CN114200886A - Transition method and medium for switching among five-axis tool paths and fairing and numerical control equipment of five-axis machine tool - Google Patents

Transition method and medium for switching among five-axis tool paths and fairing and numerical control equipment of five-axis machine tool Download PDF

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CN114200886A
CN114200886A CN202010989138.4A CN202010989138A CN114200886A CN 114200886 A CN114200886 A CN 114200886A CN 202010989138 A CN202010989138 A CN 202010989138A CN 114200886 A CN114200886 A CN 114200886A
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track
axis
transition
speed
switching
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CN114200886B (en
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朱蓓
赵建华
黄云鹰
邱明勇
曾鹏
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Symg Shanghai Intelligence System Co ltd
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    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B19/00—Programme-control systems
    • G05B19/02—Programme-control systems electric
    • G05B19/18—Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of programme data in numerical form
    • G05B19/19—Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of programme data in numerical form characterised by positioning or contouring control systems, e.g. to control position from one programmed point to another or to control movement along a programmed continuous path
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B19/00—Programme-control systems
    • G05B19/02—Programme-control systems electric
    • G05B19/18—Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of programme data in numerical form
    • G05B19/416—Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of programme data in numerical form characterised by control of velocity, acceleration or deceleration
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B19/00—Programme-control systems
    • G05B19/02—Programme-control systems electric
    • G05B19/418—Total factory control, i.e. centrally controlling a plurality of machines, e.g. direct or distributed numerical control [DNC], flexible manufacturing systems [FMS], integrated manufacturing systems [IMS] or computer integrated manufacturing [CIM]
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P90/00—Enabling technologies with a potential contribution to greenhouse gas [GHG] emissions mitigation
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Abstract

The invention provides a transition method and medium for a five-axis tool path switching fairing and numerical control equipment of a five-axis machine tool, wherein the transition method for the five-axis tool path switching fairing comprises the following steps: acquiring instruction information from a processing file of a workpiece, and analyzing the instruction information to acquire a five-axis track of the workpiece during processing; at least two sections of the five-axis trajectories are subjected to trajectory preprocessing; constructing a transfer transition curve between two adjacent preprocessed tracks; and optimizing the machining track of the cutter according to the speed constraint and the interpolation point of the switching transition curve. The invention provides a transition method for switching smoothness, which can ensure the processing precision of a workpiece and ensure that the feeding speed/acceleration/jerk of a cutter is in a range allowed by a system.

Description

Transition method and medium for switching among five-axis tool paths and fairing and numerical control equipment of five-axis machine tool
Technical Field
The invention belongs to the technical field of five-axis machining, relates to a transition method of a switching fairing, and particularly relates to a transition method and medium of a five-axis tool path switching fairing and numerical control equipment of a five-axis machine tool.
Background
In the industries of aerospace, automobile manufacturing, ship manufacturing and the like, the machining of more complex mechanical parts is involved, and the application of the free-form surface is more and more extensive. The five-axis numerical control machine tool has the advantages that due to the introduction of the rotating shaft, the cutter can machine workpieces at multiple angles, the flexibility of part machining is greatly improved, and the five-axis numerical control machine tool is an effective way for realizing high-speed and high-precision machining of free-form surfaces.
Currently, linear tool paths are the most common numerical control code format for industrial applications. At the joint point of the two linear tool tracks, the tangential direction and the curvature of the tool track are suddenly changed, so that the machine tool vibrates when a workpiece is machined, and further the machining efficiency and the surface quality of the workpiece are influenced.
Smoothing is carried out to five-axis tool paths, and machine tool vibration is reduced, and two main modes are provided: fitting fairing and transfer fairing. The fitting fairing is that a spline curve is adopted to approximate the original tool path track within the allowable deviation range, and the method has large calculated amount due to the limitation of curve fitting precision, so that the difficulty exists in the real-time calculation of the five-axis machine tool at present. The switching fairing is to add transition curves in two tool tracks, so that the two tracks have uniform speed change during switching, and the workpiece surface processing quality and the workpiece processing efficiency are improved.
In the existing five-axis tool path switching fairing, in engineering practice, an arc track is a conventional track description mode and has wide application, but a transition strategy for supporting the arc track in five axes does not exist.
Therefore, how to provide a transition method for switching among five-axis tool paths and a medium and a numerical control device of a five-axis machine tool, so as to construct a second-order continuous transition track between continuous five-axis track sections, so as to solve the defects in the prior art, is a technical problem to be solved by those skilled in the art.
Disclosure of Invention
In view of the above-mentioned shortcomings of the prior art, the present invention aims to provide a transition method and medium for a five-axis tool path switching fairing, and a numerical control device of a five-axis machine tool, which are used for transition between five-axis track sections, and improve the surface quality and the machining efficiency of a workpiece.
In order to achieve the above and other related objects, an aspect of the present invention provides a transition method for a five-axis tool path switching fairing, where the transition method for the five-axis tool path switching fairing includes: acquiring instruction information from a processing file of a workpiece, and analyzing the instruction information to acquire a five-axis track of the workpiece during processing; at least two sections of the five-axis trajectories are subjected to trajectory preprocessing; constructing a transfer transition curve between two adjacent preprocessed tracks; and optimizing the machining track of the cutter according to the speed constraint and the interpolation point of the switching transition curve.
In an embodiment of the present invention, the command information includes coordinate information and a speed command; the step of analyzing the instruction information comprises the following steps: and calculating the coordinate information in the processing file, and analyzing the speed instruction in the processing file.
In an embodiment of the present invention, the step of calculating the coordinate information in the processing file includes: and calculating the information of the position of the tool nose point at the starting point in the five-axis track and the information of the euler angle according to the coordinate information, and calculating the information of the position of the tool nose point at the end point in the five-axis track and the information of the euler angle.
In an embodiment of the present invention, the step of analyzing the speed command in the processing file includes: and determining the feeding speed of the tool point according to the speed instruction.
In an embodiment of the present invention, the five-axis trajectory includes a straight trajectory and a circular arc trajectory; the track preprocessing step of at least two sections of the five-axis tracks comprises the following steps: performing track preprocessing on a straight track in the five-axis track according to the coordinate information to determine the track length, the track starting point unit tangent vector and the track end point unit tangent vector of the straight track; and/or performing track preprocessing on the arc track in the five-axis track according to the coordinate information to determine the circle center, the direction vector, the arc length, the arc track radius, the central angle corresponding to the arc, the track length, the track starting point unit tangent vector and the track terminal point unit tangent vector of the arc track.
In an embodiment of the present invention, the step of constructing a transition curve between two adjacent preprocessed tracks includes: calculating a vector angle between a tail end unit tangent of the first section of track and a head end unit tangent of the second section of track; calculating a trajectory construction parameter according to the vector angle; respectively determining the parameters of the first section of track and the parameters of the second section of track by using the track construction parameters; and constructing a cubic B-spline curve according to the parameters of the first section of track and the parameters of the second section of track.
In an embodiment of the present invention, the step of optimizing the tool machining trajectory according to the speed constraint and the interpolation point of the transition curve includes: determining a first tangent vector mode length value of the switching transition curve at the beginning of the transition section; calculating the speed constraint of the switching transition curve according to a connecting point of the switching transition curve, a tail end unit tangent vector of the first section of track, a head end unit tangent vector of the second section of track, the track construction parameters and the first-order tangent vector modular length value; and calculating the interpolation point of the switching transition curve according to the interpolation speed, the interpolation period, the residual error of the first section of track and the first-order tangent vector model length value.
In an embodiment of the present invention, the step of calculating the speed constraint of the transition curve includes: calculating a constraint value of the acceleration of the switching transition curve to the speed according to a connecting point of the switching transition curve, a tail end unit tangent vector of the first section of track, a head end unit tangent vector of the second section of track, the track construction parameters and the first order tangent vector model length value; calculating a constraint value of the jerk of the transit transition curve to the speed according to a connection point of the transit transition curve, a unit tangent vector at the tail end of the first section of track, a unit tangent vector at the head end of the second section of track, the track construction parameters and the first-order tangent vector model length value; and selecting the minimum value of the speed allowed by the machining program, the allowed speed preset by the machine tool, the constraint value of the acceleration to the speed and the constraint value of the jerk to the speed as the speed constraint of the switching transition curve.
Another aspect of the present invention provides a medium having a computer program stored thereon, where the computer program is executed by a processor to implement the five-axis tool path switching fairing transition method.
In a final aspect, the present invention provides a numerical control apparatus for a five-axis machine tool, including: a processor and a memory; the memory is used for storing computer programs, and the processor is used for executing the computer programs stored by the memory so as to enable the numerical control equipment of the five-axis machine tool to execute the transition method of the five-axis tool path switching smoothness.
As described above, the transition method and medium for switching among the five-axis tool paths and the numerical control equipment of the five-axis machine tool provided by the invention have the following beneficial effects:
the invention provides a transition method for switching fairing, which realizes controllable trajectory deviation and is within a preset deviation range; the speed, the acceleration and the jerk can be controlled during the transfer transition and are within the preset parameter limit. In the transfer transition process, the speed and the acceleration are continuous, and the vibration of the machine tool can be effectively reduced. The invention supports the switching fairing transition strategy of the circular arc, and can directly establish a transition track based on track information of the circular arc of a five-axis track. The nonlinear conversion relation between the machine tool coordinate system and the workpiece coordinate system is considered, the established transition track can be quickly positioned at the position with the maximum curvature at both the workpiece coordinate system end and the machine tool coordinate system end, and the speed limit of the transition track section can be quickly determined.
Drawings
Fig. 1 is a schematic flow chart illustrating a transition method of a five-axis tool path switching fairing of the present invention in an embodiment.
Fig. 2 is a schematic diagram illustrating B-spline RTCP processing in an embodiment of the five-axis tool path switching fairing transition method of the present invention.
Fig. 3A is a transition model diagram of a straight line-straight line trajectory in an embodiment of the five-axis tool path switching fairing transition method of the present invention.
Fig. 3B is a transition model diagram of a straight line-circular arc trajectory in an embodiment of the five-axis tool path switching fairing transition method of the present invention.
Fig. 3C is a transition model diagram of a circular arc-linear trajectory in an embodiment of the five-axis tool path switching fairing transition method of the present invention.
Fig. 3D is a transition model diagram illustrating a circular arc-circular arc trajectory in an embodiment of the five-axis tool path switching fairing transition method according to the present invention.
Fig. 4 is a speed diagram of a five-axis tool path transition smoothing method according to an embodiment of the present invention.
Fig. 5 is an acceleration diagram of a five-axis tool path switching fairing transition method according to an embodiment of the present invention.
Fig. 6 is a schematic view illustrating the jerk of the five-axis tool path switching smoothing method according to an embodiment of the present invention.
Fig. 7 is a schematic diagram illustrating a transition locus of a five-axis tool path transition fairing transition method in an embodiment of the invention.
FIG. 8 is a schematic structural connection diagram of a numerical control apparatus of a five-axis machine tool according to an embodiment of the present invention.
Description of the element reference numerals
Numerical control equipment of 8 five-axis machine tool
81 processor
82 memory
S11-S14
Detailed Description
The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention. It is to be noted that the features in the following embodiments and examples may be combined with each other without conflict.
It should be noted that the drawings provided in the following embodiments are only for illustrating the basic idea of the present invention, and the drawings only show the components related to the present invention rather than the number, shape and size of the components in actual implementation, and the type, quantity and proportion of the components in actual implementation may be changed freely, and the layout of the components may be more complicated.
The transition method of the five-axis tool path switching fairing can perform switching fairing transition on an arc track, and can ensure the speed/acceleration within the allowable range of a machine tool system while ensuring the precision.
The principle and implementation of the transition method, medium and numerical control equipment of the five-axis machine tool for five-axis tool path switching fairing according to the present embodiment will be described in detail below with reference to fig. 1 to 8, so that those skilled in the art can understand the transition method, medium and numerical control equipment of the five-axis machine tool for five-axis tool path switching fairing without creative work.
Fig. 1 is a schematic flow chart illustrating a five-axis tool path transition smoothing method according to an embodiment of the present invention. As shown in fig. 1, the transition method for five-axis tool path switching fairing specifically includes the following steps:
and S11, acquiring instruction information from the processing file of the workpiece, and analyzing the instruction information to acquire the five-axis track of the workpiece during processing. For example, the machining file is a CAM (Computer Aided Manufacturing) file.
In this embodiment, the instruction information includes coordinate information and a speed instruction. And calculating the coordinate information in the processing file, and analyzing the speed instruction in the processing file.
On one hand, the information of the position of the tool nose point at the starting point in the five-axis track and the information of the Euler angle are calculated according to the coordinate information, and the information of the position of the tool nose point at the end point in the five-axis track and the information of the Euler angle are calculated.
In another aspect, a tip point feed speed is determined based on the speed command.
And S12, performing track preprocessing on at least two sections of the five-axis tracks.
In the present embodiment, the five-axis trajectory includes a straight trajectory and a circular arc trajectory. In particular to a trajectory that the trajectory of the tool nose point is a straight line and a trajectory that the trajectory of the tool nose point is an arc.
On one hand, track preprocessing is carried out on a straight track in the five-axis track according to the coordinate information so as to determine the track length, the track starting point unit tangent and the track end point unit tangent of the straight track.
Specifically, the linear trajectory is preprocessed. The ith track length path (i).
And on the other hand, performing track preprocessing on the arc track in the five-axis track according to the coordinate information to determine the circle center, the direction vector, the arc length, the arc track radius, the central angle corresponding to the arc, the track length, the track starting point unit tangent vector and the track terminal point unit tangent vector of the arc track.
Specifically, the circular arc trajectory is preprocessed. Recording the circle center of the circular arc as path (i), pc, the direction vector of the circular arc as path (i), tc, the length of the circular arc of the cutting point track as path (i), ArcLen, the radius of the circular arc track as path (i), arcRadius, the central angle path (i), arcanger, the length of the track as path (i), length of the track as path starting point unit tangent path (i), ts, and the end point unit tangent vector of the track as path (i), te.
The tool nose point track is a circle center path (i), pc, a direction vector path (i), tc, a radius path (i), arcRadius of the arc track, and the central angle path (i), ArcAngle calculation method corresponding to the arc is an arc length calculation method in the prior art, and the invention is not repeated.
(1) In the arc track preprocessing, the calculation process of the five-dimensional track length (i) of the arc track with the nose point track is as follows:
path(i).Length＝sqrt(path(i).ArcLen^2+(path(i).psa-path(i).pea)^2+(path(i).psc-path(i).pec)^2)。
in the above-mentioned formula, the compound of formula,
ArcLen represents the arc length of the middle tool point track of the ith track section;
path (i) psa represents the a-axis coordinates at the start of the ith track point;
path (i) pea represents the coordinate of the A axis at the end point of the ith track point;
path (i) psc represents the C-axis coordinate at the start of the ith track point;
path (i) pec represents the C-axis coordinate at the end point of the ith segment of track.
(2) In the circular arc track preprocessing, the unit tangent vector calculation process in which the nose point track is the starting point/the end point of the circular arc track is as follows (taking the starting point path (i) ts as an example, the end point is the same as the following):
let tarc be an intermediate amount for calculation, tarc ═ path (i), tc ^ (path (i), ps (1:3) -path (i), pc), ^ denotes cross product, and tarc ═ tarc/| tarc |.
Substituting calculated tarc into temp _ t ═ tarc, (path (i). pe (4:5) -path (i). ps (4:5))/path (i). ArcLen ], and then making the arc track starting point unit tangent path (i) · ts ═ temp _ t/| temp _ t |.
In the above-mentioned formula, the compound of formula,
path (i). ps (1:3) is the X-axis, Y-axis and Z-axis coordinates of the starting point of the ith segment;
path (i). ps (4:5) is the A-axis and C-axis coordinates of the start of the ith segment;
path (i) pe (4:5) is the A-axis and C-axis coordinates of the end point of the i-th segment.
And S13, constructing a transfer transition curve between two adjacent preprocessed tracks.
In the present embodiment, S13 includes:
(1) and calculating a vector angle between the tail end unit tangent of the first section of track and the head end unit tangent of the second section of track.
Specifically, two continuous tracks are defined as path (i) and path (i +1), and the ligation point of path (i) and path (i +1) is p 1; the unit tangent vector at the end of path (i) is defined as t1, and the unit tangent vector at the head end of path (i +1) is defined as t2, i.e.: t1, t2, path (i +1) ts. The vector angle Teata of-t 1 and t2 is calculated by the formula Teata ═ arcos (dot (-t1, t 2)). Where dot (-t1, t2) represents the dot product of vectors-t 1 and t 2.
(2) And calculating track construction parameters according to the vector angle.
Calculating a transition track construction parameter d according to a vector angle Teata, a chord height error ChordError allowed by a numerical control system, a track Length1 of a path (i), a track Length2 of a path (i +1) and a track form (whether a track of a nose point is a circular arc or not), wherein the construction mode is as follows: d is min ([ chord error _ d, Length _ d, arc _ d ].
Wherein, chord error _ d is the constraint of the curve chord height error to the construction parameter d, Length _ d is the constraint of the track Length to the construction parameter d, and arc _ d is the constraint of the track form to the construction parameter d. Chord error _ d ═ 3 × chord error/cos (Teata/2); length _ d ═ Length _ k ═ min ([ Length1, Length2 ]); len _ k is an empirical coefficient, and the value range is len _ k belonging to [ 0.010.5 ].
and arc _ d means that if the track of the tool point exists in the front and rear tracks and is an arc, the arc restricts d. For example, arc _ d of the ith segment is calculated as follows: arc _ d ═ path (i), arcRadius path (i), Length/path (i), ArcLen.
Wherein, path (i) arcRadius represents the radius of the arc track corresponding to the ith segment; path (i), Length represents the five-dimensional track Length of the arc track corresponding to the ith segment; ArcLen represents the three-dimensional arc length of the arc track corresponding to the ith segment; k represents an empirical coefficient and has a value range of k belonging to [ 0.010.2 ].
It should be noted that if the front and rear tracks are arcs, the corresponding arc _ d needs to be calculated for the arcs of the front and rear tracks, and the smaller value is taken as the arc _ d; if there is no circular arc trajectory, there is no such limitation.
(3) And respectively determining the parameters of the first section of track and the parameters of the second section of track by using the track construction parameters. Specifically, the first-stage trajectory is taken as a front-stage trajectory, and the second-stage trajectory is taken as a rear-stage trajectory. The parameters of the first segment of track are paa, taa, and the parameters of the second segment of track are pbb, tbb.
Please refer to fig. 3A to fig. 3D, which respectively show a transition model diagram of a straight line-straight line trajectory in an embodiment of the five-axis tool path switching fairing transition method of the present invention, a transition model diagram of a straight line-circular arc trajectory in an embodiment of the five-axis tool path switching fairing transition method of the present invention, a transition model diagram of a circular arc-straight line trajectory in an embodiment of the five-axis tool path switching fairing transition method of the present invention, and a transition model diagram of a circular arc-circular arc trajectory in an embodiment of the five-axis tool path switching fairing transition method of the present invention. The front section of the track of fig. 3A is a straight track, and the rear section of the track is a straight track; the front section of the track in fig. 3B is a straight track, and the rear section of the track is a circular arc track; the front section of the track in fig. 3C is a circular arc track, and the rear section of the track is a straight line track; the front section trajectory of fig. 3D is a circular arc trajectory, and the rear section trajectory is a circular arc trajectory.
A. The start position paa of the transition curve is constructed and the tangential direction taa of point paa on the lead segment trajectory is determined.
A1. If the front segment trajectory is a straight line, paa is defined as: paa ═ p1-d × t 1; taa is defined as: taa is t 1.
A2. If the front segment trajectory is a circular arc, paa is defined as: dTeata ═ karc × path (i) · arcangele wherein karc ═ 1-d/path (i) · Length. paa is the point of the section i where the trajectory of the point of the nose is at dTata from the central angle of the joining point p 1; taa is a unit tangent vector of paa on the circular arc, and the calculation method thereof is consistent with the calculation method of the unit tangent vector at the start point of the trajectory in which the tip point is the circular arc trajectory in step (2) of S12.
B. The end position pbb of the transition curve is constructed and the tangential direction tbb of the point pbb on the trailing trace is determined.
B1. If the rear section track is a straight line, pbb is determined according to the following method: pbb ═ p1+ d × t 2; tbb are defined as follows: tbb ═ t 2.
B2. If the rear section track is a circular arc: let dTeataR ═ k × path (i +1). arcangele, where k ═ d/path (i +1). Length; pbb is the point of the section i +1 where the trajectory of the point of the tool nose is away from the central angle dTata of the joining point p 1; tbb denotes a unit tangent vector on the circular arc of pbb, and the calculation method thereof coincides with the calculation method of the unit tangent vector at the start point of the trajectory in which the nose point is the circular arc trajectory in step (2) of S12.
(4) And constructing a cubic B-spline curve according to the parameters of the first section of track and the parameters of the second section of track.
Specifically, when constructing a cubic B-spline curve, the control point BP is defined as follows: BP ═ q 0; q 1; q 2; q 3; q 4; q 5; q6 ]; corresponding 3-degree B spline node parameters: BKnot ═ 0; 0; 0; 0; 0.5; 0.5; 0.5; 1; 1; 1; 1].
B spline curve passing formula
Figure BDA0002690249200000071
And (5) constructing. Wherein N isi,3And (u) is a B-sample strip base for 3 times, u represents the numerical value of the node parameter, the value is taken in Bknot, the calculation of the sample strip curve is a known technology in the prior art, and the invention is not described again.
Control point BP ═ q 0; q 1; q 2; q 3; q 4; q 5; q6] is determined as follows to ensure second order continuity at the start/end of the transition curve:
q0＝paa；
q6＝pbb；
q1＝paa+1/3*d*taa；
q2＝paa+2/3*d*taa；
q5＝pbb-1/3*d*tbb；
q4＝pbb-2/3*d*tbb；
q3＝0.5*(q2+q4)；
the second order tangent formula at the origin is:
bspl(2)(0)＝p*(p-1)/BKnot(p+1)*[q0/BKnot(p+1)-q1*(BKnot(p+1)+BKnot(p+2))/BKnot(p+1)/BKnot(p+2)+q2/BKnot(p+2)]。
let p be 3, and substitute the parameters for constructing the transition curve to obtain bspl(2)(0) For example, the second order tangent formula at the end point can be derived as 0: bspl(2)(1) This ensures a second order continuation of the curve from the beginning to the end, which is 0.
And S14, optimizing the tool machining track according to the speed constraint and the interpolation point of the switching transition curve.
In five-axis planning, the rated speed, acceleration constraint and the like of a motor of each axis need to be ensured, and meanwhile, the machining precision of a workpiece needs to be ensured. The invention realizes that the precision is ensured and the speed/acceleration/jerk is in the range allowed by the System by calculating the speed limit in the MCS (Machine Coordinate System) and interpolating in the WCS (Workpiece Coordinate System).
In the present embodiment, S14 includes:
(1) and determining a first tangent vector mode length value of the switching transition curve at the beginning of the transition section.
The first tangent-vector mode-length value at the beginning of the transition is denoted as alpha, and alpha is 2 x d.
(2) And calculating the speed constraint of the switching transition curve according to the connection point of the switching transition curve, the tail end unit tangent vector of the first section of track, the head end unit tangent vector of the second section of track, the track construction parameters and the first-order tangent vector modular length value.
The curve speed constraint calculation involves p1a, p1b and p1, which are determined by the unit tangent t1 at the end of path (i), the unit tangent t2 at the head of path (i +1) and the parameter d, as follows: p1a ═ p1-t1 × d; p1b ═ p1+ t2 × d.
Specifically, the calculating the speed constraint of the transfer transition curve in the step (2) includes:
and (2.1) calculating a constraint value of the acceleration of the switching transition curve to the speed according to a connecting point of the switching transition curve, a tail unit tangent vector of the first section of track, a head unit tangent vector of the second section of track, the track construction parameters and the first order tangent vector modular length value.
Please refer to fig. 2, which illustrates a schematic diagram of B-spline RTCP processing in an embodiment of the five-axis tool path switching fairing transition method according to the present invention. The five-axis structure parameters of the Machine Tool determine the conversion relationship from the programming instruction information in the WCS (Workpiece Coordinate System) to the position information in the MCS (Machine Coordinate System), i.e. the RTCP (Rotational Tool Center Point) conversion relationship. As shown in fig. 2, data points of p1, p1a, and p1b in WCS (Workpiece Coordinate System) corresponding to MCS (Machine Coordinate System) are p1_ MCS, p1a _ MCS, and p1b _ MCS, respectively. In order to ensure the surface quality of the Workpiece, it is ensured that the track constructed at the WCS (Workpiece Coordinate System) end is generally symmetrical, so that the transition track at the MCS (Machine Coordinate System) end is asymmetrical.
In the velocity constraint calculation, the velocity constraint value of the asymmetrically constructed B-spline track needs to be determined. In the curve interpolation stage, the relationship between jerk, acceleration and curve characteristics needs to be considered. And recording the second-order mode length maximum value BataMax and the third-order mode length maximum value GamaMax of the 3-order B-spline transition curve section. At the MCS end, the module length | p1a _ mcsp1_ MCS | ≠ module length | p1b _ mcsp1_ MCS |.
When the node parameter u is 0.5, the modular length value of the second order tangent vector is the maximum value of u on [0, 1], so that: batama ═ 4 × p1a _ mcs + p1b _ mcs-2 × p1_ mcs |.
The constraint vacc of the acceleration to the speed is determined according to the formula vacc alpha (aM/BataMax) ^ (1/2), wherein aM is the maximum acceleration preset by the system.
And (2.2) calculating a constraint value of the jerk of the switching transition curve to the speed according to a connecting point of the switching transition curve, a unit tangent vector at the tail end of the first section of track, a unit tangent vector at the head end of the second section of track, the track construction parameters and the first-order tangent vector modular length value.
The constructed 3-th order B-spline third-order modular length value is fixed. Therefore, when u is equal to 0, the modular length value of the third-order tangent vector is the maximum value in the value range [0, 1] of u, that is: GamaMax ═ 8 × p1a _ mcs + p1b _ mcs-2 × p1_ mcs |.
The constraint vjerk of jerk to speed is determined according to the formula vjerk alpha (jM/GamaMax) ^ (1/3), wherein jM is the maximum jerk preset by the system.
And (2.3) selecting the minimum value of the speed allowed by the machining program, the allowed speed preset by the machine tool, the constraint value of the acceleration to the speed and the constraint value of the jerk to the speed as the speed constraint of the transfer transition curve.
Let the speed v allowed at the transition be min ([ vacc, vjerk, F, vM ]), where F is the speed allowed by the program and vM is the speed allowed by the system.
Fig. 4 to fig. 6 respectively show a velocity diagram of a five-axis tool path switching fairing transition method of the present invention in an embodiment, an acceleration diagram of the five-axis tool path switching fairing transition method of the present invention in an embodiment, and an acceleration diagram of the five-axis tool path switching fairing transition method of the present invention in an embodiment. The graphs of the resultant five axes and the corresponding variables of the individual X, Y, Z, a and C axes are shown.
(3) And calculating the interpolation point of the switching transition curve according to the interpolation speed, the interpolation period, the residual error of the first section of track and the first-order tangent vector model length value.
Specifically, the equal-parameter interpolation is performed on the transition section. Let the residual of the previous segment be rms, the current interpolation speed be vs, and the first-order tangent vector modulo length value at the beginning of the transition segment be denoted as alpha, alpha being 2 x d.
The interpolated parameter step is calculated as follows:
let duration time be alpha/vs; and substituting the calculated duration time into a formula du/duration time to obtain du. The starting node parameter u is defined as us, and us is rms/alpha, and the node parameter range is determined as [ us,1 ].
Fig. 7 is a schematic diagram showing a transition locus of a five-axis tool path transition fairing transition method according to an embodiment of the present invention. As shown in fig. 7, each u value corresponds to an interpolation point on the B-spline curve, and equal-parameter interpolation with interval du is performed in a parameter interval u e [ us,1], where T is an interpolation period. For example, us corresponds to a first interpolation point, us + du corresponds to a second interpolation point, us + du + du corresponds to a third interpolation point, and so on, a plurality of interpolation points form a B-spline curve, i.e., a transition curve, and the last effective interpolation parameter interpolated in [ us,1] is denoted as uend.
Thus, the residual rme and velocity after the transition interpolation are as follows: rme ═ alpha × overu (where overu ═ uend + du-1); ve ═ vs.
The calculation in the transition method of the five-axis tool path switching fairing is vector calculation. The protection scope of the five-axis tool path switching fairing transition method is not limited to the execution sequence of the steps listed in the embodiment, and all the schemes of adding, subtracting and replacing the steps in the prior art according to the principle of the invention are included in the protection scope of the invention.
The present embodiment provides a computer storage medium on which a computer program is stored, wherein the computer program is executed by a processor to implement the transition method of five-axis tool path switching fairing.
Those of ordinary skill in the art will understand that: all or part of the steps for implementing the above method embodiments may be performed by hardware associated with a computer program. The aforementioned computer program may be stored in a computer readable storage medium. When executed, the program performs steps comprising the method embodiments described above; and the aforementioned computer-readable storage media comprise: various computer storage media that can store program codes, such as ROM, RAM, magnetic or optical disks.
Please refer to fig. 8, which is a schematic structural connection diagram of a numerical control apparatus of a five-axis machine tool according to an embodiment of the present invention. As shown in fig. 8, the present embodiment provides a numerical control apparatus 8 of a five-axis machine tool, the numerical control apparatus 8 of the five-axis machine tool including: a processor 81 and a memory 82; the memory 82 is used for storing a computer program, and the processor 81 is used for executing the computer program stored in the memory, so that the numerical control equipment of the five-axis machine tool executes each step of the transition method of the five-axis tool path switching smoothness.
The Memory 82 may include a Random Access Memory (RAM), and may further include a non-volatile Memory (non-volatile Memory), such as at least one disk Memory.
The Processor 81 may be a general-purpose Processor, and includes a Central Processing Unit (CPU), a Network Processor (NP), and the like; the Integrated Circuit may also be a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) or other Programmable logic device, discrete gate or transistor logic device, discrete hardware component.
In summary, the transition method and medium for switching among the five-axis tool paths and the numerical control equipment of the five-axis machine tool provide a transition method for switching among the five-axis tool paths, so that the track deviation is controllable and is within a preset deviation range; the speed, the acceleration and the jerk can be controlled during the transfer transition and are within the preset parameter limit. In the transfer transition process, the speed and the acceleration are continuous, and the vibration of the machine tool can be effectively reduced. The invention supports the switching fairing transition strategy of the circular arc, and can directly establish a transition track based on track information of the circular arc of a five-axis track. The nonlinear conversion relation between the machine tool coordinate system and the workpiece coordinate system is considered, the established transition track can be quickly positioned at the position with the maximum curvature at both the workpiece coordinate system end and the machine tool coordinate system end, and the speed limit of the transition track section can be quickly determined. The invention effectively overcomes various defects in the prior art and has high industrial utilization value.
The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.

Claims (10)

1. A transition method of a five-axis tool path switching fairing is characterized by comprising the following steps:
acquiring instruction information from a processing file of a workpiece, and analyzing the instruction information to acquire a five-axis track of the workpiece during processing;
at least two sections of the five-axis trajectories are subjected to trajectory preprocessing;
constructing a transfer transition curve between two adjacent preprocessed tracks;
and optimizing the machining track of the cutter according to the speed constraint and the interpolation point of the switching transition curve.
2. The five-axis tool path switching fairing transition method as recited in claim 1, wherein said command information comprises coordinate information and a speed command; the step of analyzing the instruction information comprises the following steps:
and calculating the coordinate information in the processing file, and analyzing the speed instruction in the processing file.
3. The five-axis tool path switching fairing transition method as claimed in claim 2, wherein the step of calculating coordinate information in the machining file comprises:
and calculating the information of the position of the tool nose point at the starting point in the five-axis track and the information of the euler angle according to the coordinate information, and calculating the information of the position of the tool nose point at the end point in the five-axis track and the information of the euler angle.
4. The five-axis tool path switching fairing transition method as claimed in claim 2, wherein the step of parsing the speed command in the machining file comprises:
and determining the feeding speed of the tool point according to the speed instruction.
5. The five-axis tool path switching fairing transition method of claim 2, wherein said five-axis trajectory comprises a straight trajectory and a circular arc trajectory; the track preprocessing step of at least two sections of the five-axis tracks comprises the following steps:
performing track preprocessing on a straight track in the five-axis track according to the coordinate information to determine the track length, the track starting point unit tangent vector and the track end point unit tangent vector of the straight track; and/or
And carrying out track preprocessing on the arc track in the five-axis track according to the coordinate information so as to determine the circle center, the direction vector, the arc length, the arc track radius, the central angle corresponding to the arc, the track length, the track starting point unit tangent vector and the track terminal point unit tangent vector of the arc track.
6. The five-axis tool path transition fairing transition method of claim 1, wherein the step of constructing a transition curve between two adjacent preprocessed trajectories comprises:
calculating a vector angle between a tail end unit tangent of the first section of track and a head end unit tangent of the second section of track;
calculating a trajectory construction parameter according to the vector angle;
respectively determining the parameters of the first section of track and the parameters of the second section of track by using the track construction parameters;
and constructing a cubic B-spline curve according to the parameters of the first section of track and the parameters of the second section of track.
7. The five-axis tool path transition fairing transition method of claim 6, wherein said step of optimizing a tool machining trajectory based on a speed constraint and interpolation points of said transition profile comprises:
determining a first tangent vector mode length value of the switching transition curve at the beginning of the transition section;
calculating the speed constraint of the switching transition curve according to a connecting point of the switching transition curve, a tail end unit tangent vector of the first section of track, a head end unit tangent vector of the second section of track, the track construction parameters and the first-order tangent vector modular length value;
and calculating the interpolation point of the switching transition curve according to the interpolation speed, the interpolation period, the residual error of the first section of track and the first-order tangent vector model length value.
8. The five-axis tool path transition fairing transition method of claim 7, wherein said step of calculating a speed constraint for said transition profile comprises:
calculating a constraint value of the acceleration of the switching transition curve to the speed according to a connecting point of the switching transition curve, a tail end unit tangent vector of the first section of track, a head end unit tangent vector of the second section of track, the track construction parameters and the first order tangent vector model length value;
calculating a constraint value of the jerk of the transit transition curve to the speed according to a connection point of the transit transition curve, a unit tangent vector at the tail end of the first section of track, a unit tangent vector at the head end of the second section of track, the track construction parameters and the first-order tangent vector model length value;
and selecting the minimum value of the speed allowed by the machining program, the allowed speed preset by the machine tool, the constraint value of the acceleration to the speed and the constraint value of the jerk to the speed as the speed constraint of the switching transition curve.
9. A medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the five-axis tool change smoothing transition method of any one of claims 1 to 8.
10. A numerical control apparatus of a five-axis machine tool, characterized by comprising: a processor and a memory;
the memory is used for storing a computer program, and the processor is used for executing the computer program stored by the memory to enable the numerical control equipment of the five-axis machine tool to execute the transition method of the five-axis tool path switching smoothness as claimed in any one of claims 1 to 8.
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