CN102566511B - Five-shaft numerical control system cutter center point interpolation path interpolation method - Google Patents

Abstract

The invention relates to a five- shaft numerical control system cutter center point interpolation path interpolation method. The method comprises the following steps: determining cutter center point position information, cutter direction information, cutter center point feeding speed and an interpolation period; determining a conversion relation of programming instruction information in a workpiece coordinate system to machine tool coordinate system lower shaft position information; determining a cutter center point interpolation step length and segment length, and a motion stroke of each shaft, and combined with maximum restriction speed of each shaft, calculating shortest shaft interpolation time and shaft interpolation period number which are needed by completing a cutter center point interpolation path; determining a shortest interpolation period number under a speed constraint condition; determining a motion position of each interpolation period of each shaft, and completing motion information calculation of each shaft; when motion of each shaft is in accordance with an acceleration constraint requirement, carrying out three times of batten smooth processing of motion information of each shaft, sending the motion information to a servo, and ending present operation. According to the method, a programming path is subjected to interpolation processing, thus smooth five- shaft processing cutter center point interpolation can be carried out through a five-shaft machine tool with two rotating shafts.

Description

Five-axle numerical control system cutter heart point interpolation path interpolation method

Technical field

The present invention relates to five process technologies in a kind of fields of numeric control technique, specifically a kind of five-axle numerical control system cutter heart point interpolation path interpolation method.

Background technology

As the five-axle number control machine tool of the free form surface of processing metal mould etc., have the parts of turning axle beyond using on linear shifting axle basis.Known have the linear shifting axle of X, Y, Z and a five-axis machine tool of two turning axles, adds man-hour carrying out multiaxis, because the appearance of turning axle can be processed cutter with different angles to workpiece.Appearing at when process flexibility is strengthened greatly of turning axle also makes the establishment of five job sequences become loaded down with trivial details, and be abstract, indigestion.In general, the five-shaft numerical control job sequence is difficult to finish with artificial hand-written mode, and can only handle the NC program that the cutter spacing data that CAD/CAM is generated are converted to concrete lathe by postposition.In case machine tool structure or cutter for same change, original program just can not be used.The cooked mode of this " key is driven once lock ", the low operability of efficient and versatility are poor.In the production in enormous quantities that becomes increasingly complex and accuracy requirement is more and more higher is processed, the serious restriction of this cooked mode the performance of five-axis machine tool working ability and efficient, become the bottleneck that the 5-shaft linkage numerical control processed and applied is promoted and developed, there is following drawback in this tupe:

1. must use expensive CAM software and specific rearmounted process software;

2. processing produces a large amount of small program processing instructions at simple path, needs system to have jumbo memory device to store tediously long job sequence;

3. a large amount of small program segment can increase the weight of the communication load between programing system and the CNC system, reduces the reliability of total system;

4. numerical control device needs plenty of time and processing power to analyze tediously long program, is difficult to the level and smooth processing under the assurance high-precision high-speed;

5. the lathe at the different motion structure need generate different job sequences;

6. can't control the processing speed of feed.

Can directly carry out multiaxis processing based on CAD/CAM system or profiling data for digital control system, need directly carry out interpolation from the instruction point.At this moment, need five-shaft numerical control to take all factors into consideration Machine Tool Dynamics constraint and machining path constraint, by in real-time interpolation, finishing the conversion that programming instruction arrives Machine-Tool Control point under the workpiece coordinate system.

In addition, instruction under the workpiece coordinate system directly drives five-axis machine tool and carries out method for processing and become known technology, program path is carried out being undertaken by program speed F the path interpolation of each interpolation cycle t, carry out the kinematics conversion then, each is processed to drive lathe.But carry out each interpolated point that path interpolation obtain according to program speed F and interpolation cycle t this moment, can not guarantee to retrain apart from the dynamics that satisfies lathe between adjacent interpolated point, may cause each overproof situation to occur in the interpolation process.Turning axle occurs with angular unit simultaneously, the cutter shaft direction interpolating method of vector units form is not handled.

Summary of the invention

Overproof or the discontinuous problem of axle motion that may cause at the real-time interpolation based on instruction that exists in the prior art, the technical problem to be solved in the present invention provides Machine Tool Dynamics constraint that a kind of combining with digital control system controls and the five-axle numerical control system cutter heart point interpolation path interpolation method of machining path constraint, realization continuous five processing cutter heart points interpolation stably.

For solving the problems of the technologies described above, the technical solution used in the present invention is:

Five-axle numerical control system cutter heart point interpolation of the present invention path interpolation method, the digital control system for the five-axis machine tool that has three linear axes and two turning axles by control is used may further comprise the steps:

Instruction is resolved: determine cutter heart dot position information and the tool orientation information of path starting point and terminal point, cutter heart point speed of feed, interpolation cycle; By five-axis machine tool structural parameters in the system, determine that programming instruction information is to the transformational relation of lathe coordinate system lower shaft positional information in the workpiece coordinate system simultaneously;

Path interpolation pre-service: determine cutter heart point interpolation step-length and segment length, and according to the required cutter heart point interpolation cycle number of programming instruction;

Minor axis interpolation Time Calculation: determine to finish needed each movement travel in whole cutter heart point interpolation path, in conjunction with the maximum constraints speed of each, calculate and finish cutter heart point interpolation path required minor axis interpolation time and an axle interpolation cycle number;

The shortest interpolation cycle number of constraint of velocity: according to cutter heart point interpolation cycle number and axle interpolation cycle number, determine the shortest interpolation cycle number under the constraint of velocity condition;

Each interpolation position calculates: count the tool setting heart locus of points according to the shortest interpolation cycle and handle, determine the movement position of each each interpolation cycle, calculate the movable information of finishing each by inverse kinematics then and calculate;

The acceleration constraint is judged: each carried out the acceleration constraint judges, and then servo with issuing after each movable information process cubic spline smoothing processing when each motion meets the acceleration constraint requirements, finish this operation.

When if each motion does not meet the acceleration constraint requirements, return minor axis interpolation Time Calculation step.

The cutter heart point interpolation time is:

Wherein, L is the displacement of the center cutter point of each interpolation cycle under the instruction speed F, and D is the center cutter point distance segment length that starting point arrives terminal point, and t is interpolation cycle.

The displacement L of the center cutter point of each interpolation cycle under the instruction speed F is:

L＝F×t

Wherein F is cutter heart point speed of feed.

Starting point to the center cutter point distance segment length D of terminal point is:

$D=\sqrt{({(x_e-x_s)}^2+{(y_e-y_s)}^2+{(z_e-z_s)}^2)}$

Wherein, x _s, y _s, z _sBe the center cutter point position coordinates of path starting point, x _e, y _e, z _eCenter cutter point position coordinates for the path terminus.

The minor axis interpolation time calculates by following formula

$t_{\min }=\max (\frac{\mathrm{\Δx}}{n_{\mathrm{mx}}},\frac{\mathrm{\Δy}}{n_{\mathrm{my}}},\frac{\mathrm{\Δz}}{n_{\mathrm{mz}}},\frac{\mathrm{\Δ\α}}{n_{\mathrm{m\α}}},\frac{\mathrm{\Δ\β}}{n_{\mathrm{m\β}}})$

Wherein, each maximal rate is respectively n _Mx, n _My, n _Mz, n _MaAnd n _Mc, each movement travel is respectively Δ x, Δ y, Δ z, Δ α and Δ B.

The shortest interpolation cycle number of constraint of velocity is

Wherein, L is the displacement of the center cutter point of each interpolation cycle under the instruction speed, and D is the center cutter point distance segment length that starting point arrives terminal point, and t is interpolation cycle, t _MinBe the minor axis interpolation time.

The present invention has following beneficial effect and advantage:

1. the present invention is when carrying out the interpolation of cutter heart point, the Machine Tool Dynamics constraint that the combining with digital control system controls and machining path constraint, program path is carried out interpolation processing, thereby can carry out five processing cutter heart points interpolation stably by having the five-axis machine tool of 2 turning axles.

Description of drawings

Fig. 1 is for implementing the digital control system structural drawing of the inventive method;

Fig. 2 is the process flow diagram of the inventive method.

Embodiment

Fig. 1 is digital control system 10 structural drawing that are suitable for parameter configuration mode of the present invention.Based on component model, with bus the digital control system structure has been comprised human interface components 21, task controller assembly 22, PLC assembly 24, motion controller assembly 23 and control bus 25 assemblies and be connected in the digital control system 10.

Wherein human interface components 21: be responsible for user management, data acquisition, transmission new data to controller and user interface that unanimity is provided for various device, also need the needed various information of explicit user simultaneously, as job sequence, at present conditions of machine tool, the data handled etc.

Task controller assembly 22: explain and carry out job sequence, add process sequence control in man-hour and for detection diagnosis and the processing capacity of mistake.According to part program, task controller controlled motion controller and I/O controller are finished processing tasks.

PLC assembly 24: be responsible for the I/O control of sensor and actuator, mainly comprise lathe power-on and power-off, emergency stop switch, cold switch etc.

Motion controller assembly 23: be responsible for detecting each kinematic axis current location, calculate next movement position and result of calculation is sent to the control bus assembly to control execution etc. with command forms.

Control bus assembly 25: be responsible for from motion controller assembly and PLC assembly, receiving order, and order is sent in the bus driver card to drive digital servo 26, simultaneously servo condition is fed back to motion controller assembly 23 and PLC assembly 24.

In the present embodiment, with digital control system 10 control gang tools, have X-axis, Y-axis, Z axle and A axle, the B axle of linear axes, 2 turning axles in the C axle.Each axle control structure outputs to servo 26 from the axle movement instruction of control bus 25 with each instruction.Servo 26 organization instructions drive each servo motor 34.Servo motor 34 is built-in with the speed/positional detecting device simultaneously, will feed back in the meeting servo 26 from the speed/positional feedback signal of this speed/positional detecting device, carries out the FEEDBACK CONTROL of speed/positional.

As shown in Figure 2, five-axle numerical control system cutter heart point interpolation of the present invention path interpolation method, the digital control system for the five-axis machine tool that has three linear axes and two turning axles by control is used may further comprise the steps:

Instruction is resolved: determine cutter heart dot position information and the tool orientation information of path starting point and terminal point, cutter heart point speed of feed, interpolation cycle; By five-axis machine tool structural parameters in the system, determine that programming instruction information is to the transformational relation of lathe coordinate system lower shaft positional information in the workpiece coordinate system simultaneously;

Path interpolation pre-service: determine cutter heart point interpolation step-length and segment length, and according to the required cutter heart point interpolation cycle number of programming instruction;

Minor axis interpolation Time Calculation: determine to finish needed each movement travel in whole cutter heart point interpolation path, in conjunction with the maximum constraints speed of each, calculate and finish cutter heart point interpolation path required minor axis interpolation time and an axle interpolation cycle number;

The shortest interpolation cycle number of constraint of velocity: according to cutter heart point interpolation cycle number and axle interpolation cycle number, determine the shortest interpolation cycle number under the constraint of velocity condition;

Each interpolation position calculates: count the tool setting heart locus of points according to the shortest interpolation cycle and handle, determine the movement position of each each interpolation cycle;

Acceleration constraint is judged: each is carried out acceleration constraint judgement, when each motion meets the acceleration constraint requirements, then each movable information is carried out issuing after the cubic spline optimization servo, finish this operation;

When if each motion does not meet the acceleration constraint requirements, return minor axis interpolation Time Calculation step.

Calculating and finishing the required minor axis interpolation time of cutter heart point interpolation path is according to each interpolation stroke, and the maximal rate of each permission, guarantee the shortest interpolation Time Calculation that each arrives simultaneously, according to cutter heart point routing information and cutter heart point programming speed of feed, calculate the cutter heart point interpolation time.

Comprise the job sequence that uses CAD/CAM system or profiling data directly to carry out multiaxis processing from data input device 31 by man-machine interface (HMI) 21 inputs.If each is linear axes X-axis, Y-axis and Z axle for the five-axis machine tool that digital control system 10 is controlled, turning axle is α axle and β axle.

In the instruction analyzing step, at first the concrete lathe configuring condition of controlling according to digital control system utilizes formula (1) and formula (2), and can obtain turning axle and generating tool axis vector and instruction point and the kinematics transformational relation of each has

(i _i j _i k _i)＝F _R(α _i，β _i)(1)

(x _i y _i z _i)＝F _L(x _mi y _mi z _miα _iβ _i)(2)

(i in formula 1 and the formula 2 _ij _ik _i) be the generating tool axis vector under arbitrary i interpolation workpiece coordinate system constantly, (x _Miy _Miz _Miα _iβ _i) be each shaft position instruction under arbitrary i interpolation moment lathe coordinate system.

Suppose to obtain path starting point under the workpiece coordinate system and the center cutter point coordinate of terminal point is p by instruction _s=(x _sy _sz _s) and p _e=(x _ey _ez _e), the tool orientation vector is the q that vector form is described _s=(i _sj _sk _s) and q _e=(i _ej _ek _e) or (α of turning axle instruction type _s, β _s) and (α _e, β _e), cutter heart point speed of feed is F, interpolation cycle t.

In the interpolation pre-treatment step of path, obtained the displacement L of the center cutter point of each interpolation cycle under the instruction speed F by formula (3) earlier.

L＝F×t (3)

Again according to starting point and terminal point center cutter point position (x _sy _sz _s) and (x _ey _ez _e), obtain starting point to the center cutter point distance segment length D of terminal point by formula (4).

$D=\sqrt{({(x_e-x_s)}^2+{(y_e-y_s)}^2+{(z_e-z_s)}^2)}---\left(4\right)$

In minor axis interpolation Time Calculation step, according to the information of starting point and terminal point, through type (1) and formula (2) can obtain each stroke in the interpolation process

$\left\{\begin{array}{c}\mathrm{\Δx}=|x_{\mathrm{me}}-x_{\mathrm{ms}}|\\ \mathrm{\Δy}=|y_{\mathrm{me}}-y_{\mathrm{ms}}|\\ \mathrm{\Δz}=|z_{\mathrm{me}}-z_{\mathrm{ms}}|\\ \mathrm{\Δ\α}=|{\mathrm{\α}}_{\mathrm{me}}-{\mathrm{\α}}_{\mathrm{ms}}|\\ \mathrm{\Δ\β}=|{\mathrm{\β}}_{\mathrm{me}}-{\mathrm{\β}}_{\mathrm{ms}}|\end{array}\right.---\left(5\right)$

Because in the machine tool structure, the performance of each is different, also needs to determine transition shortest time t _MinGuarantee that each can arrive simultaneously.If each maximal rate is respectively n _Mx, n _My, n _Mz, n _MaAnd n _McThen have

$t_{\min }=\max (\frac{\mathrm{\Δx}}{n_{\mathrm{mx}}},\frac{\mathrm{\Δy}}{n_{\mathrm{my}}},\frac{\mathrm{\Δz}}{n_{\mathrm{mz}}},\frac{\mathrm{\Δ\α}}{n_{\mathrm{m\α}}},\frac{\mathrm{\Δ\β}}{n_{\mathrm{m\β}}})---\left(6\right)$

Count in the n solution procedure at the shortest interpolation cycle, according to formula (5) and formula (6), can obtain that the maximum speed of clamping down on of each is in the interpolation process

$\left\{\begin{array}{c}{n}_x=\frac{\mathrm{\Δx}}{t_{\min }}\\ n_y=\frac{\mathrm{\Δy}}{t_{\min }}\\ n_z=\frac{\mathrm{\Δz}}{t_{\min }}\\ n_{\mathrm{\α}}=\frac{\mathrm{\Δ\α}}{t_{\min }}\\ n_{\mathrm{\β}}=\frac{\mathrm{\Δ\β}}{t_{\min }}\end{array}\right.$

If n be cutter heart point from the required interpolation hop count of origin-to-destination, then have

Interpolation time when at this moment, cutter heart spot speed is F is t _t=nt.Through type (7) can obtain interpolation hop count n required from the starting point to the terminal point

In inverse kinematics calculating and each movable information calculation procedure, after having determined interpolation hop count n, to starting point (x _sy _sz _s) and terminal point (x _ey _ez _e) the center cutter point path that forms carries out the n five equilibrium, utilizes formula (8) to obtain the center cutter point interpolation position of each interpolation cycle, have

$\left\{\begin{array}{c}{x}_i=i\×[(x_e-x_s)/n]+x_s\\ y_i=i\×[(y_e-y_s)/n]+y_s\\ z_i=i\×[(z_e-z_s)/n]+z_s\end{array}\right.---\left(8\right)$

I=0 in the formula, 1 ..., n.(x _iy _iz _i) center cutter point position coordinates when being each interpolation cycle.

Next carry out analyzing and processing to rotatablely moving, if turning axle adopts the linear interpolation mode, the turning axle angle of then using formula (9) to obtain each interpolation cycle is

$\left\{\begin{array}{c}{\mathrm{\α}}_i=i\×[({\mathrm{\α}}_e-{\mathrm{\α}}_s)/n]+{\mathrm{\α}}_s\\ {\mathrm{\β}}_i=i\×[({\mathrm{\β}}_e-{\mathrm{\β}}_s)/n]+{\mathrm{\β}}_s\end{array}\right.---\left(9\right)$

If turning axle adopts the vector interpolation mode, then at first with start vector (i _sj _sk _s) and finish vector (i _ej _ek _e), carry out the n five equilibrium, obtain the generating tool axis vector (i of each interpolation cycle _ij _ik _i).Use formula (1) to obtain corresponding turning axle angle then

Determining the center cutter point coordinate (x of each interpolation cycle _iy _iz _i) and turning axle coordinate (α _iβ _i) after, use formula (2) obtains corresponding each the reference mark positional information (x of each interpolation cycle _Miy _Miz _Miα _iβ _i).

In acceleration constraint determining step, based on each interpolation of obtaining each movement position information of lathe constantly, carry out acceleration constraint judgement.Be example with the X-axis, the location point sequence is { x _s, x ₁..., x _I-1, x _i, x _I+1..., x _e.If the permission peak acceleration of X-axis is α _Xmax, then use formula (10) to the x axle acceleration α of i interpolation section _XiCalculate.

$a_{\mathrm{xi}}=\frac{x_{i+1}+x_{i-1}-{2x}_i}{t^2}---\left(10\right)$

I=0 in the formula, 1 ..., n-1.If the intersegmental acceleration of each interpolation satisfies peak acceleration constraint, then each of trying to achieve reference mark information is carried out cubic spline and is issued servo 26 after level and smooth.If the intersegmental acceleration of each interpolation does not satisfy the peak acceleration constraint, then with interpolation hop count n, increase progressively to handle and continue to handle after getting n=n+1, after satisfying peak acceleration constraint condition, again each reference mark information of trying to achieve is carried out cubic spline and issue servo 26 after level and smooth.

Claims (6)

1. five-axle numerical control system cutter heart point interpolation path interpolation method is used for having the digital control system that the five-axis machine tool of three linear axes and two turning axles is used by control, it is characterized in that may further comprise the steps:

Instruction is resolved: determine cutter heart dot position information and the tool orientation information of path starting point and terminal point, cutter heart point speed of feed, interpolation cycle; By five-axis machine tool structural parameters in the system, determine that programming instruction information is to the transformational relation of lathe coordinate system lower shaft positional information in the workpiece coordinate system simultaneously;

Path interpolation pre-service: determine cutter heart point interpolation step-length and segment length, and according to the required cutter heart point interpolation cycle number of programming instruction;

Minor axis interpolation Time Calculation: determine to finish needed each movement travel in whole cutter heart point interpolation path, in conjunction with the maximum constraints speed of each, calculate and finish cutter heart point interpolation path required minor axis interpolation time and an axle interpolation cycle number;

The shortest interpolation cycle number of constraint of velocity: according to cutter heart point interpolation cycle number and axle interpolation cycle number, determine the shortest interpolation cycle number under the constraint of velocity condition;

Each interpolation position calculates: count the tool setting heart locus of points according to the shortest interpolation cycle and handle, determine the movement position of each each interpolation cycle, calculate the movable information of finishing each by inverse kinematics then and calculate;

The acceleration constraint is judged: each carried out the acceleration constraint judges, and then servo with issuing after each movable information process cubic spline smoothing processing when each motion meets the acceleration constraint requirements, finish this operation.

2. by the described five-axle numerical control system cutter of claim 1 heart point interpolation path interpolation method, it is characterized in that: if when each motion does not meet the acceleration constraint requirements, return minor axis interpolation Time Calculation step.

3. by the described five-axle numerical control system cutter of claim 1 heart point interpolation path interpolation method, it is characterized in that:

The cutter heart point interpolation time is:

Wherein, L is the displacement of the cutter heart point of each interpolation cycle under the instruction speed F, and D is the cutter heart point distance segment length that starting point arrives terminal point, and t is interpolation cycle.

4. by the described five-axle numerical control system cutter of claim 3 heart point interpolation path interpolation method, it is characterized in that:

The displacement L of the cutter heart point of each interpolation cycle under the instruction speed F is:

L=F×t。

5. by the described five-axle numerical control system cutter of claim 3 heart point interpolation path interpolation method, it is characterized in that:

Starting point to the cutter heart point distance segment length D of terminal point is:

$D=\sqrt{({(x_e-x_s)}^2+{(y_e-y_s)}^2+{(z_e-z_s)}^2)}$

Wherein, x _s, y _s, z _sBe the cutter heart point position coordinates of path starting point, x _e, y _e, z _eCutter heart point position coordinates for path termination;

The minor axis interpolation time calculates by following formula

$t_{\min }=\max (\frac{\mathrm{\Δx}}{n_{\mathrm{mx}}},\frac{\mathrm{\Δy}}{n_{\mathrm{my}}},\frac{\mathrm{\Δz}}{n_{\mathrm{mz}}},\frac{\mathrm{\Δ\α}}{n_{\mathrm{m\α}}},\frac{\mathrm{\Δ\β}}{n_{\mathrm{m\β}}})$

Wherein, each maximal rate is respectively n _Mx, n _My, n _Mz, n _{M α}And n _{M β}, each movement travel is respectively Δ x, Δ y, Δ z, Δ α and Δ β.

6. by the described five-axle numerical control system cutter of claim 1 heart point interpolation path interpolation method, it is characterized in that:

The shortest interpolation cycle number of constraint of velocity is

Wherein, L is the displacement of the cutter heart point of each interpolation cycle under the instruction speed, and D is the cutter heart point distance segment length that starting point arrives terminal point, and t is interpolation cycle, t _MinBe minor axis interpolation time, t _tBe the cutter heart point interpolation time.

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