CN109732401A

CN109732401A - A method for detecting the position-independent error of double rotary axes of five-axis CNC machine tools

Info

Publication number: CN109732401A
Application number: CN201910010087.3A
Authority: CN
Inventors: 蒋晓耕; 贾经纬; 王量; 姚思涵; 王浩; 李晨阳
Original assignee: Tianjin Polytechnic University
Current assignee: Tianjin Polytechnic University
Priority date: 2019-01-02
Filing date: 2019-01-02
Publication date: 2019-05-10
Anticipated expiration: 2039-01-02
Also published as: CN109732401B

Abstract

The invention discloses a method for detecting the position-independent error of double rotary axes of a five-axis numerically controlled machine tool. Independent Geometric Errors (PIGEs), a new measurement trajectory is proposed to solve the asynchrony between the resultant velocity and the ballbar capture velocity when the B-axis of the swing axis and the C-axis of the rotation axis move in coordination, combined with the rigid body kinematics. Homogeneous transformation matrix, establishing a simulation model, and combining the simulation model with the experiment to realize the identification and measurement of the position-independent geometric errors of the double rotary axes of the five-axis numerical control machine tool. The geometric error of the rotating shaft has nothing to do with the position, the precision is high, and the practicability is good.

Description

A kind of detection method about the unrelated error of five-axle number control machine tool double back rotating shaft position

Technical field

The invention belongs to numerically-controlled machine tool detection technique fields, in particular to one kind is about five-axle number control machine tool dual AC power axle position Set the detection method of unrelated error.

Technical background

Five-axle number control machine tool is widely used in the part of processing complex geometry feature, it, which has, improves surface smoothness, improves The advantages that material remove rate.And under most processing conditions be all the double back shaft by lathe, make cutter relative to workpiece into Change in orientation occurs when row processing, therefore there is greater flexibility than traditional three axis machining when generating cutter path.But It is that swinging axle B axle and rotary shaft C axis introduce more geometric error elements in processing, part to be processed is caused flaw occur And defect.

The constant error for studying swinging axle B axle and rotary shaft C axis is most important for control five-axle number control machine tool precision, mesh Before there are ball bar, the measuring devices such as laser interferometer and R-test.Due to the features such as ball bar operation is convenient, and time-consuming is few It is widely adopted.But how to solve aggregate velocity when swinging axle B axle and the rotary shaft C axis coordinated movement of various economic factors and ball bar capture speed Asynchronism between degree accurately identifies the double back shaft geometric error unrelated with position using ball bar, therefore proposes that one kind can It is particularly important in the method for quickly and simply detecting the unrelated error of five-axle number control machine tool double back rotating shaft position.

Summary of the invention

To solve the above problems, it is an object of the invention to propose it is a kind of about five-axle number control machine tool double back rotating shaft position without The detection method for closing error, is examined using the geometric error unrelated with position of the ball bar to swinging axle B axle and rotary shaft C axis It surveys.The invention can be easy and be accurately measured to error, and then greatlys improve processing quality.Specific measuring process is such as Under:

Step 1, according to the specific structure and swinging axle B axle of five-axle number control machine tool and the position of rotary shaft C axis, build reality Test measuring device.

Step 2, Binding experiment device propose 8 Xiang Yuwei of measurement five-axle number control machine tool swinging axle B axle and rotary shaft C axis Set the track of unrelated geometric error.

Step 3, solve swinging axle B axle and aggregate velocity when the rotary shaft C axis coordinated movement of various economic factors and ball bar acquisition speed it Between asynchronism

Step 4 carries out error identification in conjunction with lathe multi-body movement Systems Theory and homogeneous coordinate transformation.

According to five shafts numerical controlled machine bed structure and swinging axle B axle and rotary shaft C axis type in step 1, the survey of ball bar is determined Measure position.Two balls of ball bar are magnetically attracted on two tool cups, the two tool cups are connected to main shaft and are located at workbench Fixture on, comprising steps of

The coordinate system that step 1.1, setting measure, Z axis are overlapped with the original Z axis of lathe, measure the X-axis and Y-axis of coordinate system It is parallel to the direction of motion of lathe X-axis and Y-axis.

Step 1.2, rotary shaft C axis tool cup are mounted on the fixture at the top of turntable, and the XOY plane for measuring coordinate system exists It is lifted on turntable, sets the size of the distance between swinging axle B axle and origin O-XYZ as 400mm, incited somebody to action using touch probe The center of spindle tools cup to swinging axle B axle is adjusted to 400mm, while the Workpiece tool cup being located on turntable is apart from rotary shaft C axis center 400mm, ball bar are extended using extension bar, its nominal length is converted to 400mm, and to experimental tool into Row calibration.

Corresponding program is utilized in step 2, the swinging axle B axle and rotary shaft C axis for controlling five-axle number control machine tool link, Geometric error unrelated with position of double back shaft of five-axle number control machine tool is measured during this, comprising steps of

It is aligned the axis of ball bar with the Y-axis of O-XYZ in step 2.1, measuring route, one end setting of ball bar exists The origin of O-XYZ, the other end are arranged at the position 400mm apart from Y-axis.Swinging axle B axle and rotary shaft C axis are rotated from 0 ° respectively To -90 ° and 90 ° to 0 °.

The distance between two tool cups are not constant in step 2.2, main shaft and turntable, will lead to ball bar from magnetic Fall down on property centre mount, thus the coordinated movement of various economic factors of swinging axle B axle and rotary shaft C axis should ensure that the point of the P in Fig. 3 and Q point away from From being held constant at 400mm.

P point in Fig. 3 is projected to XOY plane by step 2.3, Fig. 4, to obtain the rotation of swinging axle B axle and rotary shaft C axis Relationship between angle:

According to pythagoras of Samos theorem:

In XOY plane according to cosine law:

By measuring device R_B=R_C=L_DBB=400mm, formula (1) and formula (2), the available pass rotated between angle System:

Solved in step 3 swinging axle B axle and aggregate velocity when the rotary shaft C axis coordinated movement of various economic factors and ball bar acquisition speed it Between asynchronism.

Step 3.1, swinging axle B axle and rotary shaft C axis rotate to -90 ° and 90 ° from 0 ° respectively and rotate to 0 °, swinging axle B axle It is rotated with constant speed, step-length is that the position of 0.1 ° of corresponding rotary shaft C shaft angle can provide are as follows:

And the angle position of swinging axle B axle and rotary shaft C axis is:

Step 3.2, each step-length of experiment measurement represent in Fig. 5, form semicircle track.

Step 3.3, Fig. 6 show adjacent step sizes be not it is equidistant, will lead to lathe along the fluctuation of the step-length of track The problem of movement and ball bar asynchronous sampling, since the acquisition rate of ball bar is constant, thereby, it is ensured that movement is at the uniform velocity It is also particularly significant, analysis also could be effective.

Step 3.4, track represents tool cup center in Fig. 6.Spindle tools cup is mounted on the main shaft of swinging axle B axle On shell, therefore tool cup axis and tool cup are centrally formed one and half straight circular cones as shown in fig. 7, cone therefore can be obtained The bottom radius of circle of parameter, cone isThe aperture of cone is 90 °, and the bus length of cone is 400mm.

Step 3.5, in order to ensure the distance between adjacent step sizes it is constant, cone is deployed on two-dimensional surface, such as Fig. 8 (a) shown in, if distance | | OO ' | | it is r,SchemingIt can also be obtained in expansion planeThe angle of spread can be obtained:

Step 3.6 is expressed as φ by the central angle of OB and BP ' encirclement, can provide are as follows:

Θ can be given by the central angle of OO ' and O ' P ' encirclement in step 3.7, Fig. 8 (c), in the bottom circle of cone In, it can provide:

Step 3.8, wherein N is in Fig. 8 (c) | | OP ' | | midpoint, be based on triangle relation, following equation can be provided:

Step 3.9, therefore θ_BIt can be obtained based on equation 5-9 with the relationship of Θ:

As long as step 3.10, tool cup center are evenly distributed in Φ, so that it may realize uniform motion, be selected in centre 900 steps of equidistance are selected, formula equation 5-10 is substituted into, it is as shown in Figure 9 to form equally distributed motion profile.

In step 4, error measure model is established according to theory of multi body system and homogeneous coordinate transformation, although proposed Method is to put english to carry out on turntable type five-axis machine tool in swinging axle, but can be applied to any have the five of similar topological structure Axis lathe.In order to simplify modeling process, current multi-axis NC Machine Tools NC system can compensate for linear axis error, it is therefore assumed that all The geometric error of compensation linear axes only considers the PIGE of rotary shaft before test.

Step 4.1, rotary shaft C axis PIGE according to ISO230-1, each rotary shaft has 4 PIGE, it is contemplated that the zero of CNC Position compensation function can ignore an error of zero.4 PIGE are two linear position errors in XOY plane in X-axis and Y-axis Component E_XOCAnd E_YOC, and two orientation error component E of X-axis and Y-axis are surrounded respectively_AOCAnd E_BOC.It can be based on IOS230-1 Obtain the like error composition of swinging axle B axle.

Step 4.2, the overall error that kinematic axis can be assessed by the sequence multiplication of basic homogeneous transform matrix.According to more bodies Systems Theory, the eigentransformation matrix from workpiece coordinate system to reference frame can be given below:

Cutting tool branch similar with above-mentioned expression formula can provide:

Ideal transformation matrix from center cutter point to workpiece coordinate system can be given below:

It is influenced by PIGE in contacting, the practical posture of transition matrix indicates are as follows:

Wherein E is 4 × 4 rank unit matrixs, due to there are geometric error,Indicate given deviation matrix:

Then the real transform from cutting tool central point to workpiece can provide:

Wherein letter r, W, T and i indicate the reference frame in the kinematic chain of target lathe, workpiece coordinate system, skiver Has the coordinate system of coordinate system and the i-th rigid body.D_idealAnd D_actualIt indicates ideal and actual homogeneous transform matrix, indicates from its left side Transformation of the lower target coordinate system to one of its pre-super.Rot and Trans respectively describes rotation and translation in homogeneous transform matrix From its pre-sub coordinate system to the conversion in one of its upper left corner.

The model use pseudoinverse technique proposed in step 4.3, Binding experiment measurement data and step 4 obtains five-shaft numerical control Eight errors unrelated with geometric position of lathe swinging axle and rotary shaft.

Five-axle number control machine tool double back shaft Error Analysis unrelated with position, including 8 and geometry position are completed above Set unrelated geometric error.

The identification and inspection of double back shaft geometric error unrelated with position in effective solution of the present invention five-axle number control machine tool It surveys, propose effective detection path and solves the asynchronism of ball bar in the detection process, finally obtain measurement result.

Detailed description of the invention

Fig. 1 is the structure chart of certain five-axle number control machine tool

Fig. 2 is the schematic diagram of experimental provision position in embodiment of the present invention method

Fig. 3 is by the measuring route that experiment measurement is walked in embodiment of the present invention method

Fig. 4 is the XOY plane perspective view of measuring route in embodiment of the present invention method

Fig. 5 is the semicircle track that each step-length in track is formed in embodiment of the present invention method

Fig. 6 is that measuring route step-length is uneven in embodiment of the present invention method

Fig. 7 be embodiment of the present invention method in B axle measuring route tool cupuliform at semicircle cone

Fig. 8 is that plan view is unfolded in half cone formed in embodiment of the present invention method

Fig. 9 is that measuring route step-length is uniform in embodiment of the present invention method

Specific embodiment

A specific embodiment of the invention is described below with reference to experimental measurement method and attached drawing.

Attached drawing 1 show the structure chart for certain five-axle number control machine tool that the present invention uses, based on this to this measurement method It is described.

Step 1.1, setting meet the measurement coordinate system of this experimental measurement method, by the original Z of the Z axis of coordinate system and lathe Overlapping of axles, the X-axis and Y-axis of coordinate system are parallel to the direction of motion of lathe X-axis and Y-axis.

Step 1.2, as shown in Fig. 2, the tool cup of rotary shaft C axis is mounted in the top clamp of rotary table, The XOY plane of measurement coordinate system is lifted on a spinstand, and swinging axle B axle is set as apart from the distance between origin O-XYZ The center of spindle tools cup to swinging axle B axle is adjusted to 400mm using touch probe, while is located on turntable by 400mm Workpiece tool cup is extended using extension bar apart from rotary shaft C axis center 400mm, ball bar, its nominal length is converted to 400mm, and experimental tool is calibrated.

Corresponding program is utilized in step 2, the swinging axle B axle and rotary shaft C axis for controlling five-axle number control machine tool link, Geometric error unrelated with position of five-axle number control machine tool double back shaft is measured during this, comprising steps of

Step 2.1, measuring route are as shown in Fig. 3, are aligned the bar of ball bar with the Y-axis of O-XYZ, ball bar The origin of O-XYZ is arranged in one end, and the other end is arranged at the position 400mm of distance Y.Swinging axle B axle and rotary shaft C axis difference - 90 ° and 90 ° to 0 ° are rotated to from 0 °.Ball bar carries out data acquisition simultaneously.

Step 2.2, due between two tool cups on main shaft and in turntable distance be not it is constant, will lead to club Instrument falls down from non-magnetic center seat, therefore the coordinated movement of various economic factors of swinging axle B axle and rotary shaft C axis should ensure that the point of the P in Fig. 3 and Q The distance of point is held constant at 400mm.

P point in attached drawing 3 is projected to XOY plane by step 2.3, attached drawing 4, to obtain between B axle and the rotation angle of C axis Relationship:

According to pythagoras of Samos theorem:

In XOY plane according to cosine law:

Further, it is different that the movement of swinging axle B axle and rotary shaft C axis when carrying out data acquisition is solved in step 3 Step problem.

And the angle position of swinging axle B axle and rotary shaft C axis is:

The semicircle track that each step-length of experiment measurement is formed is illustrated in step 3.2, attached drawing 5.

Step 3.3, attached drawing 6 show adjacent step sizes be not it is equidistant, will lead to machine along the fluctuation of the step-length of track The problem of bed motion and ball bar asynchronous sampling, since the acquisition rate of ball bar is constant, thereby, it is ensured that movement is even Fast is also particularly significant, and analysis also could be effective.

Step 3.7 can be given Θ by the central angle of OO ' in Fig. 8 (c) and O ' P ' encirclement, in the bottom circle of cone In, it can provide:

Step 3.8, N is in Fig. 8 (c) | | OP ' | | midpoint, be based on triangle relation, following equation can be provided:

Step 3.10, attached drawing 9 show equally distributed motion profile, as long as tool cup center is evenly distributed on Φ In, so that it may it realizes uniform motion, in 900 steps of intermediate selection equidistance, substitutes into formula equation 5-10, formation is uniformly distributed Motion profile.

Further, in step 4, error measure model is established according to theory of multi body system and homogeneous coordinate transformation, although institute The method of proposition is to carry out on " swinging axle B axle and turntable C axis " formula five-axis machine tool, but can be applied to any have The five-axis machine tool of similar topological structure.In order to simplify modeling process, current multi-axis NC Machine Tools NC system can compensate for linear axes Error, it is therefore assumed that the geometric error for compensating linear axes before all tests only considers the PIGE of rotary shaft.

The model use pseudoinverse technique proposed in step 4.3, Binding experiment measurement data and step 4 obtains five-shaft numerical control The error unrelated with geometric position of eight of lathe double back shaft is as shown in Table 1:

Claims

1. a detection method about the position-independent error of the double rotary axes of a five-axis CNC machine tool, is characterized in that, comprises the steps:

Step 1. According to the specific structure of the five-axis CNC machine tool and the positions of the B-axis of the swing axis and the C-axis of the rotation axis, an experimental measurement device is built.

Step 2. Combined with the experimental device, a trajectory for measuring 8 position-independent geometric errors of the swing axis B axis and the rotation axis C axis of the five-axis CNC machine tool is proposed.

Step 3. Solve the asynchrony between the synthetic speed and the ballbar capture speed when the swing axis B axis and the rotation axis C axis coordinate motion

Step 4. Carry out error identification based on the theory of machine tool multi-body motion system and homogeneous coordinate transformation.

2. The method for detecting the position-independent error of the dual rotary axes of a five-axis CNC machine tool according to claim 1, wherein in step 1, according to the structure of the five-axis CNC machine tool and the swing axis B axis and the rotation axis C axis type, set up the experimental setup, such as the position of the ballbar and the calibration of the tool cup, including steps:

Step 1.1. Set the coordinate system for measurement, the Z-axis coincides with the original Z-axis of the machine tool, and the X-axis and Y-axis of the measurement coordinate system are parallel to the movement directions of the X-axis and Y-axis of the machine tool.

Step 1.2. The rotary axis C-axis tool cup is installed on the fixture on the top of the rotary table, the XOY plane of the measurement coordinate system is lifted on the rotary table, and the distance O-XYZ between the B-axis of the swing axis and the origin is set as 400mm, use the touch probe to adjust the center of the spindle tool cup to the B-axis of the swing axis to 400mm, and the workpiece tool cup located on the rotary table is 400mm away from the center of the C-axis of the rotary axis. The length was converted to 400mm and the experimental tool was calibrated.

3. The detection method about the position-independent error of the double rotary axes of the five-axis CNC machine tool according to claim 1, is characterized in that, in the step 2, in conjunction with the experimental device, it is proposed to measure the five-axis CNC machine tool swing axis B-axis and The trajectory of the 8-item position-independent geometric errors of the C-axis of the rotary axis, including the steps:

Step 2.1. In the measurement path, first align the axis of the ballbar with the Y axis of the O-XYZ. One end of the ballbar is set at the origin of the O-XYZ, and the other end is set at a distance of 400mm from the Y axis. The swing axis B axis and the rotation axis C axis rotate from 0° to -90° and 90° to 0°, respectively.

Step 2.2. The distance between the two tool cups in the spindle and the rotary table is not constant, which will cause the ballbar to fall off the magnetic center seat, so the coordinated movement of the swing axis B axis and the rotation axis C axis should ensure that the ballbar The distance between the two bases was kept constant at 400mm.

Step 2.3. Project the measurement trajectory to the XOY plane to obtain the relationship between the rotation angle of the swing axis B axis and the rotation axis C axis:

According to the Pythagorean theorem:

In the XOY plane according to the law of cosines:

From the measuring device R _B =R _C =L _DBB =400mm, formula (1) and formula (2), the relationship between the rotation angles can be obtained:

4. the detection method about the position-independent error of the double rotary axes of the five-axis CNC machine tool according to claim 1, it is characterized in that in the described step 3, solve the synthetic speed during the coordinated movement of the swing axis B axis and the rotation axis C axis Asynchrony with ballbar capture velocity, including steps:

Step 3.1. The swing axis B axis and the rotation axis C axis rotate from 0° to -90° and 90° to 0° respectively, the swing axis B axis rotates at a constant speed, and the step length is 0.1° corresponding to the rotation axis C axis angle The location of can be given as:

And the angular positions of the B and C axes are:

Step 3.2. Each step measured by the experiment indicates that a semicircular trajectory will be formed. The adjacent steps of the formed semicircular trajectory are not equidistant. The fluctuation of the step along the trajectory will cause the machine tool movement and the club Since the acquisition rate of the ballbar is constant, it is also very important to ensure that the movement is uniform, and the analysis can be effective.

Step 3.3. The track represents the center position of the tool cup. The spindle tool cup is installed on the spindle housing of the B-axis swing shaft, so the axis of the tool cup and the center of the tool cup form a semi-right cone, so the parameters of the cone can be obtained. The radius of the bottom circle of the cone is The hole diameter of the cone is 90°, and the length of the generatrix of the cone is 400mm.

Step 3.4. In order to ensure that the distance between adjacent steps is constant, expand the vertebral body on a two-dimensional plane. If the distance ||OO′|| is r, Also available in the unfolded plane Available expansion angles:

Step 3.5. The central angle surrounded by OB and BP′ is denoted as φ and can be given as:

Step 3.6. The central angle surrounded by OO' and O'P' can be given as Θ, in the bottom circle of the cone, can be given as:

Step 3.7, where N is the midpoint of ||OP′||, based on the trigonometric relationship, the following equation can be given:

Step 3.8, so the relationship between θ _B and Θ can be obtained based on Equations 5-9:

Step 3.9. As long as the center position of the tool cup is evenly distributed in Φ, uniform motion can be achieved. Select 900 steps of equal distance in the middle, and substitute it into the formula Equation 5-10 to form a uniformly distributed motion trajectory.

5. The method for detecting the error of the double rotary axis of a five-axis CNC machine tool according to claim 1, wherein in the step 4, error identification is carried out in combination with the theory of the multi-body motion system of the machine tool and the homogeneous coordinate transformation, including step:

Step 4.1. PIGE of the C-axis of the rotary axis According to ISO230-1, each rotary axis has 4 PIGEs. Considering the zero position compensation function of the CNC, a zero position error can be ignored. The 4 PIGEs are the two linear position error components E _XOC and E _YOC on the X and Y axes in the XOY plane, and the two orientation error components E _AOC and E _BOC around the X and Y axes, respectively. A similar error composition of the B-axis of the swing axis can be obtained based on IOS230-1.

Step 4.2. The total error of the motion axis can be estimated by sequential multiplication of the basic homogeneous transformation matrix. According to the multi-body system theory, the feature transformation matrix from the workpiece coordinate system to the reference coordinate system can be given as follows:

The cutting tool branch can be given similarly to the above expression:

The ideal transformation matrix from the tool center point to the workpiece coordinate system can be given as follows:

Influenced by PIGE in the contact, the actual pose of the transformation matrix is expressed as:

where E is the identity matrix of order 4 × 4, due to geometric errors, Represent a given bias matrix:

Then the actual transformation from the cutting tool center point to the workpiece can be given by:

The letters R, W, T and i represent the reference coordinate system, workpiece coordinate system, cutting tool coordinate system and the coordinate system of the i-th rigid body in the kinematic chain of the target machine tool. D _ideal and D _actual represent the ideal and actual homogeneous transformation matrices, representing the transformation from the coordinate system of its left subscript to one of its left superscript. Rot and Trans respectively describe the transformation of rotation and translation in a homogeneous transformation matrix from its left subscript coordinate system to one of its upper left corners.

Step 4.3. Combined with the experimental measurement data and the model proposed in step 4, the pseudo-inverse method is used to obtain the eight-term geometric position-independent errors of the double rotary axis of the five-axis CNC machine tool.