled from the path of the machining position data tilted at an angle in the normal direction according to the path movement direction. The posture information generation unit 104 adds posture information to each point in the path of the machining position data according to the input points in the spherical κ-curve and outputs it as posture data.

[0044] The posture information generation unit 104 performs the following processing on each closed machining position data path. It also reads cone data for interference checking with the machining position data path.

[0045] The preprocessing unit 110 converts the normal data of each point in the machining position data path into polar coordinates of azimuth angle θ and zenith angle φ, and then smooths it. The preprocessing unit 110 also divides each point from which the normal data has been smoothed into segments corresponding to the machining position data path.

[0046] The smoothing and splitting processes of the preprocessing unit 110 described above will now be explained. The smoothing process converts the normal data of the unit spherical data into polar coordinates (θ, φ) and performs discrete smoothing using a moving average (low pass filter). Approximately 7 to 15 points are used in the smoothing process. Next, the splitting process divides each point of the smoothed normal data into segments corresponding to the path of the machining position data. A segment is a unit of a curve and is a curve segment that can be described by a single mathematical formula. The segments are obtained by dividing a closed path of the machining position data as shown in Figure 7 above, and for example, the segments are divided so that each segment has approximately 30 to 40 points.

[0047] The curve generation unit 112 generates a spherical κ-curve on a unit sphere for each segment. For example, it samples several points (e.g., 5-7 points or 6-8 points) from the divided points, tilts them by an angle α degrees (e.g., α=15) in the path movement direction, and uses these points as input points for the spherical κ-curve. In other words, the input points are points sampled for each segment of the path of the machining position data. Figure 8 shows an example of a generated spherical κ-curve. Note that in Figure 8, for the sake of explanation, an example of the movement trajectory of the entire closed path is shown. However, since a spherical κ-curve is generated for each segment, a spherical κ-curve of a partial arc of the circumference is generated. If there are N partial arcs connecting the circumference, for example, by joining the endpoints of the first (nth) segment and the second (n+1) segment to coincide, a spherical κ-curve for one full circle of the closed path of the machining position data is generated. In Figure 8, CL, shown on the central axis of the cone of the unit sphere S, represents the orientation data attached to the machining position data path. This CL indicates the movement of the axis orientation using a conventional method that does not use a spherical κ-curve. In Figure 8, each input point is connected to draw the curve CV. It can be seen that the change in axis orientation according to this embodiment is significantly smoother and more mechanically efficient than conventional axis orientation movements because it moves along the spherical κ-curve shown by CV. In the example in Figure 8, there are 7 points for the entire circumference, but it is assumed that several points will be sampled for a portion of the arc.

[0048] Here, we will explain the algorithm for generating spherical kappa curves. The algorithm for generating spherical kappa curves performs the following steps 1 to 4. The update method during processing will be explained later in the explanation of the principle.

[0049] 1. Input a passing point on the unit sphere as the input point. Below, a curve is generated such that the input point (passing point) becomes the curvature extremum of the spherical κ-curve. 2. The input points are set as control points for the initial curve. The input points become the initial values ​​for the control points used to define the spherical κ-curve. Control points are points specified for generating the curve. In this embodiment, the input points sampled for each segment are used as control points for the initial curve, and the control point positions are optimized while updating the parameters. This sets up each subcurve connecting the input points. Each subcurve is a subcurve between two points that are further parts of the arc of the segment, connecting point n and point n+1. The control points are set by setting the first parameter λi, which determines the endpoints of each subcurve, to 0.5, and setting the input point n of interest to be the midpoint of two adjacent input points (input point n-1 and input point n+1). In addition, the second parameter ti, which relates to the curve at each point where the curvature extremum occurs in each subcurve segment, is set to 0.5. Note that the values ​​of the first parameter λi and the second parameter ti are examples. 3. The position of the control points is optimized using the following process until the point of curvature extremum converges to the input point. 3.1: Update the first parameter λi so that the curvature coincides at the endpoints of two adjacent subcurves. 3.2: Update the position of the control point using the updated first parameter λi. 3.3: Update the second parameter ti using the updated control points. 3.4: Optimize the position of the control points using the updated second parameter ti so that the input points are the points where the curvature extrema occurs. 4. Generate a curve (spherical κ-curve of the segment) from the obtained control points.

[0050] Furthermore, as shown in Figure 9, the geodetic curvature of the spherical κ-curve is a curve that passes through all input points, and all input points are points of geodetic curvature maxima, thus guaranteeing curvature continuity. In the graph of Figure 9, the vertical axis shows the geodetic curvature, and the horizontal axis shows the parameters of the spherical κ-curve.

[0051] (Principle of calculating spherical κ-curve / geodetic curvature) Here, we will explain the principle of calculating the spherical κ-curve / geodetic curvature.

[0052] The curvature at the endpoint (t=0) of the quadratic spherical Bézier curve for the following control points is calculated. To change the value of the curvature extrema of the spherical κ-curve, a method of rationalizing the quadratic spherical Bézier curve is assumed. Assuming that the quadratic spherical Bézier curve lies exactly on the unit sphere, and that its normal curvature coincides with the outward normal of the unit sphere, it is always 1. Therefore, the geodesic curvature is calculated as follows.

[0053] First, without losing generality, we set the control points as shown in equation (1-1) below.

number

[0054] Furthermore, when equation (1-1) is true, the relationship shown in equation (1-2) follows.

number

[0055] The z component of the second derivative of C(ν) is given by equation (1-3) below.

number

[0056] The normal vector at point P0 is (1,0,0), and the geodetic curvature is κ. gThis is given as the z component of the curvature vector κ. The curvature vector κ is calculated using equation (1-4) below.

number

[0057] geodetic curvature κ g The calculation of d 2 C(0) / dν 2 We only need to consider the z component. Therefore, we obtain equation (1-5) below.

number

[0058] To ensure continuity of geodetic curvature at segment connection points, we need to find λ (first parameter λi) that satisfies equation (1-6) below. The first parameter λi in 3.1 above is updated using equation (1-6). The position of the control point in 3.2 is updated by feeding back the values ​​of θ and φ that satisfy equation (1-6) to equation (1-1).

number

number

[0059] The allocation unit 114 sets parameters for each point between the input points of the spherical κ-curve for each generated segment and determines the normal for each point. Here, the parameter values ​​of each segment of the spherical curve are divided according to the number of points between the two input points, and the normal for each point is determined by setting parameter values ​​for the divided points between the input points. The normal determined here becomes the angle (θ, φ) as orientation information of the tool (ball end mill). The parameter values ​​to be divided here are the parameters used in the definition of the spherical κ-curve shown in Figure 9. Even if the parameters are divided into equal intervals, the distances between points on the sphere corresponding to those parameter values ​​(distances as great circles) are generally not equal intervals. Here, firstly, this matter is ignored, and the parameter values ​​are divided equally according to the number of points. Alternatively, secondly, the parameter values ​​are determined so that the distances on the sphere are equal intervals. However, in the second case, the processing time may increase, so it is generally sufficient to use the first equal division.

[0060] Next, the allocation unit 114 determines whether the normal data lies inside the cone data. If it does not, it adds a point inside and updates the generated spherical κ-curve. The spherical κ-curve is updated repeatedly until the normals of all points lie inside the cone data. The spherical κ-curve generated for each segment is concatenated to form the final spherical κ-curve for the machining position data. The cone data is an example of the operating range data in this disclosure, and the area inside the cone data is an example of the movable range.

[0061] The assignment unit 114 assigns orientation information to all points in the machining position data path for each closed machining position path using the finally generated spherical κ-curve. In this way, orientation data is obtained for all machining position data paths. Figure 10 shows an example of a machining position data path to which orientation information has been assigned. The orientation information is in the axial direction shown in Figure 1, from the tool tip center to the tool axis center. Therefore, as shown in Figure 10(a), it is basically the same orientation (no forward tilt) as the surface direction of the workpiece. In this case, to improve the quality of the machined surface, the tool may be tilted forward in the direction of travel (for example, 15 degrees forward tilt). In Figure 10(b), the orientation was generated with an overall forward tilt by changing the passing points of the spherical κ-curve to positions with a forward tilt.

[0062] Figure 11 shows machining position data (position data) to which position information is assigned. In the example in Figure 11, it is assumed that the tool approaches from above (the top of the tooth) in the first half of machining, and from below (the bottom of the tooth) in the second half of machining. The position information generation unit 104 outputs the position data to the 5-axis machining center 130. The position data is also stored in the storage unit 102.

[0063] (Process flow) Next, the operation of the control device 100 will be explained. Figure 12 is a flowchart showing the flow of control processing by the control device 100. The CPU 11 reads the learning program from the ROM 12 or storage 14, loads it into the RAM 13, and executes it, thereby performing the learning process. The CPU 11 functions as a part of the control device 100 to perform the following processes.

[0064] In step S100, the CPU 11 selects the path (CL path) of the target machining position data.

[0065] In step S102, the CPU 11, acting as a preprocessing unit 110, converts the normal data of each point in the path of the machining position data into polar coordinates of azimuth angle θ and zenith angle φ, and then smooths it.

[0066] In step S104, the CPU 11, acting as a preprocessing unit 110, divides each point from which the normal data has been smoothed into segments corresponding to the path of the machining position data.

[0067] In step S106, the CPU 11, as the curve generation unit 112, generates a spherical κ-curve on the unit sphere for each segment. The generation of the spherical κ-curve is described in a subroutine.

[0068] In step S108, the CPU 11, as an allocation unit 114, sets parameters for each point between the input points of the spherical κ-curve of each generated segment and determines the normal of each point.

[0069] In step S110, the CPU 11, as the allocation unit 114, selects a point to be judged from each point whose normal vector has been determined.

[0070] In step S112, the CPU 11, acting as the allocation unit 114, determines whether the normal data for the selected point lies inside the cone data. If it lies inside, the process proceeds to step S116; otherwise, the process proceeds to step S114.

[0071] In step S114, the CPU 11, as the allocation unit 114, adds points to the interior and updates the generated spherical κ-curve.

[0072] In step S116, the CPU 11, acting as the allocation unit 114, determines whether or not the determination has been completed for all points. If it has been completed, the process proceeds to step S114. If it has not been completed, the process returns to step S110 and is repeated.

[0073] In step S118, the CPU 11, as an assignment unit 114, assigns orientation information to all points along the machining position data path using the ultimately generated spherical κ-curve.

[0074] In step S120, the CPU 11, acting as the posture information generation unit 104, determines whether or not it has finished processing all paths of the machining position data. If it has finished, it proceeds to step S122. If it has not finished, it returns to step S100 and repeats the process.

[0075] In step S122, the CPU 11 outputs orientation data for all machining position data paths to the 5-axis machining center 130, stores it in the memory unit 102, and terminates the process.

[0076] The process of generating the spherical κ-curve in step S106 will now be explained. Figure 13 is a flowchart of the curve generation process.

[0077] In step S200, the CPU 11 inputs a point on the unit sphere (a point that represents an extreme curvature).

[0078] In step S202, the CPU 11 sets the input point as the control point of the initial curve.

[0079] In step S204, the CPU 11 updates the first parameter λi so that the curvatures of two adjacent subcurves coincide at their endpoints.

[0080] In step S206, the CPU 11 updates the position of the control point using the updated first parameter λi.

[0081] In step S208, the CPU 11 updates the second parameter ti using the updated control points.

[0082] In step S210, the CPU 11 optimizes the position of the control points using the updated second parameter ti so that the points where the curvature extrema occurs become the input points.

[0083] In step S212, the CPU 11 determines whether the points of the curvature extrema have converged to the input points. If it determines that they have converged, it proceeds to step S214. If it determines that they have not converged, it returns to step S204 and repeats the process.

[0084] In step S214, the CPU 11 generates a spherical κ-curve of the segment from the obtained control points.

[0085] As described above, the control device 100 according to this embodiment enables accurate and efficient machining. Furthermore, as shown in Figure 8, by optimizing the spherical κ-curve to control the tool path and orientation, (1) the maximum force applied to the tool can be optimized to be as small as possible. Also, (2) optimization can be performed to minimize the value obtained by integrating the force applied to the tool over time (impulse). This optimization makes it possible to efficiently transmit tool performance to the machined surface. In addition, by drawing a spherical curve on a unit sphere, the orientation of the tool can be continuously controlled, making control easier.

[0086] This disclosure is not limited to the embodiments described above, and various modifications and applications are possible without departing from the spirit of the invention.

[0087] For example, in the above embodiment, the example described was that the range of motion that does not interfere with the workpiece or jig and the data of said range of motion are a cone (cone data), but it is not limited to this. For example, the range of motion data can be a polygon or any other shape and method as long as a non-interfering region can be specified. In addition to interference with the workpiece or jig, the range of motion that does not interfere may also be limited by the physical range of motion of the tool tip, etc.

[0088] Furthermore, although the present specification describes an embodiment in which the program is pre-installed, it is also possible to provide the program stored on a computer-readable recording medium. [Explanation of symbols]

[0089] 100 Control device 102 Storage section 104 Posture information generation section 110 Pre-processing 112 Curve generator 114 Allocation Section 130 5 axis processing machine

Claims

1. A control device for controlling the position and orientation of a tool in a 5-axis machining center, which includes an orientation information generation unit that specifies the orientation by the azimuth angle and zenith angle at the position of a point on a curve generated on a unit sphere and outputs orientation data for continuously controlling the orientation change of the tool axis, The aforementioned posture information generation unit, Regarding machining position data relating to the movement path based on the position and orientation of the tool tip center obtained from the shape of the workpiece, a curve is generated on a unit sphere as input points at each point sampled from the machining position data, with the angle in the normal direction tilted in the normal direction according to the path movement direction. The attitude information generation unit, in generating the curve, For the normal data of each point in the path of the aforementioned processing position data, convert it to polar coordinates of the azimuth angle and zenith angle and smooth it out. Each point obtained by smoothing the normal data is divided into segments corresponding to the path of the processing position data, For each of the divided segments, A partial curve is generated using the sampled input points. Set parameters for each point between the aforementioned input points, and determine the normal vector for each point. The normal data is determined to be inside the movable range data that determines the movable range of the path of the processing position data. If it is not inside, a point is added inside, and the generated curve is updated. The attitude information generation unit, with respect to the generation of the partial curve, A control point for generating the aforementioned curve, wherein the input point is set as a control point for the initial curve, and each subcurve between two points connecting the input points is, A first parameter is set to determine the endpoint of each subcurve so that it is the midpoint of two adjacent input points. A second parameter is set for the curve at each point in the segment of each subcurve that takes on a curvature extremum. The curve is generated by updating the position of the input point while updating the first and second parameters until the point of curvature extremum converges to the input point, and optimizing the process. The system adds orientation information to each point of the processing position data according to the input points in the curve, and outputs it as orientation data. Control device.

2. The control device according to claim 1, wherein the determination of whether the range of motion data is inside the range of motion is determined according to the safety factor set for the 5-axis machining center.

3. The control device according to claim 1, wherein the attitude information generation unit generates the curve as a spherical curve satisfying the following characteristics: that it is a curve that passes through all of the input points, that all input points are points of maximum geodetic curvature, and that the continuity of curvature is guaranteed.

4. In tool position and orientation control for a 5-axis machining center, the orientation is specified by the azimuth angle and zenith angle at the position of a point on a curve generated on a unit sphere, and the change in the orientation of the tool axis is continuously controlled. A control method for outputting posture data for the purpose of The processor generates a curve on a unit sphere as input points, with each point sampled from the machining position data relating to the movement path based on the position and orientation of the tool tip center obtained from the shape of the workpiece, and with the angle inclined in the normal direction according to the path movement direction. In generating the curve, the processor For the normal data of each point in the path of the aforementioned processing position data, convert it to polar coordinates of the azimuth angle and zenith angle and smooth it out. Each point obtained by smoothing the normal data is divided into segments corresponding to the path of the processing position data, For each of the divided segments, A partial curve is generated using the sampled input points. Set parameters for each point between the aforementioned input points, and determine the normal vector for each point. The normal data is determined to be inside the movable range data that determines the movable range of the path of the processing position data. If it is not inside, a point is added inside, and the generated curve is updated. The processor, with respect to the generation of the partial curve, A control point for generating the aforementioned curve, wherein the input point is set as a control point for the initial curve, and each subcurve between two points connecting the input points is, A first parameter is set to determine the endpoint of each subcurve so that it is the midpoint of two adjacent input points. A second parameter is set for the curve at each point in the segment of each subcurve that takes on a curvature extremum. The curve is generated by updating the position of the input point while updating the first and second parameters until the point of curvature extremum converges to the input point, and optimizing the process. The system adds orientation information to each point of the processing position data according to the input points in the curve, and outputs it as orientation data. A control method by which a computer executes a process.

5. A control program for controlling the position and orientation of a tool in a 5-axis machining center, which specifies the orientation by the azimuth angle and zenith angle at the position of a point on a curve generated on a unit sphere, and outputs orientation data for continuously controlling the orientation change of the tool axis, The processor generates a curve on a unit sphere as input points, with each point sampled from the machining position data relating to the movement path based on the position and orientation of the tool tip center obtained from the shape of the workpiece, and with the angle inclined in the normal direction according to the path movement direction. In generating the curve, the processor For the normal data of each point in the path of the aforementioned processing position data, convert it to polar coordinates of the azimuth angle and zenith angle and smooth it out. Each point obtained by smoothing the normal data is divided into segments corresponding to the path of the processing position data, For each of the divided segments, A partial curve is generated using the sampled input points. Set parameters for each point between the aforementioned input points, and determine the normal vector for each point. The normal data is determined to be inside the movable range data that determines the movable range of the path of the processing position data. If it is not inside, a point is added inside, and the generated curve is updated. The processor, with respect to the generation of the partial curve, A control point for generating the aforementioned curve, wherein the input point is set as a control point for the initial curve, and each subcurve between two points connecting the input points is, A first parameter is set to determine the endpoint of each subcurve so that it is the midpoint of two adjacent input points. A second parameter is set for the curve at each point in the segment of each subcurve that takes on a curvature extremum. The curve is generated by updating the position of the input point while updating the first and second parameters until the point of curvature extremum converges to the input point, and optimizing the process. The system adds orientation information to each point of the processing position data according to the input points in the curve, and outputs it as orientation data. A control program that instructs a computer to perform a process.

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