CN1364675A - Predicting and compensating control method and device for boring size error - Google Patents

Abstract

The bording size error predicting and compensating control method includes successive measurement of the bore size Yi of T+1 machined workpieces; calculating the estimated size valve D(n) of the n-th workpiece to be matchined; calculating the weighted average value Z(n) of the sizes Y0, Y1, Y2,..., Yt; controlling the destination based on the reference size; and regulating the cutter based on the estimated size D(n). The corresponding device includes automatic measurement unit, control unit, and compensation boring head, and the compensation boring head includes mainly elastic boring bar, main shaft, push rod, main motor, compensating driving motor, screw bolt-screw nut pair and guide rod.

Description

Key is cut scale error predictive compensation control method and device thereof

Technical field

The invention belongs to the boring processing technique field, specifically, it relates to a kind of boring size error predictive compensation control method and device thereof.

Background technology

In bore hole processing, especially on automatic assembly line, carry out large quantities of a large amount of bore holes and add man-hour, because tool wear and adjustment, lathe wearing and tearing and other process conditions variation etc. are determined or the existence of uncertain factor, greatly influenced quality, efficient and the reliability of bore hole processing.Two key issues that right boring hole dimension error auto compensatng unit need solve comprise: error prediction method and compensation boring unit head (being called for short the compensation boring head), the former has determined the model and the control strategy thereof of error prediction, and the latter then is the executing agency of Tool in Cutting and compensating motion.

About the error prediction control method, sun contains and professor utilizes Wiener filtering that the scale error forecasting problem has been done deep discussion (seeing " pre-test of metal cutting process ", " XI AN JIAOTONG UNIVERSITY Subject Index ", 1978.1), the cylindricalo grinding experiment shows that its accurate to dimension has improved 30%.And he makes the error prediction model more become to optimizing by introducing the optimum prediction theory on this working foundation.The internal grinding experiment shows that its machining accuracy has improved more than 50%, and not only systematic error almost all is compensated, and random error also partly is compensated.Afterwards, the Li Peigen professor has at first introduced Kalman filtering and (has seen " Automatic Dimension Control in Fine-Boring " in the scale error prediction of bore hole, " Huazhong Institute of Technology journal ", 1982.12,127:127～135), a distinguishing feature in this method is that error prediction only needs the metrical information of back, has reduced the workload in line computation widely.

Need to prove, above-mentioned experimental work is primarily aimed at grinding or turning processing, its one of the main reasons is only to need moving linearly as the grinding carriage of cutter compensation mechanism or lathe saddle, and need not do gyration, make compensating motion (the microfeed motion of grinding carriage or lathe saddle) realize easily.In addition, in above-mentioned error model, the parameter of model is a constant, but not variations per hour, and they and fabrication process condition are closely related, generally show as with the statistic of system of processing output observation (as the measured value of workpiece to be machined diameter) closely related.If especially process conditions are unstable or change, model but can not self adaptation and self-regulation, and this also becomes them and fail to obtain one of significant obstacle of using in engineering reality.

As the critical component in the boring size error predictive compensation control device-compensation boring head, its main compensation performance index has: the minimum amount of feeding (resolution ratio), repetitive positioning accuracy, linearity, maximum feed range.The domestic and international compensation arrangement of developing is various at present, and from producing the mode of microdisplacement, they can be divided into two big classes: the first kind is to utilize some special entities to produce microdisplacement, as centering type and inclined disc type.Second class is to utilize the strain of knife bar or cutter holder to produce microdisplacement, as the differential thread formula, and elasticity cutter holder formula.Comparatively speaking, the mechanical transfer link of first kind compensation way is more, exist the possibility of error just big, thereby the application in fine compensation is restricted.The knife bar strain divides the relative main-shaft axis of knife bar axis to tilt (as the differential thread formula) and two kinds of translations (as parallel-crank mechanism), and its outstanding feature is to be resilient connection between main shaft and the knife bar.The problem that this resilient connection produces is: for avoiding producing dynamic vibration in cutting, just must note improving its rigidity when connecting, thereby produce the just correspondingly increase of driving force of feed motion.In addition, because the former is more with respect to the latter's machine driving link, thereby aspect avoiding creeping and producing the least unit compensation rate, the latter has the better application prospect, but its strain is driven by the signal of telecommunication/pressure oil, makes its controllability and dynamic responding speed deficiency.The elasticity cutter holder generally is to adopt skewback to promote cutter holder to produce strain, thereby realizes the radial compensation of point of a knife.Owing to be the strain of cutter holder, therefore, not only compensated linear is better, and required driving force is much smaller with respect to the knife bar distortion, and this is good for the unnecessary distortion that reduces whole transmission link.From producing the mode of skewback axially-movable, can be divided into piezo-electric crystal and stepper motor---nut screw pair dual mode.For the former, its distortion is unidirectional, therefore can not produce the action of negative sense feeding and cutter relieving, and distortion linearity Ben Shen is relatively poor in addition, thereby its application is restricted.And the latter can not only overcome the former above-mentioned defective, but also has fine control performance, thereby obtained in practice to use widely, but owing to be subjected to the restriction of elasticity cutter holder design space, when less or processing object was coaxial shoulder hole when the aperture of processing object, its application was restricted.Another should be noted that problem is, when needs time processing coaxial aperture, then needs the translation distortion of knife bar.Comprehensive, the subject matter that the research and development of existing compensation boring head exist is:

One precision index deficiency has restricted The Research of Relevant Technology and development.With regard to the technical merit of present this type of device, owing to be subjected to the restriction of principle and method, the microfeed precision of boring cutter can only reach micron order, and the driving mechanism of micro-deformation exists gap and strain inevitably, can not realize replacing the micron order microfeed of positive negative direction (unidirectional continuously even), make this type of device only be useful for the interruption feeding, as behind scale error compensation aspect-part of processing of boring under non-cutting state toolsetting, and can not be used for the continuous feed of working angles--boring two-axle interlocking (the microfeed motion of cutter and the feed motion of boring head) is processed, as the compensation of boring form error and the processing of irregularly-shaped hole, consider processing request (especially surface quality), the performance indications of some microfeed will exceed an order of magnitude at least, should reach submicron order as minimum compensation rate, and the dynamic response that corresponding driving is arranged, in addition, the unbalance dynamic problem of the cutting system that is caused by tool feeding also should cause enough attention.

Its two reliability is not high, has hindered the extensive employing in engineering reality.This type of device application in China's engineering reality is mainly aspect the compensation of scale error at present, and all be the technology of introducing basically, the fault rate height is a universal phenomenon, traces it to its cause, and the pollution of mechanically operated wearing and tearing and industry spot is its one of the main reasons.

Summary of the invention

The object of the present invention is to provide and be to provide a kind of boring aperture size error prediction compensating control method, this control method can be processed aperture size to boring and be predicted estimation, and has good adaptive and self-regulation, the present invention also provides its implement device, compensation boring head in this device has overcome the defective of prior art, has higher precision and reliability.

In order to realize the foregoing invention purpose, a kind of boring size error predictive compensation control method comprises the steps: that successively (1) measure the aperture size Y of T+1 finished work successively _i(i=0,1,2 ..., T); (2) the size estimation D (n) of calculating n workpiece to be processed (i.e. T+n+1 workpiece) thereafter, n=1,2,3,

Calculate finished work size Y ₀, Y ₁, Y ₂..., Y _TWeighted average Z _(n), as size estimation D (n) to T+n+1 workpiece, i.e. D (n)=Z _(n) $Z\left(n\right)=\underset{i=0}{\overset{T}{\mathrm{\Σ}}}{Y}_i{H}_i---\left(1\right)$ $H_i=\frac{1}{1+T}+\frac{12(n+\frac{T}{2})(\frac{T}{2}-i)}{T(T+1)(T+2)},i=\mathrm{0,1}\mathrm{\ΛT}---\left(2\right)$ H in the formula _iBe weight coefficient; (3),, cutter is adjusted according to above-mentioned size estimation D (n) with reference to the size Control desired value;

When n=1, step 2 is for replacing with: (2.1) calculate initial toolsetting meansquaredeviation respectively to the analysis that takes statistics of boring process _A ², processing meansquaredeviation _j ², measure meansquaredeviation _N ², a workpiece of every processing cutter average abrasion amount Δ D, and set the dimension D of initial toolsetting ₀(being generally processing dimension control desired value); (2.2) the inside diameter measurement value of establishing current finished work is Y (k), and then the aperture size of next workpiece to be processed is estimated D=X (k+1|k), k=0, and 1 ..., the recursion computing formula is: $K\left(k\right)=\frac{P\left(k\right|k-1)}{P\left(k\right|k-1)+{\mathrm{\&sigma;}}_N^2}---\left(3\right)$ $P(k+1|k)=\frac{{\mathrm{\&sigma;}}_N^{2}P\left(k\right|k-1)}{{\mathrm{\&sigma;}}_{\mathrm{<figure-callout\; id="2"\; label="N"\; filenames="A0211553700132.png"\; state="\{\{state\}\}">N</figure-callout>}}^2+P\left(k\right|k-1)}+{\mathrm{\&sigma;}}_j^2---\left(4\right)$

X(k+1|k)＝X(k|k-1)-ΔD+K(k)(Y(k)-X(k|k-1))??(5)

K in the formula (k) is the optimum gain coefficient, and P (k/k-1) is a predicated error covariance number, and X (k+1/k) is that the primary condition of recursion computing formula is based on the predicted value of k finished work to next workpiece to be processed size: $P\left(0\right|0\_)={\mathrm{\&sigma;}}_A^2---\left(6\right)$

X(0|0_)＝D ₀????(7)

Realize the device of above-mentioned boring size error predictive compensation control method, comprise self-operated measuring unit, control system and compensation boring head, described self-operated measuring unit is used for the size of measuring workpieces, and link to each other with described control system, this control system links to each other with described compensation boring head, it is characterized in that: described compensation boring head mainly comprises elastic boring bar, main shaft, pull bar, main motor, the compensation drive motors, feed screw nut pair and guide post, main motor links to each other with main shaft by transmission device, elastic boring bar is fixedlyed connected with main shaft, the compensation drive motors links to each other with screw mandrel in the feed screw nut pair by shaft coupling, and gyration is converted to moving axially of nut, nut links to each other with nut sleeve, and fixedly connected with guide post and a set of cups by it, be provided with rolling bearing in a set of cups, be used for support mandrel, this mandrel links to each other with pull bar in the main shaft, and pull bar links to each other with pull bar in the elastic boring bar.

Operation principle of the present invention is: self-operated measuring unit is input to control system with work piece size (diameter value) information that collects, control system is predicted the scale error of workpiece to be processed automatically according to the size of being set up (diameter) error prediction model, and the compensation boring head that control has a toolsetting function automatically (compensation of cutter trace) adjusts automatically to cutter, thus the uniformity of assurance workpiece to be machined size and the efficient and the reliability of processing.The present invention compared with prior art has following advantage and good effect: the error prediction model has good precision of prediction, predetermined speed is fast, the compensation of cutter and repetitive positioning accuracy height, compensation range is big, good linearity, cutting data is big, but because the translation of knife bar overall radial, make and once to realize manyly, be applicable to the processing of coaxial shoulder hole the contour compensation of blade (toolsetting); The present invention and on-line automatic inside diameter measurement device are used, can form the automation boring system of processing of a full cut-off ring, not only can automatically eliminate of the influence of cutter normal wearing stage to crudy, and can reduce the random error of system of processing significantly, greatly improve quality, efficient and the reliability of bore hole processing on the automatic assembly line, and have on-line computer quality of assistance management function.Its key technical indexes is as shown in the table:

Index name	Technical indicator
		Minimum compensation rate	＜0.5um
Compensation range (diameter)	0.4mm
		The cutter repetitive positioning accuracy	1um
Linear	Excellent
		Cutting depth	0.5mm
Cutting speed	120-180mm/min

In a word, the present invention is by detecting automatically the processing dimension on-line error, by relevant control theory to process model building, online forecasting mismachining tolerance in view of the above, for the bore hole process provides additional input, thereby reach the purpose of scale error control, can significantly improve quality, efficient and the reliability of (on the automatic assembly line) bore hole processing.Be applicable to and on automatic assembly line, carry out automation bore hole (essence) processing, and have operation computer aided quality management function.

Description of drawings

Fig. 1 is the structural representation of boring size error predictive compensation control device of the present invention;

Fig. 2 is the structural representation of compensation boring head among Fig. 1.

Fig. 3 is a specific embodiment structural representation of elastic boring bar among Fig. 2;

Fig. 4 is the structural representation of a specific embodiment of elastic deformable body among Fig. 3.

The specific embodiment

The present invention is further detailed explanation below in conjunction with accompanying drawing.

As shown in Figure 1, apparatus of the present invention are made of the self-operated measuring unit 22 that links to each other successively, control system 25 and compensation boring head 24.

Self-operated measuring unit 22 is used for the size of measuring workpieces 23, and links to each other with control system 25.Self-operated measuring unit can adopt the existing self-operated measuring unit in this area to carry out, as gage outfit and measuring instrument.

Control system 25 can be made up of industrial computer, PLC and software module thereof, measures the aperture size Y of T+1 finished work successively when self-operated measuring unit 22 _i(i=0,1,2 ..., T) after,

Control system is calculated finished work size Y ₀, Y ₁, Y ₂..., Y _TWeighted average Z _(n), as size estimation D (n) to T+n+1 workpiece, i.e. D (n)=Z _(n), (n=1,2 ...) $Z\left(n\right)=\underset{i=0}{\overset{T}{\mathrm{\&Sigma;}}}{Y}_i{H}_i---\left(1\right)$ $H_i=\frac{1}{1+T}+\frac{12(n+\frac{T}{2})(\frac{T}{2}-i)}{T(T+1)(T+2)},i=\mathrm{0,1}\mathrm{\&Lambda;T}---\left(2\right)$ H in the formula _iBe weight coefficient;

When only needing the predicted value of the next workpiece to be processed aperture size of prediction, also can adopt following manner to carry out, that is:

At first, calculate initial toolsetting meansquaredeviation respectively to the analysis that takes statistics of boring process _A ², processing meansquaredeviation _j ², measure meansquaredeviation _N ², a workpiece of every processing cutter average abrasion amount Δ D, and set the dimension D of initial toolsetting ₀(being generally processing dimension control desired value);

Next inside diameter measurement value of establishing current finished work is Y (k), and then the aperture size of next workpiece to be processed is estimated D (1)=X (k+1|k), k=0, and 1 ..., the recursion computing formula is: $K\left(k\right)=\frac{P\left(k\right|k-1)}{P\left(k\right|k-1)+{\mathrm{\&sigma;}}_N^2}---\left(3\right)$ $P(k+1|k)=\frac{{\mathrm{\&sigma;}}_N^{2}P\left(k\right|k+1)}{{\mathrm{\&sigma;}}_{\mathrm{<figure-callout\; id="2"\; label="N"\; filenames="A0211553700132.png"\; state="\{\{state\}\}">N</figure-callout>}}^2+P\left(k\right|k-1)}+{\mathrm{\&sigma;}}_j^2---\left(4\right)$ X(k+1|k)＝X(k|k-1)-ΔD+K(k)(Y(k)-X(k|k-1))??(5)

K in the formula (k) is the optimum gain coefficient, and P (k/k-1) is a predicated error covariance number, and X (k+1/k) is that the primary condition of recursion computing formula is based on the predicted value of k finished work to next workpiece to be processed size:

Comprehensive above-mentioned various, as long as pre-determine Δ D, σ _A ², σ _j ², σ _N ², D ₀Just can make optimum one-step prediction, and produce compensating signal in view of the above bore size. $P\left(0\right|0\_)={\mathrm{\&sigma;}}_A^2---\left(6\right)$

X(0|0_)＝D ₀????(7)

Last mode can be predicted any workpiece after the current processing work.When pre-determining n, behind the T, H _iBe constant, be not subjected to tool abrasion, mismachining tolerance and influence of measurement error so the advantage of this model is the error prediction model.

Control system according to above-mentioned size estimation D (n), utilizes 24 pairs of cutters of compensation boring head to adjust with reference to the size Control desired value.

Compensation boring head 24 is cores of the present invention, its structure as shown in Figure 2, mainly comprise elastic boring bar 1, main shaft 2, pull bar 5, main motor 8, compensation drive motors 13, feed screw nut pair 17,18 and guide post 16, main motor 8 links to each other with main shaft 2 by belt pulley transmission 7,21 (or other transmission device), drives main shaft 2 revolutions; Main shaft 2 is supported in the preceding casing 4 by bearing 3,6.Elastic boring bar 1 is fixedlyed connected with main shaft 2, and turns round with main shaft.Compensation drive motors 13 links to each other with screw mandrel 18 in the feed screw nut pair 17,18 by shaft coupling 14, wherein screw mandrel 18 is supported in the rear box 12 by bearing 15, coaxial with main shaft 2, and gyration is converted to moving axially of nut 17, nut 17 links to each other with nut sleeve 19, and is fixed together by it and guide post 16 and a set of cups 10 and moves axially; Be provided with rolling bearing 11 in a set of cups 10, be used for support mandrel 20, make it both can move axially with nut 17, can self do gyration again, pull bar 5 in this mandrel and the main shaft is rigidly connected by pin 9, and turns round with main shaft, and can drive pull bar 5 simultaneously and move axially, pull bar in pull bar 5 and the elastic boring bar is rigidly connected, and drives cutter by the transmission link in the elastic boring bar and produces compensating movement.

Elastic boring bar in the above-mentioned compensation boring head can adopt existing elastic boring bar, but adopts the parallelogram elastic boring bar that provides in another innovation and creation of the inventor can produce better technique effect.

As shown in Figure 3, the knife bar that boring cutter is housed two parts that elastic boring bar can be divided into the body of rod and be attached thereto, the body of rod is made of elastic deformable body 25, coupling sleeve 26, push rod 22, pull bar 27 and steel ball 23.Elastic deformable body 25 is a cylinder, as shown in Figure 4, it before vertically be divided into back three section 32,41 and 40, first to the 3rd cannelure 29,31,35 is positioned on the A-A cross section in elastic deformable body stage casing, the the 4th to the 6th cannelure 36,39,43 is positioned on the B-B cross section parallel with the A-A cross section, elastic deformable body stage casing, and the thickness that forms 30,34,37,42, four thin-walleds of four thin-walleds that are parallel to each other can produce better technique effect between 0.5-15.0mm the time.Transverse groove 33 communicates with the second and the 5th cannelure 31,39.When transverse groove 33 is vertical with the 5th cannelure 31,39 with second, and when the stage casing of elastic deformable body 25 is divided into laterally zygomorphic two parts, can realize better technique effect.

As can be seen from Figure 4, four the line of thin-walled 30,34,37,42 on same cross section constituted parallelogram.

Coupling sleeve 26 also is a cylinder, and be positioned at strain .25, the leading portion of elastic deformable body and stage casing and coupling sleeve external cylindrical surface have the gap about 1mm, and there is certain space that moves radially in the leading portion and the stage casing that are beneficial to elastic deformable body, and its back segment is fixedly connected with it.

Pull bar 27 is positioned at coupling sleeve 26 and coaxial with it, and like this, pull bar can move axially in the central through hole of coupling sleeve.Pull bar is provided with the inclined-plane;

Push rod 22 is positioned at the top, inclined-plane of pull bar 27, its axial line and thin-walled 30,34,37,42 are perpendicular, fixedly connected with the leading portion of elastic deformable body 25 in the upper end of push rod 22, concrete mode can be that push rod one end is threaded, and be connected, and by locking nut locking and guarantee certain pretightning force with screwed hole on the elastic deformable body leading portion.The axis of this screwed hole is vertical with four book walls that are parallel to each other on the elastic deformable body, the end of the other end of push rod is provided with centre bore, and steel ball is packed in the centre bore, and is pressed on the inclined-plane of pull bar, the contact-making surface on it and inclined-plane is the plane, can guarantee that both are doing not damage contact-making surface when mobile.

Fixedly connected with the leading portion of elastic deformable body 25 in the end of knife bar 24, concrete mode can adopt location, the face of cylinder, and by screw in compression.

Coupling sleeve 26 is located with adopting the short cylindrical conical surface being connected of boring head main shaft, compresses by the screw end face.

Straight end-face key all can be established in the end face cooperation place of above-mentioned boring head main shaft and coupling sleeve, coupling sleeve and elastic deformable body, elastic deformable body and knife bar, to transmit moment of torsion.

The above-mentioned body of rod is with cover plate 44 and protective cover 28 outward, and cover plate and protective cover play sealing and protective action, enter boring bar body inside with the foreign material that prevent industry spot.

Claims (4)

1. boring size error predictive compensation control method comprises the steps: that successively (1) measure the aperture size Y of T+1 finished work successively _i(i=0,1,2 ..., T); (2) the size estimation D (n) of calculating n workpiece to be processed thereafter;

Calculate finished work size Y ₀, Y ₁, Y ₂..., Y _TWeighted average Z _(n), as size estimation D (n) to T+n+1 workpiece, (n=1,2,3 ...), i.e. D (n)=Z _(n) $Z\left(n\right)=\underset{i=0}{\overset{T}{\mathrm{\&Sigma;}}}{Y}_i{H}_i---\left(1\right)$ $H_i=\frac{1}{1+T}+\frac{12(n+\frac{T}{2})(\frac{T}{2}-i)}{T(T+1)(T+2)},i=\mathrm{0,1}\mathrm{\&Lambda;T}--\left(2\right)$ H in the formula _iBe weight coefficient; (3),, cutter is adjusted according to above-mentioned size estimation D (n) with reference to the size Control desired value;

2. a kind of boring size error predictive compensation control method according to claim 1 is characterized in that when n=1, step 2 is: (2.1) calculate initial toolsetting meansquaredeviation respectively to the analysis that takes statistics of boring process _A ², processing meansquaredeviation _j ², measure meansquaredeviation _N ², a workpiece of every processing cutter average abrasion amount Δ D, and set the dimension D of initial toolsetting ₀(2.2) the inside diameter measurement value of establishing current finished work is Y (k), and then the aperture size of next workpiece to be processed is estimated D (1)=X (k+1|k), k=0, and 1 ..., the recursion computing formula is: $K\left(k\right)=\frac{P\left(k\right|k-1)}{P\left(k\right|k-1)+{\mathrm{\&sigma;}}_N^2}---\left(3\right)$ $P(k+1|k)=\frac{{\mathrm{\&sigma;}}_N^{2}P\left(k\right|k-1)}{{\mathrm{\&sigma;}}_N^2+P\left(k\right|k-1)}+{\mathrm{\&sigma;}}_j^2---\left(4\right)$

X(k+1|k)＝X(k|k-1)-ΔD+K(k)(Y(k)-X(k|k-1))??(5)

K in the formula (k) is the optimum gain coefficient, and P (k|k-1) is a predicated error covariance number, and X (k+1/k) is that the primary condition of recursion computing formula is based on the predicted value of k finished work to next workpiece to be processed size: $P\left(0\right|0\_)={\mathrm{\&sigma;}}_A^2---\left(6\right)$ X(0|0_)＝D ₀????(7)

3. device of realizing claim 1 or 2 described boring size error predictive compensation control methods, comprise self-operated measuring unit, control system and compensation boring head, described self-operated measuring unit (22) is used for the size of measuring workpieces, and link to each other with described control system (25), this control system links to each other with described compensation boring head, it is characterized in that: described compensation boring head (24) mainly comprises elastic boring bar (1), main shaft (2), pull bar (5), main motor (8), compensation drive motors (13), feed screw nut pair (17,18) and guide post (16), main motor (8) links to each other with main shaft (2) by transmission device, elastic boring bar (1) is fixedlyed connected with main shaft (2), compensation drive motors (13) links to each other with screw mandrel (18) in the feed screw nut pair by shaft coupling (14), and gyration is converted to moving axially of nut (17), nut (17) links to each other with nut sleeve (19), and fixedly connected with guide post (16) and a set of cups (10) by it, be provided with rolling bearing (11) in a set of cups (10), be used for support mandrel (20), this mandrel (20) links to each other with pull bar (5) in the main shaft (2), and pull bar links to each other with pull bar in the elastic boring bar (1).

4. device according to claim 3 is characterized in that: described elastic boring bar is the parallelogram elastic boring bar.

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