CN101957611A - Spline real-time interpolation method - Google Patents

Abstract

The invention relates to a spline real-time interpolation method which comprises the following steps: carrying out the spline segment preprocessing on a processing program to obtain the curve length and catastrophe point information; carrying out speed planning according to the curve length and the catastrophe point information to obtain the processing speed; according to the obtained processing speed to calculate the coordinates of the next point, and outputting the coordinates to a servo control device, wherein the spline segment preprocessing is as follows: an input processing program: setting the initial speed of the current curve segment; according to the error restraining, accelerated speed restraining and jerk restraining, planning the current speed; if the planned current speed is a catastrophe point, adding the catastrophe point into a catastrophe group; working out the coordinates of the next interpolation point; if the program is ended, outputting the processed result to a real-time interpolation module, and reading in the next segment of the processing program; and returning to the step of setting the initial speed of the current program segment. The invention can ensure that each interpolation period can output one reliable interpolation point in real time, and can obtain a speed-down point with high precision, has good interactivity and can response the trimming operation in real time.

Description

SPL real-time interpolation method

Technical field

The present invention relates to the velocity process technology of digital control system, specifically a kind of SPL real-time interpolation method.

Background technology

In commercial CAD/CAM (computer-aided design/computer-aidedmanufacturing, CAD (computer aided design) and computer are auxiliary to be made) software, the free type curve and surface is represented by batten.But the development of CNC (Computer numerical control, computer numerical control (CNC)) system will lag behind CAD/CAM system, and traditional CNC system only possesses circular arc and linear interpolation function, has limited the further raising of numerical control (NC) Machining Accuracy and efficient.In order to overcome the drawback that traditional straight line, circular interpolation bring, need in numerical control device, directly carry out interpolation and calculate the SPL of CAD/CAM device output.

Compare with little line segment, the shape of SPL is more complicated, and its curvature is constantly to change, and has the curvature point of discontinuity, and this has just brought a lot of problems to speed planning.At first, deceleration point is difficult to accurate Calculation.When little line segment was carried out speed planning, we generally obtained the total length when preplanning section path earlier, carry out speed planning according to residual paths length then, obtain deceleration point.When SPL is carried out real-time interpolation, be to go to approach original SPL with actual step size, the path that different approach methods calculates is also different, and concrete approach method is relevant with speed planning, therefore is difficult to accurately obtain the deceleration point position.In the speed planning process, at first obtain the maximum speed value that allows under the current curvature simultaneously, adjust according to the acceleration and deceleration ability of lathe then according to machining precision at each interpolated point.But have the catastrophe point (curvature discrete point) of curvature in the SPL, this has also just caused the speed of being asked to undergo mutation.Adopt pretreated method can obtain the catastrophe point of speed and acceleration in advance, and cook up rate curve.But repair in process when transferring operation, the rate curve that can cause cooking up lost efficacy, and need recomputate, demand that can not the real-time response user.Adopt the method for real time forward looking real-time response to repair operations such as accent, but because the SPL calculated amount is big, the speed planning complexity, all calculating are finished by real time forward looking fully, are difficult to requirement of real time.

In recent years, existing both at home and abroad a large amount of relevant theoretical researches and obtained bigger progress.The real-time interpolation technology of SPL has experienced constant speed of feed, has regulated this several stages of speed of feed and pre-service automatically.The problem of being considered also expands to the actual acceleration and deceleration ability of lathe from initial working (machining) efficiency, precision.But these algorithms exist calculated amount big, are difficult to requirement of real time, and deceleration point calculates the problem such as accent of repairing not accurate enough and that occur in the processing process in real time, therefore can not be grafted directly to have now in the digital control system.

Summary of the invention

At above shortcomings part in the prior art, the technical problem to be solved in the present invention provides a kind of SPL real-time interpolation algorithm that can realize speed smooth transition, guaranteeing the even running of each kinematic axis, thereby satisfies the requirement of flexibility processing.

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

A kind of SPL real-time interpolation of the present invention method may further comprise the steps:

SPL section pre-service: job sequence is carried out the pre-service of SPL section, obtain length of curve and catastrophe point information;

Real time forward looking: carry out speed planning according to above-mentioned length of curve and catastrophe point information, obtain process velocity;

Interpolation is calculated: calculate next point coordinate according to the process velocity that obtains, export Servocontrol device to.

Describedly job sequence is carried out the pre-service of SPL section may further comprise the steps:

Import job sequence, the initial velocity of current curves section is set;

According to error constraint, acceleration constraint and acceleration constraint planning present speed;

Is the present speed of judging planning a catastrophe point?

If catastrophe point then adds the catastrophe point array with this catastrophe point;

Obtain next interpolated point coordinate;

Judge whether the current curves section finishes;

As finishing, export result to the real-time interpolation module, and read in next section of job sequence;

Return the initial velocity step that the present procedure section is set.

Described real time forward looking may further comprise the steps:

The initial velocity of processing is set;

According to error constraint, acceleration constraint, acceleration constraint and be programmed into constraint speed to constraint of velocity condition calculating processing;

Ask down some positions according to constraint speed;

According to being programmed into to Velocity Updating catastrophe point array;

Whether the residual paths length under judging between some positions and all catastrophe points is all greater than required deceleration distance;

, then reduce speed now, and recomputate present speed for not as above-mentioned judged result from current point;

Export present speed to the interpolation calculation procedure, and go to according to error constraint, acceleration constraint, acceleration constraint and be programmed into constraint speed step to constraint of velocity condition calculating processing.

Whether the residual paths length under judging between some positions and all catastrophe points all may further comprise the steps greater than required deceleration distance:

From the catastrophe point array, take out catastrophe point successively;

The length of curve information calculations that obtains according to pre-service from some positions down to the distance of this catastrophe point;

Judge successively that according to following any acceleration and the acceleration of speed, catastrophe point and speed whether the residual paths length between some positions and catastrophe point is greater than required deceleration distance down.

If the residual paths length between some positions and all catastrophe points is all greater than required deceleration distance, then continuing exports present speed to the interpolation calculation procedure, and goes to according to error constraint, acceleration constraint, acceleration constraint and be programmed into constraint speed step to constraint of velocity condition calculating processing.

If the current curves section does not finish, then go to according to error constraint, acceleration constraint and acceleration constraint planning present speed step.

If not catastrophe point, then directly enter and obtain next interpolated point coordinate step.

The present invention has following beneficial effect and advantage:

1. real-time is good.In conjunction with prediction and pretreated advantage, adopt the implementation of pre-service+prediction, calculated amount is repaiied the work of transferring operating influence greatly and not to be placed on pre-service and to finish, thereby reduced the calculated amount of real time forward looking, make the prediction hop count long enough in each cycle, can guarantee each interpolation cycle reliable interpolated point of output in real time.

2. ask deceleration point precision height.Employing avoids technology such as deviation accumulation and real time forward looking to make the position of the deceleration point of asking more accurate, can not occur not satisfying the phenomenon of machining precision because of deceleration distance causes part point inadequately.

3. interaction is good, can real-time response repair the accent operation.

Description of drawings

Fig. 1 is the inventive method process flow diagram;

Curvature point of discontinuity example in Fig. 2 SPL;

Fig. 3 is a batten pretreatment module process flow diagram;

Fig. 4 real-time interpolation module process flow diagram;

Fig. 5 curve exemplary plot to be processed;

The accelerating curve of Fig. 6 expectation;

Fig. 7 (a)～7 (d) is for to decelerate to the speed of catastrophe point, possible transient mode ()～(four) of acceleration from present speed, acceleration;

Fig. 8 processes the exemplar diagrammatic sketch;

The graph of errors design sketch of Fig. 9 the inventive method;

The rate curve design sketch of Figure 10 the inventive method;

The acceleration plots of Figure 11 the inventive method;

The accelerating curve part amplification effect figure of Figure 12 the inventive method.

Embodiment

Below in conjunction with accompanying drawing the present invention is described in further detail.

The inventive method may further comprise the steps:

SPL section pre-service: job sequence is carried out the pre-service of SPL section, obtain length of curve and catastrophe point information;

Real time forward looking: carry out speed planning according to above-mentioned length of curve and catastrophe point information, obtain process velocity;

Interpolation is calculated: calculate next point coordinate according to the process velocity that obtains, export Servocontrol device to.

As shown in Figure 1, in the present embodiment, the job sequence of exporting from the CAD/CAM device at first enters the interpreter of numerical control device, interpreter is divided into job sequence to be explained and SPL section pre-service two parts, it makes an explanation and pre-service to job sequence, and will handle data well and issue motion controller by shared buffer memory.Motion controller is real-time, and it carries out each interpolation cycle speed planning and calculate next interpolated point coordinate by real time forward looking and interpolation calculating, at last this coordinate is sent to servomechanism installation, the drive motor motion.

With reference to shown in Figure 2, there be the curvature discrete point in the SPL, and when curved transition is too fast, the point of lathe slowing down power(SDP) also can occur exceeding.In order to guarantee that actual to add man-hour be continuous at these acceleration, need these points be noted at SPL section pretreatment stage.

The pretreated system flowchart of SPL section describedly carries out the pre-service of SPL section to job sequence and may further comprise the steps as shown in Figure 3:

S1: import job sequence, the initial velocity of current curves section is set;

S2: according to error constraint, acceleration constraint and acceleration constraint planning present speed;

Is S3: the present speed of judging planning a catastrophe point? if catastrophe point then adds the catastrophe point array with this catastrophe point;

S4: obtain next interpolated point coordinate;

S5: judge whether the current curves section finishes;

S6: as finishing, export result to the real-time interpolation module, and read in next section of job sequence, return the initial velocity step that the present procedure section is set.

Because SPL is segmentation, and the catastrophe point of curvature is present in segmentation link place mostly, and for fear of owing to repair pre-service that operation such as accent causes Problem of Failure as a result, we regard SPL as segmentation independently when pre-service.

In each segmentation starting point, step S1 thinks that initial velocity is the maximal rate that a last segmentation last point error allows.If ER is (u _i), ρ (u _i) and V (u _i) be respectively interpolated point u _iBow high level error, radius-of-curvature and the speed at place, T _sBe the interpolation cycle of lathe, the bow high level error maximal value of ER for allowing, J _MaxBe the maximum acceleration that allows, A _MaxBe the peak acceleration that allows.u _iThe maximal rate V that place's error, peak acceleration, acceleration allow _e(u _i), V _a(u _i) and V _j(u _i) be respectively:

The error constraint formulations: $V_e\left(u_i\right)=\frac{2}{T_s}\sqrt{2\mathrm{\ρ}\left(u_i\right)\mathrm{ER}-{\mathrm{ER}}^2}---\left(1\right)$

Acceleration constraint formulations: V _a(u _i)=V (u _I-1)+A _MaxT _s(2)

Acceleration constraint formulations: V _j(u _i)=V (u _I-1)+(a (u _I-1)+J _MaxT _s) T _s(3)

When step S2 asks constraint speed according to above-mentioned each formula, not consider to be programmed into to constraint of velocity, present speed is V (u _i)=min (V _e(u _i), V _a(u _i), V _j(u _i)).Note the knot vector of this point simultaneously, acceleration, speed and starting point are to the cumulative path length of this point.Step S3 is judged to be catastrophe point with the point that meets the following conditions simultaneously: 1) speed of obtaining according to constraint conditions such as machining precision, peak acceleration, accelerations is got minimum value as current spot speed, and this speed is compared the lathe acceleration and deceleration ability that exceeds with last spot speed; 2) current spot speed needs to slow down less than last spot speed.If current interpolated point is catastrophe point, the nodal information that will put then, information such as speed, acceleration record in another array, press the interpolation successively in the catastrophe point array of interpolation order.

Described real time forward looking may further comprise the steps:

P1: the initial velocity that processing is set; According to error constraint, acceleration constraint, acceleration constraint and be programmed into constraint speed to constraint of velocity condition calculating processing;

P2: ask down some positions according to constraint speed;

P3: according to being programmed into to Velocity Updating catastrophe point array;

P4: whether the residual paths length under judging between some positions and all catastrophe points is all greater than required deceleration distance;

P5: for not, then reduce speed now, and recomputate present speed from current point as above-mentioned judged result;

P6: export present speed to the interpolation calculation procedure, and go to according to error constraint, acceleration constraint, acceleration constraint and be programmed into constraint speed step to constraint of velocity condition calculating processing.

Real time forward looking carries out accurate speed planning according to the information that pre-service is noted, as shown in Figure 4, it is 0 that initial velocity is set, and supposes that the programming speed of feed is F, and each cycle is at first calculated constraint speed V (u according to constraint conditions such as error, programming speed of feed, peak acceleration, accelerations _i)=min (F, V _e(u _i), V _a(u _i), V _j(u _i)), and obtain down some position P according to this speed _I+1

Owing in real time forward looking, will limit real-time interpolation speed according to the programming speed of feed, can produce new catastrophe point, therefore need in step P3, upgrade the catastrophe point array, promptly increase new catastrophe point.Because this catastrophe point only may be near the maximum point of speed can be occurred, so the specific implementation method is: remember first point that surpasses the speed of feed of programme for going into a little, last surpasses the point of the speed of feed of programming for going out a little.The acceleration of going into a little and going out a little is made as zero, and speed is made as the programming speed of feed.If the acceleration change amount absolute value of going into a little or go out next one point a little is greater than J _MaxT then joins it in catastrophe point array.

Step P4 judges P _I+1Whether the residual paths length between all catastrophe points on point and the prediction segment of curve satisfies required deceleration distance, and concrete decision method is as follows:

At first calculate required deceleration distance, suppose that Fig. 5 is one section SPL to be processed, wherein u _iA catastrophe point that obtains when being the pre-service of SPL section, its next interpolated point acceleration is a _I+1, u _jBe sampled point u _iDeceleration point, its previous interpolated point acceleration is a _J-1Realize the continuity of whole process acceleration, as shown in Figure 6, need to guarantee that braking section starting point and terminal point acceleration all are continuous.Therefore be to judge whether what needs slowed down at step P2 according to the speed and required minimum process path and the relation between the residual paths length between them of acceleration that carry out the transition to catastrophe point from current speed and acceleration.The computing method of required minimum process path are as follows:

Suppose that present speed is V _i, acceleration is a _i, the required speed of catastrophe point is V _j, acceleration is a _jMay there be four kinds of transient modes shown in Fig. 7 (a)～(d) in the speed and the acceleration that carry out the transition to catastrophe point from current speed and acceleration.If catastrophe point is the acceleration catastrophe point shown in Fig. 7 (a), from V _iCarry out the transition to V _jRequired apart from S and time t is:

$S=V_{i}t+\frac{1}{2}{a}_i{t}^2-\frac{1}{6}{J}_{\max }{t}^3---\left(4\right)$

$t=\frac{a_i-a_j}{J_{\max }}---\left(5\right)$

If carry out the transition to the catastrophe point accelerating curve shown in Fig. 7 (b), from V from current point _iCarry out the transition to V _jRequired apart from S and time t is:

$S=V_{i}t+\frac{1}{2}{a}_{\mathrm{<figure-callout\; id="2"\; label="i\; t"\; filenames="H2009100125839E0000062.png"\; state="\{\{state\}\}">i</figure-callout>}}{t}^{}{}^2+\frac{1}{6}{J}_{\max }{t}^3---\left(6\right)$

$t=\frac{a_j-a_i}{J_{\max }}---\left(7\right)$

If bigger, there are Fig. 7 (c) and two kinds of situations of Fig. 7 (d) when then slowing down from the velocity variations of this catastrophe point and current point.At first existence is with acceleration-A _MaxEven situation of slowing down, in order to guarantee the continuity of acceleration, whole moderating process is divided into acceleration and is-J _MaxChange acceleration, acceleration be-A _MaxEven acceleration and acceleration are J _MaxThe change accelerator.Wherein acceleration is-J _MaxThe displacement S1 of change boost phase, terminal velocity V ₁With time t ₁Be respectively:

${\mathrm{<figure-callout\; id="1"\; label="S"\; filenames="H2009100125839E0000031.png,H2009100125839E0000041.png"\; state="\{\{state\}\}">S</figure-callout>}}_1={\mathrm{<figure-callout\; id="1"\; label="V\; i\; t"\; filenames="H2009100125839E0000031.png,H2009100125839E0000041.png"\; state="\{\{state\}\}">V</figure-callout>}}_i{t}_{}{}_1+\frac{1}{2}{a}_{\mathrm{<figure-callout\; id="1"\; label="i\; t"\; filenames="H2009100125839E0000031.png,H2009100125839E0000041.png"\; state="\{\{state\}\}">i</figure-callout>}}{t}_{}^{}{}_1^2-\frac{1}{6}{\mathrm{<figure-callout\; id="1"\; label="J\; max\; t"\; filenames="H2009100125839E0000031.png,H2009100125839E0000041.png"\; state="\{\{state\}\}">J</figure-callout>}}_{\max }{t}_{}^{}{}_1^3---\left(8\right)$

${\mathrm{<figure-callout\; id="1"\; label="V"\; filenames="H2009100125839E0000031.png,H2009100125839E0000041.png"\; state="\{\{state\}\}">V</figure-callout>}}_1=V_i+a_i{t}_1-\frac{1}{2}{\mathrm{<figure-callout\; id="1"\; label="J\; max\; t"\; filenames="H2009100125839E0000031.png,H2009100125839E0000041.png"\; state="\{\{state\}\}">J</figure-callout>}}_{\max }{t}_{}^{}{}_1^2---\left(9\right)$

${\mathrm{<figure-callout\; id="1"\; label="t"\; filenames="H2009100125839E0000031.png,H2009100125839E0000041.png"\; state="\{\{state\}\}">t</figure-callout>}}_1=\frac{a_i+A_{\max }}{J_{\max }}---\left(10\right)$

Acceleration is-A _MaxThe displacement S of even boost phase ₂With terminal velocity V ₂Be respectively:

${\mathrm{<figure-callout\; id="2"\; label="S"\; filenames="H2009100125839E0000062.png"\; state="\{\{state\}\}">S</figure-callout>}}_2=V_1{t}_2-\frac{1}{2}{A}_{\mathrm{<figure-callout\; id="2"\; label="max\; t"\; filenames="H2009100125839E0000062.png"\; state="\{\{state\}\}">max</figure-callout>}}{t}_{}^{}{}_2^2---\left(11\right)$

V ₂＝V ₁-A _maxt ₂ (12)

Acceleration is J _MaxThe displacement S of change boost phase ₃With this duration in stage t ₃For:

${\mathrm{<figure-callout\; id="3"\; label="S"\; filenames="H2009100125839E0000062.png"\; state="\{\{state\}\}">S</figure-callout>}}_3=V_2{t}_3-\frac{1}{2}{A}_{\mathrm{<figure-callout\; id="3"\; label="max\; t"\; filenames="H2009100125839E0000062.png"\; state="\{\{state\}\}">max</figure-callout>}}{t}_{}^{}{}_3^2+\frac{1}{6}{\mathrm{<figure-callout\; id="3"\; label="J\; max\; t"\; filenames="H2009100125839E0000062.png"\; state="\{\{state\}\}">J</figure-callout>}}_{\max }{t}_{}^{}{}_3^3---\left(13\right)$

${\mathrm{<figure-callout\; id="3"\; label="t"\; filenames="H2009100125839E0000062.png"\; state="\{\{state\}\}">t</figure-callout>}}_3=\frac{a_j+A_{\max }}{J_{\max }}---\left(14\right)$

The speed increment sum in each stage satisfies following relational expression:

$a_i{t}_1-\frac{1}{2}{\mathrm{<figure-callout\; id="1"\; label="J\; max\; t"\; filenames="H2009100125839E0000031.png,H2009100125839E0000041.png"\; state="\{\{state\}\}">J</figure-callout>}}_{\max }{t}_{}^{}{}_1^2-A_{\max }{t}_2-{\mathrm{<figure-callout\; id="3"\; label="A\; max\; t"\; filenames="H2009100125839E0000062.png"\; state="\{\{state\}\}">A</figure-callout>}}_{\max }{t}_{}{}_3+\frac{1}{2}{\mathrm{<figure-callout\; id="3"\; label="J\; max\; t"\; filenames="H2009100125839E0000062.png"\; state="\{\{state\}\}">J</figure-callout>}}_{\max }{t}_{}^{}{}_3^2=V_j-V_i---\left(15\right)$

Therefore can get the time t of subordinate phase ₂:

${\mathrm{<figure-callout\; id="2"\; label="t"\; filenames="H2009100125839E0000062.png"\; state="\{\{state\}\}">t</figure-callout>}}_2=(a_i{t}_1-\frac{1}{2}{\mathrm{<figure-callout\; id="1"\; label="J\; max\; t"\; filenames="H2009100125839E0000031.png,H2009100125839E0000041.png"\; state="\{\{state\}\}">J</figure-callout>}}_{\max }{t}_{}^{}{}_1^2-{\mathrm{<figure-callout\; id="3"\; label="A\; max\; t"\; filenames="H2009100125839E0000062.png"\; state="\{\{state\}\}">A</figure-callout>}}_{\max }{t}_{}{}_3+\frac{1}{2}{\mathrm{<figure-callout\; id="3"\; label="J\; max\; t"\; filenames="H2009100125839E0000062.png"\; state="\{\{state\}\}">J</figure-callout>}}_{\max }{t}_{}^{}{}_3^2-V_j+V_i)/A_{\max }---\left(13\right)$

The required total displacement S that slows down equals:

S＝S ₁+S ₂+S ₃ (16)

Shown in Fig. 7 (d), when there not being acceleration-A _MaxWhen sparing braking section, suppose that it is a that the phase one finishes the brief acceleration value _p, then above-mentioned formula should be rewritten as:

${\mathrm{<figure-callout\; id="1"\; label="t"\; filenames="H2009100125839E0000031.png,H2009100125839E0000041.png"\; state="\{\{state\}\}">t</figure-callout>}}_1=\frac{a_i-a_p}{J_{\max }}---\left(17\right)$

${\mathrm{<figure-callout\; id="2"\; label="S"\; filenames="H2009100125839E0000062.png"\; state="\{\{state\}\}">S</figure-callout>}}_2=V_1{\mathrm{<figure-callout\; id="2"\; label="t"\; filenames="H2009100125839E0000062.png"\; state="\{\{state\}\}">t</figure-callout>}}_2+\frac{1}{2}{a}_{\mathrm{<figure-callout\; id="2"\; label="p\; t"\; filenames="H2009100125839E0000062.png"\; state="\{\{state\}\}">p</figure-callout>}}{t}_{}^{}{}_2^2+\frac{1}{6}{\mathrm{<figure-callout\; id="2"\; label="J\; max\; t"\; filenames="H2009100125839E0000062.png"\; state="\{\{state\}\}">J</figure-callout>}}_{\max }{t}_{}^{}{}_2^3---\left(18\right)$

${\mathrm{<figure-callout\; id="2"\; label="t"\; filenames="H2009100125839E0000062.png"\; state="\{\{state\}\}">t</figure-callout>}}_2=\frac{a_j-a_p}{J_{\max }}---\left(19\right)$

$a_p=\sqrt[\&PlusMinus;]{\frac{a_{\mathrm{<figure-callout\; id="2"\; label="i"\; filenames="H2009100125839E0000062.png"\; state="\{\{state\}\}">i</figure-callout>}}^2+a_j^2-2J_{\max }(V_j-V_i)}{2}}---\left(20\right)$

S＝S ₁+S ₂ (21)

After obtaining the required minimum process path of the speed that carries out the transition to all catastrophe points from the speed and the acceleration of current point and acceleration respectively, if find to exist current point to the residual paths length between any catastrophe point less than required deceleration distance, then proof need reduce speed now from the i cycle; Otherwise, according to the speed operation of step P1 planning.The speed well of will planning is at last issued the interpolation computing module, calculates the position of next interpolated point, issues servomechanism installation, the drive motor motion.

The inventive method is in conjunction with the advantage of pre-service and real time forward looking, adopt pre-service to add the method for prediction, with calculated amount greatly but do not repaiied and transfer the data influence to be placed in the pre-service to calculate, real time forward looking carries out accurate speed planning according to the data that pre-service calculates, and repaiies the requirement of transferring operation to satisfy real-time and real-time response simultaneously.The path information of each interpolated point of noting when real time forward looking is according to pre-service is simultaneously dynamically revised the residual paths length between current point and the catastrophe point, can effectively avoid the generation of cumulative errors, improves the precision of the deceleration point of asking.

Because SPL is segmentation, and the catastrophe point of curvature is present in segmentation link place mostly, for fear of owing to repair and transfer pre-service that operation causes Problem of Failure as a result, when pre-service, regard SPL as segmentation independently, and think that the initial velocity of each section is the maximal rate that a last segmentation last point error allows.When needing deceleration like this and exceeding lathe acceleration and deceleration ability, this point is noted as the velocity jump point; If need to quicken, then upwards quicken according to the actual acceleration and deceleration ability of lathe.The path of obtaining is so neither repaiied the accent operating influence, again closing to reality machining path length as much as possible.

As can be seen from the above, pretreated purpose is not to cook up actual rate curve, and required catastrophe point information of knowing and comparatively accurate path are convenient to carry out speed planning when just calculating real-time interpolation in real time forward looking.At each interpolation cycle of real time forward looking module, retrain the speed V that obtains current interpolation cycle according to machining precision and acceleration, acceleration _i, to guarantee the continuity of acceleration.

Suppose prediction k section SPL, think that then the terminal velocity of k section curve is 0.Judgement is from location point P _I+1And whether the residual paths length between all catastrophe points and the k section End of Curve satisfies required deceleration distance, needs i cycle to reduce speed now if the residual paths length that has any point-to-point transmission less than required deceleration distance, then proves; Otherwise the speed operation according to obtaining above enters next interpolation cycle.

Because path that pre-service is asked less than actual path length, though can guarantee can not occur the not enough problem of deceleration distance, may enter deceleration area too early.In order to reduce the negative effect of slowing down in advance and bringing to working (machining) efficiency, the accumulative total routing information of each interpolated point that the prediction stage preserves during according to pre-service calculates the residual paths of current point, can eliminate the cumulative errors of machining path.Like this in the actual problem and of just can in time finding man-hour to slow down too early that adds to its dynamic correction.

The test of the inventive method is at the three-axis numerical control milling machine, and representative workpiece test procedure finishes by processing.Equipment therefor adopts encoder feedback, forms closed-loop control system, drives AC servo motor.The major parameter of device is as follows:

Digital control system: CPU Pentium M-1.6GHz, RAM-512M, HD-40G, I/O-32/24, scrambler input-4, D/A output-4, demonstration-10.4 " Color Liquid Crystal Display; Servo and the motor of peace river ∑-2;

Feed rate F=24m/min; Peak acceleration A _Max=5000m/s ²Maximum acceleration J _Max=500m/s ³Interpolation cycle T=1ms; Profile errors E _Max=0.000001m.

The inventive method and implement device Evaluation on effect serve as the evaluation and test foundation to process curve shown in Figure 8.And adopt the inventive method and implement device, graph of errors as shown in Figure 9, the speed planning curve as shown in figure 10, accelerating curve and part enlarged drawing are as shown in figure 11.From above-mentioned processing effect figure, can see:

1. described spline interpolation method can satisfy the requirement of machining precision, has handled the velocity jump point preferably, has solved because the part point machining precision that deceleration distance causes inadequately exceeds the problem of permissible value;

2. promptly shown in Figure 12 as the part enlarged drawing of accelerating curve among Figure 11, described method adopts the method for eliminating cumulative errors to improve the deceleration point precision of asking, and when finding to enter deceleration area in advance, can constantly in time revise present speed;

3. the accelerating curve that described method obtains is continuous substantially, and rate curve is level and smooth.

Claims (7)

1. SPL real-time interpolation method is characterized in that may further comprise the steps:

SPL section pre-service: job sequence is carried out the pre-service of SPL section, obtain length of curve and catastrophe point information;

Real time forward looking: carry out speed planning according to above-mentioned length of curve and catastrophe point information, obtain process velocity;

Interpolation is calculated: calculate next point coordinate according to the process velocity that obtains, export Servocontrol device to.

2. by the described SPL real-time interpolation of claim 1 method, it is characterized in that: describedly job sequence is carried out the pre-service of SPL section may further comprise the steps:

Import job sequence, the initial velocity of current curves section is set;

According to error constraint, acceleration constraint and acceleration constraint planning present speed;

Is the present speed of judging planning a catastrophe point?

If catastrophe point then adds the catastrophe point array with this catastrophe point;

Obtain next interpolated point coordinate;

Judge whether the current curves section finishes;

As finishing, export result to the real-time interpolation module, and read in next section of job sequence;

Return the initial velocity step that the present procedure section is set.

3. by the described SPL real-time interpolation of claim 2 method, it is characterized in that: described real time forward looking may further comprise the steps:

The initial velocity of processing is set;

According to error constraint, acceleration constraint, acceleration constraint and be programmed into constraint speed to constraint of velocity condition calculating processing;

Ask down some positions according to constraint speed;

According to being programmed into to Velocity Updating catastrophe point array;

Whether the residual paths length under judging between some positions and all catastrophe points is all greater than required deceleration distance;

, then reduce speed now, and recomputate present speed for not as above-mentioned judged result from current point;

Export present speed to the interpolation calculation procedure, and go to according to error constraint, acceleration constraint, acceleration constraint and be programmed into constraint speed step to constraint of velocity condition calculating processing.

4. by the described SPL real-time interpolation of claim 3 method, it is characterized in that: whether the residual paths length under judging between some positions and all catastrophe points all may further comprise the steps greater than required deceleration distance:

From the catastrophe point array, take out catastrophe point successively;

The length of curve information calculations that obtains according to pre-service from some positions down to the distance of this catastrophe point;

Judge successively that according to following any acceleration and the acceleration of speed, catastrophe point and speed whether the residual paths length between some positions and catastrophe point is greater than required deceleration distance down.

5. by the described SPL real-time interpolation of claim 3 method, it is characterized in that: if the residual paths length between some positions and all catastrophe points is all greater than required deceleration distance, then continuing exports present speed to the interpolation calculation procedure, and goes to according to error constraint, acceleration constraint, acceleration constraint and be programmed into constraint speed step to constraint of velocity condition calculating processing.

6. by the described SPL real-time interpolation of claim 2 method, it is characterized in that:, then go to according to error constraint, acceleration constraint and acceleration constraint planning present speed step if the current curves section does not finish.

7. by the described SPL real-time interpolation of claim 2 method, it is characterized in that:, then directly enter and obtain next interpolated point coordinate step if not catastrophe point.

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