CN106990171A - A kind of ultrasonic wave automatic testing method for considering clamping workpiece error correction - Google Patents

Abstract

The invention discloses a kind of ultrasonic wave automatic testing method for considering clamping workpiece error correction, in the case of there can be clamping error for workpiece, carry the amendment in ultrasonic probe progress C-scan detection path to realize the compensation of clamping error by industrial robot.Detailed process is：Changed with time rule by workpiece rotation process reclaimed water throw, identify the actual clamping error of workpiece, then the path changeover matrix that workpiece coordinate is tied to world coordinate system is calculated, scanning destination path of the workpiece under workpiece coordinate system is calculated into the motion path for obtaining popping one's head under world coordinate system by matrixing, you can the probe movement path after being corrected.

Description

A kind of ultrasonic wave automatic testing method for considering clamping workpiece error correction

Technical field

The present invention relates to a kind of ultrasonic wave automatic testing method for considering clamping workpiece error correction.

Background technology

Ultrasound detection is an important branch of field of non destructive testing, and digitize, automate, intelligentized robot surpass Sound detection technology can effectively solve the problem of many artificial detection bands are come, and widely used robot is had begun in the world and is carried out Detect work.

When carrying out ultrasonic scanning detection to revolving body workpieces, generally by turntable it will be driven to rotate after clamping workpiece, and Ultrasonic probe is carried using mechanical platform to move along workpiece bus, so as to complete the spiral scanning to workpiece.Detection process In, it is necessary to pop one's head in moment alignment pieces normal direction to ensure acoustic beam vertical incidence.Because scroll chuck has convenient mounting and clamping certainly The advantages of dynamic centering, generally using scroll chuck come clamping revolving body workpieces.And during actually detected, often due to detection The improper operation of personnel causes to clamp tension so that workpiece is tilted.Water logging ring is chronically at additionally, due to detection process intermediate station Border, causes scroll chuck to get rusty, and also results in the problem of clamping workpiece is tilted.Now, due to the deformity of workpiece in scanning process Rotate, ultrasonic signal quality can be had a strong impact on, cause C-scan imaging dislocation, or even the problem of missing inspection flase drop.

Patent document CN201120298053.8 discloses a kind of by rotating disk/scroll chuck clamping measured piece, five axle machines Tool hand clamps the detection means of ultrasonic probe.But ultrasonic probe receiving and transmitting signal is not during the mechanism adds robot movement Stability, reduces the sensitivity of detection and is difficult to the compensation of clamping workpiece error.

The content of the invention

The deficiency existed for the ultrasonic automatic detection prior art of revolving body workpieces, the purpose of the present invention aims to provide one kind It can realize to revolving body workpieces high accuracy, high efficiency, the ultrasonic automatic checkout system of all standing formula, and can be from probe movement road The influence that clamping heeling error is brought is compensated on footpath.

There is the technical problem that clamping error causes accuracy of detection to decline to solve workpiece, technical scheme is carried For a kind of Ultrasonic C-Scan course corrections method for considering clamping workpiece error, comprise the following steps：

Step 1, workpiece rotational model when there is clamping error is set up, workpiece under water is carried out with fixed ultrasonic probe Ultrasonic scanning, obtains the underwater sound away from the rule that changes with time, by analyze the underwater sound away from situation of change, recognize the reality of workpiece Clamping error；

Step 2：World coordinate system, holder coordinate sys and workpiece coordinate system are set up, and derives probe, fixture and workpiece right The movement locus under coordinate system is answered, the kinematics model of clamping error correction is set up；

Step 3：According to the kinematics model of clamping error correction, the path change that workpiece coordinate is tied to world coordinate system is calculated Matrix is changed, finally calculates to obtain popping one's head in by matrixing by scanning destination path of the workpiece under workpiece coordinate system and is sat in the world Motion path under mark system.

In a kind of Ultrasonic C-Scan course corrections method of described consideration clamping workpiece error, described step 1, workpiece Actual load folder error calculated by following steps：

Workpiece rotational model when setting up clamping error, expression formula is formula 1：

Wherein, projection line and X-axis angle of the initial position central shaft in XOY faces are α₀, r,Characterize the influence of eccentric error The offset in the lower cylinder bottom surface center of circle and eccentric initial phase angle, workpiece centre axle are that clamping inclination angle is θ with Z axis angle, in clamping Under the influence of error, workpiece cross section is in the ellipse that is projected as in XOY faces, and Ω is expressed as O_eP₀With the angle of transverse.

With ultrasonic probe towards a certain position and fixation on workpiece, the rotating disk of fixed workpiece is rotated, the workpiece position is obtained Put around a circle A ripple signals, the first moment point of A ripple signals is taken for emission time point, corresponding to the peak value of the echo in surface At the time of point n_FWFor time of reception point, then on the circumference the actual underwater sound of certain point away from can be calculated by following formula：

Wherein, Δ t represents beginning ripple to the transition time of workpiece surface echo, c_wThe velocity of sound is represented, workpiece is obtained using formula 2 On on the circumference that is scanned each point each correspond to the underwater sound away from l_w, draw the underwater sound away from time graph l_w- t, minimum is carried out with formula 1 Square law curve matching, you can obtain the clamping error of workpiece during initial position.

World coordinate system O in a kind of Ultrasonic C-Scan course corrections method of described consideration clamping workpiece error, step 3₁ Origin be located at whole system center immobilize, coordinate system O₁Origin is located at rotating disk claw center, Z₁Axle for it is vertical to On direction, Y₁Axle is the direction that center probe axle is pointed to probe by Z axis；

Holder coordinate sys O₂Origin be located at the center of clamping tool, initial position and coordinate system O₁Overlap, if clamping tool It is static, then coordinate system O₂With coordinate system O₁Overlap, if clamping tool rotates, coordinate system O₂With the rotation or flat of clamping tool Move and move；

Workpiece coordinate system O₃Origin be located at workpiece center, with coordinate system O₂Relative position immobilize, eccentric clamping When with coordinate system O₂Relative position be (Δ x, Δ y, 0), Δ x and Δ y are workpiece centre and coordinate system O₂Relative position.

In a kind of Ultrasonic C-Scan course corrections method of described consideration clamping workpiece error, described step 3, probe Motion path and direction change under world coordinate system are：

Wherein,Scanning pattern during clamping correct for workpiece；

The direction of probe during clamping correct for workpiece；

C (*)=cos (*), s (*)=sin (*), t are sweep time, θ, and ω is scroll chuck angular velocity of rotation, (Δ x, Δ y, Δ z) are workpiece centre and coordinate system O₂Relative position.

The technical effects of the invention are that, clamping workpiece error is gone out by ultrasound examination quantitative judge, according to invention Path planning and automatic correcting algorithm, realize and the path of clamping workpiece error are corrected, make detection of the ultrasonic probe on workpiece Path is carried out according to initial planning path, so as to realize all standing scanning to workpiece.On the other hand, by being rectified to path Just, make ultrasonic wave vertical incidence workpiece, improve the ultrasonic energy for entering inside workpiece, Flaw detectability is improved, to complexity The raising of the precision and efficiency of the ultrasonic automatic detection of type face workpiece is significant.

In order to illustrate more clearly about the embodiment of the present invention or technical scheme of the prior art, below will be to embodiment or existing There is the accompanying drawing used required in technology description to be briefly described, it should be apparent that, drawings in the following description are only this Some embodiments of invention, for those of ordinary skill in the art, on the premise of not paying creative work, can be with Other accompanying drawings are obtained according to these accompanying drawings.

Brief description of the drawings

Fig. 1 is the structural representation of detecting system of the present invention；

Fig. 2 is signal generation/receiver of the present invention, the synchronous external trigger principle schematic of Data Acquisition Card；

Fig. 3 is clamping workpiece error schematic diagram of the present invention；

Fig. 4 is horizontal cross-section when workpiece has clamping error；

Fig. 5 is the motion conditions schematic diagram after present invention probe correction, and blue arrow is the direction of probe, and wherein a is just View, b is side view, and c is top view, and d is isometric view.

Embodiment

The present invention is described in further detail with reference to the accompanying drawings and examples.Following examples are used to illustrate this hair It is bright, but can not be used for limiting the scope of the present invention.

The hardware unit that the present embodiment is used includes 6DOF industrial robot, robot controller, tank, water circulation System, independent rotating disk, DC servo motor, driver, ultrasonic probe, signal generation/receiver, industrial computer (contain motion control Card, high-speed data acquisition card) and supporting cable etc..During detection, workplace vertical is placed on bottom of gullet and driven by servomotor Rotating disk on, and with scroll chuck feel relieved clamp, rotating disk by specific rotation speeds rotation.Meanwhile, visited by industrial robot clamping ultrasound Head along magnesium alloy shell case bus path uniform motion, during be always ensured that probe axis are vertical with surface of shell, and adopt in real time Collect ultrasonic signal, so as to complete the detection of the spiral scan to magnesium alloy shell case.

The communication modes of robot and industrial computer use the Socket sockets technologies of ICP/IP protocol, by by robot Controller, industrial computer are set to server end, client, complete that request of data can be sent after communication by client, service termination Receive and handle request.So, it can both realize that upper electric, lower electricity, intended trajectory motion to robot arm etc. were automatically controlled, industry control Machine can also receive the data feedback of robotic end in real time.

The 5th generations DMC-1846PCI of U.S. GALIL bus motion control card selected by the system completes independent rotating disk The high speed of axle, high-precision motion control.The second encoder feedback interface that sports cards are provided can realize signal generator and data The synchronous external trigger of capture card, trigger theory is as shown in Figure 2.Spike generator is set to external trigger mode, by Motion control card exports the pulse signal based on turntable shaft DC servo motor encoder position, after being integrated by pulse shaper 2 tunnel synchronous forward square-wave pulses are exported, the external trigger source of generator, data collecting card is used as.So, detection can effectively be reduced During sampling delay.Compared to internal trigger pattern, it is ensured that in rotating disk high-speed rotation actual acquisition position with it is soft Part model is consistent, it is therefore prevented that the entanglement of scanning element position in imaging.The signal can freely set output by sports cards OC instructions Frequency, so as to realize freely setting for Scanning step in detection process.

When being corrected, the present invention comprises the following steps：

Step 1：Workpiece rotational model when foundation has clamping error, obtains the underwater sound away from the rule that changes with time, and solid Determine ultrasonic probe, gather workpiece original A ripples signal during rotating a circle, and then obtain the actual underwater sound away from by analyzing water The situation of change of throw, recognizes the actual clamping error of workpiece；

Step 2：Set up under world coordinate system, holder coordinate sys and workpiece coordinate system, derive probe, fixture and workpiece and exist Movement locus under its respective coordinates system, sets up the kinematics model of clamping error correction；

Step 3：According to the kinematics model of clamping error correction, the path change that workpiece coordinate is tied to world coordinate system is calculated Matrix is changed, finally calculates to obtain popping one's head in by matrixing by scanning destination path of the workpiece under workpiece coordinate system and is sat in the world Motion path under mark system.

The actual load folder of workpiece in a kind of Ultrasonic C-Scan course corrections method of described consideration clamping workpiece error, step 1 Error is calculated by following steps：

Using center of turntable as origin of coordinates O, as shown in figure 3, workpiece bottom center is (x during initial position₀,y₀), in workpiece Heart axle is θ (clamping inclination angle) with Z axis angle, and projection line and X-axis angle of the initial position central shaft in XOY faces are α₀, r, The offset in the cylinder bottom surface center of circle and eccentric initial phase angle under the influence of sign eccentric error.Under the influence of clamping error, workpiece Cross section is in the ellipse that is projected as in XOY faces, t₀The oval position shape of moment projection is as shown in figure 4, Ω is expressed as O_eP₀It is long with ellipse The angle of axle.

Initial time, elliptical center O_e(x₀,y₀) expression formula is：

Projecting oval initial position equation is：

Wherein, transverseEllipse short shaft b=R, R are the radius of revolving body workpieces to be scanned.Projection is ellipse Circle and the intersection point P of X-axis₀(x_p, 0), it can be obtained by formula (1) and formula (2)：

Wherein,

Projection ellipse and X-axis intersection point P₀(x_p, 0) abscissa change in real time, its expression formula can be obtained by formula (4) and formula (5) For：

The underwater sound is away from l_wWith x_PRelation be：

l_w=x_T-x_P(5)

x_TRepresent the location of ultrasonic probe center wafer.Formula (1) and formula (4) are substituted into formula (5), obtained,

Therefore, with ω angular speed at the uniform velocity rolling clamp, a ultrasonic signal often is gathered by Δ t, n group numbers are obtained According to Δ t=360/ (ω * n) then pops one's head in the underwater sound for arriving workpiece surface away from l according to ultrasonic signal data acquisition_w, draw l_w- t is bent Line, by l_w- t curves and l_w- t mathematic(al) representations carry out least square fitting, can try to achieve the variable θ of several sign clamping errors, α₀, r,

By r,z₁Projection elliptical center O can be tried to achieve_eCoordinate (x_e, y_e, z_e) be：

By θ, α₀, the direction vector n of workpiece centre axle can be tried to achieve：

N=(- sin (θ) sin (α₀),sin(θ)cos(α₀),cos(θ))^T (8)

It is by Oe and workpiece centre axle direction vector the n expression formulas that can try to achieve workpiece centre axle：

By formula (10) and O₁(Δ x, Δ y, eccentric error Δ x and Δ y are when Δ z) can try to achieve clamping workpiece initial position：

World coordinate system O in a kind of Ultrasonic C-Scan course corrections method of described consideration clamping workpiece error, step 2₁ Origin be located at whole system center immobilize, coordinate system O₁Origin is located at rotating disk claw center, Z₁Axle for it is vertical to On direction, Y₁Axle is the direction that center probe axle is pointed to probe by Z axis；

Holder coordinate sys O₂Origin be located at the center of clamping tool, initial position and coordinate system O₁Overlap, if clamping tool It is static, then coordinate system O₂With coordinate system O₁Overlap, if clamping tool rotates, coordinate system O₂With the rotation or flat of clamping tool Move and move；

Coordinate system O₃Origin be located at workpiece center, with coordinate system O₂Relative position immobilize, positioned at workpiece bottom The round center of circle, coordinate system O during correct clamping₃With coordinate system O₂It is completely superposed；Heeling error causes coordinate system O₃It is around coordinate system O₂ X₂Axle have rotated θ angles；Eccentric error causes coordinate system O₃With coordinate system O₂Relative position be (Δ x, Δ y, Δ z)^T。

Because rotating disk relative to world coordinate system is that with the rotation of ω angular speed, therefore holder coordinate sys are sat relative to the world Mark system is rotated with ω angular speed, and because workpiece has clamping error, therefore workpiece coordinate system is deposited relative to holder coordinate sys In offset, tilt quantity and initial phase, but be unchanged over time, when clamping error is not present in workpiece, workpiece Coordinate system is overlapped with holder coordinate sys.Based on these three coordinate systems, work as offset, when known to tilt quantity and initial phase, root According to deriving the motion path that can be compensated to clamping error and probe orientation.

Pop one's head in motion path under world coordinate system and probe orientation is：

Wherein,

This specific embodiment is secured the workpiece against in tank first so that cylindrical workpiece is scanned as an example, is sent out with ultrasonic pulse Life/receiver (also known as Ultrasound Instrument) excitation ultrasonic longitudinal wave probe, is held on ultrasonic longitudinal wave probe by probe holder and is made pottery based on history 7 free degree immersed ultrasonic test motion platforms of Bill's TX60L manipulators, are connected by the motion control card installed on computer Control circuit controls the motion of motion platform, the pose of adjustment ultrasonic longitudinal wave probe in the sink, and with the height on computer Fast data collecting card obtains and stores the raw ultrasound A ripple signals of Ultrasound Instrument output, illustrates this finally by contrast scans result The validity of invention.

The Ultrasonic C-Scan course corrections method of clamping workpiece error needs to define 3 ginsengs in the entirely scanning workpiece decorum Examine coordinate system, i.e. world coordinate system, holder coordinate sys, workpiece coordinate system represents the motion of probe respectively, the motion of fixture and The motion of workpiece.According to the motion conditions of actual chuck and clamping workpiece situation, calculate workpiece coordinate and be tied to world coordinates The path changeover matrix of system.

By scanning destination path (x, y, z) of the workpiece under workpiece coordinate system_P ^TCalculated by matrixing and obtain popping one's head in Motion path (x, y, z) under world coordinate system_T ^T。

(x,y,z,1)_P ^T=¹A₃·(x,y,z,1)_T ^T (1)

Wherein,ⁱA_jTransformation matrixs of the denotation coordination system j to coordinate system i.

Coordinate system is defined as follows：

(1) coordinate system O₁Origin be located at whole system center immobilize, coordinate system O in this example₁Origin is located at rotating disk Claw center, Z₁Axle is vertically upward direction, Y₁Axle is the direction that center probe axle is pointed to probe by Z axis；

(2) coordinate system O₂Origin be located at the center of clamping tool, initial position and coordinate system O₁Overlap, if clamping tool It is static, then coordinate system O₂With coordinate system O₁Overlap, if clamping tool rotates, coordinate system O₂With the rotation or flat of clamping tool Move and move, coordinate system O in this example₂Positioned at the center of rotating disk claw, rotated with ω angular speed, initial position and coordinate It is O₁Overlap；

(3) coordinate system O₃Origin be located at workpiece center, with coordinate system O₂Relative position immobilize, positioned at workpiece The center of circle of bottom surface circle, coordinate system O during correct clamping₃With coordinate system O₂It is completely superposed；Heeling error causes coordinate system O₃It is around coordinate It is O₂X₂Axle have rotated θ angles；Eccentric error causes coordinate system O₃With coordinate system O₂Relative position be (Δ x, Δ y, Δ z)^T。

By the definition of above coordinate system, it can obtain：

Because direction change is not influenceed by translation, only being rotated by rotating disk is influenceed, therefore

In formula, c (*)=cos (*), s (*)=sin (*), t is sweep time, and ω is scroll chuck angular velocity of rotation, (Δ X, Δ y, Δ z) are workpiece centre and coordinate system O₂Relative position, θ be clamping workpiece inclination angle.

Scanning destination path of the workpiece under workpiece coordinate system be：

Probe orientation of the workpiece under workpiece coordinate system be：

It can be obtained by formula (4) and formula (5), the motion path popped one's head under world coordinate system is：

The direction change under world coordinate system of popping one's head in is：

Following examples are tested from the mode that spiral is swept to tubular workpiece.

Scanning destination path of the workpiece under workpiece coordinate system be：

Scanning probe direction of the workpiece under workpiece coordinate system is：

In formula, R is workpiece bottom radius, l_wIt is to pop one's head in the underwater sound away from H is workpiece height, and v is probe on workpiece bus Sweep speed.

It can be obtained by formula (10) and formula (12), the motion path popped one's head under world coordinate system is：

It can be obtained by formula (11) and (13), the direction popped one's head under world coordinate system is：

Claims (4)

1. a kind of ultrasonic wave automatic testing method for considering clamping workpiece error correction, it is characterised in that comprise the following steps：

Step 1, workpiece rotational model when there is clamping error is set up, ultrasound is carried out to workpiece under water with fixed ultrasonic probe Ripple is scanned, and obtains the underwater sound away from the rule that changes with time, by analyze the underwater sound away from situation of change, recognize the actual clamping of workpiece Error；

Step 2：World coordinate system, holder coordinate sys and workpiece coordinate system are set up, and derives probe, fixture and workpiece and is sat in correspondence Movement locus under mark system, sets up the kinematics model of clamping error correction；

Step 3：According to the kinematics model of clamping error correction, the path changeover square that workpiece coordinate is tied to world coordinate system is calculated Battle array, scanning destination path of the workpiece under workpiece coordinate system is finally calculated obtain popping one's head in world coordinate system by matrixing Under motion path.

2. a kind of ultrasonic wave automatic testing method for considering clamping workpiece error correction according to claim 1, its feature It is, in described step 1, the actual load folder error of workpiece is calculated by following steps：

Workpiece rotational model when setting up clamping error, expression formula is formula 1：

Wherein, projection line and X-axis angle of the initial position central shaft in XOY faces are α₀, r,Characterize circle under the influence of eccentric error The offset in the cylinder bottom surface center of circle and eccentric initial phase angle, workpiece centre axle are that clamping inclination angle is θ with Z axis angle, in clamping error Under the influence of, workpiece cross section is in the ellipse that is projected as in XOY faces, and Ω is expressed as O_eP₀With the angle of transverse.

With ultrasonic probe towards a certain position and fixation on workpiece, the rotating disk of fixed workpiece is rotated, is obtained on the workpiece position Around a circle A ripple signals, the first moment point for taking A ripple signals is emission time point, corresponding to the peak value of the echo in surface when Punctum n_FWFor time of reception point, then on the circumference the actual underwater sound of certain point away from can be calculated by following formula：

Wherein, Δ t represents beginning ripple to the transition time of workpiece surface echo, c_wThe velocity of sound is represented, institute on workpiece is obtained using formula 2 Each point each corresponds to the underwater sound away from l on the circumference of scanning_w, draw the underwater sound away from time graph l_w- t, least square is carried out with formula 1 Method curve matching, you can obtain the clamping error of workpiece during initial position.

3. a kind of ultrasonic wave automatic testing method for considering clamping workpiece error correction according to claim 1, its feature It is, world coordinate system O in step 3₁Origin be located at whole system center immobilize, coordinate system O₁Origin is located at rotating disk Claw center, Z₁Axle is vertically upward direction, Y₁Axle is the direction that center probe axle is pointed to probe by Z axis；

Holder coordinate sys O₂Origin be located at the center of clamping tool, initial position and coordinate system O₁Overlap, if clamping tool is quiet Only, then coordinate system O₂With coordinate system O₁Overlap, if clamping tool rotates, coordinate system O₂With the rotation or translation of clamping tool And move；

Workpiece coordinate system O₃Origin be located at workpiece center, with coordinate system O₂Relative position immobilize, during eccentric clamping with Coordinate system O₂Relative position be (Δ x, Δ y, 0), Δ x and Δ y are workpiece centre and coordinate system O₂Relative position.

4. a kind of ultrasonic wave automatic testing method for considering clamping workpiece error correction according to claim 3, its feature It is, in described step 3, the motion path and direction change popped one's head under world coordinate system are：

${\left[\begin{array}{c}x\\ y\\ z\\ 1\end{array}\right]}_p=\left[\begin{array}{cc}{R_1}_3& {P_1}_3\\ 0& 1\end{array}\right]\·{\left[\begin{array}{c}{f}_x\left(t\right)\\ f_y\left(t\right)\\ f_z\left(t\right)\\ 1\end{array}\right]}_T$

${\left[\begin{array}{c}{p}_x\\ p_y\\ p_z\\ 1\end{array}\right]}_p=\left[\begin{array}{cc}{R_1}_3& 0\\ 0& 1\end{array}\right]\·{\left[\begin{array}{c}{f}_{p_x}\left(t\right)\\ f_{p_y}\left(t\right)\\ f_{p_z}\left(t\right)\\ 1\end{array}\right]}_T$

Wherein,Scanning pattern during clamping correct for workpiece；

The direction of probe during clamping correct for workpiece；

${R_1}_3=\left[\begin{array}{ccc}c\left(\mathrm{\ω}t\right)& -s\left(\mathrm{\ω}t\right)c\left(\mathrm{\θ}\right)& -s\left(\mathrm{\ω}t\right)s\left(\mathrm{\θ}\right)\\ s\left(\mathrm{\ω}t\right)& c\left(\mathrm{\ω}t\right)c\left(\mathrm{\θ}\right)& c\left(\mathrm{\ω}t\right)s\left(\mathrm{\θ}\right)\\ 0& -s\left(\mathrm{\θ}\right)& c\left(\mathrm{\θ}\right)\end{array}\right];$

${P_1}_3=\left[\begin{array}{c}c\left(\mathrm{\ω}t\right)\mathrm{\Δ}x-s\left(\mathrm{\ω}t\right)\mathrm{\Δ}y\\ s\left(\mathrm{\ω}t\right)\mathrm{\Δ}x+c\left(\mathrm{\ω}t\right)\mathrm{\Δ}y\\ \mathrm{\Δ}z\end{array}\right];$

C (*)=cos (*), s (*)=sin (*), t are sweep time, θ, and ω is scroll chuck angular velocity of rotation, (Δ x, Δ y, Δ z) is workpiece centre and coordinate system O₂Relative position.