CN103063213A - Calibration method of position relationship between welding robot and position changer - Google Patents

Abstract

The invention provides a calibration method of a position relationship between a welding robot and a position changer, which is characterized in that an oblique axis of the position changer is defined as a Z axis, and a rotating axis of the position changer is defined as a Y axis, an original point of a coordinate system is a crossing point O of a rotating axis line and a oblique axis line, and another axis which is vertical to the Z axis and conforms to right-hand rules is an X axis. The calibration method comprises the following steps of: enabling the position changer to respectively rotate to a plurality of positions around the rotating axis and the oblique axis through a robot controller, recording the position data of a TCP (Transport Control Protocol) point at the corresponding positions, establishing a spherical equation and fitting an optimal spherical surface based on a least square method to obtain the original point of the coordinate system of the position changer; and then enabling the TCP point to carry out multi-point marking in the two axial directions of the position changer by adopting a same method and further obtaining the direction vector of each coordinate axis based on a vector cross product method to realize the calibration of the position relationship. The calibration method has the benefit that in order to eliminate the effect of accidental factors, a distance deviation rate concept and a set point threshold value determination method are proposed, so that the calibration precision is improved.

Description

The scaling method of a kind of welding robot and positioner position orientation relation

Technical field

The present invention relates to laser bonding processing cutting field, the position orientation relation scaling method of especially a kind of laser melting coating robot and external shaft, specifically the position orientation relation scaling method between a kind of welding robot and the 2 axle positioners.

Background technology

Laser again manufacture process, is repaired and is improved part in conjunction with rapid laser-shaping technique and modern advanced manufacturing technique take laser melting coating as the recovery technique platform.Laser again manufacturing machine people is based on the height integrated system of laser technology and Robotics, and it has good processing flexibility with robot and laser instrument coupling.Therefore robot provides five or six programmable kinematic axiss, and its effective working space and admissible space are subject to the restriction of kinematical constraint, need to utilize the utility appliance such as positioner that redundant degree of freedom is provided, as shown in Figure 1.

Based on the laser remanufacturing system of robot, the demarcation of robot and positioner position orientation relation is the prerequisite of robot and the efficient coordinated movement of various economic factors of positioner, also is the practical key of off-line programming technique.The holy auspicious Master's thesis of Liu of Harbin Institute of Technology " arc welding robot off-line programing practical research " has proposed to record the TCP o'clock pose data five different positions based on 5 standardizations that revolve the positioner that inclines, and can realize demarcating by calculating.The method Simple fast, but be subject to the impact of accidentalia, stochastic error is larger, is difficult to satisfy the demand of high-precision laser cladding.Proposed the sphere fitting calibrating method based on least square method in the literary composition, robot has been demarcated with the position orientation relation that revolves the positioner that inclines.

By laser melting and coating technique important parts being carried out surface modification is to reduce cost, put forward high performance a kind of very important means, but some curve surface of workpiece are very complicated, accessory size is large, only rely on 6 degree of freedom of robot itself to be difficult to effectively finish the motion of this complexity, therefore its effective working space and admissible space are subject to the restriction of kinematical constraint, need to utilize the utility appliance such as positioner that redundant degree of freedom is provided.The demarcation of robot and positioner position orientation relation is the prerequisite of robot and the efficient coordinated movement of various economic factors of positioner, also is the practical key of off-line programming technique.

Summary of the invention

The object of the invention is to for the deficiencies in the prior art and defective, a kind of laser melting coating robot and the pose scaling method that revolves the diaxon positioner that inclines are provided, have higher precision, satisfy the practical application need of production of the off-line programing of high-precision laser cladding fully.

According to an aspect of the present invention, provide the scaling method of a kind of welding robot and positioner position orientation relation, comprise the steps:

Step 1: make positioner rotate to respectively a plurality of positions around turning axle and sloping shaft respectively by robot controller, record the TCP point in the pose data of correspondence position and set up spherical equation, based on the optimum sphere of least square fitting, thereby try to achieve the positioner coordinate origin;

Step 2: make positioner rotate to respectively a plurality of positions around turning axle and sloping shaft respectively by robot controller, allow the TCP point the turning axle of positioner axially and sloping shaft axially make polymarker, further try to achieve the direction vector of each coordinate axis based on the method for vector multiplication cross, thereby realize the position orientation relation demarcation.

Preferably, describedly further try to achieve the step of the direction vector of each coordinate axis based on the method for vector multiplication cross, be specially, allow first positioner be in the zero-bit of turning axle and sloping shaft, and the TCP point is overlapped with the positioner gauge point, record the TCP position of this moment; Then make positioner move to two new positions around turning axle, the TCP point is overlapped with gauge point, record the position of TCP this moment; Then keep the position of current turning axle motionless, allow positioner rotate to two different positions around sloping shaft, and the TCP of robot point is overlapped with gauge point, record the position data of TCP this moment; Then obtain normal vector perpendicular to this plane based on two different vector multiplication cross on the same plane, try to achieve respectively the direction vector of positioner coordinate axis.

Preferably, when asking for the direction vector of coordinate axis, if taken point is larger to distance value and the expectation value difference of coordinate origin, then again get a little; Wherein, the method that adopts is the method for error threshold, when the difference of actual value and expectation value divided by expectation value during greater than the threshold value set, then again get a little, this advances the method can effectively reduce stochastic error, avoids the impact of accidentalia, has higher stated accuracy.

Preferably, described step 1 specifically comprises the steps:

Step 1.1: at first do a gauge point at the positioner chuck, as positioner sloping shaft J ₂When being in 0 ° ,-40 ° ,-30 ° ,-20 ° ,-10 °, 10 °, 20 °, 30 °, 40 °, 50 °, 60 °, execution in step: the positioner coordination function is set, and positioner is active set, artificial driven group of machine; Teaching robot TCP point overlaps with gauge point, enables the displacement coordination function, makes positioner around turning axle J ₁Rotation, the TCP point can remain with gauge point and overlap in the process of motion; Positioner turns to 20 positions at random, records the pose data that corresponding TCP is ordered;

Step 1.2: with the TCP point pose data preparation that gathers, set up the spherical surface error equation, quadratic sum minimum principle based on the least square method error, thereby set up system of linear equations and try to achieve position and the spherical radius of the centre of sphere in basis coordinates system of robot, wherein, to be the positioner base be initial point to the described centre of sphere.

Preferably, described step 2 specifically comprises the steps:

Make first sloping shaft J ₂Be in zero-bit, positioner turning axle J ₁Rotate two angles, gauge point arrives respectively two different positions, and teaching robot TCP overlaps with gauge point; Allow turning axle J ₁Motionless, sloping shaft J ₂Two angles of verting respectively, gauge point arrives two different positions, and then teaching robot TCP point overlaps with gauge point, records the position data of gauge point in the robot coordinate system; Make multiplication cross according to two vectors on the same plane and can obtain direction vector perpendicular to this plane, further trying to achieve the positioner basis coordinates is each change in coordinate axis direction vector.

In preferred scheme, positioner is the positioner that inclines that revolves of 2 axles, one is the turning axle that rotates around horizontal direction, and one is the sloping shaft that rotates around vertical direction, and two axles are the external shaft of robot, be convenient to robot and positioner and carry out the coordinated movement of various economic factors by robot controller, set up positioner basis coordinates system, sloping shaft is Z axis, and turning axle is Y-axis, coordinate origin is the intersection point O of rotating shaft axis and sloping shaft axis, with Y-axis, Z axis is vertical and another axle of meeting the right-hand rule is X-axis.Take up an official post at the positioner chuck and to get a bit, no matter positioner tilts or rotates around turning axle around sloping shaft, and the distance that this point is ordered to positioner coordinate origin O remains constant.Namely this point is take initial point as the centre of sphere, to the distance of initial point be on the sphere of radius.Based on this rule, can be by a bit rotating respectively with positioner on the positioner chuck or tilting to a plurality of positions, record the TCP point in the pose data of correspondence position and set up spherical equation, adopt the optimum sphere of least square fitting, thereby try to achieve the positioner coordinate origin.Then adopt and use the same method, allow the TCP point axially make polymarker two of positioners, make multiplication cross according at grade two vectors and can obtain direction vector perpendicular to this plane, can further try to achieve the direction vector of each axle of coordinate system, thereby obtain positioner with respect to the module and carriage transformation matrix of basis coordinates system of robot, thereby realize the demarcation of positioner position orientation relation.Be to eliminate the impact of accidentalia, proposed range deviation rate concept and set and get a threshold determination method, further improved stated accuracy.

The present invention adopts multiple spot coordinate figure when a bit moving to diverse location with positioner on the chuck, thereby then try to achieve the positioner coordinate origin based on the optimum sphere of least square fitting, thereby realize that the position orientation relation of robot positioner demarcates and adopt vector multiplication cross to obtain the change in coordinate axis direction vector by the polymarker method, and when when asking direction vector to get, if taken point surpasses the deviation ratio threshold value of setting then need again get a little, further improved the accuracy of demarcating." three point method " of only getting three points or five points or " five-spot " stated accuracy with respect to routine have obviously improved a lot, after demarcating, the program of off-line programing does not need to revise or only needs correction seldom just can be directly used in production reality, be convenient to the practical application of off-line programing program, have larger practical value.

Description of drawings

By reading the detailed description of non-limiting example being done with reference to the following drawings, it is more obvious that other features, objects and advantages of the present invention will become:

Fig. 1 is the positioner Coordinate system definition;

Fig. 2 is positioner labeling process synoptic diagram;

Fig. 3 is the sphere method fitting result based on least square method.

Embodiment

The present invention is described in detail below in conjunction with specific embodiment.Following examples will help those skilled in the art further to understand the present invention, but not limit in any form the present invention.Should be pointed out that to those skilled in the art, without departing from the inventive concept of the premise, can also make some distortion and improvement.These all belong to protection scope of the present invention.

(1) first step, fit sphere method are asked coordinate origin

As shown in Figure 1, the sloping shaft that the present invention defines positioner basis coordinates system axially is Z-direction, and turning axle axially is Y direction, and with Y-axis, Z axis is vertical and another axle of meeting the right-hand rule is X-axis, true origin is the intersection point O of rotating shaft axis and sloping shaft axis.

If treating the fit sphere centre of sphere is O(A, B, C), radius is R.Take up an official post at the positioner chuck and to get 1 A, teaching robot TCP point overlaps with the A point, enables the displacement coordination function.The control positioner is around turning axle J ₁Rotation, the TCP point can remain with the A point and overlap in the process of motion.Positioner turns to 20 positions at random, the record pose data that this moment, TCP was ordered.

And then allow positioner sloping shaft J ₂Be in respectively-40 ° ,-30 ° ,-20 ° ,-10 °, 10 °, 20 °, 30 °, 40 °, 50 °, during 60 ° of equal angles, robot and the positioner coordinated movement of various economic factors, recorder people TCP is corresponding pose data when the positioner all angles.

If the data point set that gathers is P _i(X _i, Y _i, Z _i), 1≤i≤N treats that the fit sphere centre of sphere is O(A, B, C), radius is R, each point is D to the distance of the centre of sphere _i, then

$D_i=\sqrt{{(X_i-A)}^2+{(Y_i-B)}^2+{(Z_i-C)}^2}---\left(1\right)$

Suppose a=-2A, b=-2B, c=-2C, d=-R ²+ A ²+ B ²+ C ², then based on the least square fitting sphere, set up following error equation

$Q(a,b,c,d)=\underset{i=1}{\overset{i=N}{\mathrm{\Σ}}}{\mathrm{\δ}}_i^2=\underset{i=1}{\overset{i=N}{\mathrm{\Σ}}}{(D_i^2-R^2)}^2=\underset{i=1}{\overset{i=N}{\mathrm{\Σ}}}{(X_i^2+Y_i^2+Z_i^2-{2\mathrm{AX}}_i-{2\mathrm{BY}}_i-{2\mathrm{CZ}}_i+d)}^2---\left(2\right)$

Wherein, ${{\mathrm{\δ}}_i}^2={(D_i^2-R^2)}^2.$

By formula (2) as can be known, difference of two squares function Q (a, b, c, d) is greater than 0, so there is the minimal value more than or equal to 0 in this function, and maximum value be infinity.Q (a, b, c, d) is respectively to a, b, and c, d asks local derviation

Make partial derivative equal 0, with a, b, c sets up system of linear equations as known variables to be asked, and then can try to achieve the sphere centre coordinate O(A of sphere according to Cramer's rule, B, C) (being that the positioner basis coordinates is initial point) and spherical radius R.

Fig. 2 is for adopting the sphere fitting process to ask coordinate origin O(A, B, C based on least square method) and the result of spherical radius R test synoptic diagram.

(2) second step, polymarker method are asked the change in coordinate axis direction vector

Make positioner sloping shaft J ₂Be in zero-bit, turning axle J ₁Rotate two angles, gauge point is in-position A respectively ₁, A ₂, teaching robot TCP point overlaps with gauge point.Then turning axle J ₁Motionless, sloping shaft J ₂Two angles of verting respectively, gauge point in-position A ₃, A ₄, teaching TCP point overlaps with gauge point, the pose data of record gauge point in basis coordinates system of robot.Labeling process as shown in Figure 3.

By the definition of aforesaid positioner coordinate system, and the geometric relationship between the gauge point, as can be known A, A ₁, A ₂3 definite planes are axially vertical with turning axle, A ₂, A ₃, A ₄3 definite planes are axially vertical with sloping shaft.

Hence one can see that, and the Y direction unit vector of positioner basis coordinates system is

$j=\frac{\stackrel{\→}{A_1{A}_2}\×\stackrel{\→}{{\mathrm{AA}}_1}}{|\stackrel{\→}{A_1{A}_2}\×\stackrel{\→}{{\mathrm{AA}}_1}|}---\left(3\right)$

The Z-direction unit vector is

$k=\frac{\stackrel{\→}{A_2{A}_3}\×\stackrel{\→}{{A_{3}A}_4}}{|\stackrel{\→}{A_2{A}_3}\×\stackrel{\→}{A_3{A}_4}|}---\left(4\right)$

X-direction can be tried to achieve by orthogonality relation, and its unit vector is

$i=\stackrel{\→}{j}\×\stackrel{\→}{k}---\left(5\right)$

In conjunction with the coordinate origin of trying to achieve previously, thereby can obtain positioner basis coordinates system with respect to the module and carriage transformation matrix of basis coordinates system of robot

$T_P^R=\left[\begin{array}{cccc}{i}_x& i_y& i_z& A\\ j_x& j_y& j_z& B\\ k_x& k_y& k_z& C\\ 0& 0& 0& 1\end{array}\right]---\left(6\right)$

I (i in the formula _x, i _y, i _z) be x axle unit vector, j (j _x, j _y, j _z) be y axle unit vector, k (k _x, k _y, y _z) be z axle unit vector, O(A, B, C) be true origin.

The present invention gathers respectively a plurality of data points at two axles, thereby then try to achieve the positioner coordinate origin based on the optimum sphere of least square fitting, thereby then adopt the method for vector multiplication cross to obtain the position orientation relation demarcation that the change in coordinate axis direction vector is realized the robot positioner by the polymarker method, and when when asking direction vector to get, if taken point surpasses the deviation ratio threshold value of setting then need again get a little, further improved the accuracy of demarcating.Stated accuracy is high, is convenient to the practical application of off-line programing program, has larger practical value.

More than specific embodiments of the invention are described.It will be appreciated that the present invention is not limited to above-mentioned particular implementation, those skilled in the art can make various distortion or modification within the scope of the claims, and this does not affect flesh and blood of the present invention.

Claims (5)

1. the scaling method of a welding robot and positioner position orientation relation is characterized in that, comprises the steps:

Step 1: make positioner rotate to respectively a plurality of positions around turning axle and sloping shaft respectively by robot controller, record the TCP point in the pose data of correspondence position and set up spherical equation, based on the optimum sphere of least square fitting, thereby try to achieve the positioner coordinate origin;

Step 2: make positioner rotate to respectively a plurality of positions around turning axle and sloping shaft respectively by robot controller, allow the TCP point the turning axle of positioner axially and sloping shaft axially make polymarker, further try to achieve the direction vector of each coordinate axis based on the method for vector multiplication cross, thereby realize the position orientation relation demarcation.

2. the scaling method of welding robot according to claim 1 and positioner position orientation relation, it is characterized in that, described step of further trying to achieve the direction vector of each coordinate axis based on the method for vector multiplication cross, be specially, allow first positioner be in the zero-bit of turning axle and sloping shaft, and the TCP point is overlapped with the positioner gauge point, record the TCP position of this moment; Then make positioner move to two new positions around turning axle, the TCP point is overlapped with gauge point, record the position of TCP this moment; Then keep the position of current turning axle motionless, allow positioner rotate to two different positions around sloping shaft, and the TCP of robot point is overlapped with gauge point, record the position data of TCP this moment; Then obtain normal vector perpendicular to this plane based on two different vector multiplication cross on the same plane, try to achieve respectively the direction vector of positioner coordinate axis.

3. the scaling method of welding robot according to claim 2 and positioner position orientation relation is characterized in that, when asking for the direction vector of coordinate axis, if taken point is larger to distance value and the expectation value difference of coordinate origin, then again gets a little; Wherein, the method that adopts is the method for error threshold, when the difference of actual value and expectation value, is then got a little during greater than the threshold value set again divided by expectation value.

4. the scaling method of welding robot according to claim 1 and positioner position orientation relation is characterized in that, described step 1 specifically comprises the steps:

Step 1.1: at first do a gauge point at the positioner chuck, as positioner sloping shaft J ₂When being in 0 ° ,-40 ° ,-30 ° ,-20 ° ,-10 °, 10 °, 20 °, 30 °, 40 °, 50 °, 60 °, execution in step: the positioner coordination function is set, and positioner is active set, artificial driven group of machine; Teaching robot TCP point overlaps with gauge point, enables the displacement coordination function, makes positioner around turning axle J ₁Rotation, the TCP point can remain with gauge point and overlap in the process of motion; Positioner turns to 20 positions at random, records the pose data that corresponding TCP is ordered;

Step 1.2: with the TCP point pose data preparation that gathers, set up the spherical surface error equation, quadratic sum minimum principle based on the least square method error, thereby set up system of linear equations and try to achieve position and the spherical radius of the centre of sphere in basis coordinates system of robot, wherein, to be the positioner base be initial point to the described centre of sphere.

5. the scaling method of welding robot according to claim 1 and positioner position orientation relation is characterized in that, described step 2 specifically comprises the steps:

Make first sloping shaft J ₂Be in zero-bit, positioner turning axle J ₁Rotate two angles, gauge point arrives respectively two different positions, and teaching robot TCP overlaps with gauge point; Allow turning axle J ₁Motionless, sloping shaft J ₂Two angles of verting respectively, gauge point arrives two different positions, and then teaching robot TCP point overlaps with gauge point, records the position data of gauge point in the robot coordinate system; Make multiplication cross according to two vectors on the same plane and can obtain direction vector perpendicular to this plane, further trying to achieve the positioner basis coordinates is each change in coordinate axis direction vector.

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